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Sample records for magnetically actuated probes

  1. Magnetically Actuated Seal

    NASA Technical Reports Server (NTRS)

    Pinera, Alex

    2013-01-01

    This invention is a magnetically actuated seal in which either a single electromagnet, or multiple electromagnets, are used to control the seal's position. This system can either be an open/ close type of system or an actively controlled system.

  2. Probing the cell membrane by magnetic particle actuation and Euler angle tracking.

    PubMed

    Irmscher, Matthias; de Jong, Arthur M; Kress, Holger; Prins, Menno W J

    2012-02-08

    The mechanical properties of the cell membrane and the subjacent actin cortex are determinants of a variety of processes in immunity and cell division. The lipid bilayer itself and its connection to the actin cortex are anisotropic. An accurate description of the mechanical structure of the cell membrane and the involved dynamics therefore necessitates a measurement technique that can capture the inherent anisotropy of the system. Here, we combine magnetic particle actuation with rotational and translational particle tracking to simultaneously measure the mechanical stiffness of monocytic cells in three rotational and two translational directions. When using particles that bind via integrins to the cell membrane and the subjacent cortex, we measured an isotropic stiffness and a characteristic power-law dependence of the shear modulus on the applied frequency. When using particles functionalized with immunoglobulin G, we measured an anisotropic stiffness with a 10-fold-reduced value in one dimension. We suggest that the observed reduced stiffness in the plane of the cell membrane is caused by a local detachment of the lipid bilayer from the subjacent cytoskeletal cortex. We expect that our technique will enable new insights into the mechanical properties of the cell membrane that will help us to better understand membrane processes such as phagocytosis and blebbing.

  3. Remote Magnetic Actuation of Micrometric Probes for in situ 3D Mapping of Bacterial Biofilm Physical Properties

    PubMed Central

    Galy, Olivier; Zrelli, Kais; Latour-Lambert, Patricia; Kirwan, Lyndsey; Henry, Nelly

    2014-01-01

    Bacterial adhesion and growth on interfaces lead to the formation of three-dimensional heterogeneous structures so-called biofilms. The cells dwelling in these structures are held together by physical interactions mediated by a network of extracellular polymeric substances. Bacterial biofilms impact many human activities and the understanding of their properties is crucial for a better control of their development — maintenance or eradication — depending on their adverse or beneficial outcome. This paper describes a novel methodology aiming to measure in situ the local physical properties of the biofilm that had been, until now, examined only from a macroscopic and homogeneous material perspective. The experiment described here involves introducing magnetic particles into a growing biofilm to seed local probes that can be remotely actuated without disturbing the structural properties of the biofilm. Dedicated magnetic tweezers were developed to exert a defined force on each particle embedded in the biofilm. The setup is mounted on the stage of a microscope to enable the recording of time-lapse images of the particle-pulling period. The particle trajectories are then extracted from the pulling sequence and the local viscoelastic parameters are derived from each particle displacement curve, thereby providing the 3D-spatial distribution of the parameters. Gaining insights into the biofilm mechanical profile is essential from an engineer's point of view for biofilm control purposes but also from a fundamental perspective to clarify the relationship between the architectural properties and the specific biology of these structures. PMID:24837001

  4. Remote magnetic actuation of micrometric probes for in situ 3D mapping of bacterial biofilm physical properties.

    PubMed

    Galy, Olivier; Zrelli, Kais; Latour-Lambert, Patricia; Kirwan, Lyndsey; Henry, Nelly

    2014-05-02

    Bacterial adhesion and growth on interfaces lead to the formation of three-dimensional heterogeneous structures so-called biofilms. The cells dwelling in these structures are held together by physical interactions mediated by a network of extracellular polymeric substances. Bacterial biofilms impact many human activities and the understanding of their properties is crucial for a better control of their development - maintenance or eradication - depending on their adverse or beneficial outcome. This paper describes a novel methodology aiming to measure in situ the local physical properties of the biofilm that had been, until now, examined only from a macroscopic and homogeneous material perspective. The experiment described here involves introducing magnetic particles into a growing biofilm to seed local probes that can be remotely actuated without disturbing the structural properties of the biofilm. Dedicated magnetic tweezers were developed to exert a defined force on each particle embedded in the biofilm. The setup is mounted on the stage of a microscope to enable the recording of time-lapse images of the particle-pulling period. The particle trajectories are then extracted from the pulling sequence and the local viscoelastic parameters are derived from each particle displacement curve, thereby providing the 3D-spatial distribution of the parameters. Gaining insights into the biofilm mechanical profile is essential from an engineer's point of view for biofilm control purposes but also from a fundamental perspective to clarify the relationship between the architectural properties and the specific biology of these structures.

  5. Magnetic actuation of hair cells

    PubMed Central

    Rowland, David; Roongthumskul, Yuttana; Lee, Jae-Hyun; Cheon, Jinwoo; Bozovic, Dolores

    2011-01-01

    The bullfrog sacculus contains mechanically sensitive hair cells whose stereociliary bundles oscillate spontaneously when decoupled from the overlying membrane. Steady-state offsets on the resting position of a hair bundle can suppress or modulate this native motility. To probe the dynamics of spontaneous oscillation in the proximity of the critical point, we describe here a method for mechanical actuation that avoids loading the bundles or contributing to the viscous drag. Magnetite beads were attached to the tips of the stereocilia, and a magnetic probe was used to impose deflections. This technique allowed us to observe the transition from multi-mode to single-mode state in freely oscillating bundles, as well as the crossover from the oscillatory to the quiescent state. PMID:22163368

  6. Impedance analysis of the organ of corti with magnetically actuated probes.

    PubMed

    Scherer, Marc P; Gummer, Anthony W

    2004-08-01

    An innovative method is presented to measure the mechanical driving point impedance of biological structures up to at least 40 kHz. The technique employs an atomic force cantilever with a ferromagnetic coating and an external magnetic field to apply a calibrated force to the cantilever. Measurement of the resulting cantilever velocity using a laser Doppler vibrometer yields the impedance. A key feature of the method is that it permits measurements for biological tissue in physiological solutions. The method was applied to measure the point impedance of the organ of Corti in situ, to elucidate the biophysical basis of cochlear amplification. The basilar membrane was mechanically clamped at its tympanic surface and the measurements conducted at different radial positions on the reticular lamina. The tectorial membrane was removed. The impedance was described by a generalized Voigt-Kelvin viscoelastic model, in which the stiffness was real-valued and independent of frequency, but the viscosity was complex-valued with positive real part, which was dependent on frequency and negative imaginary part, which was independent of frequency. There was no evidence for an inertial component. The magnitude of the impedance was greatest at the tunnel of Corti, and decreased monotonically in each of the radial directions. In the absence of inertia, the mechanical load on the outer hair cells causes their electromotile displacement responses to be reduced by only 10-fold over the entire range of auditory frequencies.

  7. Magnetically actuated metallic microgripper

    NASA Astrophysics Data System (ADS)

    Caraffini, Simone; Boyd, James G.

    1998-10-01

    The design and the fabrication of a magnetically actuated microgripper are described. The device is designed to have an out-of-plane motion; a novel concept among the microfabricated grippers. The gripper consists of three metallic fingers, radially directed and equally spaced on a circle; each finger composed by two beams, whose motion is driven by a magnetic field. The microgripper is modeled as an elastic system of two rectilinear beams, using Euler- Bernoulli theory for small deflections. The boundary value problem is solved and the deflection of the structure is calculated as a function of the magnetic force. The microgripper is fabricated using a UV-lithography based 3D electroforming technique. Each layer of the structure is made by metal electrodeposition into a polyimide mold. Several layers are stacked by repeated deposition and the final structure is obtained by dissolving the mold. Details about the fabrication techniques are presented and discussed. Properties and problems related to the photosensitive polyimide used (such as moisture absorption, loss of adhesion, etc.) are addressed. Electroforming of nickel, copper and permalloy are performed and optimized. In particular, a nickel activating solution is applied successfully for electroforming of microstructures. A shadow mask technique for seed-layer patterning is presented and discussed. A planar electromagnetic coil is fabricated by micromolding of thick photoresist and copper electroforming into the mold. The magnetic circuit is made by electrodeposition of permalloy.

  8. Single element magnetic suspension actuator

    NASA Technical Reports Server (NTRS)

    Groom, Nelson J. (Inventor)

    1991-01-01

    The invention, a single element magnetic suspension actuator with bidirectional force capability along a single axis, includes an electromagnet and a nonmagnetic suspended element. A permanent magnet mounted on the suspended element interacts with a magnetic field established by the electromagnet to produce bidirectional forces in response to a variable force command voltage V (sub FC) applied to the electromagnet. A sensor measures the position of the suspended element on the single axis which is a function of force command voltage V (sub FC).

  9. Magnetic Bead Actuation of Saccular Hair Cells

    NASA Astrophysics Data System (ADS)

    Rowland, David; Ramunno-Johnson, Damien; Lee, Jae-Hyun; Cheon, Jinwoo; Bozovic, Dolores

    2011-11-01

    When decoupled from the overlying membrane, hair bundles of the amphibian sacculus exhibit spontaneous oscillation. To explore the dynamics of this innate motility without an imposed external load, we recorded their oscillations with a high-speed CMOS camera, and applied mechanical manipulation that minimally alters the geometry of an individual hair bundle. We present a technique that utilizes micron-sized magnetic particles to actuate the stereociliary bundle with a magnetized probe. Quasi-steady-state displacements were imposed on freely oscillating bundles. Our data indicate that deflection of the bundle affects both the frequency and the amplitude of the oscillations, with a crossing of the bifurcation that is dependent on the direction and speed of the applied offset.

  10. Permanent magnet flux-biased magnetic actuator with flux feedback

    NASA Technical Reports Server (NTRS)

    Groom, Nelson J. (Inventor)

    1991-01-01

    The invention is a permanent magnet flux-biased magnetic actuator with flux feedback for adjustably suspending an element on a single axis. The magnetic actuator includes a pair of opposing electromagnets and provides bi-directional forces along the single axis to the suspended element. Permanent magnets in flux feedback loops from the opposing electromagnets establish a reference permanent magnet flux-bias to linearize the force characteristics of the electromagnets to extend the linear range of the actuator without the need for continuous bias currents in the electromagnets.

  11. Bio inspired Magnet-polymer (Magpol) actuators

    NASA Astrophysics Data System (ADS)

    Ahmed, Anansa S.; Ramanujan, R. V.

    2014-03-01

    Magnet filler-polymer matrix composites (Magpol) are an emerging class of morphing materials. Magpol composites have an interesting ability to undergo large strains in response to an external magnetic field. The potential to develop Magpol as large strain actuators is due to the ability to incorporate large particle loading into the composite and also due to the increased interaction area at the interface of the nanoparticles and the composite. Mn-Zn ferrite fillers with different saturation magnetizations (Ms) were synthesized. Magpol composites consisting of magnetic ferrite filler particles in an Poly ethylene vinyl acetate (EVA) matrix were prepared. The deformation characteristics of the actuator were determined. The morphing ability of the Magpol composite was studied under different magnetic fields and also with different filler loadings. All films exhibited large strain under the applied magnetic field. The maximum strain of the composite showed an exponential dependence on the Ms. The work output of Magpol was also calculated using the work loop method. Work densities of upto 1 kJ/m3 were obtained which can be compared to polypyrrole actuators, but with almost double the typical strain. Applications of Magpol can include artificial muscles, drug delivery, adaptive optics and self healing structures. Advantages of Magpol include remote contactless actuation, high actuation strain and strain rate and quick response.

  12. Methodology for artificial microswimming using magnetic actuation

    NASA Astrophysics Data System (ADS)

    Ghanbari, A.; Bahrami, M.; Nobari, M. R. H.

    2011-04-01

    We propose a methodology for swimming at low-Reynolds-number flows based on ciliary motion of a microswimmer using magnetic actuation of artificial cilia. By solving the coupled magnetic-elastic-hydrodynamic problem, we demonstrate nonreciprocal effective and recovery strokes for cilia that nicely mimic natural cilia beating. Cilia drag forces, microswimmer net displacement, velocity, and efficiency are calculated, and we show the model can swim using a prespecified magnetic actuation. The proposed methodology can be used for devising biomedical microdevices that swim in viscous flows inside the human body.

  13. Methodology for artificial microswimming using magnetic actuation.

    PubMed

    Ghanbari, A; Bahrami, M; Nobari, M R H

    2011-04-01

    We propose a methodology for swimming at low-Reynolds-number flows based on ciliary motion of a microswimmer using magnetic actuation of artificial cilia. By solving the coupled magnetic-elastic-hydrodynamic problem, we demonstrate nonreciprocal effective and recovery strokes for cilia that nicely mimic natural cilia beating. Cilia drag forces, microswimmer net displacement, velocity, and efficiency are calculated, and we show the model can swim using a prespecified magnetic actuation. The proposed methodology can be used for devising biomedical microdevices that swim in viscous flows inside the human body.

  14. Navigating conjugated polymer actuated neural probes in a brain phantom

    NASA Astrophysics Data System (ADS)

    Daneshvar, Eugene D.; Kipke, Daryl; Smela, Elisabeth

    2012-04-01

    Neural probe insertion methods have a direct impact on the longevity of the device in the brain. Initial tissue and vascular damage caused by the probe entering the brain triggers a chronic tissue response that is known to attenuate neural recordings and ultimately encapsulate the probes. Smaller devices have been found to evoke reduced inflammatory response. One way to record from undamaged neural networks may be to position the electrode sites away from the probe. To investigate this approach, we are developing probes with controllably movable electrode projections, which would move outside of the zone that is damaged by the insertion of the larger probe. The objective of this study was to test the capability of conjugated polymer bilayer actuators to actuate neural electrode projections from a probe shank into a transparent brain phantom. Parylene neural probe devices, having five electrode projections with actuating segments and with varying widths (50 - 250 μm) and lengths (200 - 1000 μm) were fabricated. The electroactive polymer polypyrrole (PPy) was used to bend or flatten the projections. The devices were inserted into the brain phantom using an electronic microdrive while simultaneously activating the actuators. Deflections were quantified based on video images. The electrode projections were successfully controlled to either remain flat or to actuate out-of-plane and into the brain phantom during insertion. The projection width had a significant effect on their ability to deflect within the phantom, with thinner probes deflecting but not the wider ones. Thus, small integrated conjugated polymer actuators may enable multiple neuro-experiments and applications not possible before.

  15. Elastomeric actuator devices for magnetic resonance imaging

    NASA Technical Reports Server (NTRS)

    Dubowsky, Steven (Inventor); Hafez, Moustapha (Inventor); Jolesz, Ferenc A. (Inventor); Kacher, Daniel F. (Inventor); Lichter, Matthew (Inventor); Weiss, Peter (Inventor); Wingert, Andreas (Inventor)

    2008-01-01

    The present invention is directed to devices and systems used in magnetic imaging environments that include an actuator device having an elastomeric dielectric film with at least two electrodes, and a frame attached to the actuator device. The frame can have a plurality of configurations including, such as, for example, at least two members that can be, but not limited to, curved beams, rods, plates, or parallel beams. These rigid members can be coupled to flexible members such as, for example, links wherein the frame provides an elastic restoring force. The frame preferably provides a linear actuation force characteristic over a displacement range. The linear actuation force characteristic is defined as .+-.20% and preferably 10% over a displacement range. The actuator further includes a passive element disposed between the flexible members to tune a stiffness characteristic of the actuator. The passive element can be a bi-stable element. The preferred embodiment actuator includes one or more layers of the elastomeric film integrated into the frame. The elastomeric film can be made of many elastomeric materials such as, for example, but not limited to, acrylic, silicone and latex.

  16. Magnetic suspension characteristics of electromagnetic actuators

    NASA Technical Reports Server (NTRS)

    Rao, Dantam K.; Dill, J.; Zorzi, E.

    1993-01-01

    Electromagnetic actuators that use a current-carrying coil (which is placed in a magnetic field) to generate mechanical force are conceptually attractive components for active control of rotating shafts. In one concept that is being tested in the laboratory, the control forces from such actuators are applied on the flexibly supported bearing housings of the rotor. Development of this concept into a practical reality requires a clear and thorough understanding of the role of electromechanical parameters of these actuators in delivering the right amount of control force at the right phase into the rotor. The electromechanical parameters of the actuators investigated are the mass of the armature, stiffness of its suspension, electrical resistance, and inductance of the coils. Improper selection of these parameters can result in degradation in their performance, leading to mistuning between the actuator and the rotor. Through a simple analysis, it is shown that use of such mistuned actuators could result in sharp fluctuations in the phase of the control force delivered into the rotor around the critical speeds. These sharp fluctuations in phase, called 'Phase Glitches', are undesirable. Hence, future designs of controllers should take into account the undesirable mistuning effects between the actuator and the rotor caused by the phase glitches.

  17. Magnetically actuated microvalve for active flow control

    NASA Astrophysics Data System (ADS)

    Olivier, Ducloux; Abdelkrim, Talbi; Yves, Deblock; Leticia, Gimeno; Nicolas, Tiercelin; Philippe, Pernod; Vladimir, Preobrazhensky; Alain, Merlen

    2006-04-01

    The reattachment of separated air flows can be actively controlled by blowing oscillatory air jets in the boundary layer, through submillimetric holes situated near the separation edge. To achieve such pulsed jets, a high flow rate, high actuation frequency microvalve was designed, fabricated and characterized. The microvalve is fed by a pressurized source of air, and its inner channel is alternatively pinched by a PDMS polymer membrane, modulating the air flow which is addressed towards the separated surface. Magnetostatic actuation was chosen for its high stress, high displacement, and remote actuation capabilities. The actuation consists in coupling an inductive driving coil and a NdFeB permanent magnet situated on the PDMS flexible membrane. Characterization of the resonance frequency, and vibration amplitude are achieved by interferometric means. The output flow is characterized using strioscopy visualization and hot wire anemometry methods. The design and fabrication process of the microsystem, and the results of these characterizations are presented in this paper.

  18. Optimization of a magnetic disk drive actuator with small skew actuation

    NASA Astrophysics Data System (ADS)

    He, Zhimin; Ong, Eng Hong; Guo, Guoxiao

    2002-05-01

    Currently the utilization of the voice-coil motor for actuating read/write head elements in magnetic hard disk drives results in a skewed actuation, which necessitates an involved microjogging process and thus a complicated servo system. Furthermore, in perpendicular recording systems, a small skew actuation will relax the requirement on pole trimming. This article presents a magnetic hard disk drive actuator and suspension assembly with small skew actuation. In the present study, the distance from the actuator pivot to the read/write head is chosen so that the skew angle variation is minimized. After that, the suspension head is assembled to the actuator arm at a slant angle with respect to the actuator longitudinal direction to achieve an absolute small skew actuation. Finite element modeling and experimental measurements reveal that there are no significant changes of the actuator assembly dynamic performance with and without the slant angle.

  19. Flux-Feedback Magnetic-Suspension Actuator

    NASA Technical Reports Server (NTRS)

    Groom, Nelson J.

    1990-01-01

    Flux-feedback magnetic-suspension actuator provides magnetic suspension and control forces having linear transfer characteristics between force command and force output over large range of gaps. Hall-effect devices used as sensors for electronic feedback circuit controlling currents flowing in electromagnetic windings to maintain flux linking suspended element at substantially constant value independent of changes in length of gap. Technique provides effective method for maintenance of constant flux density in gap and simpler than previous methods. Applications include magnetic actuators for control of shapes and figures of antennas and of precise segmented reflectors, magnetic suspensions in devices for storage of angular momentum and/or kinetic energy, and systems for control, pointing, and isolation of instruments.

  20. Electropermanent magnet actuation for droplet ferromicrofluidics

    PubMed Central

    Padovani, José I.; Jeffrey, Stefanie S.; Howe, Roger T.

    2016-01-01

    Droplet actuation is an essential mechanism for droplet-based microfluidic systems. On-demand electromagnetic actuation is used in a ferrofluid-based microfluidic system for water droplet displacement. Electropermanent magnets (EPMs) are used to induce 50 mT magnetic fields in a ferrofluid filled microchannel with gradients up to 6.4 × 104 kA/m2. Short 50 µs current pulses activate the electropermanent magnets and generate negative magnetophoretic forces that range from 10 to 70 nN on 40 to 80 µm water-in-ferrofluid droplets. Maximum droplet displacement velocities of up to 300 µm/s are obtained under flow and no-flow conditions. Electropermanent magnet-activated droplet sorting under continuous flow is demonstrated using a split-junction microfluidic design. PMID:27583301

  1. Probing Cell Deformability via Acoustically Actuated Bubbles

    PubMed Central

    Xie, Yuliang; Nama, Nitesh; Li, Peng; Mao, Zhangming; Huang, Po-Hsun; Zhao, Chenglong; Costanzo, Francesco; Huang, Tony Jun

    2016-01-01

    An acoustically actuated, bubble-based technique is developed to investigate the deformability of cells suspended in microfluidic devices. A microsized bubble is generated by an optothermal effect near the targeted cells, which are suspended in a microfluidic chamber. Subsequently, acoustic actuation is employed to create localized acoustic streaming. In turn, the streaming flow results in hydrodynamic forces that deform the cells in situ. The deformability of the cells is indicative of their mechanical properties. The method in this study measures mechanical biomarkers from multiple cells in a single experiment, and it can be conveniently integrated with other bioanalysis and drug-screening platforms. Using this technique, the mean deformability of tens of HeLa, HEK, and HUVEC cells is measured to distinguish their mechanical properties. HeLa cells are deformed upon treatment with Cytochalasin. The technique also reveals the deformability of each subpopulation in a mixed, heterogeneous cell sample by the use of both fluorescent markers and mechanical biomarkers. The technique in this study, apart from being relevant to cell biology, will also enable biophysical cellular diagnosis. PMID:26715211

  2. Magnetically Actuated Cilia for Microfluidic Manipulation

    NASA Astrophysics Data System (ADS)

    Hanasoge, Srinivas; Owen, Drew; Ballard, Matt; Hesketh, Peter J.; Alexeev, Alexander; Woodruff School of Mechanical Engineering Collaboration; Petit InstituteBioengineering; Biosciences Collaboration

    2015-11-01

    We demonstrate magnetic micro-cilia based microfluidic mixing and capture techniques. For this, we use a simple and easy to fabricate high aspect ratio cilia, which are actuated magnetically. These micro-features are fabricated by evaporating NiFe alloy at room temperature, on to patterned photoresist. The evaporated alloy curls upwards when the seed layer is removed to release the cilia, thus making a free standing `C' shaped magnetic microstructure. This is actuated using an external electromagnet or a rotating magnet. The artificial cilia can be actuated upto 20Hz. We demonstrate the active mixing these cilia can produce in the microchannel. Also, we demonstrate the capture of target species in a sample using these fast oscillating cilia. The surface of the cilia is functionalized by streptavidin which binds to biotin labelled fluorescent microspheres and mimic the capture of bacteria. We show very high capture efficiencies by using these methods. These simple to fabricate micro cilia can easily be incorporated into many microfluidic systems which require high mixing and capture efficiencies.

  3. Conjugated Polymer Actuators for Articulating Neural Probes and Electrode Interfaces

    NASA Astrophysics Data System (ADS)

    Daneshvar, Eugene Dariush

    This thesis investigated the potential use of polypyrrole (PPy) doped with dodecylbenzenesulfonate (DBS) to controllably articulate (bend or guide) flexible neural probes and electrodes. PPy(DBS) actuation performance was characterized in the ionic mixture and temperature found in the brain. Nearly all the ions in aCSF were exchanged into the PPy---the cations Na +, K+, Mg2+, Ca2+, as well as the anion PO43-; Cl- was not present. Nevertheless, deflections in aCSF were comparable to those in NaDBS and they were monotonic with oxidation level: strain increased upon reduction, with no reversal of motion despite the mixture of ionic charges and valences being exchanged. Actuation depended on temperature. Upon warming, the cyclic voltammograms showed additional peaks and an increase of 70% in the consumed charge. Actuation strain was monotonic under these conditions, demonstrating that conducting polymer actuators can indeed be used for neural interface and neural probe applications. In addition, a novel microelectro-mechanical system (MEMS) was developed to measure previously disregarded residual stress in a bilayer actuator. Residual stresses are a major concern for MEMS devices as that they can dramatically influence their yield and functionality. This device introduced a new technique to measure micro-scaled actuation forces that may be useful for characterization of other MEMS actuators. Finally, a functional movable parylene-based neural electrode prototype was developed. Employing PPy(DBS) actuators, electrode projections were successfully controlled to either remain flat or actuate out-of-plane and into a brain phantom during insertion. An electrode projection 800 microm long and 50 microm wide was able to deflect almost 800 microm away from the probe substrate. Applications that do not require insertion into tissue may also benefit from the electrode projections described here. Implantable neural interface devices are a critical component to a broad class of

  4. High bandwidth piezoresistive force probes with integrated thermal actuation

    PubMed Central

    Doll, Joseph C.; Pruitt, Beth L.

    2012-01-01

    We present high-speed force probes with on-chip actuation and sensing for the measurement of pN-scale forces at the microsecond time scale. We achieve a high resonant frequency in water (1–100 kHz) with requisite low spring constants (0.3–40 pN/nm) and low integrated force noise (1–100 pN) by targeting probe dimensions on the order of 300 nm thick, 1–2 μm wide and 30–200 μm long. Forces are measured using silicon piezoresistors while the probes are actuated thermally with an aluminum unimorph and silicon heater. The piezoresistive sensors are designed using open source numerical optimization code that incorporates constraints on operating temperature. Parylene passivation enables operation in ionic media and we demonstrate simultaneous actuation and sensing. The improved design and fabrication techniques that we describe enable a 10–20 fold improvement in force resolution or measurement bandwidth over prior piezoresistive cantilevers of comparable thickness. PMID:23175616

  5. Simultaneous magnetic actuation and observation with ferromagnetic sensors

    NASA Astrophysics Data System (ADS)

    Czajkowski, J.; Kinnunen, P.; Haapanen, K.; Niinimäki, J.; Fabritius, T.

    2016-02-01

    We present a novel, non-contact, and non-optical approach to actuation and sensing. In the developed method, both functions are based only on the alternating magnetic field and take place simultaneously. The article demonstrates the technique in one of its potential applications, i.e. rheometry. The developed device uses two orthogonal pairs of inductor coils to generate a rotating magnetic field. The field actuates a rotor with an embedded NdFeB ring magnet. The angular displacement is simultaneously monitored with an angular AMR sensor, placed underneath the rotor. The device is used to study aqueous solutions at different concentrations of glycerol (10-95%). The accuracy of the angular sensing is verified using machine vision and pattern recognition, which is a technique widely used in the existing viscometers. A new approach to viscosity probing and phase slipping detection is introduced. So far, in non-contact rotational viscometers the dynamic viscosity was related to a critical frequency, determined by altering the frequency of the rotating magnetic field. However, we propose to alter the magnitude of the field, by changing the current in the inductor coils. The frequency is kept constant and the viscosity is proportional to the amplitude of current, for which the phase slipping occurs. The applied rate of rotation can be optimized for a particular measurement scenario. The results suggest a great potential of the technique in a variety of scenarios. Simultaneous magnetic actuation and sensing enables application in a broad frequency band, from dc to tens of kilohertz. Moreover, the design of a measurement device is simplified, so that its cost can be significantly lower than that of a conventional system. Furthermore, presented method is non-contact, does not require a clear optical path, and could be less susceptible to the environmental conditions (e.g. poor illumination, or full immersion in the studied solution).

  6. Cardiac tissue engineering in magnetically actuated scaffolds

    NASA Astrophysics Data System (ADS)

    Sapir, Yulia; Polyak, Boris; Cohen, Smadar

    2014-01-01

    Cardiac tissue engineering offers new possibilities for the functional and structural restoration of damaged or lost heart tissue by applying cardiac patches created in vitro. Engineering such functional cardiac patches is a complex mission, involving material design on the nano- and microscale as well as the application of biological cues and stimulation patterns to promote cell survival and organization into a functional cardiac tissue. Herein, we present a novel strategy for creating a functional cardiac patch by combining the use of a macroporous alginate scaffold impregnated with magnetically responsive nanoparticles (MNPs) and the application of external magnetic stimulation. Neonatal rat cardiac cells seeded within the magnetically responsive scaffolds and stimulated by an alternating magnetic field of 5 Hz developed into matured myocardial tissue characterized by anisotropically organized striated cardiac fibers, which preserved its features for longer times than non-stimulated constructs. A greater activation of AKT phosphorylation in cardiac cell constructs after applying a short-term (20 min) external magnetic field indicated the efficacy of magnetic stimulation to actuate at a distance and provided a possible mechanism for its action. Our results point to a synergistic effect of magnetic field stimulation together with nanoparticulate features of the scaffold surface as providing the regenerating environment for cardiac cells driving their organization into functionally mature tissue.

  7. Magnetic Actuator Modelling for Rotating Machinery Analysis

    NASA Astrophysics Data System (ADS)

    Mendes, Ricardo Ugliara; de Castro, Hélio Fiori; Cavalca, Kátia Lucchesi; Ferreira, Luiz Otávio Saraiva

    Rotating machines have a wide range of application such as airplanes, factories, laboratories and power plants. Lately, with computer aid design, shafts finite element models including bearings, discs, seals and couplings have been developed, allowing the prediction of the machine behavior. In order to keep confidence during operation, it is necessary to monitor these systems, trying to predict future failures. One of the most applied technique for this purpose is the modal analysis. It consists of applying a perturbation force into the system and then to measure its response. However, there is a difficulty that brings limitations to the excitation of systems with rotating shafts when using impact hammers or shakers, once due to friction, undesired tangential forces and noise can be present in the measurements. Therefore, the study of a non-contact technique of external excitation becomes of high interest. In this sense, the present work deals with the study and development of a finite element model for rotating machines using a magnetic actuator as an external excitation source. This work also brings numerical simulations where the magnetic actuator was used to obtain the frequency response function of the rotating system.

  8. Magnetic actuation for MEMS scanners for retinal scanning displays

    NASA Astrophysics Data System (ADS)

    Yan, Jun; Luanava, Selso; Casasanta, Vincenzo

    2003-01-01

    We discuss magnetic actuation for Microvision"s bi-axial scanners for retinal scanning displays. Compared to the common side-magnet and moving-coil approach, we have designed, assembled and tested a novel magnet configuration, with magnets above and below the moving coil. This design reduces the magnet sizes significantly without sacrificing performance, and opens further improvement paths as well.

  9. Continuously tunable terahertz metamaterial employing magnetically actuated cantilevers.

    PubMed

    Ozbey, Burak; Aktas, Ozgur

    2011-03-28

    Terahertz metamaterial structures that employ flexing microelectromechanical cantilevers for tuning the resonance frequency of an electric split-ring resonator are presented. The tuning cantilevers are coated with a magnetic thin-film and are actuated by an external magnetic field. The use of cantilevers enables continuous tuning of the resonance frequency over a large frequency range. The use of an externally applied magnetic field for actuation simplifies the metamaterial structure and its use for sensor or filter applications. A structure for minimizing the actuating field is derived. The dependence of the tunable bandwidth on frequency is discussed.

  10. Development of Microfabricated Magnetic Actuators for Removing Cellular Occlusion.

    PubMed

    Lee, Selene A; Lee, Hyowon; Pinney, James R; Khialeeva, Elvira; Bergsneider, Marvin; Judy, Jack W

    2011-05-01

    Here we report on the development of torsional magnetic microactuators for displacing biological materials in implantable catheters. Static and dynamic behaviors of the devices were characterized in air and in fluid using optical experimental methods. The devices were capable of achieving large deflections (>60°) and had resonant frequencies that ranged from 70 Hz to 1.5 kHz in fluid. The effect of long-term actuation (>2.5 · 10(8) cycles) was quantified using resonant shift as the metric (Δf < 2%). Cell-clearing capabilities of the devices were evaluated by examining the effect of actuation on a layer of aggressively growing adherent cells. On average, actuated microdevices removed 37.4% of the adherent cell layer grown over the actuator surface. The effect of actuation time, deflection angle, and beam geometry were evaluated. The experimental results indicate that physical removal of adherent cells at the microscale is feasible using magnetic microactuation.

  11. Computational Modeling of Magnetically Actuated Propellant Orientation

    NASA Technical Reports Server (NTRS)

    Hochstein, John I.

    1996-01-01

    sufficient performance to support cryogenic propellant management tasks. In late 1992, NASA MSFC began a new investigation in this technology commencing with the design of the Magnetically-Actuated Propellant Orientation (MAPO) experiment. A mixture of ferrofluid and water is used to simulate the paramagnetic properties of LOX and the experiment is being flown on the KC-135 aircraft to provide a reduced gravity environment. The influence of a 0.4 Tesla ring magnet on flow into and out of a subscale Plexiglas tank is being recorded on video tape. The most efficient approach to evaluating the feasibility of MAPO is to compliment the experimental program with development of a computational tool to model the process of interest. The goal of the present research is to develop such a tool. Once confidence in its fidelity is established by comparison to data from the MAPO experiment, it can be used to assist in the design of future experiments and to study the parameter space of the process. Ultimately, it is hoped that the computational model can serve as a design tool for full-scale spacecraft applications.

  12. Spacecraft Attitude Tracking and Maneuver Using Combined Magnetic Actuators

    NASA Technical Reports Server (NTRS)

    Zhou, Zhiqiang

    2010-01-01

    The accuracy of spacecraft attitude control using magnetic actuators only is low and on the order of 0.4-5 degrees. The key reason is that the magnetic torque is two-dimensional and it is only in the plane perpendicular to the magnetic field vector. In this paper novel attitude control algorithms using the combination of magnetic actuators with Reaction Wheel Assembles (RWAs) or other types of actuators, such as thrusters, are presented. The combination of magnetic actuators with one or two RWAs aligned with different body axis expands the two-dimensional control torque to three-dimensional. The algorithms can guarantee the spacecraft attitude and rates to track the commanded attitude precisely. A design example is presented for Nadir pointing, pitch and yaw maneuvers. The results show that precise attitude tracking can be reached and the attitude control accuracy is comparable with RWAs based attitude control. The algorithms are also useful for the RWAs based attitude control. When there are only one or two workable RWAs due to RWA failures, the attitude control system can switch to the control algorithms for the combined magnetic actuators with the RWAs without going to the safe mode and the control accuracy can be maintained.

  13. Magnetically Assisted Bilayer Composites for Soft Bending Actuators

    PubMed Central

    Jang, Sung-Hwan; Na, Seon-Hong; Park, Yong-Lae

    2017-01-01

    This article presents a soft pneumatic bending actuator using a magnetically assisted bilayer composite composed of silicone polymer and ferromagnetic particles. Bilayer composites were fabricated by mixing ferromagnetic particles to a prepolymer state of silicone in a mold and asymmetrically distributed them by applying a strong non-uniform magnetic field to one side of the mold during the curing process. The biased magnetic field induces sedimentation of the ferromagnetic particles toward one side of the structure. The nonhomogeneous distribution of the particles induces bending of the structure when inflated, as a result of asymmetric stiffness of the composite. The bilayer composites were then characterized with a scanning electron microscopy and thermogravimetric analysis. The bending performance and the axial expansion of the actuator were discussed for manipulation applications in soft robotics and bioengineering. The magnetically assisted manufacturing process for the soft bending actuator is a promising technique for various applications in soft robotics. PMID:28773007

  14. Microseconds-scale magnetic actuators system for plasma feedback stabilization

    NASA Astrophysics Data System (ADS)

    Kogan, K.; Be'ery, I.; Seemann, O.

    2016-10-01

    Many magnetic confinement machines use active feedback stabilization with magnetic actuators. We present a novel magnetic actuators system with a response time much faster than previous ones, making it capable of coping with the fast plasma instabilities. The system achieved a response time of 3 μs with maximal current of 500 A in a coil with inductance of 5.2 μH. The system is based on commercial solid-state switches and FPGA state machine, making it easily scalable to higher currents or higher inductivity.

  15. Materials for efficient high-flux magnetic bearing actuators

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    Magnetic bearings have demonstrated the capability for achieving positioning accuracies at the nanometer level in precision motion control stages. This makes possible the positioning of a wafer in six degrees of freedom with the precision necessary for photolithography. To control the position of an object at the nanometer level, a model of the magnetic bearing actuator force-current-airgap relationship must be accurately obtained. Additionally, to reduce thermal effects the design of the actuator should be optimized to achieve maximum power efficiency and flux density. Optimization of the actuator is accomplished by proper pole face sizing and utilizing a magnetic core material which can be magnetized to the highest flux density with low magnetic loss properties. This paper describes the construction of a magnetic bearing calibration fixture designed for experimental measurement of the actuator force characteristics. The results of a material study that review the force properties of nickel-steel, silicon-steel, and cobalt-vanadium-iron, as they apply to magnetic bearing applications are also presented.

  16. Three-axis force actuator for a magnetic bearing

    NASA Technical Reports Server (NTRS)

    Gondhalekar, Vijay (Inventor)

    1998-01-01

    This invention features a three-axis force actuator that axially, radially and rotatably supports a bearing member for frictionless rotation about an axis of rotation generally coincident with a Z-axis. Also featured is a magnetic bearing having such an actuator. The actuator includes an inner member, a magnetic member and a pole assembly having a ring member and four pole extending therefrom. The poles are equi-angular spaced from each other and radially spaced about the Z-axis. The inner member extends along the Z-axis and is a highly magnetic permeable material. The magnetic member is formed about the inner member outer surface, extends along the Z-axis and is configured so one magnetic pole polarity is located at its outer surface and the other polarity pole is located at its inner surface. Preferably, the magnetic member is a radially magnetized permanent magnet. The inner surface of the ring member is magnetically coupled to the magnetic member and a face of each pole is coupled to the bearing member. The magnetic member, the pole assembly, the inner member and the bearing member cooperate to generate a magnetic field that radially and rotatably supports a rotating member secured to the bearing member. The actuator further includes a plurality of electromagnetic coils. Preferably, a coil is formed about each pole and at least 2 coils are formed about the inner member. When energized, the electromagnetic coils generate a modulated magnetic field that stabilizes the rotating member in the desired operational position.

  17. Magnetic TRAnsition Region Probe (MTRAP)

    NASA Technical Reports Server (NTRS)

    Moore, R. L.; Davis, John; Hathaway, David; Six, N. Frank (Technical Monitor)

    2002-01-01

    MTRAP (Magnetic Transition Region Probe) will reveal the fine-scale physical processes in the Sun's magnetic transition region, the complex layer from the upper photosphere to the upper chromosphere/lower transition region. In the magnetic transition region plasma forces and magnetic forces are of comparable strength, which results in complex interplay of the two, which interplay governs the coupling of the convectively-driven deeper layers to the magnetically-driven upper transition region and inner corona. The fine-scale magnetic structure, processes, and events in the magnetic transition region are key to the genesis of the Sun's entire hot, dynamic outer atmosphere and to the initiation of large eruptive events. MTRAP will be a single spacecraft in Sun-synchronous Earth orbit. Because MTRAP will probe and measure the 3-D structure and dynamics of the magnetic field and plasma in the chromosphere and transition region with unprecedented resolution, the required telescope size and telemetry rates dictate that MTRAP be in Earth orbit, not in deep space. The observations will feature visible and infrared maps of vector magnetic and velocity fields in the magnetic transition region and photosphere. These will have large field of view (greater than 100,000 km), high resolution (greater than 100 km), and high sensitivity (greater than 30 G in transverse field). These observations of the lower atmosphere will be complemented by UV maps of the structure, velocity, and magnetic field (including the full vector field if technically feasible) higher up, in the upper chromosphere and lower transition region. MTRAP will also have an EUV imaging spectrograph observing coronal structure and dynamics in the same field of view with comparable resolution. Specific phenomena to be analyzed include spicules, bright points, jets, the base of plumes, and the triggering of eruptive flares and coronal mass ejections. Additional information is included in the original extended abstract.

  18. Asymmetric actuating structure generates negligible influence on the supporting base for high performance scanning probe microscopies

    NASA Astrophysics Data System (ADS)

    Yi Yan, Gang; Bin Liu, Yong; Hua Feng, Zhi

    2014-02-01

    An asymmetric actuating structure generating negligible influence on the supporting base for high performance scanning probe microscopies is proposed in this paper. The actuator structure consists of two piezostacks, one is used for actuating while the other is for counterbalancing. In contrast with balanced structure, the two piezostacks are installed at the same side of the supporting base. The effectiveness of the structure is proved by some experiments with the actuators fixed to the free end of a cantilever. Experimental results show that almost all of the vibration modes of the cantilever are suppressed effectively at a wide frequency range of 90 Hz-10 kHz.

  19. Magnetic Gearing Versus Conventional Gearing in Actuators for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Puchhammer, Gregor

    2014-01-01

    Magnetic geared actuators (MGA) are designed to perform highly reliable, robust and precise motion on satellite platforms or aerospace vehicles. The design allows MGA to be used for various tasks in space applications. In contrast to conventional geared drives, the contact and lubrication free force transmitting elements lead to a considerable lifetime and range extension of drive systems. This paper describes the fundamentals of magnetic wobbling gears (MWG) and the deduced inherent characteristics, and compares conventional and magnetic gearing.

  20. Magnetic Actuation of Self-Assembled DNA Hinges

    NASA Astrophysics Data System (ADS)

    Lauback, S.; Mattioli, K.; Armstrong, M.; Miller, C.; Pease, C.; Castro, C.; Sooryakumar, R.

    DNA nanotechnology offers a broad range of applications spanning from the creation of nanoscale devices, motors and nanoparticle templates to the development of precise drug delivery systems. Central to advancing this technology is the ability to actuate or reconfigure structures in real time, which is currently achieved primarily by DNA strand displacement yielding slow actuation times (about 1-10min). Here we exploit superparamagnetic beads to magnetically actuate DNA structures which also provides a system to measure forces associated with molecular interactions. DNA nanodevices are folded using DNA origami, whereby a long single-stranded DNA is folded into a precise compact geometry using hundreds of short oligonucleotides. Our DNA nanodevice is a nanohinge from which rod shaped DNA nanostructures are polymerized into micron-scale filaments forming handles for actuation. By functionalizing one arm of the hinge and the filament ends, the hinge can be attached to a surface while still allowing an arm to rotate and the filaments can be labeled with magnetic beads enabling the hinge to be actuated almost instantaneously by external magnetic fields. These results lay the groundwork to establish real-time manipulation and direct force application of DNA constructs.

  1. Spacecraft Attitude Tracking and Maneuver Using Combined Magnetic Actuators

    NASA Technical Reports Server (NTRS)

    Zhou, Zhiqiang

    2012-01-01

    A paper describes attitude-control algorithms using the combination of magnetic actuators with reaction wheel assemblies (RWAs) or other types of actuators such as thrusters. The combination of magnetic actuators with one or two RWAs aligned with different body axis expands the two-dimensional control torque to three-dimensional. The algorithms can guarantee the spacecraft attitude and rates to track the commanded attitude precisely. A design example is presented for nadir-pointing, pitch, and yaw maneuvers. The results show that precise attitude tracking can be reached and the attitude- control accuracy is comparable with RWA-based attitude control. When there are only one or two workable RWAs due to RWA failures, the attitude-control system can switch to the control algorithms for the combined magnetic actuators with the RWAs without going to the safe mode, and the control accuracy can be maintained. The attitude-control algorithms of the combined actuators are derived, which can guarantee the spacecraft attitude and rates to track the commanded values precisely. Results show that precise attitude tracking can be reached, and the attitude-control accuracy is comparable with 3-axis wheel control.

  2. Low power valve actuation using trans-permanent magnetics

    NASA Astrophysics Data System (ADS)

    Duval, Luis Denit

    The subject of magnetic actuators is very broad, and encompasses a wide range of technologies, magnetic circuit topologies, and performance characteristics for an ever-increasing spectrum of applications. As a consequence of recent advances in soft and hard magnetic materials and developments in power electronics, microprocessors and digital control strategies, and the continuing demand for higher performance motion control systems, there appears to be more research and development activity in magnetic actuators for applications spanning all market sectors than at any time. In this dissertation, a rational approach for switching the states of permanent magnets through an on-board magnetization process is presented. The resulting dynamic systems are referred to as trans-permanent magnetic systems (T-PM). The first part of this research focuses on the governing equations needed for the analysis of T-PM systems. Their feasibility is demonstrated experimentally. In doing so, a method that has the potential of leading to new ultra-low power designs for electromechanical devices is introduced. In the second part of this research, the aforementioned developments in T-PM are applied to the problem of low power valves. Whereas alternate approaches to low power valve control may utilize latching mechanisms to maintain valve position during inactive periods, an approach that eliminates latching mechanisms is presented. Instead, the principles of T-PM are employed to switch the states of permanent magnets; the used of permanent magnets instead of electromagnets eliminates power consumption during inactive periods, thereby reducing power consumption to ultra-low levels. The magnets in a T-PM actuator are configured in a stack. The relationships between the strength and number of magnets in the stack and the stroke and resolution of the actuator are developed. This dissertation reports on the design and testing of a prototype valve actuator that uses a stack pf T-PM with

  3. Theoretical and experimental studies of a magnetically actuated valveless micropump

    NASA Astrophysics Data System (ADS)

    Ashouri, Majid; Behshad Shafii, Mohammad; Moosavi, Ali

    2017-01-01

    This paper presents the prototype design, fabrication, and characterization of a magnetically actuated micropump. The pump body consists of three nozzle/diffuser elements and two pumping chambers connected to the ends of a flat-wall pumping cylinder. A cylindrical permanent magnet placed inside the pumping cylinder acts as a piston which reciprocates by using an external magnetic actuator driven by a motor. The magnetic piston is covered by a ferrofluid to provide self-sealing capability. A prototype composed of three bonded layers of polymethyl-methacrylate (PMMA) has been fabricated. Water has been successfully pumped at pressures of up to 750 Pa and flow rates of up to 700 µl min-1 while working at the piston actuation frequency of 4 and 5 Hz, respectively. 3D numerical simulations are also carried out to study the performance of the pump. The best experimental and numerical volumetric efficiency of the pump are about 7 and 8%, respectively, at the piston speed of 0.03 m s-1. The contactless external actuation feature of the design enables integration of the pump with other PMMA-based microfluidic systems with low cost and disposability.

  4. Geometric optimization of magnetically actuated MEMS micromirrors

    NASA Astrophysics Data System (ADS)

    Pieri, Francesco

    2016-10-01

    In this paper we develop a set of self-consistent equations describing the static and resonance characteristics of a rectangular micromirror actuated by driving a current into a multicoil inductor fabricated on the micromirror surface. Under fairly general assumptions, these equations can be solved analytically for the most common design targets, such as the driving current, deflection angle, resonance frequency, and overall dimensions. We use this solutions to optimize the micromirror geometry by minimization of a linear objective function. The tradeoffs that emerge from optimization data allow simple quantitative design of low current, low size mirrors.

  5. Selective actuation of arrays of carbon nanotubes using magnetic resonance.

    PubMed

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

    2013-07-23

    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.

  6. Magnetically-actuated, bead-enhanced silicon photonic immunosensor

    PubMed Central

    Valera, Enrique; McClellan, Melinda S.; Bailey, Ryan C.

    2015-01-01

    Magnetic actuation has been introduced to an optical immunosensor technology resulting in improvements in both rapidity and limit of detection for an assay quantitating low concentrations of a representative protein biomarker. For purposes of demonstration, an assay was designed for monocyte chemotactic protein 1 (MCP-1), a small cytokine which regulates migration and infiltration of monocytes and macrophages, and is an emerging biomarker for several diseases. The immunosensor is based on arrays of highly multiplexed silicon photonic microring resonators. A one-step sandwich immunoassay was performed and the signal was further enhanced through a tertiary recognition event between biotinylated tracer antibodies and streptavidin-coated magnetic beads. By integrating a magnet under the sensor chip, magnetic beads were rapidly directed towards the sensor surface resulting in improved assay performance metrics. Notably, the time required in the bead binding step was reduced by a factor of 11 (4 vs 45 min), leading to an overall decrease in assay time from 73 min to 32 min. The magnetically-actuated assay also lowered the limit of detection (LOD) for MCP-1 from 124 pg mL−1 down to 57 pg mL−1. In sum, the addition of magnetic actuation into bead-enhanced sandwich assays on a silicon photonic biosensor platform might facilitate improved detection of biomarkers in point-of-care diagnostics settings. PMID:26528374

  7. Analysis and decoupling control of a permanent magnet spherical actuator

    NASA Astrophysics Data System (ADS)

    Zhang, Liang; Chen, Weihai; Liu, Jingmeng; Wu, Xingming

    2013-12-01

    This paper presents the analysis and decoupling control of a spherical actuator, which is capable of performing three degree-of-freedom motion in one joint. The proposed actuator consists of a rotor with multiple PM (Permanent Magnet) poles in a circle and a stator with circumferential coils in three layers. Based on this actuator design, a decoupling control approach is developed. Unlike existing control methods that each coil is responsible for both the spinning and tilting motion, the proposed control strategy specifies the function of each coil. Specifically, the spinning motion is governed by the middle layer coils with a step control approach; while the tilting motion is regulated by upper and lower coils with a computed torque control method. Experiments have been conducted on the prototype to verify the validity of the design procedure, and the experimental results demonstrate the effectiveness of the analysis and control strategy.

  8. Oscillating magnetic field-actuated microvalves for micro- and nanofluidics

    NASA Astrophysics Data System (ADS)

    Ghosh, Santaneel; Yang, Chao; Cai, Tong; Hu, Zhibing; Neogi, Arup

    2009-07-01

    The feasibility of using tunable magnetic nanoparticles embedded in cylindrical hydrogel materials as a flow regulator via thermo-mechanical gating is studied within microfluidic channels. Ferromagnetic nanoparticles (Fe3O4) encapsulated within a thermo-sensitive polymer network (-poly(N-isopropylacrylamide) (PNIPAM)) was polymerized inside 300 µm diameter micro-capillary tubes. An oscillating magnetic field range 20-125 Oe, (100-1000 kHz) was used to induce heat and control the valving action. Valving action was effectively regulated by modulating the magnetically responsive PNIPAM networks (MPNIPAM) and thereby physically regulating the harmonics (swelling and shrinking) of the polymer monolith inside the microchannel. Magnetic properties in terms of saturation magnetization, remanence and coercivity of the designed system have been extracted for data accuracy. The optimum concentration of NIPAM monomer in the polymer matrix and the embedded nanoparticles yield ~80% volume shrinkage inside the microchannel, which is close to the undoped PNIPAM system, without compromising the oscillating field induced heating. Very importantly, the oscillating field-actuated de-swelling response time is ~3 s, which is significantly faster than the thermal actuation, and in addition the microvalve exhibits a faster response time compared with the macrovalve (MPNIPAM monolith inside 1500 µm diameter channel). The enhanced shrinkage rate and the actuation efficiency might be ideal for many biomedical applications, including synergistic application of heat and sustained releasing capability of chemotherapeutic agents.

  9. The triathlon of magnetic actuation: Rolling, propelling, swimming with a single magnetic material

    NASA Astrophysics Data System (ADS)

    Vach, Peter J.; Faivre, Damien

    2015-03-01

    Magnetic actuation of microscopic devices in a liquid environment has been achieved in various ways, which can be grouped into rolling, propelling and swimming. Previous actuators were designed with a focus on one particular type of magnetic actuation. We have shown earlier that efficient magnetic propellers can be selected from randomly shaped magnetic nanostructures synthesized in solution. Here we show that these synthesized nanostructures can be used for all three types of magnetic actuation. Whereas it might not be surprising that single structures can roll in addition to propelling, swimming is unexpectedly also observed using the same material. In this case, however, the magnetically guided self-assembly of several individual particles into chain-like structures is necessary to obtain swimmers, since individual rigid nanostructures cannot swim. Interestingly, the direction of the swimming motion is not necessarily parallel to the long axis of the chain-like assembly, a finding that had been theoretically expected but experimentally not observed so far. Our findings show that the range of structures that can be effectively actuated by external magnetic fields is much broader than assumed until now. This could open up new opportunities for the design of magnetically actuated devices.

  10. The triathlon of magnetic actuation: Rolling, propelling, swimming with a single magnetic material

    PubMed Central

    Vach, Peter J.; Faivre, Damien

    2015-01-01

    Magnetic actuation of microscopic devices in a liquid environment has been achieved in various ways, which can be grouped into rolling, propelling and swimming. Previous actuators were designed with a focus on one particular type of magnetic actuation. We have shown earlier that efficient magnetic propellers can be selected from randomly shaped magnetic nanostructures synthesized in solution. Here we show that these synthesized nanostructures can be used for all three types of magnetic actuation. Whereas it might not be surprising that single structures can roll in addition to propelling, swimming is unexpectedly also observed using the same material. In this case, however, the magnetically guided self-assembly of several individual particles into chain-like structures is necessary to obtain swimmers, since individual rigid nanostructures cannot swim. Interestingly, the direction of the swimming motion is not necessarily parallel to the long axis of the chain-like assembly, a finding that had been theoretically expected but experimentally not observed so far. Our findings show that the range of structures that can be effectively actuated by external magnetic fields is much broader than assumed until now. This could open up new opportunities for the design of magnetically actuated devices. PMID:25791721

  11. Magnetic actuator intended for left ventricular assist system

    NASA Astrophysics Data System (ADS)

    Saotome, H.; Okada, T.

    2006-04-01

    With the goal of developing an artificial heart, the authors fabricated a prototype pump employing a linear motion magnetic actuator, and carried out performance tests. The actuator is composed of two disk-shaped Nd-Fe-B magnets having a diameter of 80 mm and a thickness of 7 mm. The disks are magnetized in the direction normal to the circular surface, and are formed by semicircular pieces; one semicircle serves as a N pole and the other as a S pole. The magnets face each other in the actuator. One magnet is limited to spin around its axis while the second magnet is limited to move in linear motion along its axis. In this way, the circumferential rotation of one of the magnets produces reciprocating forces on the other magnet, causing it to move back and forth. This coupled action produces a pumping motion. Because the two magnets are magnetically coupled without any mechanical contact, the rotating magnet does not have to be implanted and should be placed outside the body. The rotating magnet is driven by a motor. The motor power is magnetically conveyed, via the rotating magnet, to the implanted linear motion magnet through the skin. The proposed system yields no problems with infection that would otherwise require careful treatment in a system employing a tube penetrating the skin for power transmission. Comparison of the proposed system with another system using a transcutaneous transformer shows that our system has good potential to occupy a smaller space in the body, because it obviates implantation of a secondary part of the transformer, a power supply, and armature windings. The dimensions of the trial pump are designed in accordance with the fluid mechanical specifications of a human left ventricle, by computing magnetic fields that provide the magnetic forces on the magnets. The output power of the trial pump, 1.0 W at 87 beats/min, is experimentally obtained under the pressure and flow conditions of water, 100 mm Hg and 4.5 l/min.

  12. Note: Seesaw actuation of atomic force microscope probes for improved imaging bandwidth and displacement range

    SciTech Connect

    Torun, H.; Torello, D.; Degertekin, F. L.

    2011-08-15

    The authors describe a method of actuation for atomic force microscope (AFM) probes to improve imaging speed and displacement range simultaneously. Unlike conventional piezoelectric tube actuation, the proposed method involves a lever and fulcrum ''seesaw'' like actuation mechanism that uses a small, fast piezoelectric transducer. The lever arm of the seesaw mechanism increases the apparent displacement range by an adjustable gain factor, overcoming the standard tradeoff between imaging speed and displacement range. Experimental characterization of a cantilever holder implementing the method is provided together with comparative line scans obtained with contact mode imaging. An imaging bandwidth of 30 kHz in air with the current setup was demonstrated.

  13. Triaxial Probe Magnetic Data Analysis

    NASA Technical Reports Server (NTRS)

    Shultz, Kimberly; Whittlesey, Albert; Narvaez, Pablo

    2007-01-01

    The Triaxial Magnetic Moment Analysis software uses measured magnetic field test data to compute dipole and quadrupole moment information from a hardware element. It is used to support JPL projects needing magnetic control and an understanding of the spacecraft-generated magnetic fields. Evaluation of the magnetic moment of an object consists of three steps: acquisition, conditioning, and analysis. This version of existing software was extensively rewritten for easier data acquisition, data analysis, and report presentation, including immediate feedback to the test operator during data acquisition. While prior JPL computer codes provided the same data content, this program has a better graphic display including original data overlaid with reconstructed results to show goodness of fit accuracy and better appearance of the report graphic page. Data are acquired using three magnetometers and two rotations of the device under test. A clean acquisition user interface presents required numeric data and graphic summaries, and the analysis module yields the best fit (least squares) for the magnetic dipole and/or quadrupole moment of a device. The acquisition module allows the user to record multiple data sets, selecting the best data to analyze, and is repeated three times for each of the z-axial and y-axial rotations. In this update, the y-axial rotation starting position has been changed to an option, allowing either the x- or z-axis to point towards the magnetometer. The code has been rewritten to use three simultaneous axes of magnetic data (three probes), now using two "rotations" of the device under test rather than the previous three rotations, thus reducing handling activities on the device under test. The present version of the software gathers data in one-degree increments, which permits much better accuracy of the fit ted data than the coarser data acquisition of the prior software. The data-conditioning module provides a clean data set for the analysis module

  14. A motionless actuation system for magnetic shape memory devices

    NASA Astrophysics Data System (ADS)

    Armstrong, Andrew; Finn, Kevin; Hobza, Anthony; Lindquist, Paul; Rafla, Nader; Müllner, Peter

    2017-10-01

    Ni–Mn–Ga is a Magnetic Shape Memory (MSM) alloy that changes shape in response to a variable magnetic field. We can intentionally manipulate the shape of the material to function as an actuator, and the material can thus replace complicated small electromechanical systems. In previous work, a very simple and precise solid-state micropump was developed, but a mechanical rotation was required to translate the position of the magnetic field. This mechanical rotation defeats the purpose of the motionless solid-state device. Here we present a solid-state electromagnetic driver to linearly progress the position of the applied magnetic field and the associated shrinkage. The generated magnetic field was focused at either of two pole pieces, providing a mechanism for moving the localized shrinkage in the MSM element. We confirmed that our driver has sufficient strength to actuate the MSM element using optical microscopy. We validated the whole design by comparing results obtained with finite element analysis with the experimentally measured flux density. This drive system serves as a possible replacement to the mechanical rotation of the magnetic field by using a multi-pole electromagnet that sweeps the magnetic field across the MSM micropump element, solid-state switching the current to each pole piece in the multi-pole electromagnet.

  15. Magnetically-induced solid-phase microextraction fiber actuation system for quantitative headspace and liquid sampling

    DOEpatents

    Harvey, Chris; Carter, Jerry; Chambers, David M.

    2017-05-23

    A magnetically-induced SPME fiber actuation system includes a SPME fiber holder and a SPME fiber holder actuator, for holding and magnetically actuating a SPME fiber assembly. The SPME fiber holder has a plunger with a magnetic material to which the SPME fiber assembly is connected, and the magnetic SPME fiber holder actuator has an elongated barrel with a loading chamber for receiving the SPME fiber assembly-connected SPME fiber holder, and an external magnet which induces axial motion of the magnetic material of the plunger to extend/retract the SPME fiber from/into the protective needle of the SPME fiber assembly.

  16. Magnetic Shape Memory Alloys with High Actuation Forces

    DTIC Science & Technology

    2006-01-29

    0.3 Tesla [16], but rare earth metals are expensive [14]. PZT (lead-zirconate-titanate) piezoceramics result in a maximum strain of about 0.1% and...maximum actuation stress level of about 100 MPa [17] in an electric field of several hundred V/cm [15]. However, PZT is an oxide and thus brittle. By...Fabricate textured polycrystalline materials from selected Fe based compositions using powder consolidation under magnetic field via Equal channel

  17. Direct torsional actuation of microcantilevers using magnetic excitation

    SciTech Connect

    Gosvami, Nitya Nand; Nalam, Prathima C.; Tam, Qizhan; Carpick, Robert W.; Exarhos, Annemarie L.; Kikkawa, James M.

    2014-09-01

    Torsional mode dynamic force microscopy can be used for a wide range of studies including mapping lateral contact stiffness, torsional frequency or amplitude modulation imaging, and dynamic friction measurements of various materials. Piezo-actuation of the cantilever is commonly used, but it introduces spurious resonances, limiting the frequency range that can be sampled, and rendering the technique particularly difficult to apply in liquid medium where the cantilever oscillations are significantly damped. Here, we demonstrate a method that enables direct torsional actuation of cantilevers with high uniformity over wide frequency ranges by attaching a micrometer-scale magnetic bead on the back side of the cantilever. We show that when beads are magnetized along the width of the cantilever, efficient torsional actuation of the cantilevers can be achieved using a magnetic field produced from a solenoid placed underneath the sample. We demonstrate the capability of this technique by imaging atomic steps on graphite surfaces in tapping mode near the first torsional resonance of the cantilever in dodecane. The technique is also applied to map the variations in the lateral contact stiffness on the surface of graphite and polydiacetylene monolayers.

  18. Fabrication of nanotweezers and their remote actuation by magnetic fields.

    PubMed

    Iss, Cécile; Ortiz, Guillermo; Truong, Alain; Hou, Yanxia; Livache, Thierry; Calemczuk, Roberto; Sabon, Philippe; Gautier, Eric; Auffret, Stéphane; Buda-Prejbeanu, Liliana D; Strelkov, Nikita; Joisten, Hélène; Dieny, Bernard

    2017-03-27

    A new kind of nanodevice that acts like tweezers through remote actuation by an external magnetic field is designed. Such device is meant to mechanically grab micrometric objects. The nanotweezers are built by using a top-down approach and are made of two parallelepipedic microelements, at least one of them being magnetic, bound by a flexible nanohinge. The presence of an external magnetic field induces a torque on the magnetic elements that competes with the elastic torque provided by the nanohinge. A model is established in order to evaluate the values of the balanced torques as a function of the tweezers opening angles. The results of the calculations are confronted to the expected values and validate the overall working principle of the magnetic nanotweezers.

  19. Magnetic fish-robot based on multi-motion control of a flexible magnetic actuator.

    PubMed

    Kim, Sung Hoon; Shin, Kyoosik; Hashi, Shuichiro; Ishiyama, Kazushi

    2012-09-01

    This paper presents a biologically inspired fish-robot driven by a single flexible magnetic actuator with a rotating magnetic field in a three-axis Helmholtz coil. Generally, magnetic fish-robots are powered by alternating and gradient magnetic fields, which provide a single motion such as bending the fish-robot's fins. On the other hand, a flexible magnetic actuator driven by an external rotating magnetic field can create several gaits such as the bending vibration, the twisting vibration, and their combination. Most magnetic fish-like micro-robots do not have pectoral fins on the side and are simply propelled by the tail fin. The proposed robot can swim and perform a variety of maneuvers with the addition of pectoral fins and control of the magnetic torque direction. In this paper, we find that the robot's dynamic actuation correlates with the magnetic actuator and the rotating magnetic field. The proposed robot is also equipped with new features, such as a total of six degrees of freedom, a new control method that stabilizes posture, three-dimensional swimming, a new velocity control, and new turning abilities.

  20. Integrated lab-on-chip biosensing systems based on magnetic particle actuation--a comprehensive review.

    PubMed

    van Reenen, Alexander; de Jong, Arthur M; den Toonder, Jaap M J; Prins, Menno W J

    2014-06-21

    The demand for easy to use and cost effective medical technologies inspires scientists to develop innovative lab-on-chip technologies for point-of-care in vitro diagnostic testing. To fulfill medical needs, the tests should be rapid, sensitive, quantitative, and miniaturizable, and need to integrate all steps from sample-in to result-out. Here, we review the use of magnetic particles actuated by magnetic fields to perform the different process steps that are required for integrated lab-on-chip diagnostic assays. We discuss the use of magnetic particles to mix fluids, to capture specific analytes, to concentrate analytes, to transfer analytes from one solution to another, to label analytes, to perform stringency and washing steps, and to probe biophysical properties of the analytes, distinguishing methodologies with fluid flow and without fluid flow (stationary microfluidics). Our review focuses on efforts to combine and integrate different magnetically actuated assay steps, with the vision that it will become possible in the future to realize integrated lab-on-chip biosensing assays in which all assay process steps are controlled and optimized by magnetic forces.

  1. Magnetic actuator for the control and mixing of magnetic bead-based reactions on-chip.

    PubMed

    Berenguel-Alonso, Miguel; Granados, Xavier; Faraudo, Jordi; Alonso-Chamarro, Julián; Puyol, Mar

    2014-10-01

    While magnetic bead (MB)-based bioassays have been implemented in integrated devices, their handling on-chip is normally either not optimal--i.e. only trapping is achieved, with aggregation of the beads--or requires complex actuator systems. Herein, we describe a simple and low-cost magnetic actuator to trap and move MBs within a microfluidic chamber in order to enhance the mixing of a MB-based reaction. The magnetic actuator consists of a CD-shaped plastic unit with an arrangement of embedded magnets which, when rotating, generate the mixing. The magnetic actuator has been used to enhance the amplification reaction of an enzyme-linked fluorescence immunoassay to detect Escherichia coli O157:H7 whole cells, an enterohemorrhagic strain, which have caused several outbreaks in food and water samples. A 2.7-fold sensitivity enhancement was attained with a detection limit of 603 colony-forming units (CFU) /mL, when employing the magnetic actuator.

  2. Computational modeling of magnetically actuated propellant orientation

    NASA Technical Reports Server (NTRS)

    Hochstein, John I.

    1996-01-01

    spacecraft propellant tanks: magnetic fields.

  3. Ti Ni shape memory alloy film-actuated microstructures for a MEMS probe card

    NASA Astrophysics Data System (ADS)

    Namazu, Takahiro; Tashiro, Youichi; Inoue, Shozo

    2007-01-01

    This paper describes the development of a novel silicon (Si) cantilever beam device actuated by titanium-nickel (Ti-Ni) shape memory alloy (SMA) films. A Ti-Ni SMA film can yield high work output per unit volume, so a Ti-Ni film-actuated Si cantilever beam device is a prospective tool for use as a microelectromechanical system (MEMS) probe card that provides a relatively large contact force between the probe and electrode pad in spite of its minute size. Before fabrication of the device, the thermomechanical deformation behavior of Ti-Ni SMA films with various compositions was investigated in order to determine a sufficient constituent film for a MEMS actuator. As a result, Ti-Ni films having a Ti content of 50.2 to 52.6 atomic% (at%) were found to be usable for operation as a room temperature actuator. We have developed a Ti-Ni film-actuated Si cantilever beam device, which can produce a contact force by the cantilever bending when in contact, and also by the shape memory effect (SME) of the Ti-Ni film arising from Joule heating. The SME of the Ti-Ni film can generate an additional average contact force of 200 µN with application of 500 mW to the film. In addition to physical contact, a dependable electric contact between the Au film-coated probe tip and the Al film electrode was achieved. However, the contact resistance exhibited an average value of 25 Ω, which would have to be reduced for practical use. Reliability tests confirmed the durability of the Ti-Ni film-actuated Si cantilever-beam, in that the contact resistance was constant throughout a large number of physical contacts (>104 times).

  4. Magnetic force induced tristability for dielectric elastomer actuators

    NASA Astrophysics Data System (ADS)

    Li, Xin-Qiang; Li, Wen-Bo; Zhang, Wen-Ming; Zou, Hong-Xiang; Peng, Zhi-Ke; Meng, Guang

    2017-10-01

    This paper presents a novel dielectric elastomer actuator (DEA) with three stable states. By introducing magnetic forces and coupling them with two cone dielectric elastomer (DE) films, an inherent tristability for the DEA is obtained with a compact design. It is easy to switch between the three stable states by controlling the voltages applied to the DE films. A theoretical model of the system’s potential energy that contains the free energy of the DEs and the potential energy of the applied magnetic field was developed for the tristable mechanism. The experimental results demonstrate that controllable transitions between the three stable states can be achieved with this design by applying over-critical voltages to the various DE films. The maximum dynamic range of the DEA can exceed 53.8% of the total length of the device and the DE’s creep speed was accelerated under the action of the magnetic field.

  5. Micro-fluidic actuation using magnetic artificial cilia.

    PubMed

    Fahrni, Francis; Prins, Menno W J; van Ijzendoorn, Leo J

    2009-12-07

    We demonstrate advanced fluid manipulations using magnetic polymeric artificial cilia on the walls of a microfluidic channel. In nature, cilia are little hairs covering the surface of micro-organisms which enable them to manipulate a fluid on the micro-scale. The asymmetric movement of natural cilia is crucial to obtain a net fluid flow. We have developed a ferromagnetic polymer made from iron nanoparticles and polydimethylsiloxane, and describe a process that can structure the material into high aspect ratio lying artificial cilia with a length of 300 microm. These artificial cilia were actuated with a homogeneous rotating magnetic field (micro(0)H < 50 mT) generated with a compact external electromagnet. An asymmetric movement involving torsion could be created when the cilia were provided with a remanent magnetisation perpendicular to the plane of rotation of the magnetic field vector. The artificial cilia could be actuated in fluid up to a frequency of approximately 50 Hz. In an aqueous solution in a microfluidic chamber we were able to generate rotational as well as translational fluid movements with fluid velocities up to approximately 0.5 mm s(-1).

  6. Characterization of magnetically actuated resonant cantilevers in viscous fluids

    NASA Astrophysics Data System (ADS)

    Vančura, Cyril; Lichtenberg, Jan; Hierlemann, Andreas; Josse, Fabien

    2005-10-01

    The vibration behavior of magnetically actuated resonant microcantilevers immersed in viscous fluids has been studied. A dependence of the resonance frequency and the quality factor (Q factor) on the fluid properties, such as density and viscosity and on the cantilever geometry is described. Various cantilever geometries are analyzed in pure water and glycerol solutions, and the results are explained in terms of the added displaced fluid mass and the fluid damping force for both the resonance frequency and the quality factor. An in-depth knowledge and understanding of such systems is necessary when analyzing resonant cantilevers as biochemical sensors in liquid environments.

  7. Magnetic field concentrator for probing optical magnetic metamaterials.

    PubMed

    Antosiewicz, Tomasz J; Wróbel, Piotr; Szoplik, Tomasz

    2010-12-06

    Development of all dielectric and plasmonic metamaterials with a tunable optical frequency magnetic response creates a need for new inspection techniques. We propose a method of measuring magnetic responses of such metamaterials within a wide range of optical frequencies with a single probe. A tapered fiber probe with a radially corrugated metal coating concentrates azimuthally polarized light in the near-field into a subwavelength spot the longitudinal magnetic field component which is much stronger than the perpendicular electric one. The active probe may be used in a future scanning near-field magnetic microscope for studies of magnetic responses of subwavelength elementary cells of metamaterials.

  8. Analytical model of an Annular Momentum Control Device (AMCD) laboratory test model magnetic bearing actuator

    NASA Technical Reports Server (NTRS)

    Groom, N. J.

    1979-01-01

    An analytical model of an Annular Momentum Control Device (AMCD) laboratory test model magnetic bearing actuator with permanent magnet fluxbiasing is presented. An AMCD consists of a spinning annular rim which is suspended by a noncontacting linear electromagnetic spin motor. The actuator is treated as a lumped-parameter electromechanical system in the development of the model.

  9. A magnetically actuated anchoring system for a wireless endoscopic capsule.

    PubMed

    Zhou, Hao; Alici, Gursel; Munoz, Fredy

    2016-12-01

    In this study, we propose a new magnetically actuated anchoring system for wireless capsule endoscopes (WCE) by employing the principle of a switchable magnetic spring. A force model is derived to predict the magnetic force needed to support the interaction between the anchors and the intestinal lumen. The theoretical and experimental analysis conducted shows that the magnetic spring is capable of providing the force needed to activate the anchoring mechanism, which consists of four foldable legs. A prototype capsule with a size comparable with the size of a commercial WCE was designed, fabricated, and tested. The in-vitro tests with a real small intestine show that the proposed anchoring mechanism is able to raise the friction force between the anchoring legs and inner wall of the intestine by more than two times after its activation using an external magnetic field. Experimental results presented demonstrate that the proposed anchoring system, which has a low foot-print not taking up too much space on the capsule, can provide a reliable anchoring capability with the capsule inside the intestinal lumen.

  10. Magnetically actuated and controlled colloidal sphere-pair swimmer

    NASA Astrophysics Data System (ADS)

    Ran, Sijie; Guez, Allon; Friedman, Gary

    2016-12-01

    Magnetically actuated swimming of microscopic objects has been attracting attention partly due to its promising applications in the bio-medical field and partly due to interesting physics of swimming in general. While colloidal particles that are free to move in fluid can be an attractive swimming system due it its simplicity and ability to assemble in situ, stability of their dynamics and the possibility of stable swimming behavior in periodically varying magnetic fields has not been considered. Dynamic behavior of two magnetically interacting colloidal particles subjected to rotating magnetic field of switching frequency is analyzed here and is shown to result in stable swimming without any stabilizing feedback. A new mechanism of swimming that relies only on rotations of the particles themselves and of the particle pair axis is found to dominate the swimming dynamics of the colloidal particle pair. Simulation results and analytical arguments demonstrate that this swimming strategy compares favorably to dragging the particles with an external magnetic force when colloidal particle sizes are reduced.

  11. Magnetically actuated artificial cilia for optimum mixing performance in microfluidics.

    PubMed

    Chen, Chia-Yuan; Chen, Chia-Yun; Lin, Cheng-Yi; Hu, Ya-Ting

    2013-07-21

    Contemporary lab-chip devices require efficient, high-performance mixing capability. A series of artificial cilia with embedded magnetic particles was fabricated to achieve precise flow manipulation through magnetically driven control. These fabricated structures were actuated in a homogeneous magnetic field generated by a built-in magnetic coil system for various beating cycles inside a microchannel. Three representative trajectories, namely, circular motion, back-and-forth oscillation, and a figure-of-eight pattern, of artificial cilia were designed and generated to mimic the motion of actual cilia. Homogeneous mixing of two highly viscous (>25 centipoise) dyed solutions by using the figure-of-eight trajectory achieved a mixing efficiency of approximately 86%. The underlying relationship between ciliated structures and the induced flow fields was further elucidated by performing a hydrodynamic analysis with micro-particle image velocimetry. In addition, a numerical modeling method which used a fluid structure interaction module was applied to provide quantitative 3D illustrations of induced flow patterns, including vortical structures and vortex core locations. The results reveal that both the magnitude and distribution of induced vortices primarily affect the mixing performance of two viscous flow streams. By using magnetically controlled artificial cilia along with the presented analytical paradigms, a new active flow mixing strategy was suggested to efficiently transport/agitate flows for microfluidics and biomedical applications.

  12. A novel dog-bone oscillating AFM probe with thermal actuation and piezoresistive detection.

    PubMed

    Xiong, Zhuang; Mairiaux, Estelle; Walter, Benjamin; Faucher, Marc; Buchaillot, Lionel; Legrand, Bernard

    2014-10-31

    In order to effectively increase the resonance frequency and the quality factor of atomic force microscope (AFM) probes, a novel oscillating probe based on a dog-bone shaped MEMS resonator was conceived, designed, fabricated and evaluated. The novel probe with 400 μm in length, 100 μm in width and 5 μm in thickness was enabled to feature MHz resonance frequencies with integrated thermal actuation and piezoresistive detection. Standard silicon micromachining was employed. Both electrical and optical measurements were carried out in air. The resonance frequency and the quality factor of the novel probe were measured to be 5.4 MHz and 4000 respectively, which are much higher than those (about several hundreds of kHz) of commonly used cantilever probes. The probe was mounted onto a commercial AFM set-up through a dedicated probe-holder and circuit board. Topographic images of patterned resist samples were obtained. It is expected that the resonance frequency and the measurement bandwidth of such probes will be further increased by a proper downscaling, thus leading to a significant increase in the scanning speed capability of AFM instruments.

  13. A Novel Dog-Bone Oscillating AFM Probe with Thermal Actuation and Piezoresistive Detection †

    PubMed Central

    Xiong, Zhuang; Mairiaux, Estelle; Walter, Benjamin; Faucher, Marc; Buchaillot, Lionel; Legrand, Bernard

    2014-01-01

    In order to effectively increase the resonance frequency and the quality factor of atomic force microscope (AFM) probes, a novel oscillating probe based on a dog-bone shaped MEMS resonator was conceived, designed, fabricated and evaluated. The novel probe with 400 μm in length, 100 μm in width and 5 μm in thickness was enabled to feature MHz resonance frequencies with integrated thermal actuation and piezoresistive detection. Standard silicon micromachining was employed. Both electrical and optical measurements were carried out in air. The resonance frequency and the quality factor of the novel probe were measured to be 5.4 MHz and 4000 respectively, which are much higher than those (about several hundreds of kHz) of commonly used cantilever probes. The probe was mounted onto a commercial AFM set-up through a dedicated probe-holder and circuit board. Topographic images of patterned resist samples were obtained. It is expected that the resonance frequency and the measurement bandwidth of such probes will be further increased by a proper downscaling, thus leading to a significant increase in the scanning speed capability of AFM instruments. PMID:25365463

  14. Magnetic actuated FR4 scanners for compact spectrometers

    NASA Astrophysics Data System (ADS)

    Ataman, Çağlar; Urey, Hakan

    2008-04-01

    A novel magnetic actuated polymer optical platform is integrated into a Michelson interferometer type Fourier transform infrared spectrometer. The proposed advantages of the novel platform over existing approaches, such as MEMS spectrometers, or bulky FTIR systems, include millimeter range dimensions providing a large clear aperture and enabling conventional machining for device fabrication, a controllable AC and/or DC motion both in rotational and translational modes, and low frequency operation. It has been demonstrated that the platform is capable of achieving 400μm DC deflection in ambient pressure in the translational mode, and a total optical scan angle exceeding 60 degrees in the resonant rotational mode. A Michelson type Fourier transform spectrometer was built using a retro-reflector bearing FR4 platform and a spectral resolution of 25cm -1 is demonstrated with this setup. In addition, possible use of the same platform in various other spectrometer configurations and methods to improve the motion precision are discussed.

  15. Magnetically actuated propulsion at low Reynolds numbers: towards nanoscale control

    NASA Astrophysics Data System (ADS)

    Fischer, Peer; Ghosh, Ambarish

    2011-02-01

    Significant progress has been made in the fabrication of micron and sub-micron structures whose motion can be controlled in liquids under ambient conditions. The aim of many of these engineering endeavors is to be able to build and propel an artificial micro-structure that rivals the versatility of biological swimmers of similar size, e.g. motile bacterial cells. Applications for such artificial ``micro-bots'' are envisioned to range from microrheology to targeted drug delivery and microsurgery, and require full motion-control under ambient conditions. In this Mini-Review we discuss the construction, actuation, and operation of several devices that have recently been reported, especially systems that can be controlled by and propelled with homogenous magnetic fields. We describe the fabrication and associated experimental challenges and discuss potential applications.

  16. Preliminary validation of Sm-Fe-N magnetic silicone rubber for a flexible magnetic actuator

    NASA Astrophysics Data System (ADS)

    Fukushi, Takanori; Kim, Sung Hoon; Hashi, Shuichiro; Ishiyama, Kazushi

    2014-06-01

    In this paper, we present a new approach for a flexible magnetic actuator (FMA) using Sm-Fe-N magnetic silicone rubber (MSR) that has a higher degree of freedom (DOF) in shape, flexibility, ease of fabrication and combinative ability than permanent magnets. To verify its potential for use in an FMA, we examined its magnetic and elastic properties and focused on magnetic torque control within a uniform rotating magnetic field. Silicone rubber liquid and hardener were mixed with Sm-Fe-N powder and poured into a mold. The fabricated Sm-Fe-N MSR included Sm-Fe-N powder of 13.5, 17.3, and 21.2 vol% ratio. The physical and elastic properties were determined by a vibrating sample magnetometer (VSM) and elastic load, respectively. Furthermore, we fabricated two FMAs (multiple-magnetic anisotropy type and spiral-type), and evaluated the suitability of the Sm-Fe-N MSR for magnetic wireless actuators based on magnetic torque control.

  17. Fabrication of cantilever probes with integrated piezoresistive read-out and built-in piezoelectric actuators

    NASA Astrophysics Data System (ADS)

    Olson, Steve; Altemus, Bruce; Sankaran, Balasubramanian; Tokranova, Natalya; Geer, Robert; Castracane, James; Xu, Bai

    2005-01-01

    Micromachined cantilevers used as force probes in atomic force microscopy are extremely sensitive to a variety of environment factors such as acoustic noise, temperature and humidity. This unwanted interference can be exploited to produce highly sensitive systems with proper design and under precise conditions. In this paper, we report the development of a new generic process for the fabrication of a microprobe with integrated piezoresistive read-out and built-in piezoelectric actuators. The mechanical performance of cantilever probes of various dimensions was studied. The result from the Finite Element Analysis (FEA) was compared to the experimental results. Application of this probe in a nondestructive, general-purpose, near-field nanomechanical imaging system will be discussed.

  18. Ball bearing versus magnetic bearing reaction and momentum wheels as momentum actuators

    NASA Technical Reports Server (NTRS)

    Auer, W.

    1980-01-01

    Different bearing technologies of momentum actuators for the attitude control of satellites are compared and a guideline for the selection of the suitable momentum actuators or momentum actuator configurations to meet given mission goals with high reliability and low cost is developed. The comparison between ball bearing and magnetic bearing momentum actuators shows that given mission requirements can be economically met by employing the ball bearing technology without decreasing reliability and lifetime. However, for some special mission requirements, such as 'zero friction at zero speed,' fine pointing (met by vernier gimballing), and/or active damping, magnetic bearings may be advantageous. This makes it evident that magnetic bearing technology will not replace ball bearing technology for momentum actuators, but will supplement it for some special mission requirements.

  19. Surface Absorption Polarization Sensors (SAPS), Final Technical Report, Laser Probing of Immobilized SAPS Actuators Component

    SciTech Connect

    Joseph I. Cline

    2010-04-22

    propensity for the angular control of rotary motion to be strongly influenced by the presence of the H+ analyte: the SAPS actuators can readily detect the presence of a H+ analyte at 1 equivalent concentration. Because the total number of SAPS actuators in the probe volume of the film is small, the amount of analyte detectable can be very low. A variety of SAPS actuator structures based on dibenzofulvene rotors are possible that could bind other analytes. It appears that analyte binding that alters the electron density in the dibenzofulvene ring is sufficient to create a detectable change in the rotary efficiency. If the analyte is strongly bound to the rotor, the SAPS actuator behaves in a dosimeter mode. Weak, reversible binding would allow for monitoring of varying concentrations.

  20. Compensator-based 6-DOF control for probe asteroid-orbital-frame hovering with actuator limitations

    NASA Astrophysics Data System (ADS)

    Liu, Xiaosong; Zhang, Peng; Liu, Keping; Li, Yuanchun

    2016-05-01

    This paper is concerned with 6-DOF control of a probe hovering in the orbital frame of an asteroid. Considering the requirements of the scientific instruments pointing direction and orbital position in practical missions, the coordinate control of relative attitude and orbit between the probe and target asteroid is imperative. A 6-DOF dynamic equation describing the relative translational and rotational motion of a probe in the asteroid's orbital frame is derived, taking the irregular gravitation, model and parameter uncertainties and external disturbances into account. An adaptive sliding mode controller is employed to guarantee the convergence of the state error, where the adaptation law is used to estimate the unknown upper bound of system uncertainty. Then the controller is improved to deal with the practical problem of actuator limitations by introducing a RBF neural network compensator, which is used to approximate the difference between the actual control with magnitude constraint and the designed nominal control law. The closed-loop system is proved to be asymptotically stable through the Lyapunov stability analysis. Numerical simulations are performed to compare the performances of the preceding designed control laws. Simulation results demonstrate the validity of the control scheme using the compensator-based adaptive sliding mode control law in the presence of actuator limitations, system uncertainty and external disturbance.

  1. Magnetic Probing of Core Geodynamics

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.

    2004-01-01

    To better understand geomagnetic theory and observation, we can use spatial magnetic spectra for the main field and secular variation to test core dynmcal hypotheses against seismology. The hypotheses lead to theoretical spectra which are fitted to observational spectra. Each fit yields an estimate of the radius of Earth's core and uncertainty. If this agrees with the seismologic value, then the hypothes pass the test. A new way to obtain theoretical spectra extends the hydromagnetic scale analysis of Benton to scale-variant field and flow. For narrow scale flow and a dynamically weak field by the top of Earth's core, this yields a generalized Stevenson-McLeod spectrum for the core-source field, and a secular variation spectrum modulated by a cubic polynomial in spherical harmonic degree n. The former passes the tests. The latter passes many tests, but does not describe rapid dipole decline and quadrupole rebound; some tests suggest it is a bit hard, or rich in narrow scale change. In a core geodynamo, motion of the fluid conductor does work against the Lorentz force. This converts kinetic into magnetic energy which, in turn, is lost to heat via Ohmic dissipation. In the analysis at lentgh-scale l/k, if one presumes kinetic energy is converted in either eddy- overturning or magnetic free-decay time-scales, then Kolmogorov or other spectra in conflict with observational spectra can result. Instead, the rate work is done roughly balances the dissipation rate, which is consistent with small scale flow. The conversion time-scale depends on dynamical constraints. These are summarized by the magneto-geostrophic vertical vorticity balance by the top of the core, which includes anisotropic effects of rotation, the magnetic field, and the core- mantle boundary. The resulting theoretical spectra for the core-source field and its SV are far more compatible with observation. The conversion time-scale of order l20 years is pseudo-scale-invarient. Magnetic spectra of other

  2. Magnetic Probing of Core Geodynamics

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.

    2004-01-01

    To better understand geomagnetic theory and observation, we can use spatial magnetic spectra for the main field and secular variation to test core dynamical hypotheses against seismology. The hypotheses lead to theoretical spectra which are fitted to observational spectra. Each fit yields an estimate of the radius of Earth's core and uncertainty. If this agrees with the seismologic value, then the hypothesis passes the test. A new way to obtain theoretical spectra extends the hydromagnetic scale analysis of Benton to scale-variant field and flow. For narrow scale flow and a dynamically weak field by the top of Earth's core, this yields a generalized Stevenson-McLeod spectrum for the core-source field, and a secular variation spectrum modulated by a cubic polynomial in spherical harmonic degree n. The former passes the tests. The latter passes many tests, but does not describe rapid dipole decline and quadrupole rebound; some tests suggest it is a bit hard, or rich in narrow scale range. In a core geodynamo, motion of the fluid conductor does work against the Lorentz force. This converts kinetic into magnetic energy which, in turn, is lost to heat via Ohmic dissipation. In the analysis at length-scale 1/k, if one presumes kinetic energy is converted in either eddy-overturning or magnetic free-decay time-scales, then Kolmogorov or other spectra in conflict with observational spectra can result. Instead, the rate work is done roughly balances the dissipation rate, which is consistent with small-scale flow. The conversion time-scale depends on dynamical constraints. These are summarized by the magnetogeostrophic vertical vorticity balance by the top of the core, which includes anisotropic effects of rotation, the magnetic field, and the core-mantle boundary. The resulting theoretical spectra for the core-source field and its SV are far more compatible with observation. The conversion time-scale of order 120 years is pseudo-scale-invariant. Magnetic spectra of other

  3. Magnetic Probing of Core Geodynamics

    NASA Astrophysics Data System (ADS)

    Voorhies, C. V.

    2004-05-01

    To better understand geomagnetic theory and observation, we can use spatial magnetic spectra for the main field and secular variation to test core dynamical hypotheses against seismology. The hypotheses lead to theoretical spectra which are fitted to observational spectra. Each fit yields an estimate of the radius of Earth's core and uncertainty. If this agrees with the seismologic value, then the hypotheses pass the test. A new way to obtain theoretical spectra extends the hydromagnetic scale analysis of Benton [1992; GAFD] to scale-variant field and flow [Voorhies, 2004; JGR-SE, in press]. For narrow scale flow and a dynamically weak field by the top of Earth's core, this yields a generalized Stevenson-McLeod spectrum for the core-source field [Voorhies, Sabaka and Purucker, 2002; JGR-P], and a secular variation spectrum modulated by a cubic polynomial in spherical harmonic degree n. The former passes the tests. The latter passes many tests, but does not describe rapid dipole decline and quadrupole rebound; some tests suggest it is a bit hard, or rich in narrow scale change. In a core geodynamo, motion of the fluid conductor does work against the Lorentz force. This converts kinetic into magnetic energy which, in turn, is lost to heat via Ohmic dissipation. In the analysis at length-scale 1/k, if one presumes kinetic energy is converted in either eddy-overturning or magnetic free-decay time-scales, then Kolmogorov or other spectra in conflict with observational spectra can result. Instead, the rate work is done roughly balances the dissipation rate, which is consistent with small scale flow. The conversion time-scale depends on dynamical constraints. These are summarized by the magneto-geostrophic vertical vorticity balance by the top of the core, which includes anisotropic effects of rotation, the magnetic field, and the core-mantle boundary. The resulting theoretical spectra for the core-source field and its SV are far more compatible with observation. The

  4. Magnetic Probing of Core Geodynamics

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.

    2004-01-01

    To better understand geomagnetic theory and observation, we can use spatial magnetic spectra for the main field and secular variation to test core dynamical hypotheses against seismology. The hypotheses lead to theoretical spectra which are fitted to observational spectra. Each fit yields an estimate of the radius of Earth's core and uncertainty. If this agrees with the seismologic value, then the hypothesis passes the test. A new way to obtain theoretical spectra extends the hydromagnetic scale analysis of Benton to scale-variant field and flow. For narrow scale flow and a dynamically weak field by the top of Earth's core, this yields a generalized Stevenson-McLeod spectrum for the core-source field, and a secular variation spectrum modulated by a cubic polynomial in spherical harmonic degree n. The former passes the tests. The latter passes many tests, but does not describe rapid dipole decline and quadrupole rebound; some tests suggest it is a bit hard, or rich in narrow scale range. In a core geodynamo, motion of the fluid conductor does work against the Lorentz force. This converts kinetic into magnetic energy which, in turn, is lost to heat via Ohmic dissipation. In the analysis at length-scale 1/k, if one presumes kinetic energy is converted in either eddy-overturning or magnetic free-decay time-scales, then Kolmogorov or other spectra in conflict with observational spectra can result. Instead, the rate work is done roughly balances the dissipation rate, which is consistent with small-scale flow. The conversion time-scale depends on dynamical constraints. These are summarized by the magnetogeostrophic vertical vorticity balance by the top of the core, which includes anisotropic effects of rotation, the magnetic field, and the core-mantle boundary. The resulting theoretical spectra for the core-source field and its SV are far more compatible with observation. The conversion time-scale of order 120 years is pseudo-scale-invariant. Magnetic spectra of other

  5. Magnetic Probing of Core Geodynamics

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.

    2004-01-01

    To better understand geomagnetic theory and observation, we can use spatial magnetic spectra for the main field and secular variation to test core dynmcal hypotheses against seismology. The hypotheses lead to theoretical spectra which are fitted to observational spectra. Each fit yields an estimate of the radius of Earth's core and uncertainty. If this agrees with the seismologic value, then the hypothes pass the test. A new way to obtain theoretical spectra extends the hydromagnetic scale analysis of Benton to scale-variant field and flow. For narrow scale flow and a dynamically weak field by the top of Earth's core, this yields a generalized Stevenson-McLeod spectrum for the core-source field, and a secular variation spectrum modulated by a cubic polynomial in spherical harmonic degree n. The former passes the tests. The latter passes many tests, but does not describe rapid dipole decline and quadrupole rebound; some tests suggest it is a bit hard, or rich in narrow scale change. In a core geodynamo, motion of the fluid conductor does work against the Lorentz force. This converts kinetic into magnetic energy which, in turn, is lost to heat via Ohmic dissipation. In the analysis at lentgh-scale l/k, if one presumes kinetic energy is converted in either eddy- overturning or magnetic free-decay time-scales, then Kolmogorov or other spectra in conflict with observational spectra can result. Instead, the rate work is done roughly balances the dissipation rate, which is consistent with small scale flow. The conversion time-scale depends on dynamical constraints. These are summarized by the magneto-geostrophic vertical vorticity balance by the top of the core, which includes anisotropic effects of rotation, the magnetic field, and the core- mantle boundary. The resulting theoretical spectra for the core-source field and its SV are far more compatible with observation. The conversion time-scale of order l20 years is pseudo-scale-invarient. Magnetic spectra of other

  6. Electromechanical simulation and test of rotating systems with magnetic bearing or piezoelectric actuator active vibration control

    NASA Technical Reports Server (NTRS)

    Palazzolo, Alan B.; Tang, Punan; Kim, Chaesil; Manchala, Daniel; Barrett, Tim; Kascak, Albert F.; Brown, Gerald; Montague, Gerald; Dirusso, Eliseo; Klusman, Steve

    1994-01-01

    This paper contains a summary of the experience of the authors in the field of electromechanical modeling for rotating machinery - active vibration control. Piezoelectric and magnetic bearing actuator based control are discussed.

  7. Micromachined piezoresistive proximal probe with integratedbimorph actuator for aligned single ion implantation

    SciTech Connect

    Persaud, A.; Ivanova, K.; Sarov, Y.; Ivanov, Tzv.; Volland, B.E.; Rangelow, I.W.; Nikolov, N.; Schenkel, T.; Djakov, V.; Jenkins, D.W.K.; Meijer, J.; Vogel, T.

    2006-10-01

    The authors report a microfabrication procedure ofself-actuated piezoresistive scanning probes (SAPSPs). They are designedfor a SAPSP instrument that is integrated with an ion beam for alignedsingle ion implantation in ultrahigh vacuum. The novelty of the design isan integrated hollow pyramid, instead of a previously mechanically handmounted pyramid [J. Vac. Sci. Technol. B 23, 2798 (2005)]. Thepyramidhas dual purpose. First it collimates the ion beam and suppressessecondary particles from the back side of the cantilever, so thatsecondary particles from the target material can be used for single iondetection. Second the pyramid also provides an atomic force microscopetip for the scanning probe. A crucial step in the fabrication is the backside opening via etching for the hollow pyramid. The fabricationprocedure will be discussed in detail.

  8. Probing Magnetic Fields with GALFACTS

    NASA Astrophysics Data System (ADS)

    George, S. J.; Stil, J. M.; Andrecut, M.; Taylor, A. R.

    2012-09-01

    GALFACTS is a large-area spectro-polarimetric survey on the Arecibo Radio telescope. It uses the seven-beam focal plane feed array receiver system (ALFA) to carry out an imaging survey project of the 12,700 square degrees of sky visible from Arecibo at 1.4 GHz with 8192 spectral channels over a bandwidth of 300 MHz sampled at 1 millisecond. The aggregate data rate is 875 MB/s. GALFACTS observations will create full-Stokes image cubes at an angular resolution of 3.5' with a band-averaged sensitivity of 90 μJy, allowing sensitive imaging of polarized radiation and Faraday Rotation Measure from both diffuse emission and extragalactic sources. GALFACTS is a scientific pathfinder to the SKA in the area of cosmic magnetism. Key to magnetism science with the SKA is the technique of RM synthesis. The technique of RM synthesis is introduced and we discuss practical aspects of RM synthesis including efficient computational techniques and detection thresholds in the resulting Faraday spectrum. We illustrate the use of the technique by presenting the current development of the RM synthesis pipeline for GALFACTS and present early results.

  9. Investigation of static and dynamic behavior of functionally graded piezoelectric actuated Poly-Si micro cantilever probe

    SciTech Connect

    Pandey, Vibhuti Bhushan; Parashar, Sandeep Kumar

    2016-04-13

    In the present paper a novel functionally graded piezoelectric (FGP) actuated Poly-Si micro cantilever probe is proposed for atomic force microscope. The shear piezoelectric coefficient d{sub 15} has much higher value than coupling coefficients d{sub 31} and d{sub 33}, hence in the present work the micro cantilever beam actuated by d{sub 15} effect is utilized. The material properties are graded in the thickness direction of actuator by a simple power law. A three dimensional finite element analysis has been performed using COMSOL Multiphysics® (version 4.2) software. Tip deflection and free vibration analysis for the micro cantilever probe has been done. The results presented in the paper shall be useful in the design of micro cantilever probe and their subsequent utilization in atomic force microscopes.

  10. Investigation of change in surface morphology of heated surfaces upon pool boiling of magnetic fluids under magnetic actuation

    NASA Astrophysics Data System (ADS)

    Shojaeian, Mostafa; Yildizhan, Melike-Mercan; Coşkun, Ömer; Ozkalay, Ebrar; Tekşen, Yiğit; Gulgun, Mehmet Ali; Funda Yagci Acar, Havva; Koşar, Ali

    2016-09-01

    Nanofluids are becoming a significant candidate for new generation coolants to be used in industrial applications. In order to reduce clustering and sedimentation of nanoparticles and improve the heat transfer performance simultaneously, magnetic fluids prepared with magnetic Fe3O4 nanoparticles dispersed in water, which were placed in a pool and were exposed to varying magnetic fields to actuate nanoparticles in the system. The effect of magnetic actuation on boiling heat transfer characteristics and on the surface morphology of the pool was examined. An average enhancement of 29% in boiling heat transfer was achieved via magnetic actuation with rather low magnetic field (magnetic flux densities up to 11 mT) densities. Furthermore, it was observed that magnetic actuation significantly prevented the deposition and sedimentation of the nanoparticles in the pool. Otherwise, significant destabilization of nanoparticles causing aggregation and heavy sedimentation was present as a result of the performed surface analysis. Even though magnetic actuation reduced the sedimentation on the macroscale, the deposition of a thick and porous film occurred onto the pool floor, increasing the surface roughness.

  11. Refillable and magnetically actuated drug delivery system using pear-shaped viscoelastic membrane

    PubMed Central

    So, Hongyun; Seo, Young Ho; Pisano, Albert P.

    2014-01-01

    We report a refillable and valveless drug delivery device actuated by an external magnetic field for on-demand drug release to treat localized diseases. The device features a pear-shaped viscoelastic magnetic membrane inducing asymmetrical deflection and consecutive touchdown motion to the bottom of the dome-shaped drug reservoir in response to a magnetic field, thus achieving controlled discharge of the drug. Maximum drug release with 18 ± 1.5 μg per actuation was achieved under a 500 mT magnetic flux density, and various controlled drug doses were investigated with the combination of the number of accumulated actuations and the strength of the magnetic field. PMID:25379104

  12. Fabrication and Manipulation of Ciliary Microrobots with Non-reciprocal Magnetic Actuation

    PubMed Central

    Kim, Sangwon; Lee, Seungmin; Lee, Jeonghun; Nelson, Bradley J.; Zhang, Li; Choi, Hongsoo

    2016-01-01

    Magnetically actuated ciliary microrobots were designed, fabricated, and manipulated to mimic cilia-based microorganisms such as paramecia. Full three-dimensional (3D) microrobot structures were fabricated using 3D laser lithography to form a polymer base structure. A nickel/titanium bilayer was sputtered onto the cilia part of the microrobot to ensure magnetic actuation and biocompatibility. The microrobots were manipulated by an electromagnetic coil system, which generated a stepping magnetic field to actuate the cilia with non-reciprocal motion. The cilia beating motion produced a net propulsive force, resulting in movement of the microrobot. The magnetic forces on individual cilia were calculated with various input parameters including magnetic field strength, cilium length, applied field angle, actual cilium angle, etc., and the translational velocity was measured experimentally. The position and orientation of the ciliary microrobots were precisely controlled, and targeted particle transportation was demonstrated experimentally. PMID:27470077

  13. Probing fine magnetic particles with neutron scattering

    SciTech Connect

    Pynn, R.

    1991-12-31

    Because thermal neutrons are scattered both by nuclei and by unpaired electrons, they provide an ideal probe for studying the atomic and magnetic structures of fine-grained magnetic materials, including nanocrystalline solids, thin epitaxial layers, and colloidal suspensions of magnetic particles, known as ferrofluids. Diffraction, surface reflection, and small angle neutron scattering (SANS) are the techniques used. With the exception of surface reflection, these methods are described in this article. The combination of SANS with refractive-index matching and neutron polarisation analysis is particularly powerful because it allows the magnetic and atomic structures to be determined independently. This technique has been used to study both dilute and concentrated ferrofluid suspensions of relatively monodisperse cobalt particles, subjected to a series of applied magnetic fields. The size of the cobalt particle core and the surrounding surfactant layer were determined. The measured interparticle structure factor agrees well with a recent theory that allows correlations in binary mixtures of magnetic particles to be calculated in the case of complete magnetic alignment. When one of the species in such a binary mixture is a nonmagnetic, cyclindrical macromolecule, application of a magnetic field leads to some degree of alignment of the nonmagnetic species. This result has been demonstrated with tobacco mosaic virus suspended in a water-based ferrofluid.

  14. Probing fine magnetic particles with neutron scattering

    SciTech Connect

    Pynn, R.

    1991-01-01

    Because thermal neutrons are scattered both by nuclei and by unpaired electrons, they provide an ideal probe for studying the atomic and magnetic structures of fine-grained magnetic materials, including nanocrystalline solids, thin epitaxial layers, and colloidal suspensions of magnetic particles, known as ferrofluids. Diffraction, surface reflection, and small angle neutron scattering (SANS) are the techniques used. With the exception of surface reflection, these methods are described in this article. The combination of SANS with refractive-index matching and neutron polarisation analysis is particularly powerful because it allows the magnetic and atomic structures to be determined independently. This technique has been used to study both dilute and concentrated ferrofluid suspensions of relatively monodisperse cobalt particles, subjected to a series of applied magnetic fields. The size of the cobalt particle core and the surrounding surfactant layer were determined. The measured interparticle structure factor agrees well with a recent theory that allows correlations in binary mixtures of magnetic particles to be calculated in the case of complete magnetic alignment. When one of the species in such a binary mixture is a nonmagnetic, cyclindrical macromolecule, application of a magnetic field leads to some degree of alignment of the nonmagnetic species. This result has been demonstrated with tobacco mosaic virus suspended in a water-based ferrofluid.

  15. Influence of segmentation of ring-shaped NdFeB magnets with parallel magnetization on cylindrical actuators.

    PubMed

    Eckert, Paulo Roberto; Goltz, Evandro Claiton; Flores Filho, Aly Ferreira

    2014-07-21

    This work analyses the effects of segmentation followed by parallel magnetization of ring-shaped NdFeB permanent magnets used in slotless cylindrical linear actuators. The main purpose of the work is to evaluate the effects of that segmentation on the performance of the actuator and to present a general overview of the influence of parallel magnetization by varying the number of segments and comparing the results with ideal radially magnetized rings. The analysis is first performed by modelling mathematically the radial and circumferential components of magnetization for both radial and parallel magnetizations, followed by an analysis carried out by means of the 3D finite element method. Results obtained from the models are validated by measuring radial and tangential components of magnetic flux distribution in the air gap on a prototype which employs magnet rings with eight segments each with parallel magnetization. The axial force produced by the actuator was also measured and compared with the results obtained from numerical models. Although this analysis focused on a specific topology of cylindrical actuator, the observed effects on the topology could be extended to others in which surface-mounted permanent magnets are employed, including rotating electrical machines.

  16. Influence of Segmentation of Ring-Shaped NdFeB Magnets with Parallel Magnetization on Cylindrical Actuators

    PubMed Central

    Eckert, Paulo Roberto; Goltz, Evandro Claiton; Filho, Aly Ferreira Flores

    2014-01-01

    This work analyses the effects of segmentation followed by parallel magnetization of ring-shaped NdFeB permanent magnets used in slotless cylindrical linear actuators. The main purpose of the work is to evaluate the effects of that segmentation on the performance of the actuator and to present a general overview of the influence of parallel magnetization by varying the number of segments and comparing the results with ideal radially magnetized rings. The analysis is first performed by modelling mathematically the radial and circumferential components of magnetization for both radial and parallel magnetizations, followed by an analysis carried out by means of the 3D finite element method. Results obtained from the models are validated by measuring radial and tangential components of magnetic flux distribution in the air gap on a prototype which employs magnet rings with eight segments each with parallel magnetization. The axial force produced by the actuator was also measured and compared with the results obtained from numerical models. Although this analysis focused on a specific topology of cylindrical actuator, the observed effects on the topology could be extended to others in which surface-mounted permanent magnets are employed, including rotating electrical machines. PMID:25051032

  17. Towards nanomedicines of the future: Remote magneto-mechanical actuation of nanomedicines by alternating magnetic fields☆

    PubMed Central

    Golovin, Yuri I.; Gribanovsky, Sergey L.; Golovin, Dmitry Y.; Klyachko, Natalia L.; Majouga, Alexander G.; Master, Alyssa M.; Sokolsky, Marina; Kabanov, Alexander V.

    2015-01-01

    The paper describes the concept of magneto-mechanical actuation of single-domain magnetic nanoparticles (MNPs) in super-low and low frequency alternating magnetic fields (AMFs) and its possible use for remote control of nanomedicines and drug delivery systems. The applications of this approach for remote actuation of drug release as well as effects on biomacromolecules, biomembranes, subcellular structures and cells are discussed in comparison to conventional strategies employing magnetic hyperthermia in a radio frequency (RF) AMF. Several quantitative models describing interaction of functionalized MNPs with single macromolecules, lipid membranes, and proteins (e.g. cell membrane receptors, ion channels) are presented. The optimal characteristics of the MNPs and an AMF for effective magneto-mechanical actuation of single molecule responses in biological and bio-inspired systems are discussed. Altogether, the described studies and phenomena offer opportunities for the development of novel therapeutics both alone and in combination with magnetic hyperthermia. PMID:26407671

  18. Eversion of bistable shells under magnetic actuation: a model of nonlinear shapes

    NASA Astrophysics Data System (ADS)

    Seffen, Keith A.; Vidoli, Stefano

    2016-06-01

    We model in closed form a proven bistable shell made from a magnetic rubber composite material. In particular, we incorporate a non-axisymmetrical displacement field, and we capture the nonlinear coupling between the actuated shape and the magnetic flux distribution around the shell. We are able to verify the bistable nature of the shell and we explore its eversion during magnetic actuation. We show that axisymmetrical eversion is natural for a perfect shell but that non-axisymmetrical eversion rapidly emerges under very small initial imperfections, as observed in experiments and in a computational analysis. We confirm the non-uniform shapes of shell and we study the stability of eversion by considering how the landscape of total potential and magnetic energies of the system changes during actuation.

  19. Towards nanomedicines of the future: Remote magneto-mechanical actuation of nanomedicines by alternating magnetic fields.

    PubMed

    Golovin, Yuri I; Gribanovsky, Sergey L; Golovin, Dmitry Y; Klyachko, Natalia L; Majouga, Alexander G; Master, Аlyssa M; Sokolsky, Marina; Kabanov, Alexander V

    2015-12-10

    The paper describes the concept of magneto-mechanical actuation of single-domain magnetic nanoparticles (MNPs) in super-low and low frequency alternating magnetic fields (AMFs) and its possible use for remote control of nanomedicines and drug delivery systems. The applications of this approach for remote actuation of drug release as well as effects on biomacromolecules, biomembranes, subcellular structures and cells are discussed in comparison to conventional strategies employing magnetic hyperthermia in a radio frequency (RF) AMF. Several quantitative models describing interaction of functionalized MNPs with single macromolecules, lipid membranes, and proteins (e.g. cell membrane receptors, ion channels) are presented. The optimal characteristics of the MNPs and an AMF for effective magneto-mechanical actuation of single molecule responses in biological and bio-inspired systems are discussed. Altogether, the described studies and phenomena offer opportunities for the development of novel therapeutics both alone and in combination with magnetic hyperthermia.

  20. Measurement and calculation of forces in a magnetic journal bearing actuator

    NASA Technical Reports Server (NTRS)

    Knight, Josiah; Mccaul, Edward; Xia, Zule

    1991-01-01

    Numerical calculations and experimental measurements of forces from an actuator of the type used in active magnetic journal bearings are presented. The calculations are based on solution of the scalar magnetic potential field in and near the gap regions. The predicted forces from single magnet with steady current are compared with experimental measurements in the same geometry. The measured forces are smaller than calculated ones in the principal direction but are larger than calculated in the normal direction. This combination of results indicate that material and spatial effects other than saturation play roles in determining the force available from an actuator.

  1. Behavior of a Single Langmuir Probe in a Magnetic Field.

    ERIC Educational Resources Information Center

    Pytlinski, J. T.; And Others

    1978-01-01

    Describes an experiment to demonstrate the influence of a magnetic field on the behavior of a single Langmuir probe. The experiment introduces the student to magnetically supported plasma and particle behavior in a magnetic field. (GA)

  2. Magnetic resonance elastography using an air ball-actuator.

    PubMed

    Numano, Tomokazu; Kawabata, Yoshihiko; Mizuhara, Kazuyuki; Washio, Toshikatsu; Nitta, Naotaka; Homma, Kazuhiro

    2013-07-01

    The purpose of this study was to develop a new technique for a powerful compact MR elastography (MRE) actuator based on a pneumatic ball-vibrator. This is a compact actuator that generates powerful centrifugal force vibrations via high speed revolutions of an internal ball using compressed air. This equipment is easy to handle due to its simple principles and structure. Vibration frequency and centrifugal force are freely adjustable via air pressure changes (air flow volume), and replacement of the internal ball. In order to achieve MRI compatibility, all parts were constructed from non-ferromagnetic materials. Vibration amplitudes (displacements) were measured optically by a laser displacement sensor. From a bench test of displacement, even though the vibration frequency increased, the amount of displacement did not decrease. An essential step in MRE is the generation of mechanical waves within tissue via an actuator, and MRE sequences are synchronized to several phase offsets of vibration. In this system, the phase offset was detected by a four-channel optical-fiber sensor, and it was used as an MRI trigger signal. In an agarose gel phantom experiment, this actuator was used to make an MR elastogram. This study shows that the use of a ball actuator for MRE is feasible.

  3. Magnetic Actuators and Suspension for Space Vibration Control

    NASA Technical Reports Server (NTRS)

    Knospe, Carl R.; Allaire, Paul E.; Lewis, David W.

    1993-01-01

    The research on microgravity vibration isolation performed at the University of Virginia is summarized. This research on microgravity vibration isolation was focused in three areas: (1) the development of new actuators for use in microgravity isolation; (2) the design of controllers for multiple-degree-of-freedom active isolation; and (3) the construction of a single-degree-of-freedom test rig with umbilicals. Described are the design and testing of a large stroke linear actuator; the conceptual design and analysis of a redundant coarse-fine six-degree-of-freedom actuator; an investigation of the control issues of active microgravity isolation; a methodology for the design of multiple-degree-of-freedom isolation control systems using modern control theory; and the design and testing of a single-degree-of-freedom test rig with umbilicals.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  5. Characteristics of magnetic probes for identifying sentinel lymph nodes.

    PubMed

    Ookubo, Tetsu; Inoue, Yusuke; Kim, Dongmin; Ohsaki, Hiroyuki; Mashiko, Yusuke; Kusakabe, Moriaki; Sekino, Masaki

    2013-01-01

    The identification of the sentinel lymph nodes that cause tumor metastasis is important in breast cancer therapy. The detection of magnetic fluid accumulating in the lymph nodes using a magnetic probe allows surgeons to identify the lymph nodes. In this study, we carried out numerical simulations and experiments to investigate the sensitivity and basic characteristics of a magnetic probe consisting of a permanent magnet and a small magnetic sensor. The measured magnetic flux density arising from the magnetic fluid agreed well with the numerical results. In addition, the results helped realize an appropriate probe configuration for achieving high sensitivity to magnetic fluid. A prototype probe detected magnetic fluid located 30 mm from the probe head.

  6. Probing and manipulating magnetization at the nanoscale

    NASA Astrophysics Data System (ADS)

    Samarth, Nitin

    2012-02-01

    Combining semiconductors with magnetism in hetero- and nano-structured geometries provides a powerful means of exploring the interplay between spin-dependent transport and nanoscale magnetism. We describe two recent studies in this context. First, we use spin-dependent transport in ferromagnetic semiconductor thin films to provide a new window into nanoscale magnetism [1]: here, we exploit the large anomalous Hall effect in a ferromagnetic semiconductor as a nanoscale probe of the reversible elastic behavior of magnetic domain walls and gain insight into regimes of domain wall behavior inaccessible to more conventional optical techniques. Next, we describe novel ways to create self-assembled hybrid semiconductor/ferromagnet core-shell nanowires [2] and show how magnetoresistance measurements in single nanowires, coupled with micromagnetic simulations, can provide detailed insights into the magnetization reversal process in nanoscale ferromagnets [3]. The work described here was carried out in collaboration with Andrew Balk, Jing Liang, Nicholas Dellas, Mark Nowakowski, David Rench, Mark Wilson, Roman Engel-Herbert, Suzanne Mohney, Peter Schiffer and David Awschalom. This work is supported by ONR, NSF and the NSF-MRSEC program.[4pt] [1] A. L. Balk et al., Phys. Rev.Lett. 107, 077205 (2011).[0pt] [2] N. J. Dellas et al., Appl. Phys. Lett. 97, 072505 (2010).[0pt] [3] J. Liang et al., in preparation.

  7. Fabrication, characterization, and heuristic trade space exploration of magnetically actuated Miura-Ori origami structures

    NASA Astrophysics Data System (ADS)

    Cowan, Brett; von Lockette, Paris R.

    2017-04-01

    The authors develop magnetically actuated Miura-Ori structures through observation, experiment, and computation using an initially heuristic strategy followed by trade space visualization and optimization. The work is novel, especially within origami engineering, in that beyond final target shape approximation, Miura-Ori structures in this work are additionally evaluated for the shape approximation while folding and for their efficient use of their embedded actuators. The structures consisted of neodymium magnets placed on the panels of silicone elastomer substrates cast in the Miura-Ori folding pattern. Initially four configurations, arrangements of magnets on the panels, were selected based on heuristic arguments that (1) maximized the amount of magnetic torque applied to the creases and (2) reduced the number of magnets needed to affect all creases in the pattern. The results of experimental and computational performance metrics were used in a weighted sum model to predict the optimum configuration, which was then fabricated and experimentally characterized for comparison to the initial prototypes. As expected, optimization of magnet placement and orientation was effective at increasing the degree of theoretical useful work. Somewhat unexpectedly, however, trade space results showed that even after optimization, the configuration with the most number of magnets was least effective, per magnet, at directing its actuation to the structure’s creases. Overall, though the winning configuration experimentally outperformed its initial, non-optimal counterparts, results showed that the choice of optimum configuration was heavily dependent on the weighting factors. These results highlight both the ability of the Miura-Ori to be actuated with external magnetic stimuli, the effectiveness of a heuristic design approach that focuses on the actuation mechanism, and the need to address path-dependent metrics in assessing performance in origami folding structures.

  8. Microfabricated magnetic structures for future medicine: from sensors to cell actuators.

    PubMed

    Vitol, Elina A; Novosad, Valentyn; Rozhkova, Elena A

    2012-10-01

    In this review, we discuss the prospective medical application of magnetic carriers microfabricated by top-down techniques. Physical methods allow the fabrication of a variety of magnetic structures with tightly controlled magnetic properties and geometry, which makes them very attractive for a cost-efficient mass-production in the fast growing field of nanomedicine. Stand-alone fabricated particles along with integrated devices combining lithographically defined magnetic structures and synthesized magnetic tags will be considered. Applications of microfabricated multifunctional magnetic structures for future medicinal purposes range from ultrasensitive in vitro diagnostic bioassays, DNA sequencing and microfluidic cell sorting to magnetomechanical actuation, cargo delivery, contrast enhancement and heating therapy.

  9. Microfabricated magnetic structures for future medicine: from sensors to cell actuators

    PubMed Central

    Vitol, Elina A; Novosad, Valentyn; Rozhkova, Elena A

    2013-01-01

    In this review, we discuss the prospective medical application of magnetic carriers microfabricated by top-down techniques. Physical methods allow the fabrication of a variety of magnetic structures with tightly controlled magnetic properties and geometry, which makes them very attractive for a cost-efficient mass-production in the fast growing field of nanomedicine. Stand-alone fabricated particles along with integrated devices combining lithographically defined magnetic structures and synthesized magnetic tags will be considered. Applications of microfabricated multifunctional magnetic structures for future medicinal purposes range from ultrasensitive in vitro diagnostic bioassays, DNA sequencing and microfluidic cell sorting to magnetomechanical actuation, cargo delivery, contrast enhancement and heating therapy. PMID:23148542

  10. Hysteresis modeling of magnetic shape memory alloy actuator based on Krasnosel'skii-Pokrovskii model.

    PubMed

    Zhou, Miaolei; Wang, Shoubin; Gao, Wei

    2013-01-01

    As a new type of intelligent material, magnetically shape memory alloy (MSMA) has a good performance in its applications in the actuator manufacturing. Compared with traditional actuators, MSMA actuator has the advantages as fast response and large deformation; however, the hysteresis nonlinearity of the MSMA actuator restricts its further improving of control precision. In this paper, an improved Krasnosel'skii-Pokrovskii (KP) model is used to establish the hysteresis model of MSMA actuator. To identify the weighting parameters of the KP operators, an improved gradient correction algorithm and a variable step-size recursive least square estimation algorithm are proposed in this paper. In order to demonstrate the validity of the proposed modeling approach, simulation experiments are performed, simulations with improved gradient correction algorithm and variable step-size recursive least square estimation algorithm are studied, respectively. Simulation results of both identification algorithms demonstrate that the proposed modeling approach in this paper can establish an effective and accurate hysteresis model for MSMA actuator, and it provides a foundation for improving the control precision of MSMA actuator.

  11. Linearization of the response of a 91-actuator magnetic liquid deformable mirror.

    PubMed

    Brousseau, Denis; Borra, Ermanno F; Rochette, Maxime; Landry, Daniel Bouffard

    2010-04-12

    We present the experimental performance of a 91-actuator deformable mirror made of a magnetic liquid (ferrofluid) using a new technique that linearizes the response of the mirror by superposing a uniform magnetic field to the one produced by the actuators. We demonstrate linear driving of the mirror using influence functions, measured with a Fizeau interferometer, by producing the first 36 Zernikes polynomials. Based on our measurements, we predict achievable mean PV wavefront amplitudes of up to 30 microm having RMS residuals of lambda/10 at 632.8 nm. Linear combination of Zernikes and over-time repeatability are also demonstrated.

  12. Progesterone-Targeted Magnetic Resonance Imaging Probes

    PubMed Central

    2015-01-01

    Determination of progesterone receptor (PR) status in hormone-dependent diseases is essential in ascertaining disease prognosis and monitoring treatment response. The development of a noninvasive means of monitoring these processes would have significant impact on early detection, cost, repeated measurements, and personalized treatment options. Magnetic resonance imaging (MRI) is widely recognized as a technique that can produce longitudinal studies, and PR-targeted MR probes may address a clinical problem by providing contrast enhancement that reports on PR status without biopsy. Commercially available MR contrast agents are typically delivered via intravenous injection, whereas steroids are administered subcutaneously. Whether the route of delivery is important for tissue accumulation of steroid-modified MRI contrast agents to PR-rich tissues is not known. To address this question, modification of the chemistry linking progesterone with the gadolinium chelate led to MR probes with increased water solubility and lower cellular toxicity and enabled administration through the blood. This attribute came at a cost through lower affinity for PR and decreased ability to cross the cell membrane, and ultimately it did not improve delivery of the PR-targeted MR probe to PR-rich tissues or tumors in vivo. Overall, these studies are important, as they demonstrate that targeted contrast agents require optimization of delivery and receptor binding of the steroid and the gadolinium chelate for optimal translation in vivo. PMID:25019183

  13. Fundamentals of magnet-actuated droplet manipulation on an open hydrophobic surface†

    PubMed Central

    Long, Zhicheng; Shetty, Abhishek M.; Solomon, Michael J.; Larson, Ronald G.

    2010-01-01

    We systematically investigate droplet movement, coalescence, and splitting on an open hydrophobic surface. These processes are actuated by magnetic beads internalized in an oil-coated aqueous droplet using an external magnet. Results are organized into an ‘operating diagram’ that describes regions of droplet stable motion, breakage, and release from the magnet. The results are explained theoretically with a simple model that balances magnetic, friction, and capillary-induced drag forces and includes the effects of particle type, droplet size, surrounding oil layer, surface tension, and viscosity. Finally, we discuss the implications of the results for the design of magnet-actuated droplet systems for applications such as nucleic acid purification, immunoassay and drug delivery. PMID:19458864

  14. Evaluation of magnetic resonance imaging issues for implantable microfabricated magnetic actuators.

    PubMed

    Lee, Hyowon; Xu, Qing; Shellock, Frank G; Bergsneider, Marvin; Judy, Jack W

    2014-02-01

    The mechanical robustness of microfabricated torsional magnetic actuators in withstanding the strong static fields (7 T) and time-varying field gradients (17 T/m) produced by an MR system was studied in this investigation. The static and dynamic mechanical characteristics of 30 devices were quantitatively measured before and after exposure to both strong uniform and non-uniform magnetic fields. The results showed no statistically significant change in both the static and dynamic mechanical performance, which mitigate concerns about the mechanical stability of these devices in association with MR systems under the conditions used for this assessment. The MR-induced heating was also measured in a 3-T/128-MHz MR system. The results showed a minimal increase (1.6 °C) in temperature due to the presence of the magnetic microactuator array. Finally, the size of the MR-image artifacts created by the magnetic microdevices were quantified. The signal loss caused by the devices was approximately four times greater than the size of the device.

  15. Attitude dynamics of gyrostat-satellites under control by magnetic actuators at small perturbations

    NASA Astrophysics Data System (ADS)

    Doroshin, Anton V.

    2017-08-01

    The angular motion of gyrostat-satellites with one axial rotor is considered under control by magnetic actuators and at the action of small polyharmonic perturbations of the own dipole magnetic moment's components which are created proportionally to components of the angular velocity of the satellite. The attitude dynamics is investigated in conditions of the coincidence of the vector of magnetic induction of the external magnetic field and the initial angular momentum vector of the satellite. General and heteroclinic analytical solutions are obtained for dynamical parameters at the relative smallness of the magnetic torques. The chaotic regimes are examined on the base of the Melnikov method and Poincaré sections.

  16. MRI Compatibility of Microfabricated Magnetic Actuators for Implantable Catheters: Mechanical Evaluations

    PubMed Central

    Lee, Hyowon; Xu, Qing; Ephrati, Jeremy; Bergsneider, Marvin; Judy, Jack W.

    2017-01-01

    Here we demonstrate the mechanical robustness of microfabricated torsional magnetic actuators in withstanding the magnetic fields produced by a 7 T MRI magnet. The static and dynamic mechanical characteristics of 30 devices were quantitatively measured before and after exposure to both uniform and non-uniform magnetic fields. The results show no statistically significant change in both the static and dynamic mechanical performance, which mitigates concerns about the mechanical compatibility of our devices with MRI scanners. Additional experiments are required to quantify the potential image-artifact size and radio-frequency-induced heating caused by the magnetic microactuators inside an MRI scanner. PMID:21096979

  17. Development of magnetic shape memory alloy actuators for a swashplateless helicopter rotor

    NASA Astrophysics Data System (ADS)

    Couch, Ronald Newton

    Actuator concepts utilizing NiMnGa, ferromagnetic shape memory alloy are investigated for potential use on a smart rotor for trailing edge flap actuation. With their high energy density, large dynamic stroke, and wide operating bandwidth, ferromagnetic shape memory alloys (FSMA) like NiMnGa, seem like attractive candidates for smart rotor actuators, potentially able to fulfill the requirements for both primary rotor control and vibration suppression. However, because of the recent discovery of the material, current experimental data and analytical tools are limited. To rectify these shortcomings, an extensive set of detailed experiments were conducted on samples of NiMnGa to characterize the response of the alloy for a wide variety of mechanical and magnetic loading conditions. Measurements of the material performance parameters such as power density, damping properties, magneto-mechanical coupling, and transduction efficiency were included. Once characterized, the experimental data were used to develop a series of analytical tools to predict the behavior of the material. A model, developed in parallel to thermal shape memory alloy models is proposed to predict the quasi-static stress-strain behavior. A simple, low frequency, parameter based model was also developed to predict the alloy's dynamic strain response. A method for developing conceptual actuators utilizing NiMnGa as the actuation element was proposed. This approach incorporates experimental data into a process that down-selects a series of possible actuator configurations to obtain a single configuration optimized for volumetric and weight considerations. The proposed actuator was designed to deliver 2 mm of stroke and 60 N of force at an actuation frequency of 50 Hz. However, to generate the 1.0 T magnetic field, the actuator mass was determined to be 2.8 kg and required a minimum of 320 Watts of power for operation. The mass of the NiMnGa element was only 18.3 g. It was concluded that although the Ni

  18. Magnetic-probe diagnostics for railgun plasma armatures

    SciTech Connect

    Parker, J.V.

    1989-06-01

    Magnetic probes were employed on the first plasma armature railgun experiments, and they have been used continuously since then for position determination and qualitative determination of the armature current. In the last few years, improvements in experimental technique and analysis have permitted more accurate measurements of the plasma-armature current distribution. This paper reviews the various probe configurations in use today and presents analytic approximations for the dependence of the probe signal on probe location and railgun geometry. Rail current and armature current probes are compared and contrasted with respect to resolution and accuracy. Further improvements in measurement accuracy are predicted for close-spaced magnetic-probe arrays.

  19. Wireless actuation of piezoelectric coupled micromembrane using radio frequency magnetic field for biomedical applications

    NASA Astrophysics Data System (ADS)

    Sinha, Dhiraj

    2017-04-01

    We report on a novel technique of wireless actuation of a micromembrane mounted on a piezoelectric stack using radio frequency magnetic fields. The magnetic field component of the radio frequency field induces time varying voltage across the leads of the piezoelectric stack which results in vibrations of the piezoelectric stack which are eventually transferred to a micromembrane of silicon nitride mounted on top of it. Thus, wireless actuation of micromembranes is achieved which is measured using a laser-photodetector system. Wireless actuation of micromembranes has applications in controlled drug delivery with rates of the order of tens of nanolitres per second. It can also be used in controlling capsule endoscopes, in vivo sensors, and micromachines for biomedical applications.

  20. MTRAP: The Magnetic Transition Region Probe

    NASA Technical Reports Server (NTRS)

    Davis, J. M.; West, E. A.; Moore, R. L.; Gary, G. A.; Kobayashi, K.; Oberright, J. F.; Evans, D. C.; Wood, H. J.; Saba, J. L. R.; Alexander, D.

    2005-01-01

    The Magnetic Transition Region Probe is a space telescope designed to measure the magnetic field at several heights and temperatures in the solar atmosphere, providing observations spanning the chromospheric region where the field is expected to become force free. The primary goal is to provide an early warning system (hours to days) for solar energetic particle events that pose a serious hazard to astronauts in deep space and to understand the source regions of these particles. The required magnetic field data consist of simultaneous circular and linear polarization measurements in several spectral lines over the wavelength range from 150 to 855 nm. Because the observations are photon limited an optical telescope with a large (>18sq m) collecting area is required. To keep the heat dissipation problem manageable we have chosen to implement MTRAP with six separate Gregorian telescopes, each with approx. 3 sq m collecting area, that are brought to a common focus. The large field of view (5 x 5 arcmin(sup 2)) and angular resolution (0.025 arcsec pixels) require large detector arrays and, because of the requirements on signal to noise (10(exp 3)), pixels with large full well depths to reduce the readout time and improve the temporal resolution. The optical and engineering considerations that have gone into the development of a concept that meets MTRAP's requirements are described.

  1. Heat transfer enhancement with actuation of magnetic nanoparticles suspended in a base fluid

    NASA Astrophysics Data System (ADS)

    Şeşen, Muhsincan; Tekşen, Yiǧit; Şendur, Kürşat; Pınar Mengüç, M.; Öztürk, Hande; Yaǧcı Acar, H. F.; Koşar, Ali

    2012-09-01

    In this study, we have experimentally demonstrated that heat transfer can be substantially increased by actuating magnetic nanoparticles inside a nanofluid. In order to materialize this, we have utilized a miniature heat transfer enhancement system based on the actuation of magnetic nanoparticles dispersed in a base fluid (water). This compact system consists of a pool filled with a nanofluid containing ferromagnetic nanoparticles, a heater, and two magnetic stirrers. The ferromagnetic particles within the pool were actuated with the magnetic stirrers. Single-phase heat transfer characteristics of the system were investigated at various fixed heat fluxes and were compared to those of stationary nanofluid (without magnetic stirring). The heat transfer enhancement realized by the circulation of ferromagnetic nanoparticles dispersed in a nanofluid was studied using the experimental setup. The temperatures were recorded from the readings of thin thermocouples, which were integrated to the heater surface. The surface temperatures were monitored against the input heat flux and data were processed to compare the heat transfer results of the configuration with magnetic stirrers to the heat transfer of the configuration without the magnetic stirrers.

  2. A Comparison of Analytical and Experimental Data for a Magnetic Actuator

    NASA Technical Reports Server (NTRS)

    Groom, Nelson J.; Bloodgood, V. Dale, Jr.

    2000-01-01

    Theoretical and experimental force-displacement and force-current data are compared for two configurations of a simple horseshoe, or bipolar, magnetic actuator. One configuration utilizes permanent magnet wafers to provide a bias flux and the other configuration has no source of bias flux. The theoretical data are obtained from two analytical models of each configuration. One is an ideal analytical model which is developed under the following assumptions: (1) zero fringing and leakage flux, (2) zero actuator coil mmf loss, and (3) infinite permeability of the actuator core and suspended element flux return path. The other analytical model, called the extended model, is developed by adding loss and leakage factors to the ideal model. The values of the loss and leakage factors are calculated from experimental data. The experimental data are obtained from a magnetic actuator test fixture, which is described in detail. Results indicate that the ideal models for both configurations do not match the experimental data very well. However, except for the range around zero force, the extended models produce a good match. The best match is produced by the extended model of the configuration with permanent magnet flux bias.

  3. Analysis of the giant magnetostrictive actuator with strong bias magnetic field

    NASA Astrophysics Data System (ADS)

    Xue, Guangming; He, Zhongbo; Li, Dongwei; Yang, Zhaoshu; Zhao, Zhenglong

    2015-11-01

    Giant magnetostrictive actuator with strong bias magnetic field is designed to control the injector bullet valve opening and closing. The relationship between actuator displacement amplitude and input signal direction is analyzed. And based on the approximate linearity of strain-magnetic field, second-order system model of the actuator displacement is established. Experimental system suitable for the actuator is designed. The experimental results show that, the square voltage amplitude being 12 V, the actuator displacement amplitude is about 17 μm with backward direction signal input while being 1.5 μm under forward direction signal. From the results, the suitable input direction is confirmed to be backward. With exciting frequncy lower than 200 Hz, the error between the model and experimental result is less than 1.7 μm. So the model is validated under the low-frequency signal input. The testing displacement-voltage curves are approximately straight lines. But due to the biased position, the line slope and the displacement-voltage linearity change as the input voltage changes.

  4. Wireless steering mechanism with magnetic actuation for an endoscopic capsule.

    PubMed

    Menciassi, A; Valdastri, P; Quaglia, C; Buselli, E; Dario, P

    2009-01-01

    This paper illustrates the design, development and testing of a miniature mechanism to be integrated in endoscopic capsules for precise steering capabilities (Magnetic Internal Mechanism, MIM). The mechanism consists of an electromagnetic motor connected to a couple of small permanent magnets and immersed in a static magnetic field produced by an external permanent magnet or a by an electromagnetic coil. The overall steering capsule, integrating the magnetic steering mechanism and the vision system is 15.6 mm in diameter, 48 mm in length, 14.4 g in weight and can be oriented with an accuracy of 0.01 degrees . As regards system scalability, the capsule size could be reduced down to 11 mm in diameter by optimizing some mechanical components. On the other hand, the magnets size cannot be reduced because the magnetic link between internal and external magnets at typical operation distances (about 15 mm) would be weak.

  5. Bunker probe: A plasma potential probe almost insensitive to its orientation with the magnetic field

    SciTech Connect

    Costea, S. Schneider, B. S.; Schrittwieser, R.; Ionita, C.; Fonda, B.; Kovačič, J.; Gyergyek, T.

    2016-05-15

    Due to their ability to suppress a large part of the electron current and thus measuring directly the plasma potential, ion sensitive probes have begun to be widely tested and used in fusion devices. For these probes to work, almost perfect alignment with the total magnetic field is necessary. This condition cannot always be fulfilled due to the curvature of magnetic fields, complex magnetic structure, or magnetic field reconnection. In this perspective, we have developed a plasma potential probe (named Bunker probe) based on the principle of the ion sensitive probe but almost insensitive to its orientation with the total magnetic field. Therefore it can be used to measure the plasma potential inside fusion devices, especially in regions with complex magnetic field topology. Experimental results are presented and compared with Ball-Pen probe measurements taken under identical conditions. We have observed that the floating potential of the Bunker probe is indeed little affected by its orientation with the magnetic field for angles ranging from 90° to 30°, in contrast to the Ball-Pen probe whose floating potential decreases towards that of a Langmuir probe if not properly aligned with the magnetic field.

  6. Measurement method for determining the magnetic hysteresis effects of reluctance actuators by evaluation of the force and flux variation

    NASA Astrophysics Data System (ADS)

    Vrijsen, N. H.; Jansen, J. W.; Compter, J. C.; Lomonova, E. A.

    2013-07-01

    A measurement method is presented which identifies the magnetic hysteresis effects present in the force of linear reluctance actuators. The measurement method is applied to determine the magnetic hysteresis in the force of an E-core reluctance actuator, with and without pre-biasing permanent magnet. The force measurements are conducted with a piezoelectric load cell (Kistler type 9272). This high-bandwidth force measurement instrument is identified in the frequency domain using a voice-coil actuator that has negligible magnetic hysteresis and eddy currents. Specifically, the phase delay between the current and force of the voice-coil actuator is used for the calibration of the measurement instrument. This phase delay is also obtained by evaluation of the measured force and flux variation in the E-core actuator, both with and without permanent magnet on the middle tooth. The measured magnetic flux variation is used to distinguish the phase delay due to magnetic hysteresis from the measured phase delay between the current and the force of the E-core actuator. Finally, an open loop steady-state ac model is presented that predicts the magnetic hysteresis effects in the force of the E-core actuator.

  7. Measurement method for determining the magnetic hysteresis effects of reluctance actuators by evaluation of the force and flux variation.

    PubMed

    Vrijsen, N H; Jansen, J W; Compter, J C; Lomonova, E A

    2013-07-01

    A measurement method is presented which identifies the magnetic hysteresis effects present in the force of linear reluctance actuators. The measurement method is applied to determine the magnetic hysteresis in the force of an E-core reluctance actuator, with and without pre-biasing permanent magnet. The force measurements are conducted with a piezoelectric load cell (Kistler type 9272). This high-bandwidth force measurement instrument is identified in the frequency domain using a voice-coil actuator that has negligible magnetic hysteresis and eddy currents. Specifically, the phase delay between the current and force of the voice-coil actuator is used for the calibration of the measurement instrument. This phase delay is also obtained by evaluation of the measured force and flux variation in the E-core actuator, both with and without permanent magnet on the middle tooth. The measured magnetic flux variation is used to distinguish the phase delay due to magnetic hysteresis from the measured phase delay between the current and the force of the E-core actuator. Finally, an open loop steady-state ac model is presented that predicts the magnetic hysteresis effects in the force of the E-core actuator.

  8. Spin Polarized Electron Probes and Magnetic Nanostructures

    SciTech Connect

    D.L. Mills

    2003-10-15

    OAK B188 This report summarizes progress to date in our theoretical research program, for the period from July 1, 2002 to November 1, 2003. In addition, our research priorities for the coming year are set forth. The reporting period has been a most exciting and significant one. For the past several years, one of our principal thrust areas has been development of the theory of spin dynamics in magnetic nanostructures with emphasis on the use of spin polarized electrons as probes of short wavelength spin dynamics in such entities. Our program stimulated the first experiment which detected large wave vector spin waves in ultrathin films in 1999 through spin polarized electron loss spectroscopy (SPEELS); the publication which announced this discovery was a joint publication between a group in Halle (Germany) with our theory effort. The continued collaboration has led to the design and implementation of the new SPEELS spectrometer and we now have in hand the first detailed measurements of spin wave dispersion in an ultrathin film. A second such spectrometer is now operational in the laboratory of Prof. H. Hopster, at UC Irvine. We are thus entering a most exciting new era in the spectroscopy of spin excitations in magnetic nanostructures. During the reporting period, we have completed very important new analyses which predict key aspects of the spectra which will be uncovered by these new instruments, and the calculations continue to be developed and to expand our understanding. In addition, we have initiated a new series of theoretical studies directed toward spin dynamics of single magnetic adatoms on metal surfaces, with STM based studies of this area n mind. In the near future, these studies will continue, and we will expand our effort into new areas of spin dynamics in magnetic nanostructures.

  9. Microscale flow propulsion through bioinspired and magnetically actuated artificial cilia.

    PubMed

    Chen, Chia-Yuan; Cheng, Ling-Ying; Hsu, Chun-Chieh; Mani, Karthick

    2015-05-01

    Recent advances in microscale flow propulsion through bioinspired artificial cilia provide a promising alternative for lab-on-a-chip applications. However, the ability of actuating artificial cilia to achieve a time-dependent local flow control with high accuracy together with the elegance of full integration into the biocompatible microfluidic platforms remains remote. Driven by this motive, the current work has constructed a series of artificial cilia inside a microchannel to facilitate the time-dependent flow propulsion through artificial cilia actuation with high-speed (>40 Hz) circular beating behavior. The generated flow was quantified using micro-particle image velocimetry and particle tracking with instantaneous net flow velocity of up to 10(1 ) μm/s. Induced flow patterns caused by the tilted conical motion of artificial cilia constitutes efficient fluid propulsion at microscale. This flow phenomenon was further measured and illustrated by examining the induced flow behavior across the depth of the microchannel to provide a global view of the underlying flow propulsion mechanism. The presented analytic paradigms and substantial flow evidence present novel insights into the area of flow manipulation at microscale.

  10. Microscale flow propulsion through bioinspired and magnetically actuated artificial cilia

    PubMed Central

    Chen, Chia-Yuan; Cheng, Ling-Ying; Hsu, Chun-Chieh; Mani, Karthick

    2015-01-01

    Recent advances in microscale flow propulsion through bioinspired artificial cilia provide a promising alternative for lab-on-a-chip applications. However, the ability of actuating artificial cilia to achieve a time-dependent local flow control with high accuracy together with the elegance of full integration into the biocompatible microfluidic platforms remains remote. Driven by this motive, the current work has constructed a series of artificial cilia inside a microchannel to facilitate the time-dependent flow propulsion through artificial cilia actuation with high-speed (>40 Hz) circular beating behavior. The generated flow was quantified using micro-particle image velocimetry and particle tracking with instantaneous net flow velocity of up to 101 μm/s. Induced flow patterns caused by the tilted conical motion of artificial cilia constitutes efficient fluid propulsion at microscale. This flow phenomenon was further measured and illustrated by examining the induced flow behavior across the depth of the microchannel to provide a global view of the underlying flow propulsion mechanism. The presented analytic paradigms and substantial flow evidence present novel insights into the area of flow manipulation at microscale. PMID:26045730

  11. A Cryogenic Magnetostrictive Actuator Using a Persistent High Temperature Superconducting Magnet. Part 1; Concept and Design

    NASA Technical Reports Server (NTRS)

    Horner, Garnett; Bromberg, Leslie; Teter, J. P.

    2000-01-01

    Cryogenic magnetostrictive materials, such as rare earth zinc crystals, offer high strains and high forces with minimally applied magnetic fields, making the material ideally suited for deformable optics applications. For cryogenic temperature applications the use of superconducting magnets offer the possibility of a persistent mode of operation, i.e., the magnetostrictive material will maintain a strain field without power. High temperature superconductors (HTS) are attractive options if the temperature of operation is higher than 10 degrees Kelvin (K) and below 77 K. However, HTS wires have constraints that limit the minimum radius of winding, and even if good wires can be produced, the technology for joining superconducting wires does not exist. In this paper, the design and capabilities of a rare earth zinc magnetostrictive actuator using bulk HTS is described. Bulk superconductors can be fabricated in the sizes required with excellent superconducting properties. Equivalent permanent magnets, made with this inexpensive material, are persistent, do not require a persistent switch as in HTS wires, and can be made very small. These devices are charged using a technique which is similar to the one used for charging permanent magnets, e.g., by driving them into saturation. A small normal conducting coil can be used for charging or discharging. Because of the magnetic field capability of the superconductor material, a very small amount of superconducting magnet material is needed to actuate the rare earth zinc. In this paper, several designs of actuators using YBCO and BSCCO 2212 superconducting materials are presented. Designs that include magnetic shielding to prevent interaction between adjacent actuators will also be described. Preliminary experimental results and comparison with theory for BSCCO 2212 with a magnetostrictive element will be discussed.

  12. A Hybrid Extended Kalman Filter as an Observer for a Pot-Electro-Magnetic Actuator

    NASA Astrophysics Data System (ADS)

    Schmidt, Simon; Mercorelli, Paolo

    2017-01-01

    This paper deals with an application in which a hybrid extended Kalman Filter (HEKF) is used to estimate state variables in a U-shaped electro-magnetic actuator to be used in mechanical systems. In this context a hybrid Kalman Filter is the one which switches between different models. The paper proposes a hybrid model for an extended Kalman Filter to be used as an observer to estimate the state and to control the force of the actuator. Applications include position, velocity and force control in automotive, engine and manufacturing systems. This work is focused on the estimation of state variables of the actuator. Simulated results show the effectiveness of the proposed approach.

  13. Mechanical Actuation of Magnetic Domain-Wall Motion

    NASA Astrophysics Data System (ADS)

    Kim, Se Kwon; Hill, Daniel; Tserkovnyak, Yaroslav

    2016-12-01

    We theoretically study the motion of a magnetic domain wall induced by transverse elastic waves in a one-dimensional magnetic wire, which respects both rotational and translational symmetries. By invoking the conservation of the associated total angular and linear momenta, we are able to derive the torque and the force on the domain wall exerted by the waves. We then show how ferromagnetic and antiferromagnetic domain walls can be driven by circularly and linearly polarized waves, respectively. We envision that elastic waves may provide effective means to drive the dynamics of magnetic solitons in insulators.

  14. Design considerations for an air core magnetic actuator

    NASA Technical Reports Server (NTRS)

    Groom, Nelson J.

    1992-01-01

    Equations for the force produced by an air core electromagnet on a permanent magnet core as a function of the coil height, coil inner and outer radii, and core displacement are developed. The magnetization vector of the permanent magnet core is assumed to be aligned with the central axis of the electromagnet and the forces which are produced lie along the same axis. Variations in force due to changes in electromagnet parameters and core displacement are investigated and parameter plots which should be useful for coil design are presented.

  15. Patterned magnetic traps for magnetophoretic assembly and actuation of microrotor pumps

    NASA Astrophysics Data System (ADS)

    Henighan, T.; Giglio, D.; Chen, A.; Vieira, G.; Sooryakumar, R.

    2011-03-01

    We demonstrate a microscopic magnetic rotor pump for fluidic channels whose components are assembled in situ and powered by weak external magnetic fields (<150 Oe). A platform of patterned Permalloy microdisks and microcavities provided for the transport, trapping, and rotation of the superparamagnetic spherical microrotors. Parallel actuation of several rotors without direct physical link to external energy sources, tunable rotation speeds, and reversible drive torques offers significant advantages over macroscopic techniques to control flow within microfluidic devices. The effectiveness of trapping and transporting magnetic nanoparticles by the disks illustrate scalability to smaller, submicrometer sized devices.

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

    PubMed

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

    2014-10-24

    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.

  17. Apparatus comprising magnetically actuated valves and uses thereof

    DOEpatents

    Edwards, Thayne L.; Harper, Jason C.

    2016-07-12

    The present invention, in part, relates to an apparatus having a single-use, normally-closed fluidic valve that is initially maintained in the closed position by a valve element bonded to an adhesive coating. The valve is opened using a magnetic force. The valve element includes a magnetic material or metal. In some examples, the valve is opened by bringing a magnet in proximity to the valve element to provide a magnetic force that delaminates the valve element from the adhesive coating. In particular, the apparatus can be useful for on-chip amplification and/or detection of various targets, including biological targets and any amplifiable targets. Such apparatuses and methods are useful for in-field or real-time detection of targets, especially in limited resource settings.

  18. Design, modelling and control of a micro-positioning actuator based on magnetic shape memory alloys

    NASA Astrophysics Data System (ADS)

    Minorowicz, Bartosz; Leonetti, Giuseppe; Stefanski, Frederik; Binetti, Giulio; Naso, David

    2016-07-01

    This paper presents an actuator based on magnetic shape memory alloys (MSMAs) suitable for precise positioning in a wide range (up to 1 mm). The actuator is based on the spring returned operating mode and uses a Smalley wave spring to maintain the same operating parameters of a classical coil spring, while being characterized by a smaller dimension. The MSMA element inside the actuator provides a deformation when excited by an external magnetic field, but its behavior is characterized by an asymmetric and saturated hysteresis. Thus, two models are exploited in this work to represent such a non-linear behavior, i.e., the modified and generalized Prandtl-Ishlinskii models. These models are particularly suitable for control purposes due to the existence of their analytical inversion that can be easily exploited in real time control systems. To this aim, this paper investigates three closed-loop control strategies, namely a classical PID regulator, a PID regulator with direct hysteresis compensation, and a combined PID and feedforward compensation strategy. The effectiveness of both modelling and control strategies applied to the designed MSMA-based actuator is illustrated by means of experimental results.

  19. Magnetically-actuated artificial cilia for microfluidic propulsion.

    PubMed

    Khaderi, S N; Craus, C B; Hussong, J; Schorr, N; Belardi, J; Westerweel, J; Prucker, O; Rühe, J; den Toonder, J M J; Onck, P R

    2011-06-21

    In this paper we quantitatively analyse the performance of magnetically-driven artificial cilia for lab-on-a-chip applications. The artificial cilia are fabricated using thin polymer films with embedded magnetic nano-particles and their deformation is studied under different external magnetic fields and flows. A coupled magneto-mechanical solid-fluid model that accurately captures the interaction between the magnetic field, cilia and fluid is used to simulate the cilia motion. The elastic and magnetic properties of the cilia are obtained by fitting the results of the computational model to the experimental data. The performance of the artificial cilia with a non-uniform cross-section is characterised using the numerical model for two channel configurations that are of practical importance: an open-loop and a closed-loop channel. We predict that the flow and pressure head generated by the artificial cilia can be as high as 18 microlitres per minute and 3 mm of water, respectively. We also study the effect of metachronal waves on the flow generated and show that the fluid propelled increases drastically compared to synchronously beating cilia, and is unidirectional. This increase is significant even when the phase difference between adjacent cilia is small. The obtained results provide guidelines for the optimal design of magnetically-driven artificial cilia for microfluidic propulsion.

  20. A low-cost, high-field-strength magnetic resonance imaging-compatible actuator.

    PubMed

    Secoli, Riccardo; Robinson, Matthew; Brugnoli, Michele; Rodriguez y Baena, Ferdinando

    2015-03-01

    To perform minimally invasive surgical interventions with the aid of robotic systems within a magnetic resonance imaging scanner offers significant advantages compared to conventional surgery. However, despite the numerous exciting potential applications of this technology, the introduction of magnetic resonance imaging-compatible robotics has been hampered by safety, reliability and cost concerns: the robots should not be attracted by the strong magnetic field of the scanner and should operate reliably in the field without causing distortion to the scan data. Development of non-conventional sensors and/or actuators is thus required to meet these strict operational and safety requirements. These demands commonly result in expensive actuators, which mean that cost effectiveness remains a major challenge for such robotic systems. This work presents a low-cost, high-field-strength magnetic resonance imaging-compatible actuator: a pneumatic stepper motor which is controllable in open loop or closed loop, along with a rotary encoder, both fully manufactured in plastic, which are shown to perform reliably via a set of in vitro trials while generating negligible artifacts when imaged within a standard clinical scanner.

  1. Development of transient internal probe (TIP) magnetic field diagnostic

    SciTech Connect

    Galambos, J.P.; Bohnet, M.A.; Jarboe, T.R.; Mattick, A.T.

    1994-12-31

    The Transient Internal Probe (TIP) is designed to permit measurement of internal magnetic fields, in hot, high density plasmas. The concept consists of accelerating a probe to high velocities (2.2 Km/s) in order to minimize probe exposure time to plasma. Faraday rotation within the probe is used to measure the local magnetic field. An Argon laser illuminates the probe consisting of a Faraday-rotator material with a retro-reflector that returns the incident light to the detection system. Performance results of the light gas gun and optical detection system will be shown. To date, the gas gun has been extensively tested consistently achieving velocities between 2 and 3 km/s. The probe and detection scheme have been tested by dropping the probe through a static magnetic field. Magnetic field resolution of 20 gauss and spatial resolution of 5 mm has been achieved. System frequency response is 10Mhz. Work is currently being conducted to integrate the diagnostic system with laboratory plasma experiments. Specifically a gas interfaced system has been developed to prevent helium muzzle gas from entering the plasma chamber with the probe. Additionally the probe must be separated from the sabot which protects the probe during acceleration in the gas gun. Data will be presented showing the results of various separation techniques.

  2. Results of a Parametric Study on 10,000 lb. and 50,000 lb. Permanent Magnetic Actuators

    NASA Technical Reports Server (NTRS)

    Stekly, Z. J. J.; Gardner, C.; Domigan, P.; McDonald, C.; Farrell, R. A.

    1996-01-01

    The purpose of this study was to generate design data and complete dynamic performance estimates for a high performance permanent magnet actuator. The basic configuration selected for analysis is an axisymmetric Nd-B-Fe permanent magnet actuator capable of providing force in one direction along its major axis. The actuator consisted of two main axisymmetric components separated by an air gap. The design was optimized for each value of force, gap and magnetic field to yield minimum weight and maximum lift to weight ratio. The basic conclusion is that, within parameters considered, the 10,000 lb. and 50,000 lb. actuators are lightweight and compact. As expected for most permanent magnet devices, the smaller ones have higher lift to eight ratios.

  3. Brake Failure from Residual Magnetism in the Mars Exploration Rover Lander Petal Actuator

    NASA Technical Reports Server (NTRS)

    Jandura, Louise

    2004-01-01

    In January 2004, two Mars Exploration Rover spacecraft arrived at Mars. Each safely delivered an identical rover to the Martian surface in a tetrahedral lander encased in airbags. Upon landing, the airbags deflated and three Lander Petal Actuators opened the three deployable Lander side petals enabling the rover to exit the Lander. Approximately nine weeks prior to the scheduled launch of the first spacecraft, one of these mission-critical Lander Petal Actuators exhibited a brake stuck-open failure during its final flight stow at Kennedy Space Center. Residual magnetism was the definitive conclusion from the failure investigation. Although residual magnetism was recognized as an issue in the design, the lack of an appropriately specified lower bound on brake drop-out voltage inhibited the discovery of this problem earlier in the program. In addition, the brakes had more unit-to-unit variation in drop-out voltage than expected, likely due to a larger than expected variation in the magnetic properties of the 15-5 PH stainless steel brake plates. Failure analysis and subsequent rework of two other Lander Petal Actuators with marginal brakes was completed in three weeks, causing no impact to the launch date.

  4. Thickness dependence of voltage-driven magnetization switching in FeCo/PI/piezoelectric actuator heterostructures

    NASA Astrophysics Data System (ADS)

    Cui, B. S.; Guo, X. B.; Wu, K.; Li, D.; Zuo, Y. L.; Xi, L.

    2016-03-01

    Strain mediated magnetization switching of ferromagnetic/substrate/piezoelectric actuator heterostructures has become a hot issue due to the advantage of low-power consumption. In this work, Fe65Co35 thin films were deposited on a flexible polyamides (PI) substrate, which has quite low Young’s module (~4 GPa for PI as compared to ~180 GPa for Si) and benefits from complete transfer of the strain from the piezoelectric actuator to magnetic thin films. A complete 90° transition of the magnetic easy axis was realized in 50 nm thick FeCo films under the voltage of 70 V, while a less than 90° rotation angle of the magnetic easy axis direction was observed in other samples, which was ascribed to the distribution of the anisotropy field and/or the orthogonal misalignment between stress induced anisotropy and original uniaxial anisotropy. A model considering two uniaxial anisotropies with orthogonal arrangement was used to quantitatively understand the observed results and the linear-like voltage dependent anisotropy field, especially for 10 nm FeCo films, in which the switching mechanism along the easy axis direction can be explained by the domain wall depinning model. It indicates that the magnetic domain-wall movement velocity may be controlled by strain through tuning the energy barrier of the pinning in heterostructures. Moreover, voltage-driven 90° magnetization switching with low-power consumption was achieved in this work.

  5. Feedforward-Feedback Hybrid Control for Magnetic Shape Memory Alloy Actuators Based on the Krasnosel'skii-Pokrovskii Model

    PubMed Central

    Zhou, Miaolei; Zhang, Qi; Wang, Jingyuan

    2014-01-01

    As a new type of smart material, magnetic shape memory alloy has the advantages of a fast response frequency and outstanding strain capability in the field of microdrive and microposition actuators. The hysteresis nonlinearity in magnetic shape memory alloy actuators, however, limits system performance and further application. Here we propose a feedforward-feedback hybrid control method to improve control precision and mitigate the effects of the hysteresis nonlinearity of magnetic shape memory alloy actuators. First, hysteresis nonlinearity compensation for the magnetic shape memory alloy actuator is implemented by establishing a feedforward controller which is an inverse hysteresis model based on Krasnosel'skii-Pokrovskii operator. Secondly, the paper employs the classical Proportion Integration Differentiation feedback control with feedforward control to comprise the hybrid control system, and for further enhancing the adaptive performance of the system and improving the control accuracy, the Radial Basis Function neural network self-tuning Proportion Integration Differentiation feedback control replaces the classical Proportion Integration Differentiation feedback control. Utilizing self-learning ability of the Radial Basis Function neural network obtains Jacobian information of magnetic shape memory alloy actuator for the on-line adjustment of parameters in Proportion Integration Differentiation controller. Finally, simulation results show that the hybrid control method proposed in this paper can greatly improve the control precision of magnetic shape memory alloy actuator and the maximum tracking error is reduced from 1.1% in the open-loop system to 0.43% in the hybrid control system. PMID:24828010

  6. Feedforward-feedback hybrid control for magnetic shape memory alloy actuators based on the Krasnosel'skii-Pokrovskii model.

    PubMed

    Zhou, Miaolei; Zhang, Qi; Wang, Jingyuan

    2014-01-01

    As a new type of smart material, magnetic shape memory alloy has the advantages of a fast response frequency and outstanding strain capability in the field of microdrive and microposition actuators. The hysteresis nonlinearity in magnetic shape memory alloy actuators, however, limits system performance and further application. Here we propose a feedforward-feedback hybrid control method to improve control precision and mitigate the effects of the hysteresis nonlinearity of magnetic shape memory alloy actuators. First, hysteresis nonlinearity compensation for the magnetic shape memory alloy actuator is implemented by establishing a feedforward controller which is an inverse hysteresis model based on Krasnosel'skii-Pokrovskii operator. Secondly, the paper employs the classical Proportion Integration Differentiation feedback control with feedforward control to comprise the hybrid control system, and for further enhancing the adaptive performance of the system and improving the control accuracy, the Radial Basis Function neural network self-tuning Proportion Integration Differentiation feedback control replaces the classical Proportion Integration Differentiation feedback control. Utilizing self-learning ability of the Radial Basis Function neural network obtains Jacobian information of magnetic shape memory alloy actuator for the on-line adjustment of parameters in Proportion Integration Differentiation controller. Finally, simulation results show that the hybrid control method proposed in this paper can greatly improve the control precision of magnetic shape memory alloy actuator and the maximum tracking error is reduced from 1.1% in the open-loop system to 0.43% in the hybrid control system.

  7. A platform for designing hyperpolarized magnetic resonance chemical probes

    PubMed Central

    Nonaka, Hiroshi; Hata, Ryunosuke; Doura, Tomohiro; Nishihara, Tatsuya; Kumagai, Keiko; Akakabe, Mai; Tsuda, Masashi; Ichikawa, Kazuhiro; Sando, Shinsuke

    2013-01-01

    Hyperpolarization is a highly promising technique for improving the sensitivity of magnetic resonance chemical probes. Here we report [15N, D9]trimethylphenylammonium as a platform for designing a variety of hyperpolarized magnetic resonance chemical probes. The platform structure shows a remarkably long 15N spin–lattice relaxation value (816 s, 14.1 T) for retaining its hyperpolarized spin state. The extended lifetime enables the detection of the hyperpolarized 15N signal of the platform for several tens of minutes and thus overcomes the intrinsic short analysis time of hyperpolarized probes. Versatility of the platform is demonstrated by applying it to three types of hyperpolarized chemical probes: one each for sensing calcium ions, reactive oxygen species (hydrogen peroxide) and enzyme activity (carboxyl esterase). All of the designed probes achieve high sensitivity with rapid reactions and chemical shift changes, which are sufficient to allow sensitive and real-time monitoring of target molecules by 15N magnetic resonance. PMID:24022444

  8. The decay properties of the trapped magnetic field in HTS bulk superconducting actuator by AC controlled magnetic field

    NASA Astrophysics Data System (ADS)

    Kim, S. B.; Uwani, Y.; Joo, J. H.; Kawamoto, R.; Jo, Y. S.

    2011-11-01

    The electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties according to their strong flux pinning force, have been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contract transportation device which moves freely in space. It is certain for our proposed 3-D superconducting actuator to be useful as a transporter used in a clean room where silicon wafers, which do not like mechanical contact and dust, are manufactured. The proposed actuator consists of the trapped HTS bulk as a mover and two-dimensionally arranged electromagnets as a stator. Up to now, the electromagnets consisted with iron core and copper coil were used as a stator, and each electromagnet was individually controlled using DC power supplies. In our previous work, the unstable movement characteristics of HTS bulk were observed under the DC operation, and the AC electromagnets driven with AC controlled current was proposed to solve these problems. In general, the trapped magnetic field in HTS bulk was decayed by a time-varying external magnetic field. Thus, it needs to optimize the shapes of AC electromagnets and operating patterns, the decay properties of the trapped magnetic field in the HTS bulk mover by the AC magnetic field should be cleared. In this paper, the influences of the frequency, the overall operating time, the strength of magnetization field and drive current against the decay of trapped magnetic field were experimentally studied using the fabricated AC electromagnets.

  9. Inductively Heated Shape Memory Polymer for the Magnetic Actuation of Medical Devices

    SciTech Connect

    Buckley, P; Mckinley, G; Wilson, T; Small, W; Benett, W; Bearinger, J; McElfresh, M; Maitland, D

    2005-09-06

    Presently there is interest in making medical devices such as expandable stents and intravascular microactuators from shape memory polymer (SMP). One of the key challenges in realizing SMP medical devices is the implementation of a safe and effective method of thermally actuating various device geometries in vivo. A novel scheme of actuation by Curie-thermoregulated inductive heating is presented. Prototype medical devices made from SMP loaded with Nickel Zinc ferrite ferromagnetic particles were actuated in air by applying an alternating magnetic field to induce heating. Dynamic mechanical thermal analysis was performed on both the particle-loaded and neat SMP materials to assess the impact of the ferrite particles on the mechanical properties of the samples. Calorimetry was used to quantify the rate of heat generation as a function of particle size and volumetric loading of ferrite particles in the SMP. These tests demonstrated the feasibility of SMP actuation by inductive heating. Rapid and uniform heating was achieved in complex device geometries and particle loading up to 10% volume content did not interfere with the shape recovery of the SMP.

  10. Inductively heated shape memory polymer for the magnetic actuation of medical devices.

    PubMed

    Buckley, Patrick R; McKinley, Gareth H; Wilson, Thomas S; Small, Ward; Benett, William J; Bearinger, Jane P; McElfresh, Michael W; Maitland, Duncan J

    2006-10-01

    Presently, there is interest in making medical devices such as expandable stents and intravascular microactuators from shape memory polymer (SMP). One of the key challenges in realizing SMP medical devices is the implementation of a safe and effective method of thermally actuating various device geometries in vivo. A novel scheme of actuation by Curie-thermoregulated inductive heating is presented. Prototype medical devices made from SMP loaded with nickel zinc ferrite ferromagnetic particles were actuated in air by applying an alternating magnetic field to induce heating. Dynamic mechanical thermal analysis was performed on both the particle-loaded and neat SMP materials to assess the impact of the ferrite particles on the mechanical properties of the samples. Calorimetry was used to quantify the rate of heat generation as a function of particle size and volumetric loading of ferrite particles in the SMP. These tests demonstrated the feasibility of SMP actuation by inductive heating. Rapid and uniform heating was achieved in complex device geometries and particle loading up to 10% volume content did not interfere with the shape recovery of the SMP.

  11. Control and actuator design for a precision magnetic suspension linear bearing

    NASA Astrophysics Data System (ADS)

    Trumper, David L.; Queen, Michael A.

    1992-07-01

    In optical systems, where the positions of such components as mirrors must be controlled in six degrees of freedom (DOFs), magnetic bearings can impart forces and torques to the suspended component without rigidly constraining its DOFs, and obviate the complex flexures typical of conventional designs. Attention is here given to a magnetically suspended linear bearing employing variable-reluctance actuators to control three rotational and two translational DOFs, as well as to a linear motor charged with control of the sixth DOF. Applicability to vibration isolation and optical line-of-sight stabilization are noted.

  12. Experimental Results from Railgun Firings Involving Magnetic Flux Probes.

    DTIC Science & Technology

    1986-12-01

    of railgun firings, the voltages induced in small solenoidal probes mounted in different positions and orientations along the barrel were measured to...different positions and orientations along the barrel were measured to gain a better understanding of the current density and magnetic field in a...ACKNOWLEDGEMENTS 7. REFERENCES 10 I’. 4¢ EXPERIMENTAL RESULTS FROM RAILGUN FIRINGS INVOLVING MAGNETIC FLUX PROBES 1. INTRODUCTION The Lorentz force acting on the

  13. Mapping of Bacterial Biofilm Local Mechanics by Magnetic Microparticle Actuation

    PubMed Central

    Galy, Olivier; Latour-Lambert, Patricia; Zrelli, Kais; Ghigo, Jean-Marc; Beloin, Christophe; Henry, Nelly

    2012-01-01

    Most bacteria live in the form of adherent communities forming three-dimensional material anchored to artificial or biological surfaces, with profound impact on many human activities. Biofilms are recognized as complex systems but their physical properties have been mainly studied from a macroscopic perspective. To determine biofilm local mechanical properties, reveal their potential heterogeneity, and investigate their relation to molecular traits, we have developed a seemingly new microrheology approach based on magnetic particle infiltration in growing biofilms. Using magnetic tweezers, we achieved what was, to our knowledge, the first three-dimensional mapping of the viscoelastic parameters on biofilms formed by the bacterium Escherichia coli. We demonstrate that its mechanical profile may exhibit elastic compliance values spread over three orders of magnitude in a given biofilm. We also prove that heterogeneity strongly depends on external conditions such as growth shear stress. Using strains genetically engineered to produce well-characterized cell surface adhesins, we show that the mechanical profile of biofilm is exquisitely sensitive to the expression of different surface appendages such as F pilus or curli. These results provide a quantitative view of local mechanical properties within intact biofilms and open up an additional avenue for elucidating the emergence and fate of the different microenvironments within these living materials. PMID:22995513

  14. Broad-band magnetic induction probe calibration using a frequency-corrected reference probe.

    PubMed

    Hill, Carrie

    2013-10-01

    Finite impedances of magnetic induction probes attenuate and shift the field fluctuations measured by the probe so that they differ from the measured signal at the digitizer. These effects vary with frequency. Traditionally, impedance effects have been accounted for in the calibration process by sweeping the frequency of the magnetic field source through a range of frequencies. Situations arise where the conventional calibration method is not feasible due to probe geometry or hardware constraints. A new calibration technique is presented in this paper which calibrates the probe in situ at a single frequency and uses impedance measurements of the probe assembly across the desired frequency range to account for broad-band effects. The in situ calibration technique requires a reference probe with a known proportionality constant NA and known impedances. Impedance effects are corrected in the probe signal using broad-band impedance measurements included in a transfer function in frequency space. The in situ calibration technique is shown to be complicated by capacitive coupling between the probes and the high voltage source coil. Circuit modeling demonstrates that this coupling introduces negligible attenuation and a small phase-delay so that the relative phase-delay between the reference and target probe signals can be corrected by shifting the signals in time. In summary, this calibration method extends traditional single-frequency calibration techniques to broad-band applications, accounting for important non-ideal effects to improve the accuracy of the magnetic field measurement.

  15. Swimming of a Microrobot Actuated by a Clinical Magnetic Resonance Imaging Apparatus

    NASA Astrophysics Data System (ADS)

    Gosselin, Frederck P.; Zhou, David; Lalande, Viviane; Vonthron, Manuel; Martel, Sylvain

    2010-11-01

    A miniature robot was designed to achieve fish-like locomotion when actuated by the imaging coils of a clinical Magnetic Resonance Imaging (MRI) system. The wireless fish robot is composed of a ferromagnetic head, a flexible tail and a float. In an aquarium placed in the MRI, the robot is set into a swimming motion by an alternating transverse linear magnetic gradient. The influence of tail length, forcing frequency and forcing magnitude on the swimming velocity and flapping amplitude are investigated. Moreover, by using a combination of simultaneous magnetic gradients, the fish can reach superior swimming speeds than can be achieved by simply "pulling" on the fish with a magnetic field. Upon further miniaturization, the propulsion principle devised here could be used to navigate a micro surgical robot or a drug delivery system. A great advantage of this system is that no energy storage, motor or control system need to be carried by the robot, allowing great miniaturization possibilities.

  16. Remote Actuation of Magnetic Nanoparticles For Cancer Cell Selective Treatment Through Cytoskeletal Disruption.

    PubMed

    Master, Alyssa M; Williams, Philise N; Pothayee, Nikorn; Pothayee, Nipon; Zhang, Rui; Vishwasrao, Hemant M; Golovin, Yuri I; Riffle, Judy S; Sokolsky, Marina; Kabanov, Alexander V

    2016-09-20

    Motion of micron and sub-micron size magnetic particles in alternating magnetic fields can activate mechanosensitive cellular functions or physically destruct cancer cells. However, such effects are usually observed with relatively large magnetic particles (>250 nm) that would be difficult if at all possible to deliver to remote sites in the body to treat disease. Here we show a completely new mechanism of selective toxicity of superparamagnetic nanoparticles (SMNP) of 7 to 8 nm in diameter to cancer cells. These particles are coated by block copolymers, which facilitates their entry into the cells and clustering in the lysosomes, where they are then magneto-mechanically actuated by remotely applied alternating current (AC) magnetic fields of very low frequency (50 Hz). Such fields and treatments are safe for surrounding tissues but produce cytoskeletal disruption and subsequent death of cancer cells while leaving healthy cells intact.

  17. Remote Actuation of Magnetic Nanoparticles For Cancer Cell Selective Treatment Through Cytoskeletal Disruption

    PubMed Central

    Master, Alyssa M.; Williams, Philise N.; Pothayee, Nikorn; Pothayee, Nipon; Zhang, Rui; Vishwasrao, Hemant M.; Golovin, Yuri I.; Riffle, Judy S.; Sokolsky, Marina; Kabanov, Alexander V.

    2016-01-01

    Motion of micron and sub-micron size magnetic particles in alternating magnetic fields can activate mechanosensitive cellular functions or physically destruct cancer cells. However, such effects are usually observed with relatively large magnetic particles (>250 nm) that would be difficult if at all possible to deliver to remote sites in the body to treat disease. Here we show a completely new mechanism of selective toxicity of superparamagnetic nanoparticles (SMNP) of 7 to 8 nm in diameter to cancer cells. These particles are coated by block copolymers, which facilitates their entry into the cells and clustering in the lysosomes, where they are then magneto-mechanically actuated by remotely applied alternating current (AC) magnetic fields of very low frequency (50 Hz). Such fields and treatments are safe for surrounding tissues but produce cytoskeletal disruption and subsequent death of cancer cells while leaving healthy cells intact. PMID:27644858

  18. Poly-l-lysine-coated magnetic nanoparticles as intracellular actuators for neural guidance.

    PubMed

    Riggio, Cristina; Calatayud, Maria Pilar; Hoskins, Clare; Pinkernelle, Josephine; Sanz, Beatriz; Torres, Teobaldo Enrique; Ibarra, Manuel Ricardo; Wang, Lijun; Keilhoff, Gerburg; Goya, Gerardo Fabian; Raffa, Vittoria; Cuschieri, Alfred

    2012-01-01

    It has been proposed in the literature that Fe(3)O(4) magnetic nanoparticles (MNPs) could be exploited to enhance or accelerate nerve regeneration and to provide guidance for regenerating axons. MNPs could create mechanical tension that stimulates the growth and elongation of axons. Particles suitable for this purpose should possess (1) high saturation magnetization, (2) a negligible cytotoxic profile, and (3) a high capacity to magnetize mammalian cells. Unfortunately, the materials currently available on the market do not satisfy these criteria; therefore, this work attempts to overcome these deficiencies. Magnetite particles were synthesized by an oxidative hydrolysis method and characterized based on their external morphology and size distribution (high-resolution transmission electron microscopy [HR-TEM]) as well as their colloidal (Z potential) and magnetic properties (Superconducting QUantum Interference Devices [SQUID]). Cell viability was assessed via Trypan blue dye exclusion assay, cell doubling time, and MTT cell proliferation assay and reactive oxygen species production. Particle uptake was monitored via Prussian blue staining, intracellular iron content quantification via a ferrozine-based assay, and direct visualization by dual-beam (focused ion beam/scanning electron microscopy [FIB/SEM]) analysis. Experiments were performed on human neuroblastoma SH-SY5Y cell line and primary Schwann cell cultures of the peripheral nervous system. This paper reports on the synthesis and characterization of polymer-coated magnetic Fe(3)O(4) nanoparticles with an average diameter of 73 ± 6 nm that are designed as magnetic actuators for neural guidance. The cells were able to incorporate quantities of iron up to 2 pg/cell. The intracellular distribution of MNPs obtained by optical and electronic microscopy showed large structures of MNPs crossing the cell membrane into the cytoplasm, thus rendering them suitable for magnetic manipulation by external magnetic fields

  19. Poly-l-lysine-coated magnetic nanoparticles as intracellular actuators for neural guidance

    PubMed Central

    Riggio, Cristina; Calatayud, Maria Pilar; Hoskins, Clare; Pinkernelle, Josephine; Sanz, Beatriz; Torres, Teobaldo Enrique; Ibarra, Manuel Ricardo; Wang, Lijun; Keilhoff, Gerburg; Goya, Gerardo Fabian; Raffa, Vittoria; Cuschieri, Alfred

    2012-01-01

    Purpose It has been proposed in the literature that Fe3O4 magnetic nanoparticles (MNPs) could be exploited to enhance or accelerate nerve regeneration and to provide guidance for regenerating axons. MNPs could create mechanical tension that stimulates the growth and elongation of axons. Particles suitable for this purpose should possess (1) high saturation magnetization, (2) a negligible cytotoxic profile, and (3) a high capacity to magnetize mammalian cells. Unfortunately, the materials currently available on the market do not satisfy these criteria; therefore, this work attempts to overcome these deficiencies. Methods Magnetite particles were synthesized by an oxidative hydrolysis method and characterized based on their external morphology and size distribution (high-resolution transmission electron microscopy [HR-TEM]) as well as their colloidal (Z potential) and magnetic properties (Superconducting QUantum Interference Devices [SQUID]). Cell viability was assessed via Trypan blue dye exclusion assay, cell doubling time, and MTT cell proliferation assay and reactive oxygen species production. Particle uptake was monitored via Prussian blue staining, intracellular iron content quantification via a ferrozine-based assay, and direct visualization by dual-beam (focused ion beam/scanning electron microscopy [FIB/SEM]) analysis. Experiments were performed on human neuroblastoma SH-SY5Y cell line and primary Schwann cell cultures of the peripheral nervous system. Results This paper reports on the synthesis and characterization of polymer-coated magnetic Fe3O4 nanoparticles with an average diameter of 73 ± 6 nm that are designed as magnetic actuators for neural guidance. The cells were able to incorporate quantities of iron up to 2 pg/cell. The intracellular distribution of MNPs obtained by optical and electronic microscopy showed large structures of MNPs crossing the cell membrane into the cytoplasm, thus rendering them suitable for magnetic manipulation by external

  20. On-chip magnetically actuated robot with ultrasonic vibration for single cell manipulations.

    PubMed

    Hagiwara, Masaya; Kawahara, Tomohiro; Yamanishi, Yoko; Masuda, Taisuke; Feng, Lin; Arai, Fumihito

    2011-06-21

    This paper presents an innovative driving method for an on-chip robot actuated by permanent magnets in a microfluidic chip. A piezoelectric ceramic is applied to induce ultrasonic vibration to the microfluidic chip and the high-frequency vibration reduces the effective friction on the MMT significantly. As a result, we achieved 1.1 micrometre positioning accuracy of the microrobot, which is 100 times higher accuracy than without vibration. The response speed is also improved and the microrobot can be actuated with a speed of 5.5 mm s(-1) in 3 degrees of freedom. The novelty of the ultrasonic vibration appears in the output force as well. Contrary to the reduction of friction on the microrobot, the output force increased twice as much by the ultrasonic vibration. Using this high accuracy, high speed, and high power microrobot, swine oocyte manipulations are presented in a microfluidic chip.

  1. Tracking Control of a Magnetic Shape Memory Actuator Using an Inverse Preisach Model with Modified Fuzzy Sliding Mode Control.

    PubMed

    Lin, Jhih-Hong; Chiang, Mao-Hsiung

    2016-08-25

    Magnetic shape memory (MSM) alloys are a new class of smart materials with extraordinary strains up to 12% and frequencies in the range of 1 to 2 kHz. The MSM actuator is a potential device which can achieve high performance electromagnetic actuation by using the properties of MSM alloys. However, significant non-linear hysteresis behavior is a significant barrier to control the MSM actuator. In this paper, the Preisach model was used, by capturing experiments from different input signals and output responses, to model the hysteresis of MSM actuator, and the inverse Preisach model, as a feedforward control, provided compensational signals to the MSM actuator to linearize the hysteresis non-linearity. The control strategy for path tracking combined the hysteresis compensator and the modified fuzzy sliding mode control (MFSMC) which served as a path controller. Based on the experimental results, it was verified that a tracking error in the order of micrometers was achieved.

  2. Tracking Control of a Magnetic Shape Memory Actuator Using an Inverse Preisach Model with Modified Fuzzy Sliding Mode Control

    PubMed Central

    Lin, Jhih-Hong; Chiang, Mao-Hsiung

    2016-01-01

    Magnetic shape memory (MSM) alloys are a new class of smart materials with extraordinary strains up to 12% and frequencies in the range of 1 to 2 kHz. The MSM actuator is a potential device which can achieve high performance electromagnetic actuation by using the properties of MSM alloys. However, significant non-linear hysteresis behavior is a significant barrier to control the MSM actuator. In this paper, the Preisach model was used, by capturing experiments from different input signals and output responses, to model the hysteresis of MSM actuator, and the inverse Preisach model, as a feedforward control, provided compensational signals to the MSM actuator to linearize the hysteresis non-linearity. The control strategy for path tracking combined the hysteresis compensator and the modified fuzzy sliding mode control (MFSMC) which served as a path controller. Based on the experimental results, it was verified that a tracking error in the order of micrometers was achieved. PMID:27571081

  3. Magnetically-Actuated Escherichia coli System for Micro Lithography

    NASA Astrophysics Data System (ADS)

    Lauback, S.; Brown, E.; Pérez-Guzman, L.; Peace, C.; Pierce, C.; Lower, B. H.; Lower, S. K.; Sooryakumar, R.

    2015-03-01

    Technologies that control matter at the nano- and micro-scale are crucial for developing new engineered materials and devices. While the more traditional approaches for such manipulations often depend on lithographic fabrication, they can be expanded upon by taking advantage of the biological systems within a living cell which also operate on the nano- and micro- scale. In this study, a system is being developed to functionalize a targeted location on the surface of a chip with the protein AmCyan from transformed Escherichia coli cells. Using established methods in molecular biology where a plasmid with the amcyan gene sequence is inserted into the cell, E. coli are engineered to express the AmCyan protein on their outer surface. In order to transport the cells to the targeted location, the transformed E. coli are labeled with superparamagnetic micro-beads which exert directed forces on the cells in an external field. Preliminary results of the protein expression on E. coli, the transport of the cell through weak magnetic fields to targeted locations and the potential to transfer protein from the cell to the chip surface will be presented.

  4. Magnetoelectric versus thermal actuation characteristics of shear force AFM probes with piezoresistive detection

    NASA Astrophysics Data System (ADS)

    Sierakowski, Andrzej; Kopiec, Daniel; Majstrzyk, Wojciech; Kunicki, Piotr; Janus, Paweł; Dobrowolski, Rafał; Grabiec, Piotr; Rangelow, Ivo W.; Gotszalk, Teodor

    2017-03-01

    In this paper the authors compare methods used for piezoresistive microcantilevers actuation for the atomic force microscopy (AFM) imaging in the dynamic shear force mode. The piezoresistive detection is an attractive technique comparing the optical beam detection of deflection. The principal advantage is that no external alignment of optical source and detector are needed. When the microcantilever is deflected, the stress is transferred into a change of resistivity of piezoresistors. The integration of piezoresistive read-out provides a promising solution in realizing a compact non-contact AFM. Resolution of piezoresistive read-out is limited by three main noise sources: Johnson, 1/f and thermomechanical noise. In the dynamic shear force mode measurement the method used for cantilever actuation will also affect the recorded noise in the piezoresistive detection circuit. This is the result of a crosstalk between an aluminium path (current loop used for actuation) and piezoresistors located near the base of the beam. In this paper authors described an elaborated in ITE (Institute of Electron Technology) technology of fabrication cantilevers with piezoresistive detection of deflection and compared efficiency of two methods used for cantilever actuation.

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  6. Fluid transport at low Reynolds number with magnetically actuated artificial cilia

    NASA Astrophysics Data System (ADS)

    Gauger, E. M.; Downton, M. T.; Stark, H.

    2009-02-01

    By numerical modeling we investigate fluid transport in low-Reynolds-number flow achieved with a special elastic filament or artifical cilium attached to a planar surface. The filament is made of superparamagnetic particles linked together by DNA double strands. An external magnetic field induces dipolar interactions between the beads of the filament which provides a convenient way of actuating the cilium in a well-controlled manner. The filament has recently been used to successfully construct the first artificial micro-swimmer (R. Dreyfus et al., Nature 437, 862 (2005)). In our numerical study we introduce a measure, which we call pumping performance, to quantify the fluid transport induced by the magnetically actuated cilium and identify an optimum stroke pattern of the filament. It consists of a slow transport stroke and a fast recovery stroke. Our detailed parameter study also reveals that for sufficiently large magnetic fields the artificial cilium is mainly governed by the Mason number that compares frictional to magnetic forces. Initial studies on multi-cilia systems show that the pumping performance is very sensitive to the imposed phase lag between neighboring cilia, i.e., to the details of the initiated metachronal wave.

  7. Implementation of Akiyama probe in low temperature magnetic force microscope

    NASA Astrophysics Data System (ADS)

    Sass, Paul; Wu, Weida

    Exotic phenomena often call for high sensitivity scanning probe microscopic techniques working at extremely low temperatures. Specifically, it is of great fundamental interest to detect the weak magnetic signals in a range of interesting systems such as, quantum anomalous Hall, skyrmion, heavy-fermion, and multiferroic systems. To this end, we are developing low temperature magnetic force microscope (MFM) using a self-sensing cantilever called Akiyama-probe (A-probe). The main advantage of this specific probe is its extremely low power-dissipation compared to other self-sensing (e.g. piezoresistive) cantilevers for low temperature application. We will present progress of the implementation of A-probe and preliminary results under various conditions. This work is supported by DOE BES under Award DE-SC0008147.

  8. Magnetic resonance force microscopy with a paramagnetic probe

    DOE PAGES

    Berman, G. P.; Gorshkov, V. N.; Tsifrinovich, V. I.

    2017-04-01

    Here, we consider theoretically extension of magnetic resonance force microscopy (MRFM) replacing a ferromagnetic probe on a cantilever tip (CT) with a paramagnetic one (PMRFM). The dynamics of the interaction between the paramagnetic probe and a local magnetic moment in a sample is analyzed, using a quasi-classical approach. We show that the application of a proper sequence of electromagnetic pulses provides a significant deflection of the CT from the initial equilibrium position. Periodic application of these sequences of pulses results in quasi-periodic CT deflections from the equilibrium, which can be used for detection of the magnetic moment in a sample.

  9. Magnetic resonance force microscopy with a paramagnetic probe

    NASA Astrophysics Data System (ADS)

    Berman, G. P.; Gorshkov, V. N.; Tsifrinovich, V. I.

    2017-04-01

    We consider theoretically extension of magnetic resonance force microscopy (MRFM) replacing a ferromagnetic probe on a cantilever tip (CT) with a paramagnetic one (PMRFM). The dynamics of the interaction between the paramagnetic probe and a local magnetic moment in a sample is analyzed, using a quasi-classical approach. We show that the application of a proper sequence of electromagnetic pulses provides a significant deflection of the CT from the initial equilibrium position. Periodic application of these sequences of pulses results in quasi-periodic CT deflections from the equilibrium, which can be used for detection of the magnetic moment in a sample.

  10. Detecting magnetic ordering with atomic size electron probes

    SciTech Connect

    Idrobo, Juan Carlos; Rusz, Ján; Spiegelberg, Jakob; McGuire, Michael A.; Symons, Christopher T.; Vatsavai, Ranga Raju; Cantoni, Claudia; Lupini, Andrew R.

    2016-05-27

    While magnetism originates at the atomic scale, the existing spectroscopic techniques sensitive to magnetic signals only produce spectra with spatial resolution on a larger scale. However, recently, it has been theoretically argued that atomic size electron probes with customized phase distributions can detect magnetic circular dichroism. Here, we report a direct experimental real-space detection of magnetic circular dichroism in aberration-corrected scanning transmission electron microscopy (STEM). Using an atomic size-aberrated electron probe with a customized phase distribution, we reveal the checkerboard antiferromagnetic ordering of Mn moments in LaMnAsO by observing a dichroic signal in the Mn L-edge. The novel experimental setup presented here, which can easily be implemented in aberration-corrected STEM, opens new paths for probing dichroic signals in materials with unprecedented spatial resolution.

  11. Detecting magnetic ordering with atomic size electron probes

    DOE PAGES

    Idrobo, Juan Carlos; Rusz, Ján; Spiegelberg, Jakob; ...

    2016-05-27

    While magnetism originates at the atomic scale, the existing spectroscopic techniques sensitive to magnetic signals only produce spectra with spatial resolution on a larger scale. However, recently, it has been theoretically argued that atomic size electron probes with customized phase distributions can detect magnetic circular dichroism. Here, we report a direct experimental real-space detection of magnetic circular dichroism in aberration-corrected scanning transmission electron microscopy (STEM). Using an atomic size-aberrated electron probe with a customized phase distribution, we reveal the checkerboard antiferromagnetic ordering of Mn moments in LaMnAsO by observing a dichroic signal in the Mn L-edge. The novel experimental setupmore » presented here, which can easily be implemented in aberration-corrected STEM, opens new paths for probing dichroic signals in materials with unprecedented spatial resolution.« less

  12. Magnetic field measurements using the transient internal probe (TIP)

    SciTech Connect

    Galambos, J.P.; Bohnet, M.A.; Jarboe, T.R.; Mattick, A.T.

    1995-12-31

    Knowledge of the internal magnetic field profile in hot plasmas is fundamental to understanding the structure and behavior of the current profile. The transient internal probe (TIP) is a novel diagnostic designed to measure internal magnetic fields in hot plasmas. The diagnostic involves shooting a magneto-optic probe through the plasma at high velocities (greater than 2 km/s) using a two stage light gas gun. Local fields are obtained by illuminating the probe with an argon ion laser and measuring the amount of Faraday rotation in the reflected beam. Initial development of the diagnostic is complete. Results of magnetic field measurements conducted at 2 km/s will be presented. Helium muzzle gas introduction to the plasma chamber has been limited to less than 0.4 Torr-{ell}. Magnetic field resolution of 40 Gauss and spatial resolution of 5 mm have been achieved. System frequency response is 10 MHz.

  13. Biomimetic cilia arrays - fabrication, magnetic actuation, and driven fluid transport phenomena

    NASA Astrophysics Data System (ADS)

    Shields, Adam

    The cilium is one of biology's most basic functional nanostructures, present on nearly every cell and increasingly realized as vital to many aspects of human health. A fundamental reason for the ubiquity of cilia is their ability to effectively interact with fluids at the microscale, where the Reynolds number is low and thus inertia is irrelevant. This ability makes cilia an attractive and popular candidate for an engineered biomimic with potential applications in microfluidics and sensing. In addition, biological ciliated systems are difficult to study for many reasons, and so I demonstrate how a functional biomimetic system can also serve as a model platform for highly controlled studies of biologically relevant, cilia-driven hydrodynamics. Using the template-based microfabrication of a magnetic nanoparticle/polymer composite, I fabricate arrays of magnetically actuated biomimetic cilia at the scale of their biological analogues. I will discuss this fabrication technique and the magnetic actuation of these arrays to mimic the beat of biological cilia. I also report on the nature of the fluid flows driven by the cilia beat, and demonstrate how these cilia arrays can simultaneously generate long-range fluid transport and mixing in distinct fluid flow regimes. Finally, I present these results within the context of canonical hydrodynamics problems and discuss the implications for biological systems, such as the motile cilia recently discovered in the embryonic node.

  14. Nanopatterning reconfigurable magnetic landscapes via thermally assisted scanning probe lithography.

    PubMed

    Albisetti, E; Petti, D; Pancaldi, M; Madami, M; Tacchi, S; Curtis, J; King, W P; Papp, A; Csaba, G; Porod, W; Vavassori, P; Riedo, E; Bertacco, R

    2016-06-01

    The search for novel tools to control magnetism at the nanoscale is crucial for the development of new paradigms in optics, electronics and spintronics. So far, the fabrication of magnetic nanostructures has been achieved mainly through irreversible structural or chemical modifications. Here, we propose a new concept for creating reconfigurable magnetic nanopatterns by crafting, at the nanoscale, the magnetic anisotropy landscape of a ferromagnetic layer exchange-coupled to an antiferromagnetic layer. By performing localized field cooling with the hot tip of a scanning probe microscope, magnetic structures, with arbitrarily oriented magnetization and tunable unidirectional anisotropy, are reversibly patterned without modifying the film chemistry and topography. This opens unforeseen possibilities for the development of novel metamaterials with finely tuned magnetic properties, such as reconfigurable magneto-plasmonic and magnonic crystals. In this context, we experimentally demonstrate spatially controlled spin wave excitation and propagation in magnetic structures patterned with the proposed method.

  15. Development and Testing of a Magnetically Actuated Capsule Endoscopy for Obesity Treatment.

    PubMed

    Do, Thanh Nho; Seah, Tian En Timothy; Ho, Khek Yu; Yu, Ho Khek; Phee, Soo Jay

    2016-01-01

    Intra-gastric balloons (IGB) have become an efficient and less invasive method for obesity treatment. The use of traditional IGBs require complex insertion tools and flexible endoscopes to place and remove the balloon inside the patient's stomach, which may cause discomfort and complications to the patient. This paper introduces a new ingestible weight-loss capsule with a magnetically remote-controlled inflatable and deflatable balloon. To inflate the balloon, biocompatible effervescent chemicals are used. As the source of the actuation is provided via external magnetic fields, the magnetic capsule size can be significantly reduced compared to current weight-loss capsules in the literature. In addition, there are no limitations on the power supply. To lose weight, the obese subject needs only to swallow the magnetic capsule with a glass of water. Once the magnetic capsule has reached the patient's stomach, the balloon will be wirelessly inflated to occupy gastric space and give the feeling of satiety. The balloon can be wirelessly deflated at any time to allow the magnetic capsule to travel down the intestine and exit the body via normal peristalsis. The optimal ratio between the acid and base to provide the desired gas volume is experimentally evaluated and presented. A prototype capsule (9.6mm x 27mm) is developed and experimentally validated in ex-vivo experiments. The unique ease of delivery and expulsion of the proposed magnetic capsule is slated to make this development a good treatment option for people seeking to lose excess weight.

  16. Probing Magnetic Fields of Early Galaxies

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2017-06-01

    How do magnetic fields form and evolve in early galaxies? A new study has provided some clever observations to help us answer this question.The Puzzle of Growing FieldsDynamo theory is the primary model describing how magnetic fields develop in galaxies. In this picture, magnetic fields start out as weak seed fields that are small and unordered. These fields then become ordered and amplified by large-scale rotation and turbulence in galaxy disks and halos, eventually leading to the magnetic fields we observe in galaxies today.Schematic showinghow to indirectly measure protogalactic magnetic fields. The measured polarization of a background quasar is altered by the fields in a foreground protogalaxy. Click for a closer look! [Farnes et al. 2017/Adolf Schaller/STSCI/NRAO/AUI/NSF]To test this model, we need observations of the magnetic fields in young protogalaxies. Unfortunately, we dont have the sensitivity to be able to measure these fields directly but a team of scientists led by Jamie Farnes (Radboud University in the Netherlands) have come up with a creative alternative.The key is to find early protogalaxies that absorb the light of more distant background objects. If a protogalaxy lies between us and a distant quasar, then magnetic fields of the protogalaxy if present will affect the polarization measurements of the background quasar.Observing Galactic Building BlocksTop: Redshift distribution for the background quasars in the authors sample. Bottom: Redshift distribution for the foreground protogalaxies the authors are exploring. [Farnes et al. 2017]Farnes and collaborators examined two types of foreground protogalaxies: Damped Lyman-Alpha Absorbers (DLAs) and Lyman Limit Systems (LLSs). They obtained polarimetric data for a sample of 114 distant quasars with nothing in the foreground (the control sample), 19 quasars with DLAs in the foreground, and 27 quasars with LLSs in the foreground. They then used statistical analysis techniques to draw conclusions about

  17. Probing electric and magnetic vacuum fluctuations with quantum dots.

    PubMed

    Tighineanu, P; Andersen, M L; Sørensen, A S; Stobbe, S; Lodahl, P

    2014-07-25

    The electromagnetic-vacuum-field fluctuations are intimately linked to the process of spontaneous emission of light. Atomic emitters cannot probe electric- and magnetic-field fluctuations simultaneously because electric and magnetic transitions correspond to different selection rules. In this Letter we show that semiconductor quantum dots are fundamentally different and are capable of mediating electric-dipole, magnetic-dipole, and electric-quadrupole transitions on a single electronic resonance. As a consequence, quantum dots can probe electric and magnetic fields simultaneously and can thus be applied for sensing the electromagnetic environment of complex photonic nanostructures. Our study opens the prospect of interfacing quantum dots with optical metamaterials for tailoring the electric and magnetic light-matter interaction at the single-emitter level.

  18. A modified Katsumata probe--Ion sensitive probe for measurement in non-magnetized plasmas.

    PubMed

    Čada, M; Hubička, Z; Adámek, P; Olejníček, J; Kment, Š; Adámek, J; Stöckel, J

    2015-07-01

    A modified Katsumata probe has been developed for measurement of ion velocity distribution function (IVDF) in technological non-magnetized plasmas. A simple construction of the modified Katsumata probe consists of adding a pair of permanent Sm-Co magnets in front of Katsumata probe. A comparative study regarding IVDF measurement in a high power impulse magnetron sputtering system operating in pure argon atmosphere by means of developed modified Katsumata probe and commercially available gridded retarding field analyzer (RFA) has been carried out. A time-resolved measurement of IVDF for two different pressures whilst other plasma conditions have been kept unchanged has revealed that the main advantage of the modified Katsumata probe compared to the RFA consists in significantly smaller angular aperture of entrance orifice of modified Katsumata probe being approximately 15° in comparison with a commercial RFA having angular aperture more than 160°. It leads in much better velocity resolution in measured IVDF since the transversal part of velocity vector is much more suppressed compared to RFA. Furthermore, the modified Katsumata probe less suffers from collisions of ions in the space charge sheath in front or inside of the probe compared to the RFA.

  19. Magnetic Barkhausen Noise Measurements Using Tetrapole Probe Designs

    NASA Astrophysics Data System (ADS)

    McNairnay, Paul

    A magnetic Barkhausen noise (MBN) testing system was developed for Defence Research and Development Canada (DRDC) to perform MBN measurements on the Royal Canadian Navy's Victoria class submarine hulls that can be correlated with material properties, including residual stress. The DRDC system was based on the design of a MBN system developed by Steven White at Queen's University, which was capable of performing rapid angular dependent measurements through the implementation of a flux controlled tetrapole probe. In tetrapole probe designs, the magnetic excitation field is rotated in the surface plane of the sample under the assumption of linear superposition of two orthogonal magnetic fields. During the course of this work, however, the validity of flux superposition in ferromagnetic materials, for the purpose of measuring MBN, was brought into question. Consequently, a study of MBN anisotropy using tetrapole probes was performed. Results indicate that MBN anisotropy measured under flux superposition does not simulate MBN anisotropy data obtained through manual rotation of a single dipole excitation field. It is inferred that MBN anisotropy data obtained with tetrapole probes is the result of the magnetic domain structure's response to an orthogonal magnetization condition and not necessarily to any bulk superposition magnetization in the sample. A qualitative model for the domain configuration under two orthogonal magnetic fields is proposed to describe the results. An empirically derived fitting equation, that describes tetrapole MBN anisotropy data, is presented. The equation describes results in terms of two largely independent orthogonal fields, and includes interaction terms arising due to competing orthogonally magnetized domain structures and interactions with the sample's magnetic easy axis. The equation is used to fit results obtained from a number of samples and tetrapole orientations and in each case correctly identifies the samples' magnetic easy axis.

  20. High-Resolution and Frequency, Printed Miniature Magnetic Probes

    NASA Astrophysics Data System (ADS)

    Prager, James; Ziemba, Timothy; Miller, Kenneth; Picard, Julian

    2013-10-01

    Eagle Harbor Technologies, Inc. (EHT) is developing a technique to significantly reduce the cost and development time of producing magnetic field diagnostics. EHT is designing probes that can be printed on flexible PCBs thereby allowing for extremely small coils to be produced while essentially eliminating the time to wind the coils. The coil size can be extremely small when coupled with the EHT Hybrid Integrator, which is capable of high bandwidth measurements over short and long pulse durations. This integrator is currently being commercialized with the support of a DOE SBIR. Additionally, the flexible PCBs allow probes to be attached to complex surface and/or probes that have a complex 3D structure to be designed and fabricated. During the Phase I, EHT will design and construct magnetic field probes on flexible PCBs, which will be tested at the University of Washington's HIT-SI experiment and in EHT's material science plasma reactor. Funding provided by DOE SBIR/STTR Program.

  1. Magnetic probe array with high sensitivity for fluctuating field.

    PubMed

    Kanamaru, Yuki; Gota, Hiroshi; Fujimoto, Kayoko; Ikeyama, Taeko; Asai, Tomohiko; Takahashi, Tsutomu; Nogi, Yasuyuki

    2007-03-01

    A magnetic probe array is constructed to measure precisely the spatial structure of a small fluctuating field included in a strong confinement field that varies with time. To exclude the effect of the confinement field, the magnetic probes consisting of figure-eight-wound coils are prepared. The spatial structure of the fluctuating field is obtained from a Fourier analysis of the probe signal. It is found that the probe array is more sensitive to the fluctuating field with a high mode number than that with a low mode number. An experimental demonstration of the present method is attempted using a field-reversed configuration plasma, where the fluctuating field with 0.1% of the confinement field is successfully detected.

  2. Harmonic phases of the nanoparticle magnetization: An intrinsic temperature probe

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    Magnetic fluid hyperthermia is a promising cancer therapy in which magnetic nanoparticles act as heat sources activated by an external AC magnetic field. The nanoparticles, located near or inside the tumor, absorb energy from the magnetic field and then heat up the cancerous tissues. During the hyperthermia treatment, it is crucial to control the temperature of different tissues: too high temperature can cause undesired damage in healthy tissues through an uncontrolled necrosis. However, the current thermometry in magnetic hyperthermia presents some important technical problems. The widely used optical fiber thermometers only provide the temperature in a discrete set of spatial points. Moreover, surgery is required to locate these probes in the correct place. In this scope, we propose here a method to measure the temperature of a magnetic sample. The approach relies on the intrinsic properties of the magnetic nanoparticles because it is based on monitoring the thermal dependence of the high order harmonic phases of the nanoparticle dynamic magnetization. The method is non-invasive and it does not need any additional probe or sensor attached to the magnetic nanoparticles. Moreover, this method has the potential to be used together with the magnetic particle imaging technique to map the spatial distribution of the temperature.

  3. Seismic probes of solar interior magnetic structure.

    PubMed

    Hanasoge, Shravan; Birch, Aaron; Gizon, Laurent; Tromp, Jeroen

    2012-09-07

    Sun spots are prominent manifestations of solar magnetoconvection, and imaging their subsurface structure is an outstanding problem of wide physical importance. Travel times of seismic waves that propagate through these structures are typically used as inputs to inversions. Despite the presence of strongly anisotropic magnetic waveguides, these measurements have always been interpreted in terms of changes to isotropic wave speeds and flow-advection-related Doppler shifts. Here, we employ partial-differential-equation-constrained optimization to determine the appropriate parametrization of the structural properties of the magnetic interior. Seven different wave speeds fully characterize helioseismic wave propagation: the isotropic sound speed, a Doppler-shifting flow-advection velocity, and an anisotropic magnetic velocity. The structure of magnetic media is sensed by magnetoacoustic slow and fast modes and Alfvén waves, each of which propagates at a different wave speed. We show that even in the case of weak magnetic fields, significant errors may be incurred if these anisotropies are not accounted for in inversions. Translation invariance is demonstrably lost. These developments render plausible the accurate seismic imaging of magnetoconvection in the Sun.

  4. Nanoscale Probe of Magnetism Based on Artificial Atoms in Diamond

    DTIC Science & Technology

    2014-07-18

    AFRL-OSR-VA-TR-2014-0165 (YIP 11) Nanoscale probe of magnetism based on artificial atoms in diamond Ania Bleszynski Jayich UNIVERSITY OF CALIFORNIA...06-30-2014 Final Report 04-01-2011 To 03-31-2014 Nanoscale probe of magnetism based on artificial atoms in diamond FA9550-11-1-0013 AFOSR-BAA-2010-3...sensing using a nitrogen-vacancy (NV) center in diamond . Significant accomplishments funded by this award include 1) characterization of the surface

  5. Mach Probe Wakes are Important in Weakly Magnetized, Collisional Plasmas

    NASA Astrophysics Data System (ADS)

    Gosselin, Jordan James; Thakur, Saikat; Sears, Stephanie; McKee, John; Scime, Earl; Tynan, George

    2015-11-01

    Mach probes are often used as the diagnostic for flow in the scrape off layer (SOL) of tokamaks and in linear devices because of their low cost and ease of construction. However, proper interpretation of the Mach number has been debated, and interpretation methods use different calibration factors for different plasma parameters. The Controlled Shear Decorrelation eXperiment (CSDX) operates in an intermediate magnetization regime. To validate theories in this regime, measurements of the parallel ion velocity were made with Mach probes and laser induced fluorescence (LIF) at magnetic fields from 400 to 1600 gauss. We find that Mach probe measurements indicate higher velocities than LIF at fields above 400 gauss. Reduced downstream plasma density due to probe shadowing is a strong candidate for the cause of the discrepancy. An advective-diffusive model for the geometric shadowing and downstream plasma density is presented. When the model for the density drop is included, the Mach probe results agree with the LIF data. This result should be included by groups using Mach probes to measure parallel velocities in plasmas where the ion-neutral mean free path is shorter than the probe shadow length, Lps = a2Cs /Dperp in linear devices, the SOL, or divertor region of tokamaks. This material is based upon work supported by the U.S. Department of Energy, Office of Science, under Awards Number DE-FG02-07ER54912.

  6. Probing of multiple magnetic responses in magnetic inductors using atomic force microscopy.

    PubMed

    Park, Seongjae; Seo, Hosung; Seol, Daehee; Yoon, Young-Hwan; Kim, Mi Yang; Kim, Yunseok

    2016-02-08

    Even though nanoscale analysis of magnetic properties is of significant interest, probing methods are relatively less developed compared to the significance of the technique, which has multiple potential applications. Here, we demonstrate an approach for probing various magnetic properties associated with eddy current, coil current and magnetic domains in magnetic inductors using multidimensional magnetic force microscopy (MMFM). The MMFM images provide combined magnetic responses from the three different origins, however, each contribution to the MMFM response can be differentiated through analysis based on the bias dependence of the response. In particular, the bias dependent MMFM images show locally different eddy current behavior with values dependent on the type of materials that comprise the MI. This approach for probing magnetic responses can be further extended to the analysis of local physical features.

  7. Probing of multiple magnetic responses in magnetic inductors using atomic force microscopy

    PubMed Central

    Park, Seongjae; Seo, Hosung; Seol, Daehee; Yoon, Young-Hwan; Kim, Mi Yang; Kim, Yunseok

    2016-01-01

    Even though nanoscale analysis of magnetic properties is of significant interest, probing methods are relatively less developed compared to the significance of the technique, which has multiple potential applications. Here, we demonstrate an approach for probing various magnetic properties associated with eddy current, coil current and magnetic domains in magnetic inductors using multidimensional magnetic force microscopy (MMFM). The MMFM images provide combined magnetic responses from the three different origins, however, each contribution to the MMFM response can be differentiated through analysis based on the bias dependence of the response. In particular, the bias dependent MMFM images show locally different eddy current behavior with values dependent on the type of materials that comprise the MI. This approach for probing magnetic responses can be further extended to the analysis of local physical features. PMID:26852801

  8. Magnetic probing of the solar interior

    NASA Technical Reports Server (NTRS)

    Benton, E. R.; Estes, R. H.

    1985-01-01

    The magnetic field patterns in the region beneath the solar photosphere is determined. An approximate method for downward extrapolation of line of sight magnetic field measurements taken at the solar photosphere was developed. It utilizes the mean field theory of electromagnetism in a form thought to be appropriate for the solar convection zone. A way to test that theory is proposed. The straightforward application of the lowest order theory with the complete model fit to these data does not indicate the existence of any reasonable depth at which flux conservation is achieved.

  9. Nanosatellite spin-up using magnetic actuators: ESTCube-1 flight results

    NASA Astrophysics Data System (ADS)

    Ehrpais, Hendrik; Kütt, Johan; Sünter, Indrek; Kulu, Erik; Slavinskis, Andris; Noorma, Mart

    2016-11-01

    This paper presents the in-orbit performance of the ESTCube-1 attitude control system that used electromagnetic actuators to achieve a high angular velocity. ESTCube-1 is a one-unit CubeSat that aimed to perform the first electric solar wind sail experiment. The attitude control system was designed to provide enough centrifugal force by spinning up the satellite to deploy a 10 m long tether. The required spin rate was a minimum of one rotation per second. The actuators used were three electromagnetic coils, each able to produce a magnetic moment of up to 0.1 A m2. In this paper, we describe the design of the attitude control system, implementation of the spin controller and the in-orbit performance of the system. In addition we describe the effect that a residual magnetic moment had on the attitude control of the satellite and the measures taken to overcome this issue. During testing of the satellite, ESTCube-1 achieved the highest known spin rate of 841°/s for small scale satellites. The satellite ended its operations on the 19th of May, 2015 after 2 years in orbit.

  10. Directed Fluid Flow Produced by Arrays of Magnetically Actuated Core-Shell Biomimetic Cilia

    NASA Astrophysics Data System (ADS)

    Fiser, B. L.; Shields, A. R.; Evans, B. A.; Superfine, R.

    2010-03-01

    We have developed a novel core-shell microstructure that we use to fabricate arrays of flexible, magnetically actuated biomimetic cilia. Our biomimetic cilia mimic the size and beat shape of biological cilia in order to replicate the transport of fluid driven by cilia in many biological systems including the determination of left-right asymmetry in the vertebrate embryonic nodal plate and mucociliary clearance in the lung. Our core-shell structures consist of a flexible poly(dimethylsiloxane) (PDMS) core surrounded by a shell of nickel approximately forty nanometers thick; by using a core-shell structure, we can tune the mechanical and magnetic properties independently. We present the fabrication process and the long-range transport that occurs above the beating biomimetic cilia tips and will report on progress toward biomimetic cilia induced flow in viscoelastic fluids similar to mucus in the human airway. These flows may have applications in photonics and microfluidics, and our structures may be further useful as sensors or actuators in microelectromechanical systems.

  11. In-plane cost-effective magnetically actuated valve for microfluidic applications

    NASA Astrophysics Data System (ADS)

    Pugliese, Marco; Ferrara, Francesco; Bramanti, Alessandro Paolo; Gigli, Giuseppe; Maiorano, Vincenzo

    2017-04-01

    We present a new in-plane magnetically actuated microfluidic valve. Its simple design includes a circular area joining two channels lying on the same plane. The area is parted by a septum lying on and adhering to a magneto-active polymeric ‘floor’ membrane, keeping the channels normally separated (valve closed). Under the action of a magnetic field, the membrane collapses, letting the liquid flow below the septum (valve open). The valve was extensively characterized experimentally, and modeled and optimized theoretically. The growing interest in lab on chips, especially for diagnostics and precision medicine, is driving researchers towards smart, efficient and low cost solutions to the management of biological samples. In this context, the valve developed in this work represents a useful building-block for microfluidic applications requiring precise flow control, its main features being easy and rapid manufacturing, biocompatibility and low cost.

  12. A magnetic probe equipped with small-tip permanent magnet for sentinel lymph node biopsy

    NASA Astrophysics Data System (ADS)

    Kaneko, Miki; Ohashi, Kaichi; Chikaki, Shinichi; Kuwahata, Akihiro; Shiozawa, Mikio; Kusakabe, Moriaki; Sekino, Masaki

    2017-05-01

    We previously developed a magnetic probe equipped with a ring-shaped permanent magnet for detecting magnetic nanoparticle tracer accumulating in the sentinel lymph nodes (SLNs). The magnetic probe enables us to identify SLNs objectively, without the risk of radiation exposure, unlike the conventional technique using dye and radioisotope. A technical challenge of the probe is to reduce the tip diameter of magnet to identify smaller SLNs. In this study, we optimized the size of smaller-tip magnet based on numerical analyses using the finite element method and evaluated the expected sensitivity. According to the analysis results, the optimum tip diameter and length of convex-shaped magnet were 16 mm and 12 mm, respectively. The experimental results showed that the sensitivity of the probe with smaller-tip magnet was comparable to the previous one. We successfully developed a smaller tip magnet, maintaining the sensitivity to magnetic nanoparticles. The proposed probe will be capable of identifying the location of SLNs more easily.

  13. Magnetically engineered semiconductor quantum dots as multimodal imaging probes.

    PubMed

    Jing, Lihong; Ding, Ke; Kershaw, Stephen V; Kempson, Ivan M; Rogach, Andrey L; Gao, Mingyuan

    2014-10-08

    Light-emitting semiconductor quantum dots (QDs) combined with magnetic resonance imaging contrast agents within a single nanoparticle platform are considered to perform as multimodal imaging probes in biomedical research and related clinical applications. The principles of their rational design are outlined and contemporary synthetic strategies are reviewed (heterocrystalline growth; co-encapsulation or assembly of preformed QDs and magnetic nanoparticles; conjugation of magnetic chelates onto QDs; and doping of QDs with transition metal ions), identifying the strengths and weaknesses of different approaches. Some of the opportunities and benefits that arise through in vivo imaging using these dual-mode probes are highlighted where tumor location and delineation is demonstrated in both MRI and fluorescence modality. Work on the toxicological assessments of QD/magnetic nanoparticles is also reviewed, along with progress in reducing their toxicological side effects for eventual clinical use. The review concludes with an outlook for future biomedical imaging and the identification of key challenges in reaching clinical applications.

  14. Performance of field measuring probes for SSC magnets

    SciTech Connect

    Thomas, R.; Ganetis, G.; Herrera, J.; Hogue, R.; Jain, A.; Louie, W.; Marone, A.; Wanderer, P.

    1993-12-31

    Several years of experience have been acquired on the operation of probes (``moles``) constructed for the measurement of the multipole components of the magnetic fields of SSC magnets. The field is measured by rotating coils contained in a 2.4-m long tube that is pulled through the aperture of the magnet by an external device-the transporter. In addition to the measuring coils, the tube contains motors for rotating the coil and a system for sensing local vertical using gravity sensors to provide an absolute reference for the field measurements. We describe the steps that must be taken in order to ensure accurate, repeatable measurements; the design changes that have been motivated by difficulties encountered (noise, vibration, variations in temperature); and other performance issues. The mechanical interface between the probe and the hewn tube of the magnet is also described.

  15. Magnetic Classification of Meteorites and Asteroid Probing

    NASA Astrophysics Data System (ADS)

    Rochette, P.; Sagnotti, L.; Chevrier, V.; Consolmagno, G.; Denise, M.; Folco, L.; Osete, M.; Pesonen, L.

    Magnetic susceptibility (X) provides a versatile rapid and non destructive way to quan- tify the amount of magnetic minerals (FeNi metal, magnetic oxides and sulfides) on large volume of material. As petrological studies of meteorites suggest that this param- eter should be quite discriminant, we assembled a database of measurements on about 1000 stony meteorites from various European collections: Helsinki, Madrid, Paris, Prague, Roma, Siena, Vatican, and other smaller collections. From 1 to >20 pieces and 1 to >100 cc per meteorite allow to define a representative mean value, using a large coil (8 cm) Kappabridge. For ordinary chondrites, it appears that weathering is responsible for a systematic bias toward low logc for Antarctic (Frontier Mountain) and non Antarctic (mainly from Sahara) finds. Once only falls are considered a quite narrow range of logc is observed for a given class, with no effect of petrological grade except for LL. High grade LLs (heated above 400C) develop the weakly magnetic antitaenite-tetrataenite phases [3] during slow cooling, explaining the difference with low grade taenite-bearing LLs. Outliers from H and L classes are grade 6 material (showing metal segregation) or intermediate types: H/L and L/LL. Once these out- liers are excluded, well defined means for H and L are observed with no overlap at 2 s.d.; this agrees with the lack of overlap on metal amount. The standard deviation for all falls of a given class is only slightly higher than the averaged standard deviation for multiple pieces of the same fall. This supports the hypothesis that all falls from a given ordinary chondrite class (H or L) may come from the same homogeneous par- ent body. For non ordinary chondrites and achondrites, weakly magnetic classes are HED, Aubrites and SNC (below LL), strongly ones are E (above H) and Ureilites (in the L-H range), while C chondrites are spread in the whole range, again with each class showing restricted variation. On objects without

  16. A bio-inspired inner-motile photocatalyst film: a magnetically actuated artificial cilia photocatalyst

    NASA Astrophysics Data System (ADS)

    Zhang, Dunpu; Wang, Wei; Peng, Fengping; Kou, Jiahui; Ni, Yaru; Lu, Chunhua; Xu, Zhongzi

    2014-04-01

    A new type of inner-motile photocatalyst film is explored to enhance photocatalytic performance using magnetically actuated artificial cilia. The inner-motile photocatalyst film is capable of generating flow and mixing on the microscale because it produces a motion similar to that of natural cilia when it is subjected to a rotational magnetic field. Compared with traditional photocatalyst films, the inner-motile photocatalyst film exhibits the unique ability of microfluidic manipulation. It uses an impactful and self-contained design to accelerate interior mass transfer and desorption of degradation species. Moreover, the special cilia-like structures increase the surface area and light absorption. Consequently, the photocatalytic activity of the inner-motile photocatalyst film is dramatically improved to approximately 3.0 times that of the traditional planar film. The inner-motile photocatalyst film also exhibits high photocatalytic durability and can be reused several times with ease. Furthermore, this feasible yet versatile platform can be extended to other photocatalyst systems, such as TiO2, P25, ZnO, and Co3O4 systems, to improve their photocatalytic performance.A new type of inner-motile photocatalyst film is explored to enhance photocatalytic performance using magnetically actuated artificial cilia. The inner-motile photocatalyst film is capable of generating flow and mixing on the microscale because it produces a motion similar to that of natural cilia when it is subjected to a rotational magnetic field. Compared with traditional photocatalyst films, the inner-motile photocatalyst film exhibits the unique ability of microfluidic manipulation. It uses an impactful and self-contained design to accelerate interior mass transfer and desorption of degradation species. Moreover, the special cilia-like structures increase the surface area and light absorption. Consequently, the photocatalytic activity of the inner-motile photocatalyst film is dramatically

  17. Probing Gravitational Sensitivity in Biological Systems Using Magnetic Body Forces

    NASA Technical Reports Server (NTRS)

    Guevorkian, Karine; Wurzel, Sam; Mihalusova, Mariana; Valles, Jim

    2003-01-01

    At Brown University, we are developing the use of magnetic body forces as a means to simulate variable gravity body forces on biological systems. This tool promises new means to probe gravi-sensing and the gravi-response of biological systems. It also has the potential as a technique for screening future systems for space flight experiments.

  18. Switchable bi-stable multilayer magnetic probes for imaging of soft magnetic structures.

    PubMed

    Wren, Tom; Puttock, Robb; Gribkov, Boris; Vdovichev, Sergey; Kazakova, Olga

    2017-03-28

    We present the use of custom-made multilayer (ML) magnetic probes in magnetic force microscopy (MFM) for imaging soft magnetic structures, i.e. nickel submicron disks of different dimensions. One of the main advantages of a custom-made ML probe is that it can be controllably switched between standard (parallel) and low moment (antiparallel) states. We demonstrate that the predicted vortex and stripe domain states in the disks are observed when using the ML probes both in the antiparallel and parallel states. However, while the phase contrast is significantly larger in the parallel state, the images are dominated by strong sample - probe interactions that obscure the image. By comparison of the stripe domain width observed by MFM with the ML probe and those expected from the Kittel model, we show that the resolution of the probe in the AP and P states is ∼30-40nm, i.e. of the order of the probe geometrical apex and thus approaching the limit of spatial resolution. The ML probes are further compared to the commercial standard and low moment ones, showing that the quality of images obtained with the ML probe is superior to both commercial probes.

  19. Magnetic Probe Construction using Thick-film Technology

    SciTech Connect

    Takahashi, H.; Sakakibara, S.; Kubota, Y.; and Yamada, H.

    2001-02-02

    Thick-film technology has been successfully adapted for the design and fabrication of magnetic probes of a new type suitable for use in the simultaneous ultra-high vacuum and high-temperature environment of a nuclear fusion device. The maximum usable temperature is expected to be around 900 degrees C. This new probe has a specific sensitivity (coupling area per unit volume) an order of magnitude higher than a conventional coil. The new probe in one implementation is capable of simultaneously measuring magnetic field in three orthogonal directions about a single spatial point and in two frequency ranges. Low-frequency coils have a measured coupling area of 296-323 cm squared and a frequency response of about 300 kHz. High-frequency coils have a design coupling area of 12-15 cm squared.

  20. Probing magnetic and electric optical responses of silicon nanoparticles

    SciTech Connect

    Permyakov, Dmitry; Sinev, Ivan; Markovich, Dmitry; Samusev, Anton; Belov, Pavel; Ginzburg, Pavel; Valuckas, Vytautas; Kuznetsov, Arseniy I.; Luk'yanchuk, Boris S.; Miroshnichenko, Andrey E.; Neshev, Dragomir N.; Kivshar, Yuri S.

    2015-04-27

    We study experimentally both magnetic and electric optically induced resonances of silicon nanoparticles by combining polarization-resolved dark-field spectroscopy and near-field scanning optical microscopy measurements. We reveal that the scattering spectra exhibit strong sensitivity of electric dipole response to the probing beam polarization and attribute the characteristic asymmetry of measured near-field patterns to the excitation of a magnetic dipole mode. The proposed experimental approach can serve as a powerful tool for the study of photonic nanostructures possessing both electric and magnetic optical responses.

  1. Development and Testing of a Magnetically Actuated Capsule Endoscopy for Obesity Treatment

    PubMed Central

    Do, Thanh Nho; Seah, Tian En Timothy; Yu, Ho Khek; Phee, Soo Jay

    2016-01-01

    Intra-gastric balloons (IGB) have become an efficient and less invasive method for obesity treatment. The use of traditional IGBs require complex insertion tools and flexible endoscopes to place and remove the balloon inside the patient’s stomach, which may cause discomfort and complications to the patient. This paper introduces a new ingestible weight-loss capsule with a magnetically remote-controlled inflatable and deflatable balloon. To inflate the balloon, biocompatible effervescent chemicals are used. As the source of the actuation is provided via external magnetic fields, the magnetic capsule size can be significantly reduced compared to current weight-loss capsules in the literature. In addition, there are no limitations on the power supply. To lose weight, the obese subject needs only to swallow the magnetic capsule with a glass of water. Once the magnetic capsule has reached the patient’s stomach, the balloon will be wirelessly inflated to occupy gastric space and give the feeling of satiety. The balloon can be wirelessly deflated at any time to allow the magnetic capsule to travel down the intestine and exit the body via normal peristalsis. The optimal ratio between the acid and base to provide the desired gas volume is experimentally evaluated and presented. A prototype capsule (9.6mm x 27mm) is developed and experimentally validated in ex-vivo experiments. The unique ease of delivery and expulsion of the proposed magnetic capsule is slated to make this development a good treatment option for people seeking to lose excess weight. PMID:26815309

  2. Magnetically Actuated Propellant Orientation, Controlling Fluids in a Low-Gravity Environment

    NASA Technical Reports Server (NTRS)

    Martin, James J.; Holt, James B.

    2000-01-01

    Cryogenic fluid management (CFM) is a technology area common to virtually every space transportation propulsion concept envisioned. Storage, supply, transfer and handling of sub-critical cryogenic fluids are basic capabilities that have long been needed by multiple programs and the need is expected to continue in the future. The use of magnetic fields provides another method, which could replace or augment current/traditional approaches, potentially simplifying vehicle operational constraints. The magnetically actuated propellant orientation (MAPO) program effort focused on the use of magnetic fields to control fluid motion as it relates to positioning (i.e. orientation and acquisition) of a paramagnetic substance such as LO2. Current CFM state- of-the-art systems used to control and acquire propellant in low gravity environments rely on liquid surface tension devices which employ vanes, fine screen mesh channels and baskets. These devices trap and direct propellant to areas where it's needed and have been used routinely with storable (non-cryogenic) propellants. However, almost no data exists r,egarding their operation in cryogenics and the use of such devices confronts designers with a multitude of significant technology issues. Typical problems include a sensitivity to screen dry out (due to thermal loads and pressurant gas) and momentary adverse accelerations (generated from either internal or external sources). Any of these problems can potentially cause the acquisition systems to ingest or develop vapor and fail. The use of lightweight high field strength magnets may offer a valuable means of augmenting traditional systems potentially mitigating or at least easing operational requirements. Two potential uses of magnetic fields include: 1) strategically positioning magnets to keep vent ports clear of liquid (enabling low G vented fill operations), and 2) placing magnets in the center or around the walls of the tank to create an insulating vapor pocket (between

  3. 3-D Localization Method for a Magnetically Actuated Soft Capsule Endoscope and Its Applications

    PubMed Central

    Yim, Sehyuk; Sitti, Metin

    2014-01-01

    In this paper, we present a 3-D localization method for a magnetically actuated soft capsule endoscope (MASCE). The proposed localization scheme consists of three steps. First, MASCE is oriented to be coaxially aligned with an external permanent magnet (EPM). Second, MASCE is axially contracted by the enhanced magnetic attraction of the approaching EPM. Third, MASCE recovers its initial shape by the retracting EPM as the magnetic attraction weakens. The combination of the estimated direction in the coaxial alignment step and the estimated distance in the shape deformation (recovery) step provides the position of MASCE in 3-D. It is experimentally shown that the proposed localization method could provide 2.0–3.7 mm of distance error in 3-D. This study also introduces two new applications of the proposed localization method. First, based on the trace of contact points between the MASCE and the surface of the stomach, the 3-D geometrical model of a synthetic stomach was reconstructed. Next, the relative tissue compliance at each local contact point in the stomach was characterized by measuring the local tissue deformation at each point due to the preloading force. Finally, the characterized relative tissue compliance parameter was mapped onto the geometrical model of the stomach toward future use in disease diagnosis. PMID:25383064

  4. Local magnetism in palladium bionanomaterials probed by muon spectroscopy.

    PubMed

    Creamer, Neil J; Mikheenko, Iryna P; Johnson, Clive; Cottrell, Stephen P; Macaskie, Lynne E

    2011-05-01

    Palladium bionanomaterial was manufactured using the sulfate-reducing bacterium, Desulfovibrio desulfuricansm, to reduce soluble Pd(II) ions to cell-bound Pd(0) in the presence of hydrogen. The biomaterial was examined using a Superconducting Quantum Interference Device (SQUID) to measure bulk magnetisation and by Muon Spin Rotation Spectroscopy (µSR) which is uniquely able to probe the local magnetic environment inside the sample. Results showed behaviour attributable to interaction of muons both with palladium electrons and the nuclei of hydrogen trapped in the particles during manufacture. Electronic magnetism, also suggested by SQUID, is not characteristic of bulk palladium and is consistent with the presence of nanoparticles previously seen in electron micrographs. We show the first use of μSR as a tool to probe the internal magnetic environment of a biologically-derived nanocatalyst material. © Springer Science+Business Media B.V. 2011

  5. Vacuum-actuated percutaneous insertion/implantation tool for flexible neural probes and interfaces

    DOEpatents

    Sheth, Heeral; Bennett, William J.; Pannu, Satinderpall S.; Tooker, Angela C.

    2017-03-07

    A flexible device insertion tool including an elongated stiffener with one or more suction ports, and a vacuum connector for interfacing the stiffener to a vacuum source, for attaching the flexible device such as a flexible neural probe to the stiffener during insertion by a suction force exerted through the suction ports to, and to release the flexible device by removing the suction force.

  6. Hysteresis Analysis and Positioning Control for a Magnetic Shape Memory Actuator

    PubMed Central

    Lin, Jhih-Hong; Chiang, Mao-Hsiung

    2015-01-01

    Magnetic shape memory alloys (MSM alloys), a new kind of smart materials, have become a potential candidate in many engineering fields. MSMs have the advantage of bearing a huge strain, much larger than other materials. In addition, they also have fast response. These characteristics make MSM a good choice in micro engineering. However, MSMs display the obvious hysteresis phenomenon of nonlinear behavior. Thus the difficulty in using the MSM element as a positioning actuator is increased due to the hysteresis. In this paper, the hysteresis phenomenon of the MSM actuator is analyzed, and the closed-loop positioning control is also implemented experimentally. For that, a modified fuzzy sliding mode control (MFSMC) is proposed. The MFSMC and the PID control are used to design the controllers for realizing the positioning control. The experimental results are compared under different experimental conditions, such as different frequency, amplitude, and loading. The experimental results show that the precise positioning control of MFSMC can be achieved satisfactorily. PMID:25853405

  7. Oil whip instability control using μ-synthesis technique on a magnetic actuator

    NASA Astrophysics Data System (ADS)

    Riemann, Bernd; Araujo Perini, Efrain; Lucchesi Cavalca, Katia; Fiori de Castro, Helio; Rinderknecht, Stephan

    2013-02-01

    Rotating machines have a wide application range and since those machines have high trust levels, several rotor vibrations control methods are investigated in order to avoid sudden cracks, improve rotor performance or even to reach higher operation speeds by controlling some instabilities, critical speeds resonances or oil whip effect. Rotor instabilities are associated to the operation speed and can have structural or dynamic sources from the shaft, bearings and foundation or even from an actuator external force. This work focuses on a strategy that uses the μ-synthesis control technique to attenuate the oil whip instability effect of flexible hydrodynamically supported rotors and allows the rotor to operate in higher speeds. For the identified rotor model and the synthesized controller applied on a magnetic actuator, the control system stability and performance specifications are analyzed with regard to the model uncertainties and μ-synthesis controlled vibration levels are compared to PID controller in vertical and horizontal directions. The performance specifications within the μ-synthesis are optimized to suppress unbalance vibration and, in order to contribute to industrial acceptance, the controller design is presented as a strategy which focuses on a design at reduced effort.

  8. A novel high amplitude piezoceramic actuator for applications in magnetic resonance elastography: a compliant mechanical amplifier approach

    NASA Astrophysics Data System (ADS)

    Arani, Arvin; Eskandari, Amiraslan; Ouyang, Puren; Chopra, Rajiv

    2017-08-01

    Piezoceramic actuators are capable of precise positioning with high force, but suffer from limited displacement range, which has hindered their application in the field of magnetic resonance elastography (MRE). The objective of this study was to investigate the feasibility of using a mechanical amplifier in combination with a piezoceramic actuator for the application of endorectal prostate MRE. A five-bar symmetric structure was designed in ANSYS® and manufactured out of brass. Laser vibrometer measurements were used to characterize the amplitude of the CMA actuator while attached to masses in the 0-325 g range and over operating frequencies of 90-500 Hz. The response of the CMA was investigated while mechanically coupled to a balloon type endorectal coil. The resonant frequency of the prototype CMA actuator was predicted within 10% error using ANSYS simulations. The amplification ratio of the CMA actuator was measured to be 10 with the laser vibrometer and 7.6 ± 1.7 (max: 9.2, min: 6.5) using MRE, at a vibration frequency of 200 Hz. Laser vibrometer data also showed that the CMA actuator’s performance did not change whether it was connected to an empty or inflated endorectal. The feasibility of performing endorectal prostate MRE with a CMA actuator was successfully demonstrated in a human volunteer.

  9. Comparison of magnetic probe calibration at nano and millitesla magnitudes.

    PubMed

    Pahl, Ryan A; Rovey, Joshua L; Pommerenke, David J

    2014-01-01

    Magnetic field probes are invaluable diagnostics for pulsed inductive plasma devices where field magnitudes on the order of tenths of tesla or larger are common. Typical methods of providing a broadband calibration of [Formula: see text] probes involve either a Helmholtz coil driven by a function generator or a network analyzer. Both calibration methods typically produce field magnitudes of tens of microtesla or less, at least three and as many as six orders of magnitude lower than their intended use. This calibration factor is then assumed constant regardless of magnetic field magnitude and the effects of experimental setup are ignored. This work quantifies the variation in calibration factor observed when calibrating magnetic field probes in low field magnitudes. Calibration of two [Formula: see text] probe designs as functions of frequency and field magnitude are presented. The first [Formula: see text] probe design is the most commonly used design and is constructed from two hand-wound inductors in a differential configuration. The second probe uses surface mounted inductors in a differential configuration with balanced shielding to further reduce common mode noise. Calibration factors are determined experimentally using an 80.4 mm radius Helmholtz coil in two separate configurations over a frequency range of 100-1000 kHz. A conventional low magnitude calibration using a vector network analyzer produced a field magnitude of 158 nT and yielded calibration factors of 15 663 ± 1.7% and 4920 ± 0.6% [Formula: see text] at 457 kHz for the surface mounted and hand-wound probes, respectively. A relevant magnitude calibration using a pulsed-power setup with field magnitudes of 8.7-354 mT yielded calibration factors of 14 615 ± 0.3% and 4507 ± 0.4% [Formula: see text] at 457 kHz for the surface mounted inductor and hand-wound probe, respectively. Low-magnitude calibration resulted in a larger calibration factor, with an average difference of 9.7% for the surface

  10. Comparison of magnetic probe calibration at nano and millitesla magnitudes

    NASA Astrophysics Data System (ADS)

    Pahl, Ryan A.; Rovey, Joshua L.; Pommerenke, David J.

    2014-01-01

    Magnetic field probes are invaluable diagnostics for pulsed inductive plasma devices where field magnitudes on the order of tenths of tesla or larger are common. Typical methods of providing a broadband calibration of dot{{B}} probes involve either a Helmholtz coil driven by a function generator or a network analyzer. Both calibration methods typically produce field magnitudes of tens of microtesla or less, at least three and as many as six orders of magnitude lower than their intended use. This calibration factor is then assumed constant regardless of magnetic field magnitude and the effects of experimental setup are ignored. This work quantifies the variation in calibration factor observed when calibrating magnetic field probes in low field magnitudes. Calibration of two dot{{B}} probe designs as functions of frequency and field magnitude are presented. The first dot{{B}} probe design is the most commonly used design and is constructed from two hand-wound inductors in a differential configuration. The second probe uses surface mounted inductors in a differential configuration with balanced shielding to further reduce common mode noise. Calibration factors are determined experimentally using an 80.4 mm radius Helmholtz coil in two separate configurations over a frequency range of 100-1000 kHz. A conventional low magnitude calibration using a vector network analyzer produced a field magnitude of 158 nT and yielded calibration factors of 15 663 ± 1.7% and 4920 ± 0.6% {T}/{V {s}} at 457 kHz for the surface mounted and hand-wound probes, respectively. A relevant magnitude calibration using a pulsed-power setup with field magnitudes of 8.7-354 mT yielded calibration factors of 14 615 ± 0.3% and 4507 ± 0.4% {T}/{V {s}} at 457 kHz for the surface mounted inductor and hand-wound probe, respectively. Low-magnitude calibration resulted in a larger calibration factor, with an average difference of 9.7% for the surface mounted probe and 12.0% for the hand-wound probe. The

  11. Analysis of magnetic field plasma interactions using microparticles as probes

    NASA Astrophysics Data System (ADS)

    Dropmann, Michael; Laufer, Rene; Herdrich, Georg; Matthews, Lorin S.; Hyde, Truell W.

    2015-08-01

    The interaction between a magnetic field and plasma close to a nonconductive surface is of interest for both science and technology. In space, crustal magnetic fields on celestial bodies without atmosphere can interact with the solar wind. In advanced technologies such as those used in fusion or spaceflight, magnetic fields can be used to either control a plasma or protect surfaces exposed to the high heat loads produced by plasma. In this paper, a method will be discussed for investigating magnetic field plasma interactions close to a nonconductive surface inside a Gaseous Electronics Conference reference cell employing dust particles as probes. To accomplish this, a magnet covered by a glass plate was exposed to a low power argon plasma. The magnetic field was strong enough to magnetize the electrons, while not directly impacting the dynamics of the ions or the dust particles used for diagnostics. In order to investigate the interaction of the plasma with the magnetic field and the nonconductive surface, micron-sized dust particles were introduced into the plasma and their trajectories were recorded with a high-speed camera. Based on the resulting particle trajectories, the accelerations of the dust particles were determined and acceleration maps over the field of view were generated which are representative of the forces acting on the particles. The results show that the magnetic field is responsible for the development of strong electric fields in the plasma, in both horizontal and vertical directions, leading to complex motion of the dust particles.

  12. Probing Magnetic Fields with Square Kilometre Array and its Precursors

    NASA Astrophysics Data System (ADS)

    Roy, Subhashis; Sur, Sharanya; Subramanian, Kandaswamy; Mangalam, Arun; Seshadri, T. R.; Chand, Hum

    2016-12-01

    Origin of magnetic fields, its structure and effects on dynamical processes in stars to galaxies are not well understood. Lack of a direct probe has remained a problem for its study. The first phase of Square Kilometre Array (SKA-I), will have almost an order of magnitude higher sensitivity than the best existing radio telescope at GHz frequencies. In this contribution, we discuss specific science cases that are of interest to the Indian community concerned with astrophysical turbulence and magnetic fields. The SKA-I will allow observations of a large number of background sources with detectable polarization and measure their Faraday depths (FDs) through the Milky Way, other galaxies and their circum-galactic mediums. This will probe line-of-sight magnetic fields in these objects well and provide field configurations. Detailed comparison of observational data (e.g., pitch angles in spirals) with models which consider various processes giving rise to field amplification and maintenance (e.g., various types of dynamo models) will then be possible. Such observations will also provide the coherence scale of the fields and its random component through RM structure function. Measuring the random component is important to characterize turbulence in the medium. Observations of FDs with redshift will provide important information on magnetic field evolution as a function of redshift. The background sources could also be used to probe magnetic fields and its coherent scale in galaxy clusters and in bridges formed between interacting galaxies. Other than FDs, sensitive observations of synchrotron emission from galaxies will provide complimentary information on their magnetic field strengths in the sky plane. The core shift measurements of AGNs can provide more precise measurements of magnetic field in the sub parsec region near the black hole and its evolution. The low band of SKA-I will also be useful to study circularly polarized emission from Sun and comparing various

  13. Mesoscale wide-bandwidth linear magnetic actuators : an LDRD final report.

    SciTech Connect

    Jones, Lawrence Anthony

    2004-02-01

    As MEMS transducers are scaled up in size, the threshold is quickly crossed to where magnetoquasistatic (MQS) transducers are superior for force production compared to electroquasistatic (EQS) transducers. Considerable progress has been made increasing the force output of MEMS EQS transducers, but progress with MEMS MQS transducers has been more modest. A key reason for this has been the difficulty implementing efficient lithographically-fabricated magnetic coil structures. The contribution of this study is a planar multilayer polyphase coil architecture which provides for the lithographic implementation of efficient stator windings suitable for linear magnetic machines. A millimeter-scale linear actuator with complex stator windings was fabricated using this architecture. The stators of the actuator were fabricated using a BCB/Cu process, which does not require replanarization of the wafer between layers. The prototype stator was limited to thin copper layers (3 {micro}m) due to the use of evaporated metal at the time of fabrication. Two layers of metal were implemented in the prototype, but the winding architecture naturally supports additional metal layer pairs. It was found in laboratory tests that the windings can support very high current densities of 4 x 10{sup 9}A/m{sup 2} without damage. Force production normal to the stator was calculated to be 0.54 N/A. For thin stators such as this one, force production increases approximately linearly with the thickness of the windings and a six-layer stator fabricated using a newly implemented electroplated BCB/Cu process (six layers of 15 {micro}m thick metal) is projected to produce approximately 8.8 N/A.

  14. [Targeted magnetic nanoparticles used as probe for magnetic resonance molecular imaging of tumor].

    PubMed

    Lu, Jing-Jing; Wang, Fang; Jin, Zheng-Yu; Zhong, Ding-Rong

    2009-04-01

    To investigate the feasibility of in vivo tumor detection using magnetic resonance (MR) molecular imaging with targeted magnetic nanoparticles as imaging probe. Targeted probe was synthesized by covalently linking the recombinant human gonadotropin releasing hormone analog (the targeting portion) with the ultrasmall superparamagnetic iron oxide nanoparticles (the imaging portion). The imaging portion served as the control material. The in vitro tumor cell experiment and the in vivo experiment using nude mice bearing tumors were carried out to test the targeting ability of the probe. In the in vitro experiment, the targeting probe and control materials were incubated separately with A549 cells which had high affinity to gonadotropin releasing hormone. Then the cells were taken out and lysed. The resultant solution was then subjected to MR imaging. The T2 value of the solutions was measured and compared. In the in vivo experiment, the targeting probe was administered into nude mice bearing A549 tumors. Dynamic MR imaging was carried out to measure the signal and T2 value of the tumor. The control material was also administered into control group of nude mice, and dynamic magnetic resonance imaging was performed. The T2 value of the tumor in both groups were recorded and compared. Both the in vitro and in vivo experiments proved the targeting ability of targeted probe. Compared with control material, the targeting probe had higher combining ability with tumor cells. MR molecular imaging of tumor can be realized by using targeting magnetic nanoparticles.

  15. Probing the magnetic topologies of magnetic clouds by means of solar energetic particles

    NASA Technical Reports Server (NTRS)

    Kahler, S. W.; Reames, D. V.

    1991-01-01

    Solar energetic particles (SEPs) have been used as probes of magnetic cloud topologies. The rapid access of SEPs to the interiors of many clouds indicates that the cloud field lines extend back to the sun and hence are not plasmoids. The small modulation of galactic cosmic rays associated with clouds also suggests that the magnetic fields of clouds are not closed.

  16. Effects of eddy currents due to a vacuum chamber wall in the airgap of a moving-magnet linear actuator

    SciTech Connect

    Jansen, J. W.; Lomonova, E. A.; Rovers, J. M. M.

    2009-04-01

    This paper discusses the effects of eddy currents induced in an electrically conducting plate which is placed in the airgap of a linear synchronous actuator with moving permanent magnets. The eddy currents induced in this plate, which is part of a controlled atmosphere chamber, cause not only damping but also deteriorate the actuator performance by disturbing the position measurement with Hall sensors. Furthermore, feed-forward controllers are less effective due to the suppression of high frequent armature fields. These effects are analyzed with an analytical model and verified with finite element simulations and measurements.

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

    SciTech Connect

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

    2015-04-15

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

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

    PubMed

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

    2015-04-01

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

  19. Novel magnetic heating probe for multimodal cancer treatment.

    PubMed

    Kan-Dapaah, Kwabena; Rahbar, Nima; Soboyejo, Wole

    2015-05-01

    Multifunctional materials consisting of polymers and magnetic nanoparticles (MNPs) are highly sought after in the field of biomedical engineering. These materials offer new opportunities for the development of novel cancer treatment modalities that can increase the efficacy of cancer therapy. In this paper, a novel probe for multimodal cancer treatment is proposed and analyzed. The probe is essentially a cannula with two main parts: a distal heat generating tip made of a magnetic nanocomposite and a proximal insulated shaft. A description of the concept and functional operations of the probe is presented. In an effort to assess its feasibility, the authors evaluated the ability of probe tip (made of PMMA-Fe3O4 nanocomposite) to generate heat in biological tissue using alternating magnetic field (AMF) parameters (field strength and frequency) that are acceptable for human use. Heat generation by MNPs was determined using the linear response theory. The effects of Fe3O4 volume fraction on heat generation as well as treatment time on the thermal dose were studied. The finite element method model was tested for its validity using an analytical model. Lesions were revealed to have an ellipsoidal shape and their sizes were affected by treatment time. However, their shapes remained unchanged. The comparison with the analytical model showed reasonably a good agreement to within 2%. Furthermore, the authors' numerical predictions also showed reasonable agreement with the experimental results previously reported in the literature. The authors' predictions demonstrate the feasibility of their novel probe to achieve reasonable lesion sizes, during hyperthermic or ablative heating using AMF parameters (field strength and frequency) that are acceptable for human use.

  20. A Magnetic Plethysmograph Probe for Local Pulse Wave Velocity Measurement.

    PubMed

    P M, Nabeel; Joseph, Jayaraj; Sivaprakasam, Mohanasankar

    2017-08-29

    We present the design and experimental validation of an arterial compliance probe with dual magnetic plethysmograph (MPG) transducers for local pulse wave velocity (PWV) measurement. The MPG transducers (positioned at 23 mm distance apart) utilizes Hall-effect sensors and permanent magnets for arterial blood pulse detection. The MPG probe was initially validated on an arterial flow phantom using a reference method. Further, 20 normotensive subjects (14 males, age = 24 ± 3.5 years) were studied under two different physical conditions: 1) Physically relaxed condition, 2) Postexercise condition. Local PWV was measured from the left carotid artery using the MPG probe. Brachial blood pressure (BP) was measured to investigate the correlation of BP with local PWV. The proposed MPG arterial compliance probe was capable of detecting high-fidelity blood pulse waveforms. Reliable local pulse transit time estimates were assessed by the developed measurement system. Beat-by-beat local PWV was measured from multiple subjects under different physical conditions. A profound increment was observed in the carotid local PWV for all subjects after exercise (average increment = 0.42 ± 0.22 m/s). Local PWV values and brachial BP parameters were significantly correlated (r ≥ 0.72), except for pulse pressure (r = 0.42). MPG arterial compliance probe for local PWV measurement was validated. Carotid local PWV measurement, its variations due to physical exercise and correlation with BP levels were examined during the in vivo study. A novel dual MPG probe for local PWV measurement and potential use in cuffless BP measurement.

  1. Modeling drug release from functionalized magnetic nanoparticles actuated by non-heating low frequency magnetic field

    NASA Astrophysics Data System (ADS)

    Golovin, Y.; Golovin, D.; Klyachko, N.; Majouga, A.; Kabanov, A.

    2017-02-01

    Various plausible acceleration mechanisms of drug release from nanocarriers composed of a single-domain magnetic nanoparticle core with attached long macromolecule chains activated by low frequency non-heating alternating magnetic field (AMF) are discussed. The most important system characteristics affecting the AMF exposure impact are determined. Impact of several reasonable mechanisms is estimated analytically or obtained using numerical modeling. Some conditions providing manifold release acceleration as a result from exposure in AMF are found.

  2. Theranostic multimodal potential of magnetic nanoparticles actuated by non-heating low frequency magnetic field in the new-generation nanomedicine

    NASA Astrophysics Data System (ADS)

    Golovin, Yuri I.; Klyachko, Natalia L.; Majouga, Alexander G.; Sokolsky, Marina; Kabanov, Alexander V.

    2017-02-01

    The scope of this review involves one of the most promising branches of new-generation biomedicine, namely magnetic nanotheranostics using remote control of functionalized magnetic nanoparticles (f-MNPs) by means of alternating magnetic fields (AMFs). The review is mainly focused on new approach which utilizes non-heating low frequency magnetic fields (LFMFs) for nanomechanical actuation of f-MNPs. This approach is compared to such traditional ones as magnetic resonance imaging (MRI) and radio-frequency (RF) magnetic hyperthermia (MH) which utilize high frequency heating AMF. The innovative principles and specific models of non-thermal magnetomechanical actuation of biostructures by MNP rotational oscillations in LFMF are described. The discussed strategy allows biodistribution monitoring in situ, delivering drugs to target tissues and releasing them with controlled rate, controlling biocatalytic reaction kinetics, inducing malignant cell apoptosis, and more. Optimization of both LFMF and f-MNP parameters may lead to dramatic improvement of treatment efficiency, locality, and selectivity on molecular or cellular levels and allow implementing both drug and drugless, i.e., pure nanomechanical therapy, in particular cancer therapy. The optimal parameters within this approach differ significantly from those used in MH or MRI because of the principal difference in the f-MNP actuation modes. It is shown that specifically designed high gradient, steady magnetic field enables diagnostic and therapeutic LFMF impact localization in the deep tissues within the area ranging from a millimeter to a few centimeters and 3D scanning of affected region, if necessary.

  3. A light-induced spin crossover actuated single-chain magnet

    NASA Astrophysics Data System (ADS)

    Liu, Tao; Zheng, Hui; Kang, Soonchul; Shiota, Yoshihito; Hayami, Shinya; Mito, Masaki; Sato, Osamu; Yoshizawa, Kazunari; Kanegawa, Shinji; Duan, Chunying

    2013-11-01

    Both spin-crossover complexes and molecular nanomagnets display bistable magnetic states, potentially behaving as elementary binary units for information storage. It is a challenge to introduce spin-crossover units into molecular nanomagnets to switch the bistable state of the nanomagnets through external stimuli-tuned spin crossover. Here we report an iron(II) spin-crossover unit and paramagnetic iron(III) ions that are incorporated into a well-isolated double-zigzag chain. The chain exhibits thermally induced reversible spin-crossover and light-induced excited spin-state trapping at the iron(II) sites. Single-chain magnet behaviour is actuated accompanying the synergy between light-induced excited spin-state trapping at the iron(II) sites and ferromagnetic interactions between the photoinduced high-spin iron(II) and low-spin iron(III) ions in the chain. The result provides a strategy to switch the bistable state of molecular nanomagnets using external stimuli such as light and heat, with the potential to erase and write information at a molecular level.

  4. A bio-inspired inner-motile photocatalyst film: a magnetically actuated artificial cilia photocatalyst.

    PubMed

    Zhang, Dunpu; Wang, Wei; Peng, Fengping; Kou, Jiahui; Ni, Yaru; Lu, Chunhua; Xu, Zhongzi

    2014-05-21

    A new type of inner-motile photocatalyst film is explored to enhance photocatalytic performance using magnetically actuated artificial cilia. The inner-motile photocatalyst film is capable of generating flow and mixing on the microscale because it produces a motion similar to that of natural cilia when it is subjected to a rotational magnetic field. Compared with traditional photocatalyst films, the inner-motile photocatalyst film exhibits the unique ability of microfluidic manipulation. It uses an impactful and self-contained design to accelerate interior mass transfer and desorption of degradation species. Moreover, the special cilia-like structures increase the surface area and light absorption. Consequently, the photocatalytic activity of the inner-motile photocatalyst film is dramatically improved to approximately 3.0 times that of the traditional planar film. The inner-motile photocatalyst film also exhibits high photocatalytic durability and can be reused several times with ease. Furthermore, this feasible yet versatile platform can be extended to other photocatalyst systems, such as TiO2, P25, ZnO, and Co3O4 systems, to improve their photocatalytic performance.

  5. Electrically driven magnetization of diluted magnetic semiconductors actuated by the Overhauser effect.

    PubMed

    Siddiqui, L; Zainuddin, A N M; Datta, S

    2010-06-02

    It is well known that the Curie temperature, and hence the magnetization, in diluted magnetic semiconductors (DMS) like Ga(1-x)Mn(x)As can be controlled by changing the equilibrium density of holes in the material. Here, we propose that even with a constant hole density, large changes in the magnetization can be obtained with a relatively small imbalance in the quasi-Fermi levels for up-spin and down-spin electrons. We show, by coupling the mean field theory of diluted magnetic semiconductor ferromagnetism with master equations governing the Mn spin-dynamics, that a mere splitting of the up-spin and down-spin quasi-Fermi levels by 0.1 meV will produce the effect of an external magnetic field as large as 1 T as long as the alternative relaxation paths for Mn spins (i.e. spin-lattice relaxation) can be neglected. The physics is similar to the classic Overhauser effect, also called the dynamic nuclear polarization, with the Mn impurities playing the role of the nucleus. We propose that a lateral spin-valve structure in an anti-parallel configuration with a DMS as the channel can be used to demonstrate this effect, as quasi-Fermi level splitting of such magnitude, inside the channel of similar systems, has already been experimentally demonstrated to produce polarization of paramagnetic impurity spins.

  6. Permanent magnets as biasing mechanism for improving the performance of circular dielectric elastomer out-of-plane actuators

    NASA Astrophysics Data System (ADS)

    Loew, P.; Rizzello, G.; Seelecke, S.

    2017-04-01

    Dielectric Elastomers (DE) represent an attractive technology for the realization of mechatronic actuators, due to their lightweight, high energy density, high energy efficiency, scalability, and low noise features. In order to produce a stroke, a DE membrane needs to be pre-loaded with a mechanical biasing mechanism. In our previous works, we compared the stroke achieved with different biasing mechanisms for a circular out-of-plane DE Actuator (DEA), i.e., hanging masses, linear and bi-stable springs. The novel contribution of this paper is the investigation of a biasing design approach based on permanent magnets. The resulting magnet-based actuators are usually more compact than the spring-based ones, allowing to obtain more compact systems. Two design solutions are proposed and compared, namely a first one characterized by a stable actuation, and a second one which permits to achieve a higher stroke, but it is intrinsically unstable. The effectiveness of the novel design solution is assessed by means of several experiments.

  7. Matched dipole probe for precise electron density measurements in magnetized and non-magnetized plasmas

    NASA Astrophysics Data System (ADS)

    Rafalskyi, Dmytro; Aanesland, Ane

    2015-09-01

    We present a plasma diagnostics method based on impedance measurements of a short matched dipole placed in the plasma. This allows measuring the local electron density in the range from 1012-1015 m-3 with a magnetic field of at least 0-50 mT. The magnetic field strength is not directly influencing the data analysis and requires only that the dipole probe is oriented perpendicularly to the magnetic field. As a result, the magnetic field can be non-homogeneous or even non-defined within the probe length without any effect on the final tolerance of the measurements. The method can be applied to plasmas of relatively small dimensions (< 10 cm) and doesn't require any special boundary conditions. The high sensitivity of the impedance measurements is achieved by using a miniature matching system installed close to the probe tip, which also allows to suppress sheath resonance effects. We experimentally show here that the tolerance of the electron density measurements reaches values lower than 1%, both with and without the magnetic field. The method is successfully validated by both analytical modeling and experimental comparison with Langmuir probes. The validation experiments are conducted in a low pressure (1 mTorr) Ar discharge sustained in a 10 cm size plasma chamber with and without a transversal magnetic field of about 20 mT. This work was supported by a Marie Curie International Incoming Fellowships within FP7 (NEPTUNE PIIF-GA-2012-326054).

  8. Scanning Hall probe microscopy of a diluted magnetic semiconductor

    SciTech Connect

    Kweon, Seongsoo; Samarth, Nitin; Lozanne, Alex de

    2009-05-01

    We have measured the micromagnetic properties of a diluted magnetic semiconductor as a function of temperature and applied field with a scanning Hall probe microscope built in our laboratory. The design philosophy for this microscope and some details are described. The samples analyzed in this work are Ga{sub 0.94}Mn{sub 0.06}As films grown by molecular beam epitaxy. We find that the magnetic domains are 2-4 mum wide and fairly stable with temperature. Magnetic clusters are observed above T{sub C}, which we ascribe to MnAs defects too small and sparse to be detected by a superconducting quantum interference device magnetometer.

  9. Active control of surge in centrifugal compressors using magnetic thrust bearing actuation

    NASA Astrophysics Data System (ADS)

    Sanadgol, Dorsa

    This research presents a new method for active surge control in centrifugal compressors with unshrouded impellers using a magnetic thrust bearing to modulate the impeller tip clearance. Magnetic bearings offer the potential for active control of flow instabilities. This capability is highly dependent on the sensitivity of the compressor characteristics to blade tip clearance. If the position of the shaft can be actuated with sufficient authority and speed, the induced pressure modulation makes control of surge promising. The active nature of the magnetic bearing system makes the real-time static and dynamic positioning of the rotor and therefore modulation of the impeller tip clearance possible. A theoretical model is first established that describes the sensitivity of the centrifugal compressor characteristic curve to tip clearance variations induced by axial motion of the rotor. Results from simulation of the nonlinear model for a single stage high-speed centrifugal compressor show that using the proposed control method, mass flow and pressure oscillations associated with compressor surge are quickly suppressed with acceptable tip clearance excursions, typically less than 20% of the available clearance. It is shown that it is possible to produce adequate axial excursions in the clearance between the impeller blades and the adjacent stationary shroud using a magnetic thrust bearing with practical levels of drive voltage. This surge control method would allow centrifugal compressors to reliably and safely operate with a wider range than is currently done in the field. The principal advantage of the proposed approach over conventional surge control methods lies in that, in machines already equipped with magnetic bearing, the method can potentially be implemented by simply modifying controller software. This dispenses with the need to introduce additional hardware, permitting adaptation of existing machinery at virtually no cost. In addition, since the controller is

  10. Electro-magnetically Actuated Minute Polymer Pump Fabricated using Packaging Technology

    NASA Astrophysics Data System (ADS)

    Balaji, G.; Singh, A.; Ananthasuresh, G. K.

    2006-04-01

    Design, fabrication and preliminary testing of a flat pump with millimetre thickness are described in this paper. The pump is entirely made of polymer materials barring the magnet and copper coils used for electromagnetic actuation. The fabrication is carried out using widely available microelectronic packaging machinery and techniques. Therefore, the fabrication of the pump is straightforward and inexpensive. Two types of prototypes are designed and built. One consists of copper coils that are etched on an epoxy plate and the other has wound insulated wire of 90 µm diameter to serve as a coil. The overall size of the first pump is 25 mm × 25 mm × 3.6 mm including the 3.1 mm-thick NdFeB magnet of diameter 12 mm. It consists of a pump chamber of 20 mm × 20 mm × 0.8 mm with copper coils etched from a copper-clad epoxy plate using dry-film lithography and milled using a CNC milling machine, two passive valves and the pump-diaphragm made of Kapton film of 0.089 mm thickness. The second pump has an overall size of 35 mm × 35 mm × 4.4 mm including the magnet and the windings. A breadboard circuit and DC power supply are used to test the pump by applying an alternating square-wave voltage pulse. A water slug in a tube attached to the inlet is used to observe and measure the air-flow induced by the pump against atmospheric pressure. The maximum flow rate was found to be 15 ml/min for a voltage of 2.5 V and a current of 19 mA at 68 Hz.

  11. Mapping magnetism with atomic resolution using aberrated electron probes

    NASA Astrophysics Data System (ADS)

    Idrobo, Juan; Rusz, Ján; McGuire, Michael A.; Symons, Christopher T.; Vatsavai, Ranga Raju; Lupini, Andrew R.

    2015-03-01

    In this talk, we report a direct experimental real-space mapping of magnetic circular dichroism with atomic resolution in aberration-corrected scanning transmission electron microscopy (STEM). Using an aberrated electron probe with customized phase distribution, we reveal with electron energy-loss (EEL) spectroscopy the checkerboard antiferromagnetic ordering of Mn moments in LaMnAsO by observing a dichroic signal in the Mn L-edge. The aberrated probes allow the collection of EEL spectra using the transmitted beam, which results in a magnetic circular dichroic signal with intrinsically larger signal-to-noise ratios than those obtained via nanodiffraction techniques (where most of the transmitted electrons are discarded). The novel experimental setup presented here, which can easily be implemented in aberration-corrected STEM, opens new paths for probing dichroic signals in materials with unprecedented spatial resolution. This research was supported by DOE SUFD MSED, by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the US DOE, and by the Swedish Research Council and Swedish National Infrastructure for Computing (NSC center)

  12. A multichannel magnetic probe system for analysing magnetic fluctuations in helical axis plasmas

    SciTech Connect

    Haskey, S. R.; Blackwell, B. D.; Seiwald, B.; Hole, M. J.; Pretty, D. G.; Howard, J.; Wach, J.

    2013-09-15

    The need to understand the structure of magnetic fluctuations in H-1NF heliac [S. Hamberger et al., Fusion Technol. 17, 123 (1990)] plasmas has motivated the installation of a sixteen former, tri-axis helical magnetic probe Mirnov array (HMA). The new array complements two existing poloidal Mirnov arrays by providing polarisation information, higher frequency response, and improved toroidal resolution. The helical placement is ideal for helical axis plasmas because it positions the array as close as possible to the plasma in regions of varying degrees of favourable curvature in the magnetohydrodynamic sense, but almost constant magnetic angle. This makes phase variation with probe position near linear, greatly simplifying the analysis of the data. Several of the issues involved in the design, installation, data analysis, and calibration of this unique array are presented including probe coil design, frequency response measurements, mode number identification, orientation calculations, and mapping probe coil positions to magnetic coordinates. Details of specially designed digitally programmable pre-amplifiers, which allow gains and filters to be changed as part of the data acquisition initialisation sequence and stored with the probe signals, are also presented. The low shear heliac geometry [R. Jiménez-Gómez et al., Nucl. Fusion 51, 033001 (2011)], flexibility of the H-1NF heliac, and wealth of information provided by the HMA create a unique opportunity for detailed study of Alfvén eigenmodes, which could be a serious issue for future fusion reactors.

  13. Probing neutrino magnetic moments at the Spallation Neutron Source facility

    NASA Astrophysics Data System (ADS)

    Kosmas, T. S.; Miranda, O. G.; Papoulias, D. K.; Tórtola, M.; Valle, J. W. F.

    2015-07-01

    Majorana neutrino electromagnetic properties are studied through neutral current coherent neutrino-nucleus scattering. We focus on the potential of the recently planned COHERENT experiment at the Spallation Neutron Source to probe muon-neutrino magnetic moments. The resulting sensitivities are determined on the basis of a χ2 analysis employing realistic nuclear structure calculations in the context of the quasiparticle random phase approximation. We find that they can improve existing limits by half an order of magnitude. In addition, we show that these facilities allow for standard model precision tests in the low energy regime, with a competitive determination of the weak mixing angle. Finally, they also offer the capability to probe other electromagnetic neutrino properties, such as the neutrino charge radius. We illustrate our results for various choices of experimental setup and target material.

  14. Simulation studies of a novel electromagnetic actuation scheme for focusing magnetic micro/nano-carriers into a deep target region

    NASA Astrophysics Data System (ADS)

    Le, Tuan-Anh; Zhang, Xingming; Hoshiar, Ali Kafash; Kim, Myeong Ok; Yoon, Jungwon

    2017-05-01

    The ability to focus spherical particles (SPPs) to a deep tumor region remains one of the major challenges in magnetic drug targeting (MDT). A number of studies have attempted to overcome this problem using fast magnetic pulses and ferromagnetic rods. However, focusing of the SPPs in the deep body organs remains unsolved using existing schemes. In this paper, we propose a novel electro-magnetic actuation scheme for pushing and focusing SPPs. The simulation results demonstrate that the newly proposed actuation scheme can focus SPPs to a target surface region, inside of a block filled with an environment that has the characteristics of blood. We then investigated the effects of the proposed focusing scheme in realistic blood vessels with a maximum length of about 10-12 cm. The results show that SPPs of 500 nm can be concentrated onto a target tumor region with up to 97.9% efficiency. The proposed electromagnetic actuation scheme can maximize the efficiency of MDT, while minimizing the side effects of drugs in other tissues.

  15. Determination of forces in a magnetic bearing actuator - Numerical computation with comparison to experiment

    NASA Technical Reports Server (NTRS)

    Knight, J. D.; Xia, Z.; Mccaul, E.; Hacker, H., Jr.

    1992-01-01

    Calculations of the forces exerted on a journal by a magnetic bearing actuator are presented, along with comparisons to experimentally measured forces. The calculations are based on two-dimensional solutions for the flux distribution in the metal parts and free space, using finite but constant permeability in the metals. Above a relative permeability of 10,000 the effects of changes in permeability are negligible, but below 10,000 decreases in permeability cause significant decreases in the force. The calculated forces are shown to depend on the metal permeability more strongly when the journal is displaced from its centered position. The predicted forces in the principal attractive direction are in good agreement with experiment when a relatively low value of permeability is chosen. The forces measured normal to the axis of symmetry when the journal is displaced from that axis, however, are significantly higher than predicted by theory, even with a value of relative permeability larger than 5000. These results indicate a need for further work including nonlinear permeability distributions.

  16. Determination of forces in a magnetic bearing actuator - Numerical computation with comparison to experiment

    NASA Technical Reports Server (NTRS)

    Knight, J. D.; Xia, Z.; Mccaul, E.; Hacker, H., Jr.

    1992-01-01

    Calculations of the forces exerted on a journal by a magnetic bearing actuator are presented, along with comparisons to experimentally measured forces. The calculations are based on two-dimensional solutions for the flux distribution in the metal parts and free space, using finite but constant permeability in the metals. Above a relative permeability of 10,000 the effects of changes in permeability are negligible, but below 10,000 decreases in permeability cause significant decreases in the force. The calculated forces are shown to depend on the metal permeability more strongly when the journal is displaced from its centered position. The predicted forces in the principal attractive direction are in good agreement with experiment when a relatively low value of permeability is chosen. The forces measured normal to the axis of symmetry when the journal is displaced from that axis, however, are significantly higher than predicted by theory, even with a value of relative permeability larger than 5000. These results indicate a need for further work including nonlinear permeability distributions.

  17. Voltage-Driven In-Plane Magnetization Easy Axis Switching in FeNi/Piezoelectric Actuator Hybrid Structure

    NASA Astrophysics Data System (ADS)

    Xi, Li; Guo, Xiaobin; Wang, Zhen; Li, Yue; Yao, Yuelin; Zuo, Yalu; Xue, Desheng

    2013-01-01

    FeNi thin films with the in-plane uniaxial anisotropy were fabricated by direct current magnetron sputtering. An FeNi/piezoelectric actuator hybrid structure was used to investigate the voltage-controlled magnetization switching. A theoretical calculation was performed to provide a simplified vision of the magnetoelastic contribution to the magnetic anisotropy. Magneto-optical Kerr effect measurements were performed and the rotation of the magnetization easy axis in the FeNi film upon application of a voltage with or without the application of a magnetic field was demonstrated. A film-thickness dependent in-plane magnetization easy axis rotation angle was observed and explained by the variation of the magnetostriction.

  18. Parameter estimation and actuator characteristics of hybrid magnetic bearings for axial flow blood pump applications.

    PubMed

    Lim, Tau Meng; Cheng, Shanbao; Chua, Leok Poh

    2009-07-01

    Axial flow blood pumps are generally smaller as compared to centrifugal pumps. This is very beneficial because they can provide better anatomical fit in the chest cavity, as well as lower the risk of infection. This article discusses the design, levitated responses, and parameter estimation of the dynamic characteristics of a compact hybrid magnetic bearing (HMB) system for axial flow blood pump applications. The rotor/impeller of the pump is driven by a three-phase permanent magnet brushless and sensorless motor. It is levitated by two HMBs at both ends in five degree of freedom with proportional-integral-derivative controllers, among which four radial directions are actively controlled and one axial direction is passively controlled. The frequency domain parameter estimation technique with statistical analysis is adopted to validate the stiffness and damping coefficients of the HMB system. A specially designed test rig facilitated the estimation of the bearing's coefficients in air-in both the radial and axial directions. Experimental estimation showed that the dynamic characteristics of the HMB system are dominated by the frequency-dependent stiffness coefficients. By injecting a multifrequency excitation force signal onto the rotor through the HMBs, it is noticed in the experimental results the maximum displacement linear operating range is 20% of the static eccentricity with respect to the rotor and stator gap clearance. The actuator gain was also successfully calibrated and may potentially extend the parameter estimation technique developed in the study of identification and monitoring of the pump's dynamic properties under normal operating conditions with fluid.

  19. In Situ control and modification of the probe magnetization state for accurate magnetic force microscopy

    NASA Astrophysics Data System (ADS)

    Angeloni, Livia; Passeri, Daniele; Natali, Marco; Reggente, Melania; Anelli, Emanuele; Bettucci, Andrea; Mantovani, Diego; Rossi, Marco

    2017-08-01

    Electrostatic tip-sample interactions currently represent the main limitation to accurate quantitative analysis of magnetic force microscopy (MFM) data. Controlled magnetization MFM (CM-MFM) represents a smart solution to overcome this limitation as it allows one to identify electrostatic artifacts and to subtract them from standard MFM images, thus enabling the quantitative investigation of magnetic properties of materials at the nanometer scale. CM-MFM, however, requires not only the magnetization, but also the in situ accurate demagnetization of the MFM probe. In particular, the latter represents a crucial step for the complete removal of electrostatic artifacts. In this work, we describe two different methods to depolarize the MFM tip, based on the application of the coercive remanent magnetic field of the tip and on a damped alternating magnetic field, respectively. The two techniques are escribed and compared to emphasize their specific advantages and limitations.

  20. An Electrolyte-Free Conducting Polymer Actuator that Displays Electrothermal Bending and Flapping Wing Motions under a Magnetic Field.

    PubMed

    Uh, Kyungchan; Yoon, Bora; Lee, Chan Woo; Kim, Jong-Man

    2016-01-20

    Electroactive materials that change shape in response to electrical stimulation can serve as actuators. Electroactive actuators of this type have great utility in a variety of technologies, including biomimetic artificial muscles, robotics, and sensors. Electroactive actuators developed to date often suffer from problems associated with the need to use electrolytes, slow response times, high driving voltages, and short cycle lifetimes. Herein, we report an electrolyte-free, single component, polymer electroactive actuator, which has a fast response time, high durability, and requires a low driving voltage (<5 V). The process employed for production of this material involves wet-spinning of a preorganized camphorsulfonic acid (CSA)-doped polyaniline (PANI) gel, which generates long, flexible, and conductive (∼270 S/cm) microfibers. Reversible bending motions take place upon application of an alternating current (AC) to the PANI polymer. This motion, promoted by a significantly low driving voltage (<0.5 V) in the presence of an external magnetic field, has a very large swinging speed (9000 swings/min) that lies in the range of those of flies and bees (1000-15000 swings/min) and is fatigue-resistant (>1000000 cycles).

  1. A probe for measuring current density during magnetic stimulation.

    PubMed

    Tay, G; Chilbert, M A; Battocletti, J; Sances, A; Swiontek, T

    1991-01-01

    Time-varying magnetic fields induce currents in conductive media, and when the induced current is large enough in excitable tissue, stimulation occurs. This phenomenon has been applied to the human brain and peripheral nerves for diagnostic evaluation of the neural system. One important aspect that is presently unknown is the current level necessary in tissue for stimulation induced by magnetic fields. This study presents a method of measuring the induced current density from pulsed magnetic fields in vitro and in vivo. The current-density probe was inserted into three concentrations of saline and into the brains of ten anesthetized cats. Two stimulation systems with coils 9 cm and 5 cm in diameter were used. The two systems provided sinusoidal and pulsatile coil currents. Measurements made in saline were compared with those calculated theoretically for a semi-infinite medium. The measured values were within 5% of the calculated values. Measurements made in the cat brain showed a 67% decrease compared with the theoretic model. This variance is attributed to the finite bounds of the skull. The results indicate that direct measurement of current density is possible. Subsequent measurements will aid in the design of improved magnetic stimulation systems.

  2. Characteristics of magnetic force microscopy magnetics on high moment perpendicular magnetic recording writers with high coercivity probes

    NASA Astrophysics Data System (ADS)

    Liu, Feng; Li, Shaoping; Bai, Daniel; Wang, James; Li, Zhanjie; Han, Dehua; Pan, Tao; Mao, Sining

    2012-04-01

    High resolution magnetic force microscopy (MFM) imaging with high coercivity probes on perpendicular magnetic recording (PMR) writers directly characterizes magnetic field contour for the writer main pole as well as its shields' magnetic state. Evolution of write bubble and return field was analyzed by MFM imaging in dynamic phase detection scheme. Different write field components and their out of plane second order derivatives were calculated via finite element modeling. The MFM imaged write field distribution correlates well with the PMR writer out of plane write field component. Magnetic responses of the PMR writer main pole, trailing and side shields are quantified. The trailing and side shields exhibit complicated magnetic saturation behaviors comparing with the PMR writer pole. The side shield's magnetic response is dependent upon its initial equilibrium state.

  3. Toxoplasma gondii DNA detection with a magnetic molecular beacon probe

    NASA Astrophysics Data System (ADS)

    Xu, Shichao; Yao, Cuicui; Wei, Shuoming; Zhang, Jimei; Dai, Zhao; Zheng, Guo; Sun, Bo; Han, Qing; Hu, Fei; Zhou, Hongming

    2008-12-01

    Toxoplasma Gondii infection is widespread in humans worldwide and reported infection rates range from 3%-70%, depending on the populations or geographic areas, and it has been recognized as a potential food safety hazard in our daily life. A magnetic molecular beacon probe (mMBP), based on theory of fluorescence resonance energy transfer (FRET), was currently reported to detect Toxoplasma Gondii DNA. Nano-sized Fe3O4 were primarily prepared by coprecipitation method in aqueous phase with NaOH as precipitator, and was used as magnetic core. The qualified coreshell magnetic quantum dots (mQDs), i.e. CdTe(symbol)Fe3O4, were then achieved by layer-by-layer method when mol ratio of Fe3O4/CdTe is 1/3, pH at 6.0, 30 °C, and reactant solution was refluxed for 30 min, the size of mQDs were determined to be 12-15 nm via transmission electron microscopy (TEM). Over 70% overlap between emission spectrum of mQDs and absorbance spectrum of BHQ-2 was observed, this result suggests the synthesized mQDs and BHQ-2 can be utilized as energy donor and energy acceptor, respectively. The sensing probe was fabricated and a stem-loop Toxoplasma Gondii DNA oligonucleotide was labeled with mQDs at the 5' end and BHQ-2 at 3' end, respectively. Target Toxoplasma gondii DNA was detected under conditions of 37 °C, hybridization for 2h, at pH8.0 in Tris-HCl buffer. About 30% recovery of fluorescence intensity was observed via fluorescence spectrum (FS) after the Toxoplasma gondii DNA was added, which suggested that the Toxoplasma Gondii DNA was successfully detected. Specificity investigation of the mMBP indicated that relative low recovery of fluorescence intensity was obtained when the target DNA with one-base pair mismatch was added, this result indicated the high specificity of the sensing probe. Our research simultaneously indicated that mMBP can be conveniently separated from the unhybridized stem-loop DNA and target DNA, which will be meaningful in DNA sensing and purification process.

  4. The fast reciprocating magnetic probe system on the J-TEXT tokamak

    NASA Astrophysics Data System (ADS)

    Li, Fuming; Chen, Zhipeng; Zhuang, Ge; Liu, Hai; Zhu, Lizhi

    2016-11-01

    The fast reciprocating magnetic probe (FRMP) system is newly developed on the Joint Texas Experimental Tokamak (J-TEXT) to measure the local magnetic fluctuations at the plasma edge. The magnetic probe array in the FRMP consists of four 2-dimensional magnetic probes arranged at different radial locations to detect local poloidal and radial magnetic fields. These probes are protected by a graphite and boron nitride casing to improve the frequency response of each probe; they are mounted on the head of a movable rod, which is oriented along radial direction at the top of the torus. In the experiments, multiple core diagnostics show that the insertion of the FRMP has little impact on the equilibrium of the plasma. Local magnetic fluctuations inside the last closed flux surface are successfully measured by the FRMP.

  5. The fast reciprocating magnetic probe system on the J-TEXT tokamak.

    PubMed

    Li, Fuming; Chen, Zhipeng; Zhuang, Ge; Liu, Hai; Zhu, Lizhi

    2016-11-01

    The fast reciprocating magnetic probe (FRMP) system is newly developed on the Joint Texas Experimental Tokamak (J-TEXT) to measure the local magnetic fluctuations at the plasma edge. The magnetic probe array in the FRMP consists of four 2-dimensional magnetic probes arranged at different radial locations to detect local poloidal and radial magnetic fields. These probes are protected by a graphite and boron nitride casing to improve the frequency response of each probe; they are mounted on the head of a movable rod, which is oriented along radial direction at the top of the torus. In the experiments, multiple core diagnostics show that the insertion of the FRMP has little impact on the equilibrium of the plasma. Local magnetic fluctuations inside the last closed flux surface are successfully measured by the FRMP.

  6. The fast reciprocating magnetic probe system on the J-TEXT tokamak

    SciTech Connect

    Li, Fuming; Chen, Zhipeng Zhuang, Ge; Liu, Hai; Zhu, Lizhi

    2016-11-15

    The fast reciprocating magnetic probe (FRMP) system is newly developed on the Joint Texas Experimental Tokamak (J-TEXT) to measure the local magnetic fluctuations at the plasma edge. The magnetic probe array in the FRMP consists of four 2-dimensional magnetic probes arranged at different radial locations to detect local poloidal and radial magnetic fields. These probes are protected by a graphite and boron nitride casing to improve the frequency response of each probe; they are mounted on the head of a movable rod, which is oriented along radial direction at the top of the torus. In the experiments, multiple core diagnostics show that the insertion of the FRMP has little impact on the equilibrium of the plasma. Local magnetic fluctuations inside the last closed flux surface are successfully measured by the FRMP.

  7. Probing magnetic and gold nanoparticles by using MAClevers® as ultrasensitive sensors.

    PubMed

    Nakamura, Marcelo; Araki, Koiti; Toma, Henrique E

    2010-12-01

    Magnetic AFM probes known as MAClevers® were employed for sensing picogram amounts of magnetic nanoparticles, based on the cantilever frequency shifts resulting from the magnetically induced adsorption of mass. By using organothiol functionalized magnetic nanoparticles, this analytical strategy was successfully extended to the detection of gold nanoparticles, as confirmed by confocal Raman microscopy.

  8. Development of a novel shape memory alloy-actuated resettable locking device for magnetic bearing reaction wheel.

    PubMed

    Zhang, Xiaoyong; Yan, Xiaojun; Zhang, Shaowei; Nie, Jingxu

    2014-01-01

    The current investigation proposes a shape memory alloy (SMA)-actuated resettable locking device for magnetic bearing reaction wheel. The device employed two SMA wire-based actuators to realize locking and unlocking. Dual-slope mating surfaces were used on one hand to transmit the motion between a moving part and a clamp, and on the other hand to achieve a self-locking linkage in the locking state. Moreover, geometric parameters of the two SMA wires and corresponding bias springs were also designed. Based on the proposed design scheme, four locking devices were manufactured and assembled. Performance and environmental tests were performed to verify the proposed locking device. Test results show that the locking device can protect the magnetic bearing reaction wheel from launch vibration damage, and can withstand the thermal environment in the launch and on-orbit stage. Moreover, the device can be successfully operated for 76 times, and the response time for the locking and unlocking processes under 7 V power supply is 0.9 s and 5.6 s, respectively. Considering the results obtained from these tests, we conclude that the proposed resettable locking device is an attractive alternative technology to conventional motor-driven or pyrotechnics-based technologies, and can be applied reliably in the magnetic bearing reaction wheel.

  9. Development of a novel shape memory alloy-actuated resettable locking device for magnetic bearing reaction wheel

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoyong; Yan, Xiaojun; Zhang, Shaowei; Nie, Jingxu

    2014-01-01

    The current investigation proposes a shape memory alloy (SMA)-actuated resettable locking device for magnetic bearing reaction wheel. The device employed two SMA wire-based actuators to realize locking and unlocking. Dual-slope mating surfaces were used on one hand to transmit the motion between a moving part and a clamp, and on the other hand to achieve a self-locking linkage in the locking state. Moreover, geometric parameters of the two SMA wires and corresponding bias springs were also designed. Based on the proposed design scheme, four locking devices were manufactured and assembled. Performance and environmental tests were performed to verify the proposed locking device. Test results show that the locking device can protect the magnetic bearing reaction wheel from launch vibration damage, and can withstand the thermal environment in the launch and on-orbit stage. Moreover, the device can be successfully operated for 76 times, and the response time for the locking and unlocking processes under 7 V power supply is 0.9 s and 5.6 s, respectively. Considering the results obtained from these tests, we conclude that the proposed resettable locking device is an attractive alternative technology to conventional motor-driven or pyrotechnics-based technologies, and can be applied reliably in the magnetic bearing reaction wheel.

  10. ANOMALOUS COSMIC RAYS AS PROBES OF MAGNETIC CLOUDS

    SciTech Connect

    Reames, D. V.; Kahler, S. W.; Tylka, A. J.

    2009-08-01

    We report, for the first time, the observation near the Earth of anomalous cosmic ray (ACR) particles throughout the interiors of interplanetary magnetic clouds (MCs) at the same intensity as outside the MCs. ACRs, accelerated in the outer heliosphere, have unique elemental abundances making their identity unambiguous as they probe these clouds from the outside. Thus, MCs, carried out from the Sun by coronal mass ejections (CMEs), are seen to contain no structures that are magnetically closed to the penetration of ions with energies above a few MeV amu{sup -1}. As the MCs expand outward, they must fill their increasing volume with ACRs dynamically, to the same degree as neighboring 'open' field lines. These observations cast doubt on conventional ideas about the closed field topologies of MCs and the cross-field transport of energetic particles. The ACR observations conflict with some reports of significant exclusion from MCs of solar energetic particles (SEPs) of comparable energy and rigidity. A process that allows cross-field transport of ACRs may also allow similar transport of SEPs late in events, causing the large spatial extent and uniformity of SEPs in 'invariant spectral regions' extending far behind CME-driven shock waves.

  11. Analysis of Scanned Probe Images for Magnetic Focusing in Graphene

    NASA Astrophysics Data System (ADS)

    Bhandari, Sagar; Lee, Gil-Ho; Kim, Philip; Westervelt, Robert M.

    2017-07-01

    We have used cooled scanning probe microscopy (SPM) to study electron motion in nanoscale devices. The charged tip of the microscope was raster-scanned at constant height above the surface as the conductance of the device was measured. The image charge scatters electrons away, changing the path of electrons through the sample. Using this technique, we imaged cyclotron orbits that flow between two narrow contacts in the magnetic focusing regime for ballistic hBN-graphene-hBN devices. We present herein an analysis of our magnetic focusing imaging results based on the effects of the tip-created charge density dip on the motion of ballistic electrons. The density dip locally reduces the Fermi energy, creating a force that pushes electrons away from the tip. When the tip is above the cyclotron orbit, electrons are deflected away from the receiving contact, creating an image by reducing the transmission between contacts. The data and our analysis suggest that the graphene edge is rather rough, and electrons scattering off the edge bounce in random directions. However, when the tip is close to the edge, it can enhance transmission by bouncing electrons away from the edge, toward the receiving contact. Our results demonstrate that cooled SPM is a promising tool to investigate the motion of electrons in ballistic graphene devices.

  12. Analysis of Scanned Probe Images for Magnetic Focusing in Graphene

    NASA Astrophysics Data System (ADS)

    Bhandari, Sagar; Lee, Gil-Ho; Kim, Philip; Westervelt, Robert M.

    2017-02-01

    We have used cooled scanning probe microscopy (SPM) to study electron motion in nanoscale devices. The charged tip of the microscope was raster-scanned at constant height above the surface as the conductance of the device was measured. The image charge scatters electrons away, changing the path of electrons through the sample. Using this technique, we imaged cyclotron orbits that flow between two narrow contacts in the magnetic focusing regime for ballistic hBN-graphene-hBN devices. We present herein an analysis of our magnetic focusing imaging results based on the effects of the tip-created charge density dip on the motion of ballistic electrons. The density dip locally reduces the Fermi energy, creating a force that pushes electrons away from the tip. When the tip is above the cyclotron orbit, electrons are deflected away from the receiving contact, creating an image by reducing the transmission between contacts. The data and our analysis suggest that the graphene edge is rather rough, and electrons scattering off the edge bounce in random directions. However, when the tip is close to the edge, it can enhance transmission by bouncing electrons away from the edge, toward the receiving contact. Our results demonstrate that cooled SPM is a promising tool to investigate the motion of electrons in ballistic graphene devices.

  13. Standard Practices for Usage of Inductive Magnetic Field Probes with Application to Electric Propulsion Testing

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Hill, Carrie S.; Turchi, Peter J.; Burton, Rodney L.; Messer, Sarah; Lovberg, Ralph H.; Hallock, Ashley K.

    2013-01-01

    Inductive magnetic field probes (also known as B-dot probes and sometimes as B-probes or magnetic probes) are often employed to perform field measurements in electric propulsion applications where there are time-varying fields. Magnetic field probes provide the means to measure these magnetic fields and can even be used to measure the plasma current density indirectly through the application of Ampere's law. Measurements of this type can yield either global information related to a thruster and its performance or detailed, local data related to the specific physical processes occurring in the plasma. Results of the development of a standard for B-dot probe measurements are presented, condensing the available literature on the subject into an accessible set of rules, guidelines, and techniques to standardize the performance and presentation of future measurements.

  14. Standard Practices for Usage of Inductive Magnetic Field Probes with Application to Electric Propulsion Testing

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Hill, Carrie S.; Turchi, Peter J.; Burton, Rodney L.; Messer, Sarah; Lovberg, Ralph H.; Hallock, Ashley K.

    2013-01-01

    Inductive magnetic field probes (also known as B-dot probes and sometimes as B-probes or magnetic probes) are often employed to perform field measurements in electric propulsion applications where there are time-varying fields. Magnetic field probes provide the means to measure these magnetic fields and can even be used to measure the plasma current density indirectly through the application of Ampere's law. Measurements of this type can yield either global information related to a thruster and its performance or detailed, local data related to the specific physical processes occurring in the plasma. Results of the development of a standard for B-dot probe measurements are presented, condensing the available literature on the subject into an accessible set of rules, guidelines, and techniques to standardize the performance and presentation of future measurements.

  15. Pulsed field probe of real time magnetization dynamics in magnetic nanoparticle systems

    NASA Astrophysics Data System (ADS)

    Foulkes, T.; Syed, M.; Taplin, T.

    2015-05-01

    Magnetic nanoparticles (MNPs) are extensively used in biotechnology. These applications rely on magnetic properties that are a keen function of MNP size, distribution, and shape. Various magneto-optical techniques, including Faraday Rotation (FR), Cotton-Mouton Effect, etc., have been employed to characterize magnetic properties of MNPs. Generally, these measurements employ AC or DC fields. In this work, we describe the results from a FR setup that uses pulsed magnetic fields and an analysis technique that makes use of the entire pulse shape to investigate size distribution and shape anisotropy. The setup employs a light source, polarizing components, and a detector that are used to measure the rotation of light from a sample that is subjected to a pulsed magnetic field. This magnetic field "snapshot" is recorded alongside the intensity pulse of the sample's response. This side by side comparison yields useful information about the real time magnetization dynamics of the system being probed. The setup is highly flexible with variable control of pulse length and peak magnitude. Examining the raw data for the response of bare Fe3O4 and hybrid Au and Fe3O4 nanorods reveals interesting information about Brownian relaxation and the hydrodynamic size of these nanorods. This analysis exploits the self-referencing nature of this measurement to highlight the impact of an applied field on creating a field induced transparency for a longitudinal measurement. Possible sources for this behavior include shape anisotropy and field assisted aggregate formation.

  16. Single core-shell nanoparticle probes for non-invasive magnetic force microscopy.

    PubMed

    Uhlig, Tino; Wiedwald, Ulf; Seidenstücker, Axel; Ziemann, Paul; Eng, Lukas M

    2014-06-27

    We present an easy, fast and reliable method for the preparation of magnetic force microscopy (MFM) probes based on single Co nanoparticles (NPs). Due to their dipolar character, these magnetic probes open up a new approach for quantitative and non-invasive MFM measurements on the nanometer length scale. To guarantee long-term stability of these tips under ambient conditions, an ultrathin protecting Au shell was grown around the Co NPs through photochemical deposition. Single magnetic particles were firmly attached to standard silicon AFM tips using bifunctional self-assembling molecules. Such probes were tested on longitudinal magnetic recording media and compared to the results as recorded with conventional thin-film MFM tips. Easy data interpretation of the magnetic nanoparticle probes in a point dipole model is shown. Our nanoparticle tips provide excellent endurance for MFM recording, enable non-invasive probing while maintaining a high sensitivity, resolution, and reproducibility.

  17. Probing Intergalactic Magnetic Fields from gamma-Ray Observations

    NASA Astrophysics Data System (ADS)

    Chen, Wenlei

    The large-scaled magnetic fields in intergalactic space may contain detailed information of the primordial magnetic fields produced in the early Universe. The generation of the cosmological matter-antimatter asymmetry may produce helical magnetic fields via CP (charge conjugation and parity) violating interactions during matter-genesis. Thus, the study of the intergalactic magnetic field (IGMF) could provide a new window on early-Universe cosmology. IGMFs deflect the electron-positron pairs produced by TeV gamma-rays from blazars, resulting in broadened beams of cascade GeV gamma-rays known as pair halos. In the presence of helical IGMFs, cascade GeV gamma-rays at different energies from a distant source fall into patterns in the observation plane in the GeV gamma-ray sky that have a similar chirality. These signatures of the IGMF on the gamma-ray emission from extragalactic sources, i.e. pair halos and helical patterns, can be observed using data from the Fermi Large Area Telescope (Fermi-LAT). In this dissertation, I describe methods for probing the IGMF using gamma-ray observations. I report on the results of a search for gamma-ray pair halos with a stacking analysis of low-redshift blazars using data from Fermi-LAT. For this analysis we used a number of a priori selection criteria, including the spatial and spectral properties of the Fermi sources. The angular distribution of ˜ 1 GeV photons around 24 stacked isolated high-synchrotron-peaked BL Lacs with redshift z < 0.5 shows an excess over that of point-like sources. A frequentist test yields a p-value of p ˜ 0.01 for the extended emission against the point-source hypothesis. A Bayesian estimation provides the common logarithm of Bayes factors > 2, consistent with expectations for pair halos produced in the IGMF with strength of ˜ 10-17 to 10-15 Gauss. In addition, I present a search for parity violating signatures of helical IGMFs in the GeV gamma-ray sky. In this study, the IGMF helicity is examined by

  18. Probing the Earth's core with magnetic field observations from Swarm

    NASA Astrophysics Data System (ADS)

    Finlay, Christopher; Olsen, Nils; Kotsiaros, Stavros; Gillet, Nicolas; Tøffner-Clausen, Lars

    2016-07-01

    By far the largest part of the Earth's magnetic field is generated by motions taking place within our planet's liquid metal outer core. Variations of this core-generated field thus provide a unique means of probing the dynamics taking place in the deepest reaches of the Earth. In this contribution we present a new high resolution model of the core-generated magnetic field, and its recent time changes, derived from a dataset that includes more two years of observations from the Swarm mission. Resulting inferences regarding the underlying core flow, its dynamics, and the nature of the geodynamo process will be discussed. The CHAOS-6 geomagnetic field model, covering the interval 1999-2016, is derived from magnetic data collected by the three Swarm missions, as well as the earlier CHAMP and Oersted satellites, and monthly means data collected from 160 ground observatories. Advantage is taken of the constellation aspect of the Swarm mission by ingesting both scalar and vector field differences along-track and across track between the lower pair of Swarm satellites. The internal part of the model consists of a spherical harmonic (SH) expansion, time-dependent for degrees 20 and below. The model coefficients are estimated using a regularized, iteratively reweighted, least squares scheme involving Huber weights. At Earth's surface, CHAOS-6 shows evidence for positive acceleration of the field intensity in 2015 over a broad area around longitude 90deg E that is also seen at ground observatories such as Novosibirsk. At the core surface, we are able to map the secular variation (linear trend in the magnetic field) up to SH degree 16. The radial field acceleration at the core surface in 2015 is found be largest at low latitudes under the India-South East Asia region and under the region of northern South America, as well as at high northern latitudes under Alaska and Siberia. Surprisingly, there is also evidence for some acceleration in the central Pacific region, for example

  19. Cleaning of contaminated MFM probes using a BOPP film and external magnetic field.

    PubMed

    Zhang, Chao; Liu, Jinyun; Meng, Qingling; Zhang, Wenxiao; Wang, Ying; Li, Dayou; Wang, Zuobin

    2017-02-24

    When magnetic samples are tested with a magnetic force microscope (MFM), the probe tip can inevitably be contaminated and magnetic particles are often adhered to the tip surface. The probe with magnetic contamination will seriously affect the quality of morphological and magnetic imaging. In the work, a method for the cleaning of contaminated magnetic probe tips was developed by the use of a biaxially-oriented polypropylene (BOPP) film together with an external magnet field in an MFM system. In the experiments, an MFM system was used for manipulating the tip to push into the BOPP film with a depth of 50-100nm under a magnetic field and hold for 5s, and the relationships between loading forces and separating forces were studied. The scanning electron microscope (SEM) images have shown that the use of the BOPP film together with an external magnet field is effective for the cleaning of contaminated MFM probes. This method can greatly improve the quality of magnetic imaging, prolong the service life of magnetic probes and reduce the experimental costs in many MFM applications.

  20. Magnetic and Langmuir Probe Measurements on the Plasmoid Thruster Experiment (PTX)

    NASA Technical Reports Server (NTRS)

    Koelfgen, Syri J.; Eskridge, Richard; Lee, Michael H.; Martin, Adam; Hawk, Clark W.; Fimognan, Peter

    2004-01-01

    The Plasmoid Thruster Experiment (PTX) operates by inductively producing plasmoids in a conical theta-pinch coil and ejecting them at high velocity. A plasmoid is a plasma with an imbedded closed magnetic field structure. The shape and magnetic field structure of the translating plasmoids have been measured with of an array of magnetic field probes. Six sets of two B-dot probes were constructed for measuring B(sub z) and B(sub theta), the axial and azimuthal components of the magnetic field. The probes are wound on a square G10 form, and have an average (calibrated) NA of 9.37 x l0(exp -5) square meters, where N is the number of turns and A is the cross-sectional area. The probes were calibrated with a Helmholtz coil, driven by a high-voltage pulser to measure NA, and by a signal generator to determine the probe's frequency response. The plasmoid electron number density n(sub e) electron temperature T(sub e), and velocity ratio v/c(sub m), (where v is the bulk plasma flow velocity and c(sub m), is the ion thermal speed) have also been measured with a quadruple Langmuir probe. The Langmuir probe tips are 10 mm long, 20-mil diameter stainless steel wire, housed in a 6-inch long 4-bore aluminum rod. Measurements on PTX with argon and hydrogen from the magnetic field probes and quadruple Langmuir probe will be presented in this paper.

  1. Probing magnetic turbulence by synchrotron polarimetry: statistics and structure of magnetic fields from Stokes correlators

    NASA Astrophysics Data System (ADS)

    Waelkens, A. H.; Schekochihin, A. A.; Enßlin, T. A.

    2009-10-01

    We describe a novel technique for probing the statistical properties of cosmic magnetic fields based on radio polarimetry data. Second-order magnetic field statistics like the power spectrum cannot always distinguish between magnetic fields with essentially different spatial structure. Synchrotron polarimetry naturally allows certain fourth-order magnetic field statistics to be inferred from observational data, which lifts this degeneracy and can thereby help us gain a better picture of the structure of the cosmic fields and test theoretical scenarios describing magnetic turbulence. In this work we show that a fourth-order correlator of specific physical interest, the tension force spectrum, can be recovered from the polarized synchrotron emission data. We develop an estimator for this quantity based on polarized emission observations in the Faraday rotation free frequency regime. We consider two cases: a statistically isotropic field distribution, and a statistically isotropic field superimposed on a weak mean field. In both cases the tension force power spectrum is measurable; in the latter case, the magnetic power spectrum may also be obtainable. The method is exact in the idealized case of a homogeneous relativistic electron distribution that has a power-law energy spectrum with a spectral index of p = 3, and assumes statistical isotropy of the turbulent field. We carry out numerical tests of our method using synthetic polarized emission data generated from numerically simulated magnetic fields. We show that the method is valid, that it is not prohibitively sensitive to the value of the electron spectral index p, and that the observed tension force spectrum allows one to distinguish between e.g. a randomly tangled magnetic field (a default assumption in many studies) and a field organized in folded flux sheets or filaments.

  2. High sensitivity piezomagnetic force microscopy for quantitative probing of magnetic materials at the nanoscale.

    PubMed

    Chen, Qian Nataly; Ma, Feiyue; Xie, Shuhong; Liu, Yuanming; Proksch, Roger; Li, Jiangyu

    2013-07-07

    Accurate scanning probing of magnetic materials at the nanoscale is essential for developing and characterizing magnetic nanostructures, yet quantitative analysis is difficult using the state of the art magnetic force microscopy, and has limited spatial resolution and sensitivity. In this communication, we develop a novel piezomagnetic force microscopy (PmFM) technique, with the imaging principle based on the detection of magnetostrictive response excited by an external magnetic field. In combination with the dual AC resonance tracking (DART) technique, the contact stiffness and energy dissipation of the samples can be simultaneously mapped along with the PmFM phase and amplitude, enabling quantitative probing of magnetic materials and structures at the nanoscale with high sensitivity and spatial resolution. PmFM has been applied to probe magnetic soft discs and cobalt ferrite thin films, demonstrating it as a powerful tool for a wide range of magnetic materials.

  3. Electrothermal linear actuator

    NASA Technical Reports Server (NTRS)

    Derr, L. J.; Tobias, R. A.

    1969-01-01

    Converting electric power into powerful linear thrust without generation of magnetic fields is accomplished with an electrothermal linear actuator. When treated by an energized filament, a stack of bimetallic washers expands and drives the end of the shaft upward.

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

    PubMed

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

    2012-10-01

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

  5. Crosslinking metal nanoparticles into the polymer backbone of hydrogels enables preparation of soft, magnetic field-driven actuators with muscle-like flexibility.

    PubMed

    Fuhrer, Roland; Athanassiou, Evagelos Kimon; Luechinger, Norman Albert; Stark, Wendelin Jan

    2009-03-01

    The combination of force and flexibility is at the core of biomechanics and enables virtually all body movements in living organisms. In sharp contrast, presently used machines are based on rigid, linear (cylinders) or circular (rotator in an electrical engine) geometries. As a potential bioinspired alternative, magnetic elastomers can be realized through dispersion of micro- or nanoparticles in polymer matrices and have attracted significant interest as soft actuators in artificial organs, implants, and devices for controlled drug delivery. At present, magnetic particle loss and limited actuator strength have restricted the use of such materials to niche applications. We describe the direct incorporation of metal nanoparticles into the backbone of a hydrogel and application as an ultra-flexible, yet strong magnetic actuator. Covalent bonding of the particles prevents metal loss or leaching. Since metals have a far higher saturation magnetization and higher density than oxides, the resulting increased force/volume ratio afforded significantly stronger magnetic actuators with high mechanical stability, elasticity, and shape memory effect.

  6. Structural Analysis of a Magnetically Actuated Silicon Nitride Micro-Shutter for Space Applications

    NASA Technical Reports Server (NTRS)

    Loughlin, James P.; Fettig, Rainer K.; Moseley, S. Harvey; Kutyrev, Alexander S.; Mott, D. Brent; Obenschain, Arthur F. (Technical Monitor)

    2002-01-01

    Finite element models have been created to simulate the electrostatic and electromagnetic actuation of a 0.5 micrometers silicon nitride micro-shutter for use in a spacebased Multi-object Spectrometer (MOS). The microshutter uses a torsion hinge to go from the closed, 0 degree, position, to the open, 90 degree position. Stresses in the torsion hinge are determined with a large deformation nonlinear finite element model. The simulation results are compared to experimental measurements of fabricated micro-shutter devices.

  7. Distinguishing magnetic and electrostatic interactions by a Kelvin probe force microscopy–magnetic force microscopy combination

    PubMed Central

    Jaafar, Miriam; Iglesias-Freire, Oscar; Serrano-Ramón, Luis; Ibarra, Manuel Ricardo; de Teresa, Jose Maria

    2011-01-01

    Summary The most outstanding feature of scanning force microscopy (SFM) is its capability to detect various different short and long range interactions. In particular, magnetic force microscopy (MFM) is used to characterize the domain configuration in ferromagnetic materials such as thin films grown by physical techniques or ferromagnetic nanostructures. It is a usual procedure to separate the topography and the magnetic signal by scanning at a lift distance of 25–50 nm such that the long range tip–sample interactions dominate. Nowadays, MFM is becoming a valuable technique to detect weak magnetic fields arising from low dimensional complex systems such as organic nanomagnets, superparamagnetic nanoparticles, carbon-based materials, etc. In all these cases, the magnetic nanocomponents and the substrate supporting them present quite different electronic behavior, i.e., they exhibit large surface potential differences causing heterogeneous electrostatic interaction between the tip and the sample that could be interpreted as a magnetic interaction. To distinguish clearly the origin of the tip–sample forces we propose to use a combination of Kelvin probe force microscopy (KPFM) and MFM. The KPFM technique allows us to compensate in real time the electrostatic forces between the tip and the sample by minimizing the electrostatic contribution to the frequency shift signal. This is a great challenge in samples with low magnetic moment. In this work we studied an array of Co nanostructures that exhibit high electrostatic interaction with the MFM tip. Thanks to the use of the KPFM/MFM system we were able to separate the electric and magnetic interactions between the tip and the sample. PMID:22003461

  8. Distinguishing magnetic and electrostatic interactions by a Kelvin probe force microscopy-magnetic force microscopy combination.

    PubMed

    Jaafar, Miriam; Iglesias-Freire, Oscar; Serrano-Ramón, Luis; Ibarra, Manuel Ricardo; de Teresa, Jose Maria; Asenjo, Agustina

    2011-01-01

    The most outstanding feature of scanning force microscopy (SFM) is its capability to detect various different short and long range interactions. In particular, magnetic force microscopy (MFM) is used to characterize the domain configuration in ferromagnetic materials such as thin films grown by physical techniques or ferromagnetic nanostructures. It is a usual procedure to separate the topography and the magnetic signal by scanning at a lift distance of 25-50 nm such that the long range tip-sample interactions dominate. Nowadays, MFM is becoming a valuable technique to detect weak magnetic fields arising from low dimensional complex systems such as organic nanomagnets, superparamagnetic nanoparticles, carbon-based materials, etc. In all these cases, the magnetic nanocomponents and the substrate supporting them present quite different electronic behavior, i.e., they exhibit large surface potential differences causing heterogeneous electrostatic interaction between the tip and the sample that could be interpreted as a magnetic interaction. To distinguish clearly the origin of the tip-sample forces we propose to use a combination of Kelvin probe force microscopy (KPFM) and MFM. The KPFM technique allows us to compensate in real time the electrostatic forces between the tip and the sample by minimizing the electrostatic contribution to the frequency shift signal. This is a great challenge in samples with low magnetic moment. In this work we studied an array of Co nanostructures that exhibit high electrostatic interaction with the MFM tip. Thanks to the use of the KPFM/MFM system we were able to separate the electric and magnetic interactions between the tip and the sample.

  9. Utility of a baffle probe for measurements in a magnetized plasma^*

    NASA Astrophysics Data System (ADS)

    Demidov, Vladimir; Finnegan, Sean; Koepke, Mark; Reynolds, Eric

    2003-10-01

    A probe for measurements of space potential and its oscillations in magnetized plasmas is tested. The probe consists of a tungsten wire tip, situated perpendicular to the magnetic field, and is partially shielded by ceramic baffles. The probe works under the condition that electron Larmor radius is much smaller than the probe radius, and the ion Larmor radius is comparable to or larger than the probe radius. By rotating the baffle configuration around the probe tip, the ratio between electron and ion probe current can be adjusted. The probe uses the same principle as Katsumata probe, but has the advantage of convenient controllability of the ratio between electron and ion current. Experiments have been conducted in a fully ionized, barium plasma in the WVUniversity Q-machine. By rotating of the probe it is possible to make electron and ion contributions to the floating probe's collected current comparable within a fraction of T_e/e of the dc space potential. Measurements of ac probe potentials allow us to distinguish income of oscillations from space potentials and electron temperature fluctuations. ^*This research supported by NSF

  10. Defect-induced magnetism in SiC probed by nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Zhang, Z. T.; Dmytriieva, D.; Molatta, S.; Wosnitza, J.; Wang, Yutian; Helm, M.; Zhou, Shengqiang; Kühne, H.

    2017-02-01

    We give evidence for intrinsic defect-induced bulk paramagnetism in SiC by means of 13C and 29Si nuclear magnetic resonance (NMR) spectroscopy. The temperature dependence of the internal dipole-field distribution, probed by the spin part of the NMR Knight shift and the spectral linewidth, follows the Curie law and scales very well with the macroscopic dc susceptibility. In order to quantitatively analyze the NMR spectra, a microscopic model based on dipole-dipole interactions was developed. The very good agreement between these simulations and the NMR data establishes a direct relation between the frequency distribution of the spectral intensity and the corresponding real-space volumes of nuclear spins. The presented approach by NMR can be applied to a variety of similar materials and, thus, opens a new avenue for the microscopic exploration and exploitation of diluted bulk magnetism in semiconductors.

  11. Shimming of a Magnet for Calibration of NMR Probes for the Muon g-2 Experiment

    NASA Astrophysics Data System (ADS)

    Bielajew, Rachel

    2013-10-01

    The Muon g-2 Experiment at Fermilab aims to measure the anomalous magnetic moment aμ ≡ (g-2)/2 of the muon to the precision of 0.14 parts per million. This experimental value of aμ can then be compared to the similarly precise theoretical predictions of the Standard Model in order to test the completeness of the model. The value of aμ is extracted from muons precessing in a magnetic field. The magnetic field will be measured with a set of 400 Nuclear Magnetic Resonance (NMR) probes, which have the ability to measure the field to a precision of tens of parts per billion. Before the Muon g-2 Experiment can take place, new NMR probes must be designed, built, and tested using a 1.45 Tesla test magnet at the University of Washington Center for Experimental Nuclear Physics and Astrophysics (CENPA). In order to achieve a significant signal from NMR probes, the magnetic field in which the probes are immersed must be extremely uniform. The existing magnet at CENPA has an approximately linear gradient in magnetic field of about 1 Gauss per centimeter in the smoothest direction. A pair of adjacent square Helmholtz coils was designed and built to create a linear gradient in order to cancel the existing gradient. The length of the NMR signals improved with the implementation of the coils. The results of the addition of the coils to the magnet on the signals from the NMR probes will be presented.

  12. A magnetically actuated cellular strain assessment tool for quantitative analysis of strain induced cellular reorientation and actin alignment

    NASA Astrophysics Data System (ADS)

    Khademolhosseini, F.; Liu, C.-C.; Lim, C. J.; Chiao, M.

    2016-08-01

    Commercially available cell strain tools, such as pneumatically actuated elastomer substrates, require special culture plates, pumps, and incubator setups. In this work, we present a magnetically actuated cellular strain assessment tool (MACSAT) that can be implemented using off-the-shelf components and conventional incubators. We determine the strain field on the MACSAT elastomer substrate using numerical models and experimental measurements and show that a specific region of the elastomer substrate undergoes a quasi-uniaxial 2D stretch, and that cells confined to this region of the MACSAT elastomer substrate undergo tensile, compressive, or zero axial strain depending on their angle of orientation. Using the MACSAT to apply cyclic strain on endothelial cells, we demonstrate that actin filaments within the cells reorient away from the stretching direction, towards the directions of minimum axial strain. We show that the final actin orientation angles in strained cells are spread over a region of compressive axial strain, confirming previous findings on the existence of a varied pre-tension in the actin filaments of the cytoskeleton. We also demonstrate that strained cells exhibit distinctly different values of actin alignment coherency compared to unstrained cells and therefore propose that this parameter, i.e., the coherency of actin alignment, can be used as a new readout to determine the occurrence/extent of actin alignment in cell strain experiments. The tools and methods demonstrated in this study are simple and accessible and can be easily replicated by other researchers to study the strain response of other adherent cells.

  13. Novel Handheld Magnetometer Probe Based on Magnetic Tunnelling Junction Sensors for Intraoperative Sentinel Lymph Node Identification

    PubMed Central

    Cousins, A.; Balalis, G. L.; Thompson, S. K.; Forero Morales, D.; Mohtar, A.; Wedding, A. B.; Thierry, B.

    2015-01-01

    Using magnetic tunnelling junction sensors, a novel magnetometer probe for the identification of the sentinel lymph node using magnetic tracers was developed. Probe performance was characterised in vitro and validated in a preclinical swine model. Compared to conventional gamma probes, the magnetometer probe showed excellent spatial resolution of 4.0 mm, and the potential to detect as few as 5 μg of magnetic tracer. Due to the high sensitivity of the magnetometer, all first-tier nodes were identified in the preclinical experiments, and there were no instances of false positive or false negative detection. Furthermore, these preliminary data encourage the application of the magnetometer probe for use in more complex lymphatic environments, such as in gastrointestinal cancers, where the sentinel node is often in close proximity to other non-sentinel nodes, and high spatial resolution detection is required. PMID:26038833

  14. Novel handheld magnetometer probe based on magnetic tunnelling junction sensors for intraoperative sentinel lymph node identification.

    PubMed

    Cousins, A; Balalis, G L; Thompson, S K; Forero Morales, D; Mohtar, A; Wedding, A B; Thierry, B

    2015-06-03

    Using magnetic tunnelling junction sensors, a novel magnetometer probe for the identification of the sentinel lymph node using magnetic tracers was developed. Probe performance was characterised in vitro and validated in a preclinical swine model. Compared to conventional gamma probes, the magnetometer probe showed excellent spatial resolution of 4.0 mm, and the potential to detect as few as 5 μg of magnetic tracer. Due to the high sensitivity of the magnetometer, all first-tier nodes were identified in the preclinical experiments, and there were no instances of false positive or false negative detection. Furthermore, these preliminary data encourage the application of the magnetometer probe for use in more complex lymphatic environments, such as in gastrointestinal cancers, where the sentinel node is often in close proximity to other non-sentinel nodes, and high spatial resolution detection is required.

  15. Study on Metal Detection with an Electromagnetic Induction Probe Utilizing a Rotating Magnetic Field

    NASA Astrophysics Data System (ADS)

    Koyama, Kiyoshi; Hoshikawa, Hiroshi; Sakon, Toshikazu

    The present paper describes an investigation conducted on metal detection with a scanning probe. The authors applied a rotating magnetic field probe to metal detection. The rotating magnetic field probe is composed of two vertically placed rectangular exciting coils and a circular detecting coil. The experimental results confirmed that the probe can detect metal objects and provide more information about their shape, direction, and electromagnetic characteristics than conventional metal detector probes. A two-dimensional signal display shows a blurred image of the metal object and the signal phase indicates the object's direction and electromagnetic characteristics. The experimental results showed that excellent restoration of the surface shapes of metal objects can be obtained for both magnetic and nonmagnetic metals under present conditions. There is also a possibility that the rough shape of a metal object can be estimated from the restored image.

  16. On-tip sub-micrometer Hall probes for magnetic microscopy prepared by AFM lithography.

    PubMed

    Gregusová, D; Martaus, J; Fedor, J; Kúdela, R; Kostic, I; Cambel, V

    2009-07-01

    We developed a technology of sub-micrometer Hall probes for future application in scanning hall probe microscopy (SHPM) and magnetic force microscopy (MFM). First, the Hall probes of approximately 9-mum dimensions are prepared on the top of high-aspect-ratio GaAs pyramids with an InGaP/AlGaAs/GaAs active layer using wet-chemical etching and non-planar lithography. Then we show that the active area of planar Hall probes can be downsized to sub-micrometer dimensions by local anodic oxidation technique using an atomic force microscope. Such planar probes are tested and their noise and magnetic field sensitivity are evaluated. Finally, the two technologies are combined to fabricate sub-micrometer Hall probes on the top of high-aspect ratio mesa for future SHPM and MFM techniques.

  17. Miniaturized magnetic-driven scanning probe for endoscopic optical coherence tomography.

    PubMed

    Pang, Ziwei; Wu, Jigang

    2015-06-01

    We designed and implemented a magnetic-driven scanning (MDS) probe for endoscopic optical coherence tomography (OCT). The probe uses an externally-driven tiny magnet in the distal end to achieve unobstructed 360-degree circumferential scanning at the side of the probe. The design simplifies the scanning part inside the probe and thus allows for easy miniaturization and cost reduction. We made a prototype probe with an outer diameter of 1.4 mm and demonstrated its capability by acquiring OCT images of ex vivo trachea and artery samples from a pigeon. We used a spectrometer-based Fourier-domain OCT system and the system sensitivity with our prototype probe was measured to be 91 dB with an illumination power of 850 μW and A-scan exposure time of 1 ms. The axial and lateral resolutions of the system are 6.5 μm and 8.1 μm, respectively.

  18. Note: A calibration method to determine the lumped-circuit parameters of a magnetic probe.

    PubMed

    Li, Fuming; Chen, Zhipeng; Zhu, Lizhi; Liu, Hai; Wang, Zhijiang; Zhuang, Ge

    2016-06-01

    This paper describes a novel method to determine the lumped-circuit parameters of a magnetic inductive probe for calibration by using Helmholtz coils with high frequency power supply (frequency range: 10 kHz-400 kHz). The whole calibration circuit system can be separated into two parts: "generator" circuit and "receiver" circuit. By implementing the Fourier transform, two analytical lumped-circuit models, with respect to these separated circuits, are constructed to obtain the transfer function between each other. Herein, the precise lumped-circuit parameters (including the resistance, inductance, and capacitance) of the magnetic probe can be determined by fitting the experimental data to the transfer function. Regarding the fitting results, the finite impedance of magnetic probe can be used to analyze the transmission of a high-frequency signal between magnetic probes, cables, and acquisition system.

  19. Note: A calibration method to determine the lumped-circuit parameters of a magnetic probe

    NASA Astrophysics Data System (ADS)

    Li, Fuming; Chen, Zhipeng; Zhu, Lizhi; Liu, Hai; Wang, Zhijiang; Zhuang, Ge

    2016-06-01

    This paper describes a novel method to determine the lumped-circuit parameters of a magnetic inductive probe for calibration by using Helmholtz coils with high frequency power supply (frequency range: 10 kHz-400 kHz). The whole calibration circuit system can be separated into two parts: "generator" circuit and "receiver" circuit. By implementing the Fourier transform, two analytical lumped-circuit models, with respect to these separated circuits, are constructed to obtain the transfer function between each other. Herein, the precise lumped-circuit parameters (including the resistance, inductance, and capacitance) of the magnetic probe can be determined by fitting the experimental data to the transfer function. Regarding the fitting results, the finite impedance of magnetic probe can be used to analyze the transmission of a high-frequency signal between magnetic probes, cables, and acquisition system.

  20. Magnetic Probe to Study Plasma Jets for Magneto-Inertial Fusion

    SciTech Connect

    Martens, Daniel; Hsu, Scott C.

    2012-08-16

    A probe has been constructed to measure the magnetic field of a plasma jet generated by a pulsed plasma rail-gun. The probe consists of two sets of three orthogonally-oriented commercial chip inductors to measure the three-dimensional magnetic field vector at two separate positions in order to give information about the magnetic field evolution within the jet. The strength and evolution of the magnetic field is one of many factors important in evaluating the use of supersonic plasma jets for forming imploding spherical plasma liners as a standoff driver for magneto-inertial fusion.

  1. Aberrated electron probes for magnetic spectroscopy with atomic resolution: Theory and practical aspects

    DOE PAGES

    Rusz, Ján; Idrobo, Juan Carlos

    2016-03-24

    It was recently proposed that electron magnetic circular dichroism (EMCD) can be measured in scanning transmission electron microscopy (STEM) with atomic resolution by tuning the phase distribution of a electron beam. Here, we describe the theoretical and practical aspects for the detection of out-of-plane and in-plane magnetization utilizing atomic size electron probes. Here we present the calculated optimized astigmatic probes and discuss how to achieve them experimentally.

  2. Aberrated electron probes for magnetic spectroscopy with atomic resolution: Theory and practical aspects

    SciTech Connect

    Rusz, Ján; Idrobo, Juan Carlos

    2016-03-24

    It was recently proposed that electron magnetic circular dichroism (EMCD) can be measured in scanning transmission electron microscopy (STEM) with atomic resolution by tuning the phase distribution of a electron beam. Here, we describe the theoretical and practical aspects for the detection of out-of-plane and in-plane magnetization utilizing atomic size electron probes. Here we present the calculated optimized astigmatic probes and discuss how to achieve them experimentally.

  3. Structural Analysis of a Magnetically Actuated Silicon Nitride Micro-Shutter for Space Applications

    NASA Technical Reports Server (NTRS)

    Loughlin, James P.; Fettig, Rainer K.; Moseley, S. Harvey; Kutyrev, Alexander S.; Mott, D. Brent; Obenschain, Arthur F. (Technical Monitor)

    2002-01-01

    Finite element models have been created to simulate the electrostatic and electromagnetic actuation of a 0.5gm silicon nitride micro-shutter for use in a spacebased Multi-object Spectrometer (MOS). The micro-shutter uses a torsion hinge to go from the closed, 0 degree, position, to the open, 90 degree position. Stresses in the torsion hinge are determined with a large deformation nonlinear finite element model. The simulation results are compared to experimental measurements of fabricated micro-shutter devices.

  4. Cobalt ferrite based magnetostrictive materials for magnetic stress sensor and actuator applications

    NASA Technical Reports Server (NTRS)

    Jiles, David C. (Inventor); Paulsen, Jason A. (Inventor); Snyder, John E. (Inventor); Lo, Chester C. H. (Inventor); Ring, Andrew P. (Inventor); Bormann, Keith A. (Inventor)

    2008-01-01

    Magnetostrictive material based on cobalt ferrite is described. The cobalt ferrite is substituted with transition metals (such manganese (Mn), chromium (Cr), zinc (Zn) and copper (Cu) or mixtures thereof) by substituting the transition metals for iron or cobalt to form substituted cobalt ferrite that provides mechanical properties that make the substituted cobalt ferrite material effective for use as sensors and actuators. The substitution of transition metals lowers the Curie temperature of the material (as compared to cobalt ferrite) while maintaining a suitable magnetostriction for stress sensing applications.

  5. Sealed magic angle spinning nuclear magnetic resonance probe and process for spectroscopy of hazardous samples

    SciTech Connect

    Cho, Herman M.; Washton, Nancy M.; Mueller, Karl T.; Sears, Jr., Jesse A.; Townsend, Mark R.; Ewing, James R.

    2016-06-14

    A magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) probe is described that includes double containment enclosures configured to seal and contain hazardous samples for analysis. The probe is of a modular design that ensures containment of hazardous samples during sample analysis while preserving spin speeds for superior NMR performance and convenience of operation.

  6. Inductive probe to measure the Earth’s magnetic field: a short note

    NASA Astrophysics Data System (ADS)

    Thompson, Frank

    2014-09-01

    This experiment provides ‘hands-on’ experience of Faraday’s law. By flipping a coil of wire (the probe) in a horizontal or vertical plane the two components of the Earth’s magnetic field are determined. The signal from the probe is recorded by a Picoscope ADC100.

  7. Parametric study of a pin-plane probe in moderately magnetized plasma

    NASA Astrophysics Data System (ADS)

    Binwal, S.; Gandhi, S.; Kabariya, H.; Karkari, S. K.

    2015-12-01

    The application of a planar Langmuir probe in magnetized plasma is found to be problematic due to significant perturbation of plasma along the magnetic field lines intercepting the probe surface. This causes the Ampere-Volts ‘I e(U)’ characteristics of the probe to deviate from its usual exponential law; in conjunction the electron saturation current I es is significantly reduced. Moreover estimating the electron temperature T e by considering the entire semi-log plot of I e(U) gives ambiguous values of T e. To address this problem, Pitts and Stangeby developed a formula for the reduction factor for I es. This formula depends on a number of uncertain parameters, namely; the ion temperature T +, electron cross-field diffusion coefficient {{D}\\bot ,\\text{e}} and the local potential hill V h estimated by applying a floating pin probe in the vicinity of the planar probe. Due to implicit dependence of these parameters on T e, the resulting analysis is not straightforward. This paper presents a parametric study of different parameters that influence the characteristics of a planar probe in magnetized plasma. For this purpose a pin-plane probe is constructed and applied in the magnetized plasma column. A comprehensive discussion is presented that highlights the practical methodology of using this technique for extracting useful information of plasma parameters in magnetized plasmas.

  8. Integrated sensing and actuation of dielectric elastomer actuator

    NASA Astrophysics Data System (ADS)

    Ye, Zhihang; Chen, Zheng

    2017-04-01

    Dielectric elastomer (DE) is a type of soft actuating material, the shape of which can be changed under electrical voltage stimuli. DE materials have great potential in applications involving energy harvesters, micro-manipulators, and adaptive optics. In this paper, a stripe DE actuator with integrated sensing and actuation is designed and fabricated, and characterized through several experiments. Considering the actuator's capacitor-like structure and its deform mechanism, detecting the actuator's displacement through the actuator's circuit feature is a potential approach. A self-sensing scheme that adds a high frequency probing signal into actuation signal is developed. A fast Fourier transform (FFT) algorithm is used to extract the magnitude change of the probing signal, and a non-linear fitting method and artificial neural network (ANN) approach are utilized to reflect the relationship between the probing signal and the actuator's displacement. Experimental results showed this structure has capability of performing self-sensing and actuation, simultaneously. With an enhanced ANN, the self-sensing scheme can achieve 2.5% accuracy.

  9. A Cryogenic Magnetostrictive Actuator using a Persistent High Temperature Superconducting Magnet, Part 1: Concept and Design. Part 1; Concept and Design

    NASA Technical Reports Server (NTRS)

    Horner, Garnett C.; Bromberg, Leslie; Teter, J. P.

    2001-01-01

    Cryogenic magnetostrictive materials, such as rare earth zinc crystals, offer high strains and high forces with minimally applied magnetic fields, making the material ideally suited for deformable optics applications. For cryogenic temperature applications, such as Next Generation Space Telescope (NGST), the use of superconducting magnets offer the possibility of a persistent mode of operation, i.e., the magnetostrictive material will maintain a strain field without power. High temperature superconductors (HTS) are attractive options if the temperature of operation is higher than 10 degrees Kelvin (K) and below 77 K. However, HTS wires have constraints that limit the minimum radius of winding, and even if good wires can be produced, the technology for joining superconducting wires does not exist. In this paper, the design and capabilities of a rare earth zinc magnetostrictive actuator using bulk HTS is described. Bulk superconductors can be fabricated in the sizes required with excellent superconducting properties. Equivalent permanent magnets, made with this inexpensive material, are persistent, do not require a persistent switch as in HTS wires, and can be made very small. These devices are charged using a technique which is similar to the one used for charging permanent magnets, e.g., by driving them into saturation. A small normal conducting coil can be used for charging or discharging. Very fast charging and discharging of HTS tubes, as short as 100 microseconds, has been demonstrated. Because of the magnetic field capability of the superconductor material, a very small amount of superconducting magnet material is needed to actuate the rare earth zinc. In this paper, several designs of actuators using YBCO and BSCCO 2212 superconducting materials are presented. Designs that include magnetic shielding to prevent interaction between adjacent actuators will also be described. Preliminary experimental results and comparison with theory for BSSCO 2212 with a

  10. A Cryogenic Magnetostrictive Actuator using a Persistent High Temperature Superconducting Magnet, Part 1: Concept and Design. Part 1; Concept and Design

    NASA Technical Reports Server (NTRS)

    Horner, Garnett C.; Bromberg, Leslie; Teter, J. P.

    2001-01-01

    Cryogenic magnetostrictive materials, such as rare earth zinc crystals, offer high strains and high forces with minimally applied magnetic fields, making the material ideally suited for deformable optics applications. For cryogenic temperature applications, such as Next Generation Space Telescope (NGST), the use of superconducting magnets offer the possibility of a persistent mode of operation, i.e., the magnetostrictive material will maintain a strain field without power. High temperature superconductors (HTS) are attractive options if the temperature of operation is higher than 10 degrees Kelvin (K) and below 77 K. However, HTS wires have constraints that limit the minimum radius of winding, and even if good wires can be produced, the technology for joining superconducting wires does not exist. In this paper, the design and capabilities of a rare earth zinc magnetostrictive actuator using bulk HTS is described. Bulk superconductors can be fabricated in the sizes required with excellent superconducting properties. Equivalent permanent magnets, made with this inexpensive material, are persistent, do not require a persistent switch as in HTS wires, and can be made very small. These devices are charged using a technique which is similar to the one used for charging permanent magnets, e.g., by driving them into saturation. A small normal conducting coil can be used for charging or discharging. Very fast charging and discharging of HTS tubes, as short as 100 microseconds, has been demonstrated. Because of the magnetic field capability of the superconductor material, a very small amount of superconducting magnet material is needed to actuate the rare earth zinc. In this paper, several designs of actuators using YBCO and BSCCO 2212 superconducting materials are presented. Designs that include magnetic shielding to prevent interaction between adjacent actuators will also be described. Preliminary experimental results and comparison with theory for BSSCO 2212 with a

  11. Standard Practices for Usage of Inductive Magnetic Field Probes with Application to Electric Propulsion Testing

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Hill, Carrie S.

    2013-01-01

    Inductive magnetic field probes (also known as B-dot probes and sometimes as B-probes or magnetic probes) are useful for performing measurements in electric space thrusters and various plasma accelerator applications where a time-varying magnetic field is present. Magnetic field probes have proven to be a mainstay in diagnosing plasma thrusters where changes occur rapidly with respect to time, providing the means to measure the magnetic fields produced by time-varying currents and even an indirect measure of the plasma current density through the application of Ampère's law. Examples of applications where this measurement technique has been employed include pulsed plasma thrusters and quasi-steady magnetoplasmadynamic thrusters. The Electric Propulsion Technical Committee (EPTC) of the American Institute of Aeronautics and Astronautics (AIAA) was asked to assemble a Committee on Standards (CoS) for Electric Propulsion Testing. The assembled CoS was tasked with developing Standards and Recommended Practices for various diagnostic techniques used in the evaluation of plasma thrusters. These include measurements that can yield either global information related to a thruster and its performance or detailed, local data related to the specific physical processes occurring in the plasma. This paper presents a summary of the standard, describing the preferred methods for fabrication, calibration, and usage of inductive magnetic field probes for use in diagnosing plasma thrusters. Inductive magnetic field probes (also called B-dot probes throughout this document) are commonly used in electric propulsion (EP) research and testing to measure unsteady magnetic fields produced by time-varying currents. The B-dot probe is relatively simple in construction, and requires minimal cost, making it a low-cost technique that is readily accessible to most researchers. While relatively simple, the design of a B-dot probe is not trivial and there are many opportunities for errors in

  12. Application of a portable nuclear magnetic resonance surface probe to porous media.

    PubMed

    Marko, Andriy; Wolter, Bernd; Arnold, Walter

    2007-03-01

    A portable nuclear magnetic resonance (NMR) surface probe was used to determine the time-dependent self-diffusion coefficient D(t) of water molecules in two fluid-filled porous media. The measuring equipment and the inhomogeneous magnetic fields in the sensitive volume of the probe are described. It is discussed how to evaluate D(t) using a surface probe from the primary and stimulated echoes generated in three-pulse experiments. Furthermore, the evaluation of D(t) allows one to determine the geometrical structure of porous materials.

  13. Magnetic and Langmuir Probe Measurements on the Plasmoid Thruster Experiment (PTX)

    NASA Technical Reports Server (NTRS)

    Koelfgen, Syri J.; Eskridge, Richard; Fimognari, Peter; Hawk, Clark W.; Lee, Mike; Martin, Adam

    2004-01-01

    The Plasmoid Thruster Experiment (PTX) operates by inductively producing plasmoids in a conical theta-pinch coil and subsequently ejecting them at high velocity. An overview of PTX is described in a companion paper. The shape and magnetic field structure of the translating plasmoids will be measured with of an array of inductive magnetic field probes. Six sets of two B-dot probes (for a total of twelve probes) have been constructed for measuring B(sub z) and B(sub theta), the axial and azimuthal components of the magnetic field. The probes were calibrated with a Helmholtz coil, driven alternately by a high-voltage pulser or a signal generator. The probes are wound on a G-10 form, and have an average (calibrated) NA of 9.37 x 10(exp -5) square meters, where N is the number of turns and A is cross-sectional area. The frequency response of the probes was measured over the range from 1 kHz to 10 MHZ. The electron number density n(sub e), electron temperature T(sub e) and velocity v will be determined from measurements taken with a quadruple Langmuir probe, situated in the exhaust chamber. Three of the four probes on the quadruple probe sample the current-voltage characteristic, and from this yield measurements of T(sub e) and n(sub e). The fourth probe provides a measurement of plasma flow velocity. A 6-inch long alumina rod, hollowed with four holes to house the probe wires, is being used to construct the quadruple probe. A variety of propellants will be used, including hydrogen, nitrogen and argon. From the measurements of the plasmoid mass, density, temperature, and velocity, the basic propulsion characteristics of PTX will be evaluated.

  14. Double-tuned single coil probe for nuclear magnetic resonance spectrometer

    SciTech Connect

    McKay, R.A.

    1984-05-01

    A double-tuned single coil probe for a nuclear magnetic resonance spectrometer having improved sensitivity is described comprising a double-tuned circuit means in which the low frequency irradiation is fed to a transmission line through an inductor means. The double-tuned circuit means of the invention may be remotely disposed from the magnetic field which results in greater sensitivity.

  15. Double-resonance 14N nuclear-magnetic-resonance probe for single-crystal studies

    NASA Astrophysics Data System (ADS)

    Naito, Akira; McDowell, Charles A.

    1989-06-01

    A double-resonance 14N nuclear-magnetic-resonance (NMR) probe suitable for single-crystal studies is described. The 14N and 1H sample coils are wound as coaxial solenoids and used instead of a doubly tuned single coil to tune over the required frequency range of the 14N channel. The choice of materials for the probe body and the wire size for the sample and impedance matching coils were chosen carefully to minimize spurious ringing phenomena, which is troublesome in probe designs for solid-state NMR. The probe has a very accurate goniometer since the resolution of 14N NMR signals is high.

  16. Modeling and Measurements by Hall probes of Magnetic Structures of Undulators HU256

    SciTech Connect

    Batrakov, A.; Churkin, I.; Ilyin, I.; Steshov, A.; Vobly, P.; Briquez, F.; Chubar, O.; Dael, A.; Roux, G.; Valleau, M.

    2007-01-19

    The magnetic calculations of the individual dipoles and dipoles in 'undulator environment' were executed by means of Mermaid 3D Code and these results were confirmed by magnetic measurements of the individual dipoles and the assembled undulators. The magnetic parameters of all dipoles were estimated on basis of the mechanical measurement of the dipole characteristics (pole gap, yoke width, coil position) and the main dependences obtained from magnetic calculations and measurements. These parameters were used for optimal placing of the dipoles in undulators (sorting). The special Hall probe system was designed and manufactured for magnetic measurements of the undulators. It allowed us to observe the inner structure of the magnetic fields. At a magnetic field measurement accuracy of {+-} 15 {mu}T the accuracy of the 1st integral calculated on the basis of the measured magnetic fields is {approx} 50 {mu}Tm. All three undulators were magnetically measured at BINP and are being re-measured at Soleil after transportation.

  17. On Floating Potential of Emissive Probes in a Partially-Magnetized Plasma

    NASA Astrophysics Data System (ADS)

    Raitses, Yevgeny; Kraus, Brian

    2016-10-01

    We compare measurements of plasma potential in a cross-field Penning discharge from two probes: swept biased Langmuir probe and floating emissive probe. The plasma potential was deduced from the first derivative of the Langmuir probe characteristic. In previous studies, the emissive and swept biased probes were placed at the channel exit of a Hall thruster (HT). Measurements showed that the emissive probe floats below the plasma potential, in agreement with conventional theories. However, recent measurements in the Penning discharge indicate a floating potential of a strongly-emitting hot probe above the plasma potential. In both probe applications, xenon plasmas have magnetized electrons and non-magnetized ions with similar plasma densities (1010 - 1011 cm-3) . Though their electron temperatures differ by an order of magnitude (Penning 5 eV, HT 50 eV), this difference cannot explain the difference in measurement values of the hot floating potential because both temperatures are much higher than the emitting wire. In this work, we investigate how the ion velocity and other plasma parameters affect this discrepancy between probe measurements of the plasma potential. This work was supported by DOE contract DE-AC02-09CH11466.

  18. Nanoscale magnetic field mapping with a single spin scanning probe magnetometer

    SciTech Connect

    Rondin, L.; Tetienne, J.-P.; Spinicelli, P.; Roch, J.-F.; Jacques, V.; Dal Savio, C.; Karrai, K.; Dantelle, G.; Thiaville, A.; Rohart, S.

    2012-04-09

    We demonstrate quantitative magnetic field mapping with nanoscale resolution, by applying a lock-in technique on the electron spin resonance frequency of a single nitrogen-vacancy defect placed at the apex of an atomic force microscope tip. In addition, we report an all-optical magnetic imaging technique which is sensitive to large off-axis magnetic fields, thus extending the operation range of diamond-based magnetometry. Both techniques are illustrated by using a magnetic hard disk as a test sample. Owing to the non-perturbing and quantitative nature of the magnetic probe, this work should open up numerous perspectives in nanomagnetism and spintronics.

  19. Planetary magnetism. [Mariner, Venera and Pioneer probe results

    NASA Technical Reports Server (NTRS)

    Russell, C. T.

    1979-01-01

    Recent data on planetary magnetism are reviewed, with attention given to information obtained by Mariner 10 at Mercury, from Venera 9 and 10 orbiting Venus, and Pioneer spacecraft flying past Jupiter. In addition, less recent magnetic measurements of Mars are reconsidered. Doubts about whether Mars has an active dynamo at present are mentioned, and further planetary magnetic assessments are suggested. In particular, the need to refine knowledge of multipole moments is stressed.

  20. Planetary magnetism. [Mariner, Venera and Pioneer probe results

    NASA Technical Reports Server (NTRS)

    Russell, C. T.

    1979-01-01

    Recent data on planetary magnetism are reviewed, with attention given to information obtained by Mariner 10 at Mercury, from Venera 9 and 10 orbiting Venus, and Pioneer spacecraft flying past Jupiter. In addition, less recent magnetic measurements of Mars are reconsidered. Doubts about whether Mars has an active dynamo at present are mentioned, and further planetary magnetic assessments are suggested. In particular, the need to refine knowledge of multipole moments is stressed.

  1. Probing magnetic microstructures with quasi-ballistic Hall crosses

    NASA Astrophysics Data System (ADS)

    Fasbender, S.; Schluck, J.; Cerchez, M.; Heinzel, T.; Sievers, S.; Pierz, K.; Schumacher, H. W.

    2016-03-01

    Hall sensing is performed on a localized magnetic field pattern using a quasi-ballistic Hall cross device. The Hall resistance shows a pronounced peak as a function of the magnetic field amplitude which is absent in the magnetization hysteresis loop. This non-monotonic response exemplifies qualitatively the failure of conventional Hall sensing. It is demonstrated how, by using a numerical simulation based on the Landauer-Büttiker model, the amplitude of the magnetic field profile can be determined from such measurements.

  2. Muons probe magnetism and hydrogen interaction in graphene

    NASA Astrophysics Data System (ADS)

    Riccò, M.; Aramini, M.; Mazzani, M.; Pontiroli, D.; Gaboardi, M.; Yazyev, O. V.

    2013-12-01

    Muon spin resonance (μSR) is a powerful technique for investigating the local magnetic fields in materials through implanted muons. Here we report a μSR study of chemically produced thermally exfoliated graphene. Our results provide an experimental answer to the many theoretical investigations of magnetic properties of graphene. The observed muon spin precession is attributed to a localized muon-hydrogen nuclear dipolar interaction rather than to a hyperfine interaction with magnetic electrons. This proves the absence of magnetism in chemically produced thermally exfoliated graphene.

  3. Magnetically actuated tissue engineered scaffold: insights into mechanism of physical stimulation

    PubMed Central

    Sapir-Lekhovitser, Yulia; Rotenberg, Menahem Y.; Jopp, Juergen; Friedman, Gary; Polyak, Boris; Cohen, Smadar

    2016-01-01

    Providing the right stimulatory conditions resulting in efficient tissue promoting microenvironment in vitro and in vivo is one of the ultimate goals in tissue development for regenerative medicine. It has been shown that in addition to molecular signals (e.g. growth factors) physical cues are also required for generation of functional cell constructs. These cues are particularly relevant to engineering of biological tissues, within which mechanical stress activates mechano-sensitive receptors, initiating biochemical pathways which lead to the production of functionally mature tissue. Uniform magnetic fields coupled with magnetizable nanoparticles embedded within three dimensional (3D) scaffold structures remotely create transient physical forces that can be transferrable to cells present in close proximity to the nanoparticles. This study investigated the hypothesis that magnetically responsive alginate scaffold can undergo reversible shape deformation due to alignment of scaffold’s walls in a uniform magnetic field. Using custom made Helmholtz coil setup adapted to an Atomic Force Microscope we monitored changes in matrix dimensions in situ as a function of applied magnetic field, concentration of magnetic particles within the scaffold wall structure and rigidity of the matrix. Our results show that magnetically responsive scaffolds exposed to an externally applied time-varying uniform magnetic field undergo a reversible shape deformation. This indicates on possibility of generating bending/stretching forces that may exert a mechanical effect on cells due to alternating pattern of scaffold wall alignment and relaxation. We suggest that the matrix structure deformation is produced by immobilized magnetic nanoparticles within the matrix walls resulting in a collective alignment of scaffold walls upon magnetization. The estimated mechanical force that can be imparted on cells grown on the scaffold wall at experimental conditions is in the order of 1 pN, which

  4. Magnetically actuated tissue engineered scaffold: insights into mechanism of physical stimulation

    NASA Astrophysics Data System (ADS)

    Sapir-Lekhovitser, Yulia; Rotenberg, Menahem Y.; Jopp, Juergen; Friedman, Gary; Polyak, Boris; Cohen, Smadar

    2016-02-01

    Providing the right stimulatory conditions resulting in efficient tissue promoting microenvironment in vitro and in vivo is one of the ultimate goals in tissue development for regenerative medicine. It has been shown that in addition to molecular signals (e.g. growth factors) physical cues are also required for generation of functional cell constructs. These cues are particularly relevant to engineering of biological tissues, within which mechanical stress activates mechano-sensitive receptors, initiating biochemical pathways which lead to the production of functionally mature tissue. Uniform magnetic fields coupled with magnetizable nanoparticles embedded within three dimensional (3D) scaffold structures remotely create transient physical forces that can be transferrable to cells present in close proximity to the nanoparticles. This study investigated the hypothesis that magnetically responsive alginate scaffold can undergo reversible shape deformation due to alignment of scaffold's walls in a uniform magnetic field. Using custom made Helmholtz coil setup adapted to an Atomic Force Microscope we monitored changes in matrix dimensions in situ as a function of applied magnetic field, concentration of magnetic particles within the scaffold wall structure and rigidity of the matrix. Our results show that magnetically responsive scaffolds exposed to an externally applied time-varying uniform magnetic field undergo a reversible shape deformation. This indicates on possibility of generating bending/stretching forces that may exert a mechanical effect on cells due to alternating pattern of scaffold wall alignment and relaxation. We suggest that the matrix structure deformation is produced by immobilized magnetic nanoparticles within the matrix walls resulting in a collective alignment of scaffold walls upon magnetization. The estimated mechanical force that can be imparted on cells grown on the scaffold wall at experimental conditions is in the order of 1 pN, which

  5. Single Langmuir probe characteristic in a magnetized plasma at the text tokamak

    SciTech Connect

    Jachmich, Stefan

    1995-05-01

    A single Langmuir probe tip was used at TEXT-Upgrade to obtain I-V characteristics in a magnetized plasma. Noisy data were reduced by a boxcar-averaging routine. Unexpected effects, namely nonsaturation of ion current, hysterises in the characteristics and I(V)-data were observed, which are in disagreement to the common single probe model. A double probe model allows parameterization of the I(V) curves and to determine the plasma properties in the scrape-off layer. It is shown in this model that a Langmuir probe does perturb the local space potential in the plasma. Comparisons were made with the triple probe technique of measuring temperatures. The nonsaturation of ion current leads to an error in the triple probe technique of order 20%.

  6. Probing intergalactic magnetic fields with simulations of electromagnetic cascades

    NASA Astrophysics Data System (ADS)

    Alves Batista, Rafael; Saveliev, Andrey; Sigl, Günter; Vachaspati, Tanmay

    2016-10-01

    We determine the effect of intergalactic magnetic fields on the distribution of high-energy gamma rays by performing three-dimensional Monte Carlo simulations of the development of gamma-ray-induced electromagnetic cascades in the magnetized intergalactic medium. We employ the so-called "Large Sphere Observer" method to efficiently simulate blazar gamma ray halos. We study magnetic fields with a Batchelor spectrum and with maximal left- and right-handed helicities. We also consider the case of sources whose jets are tilted with respect to the line of sight. We verify the formation of extended gamma ray halos around the source direction, and observe spiral-like patterns if the magnetic field is helical. We apply the Q -statistics to the simulated halos to extract their spiral nature and also propose an alternative method, the S -statistics. Both methods provide a quantitative way to infer the helicity of the intervening magnetic fields from the morphology of individual blazar halos for magnetic field strengths B ≳10-15 G and magnetic coherence lengths Lc≳100 Mpc . We show that the S -statistics has a better performance than the Q -statistics when assessing magnetic helicity from the simulated halos.

  7. Probing the Magnetic Causes of CMEs: Free Magnetic Energy More Important Than Either Size Or Twist

    NASA Technical Reports Server (NTRS)

    Falconer, D. A.; Moore, R. L.; Gary, G. A.

    2006-01-01

    To probe the magnetic causes of CMEs, we have examined three types of magnetic measures: size, twist and total nonpotentiality (or total free magnetic energy) of an active region. Total nonpotentiality is roughly the product of size times twist. For predominately bipolar active regions, we have found that total nonpotentiality measures have the strongest correlation with future CME productivity (approx. 75% prediction success rate), while size and twist measures each have a weaker correlation with future CME productivity (approx. 65% prediction success rate) (Falconer, Moore, & Gary, ApJ, 644, 2006). For multipolar active regions, we find that the CME-prediction success rates for total nonpotentiality and size are about the same as for bipolar active regions. We also find that the size measure correlation with CME productivity is nearly all due to the contribution of size to total nonpotentiality. We have a total nonpotentiality measure that can be obtained from a line-of-sight magnetogram of the active region and that is as strongly correlated with CME productivity as are any of our total-nonpotentiality measures from deprojected vector magnetograms. We plan to further expand our sample by using MDI magnetograms of each active region in our sample to determine its total nonpotentiality and size on each day that the active region was within 30 deg. of disk center. The resulting increase in sample size will improve our statistics and allow us to investigate whether the nonpotentiality threshold for CME production is nearly the same or significantly different for multipolar regions than for bipolar regions. In addition, we will investigate the time rates of change of size and total nonpotentiality as additional causes of CME productivity.

  8. Probing the Magnetic Causes of CMEs: Free Magnetic Energy More Important Than Either Size Or Twist

    NASA Technical Reports Server (NTRS)

    Falconer, D. A.; Moore, R. L.; Gary, G. A.

    2006-01-01

    To probe the magnetic causes of CMEs, we have examined three types of magnetic measures: size, twist and total nonpotentiality (or total free magnetic energy) of an active region. Total nonpotentiality is roughly the product of size times twist. For predominately bipolar active regions, we have found that total nonpotentiality measures have the strongest correlation with future CME productivity (approx. 75% prediction success rate), while size and twist measures each have a weaker correlation with future CME productivity (approx. 65% prediction success rate) (Falconer, Moore, & Gary, ApJ, 644, 2006). For multipolar active regions, we find that the CME-prediction success rates for total nonpotentiality and size are about the same as for bipolar active regions. We also find that the size measure correlation with CME productivity is nearly all due to the contribution of size to total nonpotentiality. We have a total nonpotentiality measure that can be obtained from a line-of-sight magnetogram of the active region and that is as strongly correlated with CME productivity as are any of our total-nonpotentiality measures from deprojected vector magnetograms. We plan to further expand our sample by using MDI magnetograms of each active region in our sample to determine its total nonpotentiality and size on each day that the active region was within 30 deg. of disk center. The resulting increase in sample size will improve our statistics and allow us to investigate whether the nonpotentiality threshold for CME production is nearly the same or significantly different for multipolar regions than for bipolar regions. In addition, we will investigate the time rates of change of size and total nonpotentiality as additional causes of CME productivity.

  9. Analysis of the Distribution of Magnetic Fluid inside Tumors by a Giant Magnetoresistance Probe

    PubMed Central

    Gooneratne, Chinthaka P.; Kurnicki, Adam; Yamada, Sotoshi; Mukhopadhyay, Subhas C.; Kosel, Jürgen

    2013-01-01

    Magnetic fluid hyperthermia (MFH) therapy uses the magnetic component of electromagnetic fields in the radiofrequency spectrum to couple energy to magnetic nanoparticles inside tumors. In MFH therapy, magnetic fluid is injected into tumors and an alternating current (AC) magnetic flux is applied to heat the magnetic fluid- filled tumor. If the temperature can be maintained at the therapeutic threshold of 42°C for 30 minutes or more, the tumor cells can be destroyed. Analyzing the distribution of the magnetic fluid injected into tumors prior to the heating step in MFH therapy is an essential criterion for homogenous heating of tumors, since a decision can then be taken on the strength and localization of the applied external AC magnetic flux density needed to destroy the tumor without affecting healthy cells. This paper proposes a methodology for analyzing the distribution of magnetic fluid in a tumor by a specifically designed giant magnetoresistance (GMR) probe prior to MFH heat treatment. Experimental results analyzing the distribution of magnetic fluid suggest that different magnetic fluid weight densities could be estimated inside a single tumor by the GMR probe. PMID:24312280

  10. Analysis of the distribution of magnetic fluid inside tumors by a giant magnetoresistance probe.

    PubMed

    Gooneratne, Chinthaka P; Kurnicki, Adam; Yamada, Sotoshi; Mukhopadhyay, Subhas C; Kosel, Jürgen

    2013-01-01

    Magnetic fluid hyperthermia (MFH) therapy uses the magnetic component of electromagnetic fields in the radiofrequency spectrum to couple energy to magnetic nanoparticles inside tumors. In MFH therapy, magnetic fluid is injected into tumors and an alternating current (AC) magnetic flux is applied to heat the magnetic fluid- filled tumor. If the temperature can be maintained at the therapeutic threshold of 42 °C for 30 minutes or more, the tumor cells can be destroyed. Analyzing the distribution of the magnetic fluid injected into tumors prior to the heating step in MFH therapy is an essential criterion for homogenous heating of tumors, since a decision can then be taken on the strength and localization of the applied external AC magnetic flux density needed to destroy the tumor without affecting healthy cells. This paper proposes a methodology for analyzing the distribution of magnetic fluid in a tumor by a specifically designed giant magnetoresistance (GMR) probe prior to MFH heat treatment. Experimental results analyzing the distribution of magnetic fluid suggest that different magnetic fluid weight densities could be estimated inside a single tumor by the GMR probe.

  11. Magnetically Insulated Baffled Probe Measurement of Unfiltered Fluctuating Space Potential in the Texas Helimak

    NASA Astrophysics Data System (ADS)

    Koepke, M. E.; Nogami, S. H.; Demidov, V. I.; Williams, C. B.; Gentle, K.

    2016-10-01

    Success is reported in employing magnetically insulated baffled (MIB) probes for the measurement of fluctuating space potential in the Texas Helimak. The combination of the MIB probe and an unbaffled probe provides the necessary ingredients for determining cross-field transport without contamination between fluctuating space potential and electron temperature. The performance of the MIB probe is quantified by its ability to produce a probe characteristic with partially reduced magnitude of electron saturation current. The baffled probe employed in the 2016 experiments performed optimally (i.e., the magnitude of the electron saturation current is equal to the magnitude of the ion saturation current), meaning there is no difference between the probe floating potential and the space potential. The performance of the baffled probe is compared to the performance of the plug probe, tested in 2015 on the Texas Helimak. Recent radial scans at the plasma edge of unfiltered fluctuating space potential are presented. Travel support from a Big XII Faculty Fellowship is gratefully acknowledged. Collaboration in probe construction with and experimental assistance by K. Carter are gratefully acknowledged.

  12. Development of a fiber based Raman probe compatible with interventional magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Ashok, Praveen C.; Praveen, Bavishna B.; Rube, Martin; Cox, Benjamin; Melzer, Andreas; Dholakia, Kishan

    2014-02-01

    Raman spectroscopy has proven to be a powerful tool for discriminating between normal and abnormal tissue types. Fiber based Raman probes have demonstrated its potential for in vivo disease diagnostics. Combining Raman spectroscopy with Magnetic Resonance Imaging (MRI) opens up new avenues for MR guided minimally invasive optical biopsy. Although Raman probes are commercially available, they are not compatible with a MRI environment due to the metallic components which are used to align the micro-optic components such as filters and lenses at the probe head. Additionally they are not mechanically compatible with a typical surgical environment as factors such as sterility and length of the probe are not addressed in those designs. We have developed an MRI compatible fiber Raman probe with a disposable probe head hence maintaining sterility. The probe head was specially designed to avoid any material that would cause MR imaging artefacts. The probe head that goes into patient's body had a diameter <1.5 mm so that it is compatible with biopsy needles and catheters. The probe has been tested in MR environment and has been proven to be capable of obtaining Raman signal while the probe is under real-time MR guidance.

  13. Three-dimensional sensitivity mapping of a handheld magnetic probe for sentinel lymph node biopsy

    NASA Astrophysics Data System (ADS)

    Kuwahata, Akihiro; Chikaki, Shinichi; Ergin, Aslı; Kaneko, Miki; Kusakabe, Moriaki; Sekino, Masaki

    2017-05-01

    An experimental apparatus for three-dimensional sensitivity mapping of a handheld magnetic probe with a permanent magnet and a Hall sensor was developed. To optimize the shapes and sizes of the magnets, the sensitivity mappings of two types of magnets, column- and cone-type magnets, were evaluated by the experimental apparatus. The longitudinal sensitivities of column and cone types are 8 and 9 mm, respectively, for 5 μL of magnetic nanoparticles. The measured longitudinal sensitivities agree well with the sensitivities calculated by the finite element method. Furthermore, the maximum lateral resolutions of column and cone types are 4.1 and 3.7 mm, respectively. In terms of the directionality, the sensitivities of column and cone types of the angle of 90° with respect to the probe axis fall approximately to 72% and 50% at 6 mm distance from the probe head, indicating that the cone type has high directionality due to its sharp shape. The measurement of sensitivity mapping revealed that the characteristics of the cone-type magnet are superior to that of the column-type magnet for the identification of sentinel lymph nodes.

  14. Magnetic actuated pH-responsive hydrogel-based soft micro-robot for targeted drug delivery

    NASA Astrophysics Data System (ADS)

    Li, Hao; Go, Gwangjun; Ko, Seong Yong; Park, Jong-Oh; Park, Sukho

    2016-02-01

    For drug delivery in cancer therapy, various stimuli-responsive hydrogel-based micro-devices have been studied with great interest. Here, we present a new concept for a hybrid actuated soft microrobot targeted drug delivery. The proposed soft microrobot consists of a hydrogel bilayer structure of 2-hydroxyethyl methacrylate (PHEMA) and poly (ethylene glycol) acrylate (PEGDA) with iron (II, III) oxide particles (Fe3O4). The PHEMA layer as a pH-responsive gel is used for a trapping and unfolding motion of the soft microrobot in pH-varying solution, and the PEGDA-with-Fe3O4 layer is employed for the locomotion of the soft microrobot in the magnetic field. The bilayer soft microrobot was fabricated by a conventional photolithography procedure and its characteristics were analyzed and presented. To evaluate the trapping performance and the motility of the soft microrobot, test solutions with different pH values and an electromagnetic actuation (EMA) system were used. First, the soft microrobot showed its full trapping motion at about pH 9.58 and its unfolding motion at about pH 2.6. Second, the soft microrobot showed a moving velocity of about 600 μm s-1 through the generated magnetic field of the EMA system. Finally, we fabricated the real anti-cancer drug microbeads (PCL-DTX) and executed the cytotoxicity test using the mammary carcinoma cells (4T1). The viability of the 4T1 cells treated with the proposed microrobot and the PCL-DTX microbeads decreased to 70.25 ± 1.52%. The result demonstrated that the soft microrobot can be moved to a target position by the EMA system and can release a small amount of beads by the pH variation and the robot exhibited no toxicity to the cells. In the future, we expect that the proposed soft microrobot can be applied to a new tumor-therapeutic tool that can move to a target tumor and release anti-tumor drugs.

  15. LabVIEW software for analyzing Langmuir probe characteristics in magnetized plasma

    NASA Astrophysics Data System (ADS)

    Gandhi, S.; Binwal, S.; Kabariya, H.; Karkari, S. K.

    2016-03-01

    This paper describes the methodology for processing Ampere-Volts (I-V) characteristics of the Langmuir probe in magnetized plasma using graphical programming language based on LabVIEW. Computing the plasma parameters from I-V characteristic involves several steps that include signal processing, interpolation, linear and non-linear curve fitting based on physical models, finding the derivatives of the experimental curve and determining the zero-crossing of the probe current as a function of the applied voltage. These operations are practically tedious to perform manually causing systematic errors in output parameters. To overcome this challenge, software is developed to analyze the planar Langmuir probe characteristics in magnetized plasma. The software allows simultaneous display of different plasma parameters that helps to verify the consistency of the analyzed plasma parameters with the standard probe theory. Using this software, plasma parameters are obtained in a linear plasma device and its characteristics are discussed.

  16. Probing the magnetic fields in L1415 and L1389

    NASA Astrophysics Data System (ADS)

    Soam, A.; Lee, Chang Won; Maheswar, G.; Kim, Gwanjeong; Neha, S.; Kim, Mi-Ryang

    2017-01-01

    We present the R-band polarimetric results towards two nebulae L1415 and L1389 containing low-luminosity stars. Aim of this study is to understand the role played by magnetic fields in formation of low-luminosity objects. Linear polarization arises due to dichroism of the background starlight projected on the cloud providing the plane-of-the sky magnetic field orientation. The offsets between mean magnetic field directions obtained towards L1415 and L1389 and the projected outflow axes are found to be 35° and 12°, respectively. The offset between cloud minor axes and mean envelope magnetic field direction in L1415 and L1389 are 50° and 87°, respectively. To estimate the magnetic field strength by using the updated Chandrasekhar-Fermi (CF) relation, we obtained the 12CO(J = 1-0) line velocity dispersion value towards L1415 cloud using the Taeduk Radio Astronomical Observatory single dish observations. The values of Bpos in L1415 and L1389 are found to be 28 and 149 μG using CF technique and 23 and 140 μG using structure function analysis, respectively. The values of Bpos in these clouds are found to be consistent using both the techniques. By combining the present results with those obtained from our previous study of magnetic fields in cores with Very Low Luminosity Objects (VeLLOs), we attempt to improve the sample of cores with low-luminosity protostars and bridge the gap between the understanding of importance of magnetic fields in cores with VeLLOs and low-luminosity protostars. The results of this work and that of our previous work show that the outflow directions are aligned with envelope magnetic fields of the clouds.

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

    SciTech Connect

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

    2008-06-01

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

  18. Controlled release of doxorubicin loaded within magnetic thermo-responsive nanocarriers under magnetic and thermal actuation in a microfluidic channel.

    PubMed

    Pernia Leal, Manuel; Torti, Andrea; Riedinger, Andreas; La Fleur, Rocco; Petti, Daniela; Cingolani, Roberto; Bertacco, Riccardo; Pellegrino, Teresa

    2012-12-21

    We report a procedure to grow thermo-responsive polymer shells at the surface of magnetic nanocarriers made of multiple iron oxide superparamagnetic nanoparticles embedded in poly(maleic anhydride-alt-1-ocatadecene) polymer nanobeads. Depending on the comonomers and on their relative composition, tunable phase transition temperatures in the range between 26 and 47 °C under physiological conditions could be achieved. Using a suitable microfluidic platform combining magnetic nanostructures and channels mimicking capillaries of the circulatory system, we demonstrate that thermo-responsive nanobeads are suitable for localized drug delivery with combined thermal and magnetic activation. Below the critical temperature nanobeads are stable in suspension, retain their cargo, and cannot be easily trapped by magnetic fields. Increasing the temperature above the critical temperature causes the aggregation of nanobeads, forming clusters with a magnetic moment high enough to permit their capture by suitable magnetic gradients in close proximity to the targeted zone. At the same time the polymer swelling activates drug release, with characteristic times on the order of one hour for flow rates of the same order as those of blood in capillaries.

  19. Using NV centers to probe magnetization dynamics in normal metal/magnetic insulator hybrid system at the nanoscale

    NASA Astrophysics Data System (ADS)

    Zhang, Huiliang; Ku, Mark J. H.; Han, Minyong; Casola, Francesco; van der Sar, Toeno; Yacoby, Amir; Walsworth, Ronald L.

    2016-05-01

    Understanding magnetization dynamics induced by electric current is of great interest for both fundamental and practical reasons. Great endeavor has been dedicated to spin-orbit torques (SOT) in metallic structures, while quantitative study of analogous phenomena in magnetic insulators remains challenging where transport measurements are not feasible. Recently we have developed techniques using nitrogen vacancy (NV) centers in diamond to probe few-nanometre-scale correlated-electron magnetic excitations (i.e., spin waves). Here we demonstrate how this powerful tool can be implemented to study magnetization dynamics inside ferromagnetic insulator, Yttrium iron garnet (YIG) with spin injection from electrical current through normal metal (Platinum in our case). Particularly our work will focus on NV magnetic detection, imaging, and spectroscopy of coherent auto-oscillations in Pt/YIG microdisc. Magnetic fluctuations and local temperature measurements, both with nearby NV centers, will also be interesting topics relevant to SOT physics in Pt/YIG hybrid system.

  20. Magnetic and electric field alignments of cellulose chains for electro-active paper actuator

    NASA Astrophysics Data System (ADS)

    Yun, Sungryul; Chen, Yi; Lee, Sang Woo; Kim, Jaehwan; Kim, Heung Soo

    2008-03-01

    To improve the piezoelectricity of cellulose electro-active paper (EAPap), electrical field and magnetic field alignments were investigated. EAPap is made with cellulose by dissolving cotton pulp and regenerating cellulose with aligned cellulose fibers. EAPap made with cellulose has piezoelectric property due to its structural crystallinity. Noncentro-symmetric crystal structure of EAPap, which is mostly cellulose II, can exhibit piezoelectricity. However, EAPap has ordered crystal parts as well as disordered parts of cellulose. Thus, well alignment of cellulose chains in EAPap is important to improve its piezoelectricity. In this paper, uniaxial alignments of cellulose chains were investigated by applying electric field and magnetic field. As exposing different fields to EAPap samples, the changed characteristics were analyzed by X-Ray diffractometer (XRD) and Scanning electron microscopy (SEM). Finally, the piezoelectricity of EAPap samples was evaluated by comparing their piezoelectric charge constant [d 31]. As increasing applied electric field up to 40V/mm, d 31 value was gradually improved due to increased cellulose crystallinity as well as alignment of cellulose chains. Also the alignment of cellulose chains was improved with increasing the exposing time to magnetic field (5.3T) and well alignment was achieved by exposing EAPap sample on the magnetic field for 180min.

  1. Achieving nutrient pumping and strain stimulus by magnetic actuation of tubular scaffolds

    NASA Astrophysics Data System (ADS)

    Mack, Julia J.; Cox, Brian N.; Sudre, Olivier; Corrin, Abigail A.; Lucato, Sergio L. dos Santos e.; Ma, Chelsea; Andrew, Jennifer S.

    2009-10-01

    Methods of forming magnetically actuable tubular scaffolds for use in engineering smooth muscle tissues such as those of the intestines, blood vessels, and urethra are described. The scaffolds are fabricated from sheets of electrospun fibrils of biocompatible and biodegradable polymers containing spatially uniform dispersions of nanoscale magnetic Fe2O3 particles. The sheets are wound into tubes, which are designed to contain a uniform seeding of cells from inner to outer layer in the wound structure, as reported elsewhere. The tubes undergo a crimping deformation when exposed to a magnetic field, similar to the deformation of peristalsis. The deformation creates both strains in the tube walls and fluid pumping through the walls, which are desired to promote cell proliferation and differentiation. In this paper, the physical properties of the electrospun sheets and the wound tubes are reported, including the magnitude of the displacements and the flux through the walls induced by a given magnetic field. A model is presented that can be used to predict the deformation and fluid flow for given field strength and material and geometrical parameters. The model can be used to optimize tube design and interpret measurements from future experiments on cell culture.

  2. Design and Application of Hybrid Magnetic Field-Eddy Current Probe

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz; Wallace, Terryl; Newman, Andy; Leser, Paul; Simpson, John

    2013-01-01

    The incorporation of magnetic field sensors into eddy current probes can result in novel probe designs with unique performance characteristics. One such example is a recently developed electromagnetic probe consisting of a two-channel magnetoresistive sensor with an embedded single-strand eddy current inducer. Magnetic flux leakage maps of ferrous materials are generated from the DC sensor response while high-resolution eddy current imaging is simultaneously performed at frequencies up to 5 megahertz. In this work the design and optimization of this probe will be presented, along with an application toward analysis of sensory materials with embedded ferromagnetic shape-memory alloy (FSMA) particles. The sensory material is designed to produce a paramagnetic to ferromagnetic transition in the FSMA particles under strain. Mapping of the stray magnetic field and eddy current response of the sample with the hybrid probe can thereby image locations in the structure which have experienced an overstrain condition. Numerical modeling of the probe response is performed with good agreement with experimental results.

  3. First experiments probing the collision of parallel magnetic fields using laser-produced plasmas

    SciTech Connect

    Rosenberg, M. J.; Li, C. K.; Fox, W.; Igumenshchev, I.; Seguin, F. H.; Town, R. P.; Frenje, J. A.; Stoeckl, C.; Glebov, V.; Petrasso, R. D.

    2015-04-08

    Novel experiments to study the strongly-driven collision of parallel magnetic fields in β~10, laser-produced plasmas have been conducted using monoenergetic proton radiography. These experiments were designed to probe the process of magnetic flux pileup, which has been identified in prior laser-plasma experiments as a key physical mechanism in the reconnection of anti-parallel magnetic fields when the reconnection inflow is dominated by strong plasma flows. In the present experiments using colliding plasmas carrying parallel magnetic fields, the magnetic flux is found to be conserved and slightly compressed in the collision region. Two-dimensional (2D) particle-in-cell (PIC) simulations predict a stronger flux compression and amplification of the magnetic field strength, and this discrepancy is attributed to the three-dimensional (3D) collision geometry. Future experiments may drive a stronger collision and further explore flux pileup in the context of the strongly-driven interaction of magnetic fields.

  4. First experiments probing the collision of parallel magnetic fields using laser-produced plasmas

    SciTech Connect

    Rosenberg, M. J. Li, C. K.; Séguin, F. H.; Frenje, J. A.; Petrasso, R. D.; Fox, W.; Igumenshchev, I.; Stoeckl, C.; Glebov, V.; Town, R. P. J.

    2015-04-15

    Novel experiments to study the strongly-driven collision of parallel magnetic fields in β ∼ 10, laser-produced plasmas have been conducted using monoenergetic proton radiography. These experiments were designed to probe the process of magnetic flux pileup, which has been identified in prior laser-plasma experiments as a key physical mechanism in the reconnection of anti-parallel magnetic fields when the reconnection inflow is dominated by strong plasma flows. In the present experiments using colliding plasmas carrying parallel magnetic fields, the magnetic flux is found to be conserved and slightly compressed in the collision region. Two-dimensional (2D) particle-in-cell simulations predict a stronger flux compression and amplification of the magnetic field strength, and this discrepancy is attributed to the three-dimensional (3D) collision geometry. Future experiments may drive a stronger collision and further explore flux pileup in the context of the strongly-driven interaction of magnetic fields.

  5. Integrated Active Magnetic Probe in Silicon-on-Insulator Complementary Metal-Oxide-Semiconductor Technology

    NASA Astrophysics Data System (ADS)

    Aoyama, Satoshi; Kawahito, Shoji; Yamaguchi, Masahiro

    2006-09-01

    A novel magnetic probe has been designed and fabricated by 0.15 μm five-metal (4M + thick metal) silicon-on-insulator (SOI) complementary metal-oxide-semiconductor (CMOS) technology to achieve both a high sensitivity and a high spatial resolution. A detecting coil having metal multilayers, a two-stage differential amplifier, a differential-to-single-ended converter, and an output buffer are integrated on a single chip. The probe is referred to as an active probe, and it has a feature to distinguish magnetic field from detected electromagnetic emissions by means of a two-turn differential coil structure and a circuit technique using a wideband differential-to-single-ended converter with a high common-mode rejection. Measurement results show the effectiveness of the active magnetic probe with the function of on-chip amplification and electric field suppression, as well as electrical switching with common-mode voltage (Vcom). Moreover, for the first time, a magnetic field distribution is visualized with an active probe.

  6. A magnetically driven reciprocating probe for tokamak scrape-off layer measurements.

    PubMed

    Gunn, J P; Pascal, J-Y

    2011-12-01

    A new in situ reciprocating probe system has been developed to provide scrape-off layer measurements in the Tore Supra tokamak. The probe motion is provided by the rotation of an energized coil in the tokamak magnetic field. Simple analytic approximations to the exact numerical model were used to identify the important parameters that govern the dynamics of the system, and optimize the coil geometry, the electrical circuit, and the stiffness of the retaining spring. The linear speed of the probe is directly proportional to the current induced by the coil's rotation; its integral gives the coil position, providing a means to implement real-time feedback control of the probe motion. Two probes were recently mounted on a movable outboard antenna protection limiter in Tore Supra and provided automatic measurements during the 2011 experimental campaign.

  7. Magnetically Actuated Propellant Orientation Experiment, Controlling Fluid Motion With Magnetic Fields in a Low-Gravity Environment

    NASA Technical Reports Server (NTRS)

    Martin, J. J.; Holt, J. B.

    2000-01-01

    This report details the results of a series of fluid motion experiments to investigate the use of magnets to orient fluids in a low-gravity environment. The fluid of interest for this project was liquid oxygen (LO2) since it exhibits a paramagnetic behavior (is attracted to magnetic fields). However, due to safety and handling concerns, a water-based ferromagnetic mixture (produced by Ferrofluidics Corporation) was selected to simplify procedures. Three ferromagnetic fluid mixture strengths and a nonmagnetic water baseline were tested using three different initial fluid positions with respect to the magnet. Experiment accelerometer data were used with a modified computational fluid dynamics code termed CFX-4 (by AEA Technologies) to predict fluid motion. These predictions compared favorably with experiment video data, verifying the code's ability to predict fluid motion with and without magnetic influences. Additional predictions were generated for LO2 with the same test conditions and geometries used in the testing. Test hardware consisted of a cylindrical Plexiglas tank (6-in. bore with 10-in. length), a 6,000-G rare Earth magnet (10-in. ring), three-axis accelerometer package, and a video recorder system. All tests were conducted aboard the NASA Reduced-Gravity Workshop, a KC-135A aircraft.

  8. Development, fabrication and testing of a magnetically connected plastic vacuum probe surface sampler

    NASA Technical Reports Server (NTRS)

    Phillips, G. B.; Pace, V. A., Jr.

    1972-01-01

    The sampler utilizes permanent magnets and soft metal pole pieces to connect the cone/filter assembly to the sampling head and vacuum supply. The cone/filter assembly is packaged in a plastic container and presterilized so that the need for any human contact during the sampling procedure is completely eliminated. Microbiological tests have demonstrated that the sampling efficiency is not affected by the magnetic coupling apparatus and that the probe appears to function as efficiently as the conventional plastic and Sandia vacuum probes.

  9. A versatile rotary-stage high frequency probe station for studying magnetic films and devices

    SciTech Connect

    He, Shikun; Meng, Zhaoliang; Huang, Lisen; Yap, Lee Koon; Zhou, Tiejun; Panagopoulos, Christos

    2016-07-15

    We present a rotary-stage microwave probe station suitable for magnetic films and spintronic devices. Two stages, one for field rotation from parallel to perpendicular to the sample plane (out-of-plane) and the other intended for field rotation within the sample plane (in-plane) have been designed. The sample probes and micro-positioners are rotated simultaneously with the stages, which allows the field orientation to cover θ from 0{sup ∘} to 90{sup ∘} and φ from 0{sup ∘} to 360{sup ∘}. θ and φ being the angle between the direction of current flow and field in a out-of-plane and an in-plane rotation, respectively. The operation frequency is up to 40 GHz and the magnetic field up to 1 T. The sample holder vision system and probe assembly are compactly designed for the probes to land on a wafer with diameter up to 3 cm. Using homemade multi-pin probes and commercially available high frequency probes, several applications including 4-probe DC measurements, the determination of domain wall velocity, and spin transfer torque ferromagnetic resonance are demonstrated.

  10. Muscle Motion Solenoid Actuator

    NASA Astrophysics Data System (ADS)

    Obata, Shuji

    It is one of our dreams to mechanically recover the lost body for damaged humans. Realistic humanoid robots composed of such machines require muscle motion actuators controlled by all pulling actions. Particularly, antagonistic pairs of bi-articular muscles are very important in animal's motions. A system of actuators is proposed using the electromagnetic force of the solenoids with the abilities of the stroke length over 10 cm and the strength about 20 N, which are needed to move the real human arm. The devised actuators are based on developments of recent modern electro-magnetic materials, where old time materials can not give such possibility. Composite actuators are controlled by a high ability computer and software making genuine motions.

  11. Magnetic field actuated manipulation and transfer of oil droplets on a stable underwater superoleophobic surface.

    PubMed

    Feng, Haifeng; Xu, Xun; Hao, Weichang; Du, Yi; Tian, Dongliang; Jiang, Lei

    2016-06-28

    The transport of fluids at functional interfaces, driven by the external stimuli, is well established. The lossless transport of oil-based fluids under water remains a challenge, however, due to their high stickiness towards the surface. Here, a superhydrophilic and underwater superoleophobic tri-phase water/oil/solid nanoarray surface has been designed and prepared. The unique tri-phase surface exhibits underwater superoleophobic properties with an extremely low stickiness towards oil-based fluids. The magnetic-field-driven manipulation and transport of oil-based magnetic fluids are demonstrated under water, which opens up a new pathway to design flexible and smart devices for the control and transfer of liquid droplets by using tri-phase systems.

  12. Self-Assembled DNA Structures for Molecular Force Measurement: A Magnetically Actuated Approach

    NASA Astrophysics Data System (ADS)

    Armstrong, M.; Lauback, S.; Miller, C.; Peace, C.; Castro, C.; Sooryakumar, R.

    2015-03-01

    Understanding molecular forces is important to comprehend many of the underlying properties of molecular machines and biological processes. The relevant forces in these cases often lie in the picoNewton range, and thus experiments on individual biomolecules must integrate techniques capable of measuring such forces. A mechanical system to measure molecular forces associated with interacting DNA strands is being developed by using self-assembled DNA nanostructures and super-paramagnetic beads. The DNA nanostructure consists of single-stranded DNA molecules which can be folded into a precise compact geometry using hundreds of short oligonucleotides, i.e., staples, via programmed molecular self-assembly. These nanostructures can be polymerized into micron-scale filaments. By functionalizing the filament ends with bispecific conjugate staples, the structure can be attached to a surface as well as labeled with magnetic beads in order to apply a force on the system. External magnetic fields provide the means to maneuver and manipulate the magnetically labeled DNA structures. Preliminary findings associated with the DNA constructs and their manipulation lay the groundwork to establish real-time control of DNA nanodevices with micromanipulation.

  13. Cellular bias on the microscale: probing the effects of digital microfluidic actuation on mammalian cell health, fitness and phenotype.

    PubMed

    Au, Sam H; Fobel, Ryan; Desai, Salil P; Voldman, Joel; Wheeler, Aaron R

    2013-08-01

    The potential benefits of using new technologies such as microfluidics for life science applications are exciting, but it is critical to understand and document potential biases imposed by these technologies on the observed results. Here, we report the first study of genome-level effects on cells manipulated by digital microfluidics. These effects were evaluated using a broad suite of tools: cell-based stress sensors for heat shock activation, single-cell COMET assays to probe changes in DNA integrity, and DNA microarrays and qPCR to evaluate changes in genetic expression. The results lead to two key observations. First, most DMF operating conditions tested, including those that are commonly used in the literature, result in negligible cell-stress or genome-level effects. Second, for DMF devices operated at high driving frequency (18 kHz) and with large driving electrodes (10 mm × 10 mm), there are significant damage to DNA integrity and differential genomic regulation. We hypothesize that these effects are caused by droplet heating. We recommend that for DMF applications involving mammalian cells that driving frequencies be kept low (≤ 10 kHz) and electrode sizes be kept small (≤ 5 mm) to avoid detrimental effects.

  14. Probing nonlinear magnetization dynamics in Fe/MgO(001) film by all optical pump-probe technique

    SciTech Connect

    He, Wei; Hu, Bo; Zhang, Xiang-Qun; Cheng, Zhao-Hua; Zhan, Qing-Feng

    2014-04-07

    An all-optical pump-probe technique has been employed to investigate the nonlinear magnetization dynamics of a 10 nm Fe/MgO(001) thin film in time domain. The magnetization precession was excited by pump-laser pulses and modulated by laser fluence variations. With increasing the laser fluence up to 7.1 mJ/cm{sup 2}, in addition to the uniform precession mode, a second harmonic signal was detected. The time evolution of the second harmonic signal was obtained in time-frequency domain. Based on the Landau-Lifshitz-Gilbert equation, the numerical simulation was performed to reproduce the observed the frequency doubling behaviors in Fe/MgO(001) film.

  15. Directly probing the effect of strain on magnetic exchange interactions

    NASA Astrophysics Data System (ADS)

    Dorr, Kathrin

    2012-02-01

    Thin films of transition metal oxides of the perovskite type ABO3 (B = 3d or 4d metal) have revealed abundant examples for strain-driven changes of magnetic ordering. One most popular is the strain-induced ferromagnetic ferroelectric state of otherwise antiferromagnetic paraelectric EuTiO3. Another promising example is the strain control of orbital occupation and magnetic coupling at oxide interfaces of SrRuO3 with manganites. In spite of strong efforts, the theoretical treatment of magnetic exchange in complex oxides has remained a challenge, and experiments continue to show unpredicted / unexplained large effects of the epitaxial strains in films. In order to provide meaningful experimental data on strain dependences, epitaxial thin films should be grown in various coherent strain states on different substrates without changing anything but the strain. This is inherently difficult: possible problems may arise from a strain-dependent oxidation level or microstructure. As a complementary approach, the in-plane strain of epitaxial oxide films can be controlled reversibly using a piezoelectric substrate, even though the accessible reversible strain of 0.1 -- 0.2% is an order of magnitude smaller. In my talk, I will address reversible-strain studies on La0.7Sr0.3MnO3, La1-xSrxCoO3 (x = 0, 0.2, 0.3) und SrRuO3 films, showing the strain response of the magnetic Curie temperature, the magnetization and the electrical resistance and discussing the current understanding of the strain effects on magnetic ordering. In La0.8Sr0.2CoO3, a strain-driven phase transition between ferromagnetic and spin-glass-like could be established by combining the piezoelectric substrate with a tuned buffer system providing varied as-grown strain states. In SrRuO3, a tetragonal tensile strain state shows a suppression of the ordered magnetic moment. Lattice parameters and symmetries of the films were determined by x-ray diffraction. It is noted that the atomic displacements (bond lengths and

  16. Magnification bias as a novel probe for primordial magnetic fields

    SciTech Connect

    Camera, S.; Fedeli, C.; Moscardini, L. E-mail: cosimo.fedeli@oabo.inaf.it

    2014-03-01

    In this paper we investigate magnetic fields generated in the early Universe. These fields are important candidates at explaining the origin of astrophysical magnetism observed in galaxies and galaxy clusters, whose genesis is still by and large unclear. Compared to the standard inflationary power spectrum, intermediate to small scales would experience further substantial matter clustering, were a cosmological magnetic field present prior to recombination. As a consequence, the bias and redshift distribution of galaxies would also be modified. Hitherto, primordial magnetic fields (PMFs) have been tested and constrained with a number of cosmological observables, e.g. the cosmic microwave background radiation, galaxy clustering and, more recently, weak gravitational lensing. Here, we explore the constraining potential of the density fluctuation bias induced by gravitational lensing magnification onto the galaxy-galaxy angular power spectrum. Such an effect is known as magnification bias. Compared to the usual galaxy clustering approach, magnification bias helps in lifting the pathological degeneracy present amongst power spectrum normalisation and galaxy bias. This is because magnification bias cross-correlates galaxy number density fluctuations of nearby objects with weak lensing distortions of high-redshift sources. Thus, it takes advantage of the gravitational deflection of light, which is insensitive to galaxy bias but powerful in constraining the density fluctuation amplitude. To scrutinise the potentiality of this method, we adopt a deep and wide-field spectroscopic galaxy survey. We show that magnification bias does contain important information on primordial magnetism, which will be useful in combination with galaxy clustering and shear. We find we shall be able to rule out at 95.4% CL amplitudes of PMFs larger than 5 × 10{sup −4} nG for values of the PMF power spectral index n{sub B} ∼ 0.

  17. THE MAGNETIC FIELD IN TAURUS PROBED BY INFRARED POLARIZATION

    SciTech Connect

    Chapman, Nicholas L.; Goldsmith, Paul F.; Pineda, Jorge L.; Li Di; Clemens, D. P.; Krco, Marko

    2011-11-01

    We present maps of the plane-of-sky magnetic field within two regions of the Taurus molecular cloud: one in the dense core L1495/B213 filament and the other in a diffuse region to the west. The field is measured from the polarization of background starlight seen through the cloud. In total, we measured 287 high-quality near-infrared polarization vectors in these regions. In L1495/B213, the percent polarization increases with column density up to A{sub V} {approx} 9 mag, the limits of our data. The radiative torques model for grain alignment can explain this behavior, but models that invoke turbulence are inconsistent with the data. We also combine our data with published optical and near-infrared polarization measurements in Taurus. Using this large sample, we estimate the strength of the plane-of-sky component of the magnetic field in nine subregions. This estimation is done with two different techniques that use the observed dispersion in polarization angles. Our values range from 5 to 82 {mu}G and tend to be higher in denser regions. In all subregions, the critical index of the mass-to-magnetic flux ratio is sub-unity, implying that Taurus is magnetically supported on large scales ({approx}2 pc). Within the region observed, the B213 filament takes a sharp turn to the north and the direction of the magnetic field also takes a sharp turn, switching from being perpendicular to the filament to becoming parallel. This behavior can be understood if we are observing the rim of a bubble. We argue that it has resulted from a supernova remnant associated with a recently discovered nearby gamma-ray pulsar.

  18. Solar energetic particles as probes of the structures of magnetic clouds

    NASA Technical Reports Server (NTRS)

    Kahler, S. W.; Reames, D. V.

    1990-01-01

    Two possible closed magnetic topologies are considered for clouds: an elongated bottle with field lines rooted at both ends in the sun and a magnetic bubble or plasmoid consisting of closed field lines. Solar energetic particles (SEPs) are used as probes of the cloud topologies. The rapid access of SEPs to clouds in many events indicates that the cloud field lines extend back to the sun.

  19. Size effects on magnetic actuation in Ni-Mn-Ga shape-memory alloys.

    PubMed

    Dunand, David C; Müllner, Peter

    2011-01-11

    The off-stoichiometric Ni(2)MnGa Heusler alloy is a magnetic shape-memory alloy capable of reversible magnetic-field-induced strains (MFIS). These are generated by twin boundaries moving under the influence of an internal stress produced by a magnetic field through the magnetocrystalline anisotropy. While MFIS are very large (up to 10%) for monocrystalline Ni-Mn-Ga, they are near zero (<0.01%) in fine-grained polycrystals due to incompatibilities during twinning of neighboring grains and the resulting internal geometrical constraints. By growing the grains and/or shrinking the sample, the grain size becomes comparable to one or more characteristic sample sizes (film thickness, wire or strut diameter, ribbon width, particle diameter, etc), and the grains become surrounded by free space. This reduces the incompatibilities between neighboring grains and can favor twinning and thus increase the MFIS. This approach was validated recently with very large MFIS (0.2-8%) measured in Ni-Mn-Ga fibers and foams with bamboo grains with dimensions similar to the fiber or strut diameters and in thin plates where grain diameters are comparable to plate thickness. Here, we review processing, micro- and macrostructure, and magneto-mechanical properties of (i) Ni-Mn-Ga powders, fibers, ribbons and films with one or more small dimension, which are amenable to the growth of bamboo grains leading to large MFIS, and (ii) "constructs" from these structural elements (e.g., mats, laminates, textiles, foams and composites). Various strategies are proposed to accentuate this geometric effect which enables large MFIS in polycrystalline Ni-Mn-Ga by matching grain and sample sizes.

  20. Probing correlations of early magnetic fields using μ-distortion

    SciTech Connect

    Ganc, Jonathan; Sloth, Martin S. E-mail: sloth@cp3.dias.sdu.dk

    2014-08-01

    The damping of a non-uniform magnetic field between the redshifts of about 10{sup 4} and 10{sup 6} injects energy into the photon-baryon plasma and causes the CMB to deviate from a perfect blackbody spectrum, producing a so-called μ-distortion. We can calculate the correlation (μ T) of this distortion with the temperature anisotropy T of the CMB to search for a correlation ( B{sup 2}ζ) between the magnetic field B and the curvature perturbation ζ; knowing the ( B{sup 2}ζ) correlation would help us distinguish between different models of magnetogenesis. Since the perturbations which produce the μ-distortion will be much smaller scale than the relevant density perturbations, the observation of this correlation is sensitive to the squeezed limit of ( B{sup 2}ζ), which is naturally parameterized by b{sub NL} (a parameter defined analogously to f{sub NL}). We find that a PIXIE-like CMB experiments has a signal to noise S/N≈ 1.0 × b{sub NL} ( B-tilde {sub μ}/10nG){sup 2}, where B-tilde {sub μ} is the magnetic field's strength on μ-distortion scales normalized to today's redshift; thus, a 10 nG field would be detectable with b{sub NL}=O(1). However, if the field is of inflationary origin, we generically expect it to be accompanied by a curvature bispectrum (ζ{sup 3}) induced by the magnetic field. For sufficiently small magnetic fields, the signal ( B{sup 2} ζ) will dominate, but for B-tilde {sub μ}∼> 1 nG, one would have to consider the specifics of the inflationary magnetogenesis model. We also discuss the potential post-magnetogenesis sources of a ( B{sup 2}ζ) correlation and explain why there will be no contribution from the evolution of the magnetic field in response to the curvature perturbation.

  1. Matched dipole probe for magnetized low electron density laboratory plasma diagnostics

    SciTech Connect

    Rafalskyi, Dmytro; Aanesland, Ane

    2015-07-15

    In this paper, a diagnostic method for magnetized and unmagnetized laboratory plasma is proposed, based on impedance measurements of a short matched dipole. The range of the measured electron densities is limited to low density plasmas (10{sup 12}–10{sup 15 }m{sup −3}), where other diagnostic methods have strong limitations on the magnetic field strength and topology, plasma dimensions, and boundary conditions. The method is designed for use in both large- and small-dimension plasma (<10 cm) without or with strong non-homogeneous magnetic field, which can be undefined within the probe size. The design of a matched dipole probe allows to suppress the sheath resonance effects and to reach high sensitivity at relatively small probe dimensions. Validation experiments are conducted in both magnetized (B ∼ 170 G) and unmagnetized (B = 0) low density (7 × 10{sup 12 }m{sup −3}–7 × 10{sup 13 }m{sup −3}) low pressure (1 mTorr) 10 cm scale plasmas. The experimentally measured data show very good agreement with an analytical theory both for a non-magnetized and a magnetized case. The electron density measured by the matched dipole and Langmuir probes in the range of 7 × 10{sup 12 }m{sup −3}–7 × 10{sup 13 }m{sup −3} show less than 30% difference. An experimentally measured tolerance/uncertainty of the dipole probe method is estimated to ±1% for plasma densities above 2 × 10{sup 13 }m{sup −3}. A spatial resolution is estimated from the experiments to be about 3d, where d is the dipole diameter. The diagnostic method is also validated by comparing the measured plasma impedance curves with results of analytical modelling.

  2. Probing the spinor nature of electronic states in nanosize non-collinear magnets

    PubMed Central

    Fischer, Jeison A.; Sandratskii, Leonid M.; Phark, Soo-Hyon; Ouazi, Safia; Pasa, André A.; Sander, Dirk; Parkin, Stuart S. P.

    2016-01-01

    Non-collinear magnetization textures provide a route to novel device concepts in spintronics. These applications require laterally confined non-collinear magnets (NCM). A crucial aspect for potential applications is how the spatial proximity between the NCM and vacuum or another material impacts the magnetization texture on the nanoscale. We focus on a prototypical exchange-driven NCM given by the helical spin order of bilayer Fe on Cu(111). Spin-polarized scanning tunnelling spectroscopy and density functional theory reveal a nanosize- and proximity-driven modification of the electronic and magnetic structure of the NCM in interfacial contact with a ferromagnet or with vacuum. An intriguing non-collinearity between the local magnetization in the sample and the electronic magnetization probed above its surface results. It is a direct consequence of the spinor nature of electronic states in NCM. Our findings provide a possible route for advanced control of nanoscale spin textures by confinement. PMID:27721384

  3. Aharonov-Bohm effect as a probe of interaction between magnetic impurities.

    PubMed

    Galitski, Victor M; Vavilov, Maxim G; Glazman, Leonid I

    2005-03-11

    We study the effects of the RKKY interaction between magnetic impurities on the mesoscopic conductance fluctuations of a metal ring with dilute magnetic impurities. At sufficiently low temperatures and strong magnetic fields, the loss of electron coherence occurs mainly due to the scattering off rare pairs of strongly coupled magnetic impurities. We establish a relation between the dephasing rate and the distribution function of the exchange interaction within such pairs. In the case of the RKKY exchange interaction, this rate exhibits 1/B(2) behavior in strong magnetic fields. We demonstrate that the Aharonov-Bohm conductance oscillations may be used as a probe of the distribution function of the exchange interaction between magnetic impurities in metals.

  4. Magnetic microparticle-based multiplexed DNA detection with biobarcoded quantum dot probes.

    PubMed

    Xiang, Dong-shan; Zeng, Guo-ping; He, Zhi-ke

    2011-07-15

    We have developed a new analytical method to detect multiple DNA simultaneously based on the biobarcoded CdSe/ZnS quantum dot (QD) and magnetic microparticle (MMP). It was demonstrated by using oligonucleotide sequences of 64 bases associated with human papillomavirus 16 and 18 L1 genes (HPV-16 and HPV-18) as model systems. This analytical system involves three types of probes, a MMP probe and two streptavidin-modified QD probes. The MMPs are functionalized with HPV-16 and HPV-18 captures DNA to form MMP probes. The QDs are conjugated with HPV-16 or HPV-18 probe DNA along with FAM- or Rox-labeled random DNA to form HPV-16 and HPV-18 QD probes, respectively. A one-step hybridization reaction was performed by mixing the MMP probes, HPV-16 and HPV-18 target DNA (T-16 and T-18), HPV-16 and HPV-18 QD probes. Afterwards, the hybrid-conjugated microparticles were separated by a magnet and heated to remove the MMPs. Finally, the detections of T-16 and T-18 were done by measuring fluorescence signals of FAM and Rox, respectively. Under the optimum conditions, the fluorescence intensity exhibited a good linear dependence on target DNA concentration in the range from 8 × 10⁻¹¹ to 8 × 10⁻⁹ M. The detection limit of T-16 is up to 7 × 10⁻¹¹ M (3σ), and that of T-18 is 6 × 10⁻¹¹ M. Compared with other biobarcode assay methods, the proposed method that QDs were used as the solid support has some advantages including shorter preparation time of QD probes, faster binding kinetics and shorter analytical time. Besides, it is simple and accurate.

  5. Magnetic Field-Induced Phase Transformation in Magnetic Shape Memory Alloys with High Actuation Stress and Work Output

    DTIC Science & Technology

    2010-05-03

    for all specimens were determined by SQUID magnetometer. Final Progress Report on ARO Project #50718-MS...step heat treatment by SQUID magnetometer. 160 140 120 100 80 60 40 20 0 M ag ne tiz at io n, e m u/ g 40036032028024020016012080400 Temperature, K...0.05 T 1 T 3 T 5 T 7 T NiMnCoIn [001](100) SQUID M-T curves (a) Figure 21. a) Change of magnetization with temperature cycling under different

  6. Probe measurements of the three-dimensional magnetic field structure in a rotating magnetic field sustained field-reversed configuration

    SciTech Connect

    Velas, K. M.; Milroy, R. D.

    2014-01-15

    A translatable three-axis probe was constructed and installed on the translation, confinement, and sustainment upgrade (TCSU) experiment. With ninety windings, the probe can simultaneously measure B{sub r}, B{sub θ}, and B{sub z} at 30 radial positions, and can be placed at any desired axial position within the field reversed configuration (FRC) confinement chamber. Positioning the probe at multiple axial positions and taking multiple repeatable shots allows for a full r-z map of the magnetic field. Measurements were made for odd-parity rotating magnetic field (RMF) antennas and even-parity RMF. The steady state data from applying a 10 kHz low pass filter used in conjunction with data at the RMF frequency yields a map of the full 3D rotating field structure. Comparisons will be made to the 3D magnetic structure predicted by NIMROD simulations, with parameters adjusted to match that of the TCSU experiments. The probe provides sufficient data to utilize a Maxwell stress tensor approach to directly measure the torque applied to the FRC's electrons, which combined with a resistive torque model, yields an estimate of the average FRC resistivity.

  7. Probe measurements of the three-dimensional magnetic field structure in a rotating magnetic field sustained field-reversed configuration

    NASA Astrophysics Data System (ADS)

    Velas, K. M.; Milroy, R. D.

    2014-01-01

    A translatable three-axis probe was constructed and installed on the translation, confinement, and sustainment upgrade (TCSU) experiment. With ninety windings, the probe can simultaneously measure Br, Bθ, and Bz at 30 radial positions, and can be placed at any desired axial position within the field reversed configuration (FRC) confinement chamber. Positioning the probe at multiple axial positions and taking multiple repeatable shots allows for a full r-z map of the magnetic field. Measurements were made for odd-parity rotating magnetic field (RMF) antennas and even-parity RMF. The steady state data from applying a 10 kHz low pass filter used in conjunction with data at the RMF frequency yields a map of the full 3D rotating field structure. Comparisons will be made to the 3D magnetic structure predicted by NIMROD simulations, with parameters adjusted to match that of the TCSU experiments. The probe provides sufficient data to utilize a Maxwell stress tensor approach to directly measure the torque applied to the FRC's electrons, which combined with a resistive torque model, yields an estimate of the average FRC resistivity.

  8. An analysis and optimization of elliptical RF probes used in magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Forbes, Lawrence K.; Crozier, Stuart; Doddrell, David M.

    1996-09-01

    In magnetic resonance imaging of the entire body, it is often desirable to use an elliptical RF probe, rather than a circular one. As an ellipse more closely conforms to the anatomical cross section of the human thorax and head, better filling factors and therefore improved signal-to-noise ratios may be achieved by the use of elliptical RF coils. The probe is usually of bird-cage type, but the rungs are of finite width due to the high-frequency signals involved. This paper presents a method for computing the magnetic fields produced inside elliptical probes, and the current distributions on the rungs. A slotted shield is assumed to surround the probe, and its influence on field homogeneity is studied. In particular, the currents in a 16-runged unshielded elliptical coil of practical interest were determined optimally in one case, using simulated annealing to optimize the homogeneity of the magnetic field within the probe. The effects of a segmented shield of both elliptical and circular cross section on this coil are discussed, and the results are confirmed by experiment.

  9. Probing Solar Eruption by Tracking Magnetic Cavities and Filaments

    NASA Astrophysics Data System (ADS)

    Sterling, A. C.; Johnson, J. R.; Moore, R. L.; Gibson, S. E.

    2015-12-01

    A solar eruption is a tremendous explosion on the Sun that happens when energy stored in twisted (or distorted) magnetic fields is suddenly released. When this field is viewed along the axis of the twist in projection at the limb, e.g. in EUV or white-light coronal images, the outer portions of the pre-eruption magnetic structure sometimes appears as a region of weaker emission, called a "coronal cavity," surrounded by a brighter envelope. Often a chromospheric filament resides near the base of the cavity and parallel to the cavity's central axis. Typically, both the cavity and filament move outward from the Sun at the start of an eruption of the magnetic field in which the cavity and filament reside. Studying properties the cavities and filaments just prior to and during eruption can help constrain models that attempt to explain why and how the eruptions occur. In this study, we examined six different at-limb solar eruptions using images from the Extreme Ultraviolet Imaging Telescope (EIT) aboard the Solar and Heliospheric Observatory (SOHO). For four of these eruptions we observed both cavities and filaments, while for the remaining two eruptions, one had only a cavity and the other only a filament visible in EIT images. All six eruptions were in comparatively-quiet solar regions, with one in the neighborhood of the polar crown. We measured the height and velocities of the cavities and filaments just prior to and during the start of their fast-eruption onsets. Our results support that the filament and cavity are integral parts of a single large-scale erupting magnetic-field system. We examined whether the eruption-onset heights were correlated with the expected magnetic field strengths of the eruption-source regions, but no clear correlation was found. We discuss possible reasons for this lack of correlation, and we also discuss future research directions. The research performed was supported by the National Science Foundation under Grant No. AGS-1460767; J

  10. Fabrication and use of a nanoscale Hall probe for measurements of the magnetic field induced by MFM tips.

    PubMed

    Matveev, Victor N; Levashov, Vladimir I; Volkov, Vladimir T; Kononenko, Oleg V; Chernyh, Anatoly V; Knjazev, Maxim A; Tulin, Vyacheslav A

    2008-11-26

    Extraordinary Hall effect probes with 160 nm × 160 nm working area were fabricated using photo- and electron-beam lithographic procedures with the aim of direct measurements of MFM cantilever tip magnetic properties. The magnetic field sensitivity of the probes was 35 Ω T(-1). Magnetic induction of the MFM cantilever tips coated by Co and SmCo films was measured with the probes. It was shown that the resolution of the probes was of the order of 10 nm.

  11. Internal magnetic field measurements on the Helicity Injected Tokamak (HIT) using the Transient Internal Probe (TIP)

    SciTech Connect

    Galambos, J.P.; Bohnet, M.A.; Jarboe, T.R.; Mattick, A.T.

    1996-12-31

    The Transient Internal Probe (TIP) is a novel diagnostic designed to measure internal magnetic fields in hot plasmas. The diagnostic involves shooting a magneto-optic probe through the plasma at high velocities (greater than 2 km/s) using a two stage light gas gun. Local fields are obtained by illuminating the probe with an argon ion laser and measuring the amount of Faraday rotation in the laser light reflected from the moving probe. Currently, internal magnetic profile measurements are being conducted on the Helicity Injected tokamak (HIT). HIT is a low aspect ratio (A = 1.5) tokamak designed to investigate steady state current drive using coaxial helicity injection. Operating parameters are T{sub e} {approx} 100, n{sub e} {approx} 5 {times} 10{sup 13} cm{sup {minus}3} and I{sub p} = 250 kA. Internal magnetic field profile data will be presented. The TIP diagnostic has a spatial resolution of 1 cm and 20 gauss magnetic field resolution. System frequency response is 10 MHz.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-03-02

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

  15. X-Ray Detected Magnetic Resonance: A Unique Probe of the Precession Dynamics of Orbital Magnetization Components

    PubMed Central

    Goulon, Jośe; Rogalev, Andrei; Goujon, Gérard; Wilhelm, Fabrice; Ben Youssef, Jamal; Gros, Claude; Barbe, Jean-Michel; Guilard, Roger

    2011-01-01

    X-ray Detected Magnetic Resonance (XDMR) is a novel spectroscopy in which X-ray Magnetic Circular Dichroism (XMCD) is used to probe the resonant precession of local magnetization components in a strong microwave pump field. We review the conceptual bases of XDMR and recast them in the general framework of the linear and nonlinear theories of ferromagnetic resonance (FMR). Emphasis is laid on the information content of XDMR spectra which offer a unique opportunity to disentangle the precession dynamics of spin and orbital magnetization components at given absorbing sites. For the sake of illustration, we focus on selected examples in which marked differences were found between FMR and XDMR spectra simultaneously recorded on ferrimagnetically ordered iron garnets. With pumping capabilities extended up to sub-THz frequencies, high-field XDMR should allow us to probe the precession of orbital magnetization components in paramagnetic organometallic complexes with large zero-field splitting. Even more challenging, we suggest that XDMR spectra might be recorded on selected antiferromagnetic crystals for which orbital magnetism is most often ignored in the absence of any supporting experimental evidence. PMID:22272105

  16. Low magnetic field dynamic nuclear polarization using a single-coil two-channel probe

    SciTech Connect

    TonThat, D.M.; Augustine, M.P.; Pines, A.; Clarke, J. |

    1997-03-01

    We describe the design and construction of a single-coil, two-channel probe for the detection of low-field magnetic resonance using dynamic nuclear polarization (DNP). The high-frequency channel of the probe, which is used to saturate the electron spins, is tuned to the electron Larmor frequency, 75 MHz at 2.7 mT, and matched to 50 {Omega}. Low-field, {sup 1}H nuclear magnetic resonance (NMR) is detected through the second, low-frequency channel at frequencies {lt}1 MHz. The performance of the probe was tested by measuring the DNP of protons in a manganese (II) chloride solution at 2.7 mT. At the proton NMR frequency of 120 kHz, the signal amplitude was enhanced over the value without DNP by a factor of about 200. {copyright} {ital 1997 American Institute of Physics.}

  17. Low magnetic field dynamic nuclear polarization using a single-coil two-channel probe

    NASA Astrophysics Data System (ADS)

    TonThat, Dinh M.; Augustine, Matthew P.; Pines, Alexander; Clarke, John

    1997-03-01

    We describe the design and construction of a single-coil, two-channel probe for the detection of low-field magnetic resonance using dynamic nuclear polarization (DNP). The high-frequency channel of the probe, which is used to saturate the electron spins, is tuned to the electron Larmor frequency, 75 MHz at 2.7 mT, and matched to 50 Ω. Low-field, 1H nuclear magnetic resonance (NMR) is detected through the second, low-frequency channel at frequencies <1 MHz. The performance of the probe was tested by measuring the DNP of protons in a manganese (II) chloride solution at 2.7 mT. At the proton NMR frequency of 120 kHz, the signal amplitude was enhanced over the value without DNP by a factor of about 200.

  18. Porosity-dependent vibration analysis of piezo-magnetically actuated heterogeneous nanobeams

    NASA Astrophysics Data System (ADS)

    Ebrahimi, Farzad; Barati, Mohammad Reza

    2017-09-01

    In this article, the size-dependent and porosity-dependent vibrational behavior of magneto-electro-elastic functionally graded (MEE-FG) nanoscale beams on two-parameter elastic substrate is presented via a third-order shear deformation beam model. Porosity-dependent material coefficients of the nanobeam are compositionally graded throughout the thickness according to a modified power-law model. Incorporation of small size effect is carried out based on Eringen's nonlocal elasticity theory. Through Hamilton's principle, derivation of nonlocal governing equations is performed. After analytically solving these equations, the influences of porosity, elastic foundation, magnetic potential, applied voltage, scale coefficient, material gradation and slenderness ratio on the frequencies of the porous MEE-FG nanobeams are examined.

  19. Chirality-driven orbital magnetic moments as a new probe for topological magnetic structures

    PubMed Central

    dos Santos Dias, Manuel; Bouaziz, Juba; Bouhassoune, Mohammed; Blügel, Stefan; Lounis, Samir

    2016-01-01

    When electrons are driven through unconventional magnetic structures, such as skyrmions, they experience emergent electromagnetic fields that originate several Hall effects. Independently, ground-state emergent magnetic fields can also lead to orbital magnetism, even without the spin–orbit interaction. The close parallel between the geometric theories of the Hall effects and of the orbital magnetization raises the question: does a skyrmion display topological orbital magnetism? Here we first address the smallest systems with nonvanishing emergent magnetic field, trimers, characterizing the orbital magnetic properties from first-principles. Armed with this understanding, we study the orbital magnetism of skyrmions and demonstrate that the contribution driven by the emergent magnetic field is topological. This means that the topological contribution to the orbital moment does not change under continuous deformations of the magnetic structure. Furthermore, we use it to propose a new experimental protocol for the identification of topological magnetic structures, by soft X-ray spectroscopy. PMID:27995909

  20. Magnetism of gold nanorods probed using electron spin resonance

    NASA Astrophysics Data System (ADS)

    Inagaki, Y.; Yonemura, H.; Sakai, N.; Makihara, Y.; Kawae, T.; Yamada, S.

    2016-08-01

    Electron spin resonance (ESR) spectroscopy has been performed for gold nanorods (AuNRs) of four different sizes covered with a diamagnetic stabilizing component, cetyltrimethylammonium bromide. ESR signals were detected in AuNRs except the largest one. Two smallest AuNRs showed an abrupt change in the temperature dependence of resonance field and line width at around 60 K, indicating ferromagnetic phase transition. In medium-size AuNRs, the resonance with a large shift was observed below 100 K. The resonance field shifts at the lowest temperature exhibit systematic variation with the system size, which is explained by considering magnetic anisotropy for the ferromagnetic resonance.

  1. Magnetism of gold nanorods probed using electron spin resonance

    SciTech Connect

    Inagaki, Y. Kawae, T.; Yonemura, H.; Yamada, S.; Sakai, N.; Makihara, Y.

    2016-08-15

    Electron spin resonance (ESR) spectroscopy has been performed for gold nanorods (AuNRs) of four different sizes covered with a diamagnetic stabilizing component, cetyltrimethylammonium bromide. ESR signals were detected in AuNRs except the largest one. Two smallest AuNRs showed an abrupt change in the temperature dependence of resonance field and line width at around 60 K, indicating ferromagnetic phase transition. In medium-size AuNRs, the resonance with a large shift was observed below 100 K. The resonance field shifts at the lowest temperature exhibit systematic variation with the system size, which is explained by considering magnetic anisotropy for the ferromagnetic resonance.

  2. Preparation of magnetic resonance probes using one-pot method for detection of hepatocellular carcinoma.

    PubMed

    Li, You-Wei; Chen, Zheng-Guang; Zhao, Zhou-She; Li, Hong-Li; Wang, Ji-Chen; Zhang, Zong-Ming

    2015-04-14

    To prepare the specific magnetic resonance (MR) probes for detection of hepatocellular carcinoma (HCC) using one-pot method. The carboxylated dextran-coated nanoparticles were conjugated with anti-α-fetoprotein (anti-AFP) or anti-glypican 3 (anti-GPC3) antibodies through 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS)-mediated reaction to synthesize the probes. The physical and chemical properties of the probes were determined by transmission electron microscopy (TEM) and dynamic light scattering, and the relaxivity was compared to uncombined ultrasmall superparamagnetic iron oxide nanoparticles (USPIONs) using a 1.5T clinical MR scanner. The binding efficiency of the antibodies to nanoparticles was measured with an ultraviolet-visible spectrophotometer. In addition, the probes were incubated with targetable cells in vitro. The superparamagnetic MR probes (anti-GPC3-USPION probe and anti-AFP-USPION probe) were synthesized using one-pot method. Their mean hydrodynamic diameter was 47 nm with a broader slight size distribution. The coupling efficiency of carboxylated dextran-coated ultrasmall superparamagnetic iron oxide (USPIO) with anti-GPC3 or anti-AFP antibody was 15.9% and 88.8%, respectively. Each of the USPIO nanoparticles may bind 3 GPC3 antibodies or 12 AFP antibodies. The statistical analysis showed no significance (P > 0.05) in shortening the T1 and T2 values when comparing the USPIO-AFP or USPIO-GPC3 to USPIO. Analysis of TEM images revealed that anti-GPC3-USPION probes and anti-AFP-USPION probes could specifically enter into the HepG2 cell by combining with the GPC3 receptors or AFP receptors, whereas the HepG2 cell sample incubated with USPIONs showed no or few nanoparticles in the cytoplasm. The synthesized probes using one-pot method can be used for in vitro experimental study and have potential clinical application in MR imaging for detection of hepatocellular carcinomas.

  3. Probing transmembrane mechanical coupling and cytomechanics using magnetic twisting cytometry

    NASA Technical Reports Server (NTRS)

    Wang, N.; Ingber, D. E.

    1995-01-01

    We recently developed a magnetic twisting cytometry technique that allows us to apply controlled mechanical stresses to specific cell surface receptors using ligand-coated ferromagnetic microbeads and to simultaneously measure the mechanical response in living cells. Using this technique, we have previously shown the following: (i) beta 1 integrin receptors mediate mechanical force transfer across the cell surface and to the cytoskeleton, whereas other transmembrane receptors (e.g., scavenger receptors) do not; (ii) cytoskeletal stiffness increases in direct proportion to the level of stress applied to integrins; and (iii) the slope of this linear stiffening response differs depending on the shape of the cell. We now show that different integrins (beta 1, alpha V beta 3, alpha V, alpha 5, alpha 2) and other transmembrane receptors (scavenger receptor, platelet endothelial cell adhesion molecule) differ in their ability to mediate force transfer across the cell surface. In addition, the linear stiffening behavior previously observed in endothelial cells was found to be shared by other cell types. Finally, we demonstrate that dynamic changes in cell shape that occur during both cell spreading and retraction are accompanied by coordinate changes in cytoskeletal stiffness. Taken together, these results suggest that the magnetic twisting cytometry technique may be a powerful and versatile tool for studies analyzing the molecular basis of transmembrane mechanical coupling to the cytoskeleton as well as dynamic relations between changes in cytoskeletal structure and alterations in cell form and function.

  4. Probing transmembrane mechanical coupling and cytomechanics using magnetic twisting cytometry

    NASA Technical Reports Server (NTRS)

    Wang, N.; Ingber, D. E.

    1995-01-01

    We recently developed a magnetic twisting cytometry technique that allows us to apply controlled mechanical stresses to specific cell surface receptors using ligand-coated ferromagnetic microbeads and to simultaneously measure the mechanical response in living cells. Using this technique, we have previously shown the following: (i) beta 1 integrin receptors mediate mechanical force transfer across the cell surface and to the cytoskeleton, whereas other transmembrane receptors (e.g., scavenger receptors) do not; (ii) cytoskeletal stiffness increases in direct proportion to the level of stress applied to integrins; and (iii) the slope of this linear stiffening response differs depending on the shape of the cell. We now show that different integrins (beta 1, alpha V beta 3, alpha V, alpha 5, alpha 2) and other transmembrane receptors (scavenger receptor, platelet endothelial cell adhesion molecule) differ in their ability to mediate force transfer across the cell surface. In addition, the linear stiffening behavior previously observed in endothelial cells was found to be shared by other cell types. Finally, we demonstrate that dynamic changes in cell shape that occur during both cell spreading and retraction are accompanied by coordinate changes in cytoskeletal stiffness. Taken together, these results suggest that the magnetic twisting cytometry technique may be a powerful and versatile tool for studies analyzing the molecular basis of transmembrane mechanical coupling to the cytoskeleton as well as dynamic relations between changes in cytoskeletal structure and alterations in cell form and function.

  5. Multifunctional magnetic-optical nanoparticle probes for simultaneous detection, separation, and thermal ablation of multiple pathogens.

    PubMed

    Wang, Chungang; Irudayaraj, Joseph

    2010-01-01

    Multifunctional nanoparticles possessing magnetization and near-infrared (NIR) absorption have warranted interest due to their significant applications in magnetic resonance imaging, diagnosis, bioseparation, target delivery, and NIR photothermal ablation. Herein, the site-selective assembly of magnetic nanoparticles onto the ends or ends and sides of gold nanorods with different aspect ratios (ARs) to create multifunctional nanorods decorated with varying numbers of magnetic particles is described for the first time. The resulting hybrid nanoparticles are designated as Fe(3)O(4)-Au(rod)-Fe(3)O(4) nanodumbbells and Fe(3)O(4)-Au(rod) necklacelike constructs with tunable optical and magnetic properties, respectively. These hybrid nanomaterials can be used for multiplex detection and separation because of their tunable magnetic and plasmonic functionality. More specifically, Fe(3)O(4)-Au(rod) necklacelike probes of different ARs are utilized for simultaneous optical detection based on their plasmon properties, magnetic separation, and photokilling of multiple pathogens from a single sample at one time. The combined functionalities of the synthesized probes will open up many exciting opportunities in dual imaging for targeted delivery and photothermal therapy.

  6. The fine magnetic image of a high TC SQUID probe microscope

    NASA Astrophysics Data System (ADS)

    Hayashi, Tadayuki; Itozaki, Hideo

    2005-01-01

    We have developed a high TC SQUID probe microscope. A high permeability probe was used as a flux guide to improve its spatial resolution. The SQUID head with the flux guide makes it possible to measure samples with high spatial resolution in air at room temperature. The end of the flux guide and the SQUID were in vacuum with a 0.1 mm separation. The tip of the flux guide was in air. The rod diameter and length of the flux guide were 0.6 and 7 mm, respectively. The sharp tip of the flux guide required for high spatial resolution was prepared by microelectropolishing. Its tip radius was less than 1 µm. The static magnetic field pattern of magnetized toner particles was detected by this system and we obtained a high-resolution magnetic image with a spatial resolution of several microns.

  7. Faraday tomography: a new, three-dimensional probe of the interstellar magnetic field

    NASA Astrophysics Data System (ADS)

    Ferrière, Katia

    2016-11-01

    Much of our present observational knowledge of the interstellar magnetic field of our Galaxy comes from two different sources, both of which involve mechanisms operating at radio wavelengths: the first one is the Faraday rotation of linearly-polarized radio waves propagating through the magneto-ionic interstellar medium, and the second one is the diffuse synchrotron emission from our Galaxy. I will review what these two classical probes have taught us about the strength, the direction/orientation, and the spatial distribution of the interstellar magnetic field. I will then present a recent method, known as Faraday tomography or rotation measure synthesis, which relies on a combination of Faraday rotation and synchrotron emission and which makes it possible to probe the interstellar magnetic field in three dimensions.

  8. Electromechanical flight control actuator

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The feasibility of using an electromechanical actuator (EMA) as the primary flight control equipment in aerospace flight is examined. The EMA motor design is presented utilizing improved permanent magnet materials. The necessary equipment to complete a single channel EMA using the single channel power electronics breadboard is reported. The design and development of an improved rotor position sensor/tachometer is investigated.

  9. Three axis vector magnet set-up for cryogenic scanning probe microscopy.

    PubMed

    Galvis, J A; Herrera, E; Guillamón, I; Azpeitia, J; Luccas, R F; Munuera, C; Cuenca, M; Higuera, J A; Díaz, N; Pazos, M; García-Hernandez, M; Buendía, A; Vieira, S; Suderow, H

    2015-01-01

    We describe a three axis vector magnet system for cryogenic scanning probe microscopy measurements. We discuss the magnet support system and the power supply, consisting of a compact three way 100 A current source. We obtain tilted magnetic fields in all directions with maximum value of 5T along z-axis and of 1.2T for XY-plane magnetic fields. We describe a scanning tunneling microscopy-spectroscopy (STM-STS) set-up, operating in a dilution refrigerator, which includes a new high voltage ultralow noise piezodrive electronics and discuss the noise level due to vibrations. STM images and STS maps show atomic resolution and the tilted vortex lattice at 150 mK in the superconductor β-Bi2Pd. We observe a strongly elongated hexagonal lattice, which corresponds to the projection of the tilted hexagonal vortex lattice on the surface. We also discuss Magnetic Force Microscopy images in a variable temperature insert.

  10. Scanned probe imaging of nanoscale magnetism at cryogenic temperatures with a single-spin quantum sensor

    NASA Astrophysics Data System (ADS)

    Pelliccione, Matthew; Jenkins, Alec; Ovartchaiyapong, Preeti; Reetz, Christopher; Emmanuelidu, Eve; Ni, Ni; Bleszynski Jayich, Ania

    The nitrogen vacancy (NV) defect in diamond has emerged as a promising candidate for high resolution magnetic imaging based on its atomic size and quantum-limited sensing capabilities afforded by long spin coherence times. Although the NV center has been successfully implemented as a nanoscale scanning magnetic probe at room temperature, it has remained an outstanding challenge to extend this capability to cryogenic temperatures, where many solid-state systems exhibit non-trivial magnetic order. In this talk, we present NV magnetic imaging at T = 6 K, first benchmarking the technique with a magnetic hard disk sample, then utilizing the technique to image vortices in the iron pnictide superconductor BaFe2(As0.7P0.3)2 with Tc = 30 K. In addition, we discuss other candidate solid-state systems that can benefit from the high spatial resolution and field sensitivity of the scanning NV magnetometer.

  11. Three axis vector magnet set-up for cryogenic scanning probe microscopy

    SciTech Connect

    Galvis, J. A.; Herrera, E.; Buendía, A.; Guillamón, I.; Vieira, S.; Suderow, H.; Azpeitia, J.; Luccas, R. F.; Munuera, C.; García-Hernandez, M.; and others

    2015-01-15

    We describe a three axis vector magnet system for cryogenic scanning probe microscopy measurements. We discuss the magnet support system and the power supply, consisting of a compact three way 100 A current source. We obtain tilted magnetic fields in all directions with maximum value of 5T along z-axis and of 1.2T for XY-plane magnetic fields. We describe a scanning tunneling microscopy-spectroscopy (STM-STS) set-up, operating in a dilution refrigerator, which includes a new high voltage ultralow noise piezodrive electronics and discuss the noise level due to vibrations. STM images and STS maps show atomic resolution and the tilted vortex lattice at 150 mK in the superconductor β-Bi{sub 2}Pd. We observe a strongly elongated hexagonal lattice, which corresponds to the projection of the tilted hexagonal vortex lattice on the surface. We also discuss Magnetic Force Microscopy images in a variable temperature insert.

  12. Variation of the ion composition in the ring current during magnetic storms: Van Allen Probes observations

    NASA Astrophysics Data System (ADS)

    Luo, Hao; Du, Aimin; Ge, Yasong; Cao, Xin; Zhang, Ying; Wang, Yuan

    2015-04-01

    It has been reported that the energy density of the oxygen ions in the ring current region will show more enhancements than protons during magnetic storms. Knowing how the ion composition changes during a magnetic storm is important for understanding the dynamic processes in the inner magnetosphere. By using ion flux data from HOPE and RBSPICE instruments on board the Van Allen probes, we study the energy density variation of both protons and oxygen ions during fifteen strong magnetic storms (minimum Dst < -80 nT) happened during year 2013 to 2014. Results provide important details about the ion composition at different storm stages and different magnetic local times. Results also give important indications about the ion acceleration in the inner magnetosphere and the source of the ring current ions during the magnetic storms.

  13. SPIN POLARIZED PHOTOELECTRON SPECTROSCOPY AS A PROBE OF MAGNETIC SYSTEMS.

    SciTech Connect

    JOHNSON, P.D.; GUNTHERODT, G.

    2006-11-01

    Spin-polarized photoelectron spectroscopy has developed into a versatile tool for the study of surface and thin film magnetism. In this chapter, we examine the methodology of the technique and its recent application to a number of different problems. We first examine the photoemission process itself followed by a detailed review of spin-polarization measurement techniques and the related experimental requirements. We review studies of spin polarized surface states, interface states and quantum well states followed by studies of the technologically important oxide systems including half-metallic transition metal oxides, ferromagnet/oxide interfaces and the antiferromagnetic cuprates that exhibit high Tc Superconductivity. We also discuss the application of high-resolution photoemission with spin resolving capabilities to the study of spin dependent self energy effects.

  14. Batch-fabrication of cantilevered magnets on attonewton-sensitivity mechanical oscillators for scanned-probe nanoscale magnetic resonance imaging

    PubMed Central

    Hickman, Steven A.; Moore, Eric W.; Lee, SangGap; Longenecker, Jonilyn G.; Wright, Sarah J.; Harrell, Lee E.; Marohn, John A.

    2015-01-01

    We have batch-fabricated cantilevers with ~100 nm diameter nickel nanorod tips and force sensitivities of a few attonewtons at 4.2 kelvin. The magnetic nanorods were engineered to overhang the leading edge of the cantilever and, consequently, the cantilevers experience what we believe is the lowest surface noise ever achieved in a scanned probe experiment. Cantilever magnetometry indicated that the tips were well magnetized, with a ≤ 20 nm dead layer; the composition of the dead layer was studied by electron microscopy and electron energy loss spectroscopy. In what we believe is the first demonstration of scanned probe detection of electron-spin resonance from a batch fabricated tip, the cantilevers were used to observe electron-spin resonance from nitroxide spin labels in a film via force-gradient-induced shifts in cantilever resonance frequency. The magnetic field dependence of the magnetic resonance signal suggests a non-uniform tip magnetization at an applied field near 0.6 T. PMID:21082863

  15. Batch-fabrication of cantilevered magnets on attonewton-sensitivity mechanical oscillators for scanned-probe nanoscale magnetic resonance imaging.

    PubMed

    Hickman, Steven A; Moore, Eric W; Lee, SangGap; Longenecker, Jonilyn G; Wright, Sarah J; Harrell, Lee E; Marohn, John A

    2010-12-28

    We have batch-fabricated cantilevers with ∼100 nm diameter nickel nanorod tips and force sensitivities of a few attonewtons at 4.2 K. The magnetic nanorods were engineered to overhang the leading edge of the cantilever, and consequently the cantilevers experience what we believe is the lowest surface noise ever achieved in a scanned probe experiment. Cantilever magnetometry indicated that the tips were well magnetized, with a ≤ 20 nm dead layer; the composition of the dead layer was studied by electron microscopy and electron energy loss spectroscopy. In what we believe is the first demonstration of scanned probe detection of electron-spin resonance from a batch-fabricated tip, the cantilevers were used to observe electron-spin resonance from nitroxide spin labels in a film via force-gradient-induced shifts in cantilever resonance frequency. The magnetic field dependence of the magnetic resonance signal suggests a nonuniform tip magnetization at an applied field near 0.6 T.

  16. DIII-D Equilibrium Reconstructions with New 3D Magnetic Probes

    NASA Astrophysics Data System (ADS)

    Lao, Lang; Strait, E. J.; Ferraro, N. M.; Ferron, J. R.; King, J. D.; Lee, X.; Meneghini, O.; Turnbull, A. D.; Huang, Y.; Qian, J. G.; Wingen, A.

    2015-11-01

    DIII-D equilibrium reconstructions with the recently installed new 3D magnetic diagnostic are presented. In addition to providing information to allow more accurate 2D reconstructions, the new 3D probes also provide useful information to guide computation of 3D perturbed equilibria. A new more comprehensive magnetic compensation has been implemented. Algorithms are being developed to allow EFIT to reconstruct 3D perturbed equilibria making use of the new 3D probes and plasma responses from 3D MHD codes such as GATO and M3D-C1. To improve the computation efficiency, all inactive probes in one of the toroidal planes in EFIT have been replaced with new probes from other planes. Other 3D efforts include testing of 3D reconstructions using V3FIT and a new 3D variational moment equilibrium code VMOM3D. Other EFIT developments include a GPU EFIT version and new safety factor and MSE-LS constraints. The accuracy and limitation of the new probes for 3D reconstructions will be discussed. Supported by US DOE under DE-FC02-04ER54698 and DE-FG02-95ER54309.

  17. Probing DNA helicase kinetics with temperature-controlled magnetic tweezers.

    PubMed

    Gollnick, Benjamin; Carrasco, Carolina; Zuttion, Francesca; Gilhooly, Neville S; Dillingham, Mark S; Moreno-Herrero, Fernando

    2015-03-18

    Motor protein functions like adenosine triphosphate (ATP) hydrolysis or translocation along molecular substrates take place at nanometric scales and consequently depend on the amount of available thermal energy. The associated rates can hence be investigated by actively varying the temperature conditions. In this article, a thermally controlled magnetic tweezers (MT) system for single-molecule experiments at up to 40 °C is presented. Its compact thermostat module yields a precision of 0.1 °C and can in principle be tailored to any other surface-coupled microscopy technique, such as tethered particle motion (TPM), nanopore-based sensing of biomolecules, or super-resolution fluorescence imaging. The instrument is used to examine the temperature dependence of translocation along double-stranded (ds)DNA by individual copies of the protein complex AddAB, a helicase-nuclease motor involved in dsDNA break repair. Despite moderately lower mean velocities measured at sub-saturating ATP concentrations, almost identical estimates of the enzymatic reaction barrier (around 21-24 k(B)T) are obtained by comparing results from MT and stopped-flow bulk assays. Single-molecule rates approach ensemble values at optimized chemical energy conditions near the motor, which can withstand opposing loads of up to 14 piconewtons (pN). Having proven its reliability, the temperature-controlled MT described herein will eventually represent a routinely applied method within the toolbox for nano-biotechnology.

  18. Probing DNA Helicase Kinetics with Temperature‐Controlled Magnetic Tweezers

    PubMed Central

    Gollnick, Benjamin; Carrasco, Carolina; Zuttion, Francesca; Gilhooly, Neville S.; Dillingham, Mark S.

    2014-01-01

    Motor protein functions like adenosine triphosphate (ATP) hydrolysis or translocation along molecular substrates take place at nanometric scales and consequently depend on the amount of available thermal energy. The associated rates can hence be investigated by actively varying the temperature conditions. In this article, a thermally controlled magnetic tweezers (MT) system for single‐molecule experiments at up to 40 °C is presented. Its compact thermostat module yields a precision of 0.1 °C and can in principle be tailored to any other surface‐coupled microscopy technique, such as tethered particle motion (TPM), nanopore‐based sensing of biomolecules, or super‐resolution fluorescence imaging. The instrument is used to examine the temperature dependence of translocation along double‐stranded (ds)DNA by individual copies of the protein complex AddAB, a helicase‐nuclease motor involved in dsDNA break repair. Despite moderately lower mean velocities measured at sub‐saturating ATP concentrations, almost identical estimates of the enzymatic reaction barrier (around 21–24 k B T) are obtained by comparing results from MT and stopped‐flow bulk assays. Single‐molecule rates approach ensemble values at optimized chemical energy conditions near the motor, which can withstand opposing loads of up to 14 piconewtons (pN). Having proven its reliability, the temperature‐controlled MT described herein will eventually represent a routinely applied method within the toolbox for nano‐biotechnology. PMID:25400244

  19. Nuclear magnetic resonance probes of membrane biophysics: Structure and dynamics

    NASA Astrophysics Data System (ADS)

    Leftin, Avigdor

    The phospholipid membrane is a self-assembled, dynamic molecular system that may exist alone in association with only water, or in complex systems comprised of multiple lipid types and proteins. In this dissertation the intra- and inter-molecular forces responsible for the atomistic, molecular and collective equilibrium structure and dynamics are studied by nuclear magnetic resonance spectroscopy (NMR). The multinuclear NMR measurements and various experimental techniques are able to provide data that enable the characterization of the hierarchical spatio-temporal organization of the phospholipid membrane. The experimental and theoretical studies conducted target membrane interactions ranging from model systems composed of only water and lipids, to multiple component domain forming membranes that are in association with peripheral and trans-membrane proteins. These measurements consisit of frequency spectrum lineshapes and nuclear-spin relaxation rates obtained using 2H NMR, 13C NMR, 31P NMR and 1H NMR. The changes of these experimental observables are interpreted within a statistical thermodynamic framework that allows the membrane structure, activation energies, and correlation times of motion to be determined. The cases presented demonstrate how fundamental principles of NMR spectroscopy may be applied to a host of membranes, leading to the biophysical characterization of membrane structure and dynamics.

  20. Electric and magnetic radial diffusion coefficients using the Van Allen probes data

    NASA Astrophysics Data System (ADS)

    Ali, Ashar F.; Malaspina, David M.; Elkington, Scot R.; Jaynes, Allison N.; Chan, Anthony A.; Wygant, John; Kletzing, Craig A.

    2016-10-01

    ULF waves are a common occurrence in the inner magnetosphere and they contribute to particle motion, significantly, at times. We used the magnetic and the electric field data from the Electric and Magnetic Field Instrument Suite and Integrated Sciences (EMFISIS) and the Electric Field and Waves instruments (EFW) on board the Van Allen Probes to estimate the ULF wave power in the compressional component of the magnetic field and the azimuthal component of the electric field, respectively. Using L∗, Kp, and magnetic local time (MLT) as parameters, we conclude that the noon sector contains higher ULF Pc-5 wave power compared with the other MLT sectors. The dawn, dusk, and midnight sectors have no statistically significant difference between them. The drift-averaged power spectral densities are used to derive the magnetic and the electric component of the radial diffusion coefficient. Both components exhibit little to no energy dependence, resulting in simple analytic models for both components. More importantly, the electric component is larger than the magnetic component by one to two orders of magnitude for almost all L∗ and Kp; thus, the electric field perturbations are more effective in driving radial diffusion of charged particles in the inner magnetosphere. We also present a comparison of the Van Allen Probes radial diffusion coefficients, including the error estimates, with some of the previous published results. This allows us to gauge the large amount of uncertainty present in such estimates.

  1. Magnetically filtered Faraday probe for measuring the ion current density profile of a Hall thruster

    SciTech Connect

    Rovey, Joshua L.; Walker, Mitchell L.R.; Gallimore, Alec D.; Peterson, Peter Y.

    2006-01-15

    The ability of a magnetically filtered Faraday probe (MFFP) to obtain the ion current density profile of a Hall thruster is investigated. The MFFP is designed to eliminate the collection of low-energy, charge-exchange (CEX) ions by using a variable magnetic field as an ion filter. In this study, a MFFP, Faraday probe with a reduced acceptance angle (BFP), and nude Faraday probe are used to measure the ion current density profile of a 5 kW Hall thruster operating over the range of 300-500 V and 5-10 mg/s. The probes are evaluated on a xenon propellant Hall thruster in the University of Michigan Large Vacuum Test Facility at operating pressures within the range of 4.4x10{sup -4} Pa Xe (3.3x10{sup -6} Torr Xe) to 1.1x10{sup -3} Pa Xe (8.4x10{sup -6} Torr Xe) in order to study the ability of the Faraday probe designs to filter out CEX ions. Detailed examination of the results shows that the nude probe measures a greater ion current density profile than both the MFFP and BFP over the range of angular positions investigated for each operating condition. The differences between the current density profiles obtained by each probe are attributed to the ion filtering systems employed. Analysis of the results shows that the MFFP, operating at a +5 A solenoid current, provides the best agreement with flight-test data and across operating pressures.

  2. A 4 K cryogenic probe for use in magnetic resonance force microscopy experiments

    SciTech Connect

    Smith, Doran D.; Alexson, Dimitri A.; Garbini, Joseph L.

    2013-09-15

    The detailed design of a mechanically detected nuclear magnetic resonance probe using the SPAM (Springiness Preservation by Aligning Magnetization) geometry, operating at 4 K, in vacuum, and a several-Tesla magnetic field is described. The probe head is vibration-isolated well enough from the environment by a three-spring suspension system that the cantilever achieves thermal equilibrium with the environment without the aid of eddy current damping. The probe uses an ultra-soft Si cantilever with a Ni sphere attached to its tip, and magnetic resonance is registered as a change in the resonant frequency of the driven cantilever. The RF system uses frequency sweeps for adiabatic rapid passage using a 500 μm diameter RF coil wound around a sapphire rod. The RF coil and optical fiber of the interferometer used to sense the cantilever's position are both located with respect to the cantilever using a Garbini micropositioner, and the sample stage is mounted on an Attocube nanopositioner.

  3. A 4 K cryogenic probe for use in magnetic resonance force microscopy experiments.

    PubMed

    Smith, Doran D; Alexson, Dimitri A; Garbini, Joseph L

    2013-09-01

    The detailed design of a mechanically detected nuclear magnetic resonance probe using the SPAM (Springiness Preservation by Aligning Magnetization) geometry, operating at 4 K, in vacuum, and a several-Tesla magnetic field is described. The probe head is vibration-isolated well enough from the environment by a three-spring suspension system that the cantilever achieves thermal equilibrium with the environment without the aid of eddy current damping. The probe uses an ultra-soft Si cantilever with a Ni sphere attached to its tip, and magnetic resonance is registered as a change in the resonant frequency of the driven cantilever. The RF system uses frequency sweeps for adiabatic rapid passage using a 500 μm diameter RF coil wound around a sapphire rod. The RF coil and optical fiber of the interferometer used to sense the cantilever's position are both located with respect to the cantilever using a Garbini micropositioner, and the sample stage is mounted on an Attocube nanopositioner.

  4. A 4 K cryogenic probe for use in magnetic resonance force microscopy experiments

    NASA Astrophysics Data System (ADS)

    Smith, Doran D.; Alexson, Dimitri A.; Garbini, Joseph L.

    2013-09-01

    The detailed design of a mechanically detected nuclear magnetic resonance probe using the SPAM (Springiness Preservation by Aligning Magnetization) geometry, operating at 4 K, in vacuum, and a several-Tesla magnetic field is described. The probe head is vibration-isolated well enough from the environment by a three-spring suspension system that the cantilever achieves thermal equilibrium with the environment without the aid of eddy current damping. The probe uses an ultra-soft Si cantilever with a Ni sphere attached to its tip, and magnetic resonance is registered as a change in the resonant frequency of the driven cantilever. The RF system uses frequency sweeps for adiabatic rapid passage using a 500 μm diameter RF coil wound around a sapphire rod. The RF coil and optical fiber of the interferometer used to sense the cantilever's position are both located with respect to the cantilever using a Garbini micropositioner, and the sample stage is mounted on an Attocube nanopositioner.

  5. Design and calibration of high-frequency magnetic probes for the SUNIST spherical tokamak

    NASA Astrophysics Data System (ADS)

    Liu, Yangqing; Tan, Yi; Pan, Ou; Ke, Rui; Wang, Wenhao; Gao, Zhe

    2014-11-01

    A new high-frequency magnetic diagnostic system is designed, installed, and calibrated in the Sino-United Spherical Tokamak (SUNIST) to investigate Alfvén waves (AWs). The system consists of a fixed toroidal array and a movable radial array of high-frequency magnetic probes (HFMPs) with 21 and 60 probes, respectively. Based on the method of vacuum enameled wire wound on ceramic bobbins, the fixed toroidal array is located as near as possible to the plasma and carefully shielded to reduce the attenuation of high-frequency magnetic field. Meanwhile, by using the technology of commercial chip inductors mounted on printed circuit boards, the movable radial array is inserted into a thin quartz tube that allows positioning along radial direction. A Helmholtz coil is utilized to calibrate the effective areas as well as the frequency response of each HFMP. The calibration results are consistent with the calculated results of an equivalent probe-and-cable circuit model. High-frequency magnetic signals related to AW are detected with these HFMPs. These HFMPs are expected to play a key role in analyzing Alfvén eigenmodes excited by AW antenna in the SUNIST.

  6. Magnetic induction spectroscopy (MIS)-probe design for cervical tissue measurements.

    PubMed

    Wang, Jau-Yi; Healey, Timothy; Barker, Anthony; Brown, Brian; Monk, Chris; Anumba, Dilly

    2017-05-01

    Gradiometers have the advantage of increasing measuring sensitivity, which is particularly useful in magnetic induction spectroscopy (MIS) for bio-impedance measurements. Traditional gradiometers use a pair of field sensing coils equally distant and on opposite sides of a drive coil, which provides high immunity to interference. In this paper, a ferrite-cored coaxial gradiometer probe of 29 mm diameter has been developed for measuring the impedance spectra of cervical tissues in vivo. It consists of a ferrite rod with outer ferrite confinement screening in order to eliminate the signals from surrounding tissue. The magnetic screening efficiency was compared with an air-cored gradiometer probe. For both gradiometer probes, a drive coil and two sensing coils were wound on a borosilicate glass former aligned coaxially with two sensing coils equidistant from the drive coil. The signal sensitivity of those two MIS gradiometers has been measured using saline samples with a conductivity range between 0.1 and 1.1 S m(-1). Finite element methods using COMSOL Multiphysics have been used to simulate the distribution of sensitivity to conductivity over the face of each probe and with depth. The ferrite-cored probe has a sensitivity confined to the volume defined by the gap between the ferrite core and outer tube of ferrite while the air-cored probe without any magnetic shielding had a wide sensitivity over the face and the side of the probe. Four saline samples and one of distilled water with conductivities from 0.1 to 1.1 S m(-1) have been used to make conductivity measurements at frequencies of 50 kHz, 100 kHz, and 300 kHz. The measurement accuracy of the air-cored MIS probe was 0.09 S m(-1) at 50 kHz, improving to 0.05 S m(-1) at 300 kHz. For the ferrite-cored MIS probe, the measurement accuracy was 0.28 S m(-1) at 50 kHz, improving to 0.04 S m(-1) at 300 kHz. In vivo measurements on human hand have been performed using both types of gradiometers and the

  7. Continuous Magnetic Field Monitoring Using Rapid Re-Excitation of NMR Probe Sets.

    PubMed

    Dietrich, Benjamin E; Brunner, David O; Wilm, Bertram J; Barmet, Christoph; Pruessmann, Klaas P

    2016-06-01

    MRI relies on static and spatially varying dynamic magnetic fields of high accuracy. NMR field probes permit the direct observation of spatiotemporal field dynamics for diverse purposes such as data correction, field control, sequence validation, and hardware characterization. However, due to probe signal decay and dephasing existing field cameras are limited in terms of readout duration and the extent of k -space that can be covered. The present work aims to overcome these limitations by the transition to short-lived NMR probes and rapid re-excitation. The proposed approach uses probes with T 2 so short that thermal relaxation dominates signal decay even in the presence of strongest gradients. They are integrated with transmit, receive and sequencing electronics that permit high-rate re-excitation with optional probe alternation as well as complementary RF pulse recording. The system is demonstrated by monitoring of sample MRI sequences with long readouts and large gradient moments. It is compared with the conventional long-lived probe concept and characterized in terms of net sensitivity and sources of systematic error. Continuous k -space trajectory mapping is demonstrated and validated by trajectory-based image reconstruction.

  8. Probing Brownian relaxation in water-glycerol mixtures using magnetic hyperthermia

    NASA Astrophysics Data System (ADS)

    Nemala, Humeshkar; Milgie, Michael; Wadehra, Anshu; Thakur, Jagdish; Naik, Vaman; Naik, Ratna

    2013-03-01

    Generation of heat by magnetic nanoparticles in the presence of an external oscillating magnetic field is known as magnetic hyperthermia (MHT). This heat is generated by two mechanisms: the Neel relaxation and Brownian relaxation. While the internal spin relaxation of the nanoparticles known as Neel relaxation is largely dependent on the magnetic properties of the nanoparticles, the physical motion of the particle or the Brownian relaxation is largely dependent on the viscous properties of the carrier liquid. The MHT properties of dextran coated iron oxide nanoparticles have been investigated at a frequency of 400KHz. To understand the influence of Brownian relaxation on heating, we probe the MHT properties of these ferrofluids in water-glycerol mixtures of varying viscosities. The heat generation is quantified using the specific absorption rate (SAR) and its maximum at a particular temperature is discussed with reference to the viscosity.

  9. Understanding temperature and magnetic-field actuated magnetization polarity reversal in the Prussian blue analogue Cu0.73Mn0.77[Fe(CN)6].zH2O, using XMCD

    SciTech Connect

    Lahiri, Debdutta; Choi, Yongseong; Kumar, Amit; Ramanan, Nitya; Chattopadhyay, Soma; Sharma, Surinder; Haskel, Daniel; Yusuf, S. M.

    2016-03-01

    We have investigated the microscopic origin of temperature and magnetic-field actuated magnetization reversal in Cu0.73Mn0.77[Fe(CN)(6)]center dot zH(2)O, using XMCD. Our results show a fair deviation from the mean-field-theory in the form of different ordering temperatures of Fe and Mn sublattices. A preferential sign reversal of Mn spin under magnetic field and different spin cant angles for the two sublattices have also been observed. An antiferromagnetic coupling between the Fe and Mn sublattices along with different ordering temperatures (sublattice decoupling) for these sublattices explain the temperature-dependent magnetization reversal. Whereas, Mn spin reversal alone (under external magnetic field) is responsible for the observed field-dependent magnetization reversal. The dissimilar magnetic behavior of Fe and Mn sublattices in this cubic 3d-orbital system has been understood by invoking disparity and competition among inter-sublattice magnetic control parameters, viz. magnetic Zeeman energy, exchange coupling constant and magnetic anisotropy constant. Our results have significant design implications for future magnetic switches, by optimizing the competition among these magnetic control parameters.

  10. [Preparation of magnetic resonance molecular probe for breast cancer detection in vitro].

    PubMed

    Li, Xu-bin; DU, Xiang-ke; Huo, Tian-long; Liu, Xia; Zhang, Sen

    2009-04-18

    To prepare magnetic resonance (MR) molecular probe for somatostain receptor expressed on breast cancer cell membranes and investigate its physico-chemical properties and imaging features in vitro. Molecular probe was prepared through superparamagnetic iron oxide (SPIO) conjugated to somatostatin analog-octreotide (OCT) using chemical method. Its features at different Fe(2+) concentrations were tested by MTT assay and Prussian blue staining respectively. Molecular probes at different Fe(2+) concentration and various numbers of cells labeled with the probe at Fe(2+) concentrations of 20 mg/L were scanned with 1.5 Tesla MR. Resovist was used in control group when labeling cells. Various blue-staining particles were found in the cytoplasms of labeled cells with the molecular probes at different concentrations after Prussion blue staining and there were more particles with the increase of Fe(2+) concentration. The label rate of the probe was 96.15% which was higher than that in control group (80.00%). The bioactivity had no difference between labeled and non-labeled cells (P>0.05). There was remarkable low signal intensity on T(2)-weighed imaging and no evident artifacts for molecular probe when the concentration of Fe(2+) was 20 mg/L. The least number of labeled cells detected by MR in vitro was 6 x 10(6) when the concentration of Fe(2+) was 20 mg/L. Molecular probe, SPIO-OCT, can effectively label breast cells which express SSTR. The reasonable Fe(2+) concentration of labeled cells and imaging was 20 mg/L. There is a correlation between MR signal intensity in vitro and the number of labeled cells.

  11. Magnetic flux dynamics in superconducting films studied by scanning Hall probe microscopy

    NASA Astrophysics Data System (ADS)

    Stan, Gheorghe

    In this thesis we address two different issues in the field of flux dynamics in superconductors with constricted geometry. In our experiments we used scanning Hall probe microscopy to investigate the magnetic field profile above the samples' surface. In the first experiment, Vortex Nucleation in Narrow Thin-Film Strips, we studied the magnetic flux nucleation in type-II superconducting thin-film strips of mesoscopic width. The maximum magnetic field below which vortices are completely expelled from niobium narrow thin-film strips was measured for different widths. Above this threshold field we examined the field dependence of the vortex density for the studied strips. In the second experiment, The Superconducting Dripping Faucet , we analyzed, in microbridge geometry, the dynamics of the magnetic flux nucleation in a one-dimensional type-I superconducting channel. For this experiment we have developed a novel high-bandwidth Hall probe to detect in real time the nucleation and subsequent motion of the magnetic flux tubes along a fabricated one-dimensional channel in a lead film. The complex dynamics exhibited by the flux tubes nucleating from one end of the channel shares many characteristics of the well-known dripping faucet experiment. Nonlinear time series analysis was used to investigate the dynamics of the flux tubes in our experiment.

  12. New probe of magnetic fields in the pre-reionization epoch. II. Detectability

    NASA Astrophysics Data System (ADS)

    Gluscevic, Vera; Venumadhav, Tejaswi; Fang, Xiao; Hirata, Christopher; Oklopčić, Antonija; Mishra, Abhilash

    2017-04-01

    In the first paper of this series, we proposed a novel method to probe large-scale intergalactic magnetic fields during the cosmic Dark Ages, using 21-cm tomography. This method relies on the effect of spin alignment of hydrogen atoms in a cosmological setting, and on the effect of magnetic precession of the atoms on the statistics of the 21-cm brightness-temperature fluctuations. In this paper, we forecast the sensitivity of future tomographic surveys to detecting magnetic fields using this method. For this purpose, we develop a minimum-variance estimator formalism to capture the characteristic anisotropy signal using the two-point statistics of the brightness-temperature fluctuations. We find that, depending on the reionization history, and subject to the control of systematics from foreground subtraction, an array of dipole antennas in a compact-grid configuration with a collecting area slightly exceeding one square kilometer can achieve a 1 σ detection of ˜10-21 Gauss comoving (scaled to present-day value) within three years of observation. Using this method, tomographic 21-cm surveys could thus probe ten orders of magnitude below current cosmic microwave background constraints on primordial magnetic fields, and provide exquisite sensitivity to large-scale magnetic fields in situ at high redshift.

  13. A portable Hall magnetometer probe for characterization of magnetic iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Araujo, Jefferson F. D. F.; Costa, Mateus C.; Louro, Sonia R. W.; Bruno, Antonio C.

    2017-03-01

    We have built a portable Hall magnetometer probe, for measuring magnetic properties of iron oxide nanoparticles, that can be used for bulk materials and liquid samples as well. The magnetometer probe consists of four voltage-programmable commercial Hall sensors and a thin acrylic plate for positioning the sensors. In order to operate, it needs to be attached to a pole of an electromagnet and connected to an AD converter and a computer. It acquires a complete magnetization curve in a couple of minutes and has a magnetic moment sensitivity of 3.5×10-7 Am2. We tested its performance with magnetic nanoparticles containing an iron oxide core and having coating layers with different sizes. The magnetization results obtained were compared with measurements performed on commercial stand-alone magnetometers, and exhibited errors of about ±0.2 Am2/kg (i.e 0.4%) at saturation and below 0.5 Am2/kg (i.e. 10%) at remanence.

  14. Achieving atomic resolution magnetic dichroism by controlling the phase symmetry of an electron probe

    DOE PAGES

    Rusz, Jan; Idrobo, Juan -Carlos; Bhowmick, Somnath

    2014-09-30

    The calculations presented here reveal that an electron probe carrying orbital angular momentum is just a particular case of a wider class of electron beams that can be used to measure electron magnetic circular dichroism (EMCD) with atomic resolution. It is possible to obtain an EMCD signal with atomic resolution by simply breaking the symmetry of the electron probe phase front using the aberration-corrected optics of a scanning transmission electron microscope. The probe’s required phase distribution depends on the sample’s magnetic symmetry and crystal structure. The calculations indicate that EMCD signals that use the electron probe’s phase are as strongmore » as those obtained by nanodiffraction methods.« less

  15. Achieving atomic resolution magnetic dichroism by controlling the phase symmetry of an electron probe

    SciTech Connect

    Rusz, Jan; Idrobo, Juan -Carlos; Bhowmick, Somnath

    2014-09-30

    The calculations presented here reveal that an electron probe carrying orbital angular momentum is just a particular case of a wider class of electron beams that can be used to measure electron magnetic circular dichroism (EMCD) with atomic resolution. It is possible to obtain an EMCD signal with atomic resolution by simply breaking the symmetry of the electron probe phase front using the aberration-corrected optics of a scanning transmission electron microscope. The probe’s required phase distribution depends on the sample’s magnetic symmetry and crystal structure. The calculations indicate that EMCD signals that use the electron probe’s phase are as strong as those obtained by nanodiffraction methods.

  16. Development of internal magnetic probe for current density profile measurement in Versatile Experiment Spherical Torus.

    PubMed

    Yang, J; Lee, J W; Jung, B K; Chung, K J; Hwang, Y S

    2014-11-01

    An internal magnetic probe using Hall sensors to measure a current density profile directly with perturbation of less than 10% to the plasma current is successfully operated for the first time in Versatile Experiment Spherical Torus (VEST). An appropriate Hall sensor is chosen to produce sufficient signals for VEST magnetic field while maintaining the small size of 10 mm in outer diameter. Temperature around the Hall sensor in a typical VEST plasma is regulated by blown air of 2 bars. First measurement of 60 kA VEST ohmic discharge shows a reasonable agreement with the total plasma current measured by Rogowski coil in VEST.

  17. Development of internal magnetic probe for current density profile measurement in Versatile Experiment Spherical Torus

    NASA Astrophysics Data System (ADS)

    Yang, J.; Lee, J. W.; Jung, B. K.; Chung, K. J.; Hwang, Y. S.

    2014-11-01

    An internal magnetic probe using Hall sensors to measure a current density profile directly with perturbation of less than 10% to the plasma current is successfully operated for the first time in Versatile Experiment Spherical Torus (VEST). An appropriate Hall sensor is chosen to produce sufficient signals for VEST magnetic field while maintaining the small size of 10 mm in outer diameter. Temperature around the Hall sensor in a typical VEST plasma is regulated by blown air of 2 bars. First measurement of 60 kA VEST ohmic discharge shows a reasonable agreement with the total plasma current measured by Rogowski coil in VEST.

  18. Use of a probing pulsed magnetic field for determining plasma parameters

    NASA Astrophysics Data System (ADS)

    Rousskikh, A. G.; Oreshkin, V. I.; Zhigalin, A. S.; Yushkov, G. Yu.

    2016-11-01

    A novel, simple, and readily usable method is proposed for measuring the electrical conductivity and temperature of a plasma. The method is based on the interaction of the test plasma with a pulsed magnetic field. The electric signals induced by the magnetic field in the circuits of two probes (miniature solenoids), one immersed in the test plasma and the other placed outside the plasma, provide data for estimating the plasma parameters. The method was verified experimentally by determining the parameters of the plasma flows generated in the cathode spots high-current pulsed vacuum arcs that were used to form cylindrical shells of bismuth Z-pinch plasma.

  19. The rectangular array of magnetic probes on J-TEXT tokamak

    NASA Astrophysics Data System (ADS)

    Chen, Zhipeng; Li, Fuming; Zhuang, Ge; Jian, Xiang; Zhu, Lizhi

    2016-11-01

    The rectangular array of magnetic probes system was newly designed and installed in the torus on J-TEXT tokamak to measure the local magnetic fields outside the last closed flux surface at a single toroidal angle. In the implementation, the experimental results agree well with the theoretical results based on the Spool model and three-dimensional numerical finite element model when the vertical field was applied. Furthermore, the measurements were successfully used as the input of EFIT code to conduct the plasma equilibrium reconstruction. The calculated Faraday rotation angle using the EFIT output is in agreement with the measured one from the three-wave polarimeter-interferometer system.

  20. Smart magnetic nanoparticle-aptamer probe for targeted imaging and treatment of hepatocellular carcinoma.

    PubMed

    Pilapong, Chalermchai; Sitthichai, Sudarat; Thongtem, Somchai; Thongtem, Titipun

    2014-10-01

    We report herein the development of a smart magnetic nanoparticle-aptamer probe, or theranostic nanoprobe, which can be used for targeted imaging and as a drug carrier for hepatocellular carcinoma treatment. The theranostic nanoprobe combines the delivery potential of a non-toxic cellulose derivative polymer, specific capability of cancer-specific molecule (DNA-based EpCAM aptamer) and the imaging capability of magnetic iron oxide nanoparticles. Our proof-of-concept design demonstrates efficient in vitro MR imaging of the cancer cells, and enhanced delivery of an anticancer drug into the cancer cells with comparable treatment efficacy. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. The rectangular array of magnetic probes on J-TEXT tokamak.

    PubMed

    Chen, Zhipeng; Li, Fuming; Zhuang, Ge; Jian, Xiang; Zhu, Lizhi

    2016-11-01

    The rectangular array of magnetic probes system was newly designed and installed in the torus on J-TEXT tokamak to measure the local magnetic fields outside the last closed flux surface at a single toroidal angle. In the implementation, the experimental results agree well with the theoretical results based on the Spool model and three-dimensional numerical finite element model when the vertical field was applied. Furthermore, the measurements were successfully used as the input of EFIT code to conduct the plasma equilibrium reconstruction. The calculated Faraday rotation angle using the EFIT output is in agreement with the measured one from the three-wave polarimeter-interferometer system.

  2. Flexure-based nanomagnetic actuators

    NASA Astrophysics Data System (ADS)

    Vasquez, Daniel James

    Nanometer-scale actuators powered through applied-magnetic fields have been designed, fabricated, and tested. These actuators consist of one or more ferromagnetic elements attached to a mechanical flexure. Two types of flexures were studied including a cantilever beam that is fixed on one end, and free on the other. The free end of the cantilever is attached to a, ferromagnetic element allowing a bending torque to be applied by a magnetic field. The second type of actuator design uses a set of torsion beams that are each anchored on one end, and attached to the magnetic element on the other end. The torsion beams are designed such that the application of a magnetic field will result in a twist along the long axis of the beam with little to no bending. The smallest fabricated and tested device is a cantilever-based ferromagnetic actuator that consists of a single 1.5-mum-long, 338-nm-wide, and 50-nm-thick nickel element, and a 2.2-mum-long, 110-nm-wide, and 30-nm-thick gold cantilever beam. A deflection of over 17° was measured for this actuator, while a similar one with a 10.1-mum long cantilever beam experienced measured deflections up to 57°. Torsion-based ferromagnetic actuators have been fabricated and tested with 110-nm-wide, and 50-rim-thick magnetic elements. Such magnetic elements contain only a single saturated magnetic domain. The ultimate scalability of ferromagnetic actuation is limited by the ability of thermal noise to affect the temporal stability of a nanometer-scale magnet. Theory to describe thermal noise and ultimate scalability of the ferromagnetic actuators has been developed. The size of the ferromagnetic actuators studied in this manuscript are smaller than most plant and animal cells. This enables the possibility of such actuators to manipulate a, living cell on an intracellular level. Other potential applications of such small actuators include MHz, to GHz frequency resonators, and tunable optical filters.

  3. Magnetohydrodynamic mode identification from magnetic probe signals via a matched filter method

    NASA Astrophysics Data System (ADS)

    Edgell, Dana H.; Kim, Jin-Soo; Bogatu, Ioan N.; Humphreys, David A.; Turnbull, Alan D.

    2002-04-01

    A matched filter analysis has been developed to identify the amplitude and phase of magnetohydrodynamic modes in DIII-D tokamak plasmas using magnetic probe signals (δBp). As opposed to conventional Fourier spatial analysis of toroidally spaced probes, this analysis includes data from both toroidally and poloidally spaced magnetic probe arrays. Using additional probes both improves the statistics of the analysis and more importantly incorporates poloidal information into the mode analysis. The matched filter is a numeric filter that matches signals from the magnetic probes with numerically predicted signals for the mode. The numerical predictions are developed using EFIT equilibrium reconstruction data as input to the stability code GATO and the vacuum field code VACUUM. Changes is the plasma equilibrium that occur on the same time scale as the mode are taken into account by modeling simple matched filter vectors corresponding to changes in total plasma current, plus vertical and horizontal plasma shifts. The matched filter method works well when there is good understanding of a mode and good modeling of its structure. Matched filter analysis results for a fast growing ideal kink mode, where equilibrium change effects are minimal, show the effectiveness of this method. A slow growing resistive-wall mode (RWM) is also analyzed using the matched filter method. The method gives good results for identifying the amplitude and phase of the RWM but the simple equilibrium vectors are insufficient for complete elimination of equilibrium changes on this time scale. An analysis of the computational requirements of the scheme indicates that real-time application of the matched filter for RWM identification will be possible.

  4. Sensor probes and phantoms for advanced transcranial magnetic stimulation system developments

    NASA Astrophysics Data System (ADS)

    Meng, Qinglei; Patel, Prashil; Trivedi, Sudhir; Du, Xiaoming; Hong, Elliot; Choa, Fow-Sen

    2015-05-01

    Transcranial magnetic stimulation (TMS) has become one of the most widely used noninvasive method for brain tissue stimulation and has been used as a treatment tool for various neurological and psychiatric disorders including migraine, stroke, Parkinson's disease, dystonia, tinnitus and depression. In the process of developing advanced TMS deep brain stimulation tools, we need first to develop field measurement devices like sensory probes and brain phantoms, which can be used to calibrate the TMS systems. Currently there are commercially available DC magnetic or electric filed measurement sensors, but there is no instrument to measure transient fields. In our study, we used a commercial figure-8 shaped TMS coil to generate transient magnetic field and followed induced field and current. The coil was driven by power amplified signal from a pulse generator with tunable pulse rate, amplitude, and duration. In order to obtain a 3D plot of induced vector electric field, many types of probes were designed to detect single component of electric-field vectors along x, y and z axis in the space around TMS coil. We found that resistor probes has an optimized signal-to-noise ratio (SNR) near 3k ohm but it signal output is too weak compared with other techniques. We also found that inductor probes can have very high output for Curl E measurement, but it is not the E-field distribution we are interested in. Probes with electrical wire wrapped around iron coil can directly measure induced E-field with high sensitivity, which matched computer simulation results.

  5. In situ magnetic compensation for potassium spin-exchange relaxation-free magnetometer considering probe beam pumping effect.

    PubMed

    Fang, Jiancheng; Wang, Tao; Quan, Wei; Yuan, Heng; Zhang, Hong; Li, Yang; Zou, Sheng

    2014-06-01

    A novel method to compensate the residual magnetic field for an atomic magnetometer consisting of two perpendicular beams of polarizations was demonstrated in this paper. The method can realize magnetic compensation in the case where the pumping rate of the probe beam cannot be ignored. In the experiment, the probe beam is always linearly polarized, whereas, the probe beam contains a residual circular component due to the imperfection of the polarizer, which leads to the pumping effect of the probe beam. A simulation of the probe beam's optical rotation and pumping rate was demonstrated. At the optimized points, the wavelength of the probe beam was optimized to achieve the largest optical rotation. Although, there is a small circular component in the linearly polarized probe beam, the pumping rate of the probe beam was non-negligible at the optimized wavelength which if ignored would lead to inaccuracies in the magnetic field compensation. Therefore, the dynamic equation of spin evolution was solved by considering the pumping effect of the probe beam. Based on the quasi-static solution, a novel magnetic compensation method was proposed, which contains two main steps: (1) the non-pumping compensation and (2) the sequence compensation with a very specific sequence. After these two main steps, a three-axis in situ magnetic compensation was achieved. The compensation method was suitable to design closed-loop spin-exchange relaxation-free magnetometer. By a combination of the magnetic compensation and the optimization, the magnetic field sensitivity was approximately 4 fT/Hz(1/2), which was mainly dominated by the noise of the magnetic shield.

  6. In situ magnetic compensation for potassium spin-exchange relaxation-free magnetometer considering probe beam pumping effect

    SciTech Connect

    Fang, Jiancheng; Wang, Tao Quan, Wei; Yuan, Heng; Li, Yang; Zhang, Hong; Zou, Sheng

    2014-06-15

    A novel method to compensate the residual magnetic field for an atomic magnetometer consisting of two perpendicular beams of polarizations was demonstrated in this paper. The method can realize magnetic compensation in the case where the pumping rate of the probe beam cannot be ignored. In the experiment, the probe beam is always linearly polarized, whereas, the probe beam contains a residual circular component due to the imperfection of the polarizer, which leads to the pumping effect of the probe beam. A simulation of the probe beam's optical rotation and pumping rate was demonstrated. At the optimized points, the wavelength of the probe beam was optimized to achieve the largest optical rotation. Although, there is a small circular component in the linearly polarized probe beam, the pumping rate of the probe beam was non-negligible at the optimized wavelength which if ignored would lead to inaccuracies in the magnetic field compensation. Therefore, the dynamic equation of spin evolution was solved by considering the pumping effect of the probe beam. Based on the quasi-static solution, a novel magnetic compensation method was proposed, which contains two main steps: (1) the non-pumping compensation and (2) the sequence compensation with a very specific sequence. After these two main steps, a three-axis in situ magnetic compensation was achieved. The compensation method was suitable to design closed-loop spin-exchange relaxation-free magnetometer. By a combination of the magnetic compensation and the optimization, the magnetic field sensitivity was approximately 4 fT/Hz{sup 1/2}, which was mainly dominated by the noise of the magnetic shield.

  7. Electromechanical actuators

    NASA Technical Reports Server (NTRS)

    Bigham, J.

    1982-01-01

    Materials illustrating a presentation on the development of electromechanical actuators (EMA) for electric flight systems are presented. Technology issues are identified, and major steps relative to EMA development, NASA's role, and a technology procurement plan are outlined.

  8. High-sensitivity detection of static magnetic field in a SQUID probe microscope

    NASA Astrophysics Data System (ADS)

    Hayashi, Tadayuki; Wang, Huiwu; Itozaki, Hideo

    2006-05-01

    We have developed a high-Tc SQUID probe microscope. A high permeability probe was used as a flux guide to improve its spatial resolution. The SQUID head with the probe makes it possible to measure samples with high spatial resolution in air at room temperature. To achieve a high spatial resolution, the microscope should have high signal to noise (S/N) ratio. We have investigated a modulation method of the static magnetic field emanating from a sample with the aim of achieving a higher S/N ratio. The sample stage was vibrated perpendicular to the plane of the SQUID with a frequency of 120 Hz by being mounted on a piezo stage attached to a mechanical stage. The oscillation amplitude of the sample was about 44 µm when the piezo stage was vibrated with amplitude 20 µm. The SQUID output was connected to a lock-in amplifier, and the magnetic field signal was obtained using lock-in detection. In order to evaluate the performance of this modulation method, we measured static magnetic field distributions of fine meander lines and fine patterns of a Ni thin film. Observed line scans showed that the improved S/N ratio of the SQUID microscope led to a higher spatial resolution.

  9. First experiments probing the collision of parallel magnetic fields using laser-produced plasmas

    DOE PAGES

    Rosenberg, M. J.; Li, C. K.; Fox, W.; ...

    2015-04-08

    Novel experiments to study the strongly-driven collision of parallel magnetic fields in β~10, laser-produced plasmas have been conducted using monoenergetic proton radiography. These experiments were designed to probe the process of magnetic flux pileup, which has been identified in prior laser-plasma experiments as a key physical mechanism in the reconnection of anti-parallel magnetic fields when the reconnection inflow is dominated by strong plasma flows. In the present experiments using colliding plasmas carrying parallel magnetic fields, the magnetic flux is found to be conserved and slightly compressed in the collision region. Two-dimensional (2D) particle-in-cell (PIC) simulations predict a stronger flux compressionmore » and amplification of the magnetic field strength, and this discrepancy is attributed to the three-dimensional (3D) collision geometry. Future experiments may drive a stronger collision and further explore flux pileup in the context of the strongly-driven interaction of magnetic fields.« less

  10. Scanning tunnelling spectroscopy as a probe of multi-Q magnetic states of itinerant magnets

    DOE PAGES

    Gastiasoro, Maria N.; Eremin, Ilya; Fernandes, Rafael M.; ...

    2017-02-08

    The combination of electronic correlations and Fermi surfaces with multiple nesting vectors can lead to the appearance of complex multi-Q magnetic ground states, hosting unusual states such as chiral density waves and quantum Hall insulators. Distinguishing single-Q and multi-Q magnetic phases is however a notoriously difficult experimental problem. Here we propose theoretically that the local density of states (LDOS) near a magnetic impurity, whose orientation may be controlled by an external magnetic field, can be used to map out the detailed magnetic configuration of an itinerant system and distinguish unambiguously between single-Q and multi-Q phases. We demonstrate this concept bymore » computing and contrasting the LDOS near a magnetic impurity embedded in three different magnetic ground states relevant to iron-based superconductors—one single-Q and two double-Q phases. Our results open a promising avenue to investigate the complex magnetic configurations in itinerant systems via standard scanning tunnelling spectroscopy, without requiring spin-resolved capability.« less

  11. Scanning tunnelling spectroscopy as a probe of multi-Q magnetic states of itinerant magnets.

    PubMed

    Gastiasoro, Maria N; Eremin, Ilya; Fernandes, Rafael M; Andersen, Brian M

    2017-02-08

    The combination of electronic correlations and Fermi surfaces with multiple nesting vectors can lead to the appearance of complex multi-Q magnetic ground states, hosting unusual states such as chiral density waves and quantum Hall insulators. Distinguishing single-Q and multi-Q magnetic phases is however a notoriously difficult experimental problem. Here we propose theoretically that the local density of states (LDOS) near a magnetic impurity, whose orientation may be controlled by an external magnetic field, can be used to map out the detailed magnetic configuration of an itinerant system and distinguish unambiguously between single-Q and multi-Q phases. We demonstrate this concept by computing and contrasting the LDOS near a magnetic impurity embedded in three different magnetic ground states relevant to iron-based superconductors-one single-Q and two double-Q phases. Our results open a promising avenue to investigate the complex magnetic configurations in itinerant systems via standard scanning tunnelling spectroscopy, without requiring spin-resolved capability.

  12. Scanning tunnelling spectroscopy as a probe of multi-Q magnetic states of itinerant magnets

    NASA Astrophysics Data System (ADS)

    Gastiasoro, Maria N.; Eremin, Ilya; Fernandes, Rafael M.; Andersen, Brian M.

    2017-02-01

    The combination of electronic correlations and Fermi surfaces with multiple nesting vectors can lead to the appearance of complex multi-Q magnetic ground states, hosting unusual states such as chiral density waves and quantum Hall insulators. Distinguishing single-Q and multi-Q magnetic phases is however a notoriously difficult experimental problem. Here we propose theoretically that the local density of states (LDOS) near a magnetic impurity, whose orientation may be controlled by an external magnetic field, can be used to map out the detailed magnetic configuration of an itinerant system and distinguish unambiguously between single-Q and multi-Q phases. We demonstrate this concept by computing and contrasting the LDOS near a magnetic impurity embedded in three different magnetic ground states relevant to iron-based superconductors--one single-Q and two double-Q phases. Our results open a promising avenue to investigate the complex magnetic configurations in itinerant systems via standard scanning tunnelling spectroscopy, without requiring spin-resolved capability.

  13. Scanning tunnelling spectroscopy as a probe of multi-Q magnetic states of itinerant magnets

    PubMed Central

    Gastiasoro, Maria N.; Eremin, Ilya; Fernandes, Rafael M.; Andersen, Brian M.

    2017-01-01

    The combination of electronic correlations and Fermi surfaces with multiple nesting vectors can lead to the appearance of complex multi-Q magnetic ground states, hosting unusual states such as chiral density waves and quantum Hall insulators. Distinguishing single-Q and multi-Q magnetic phases is however a notoriously difficult experimental problem. Here we propose theoretically that the local density of states (LDOS) near a magnetic impurity, whose orientation may be controlled by an external magnetic field, can be used to map out the detailed magnetic configuration of an itinerant system and distinguish unambiguously between single-Q and multi-Q phases. We demonstrate this concept by computing and contrasting the LDOS near a magnetic impurity embedded in three different magnetic ground states relevant to iron-based superconductors—one single-Q and two double-Q phases. Our results open a promising avenue to investigate the complex magnetic configurations in itinerant systems via standard scanning tunnelling spectroscopy, without requiring spin-resolved capability. PMID:28176779

  14. A scanning Hall probe microscope for high resolution, large area, variable height magnetic field imaging.

    PubMed

    Shaw, Gorky; Kramer, R B G; Dempsey, N M; Hasselbach, K

    2016-11-01

    We present a scanning Hall probe microscope operating in ambient conditions. One of the unique features of this microscope is the use of the same stepper motors for both sample positioning as well as scanning, which makes it possible to have a large scan range (few mm) in the x and y directions, with a scan resolution of 0.1 μm. Protocols have been implemented to enable scanning at different heights from the sample surface. The z range is 35 mm. Microstructured Hall probes of size 1-5 μm have been developed. A minimum probe-sample distance <2 μm has been obtained by the combination of new Hall probes and probe-sample distance regulation using a tuning fork based force detection technique. The system is also capable of recording local B(z) profiles. We discuss the application of the microscope for the study of micro-magnet arrays being developed for applications in micro-systems.

  15. A scanning Hall probe microscope for high resolution, large area, variable height magnetic field imaging

    NASA Astrophysics Data System (ADS)

    Shaw, Gorky; Kramer, R. B. G.; Dempsey, N. M.; Hasselbach, K.

    2016-11-01

    We present a scanning Hall probe microscope operating in ambient conditions. One of the unique features of this microscope is the use of the same stepper motors for both sample positioning as well as scanning, which makes it possible to have a large scan range (few mm) in the x and y directions, with a scan resolution of 0.1 μm. Protocols have been implemented to enable scanning at different heights from the sample surface. The z range is 35 mm. Microstructured Hall probes of size 1-5 μm have been developed. A minimum probe-sample distance <2 μm has been obtained by the combination of new Hall probes and probe-sample distance regulation using a tuning fork based force detection technique. The system is also capable of recording local B(z) profiles. We discuss the application of the microscope for the study of micro-magnet arrays being developed for applications in micro-systems.

  16. [Application of superparamagnetic iron oxide labeled antisense oligodeoxynucleotide probe in cellular magnetic resonance imaging].

    PubMed

    Wen, Ming; Li, Bi-Bo; Ouyang, Yu; Jiang, Ming-Dong; Luo, Yi; Li, Shao-Lin

    2008-10-01

    To prepare the superparamagnetic iron oxide (SPIO)-labeled antisense oligodeoxynucleotide (ASODN) probe and evaluate the application of this probe in cellular magnetic resonance imaging (MRI). We prepared the SPIO-labeled ASODN probe using chemical cross linking method to conjugate SPIO to ASODN, detected its configuration by atomic force microscopy, determined the conjugating rate and biology activation by high performance liquid chromatography, and detected the stability by polyacrylamide gel electrophoresis. After that, we transfected the SK-Br3 oncocytes which had over-expression of the c-erbB2 oncogene by this probes, observed the intracellular iron distribution by optical microscope, measured iron content by atomic absorption spectroscopy, and observed the signal change by MRI. Atomic force microscope showed that the SPIO-labeled ASODN probe was mostly spherical and well-distributed, with a diameter of 25-40 nm and a conjugating rate of 100%. This probe had inhered biological activity and stability. In addition, light microscopy revealed an intracellular uptake of iron oxides in the transfected SK-Br3 oncocyte, and the iron content of the group of transfected SK-Br3 oncocytes was significantly higher than those of other contrast groups (all P < 0.01). MRI showed that transfected SK-Br3 oncocyte had the lowest signal among all other cells (all P < 0.05). We prepared the SPIO-labeled ASODN probe successfully. It can effectively transfect SK-Br3 oncocyte and enter SK-Br3 oncocyte, and thus reduce the signal intension in MRI.

  17. Zeeman Effect in Sulfur Monoxide: a Probe to Observe Magnetic Fields in Star Forming Regions?

    NASA Astrophysics Data System (ADS)

    Cazzoli, Gabriele; Lattanzi, Valerio; Coriani, Sonia; Gauss, Jürgen; Codella, Claudio; Ramos, Andrés Asensio; Cernicharo, Jose; Puzzarini, Cristina

    2017-06-01

    Magnetic fields play a fundamental role in star formation processes and the best method to evaluate their intensity is is to measure the Zeeman effect of atomic and molecular lines. However, a direct measurement of the Zeeman spectral pattern from interstellar molecular species is challenging due to the high sensitivity and high spectral resolution required. So far, the Zeeman effect has been detected unambiguously in star forming regions for very few non-masing species, such as OH and CN. We decided to investigate the ability of sulfur monoxide (SO), which is one of the most abundant species in star forming regions, for probing the intensity of magnetic fields via Zeeman effect. The Zeeman effect for several rotational transitions of SO in the (sub-)mm spectral regions has been investigated by using a frequency-modulated, computer-controlled spectrometer, and by applying a magnetic field parallel to the radiation source. To support the experimental determination of the g factors of SO, a systematic quantum-chemical investigation of these parameters for both SO and O_2 has been carried out. An effective experimental-computational strategy for providing accurate g factors as well as for identifying the rotational transitions showing the strongest Zeeman effect has been presented. Our investigation supports SO as a good candidate for probing magnetic fields in high-density star forming regions.

  18. Capacitive probing of plasma and surface potentials in a magnetically enhanced rf discharge

    NASA Astrophysics Data System (ADS)

    Savas, S. E.; Donohoe, K. G.

    1989-07-01

    A capacitive probe is used in a magnetically enhanced rf discharge to measure spatial and parametric dependences of the amplitude of the rf fundamental of the plasma and electrode potentials. The probe has a metal `paddle tip that can be either immersed in the plasma or positioned flat on the exposed surface. The magnetically enhanced discharge uses capacitive coupled power at 13.56 MHz in the range of 1 M/cm2 to 3 W/cm2; N2 pressure in the range between 10 mTorr and 125 mTorr, and magnetic field up to 100 Gauss. The rf amplitude of the plasma potential is found to have a large gradient within the electrode sheath (≳1000 V/cm) and small variation (<10 V/cm) in the glow region. The variation along B in the glow is found to be much smaller than that perpendicular to B. The magnitude of the gradient perpendiular to B increases with both gas pressure and magnetic field strength, consistent with our simple plasma current model.

  19. Probing transverse magnetic anisotropy by electronic transport through a single-molecule magnet

    NASA Astrophysics Data System (ADS)

    Misiorny, M.; Burzurí, E.; Gaudenzi, R.; Park, K.; Leijnse, M.; Wegewijs, M. R.; Paaske, J.; Cornia, A.; van der Zant, H. S. J.

    2015-01-01

    By means of electronic transport, we study the transverse magnetic anisotropy of an individual Fe4 single-molecule magnet (SMM) embedded in a three-terminal junction. In particular, we determine in situ the transverse anisotropy of the molecule from the pronounced intensity modulations of the linear conductance, which are observed as a function of applied magnetic field. The proposed technique works at temperatures exceeding the energy scale of the tunnel splittings of the SMM. We deduce that the transverse anisotropy for a single Fe4 molecule captured in a junction is substantially larger than the bulk value.

  20. Can We Probe the Conductivity of the Lithosphere and Upper Mantle Using Satellite Tidal Magnetic Signals?

    NASA Technical Reports Server (NTRS)

    Schnepf, N. R.; Kuvshinov, A.; Sabaka, T.

    2015-01-01

    A few studies convincingly demonstrated that the magnetic fields induced by the lunar semidiurnal (M2) ocean flow can be identified in satellite observations. This result encourages using M2 satellite magnetic data to constrain subsurface electrical conductivity in oceanic regions. Traditional satellite-based induction studies using signals of magnetospheric origin are mostly sensitive to conducting structures because of the inductive coupling between primary and induced sources. In contrast, galvanic coupling from the oceanic tidal signal allows for studying less conductive, shallower structures. We perform global 3-D electromagnetic numerical simulations to investigate the sensitivity of M2 signals to conductivity distributions at different depths. The results of our sensitivity analysis suggest it will be promising to use M2 oceanic signals detected at satellite altitude for probing lithospheric and upper mantle conductivity. Our simulations also suggest that M2 seafloor electric and magnetic field data may provide complementary details to better constrain lithospheric conductivity.

  1. Quantum probe and design for a chemical compass with magnetic nanostructures.

    PubMed

    Cai, Jianming

    2011-03-11

    Magnetic fields as weak as Earth's may affect the outcome of certain photochemical reactions that go through a radical pair intermediate. When the reaction environment is anisotropic, this phenomenon can form the basis of a chemical compass and has been proposed as a mechanism for animal magnetoreception. Here, we demonstrate how to optimize the design of a chemical compass with a much better directional sensitivity simply by a gradient field, e.g., from a magnetic nanostructure. We propose an experimental test of these predictions, and suggest design principles for a hybrid metallic-organic chemical compass. In addition to the practical interest in designing a biomimetic weak magnetic field sensor, our result shows that gradient fields can serve as powerful tools to probe spin correlations in radical pair reactions.

  2. Quantum Probe and Design for a Chemical Compass with Magnetic Nanostructures

    NASA Astrophysics Data System (ADS)

    Cai, Jianming

    2011-03-01

    Magnetic fields as weak as Earth’s may affect the outcome of certain photochemical reactions that go through a radical pair intermediate. When the reaction environment is anisotropic, this phenomenon can form the basis of a chemical compass and has been proposed as a mechanism for animal magnetoreception. Here, we demonstrate how to optimize the design of a chemical compass with a much better directional sensitivity simply by a gradient field, e.g., from a magnetic nanostructure. We propose an experimental test of these predictions, and suggest design principles for a hybrid metallic-organic chemical compass. In addition to the practical interest in designing a biomimetic weak magnetic field sensor, our result shows that gradient fields can serve as powerful tools to probe spin correlations in radical pair reactions.

  3. Wash-free magnetic oligonucleotide probes-based NMR sensor for detecting the Hg ion.

    PubMed

    Ma, Wenwei; Hao, Changlong; Ma, Wei; Xing, Changrui; Yan, Wenjing; Kuang, Hua; Wang, Libing; Xu, Chuanlai

    2011-12-14

    An easily applied and sensitive sensor for the detection of heavy metal ion residues based entirely on magnetic nanoparticle and oligonucleotide was developed. The tool is established on the relaxation of magnetic nanoparticles with different dispersion states. The target analyte, Hg ions, induce the aggregation of the MNP oligonucleotide probes. Accordingly, the light produced by the magnetic relaxation image and the transverse relaxation time (T(2)) all change due to the effect of the aggregation. The limit of qualitative detection of the sensor is 0.15 ppt. The recoveries from test samples range between 97.1-101.8%. Using the nuclear resonance instrument, the method is a high throughput and sensitive sensor.

  4. Can We Probe the Conductivity of the Lithosphere and Upper Mantle Using Satellite Tidal Magnetic Signals?

    NASA Technical Reports Server (NTRS)

    Schnepf, N. R.; Kuvshinov, A.; Sabaka, T.

    2015-01-01

    A few studies convincingly demonstrated that the magnetic fields induced by the lunar semidiurnal (M2) ocean flow can be identified in satellite observations. This result encourages using M2 satellite magnetic data to constrain subsurface electrical conductivity in oceanic regions. Traditional satellite-based induction studies using signals of magnetospheric origin are mostly sensitive to conducting structures because of the inductive coupling between primary and induced sources. In contrast, galvanic coupling from the oceanic tidal signal allows for studying less conductive, shallower structures. We perform global 3-D electromagnetic numerical simulations to investigate the sensitivity of M2 signals to conductivity distributions at different depths. The results of our sensitivity analysis suggest it will be promising to use M2 oceanic signals detected at satellite altitude for probing lithospheric and upper mantle conductivity. Our simulations also suggest that M2 seafloor electric and magnetic field data may provide complementary details to better constrain lithospheric conductivity.

  5. Parametric Harmonic Generation as a Probe of Unconstrained Spin Magnetization Precession in the Shallow Barrier Limit.

    PubMed

    Capua, Amir; Rettner, Charles; Parkin, Stuart S P

    2016-01-29

    We study the parametric excitation of high orders of magnetization precession in ultrathin films having perpendicular magnetic anisotropy. We observe that for a given driving field amplitude the harmonic generation can be increased by lowering the barrier with the application of an in-plane magnetic field in the manner of the Smit-Beljers effect. In this effect, the magnetic stiffness is reduced not by lowering the magnitude of the magnetic field upon which the spins precess, but rather by effectively releasing the field's "anchoring" point. This results in a shallow energy barrier where the electrons' spin is locally unconstrained. While the observation is unveiled in the form of nonlinear high harmonic generation, we believe that the physics whereby the barrier is suppressed by an external magnetic field may apply to other phenomena associated with ultrathin films. In these cases, such unconstrained motion may serve as a sensitive probe of the torques associated with proximate spin currents. Moreover, our approach may be used as a model system for the study of phase transitions in the field of nonlinear dynamics.

  6. Scanned probe imaging of nanoscale magnetism at cryogenic temperatures with a single-spin quantum sensor.

    PubMed

    Pelliccione, Matthew; Jenkins, Alec; Ovartchaiyapong, Preeti; Reetz, Christopher; Emmanouilidou, Eve; Ni, Ni; Bleszynski Jayich, Ania C

    2016-08-01

    High-spatial-resolution magnetic imaging has driven important developments in fields ranging from materials science to biology. However, to uncover finer details approaching the nanoscale with greater sensitivity requires the development of a radically new sensor technology. The nitrogen-vacancy (NV) defect in diamond has emerged as a promising candidate for such a sensor on the basis of its atomic size and quantum-limited sensing capabilities. It has remained an outstanding challenge to implement the NV centre as a nanoscale scanning magnetic probe at cryogenic temperatures, however, where many solid-state systems exhibit non-trivial magnetic order. Here, we present NV magnetic imaging down to 6 K with 3 μT Hz(-1/2) field sensitivity, and use the technique to image vortices in the iron pnictide superconductor BaFe2(As0.7P0.3)2 with critical temperature Tc = 30 K. The expansion of NV-based magnetic imaging to cryogenic temperatures will enable future studies of previously inaccessible nanoscale magnetism in condensed-matter systems.

  7. Scanning Hall probe microscopy of magnetic vortices in very underdoped yttrium-barium-copper-oxide

    NASA Astrophysics Data System (ADS)

    Guikema, Janice Wynn

    Since their discovery by Bednorz and Muller in 1986, high-temperature cuprate superconductors have been the subject of intense research. Despite this effort, agreement on the mechanism of high- Tc has not been reached. Many theories make their strongest predictions for underdoped superconductors with very low superfluid density ns/m*. I implemented a scanning Hall probe microscope (SHPM) and used it to study magnetic vortices in newly available single crystals of very underdoped YBa2Cu3O6+x . These studies have disproved a promising theory of spin-charge separation, measured the apparent vortex size (an upper bound on the penetration depth lambda ab), and revealed an intriguing phenomenon of "split" vortices. SHPM is a non-invasive and direct method for magnetic field imaging. It is one of the few techniques capable of submicron spatial resolution coupled with sub-phi0 (flux quantum) sensitivity, and it operates over a wide temperature range. Chapter 2 introduces the variable temperature scanning microscope and discusses the scanning Hall probe set-up and scanner characterizations. Chapter 3 details my fabrication of submicron GaAs/AlGaAs Hall probes and discusses noise studies for a range of probe sizes, which suggest that sub-100 nm probes could be made without compromising flux sensitivity. The subsequent chapters detail SHPM (and SQUID) studies of very underdoped YBa2Cu3O6+x crystals with T c ≤ 15 K. Chapter 4 describes two experimental tests for visons, essential excitations of a spin-charge separation theory proposed by Senthil and Fisher. We searched for predicted hc/ e vortices and a vortex memory effect with null results, placing upper bounds on the vison energy inconsistent with the theory. Chapter 5 discusses imaging of isolated vortices as a function of Tc. Vortex images were fit with theoretical magnetic field profiles in order to extract the apparent vortex size. The data for the lowest Tc 's (5 and 6.5 K) show some inhomogeneity and suggest that

  8. Transforming thymidine into a magnetic resonance imaging probe for monitoring gene expression.

    PubMed

    Bar-Shir, Amnon; Liu, Guanshu; Liang, Yajie; Yadav, Nirbhay N; McMahon, Michael T; Walczak, Piotr; Nimmagadda, Sridhar; Pomper, Martin G; Tallman, Keri A; Greenberg, Marc M; van Zijl, Peter C M; Bulte, Jeff W M; Gilad, Assaf A

    2013-01-30

    Synthetic chemistry has revolutionized the understanding of many biological systems. Small compounds that act as agonists and antagonists of proteins, and occasionally as imaging probes, have contributed tremendously to the elucidation of many biological pathways. Nevertheless, the function of thousands of proteins is still elusive, and designing new imaging probes remains a challenge. Through screening and characterization, we identified a thymidine analogue as a probe for imaging the expression of herpes simplex virus type-1 thymidine kinase (HSV1-TK). To detect the probe, we used chemical exchange saturation transfer magnetic resonance imaging (CEST-MRI), in which a dynamic exchange process between an exchangeable proton and the surrounding water protons is used to amplify the desired contrast. Initially, five pyrimidine-based molecules were recognized as putative imaging agents, since their exchangeable imino protons resonate at 5-6 ppm from the water proton frequency and their detection is therefore less affected by endogenous CEST contrast or confounded by direct water saturation. Increasing the pK(a) value of the imino proton by reduction of its 5,6-double bond results in a significant reduction of the exchange rate (k(ex)) between this proton and the water protons. This reduced k(ex) of the dihydropyrimidine nucleosides fulfills the "slow to intermediate regime" condition for generating high CEST-MRI contrast. Consequently, we identified 5-methyl-5,6-dihydrothymidine as the optimal probe and demonstrated its feasibility for in vivo imaging of HSV1-TK. In light of these findings, this new approach can be generalized for designing specific probes for the in vivo imaging of a variety of proteins and enzymes.

  9. Magnetic probe measurements of the current sheath on the PF-3 facility

    SciTech Connect

    Krauz, V. I.; Mitrofanov, K. N.; Myalton, V. V.; Vinogradov, V. P.; Vinogradova, Yu. V.; Grabovski, E. V.; Zukakishvili, G. G.; Koidan, V. S.; Mokeev, A. N.

    2010-11-15

    Results are presented from experimental studies of the dynamics of the current sheath (CS) on the PF-3 plasma focus facility. The parameters of the sheath, including the current distribution in it, were measured using absolutely calibrated magnetic probes installed at different positions with respect to the facility axis and the anode surface. The CS dynamics in discharges operating in argon and neon was investigated, and the skin depth in different stages of the discharge was determined. One of the probes was installed at a distance of {approx}2 cm from the facility axis, which made it possible to estimate the efficiency of current transfer to the region of pinch formation. Operating modes were obtained in which the current dynamics detected by magnetic probes at different distances from the axis agreed well with the dynamics of the total discharge current until the instant of singularity in the current time derivative. It is shown that shunting breakdowns can lead to the formation of closed current loops. The shunting of the discharge current by the residual plasma is directly related to the efficiency of snowplowing of the working gas by the CS as it propagates from the insulator toward the facility axis.

  10. High torque CMG rotary actuator

    NASA Technical Reports Server (NTRS)

    1972-01-01

    A high torque rotary actuator was designed, fabricated and tested. Exacting requirements were placed on performance and physical characteristics of the actuator, particularly in the area of stiffness, backlash, torque ripple, power and size and weight. A brushless dc motor was designed utilizing rare earth magnets to meet power and weight requirements. A 26-to-1 planetary roller gear transmission was selected to best meet overall requirements. The transmission utilizes parallel gear and roller paths to minimize backlash and breakaway torque.

  11. Shape Memory Actuator System

    DTIC Science & Technology

    1998-07-31

    The advantage in utilizing 15 shape-memory cables made of Nitinol for size reduction of the remote control actuator system is 1 Fi well suited for...a submarine environment because of its non-magnetic and corrosion resistance 17 properties. Use of thermoelastic Nitinol introduces other...problems because of the cooling and 18 resetting properties of Nitinol cables. It is therefore an important object of the present invention 19 on to

  12. Magnetically insulated baffled probe for real-time monitoring of equilibrium and fluctuating values of space potentials, electron and ion temperatures, and densities

    SciTech Connect

    Demidov, V. I.; Koepke, M. E.; Raitses, Y.

    2010-10-15

    By restricting the electron-collection area of a cold Langmuir probe compared to the ion-collection area, the probe floating potential can become equal to the space potential, and thus conveniently monitored, rather than to a value shifted from the space potential by an electron-temperature-dependent offset, i.e., the case with an equal-collection-area probe. This design goal is achieved by combining an ambient magnetic field in the plasma with baffles, or shields, on the probe, resulting in species-selective magnetic insulation of the probe collection area. This permits the elimination of electron current to the probe by further adjustment of magnetic insulation which results in an ion-temperature-dependent offset when the probe is electrically floating. Subtracting the floating potential of two magnetically insulated baffled probes, each with a different degree of magnetic insulation, enables the electron or ion temperature to be measured in real time.

  13. Magnetically insulated baffled probe for real-time monitoring of equilibrium and fluctuating values of space potentials, electron and ion temperatures, and densities.

    PubMed

    Demidov, V I; Koepke, M E; Raitses, Y

    2010-10-01

    By restricting the electron-collection area of a cold Langmuir probe compared to the ion-collection area, the probe floating potential can become equal to the space potential, and thus conveniently monitored, rather than to a value shifted from the space potential by an electron-temperature-dependent offset, i.e., the case with an equal-collection-area probe. This design goal is achieved by combining an ambient magnetic field in the plasma with baffles, or shields, on the probe, resulting in species-selective magnetic insulation of the probe collection area. This permits the elimination of electron current to the probe by further adjustment of magnetic insulation which results in an ion-temperature-dependent offset when the probe is electrically floating. Subtracting the floating potential of two magnetically insulated baffled probes, each with a different degree of magnetic insulation, enables the electron or ion temperature to be measured in real time.

  14. Simultaneous poloidal measurements using new magnetically driven reciprocating probes in COMPASS

    NASA Astrophysics Data System (ADS)

    Dejarnac, R.; Gunn, J. P.; Dimitrova, M.; Hron, M.; Panek, R.; Pascal, J.-Y.; Saragosti-Chausy, C.; Tamain, P.; the COMPASS Team

    2016-03-01

    Particles and heat transport in the scrape-off layer (SOL) of tokamaks is not yet fully understood. COMPASS is a small-size tokamakp where the edge plasma is well diagnosed in view of studying the competition between the parallel and the cross-field transport in the SOL. In order to better characterize SOL dynamics, in particular the poloidal asymmetry of the main parameters' radial profiles, two new in-situ magnetically driven reciprocating manipulators have been recently installed in COMPASS. These manipulators, the so-called pecker probes, are two additional poloidal measurement points to the existing two (vertical and horizontal) reciprocating manipulators. The pecker probes are located at the low field side of COMPASS at ±47.5o with respect to the outer mid-plane and are equipped with identical tunnel probe heads, providing simultaneous measurements of the ion saturation current density Jsat, the electron temperature Te and the parallel Mach number M// with high temporal resolution. In this paper, a detailed description of the pecker probe system in COMPASS is described and first measurements are presented.

  15. Dual-Modal Magnetic Resonance/Fluorescent Zinc Probes for Pancreatic β-Cell Mass Imaging

    PubMed Central

    Stasiuk, Graeme J; Minuzzi, Florencia; Sae-Heng, Myra; Rivas, Charlotte; Juretschke, Hans-Paul; Piemonti, Lorenzo; Allegrini, Peter R; Laurent, Didier; Duckworth, Andrew R; Beeby, Andrew; Rutter, Guy A; Long, Nicholas J

    2015-01-01

    Despite the contribution of changes in pancreatic β-cell mass to the development of all forms of diabetes mellitus, few robust approaches currently exist to monitor these changes prospectively in vivo. Although magnetic-resonance imaging (MRI) provides a potentially useful technique, targeting MRI-active probes to the β cell has proved challenging. Zinc ions are highly concentrated in the secretory granule, but they are relatively less abundant in the exocrine pancreas and in other tissues. We have therefore developed functional dual-modal probes based on transition-metal chelates capable of binding zinc. The first of these, Gd⋅1, binds ZnII directly by means of an amidoquinoline moiety (AQA), thus causing a large ratiometric Stokes shift in the fluorescence from λem=410 to 500 nm with an increase in relaxivity from r1=4.2 up to 4.9 mM−1 s−1. The probe is efficiently accumulated into secretory granules in β-cell-derived lines and isolated islets, but more poorly by non-endocrine cells, and leads to a reduction in T1 in human islets. In vivo murine studies of Gd⋅1 have shown accumulation of the probe in the pancreas with increased signal intensity over 140 minutes. PMID:25736590

  16. Probe imaging studies of magnetic susceptibility and permeability for sensitive characterisation of carbonate reservoir rocks

    NASA Astrophysics Data System (ADS)

    Ivakhnenko, Aleksandr; Bigaliyeva, Akmaral; Dubinin, Vladislav

    2016-04-01

    In this study were disclosed the main principals of identifying petrophysical properties of carbonate reservoirs such as porosity, permeability and magnetic susceptibility. While exploring and developing reservoir there are significant diversity of tasks that can be solved by appropriate knowledge of properties which are listed above. Behavior of fluid flow, distribution of hydrocarbons and other various industrial applications can be solved by measuring areal distribution of these petrophysical parameters. The results demonstrate how magnetic probe and hysteresis measurements correlate with petrophysical parameters in carbonate reservoirs. We made experimental measurements and theoretical calculations of how much magnetic susceptibility depends on the porosity of the rocks and analyzed data with graphics. In theoretical model of the carbonate rocks we considered calcite, dolomite, quartz and combinations of calcite and dolomite, calcite and Fe-dolomite, calcite and quartz, calcite and aragonite with increasing concentrations of the dolomite, Fe-dolomite, quartz and aragonite up to 50% with step of 5%. Here we defined dependence of magnetic susceptibility from the porosity: the higher porosity measurements, the less slope of magnetic susceptibility, consequently mass magnetization is higher for diamagnetic and lower for paramagnetic carbonate rocks, but in the both cases magnetic susceptibility tries to reach zero with increasing of the total porosity. Rock measurements demonstrate that reservoir zones of the low diamagnetic magnetic susceptibility are generally correlated with higher permeability and also porosity distribution. However for different carbonate reservoirs we establish different relationships depending on the complexity of their mineralogy and texture. Application of integral understanding in distribution of permeability, porosity and mineral content in heterogeneous carbonates represented by this approach can be useful tool for carbonate reservoir

  17. Probing the magnetic profile of diluted magnetic semiconductors using polarized neutron reflectivity.

    PubMed

    Luo, X; Tseng, L T; Lee, W T; Tan, T T; Bao, N N; Liu, R; Ding, J; Li, S; Lauter, V; Yi, J B

    2017-07-24

    Room temperature ferromagnetism has been observed in the Cu doped ZnO films deposited under an oxygen partial pressure of 10(-3) and 10(-5) torr on Pt (200 nm)/Ti (45 nm)/Si (001) substrates using pulsed laser deposition. Due to the deposition at relatively high temperature (873 K), Cu and Ti atoms diffuse to the surface and interface, which significantly affects the magnetic properties. Depth sensitive polarized neutron reflectometry method provides the details of the composition and magnetization profiles and shows that an accumulation of Cu on the surface leads to an increase in the magnetization near the surface. Our results reveal that the presence of the copper at Zn sites induces ferromagnetism at room temperature, confirming intrinsic ferromagnetism.

  18. Large Scale Magnetostrictive Valve Actuator

    NASA Technical Reports Server (NTRS)

    Richard, James A.; Holleman, Elizabeth; Eddleman, David

    2008-01-01

    Marshall Space Flight Center's Valves, Actuators and Ducts Design and Development Branch developed a large scale magnetostrictive valve actuator. The potential advantages of this technology are faster, more efficient valve actuators that consume less power and provide precise position control and deliver higher flow rates than conventional solenoid valves. Magnetostrictive materials change dimensions when a magnetic field is applied; this property is referred to as magnetostriction. Magnetostriction is caused by the alignment of the magnetic domains in the material s crystalline structure and the applied magnetic field lines. Typically, the material changes shape by elongating in the axial direction and constricting in the radial direction, resulting in no net change in volume. All hardware and testing is complete. This paper will discuss: the potential applications of the technology; overview of the as built actuator design; discuss problems that were uncovered during the development testing; review test data and evaluate weaknesses of the design; and discuss areas for improvement for future work. This actuator holds promises of a low power, high load, proportionally controlled actuator for valves requiring 440 to 1500 newtons load.

  19. Advances in Langmuir probe diagnostics of the plasma potential and electron-energy distribution function in magnetized plasma

    NASA Astrophysics Data System (ADS)

    Popov, Tsv K.; Dimitrova, M.; Ivanova, P.; Kovačič, J.; Gyergyek, T.; Dejarnac, R.; Stöckel, J.; Pedrosa, M. A.; López-Bruna, D.; Hidalgo, C.

    2016-06-01

    Advanced Langmuir probe techniques for evaluating the plasma potential and electron-energy distribution function (EEDF) in magnetized plasma are reviewed. It is shown that when the magnetic field applied is very weak and the electrons reach the probe without collisions in the probe sheath the second-derivative Druyvesteyn formula can be used for EEDF evaluation. At low values of the magnetic field, an extended second-derivative Druyvesteyn formula yields reliable results, while at higher values of the magnetic field, the first-derivative probe technique is applicable for precise evaluation of the plasma potential and the EEDF. There is an interval of intermediate values of the magnetic field when both techniques—the extended second-derivative and the first-derivative one—can be used. Experimental results from probe measurements in different ranges of magnetic field are reviewed and discussed: low-pressure argon gas discharges in the presence of a magnetic field in the range from 0.01 to 0.08 T, probe measurements in circular hydrogen plasmas for high-temperature fusion (magnetic fields from 0.45 T to 1.3 T) in small ISTTOK and CASTOR tokamaks, D-shape COMPASS tokamak plasmas, as well as in the TJ-II stellarator. In the vicinity of the last closed flux surface (LCFS) in tokamaks and in the TJ-II stellarator, the EEDF obtained is found to be bi-Maxwellian, while close to the tokamak chamber wall it is Maxwellian. The mechanism of the appearance of a bi-Maxwellian EEDF in the vicinity of the LCFS is discussed. Comparison of the results from probe measurements with those obtained from calculations using the ASTRA and EIRENE codes shows that the main reason for the appearance of a bi-Maxwellian EEDF in the vicinity of the LCFS is the ionization of the neutral atoms.

  20. Dual-Color Fluorescence Imaging of Magnetic Nanoparticles in Live Cancer Cells Using Conjugated Polymer Probes.

    PubMed

    Sun, Minjie; Sun, Bin; Liu, Yun; Shen, Qun-Dong; Jiang, Shaojun

    2016-03-02

    Rapid growth in biological applications of nanomaterials brings about pressing needs for exploring nanomaterial-cell interactions. Cationic blue-emissive and anionic green-emissive conjugated polymers are applied as dual-color fluorescence probes to the surface of negatively charged magnetic nanoparticles through sequentially electrostatic adsorption. These conjugated polymers have large extinction coefficients and high fluorescence quantum yield (82% for PFN and 62% for ThPFS). Thereby, one can visualize trace amount (2.7 μg/mL) of fluorescence-labeled nanoparticles within cancer cells by confocal laser scanning microscopy. Fluorescence labeling by the conjugated polymers is also validated for quantitative determination of the internalized nanoparticles in each individual cell by flow cytometry analysis. Extensive overlap of blue and green fluorescence signals in the cytoplasm indicates that both conjugated polymer probes tightly bind to the surface of the nanoparticles during cellular internalization. The highly charged and fluorescence-labeled nanoparticles non-specifically bind to the cell membranes, followed by cellular uptake through endocytosis. The nanoparticles form aggregates inside endosomes, which yields a punctuated staining pattern. Cellular internalization of the nanoparticles is dependent on the dosage and time. Uptake efficiency can be enhanced three-fold by application of an external magnetic field. The nanoparticles are low cytotoxicity and suitable for simultaneously noninvasive fluorescence and magnetic resonance imaging application.

  1. Dual-Color Fluorescence Imaging of Magnetic Nanoparticles in Live Cancer Cells Using Conjugated Polymer Probes

    PubMed Central

    Sun, Minjie; Sun, Bin; Liu, Yun; Shen, Qun-Dong; Jiang, Shaojun

    2016-01-01

    Rapid growth in biological applications of nanomaterials brings about pressing needs for exploring nanomaterial-cell interactions. Cationic blue-emissive and anionic green-emissive conjugated polymers are applied as dual-color fluorescence probes to the surface of negatively charged magnetic nanoparticles through sequentially electrostatic adsorption. These conjugated polymers have large extinction coefficients and high fluorescence quantum yield (82% for PFN and 62% for ThPFS). Thereby, one can visualize trace amount (2.7 μg/mL) of fluorescence-labeled nanoparticles within cancer cells by confocal laser scanning microscopy. Fluorescence labeling by the conjugated polymers is also validated for quantitative determination of the internalized nanoparticles in each individual cell by flow cytometry analysis. Extensive overlap of blue and green fluorescence signals in the cytoplasm indicates that both conjugated polymer probes tightly bind to the surface of the nanoparticles during cellular internalization. The highly charged and fluorescence-labeled nanoparticles non-specifically bind to the cell membranes, followed by cellular uptake through endocytosis. The nanoparticles form aggregates inside endosomes, which yields a punctuated staining pattern. Cellular internalization of the nanoparticles is dependent on the dosage and time. Uptake efficiency can be enhanced three-fold by application of an external magnetic field. The nanoparticles are low cytotoxicity and suitable for simultaneously noninvasive fluorescence and magnetic resonance imaging application. PMID:26931282

  2. Scanning probe microscopy: instrumentation and applications on thin films and magnetic multilayers.

    PubMed

    Karoutsos, Vagelis

    2009-12-01

    In this article we present a review on instrumentation and the modes of operation of a scanning probe microscope. In detail, we review the main techniques of Scanning Probe Microscopy (SPM), which are Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM), focusing our attention on the latter one. The AFM instrument provides information on the roughness and grain size of thin films. As an example we review recent results on two metallic thin film systems: thin Ag films deposited on glass, and Ni/Pt compositionally modulated multilayers deposited on glass, Si, and polyimide substrates. To show the validity of the grain size measurements, we compare the data with the ones resulting from X-ray diffraction (XRD) measurements. We show that the AFM results are reliable for grain diameters as small as 14 nm, which is approximately comparable to the tip radius. Finally, we deal with Magnetic Force Microscopy (MFM) results on Co/Pt and Co/Au multilayers. We observe perpendicularly magnetized domains. The domain configurations are correlated to the magnetization hysteresis curves.

  3. Dynamics of positive probes in underdense, strongly magnetized, E×B drifting plasma: Particle-in-cell simulations

    SciTech Connect

    Heinrich, Jonathon R.; Cooke, David L.

    2013-09-15

    Electron trapping, electron heating, space-charge wings, wake eddies, and current collection by a positive probe in E×B drifting plasma were studied in three-dimensional electromagnetic particle-in-cell simulations. In these simulations, electrons and ions were magnetized with respect to the probe and the plasma was underdense (ω{sub pe}<ω{sub ce}). A large drift velocity (Mach 4.5 with respect to the ion acoustic speed) between the plasma and probe was created with background electric and magnetic fields. Four distinct regions developed in the presences of the positive probe: a quasi-trapped electron region, an electron-depletion wing, an ion-rich wing, and a wake region. We report on the observations of strong electron heating mechanisms, space-charge wings, ion cyclotron charge-density eddies in the wake, electron acceleration due to a magnetic presheath, and the current-voltage relationship.

  4. Polarized Radiation Observables for Probing the Magnetism of the Outer Solar Atmosphere

    NASA Astrophysics Data System (ADS)

    Trujillo Bueno, J.

    2014-10-01

    The basic idea of optical pumping, for which Alfred Kastler received the 1966 Nobel Prize in Physics, is that the absorption and scattering of anisotropic radiation can produce population imbalances and quantum coherence among the magnetic substates of atomic levels. The degree of this radiatively-induced atomic level polarization, which is very sensitive to the presence of magnetic fields, can be determined by observing the polarization of the scattered or transmitted spectral line radiation. The most important point for solar physics is that the outer solar atmosphere is an optically pumped vapor and that the polarization of the emergent spectral line radiation can be exploited to obtain quantitative information on the strength and/or geometry of magnetic fields within the chromosphere, transition region, and corona. Here we review some recent investigations of the polarization produced by optical pumping in selected IR, FUV, and EUV spectral lines, showing that their magnetic sensitivity is suitable for probing the magnetism of the outer solar atmosphere.

  5. Probing the magnetic relaxation and magnetic moment arrangement in a series of Dy4 squares.

    PubMed

    Wu, Jianfeng; Lin, Shuang-Yan; Shen, Si; Li, Xiao-Lei; Zhao, Lang; Zhang, Li; Tang, Jinkui

    2017-01-31

    Three μ4-O bridged Dy4 squares, {[Dy4(μ4-O)(HL(1))4(H2O)4]2(NO3)3(OH)}·2H2O·2CH3OH (1), [Dy4(μ4-O)(HL(2))4(SCN)2]·2H2O·4CH3OH (2) and [Dy4(μ4-O)(H2L(3))2(SCN)2]·6H2O (3) were assembled by using a Schiff base ligand and its dimerized and reduced congener, respectively. These complexes share a similar μ4-O bridged Dy4 core, while, both the coordination geometry and metal-ligand interactions are slightly changed upon the modulation of the ligands, resulting in distinct single-molecular magnetic (SMM) and single-molecular toroic (SMT) properties. In complex 1, the Schiff base ligands are in an antiparallel fashion and all Dy(III) ions are in a similar coordination geometry, realizing the toroidal arrangement of magnetic moments. For complex 2, the reduced ligand H3L(2) in a parallel fashion results in double relaxation processes and a 9-fold increase of the Ueff. Interestingly, with the use of the dimerized ligand H6L(3), we obtained complex 3, which is similar to complex 2, while due to the slight changes of the coordination environment both the single molecular magnetic property and toroidal magnetic moments almost disappeared.

  6. The magnetic resonance force microscope: A new microscopic probe of magnetic materials

    SciTech Connect

    Hammel, P.C.; Zhang, Z.; Midzor, M.; Roukes, M.L.; Wigen, P.E.; Childress, J.R.

    1997-08-06

    The magnetic resonance force microscope (MRFM) marries the techniques of magnetic resonance imaging (MRI) and atomic force microscopy (AFM), to produce a three-dimensional imaging instrument with high, potentially atomic-scale, resolution. The principle of the MRFM has been successfully demonstrated in numerous experiments. By virtue of its unique capabilities the MRFM shows promise to make important contributions in fields ranging from three-dimensional materials characterization to bio-molecular structure determination. Here the authors focus on its application to the characterization and study of layered magnetic materials; the ability to illuminate the properties of buried interfaces in such materials is a particularly important goal. While sensitivity and spatial resolution are currently still far from their theoretical limits, they are nonetheless comparable to or superior to that achievable in conventional MRI. Further improvement of the MRFM will involve operation at lower temperature, application of larger field gradients, introduction of advanced mechanical resonators and improved reduction of the spurious coupling when the magnet is on the resonator.

  7. Simple design of multiple aerodynamic plasma actuator

    NASA Astrophysics Data System (ADS)

    Chernyshev, S. L.; Gamirullin, M. D.; Kuryachii, A. P.; Litvinov, V. M.

    2017-06-01

    A new simple design of multiple dielectric barrier discharge (DBD) actuator intended for gas §ow acceleration in thin boundary layer on lengthy aerodynamic surface is proposed. The operability of the considered multi-DBD-actuator is con¦rmed experimentally. Proposed method of measurements of the electric power consumed by the actuator permits to estimate this value simply and with acceptable accuracy. The thrust generated by DBD-actuator and thrust-to-power relation were estimated owing to pressure probe measurements of the induced §ow velocity.

  8. Spin reorientation transition in Fe/CeH2 multilayers probed by soft X-ray resonant magnetic scattering

    NASA Astrophysics Data System (ADS)

    Dürr, H. A.; Münzenberg, M.; Felsch, W.; Dhesi, S. S.

    The magnetic domain configurations of Fe 3d spins in Fe/CeH2 multilayers were measured by soft X-ray resonant magnetic scattering. The interface region could be probed by setting up X-ray standing waves due to the multilayer periodicity. By resolving first- and second-order magnetic scattering contributions, we show that the latter probe directly the magneto-crystalline anisotropy which is dominated by the Fe interface layers causing a spin reorientation transition when the temperature is lowered.

  9. Development of Nuclear Magnetic Resonance Pulse Sequences and Probes to Study Biomacromolecules

    SciTech Connect

    Cosman, M; Krishnan, V V; Maxwell, R

    2001-02-26

    The determination of the three dimensional structures at high resolution of biomolecules, such as proteins and nucleic acids, enables us to understand their function at the molecular level. At the present time, there are only two methods available for determining such structures, nuclear magnetic resonance (NMR) spectroscopy and X-ray diffraction. Compared to well-established X-ray diffraction techniques, NMR methodology is relatively new and has many areas in which improvement can still be attained. In this project, we focused on the development of new NMR probes and pulse sequences that were tailored to tackle specific problems that are not adequately addressed by current technology. Probes are the hardware that contain the radio frequency (RF) circuitry used to both excite and detect the NMR signals. Pulse sequences are composed of a series of RF pulses and delays, which are applied to the sample held within the magnetic field by the probe, so as to manipulate the nuclear spins. Typically, a probe is developed for a specific set of nuclei and types of experiments and the pulse sequences are then written to use the probe in an optimal manner. In addition, the inter-development of instrumentation and methods are determined by the specific biological question to be examined. Thus our efforts focused on addressing an area of importance in NMR Structural Biology namely more effective ways to use the phosphorus ({sup 31}P) nucleus. Phosphorus is a very important biological element that is strategically located in nucleic acids, where it imparts negative charge and flexibility to RNA and DNA. It is also a component of the cellular membrane and thus interacts with membrane proteins. It is used in mechanisms to signal, activate or deactivate enzymes; and participates in energy storage and release. However, the phosphorus nucleus exhibits certain properties, such as poor spectral dispersion, low sensitivity of detection, and fast relaxation, which limit its effective use

  10. Theoretical Investigation of Dynamic Properties of Magnetic Molecule Systems as Probed by NMR and Pulsed Fields Experiments

    SciTech Connect

    Rousochatzakis, Ioannis

    2005-12-17

    The field of molecular magnetism[l-6] has become a subject of intense theoretical and experimental interest and has rapidly evolved during the last years. This inter-disciplinary field concerns magnetic systems at the molecular or "nanoscopic" level, whose realization has become feasible due to recent advances in the field of chemical synthesis. The present theoretical work provides a first step towards exploiting the possibilities that are offered by probing magnetic molecules using external magnetic fields with high sweep rates. These probes, apart for providing information specific to magnetic molecules, offer the possibility of conducting a detailed study of the relaxational behavior of interacting spin systems as a result of their coupling with a "heat bath" and in particular the excitations of the host lattice. Development of a broad theoretical framework for dealing with relaxational phenomena induced by dynamical magnetic fields is indeed a worthy goal.

  11. Topological protection of electronic states against disorder probed by their magnetic moment

    NASA Astrophysics Data System (ADS)

    Tadjine, Athmane; Delerue, Christophe

    2017-06-01

    Magnetic moments (MMs) of electrons in topological insulator quantum dots (TI-QDs) are investigated using a model system, namely a multiorbital honeycomb lattice. Their nature and orientation with respect to the spin are studied. We show that large MMs are not specific to edge states in nontrivial gaps, as band states can host even larger MMs. However, we demonstrate that edge-state and band-state MMs have a totally different sensitivity to disorder. Measuring the MMs in TI-QDs is therefore a direct way to probe the nontrivial to trivial topological transition under increasing disorder.

  12. Coaxial probe for nuclear magnetic resonance diffusion and relaxation correlation experiments

    SciTech Connect

    Tang, Yiqiao; Hürlimann, Martin; Mandal, Soumyajit; Paulsen, Jeffrey; Song, Yi-Qiao

    2014-02-21

    A coaxial nuclear magnetic resonance (NMR) probe is built to measure diffusion and relaxation properties of liquid samples. In particular, we demonstrate the acquisition of two-dimensional (2D) distribution functions (T{sub 1}-T{sub 2} and diffusion–T{sub 2}), essential for fluids characterization. The compact design holds promise for miniaturization, thus enabling the measurement of molecular diffusion that is inaccessible to conventional micro-NMR setups. Potential applications range from crude oil characterization to biomolecular screening and detections.

  13. Probing turbulent, magnetized star formation with ALMA observations and next-generation AREPO simulations

    NASA Astrophysics Data System (ADS)

    Hull, Charles L. H.; Mocz, Philip; Burkhart, Blakesley K.; Miquel Girart, Josep; Goodman, Alyssa A.; Cortes, Paulo; Li, Zhi-Yun; Lai, Shih-Ping; Hernquist, Lars; Springel, Volker

    2017-01-01

    The first polarization data from ALMA have been delivered, and are both expanding and confounding our understanding of the role of magnetic fields in low-mass star formation. Here I will show the highest resolution and highest sensitivity polarization images ever made of a Class 0 protostellar source. These new ALMA observations of the source, known as Ser-emb 8, achieve 140 AU resolution, allowing us to probe polarization -- and thus magnetic field orientation -- in the innermost regions surrounding the protostar. The collapse of strongly magnetized dense gas is predicted to pinch the magnetic field into an hourglass shape that persists down to scales <100 AU. However, in contrast with more than 50 years of theory, the ALMA data definitively rule out an hourglass morphology and instead reveal a chaotic magnetic field that has not been inherited from the field in the interstellar medium surrounding the source. We have simulated the star formation process with cutting-edge, moving-mesh AREPO simulations on scales from a million AU (5 pc) down to 60 AU. We find that only in the case of a very strong magnetic field (~100 microgauss on 5 pc scales) is the field direction preserved from cloud to disk scales. When the field is weak, turbulence in the interstellar gas shapes the field on large scales, and the forming star system re-shapes the field again on small scales, divorcing the field from its history on larger scales. We conclude that this is what has happened in Ser-emb 8. The main distinction from the strong-field star formation model is that in the weak-field case it is turbulence -- not the magnetic field -- that shapes the material that forms the protostar.

  14. Design and validation of the ball-pen probe for measurements in a low-temperature magnetized plasma.

    PubMed

    Bousselin, G; Cavalier, J; Pautex, J F; Heuraux, S; Lemoine, N; Bonhomme, G

    2013-01-01

    Ball-pen probes have been used in fusion devices for direct measurements of the plasma potential. Their application in low-temperature magnetized plasma devices is still subject to studies. In this context, a ball-pen probe has been recently implemented on the linear plasma device Mirabelle. Produced by a thermionic discharge, the plasma is characterized by a low electron temperature and a low density. Plasma confinement is provided by an axial magnetic field that goes up to 100 mT. The principle of the ball-pen probe is to adjust the saturation current ratio to 1 by reducing the electron current contribution. In that case, the floating potential of the probe is close to the plasma potential. A thorough study of the ball-pen probe operation is performed for different designs of the probe over a large set of plasma conditions. Comparisons between ball-pen, Langmuir, and emissive probes are conducted in the same plasma conditions. The ball-pen probe is successfully measuring the plasma potential in these specific plasma conditions only if an adapted electronics and an adapted probe size to the plasma characteristic lengths (λ(D), ρ(ce)) are used.

  15. Design and validation of the ball-pen probe for measurements in a low-temperature magnetized plasma

    SciTech Connect

    Bousselin, G.; Cavalier, J.; Pautex, J. F.; Heuraux, S.; Lemoine, N.; Bonhomme, G.

    2013-01-15

    Ball-pen probes have been used in fusion devices for direct measurements of the plasma potential. Their application in low-temperature magnetized plasma devices is still subject to studies. In this context, a ball-pen probe has been recently implemented on the linear plasma device Mirabelle. Produced by a thermionic discharge, the plasma is characterized by a low electron temperature and a low density. Plasma confinement is provided by an axial magnetic field that goes up to 100 mT. The principle of the ball-pen probe is to adjust the saturation current ratio to 1 by reducing the electron current contribution. In that case, the floating potential of the probe is close to the plasma potential. A thorough study of the ball-pen probe operation is performed for different designs of the probe over a large set of plasma conditions. Comparisons between ball-pen, Langmuir, and emissive probes are conducted in the same plasma conditions. The ball-pen probe is successfully measuring the plasma potential in these specific plasma conditions only if an adapted electronics and an adapted probe size to the plasma characteristic lengths ({lambda}{sub D}, {rho}{sub ce}) are used.

  16. Design of membrane actuators based on ferromagnetic shape memory alloy composite for the synthetic jet actuator

    NASA Astrophysics Data System (ADS)

    Liang, Yuanchang; Taya, Minoru; Kuga, Yasuo

    2004-07-01

    A new membrane actuator based on our previous diaphragm actuator was designed and constructed to improve the dynamic performance. The finite element analysis was used to estimate the frequency response of the composite membrane which will be driven close to its resonance to obtain a large stroke. The membrane is made of ferromagnetic shape memory alloy (FSMA) composite including a ferromagnetic soft iron pad and a superelastic grade of NiTi shape memory alloy (SMA). The actuation mechanism for the FSMA composite membrane of the actuator is the hybrid mechanism that we proposed previously. This membrane actuator is designed for a new synthetic jet actuator package that will be used for active flow control technology on airplane wings. Based on the FEM results, the new membrane actuator system was assembled and its static and dynamic performance was experimentally evaluated including the dynamic magnetic response of the hybrid magnet.

  17. Scanning Hall Probe Microscopy of Magnetic Vortices inVery Underdoped yttrium-barium-copper-oxide

    SciTech Connect

    Guikema, Janice Wynn; /SLAC, SSRL

    2005-12-02

    Since their discovery by Bednorz and Mueller (1986), high-temperature cuprate superconductors have been the subject of intense experimental research and theoretical work. Despite this large-scale effort, agreement on the mechanism of high-T{sub c} has not been reached. Many theories make their strongest predictions for underdoped superconductors with very low superfluid density n{sub s}/m*. For this dissertation I implemented a scanning Hall probe microscope and used it to study magnetic vortices in newly available single crystals of very underdoped YBa{sub 2}Cu{sub 3}O{sub 6+x} (Liang et al. 1998, 2002). These studies have disproved a promising theory of spin-charge separation, measured the apparent vortex size (an upper bound on the penetration depth {lambda}{sub ab}), and revealed an intriguing phenomenon of ''split'' vortices. Scanning Hall probe microscopy is a non-invasive and direct method for magnetic field imaging. It is one of the few techniques capable of submicron spatial resolution coupled with sub-{Phi}{sub 0} (flux quantum) sensitivity, and it operates over a wide temperature range. Chapter 2 introduces the variable temperature scanning microscope and discusses the scanning Hall probe set-up and scanner characterizations. Chapter 3 details my fabrication of submicron GaAs/AlGaAs Hall probes and discusses noise studies for a range of probe sizes, which suggest that sub-100 nm probes could be made without compromising flux sensitivity. The subsequent chapters detail scanning Hall probe (and SQUID) microscopy studies of very underdoped YBa{sub 2}Cu{sub 3}O{sub 6+x} crystals with T{sub c} {le} 15 K. Chapter 4 describes two experimental tests for visons, essential excitations of a spin-charge separation theory proposed by Senthil and Fisher (2000, 2001b). We searched for predicted hc/e vortices (Wynn et al. 2001) and a vortex memory effect (Bonn et al. 2001) with null results, placing upper bounds on the vison energy inconsistent with the theory. Chapter

  18. Optical Probe of the Superconducting Normal Mixed State in a Magnetic Penetration Thermometer

    NASA Technical Reports Server (NTRS)

    Stevenson, T. R.; Balvin, M. A.; Bandler, S. R.; Denis, K. L.; Lee, S. -J.; Nagler, P. C.; Smith, S. J.

    2016-01-01

    Using ultraviolet photon pulses, we have probed the internal behavior of a molybdenum-gold Magnetic Penetration Thermometer (MPT) that we designed for x-ray microcalorimetry. In this low-temperature detector, the diamagnetic response of a superconducting MoAu bilayer is used to sense temperature changes in response to absorbed photons. We have previously described an approximate model that explains the high responsivity of the detector to temperature changes as a consequence of a Meissner transition of the molybdenum-gold film in the magnetic field applied by the superconducting circuit used to bias the detector. We compare measurements of MPT heat capacity and thermal conductance, derived from UV photon pulse data, to our model predictions for the thermodynamic properties of the sensor and for the electron cooling obtained by quasiparticle recombination. Our data on electron cooling power is also relevant to the operation of other superconducting detectors, such as Microwave Kinetic Inductance Detectors.

  19. MicroRNA Sensor Based on Magnetic Beads and Enzymatic Probes

    NASA Astrophysics Data System (ADS)

    Zhang, Yue; Zhou, Dejian; He, Junhui

    2014-12-01

    MicroRNAs are associated with multiple cellular processes and diseases. Here, we designed a highly sensitive, magnetically retrievable biosensor using magnetic beads (MBs) as a model RNA sensor. The assay utilized two biotinylated probes, which were hybridized to the complementary target miRNA in a sandwich assay format. One of the biotinylated ends of the hybridization complex was immobilized onto the surface of a NeutrAvidin (NAV) coated MB and the other biotinylated end was conjugated to HRP via NAV-biotin interaction. The results were presented by colorimetric absorbance of the resorufin product from amplex red oxidation. We show that by combining the use of MBs as well as bio-specific immobilization, the sensitivity of miRNA detection is down to 100 pM. This model HRP-MBs system can be used for simple, rapid colorimetric quantification of low level DNA/RNA or other small molecules.

  20. A new approach for highly accurate, remote temperature probing using magnetic nanoparticles

    PubMed Central

    Zhong, Jing; Liu, Wenzhong; Kong, Li; Morais, Paulo Cesar

    2014-01-01

    In this study, we report on a new approach for remote temperature probing that provides accuracy as good as 0.017°C (0.0055% accuracy) by measuring the magnetisation curve of magnetic nanoparticles. We included here the theoretical model construction and the inverse calculation method, and explored the impact caused by the temperature dependence of the saturation magnetisation and the applied magnetic field range. The reported results are of great significance in the establishment of safer protocols for the hyperthermia therapy and for the thermal assisted drug delivery technology. Likewise, our approach potentially impacts basic science as it provides a robust thermodynamic tool for noninvasive investigation of cell metabolism. PMID:25315470

  1. Probing the solar magnetic field with a Sun-grazing comet.

    PubMed

    Downs, Cooper; Linker, Jon A; Mikií, Zoran; Riley, Pete; Schrijver, Carolus J; Saint-Hilaire, Pascal

    2013-06-07

    On 15 and 16 December 2011, Sun-grazing comet C/2011 W3 (Lovejoy) passed deep within the solar corona, effectively probing a region that has never been visited by spacecraft. Imaged from multiple perspectives, extreme ultraviolet observations of Lovejoy's tail showed substantial changes in direction, intensity, magnitude, and persistence. To understand this unique signature, we combined a state-of-the-art magnetohydrodynamic model of the solar corona and a model for the motion of emitting cometary tail ions in an embedded plasma. The observed tail motions reveal the inhomogeneous magnetic field of the solar corona. We show how these motions constrain field and plasma properties along the trajectory, and how they can be used to meaningfully distinguish between two classes of magnetic field models.

  2. How to probe transverse magnetic anisotropy of a single-molecule magnet by electronic transport?

    NASA Astrophysics Data System (ADS)

    Misiorny, M.; Burzuri, E.; Gaudenzi, R.; Park, K.; Leijnse, M.; Wegewijs, M.; Paaske, J.; Cornia, A.; van der Zant, H.

    We propose an approach for in-situ determination of the transverse magnetic anisotropy (TMA) of an individual molecule by electronic transport measurements, see Phys. Rev. B 91, 035442 (2015). We study a Fe4 single-molecule magnet (SMM) captured in a gateable junction, a unique tool for addressing the spin in different redox states of a molecule. We show that, due to mixing of the spin eigenstates of the SMM, the TMA significantly manifests itself in transport. We predict and experimentally observe the pronounced intensity modulation of the Coulomb peak amplitude with the magnetic field in the linear-response transport regime, from which the TMA parameter E can be estimated. Importantly, the method proposed here does not rely on the small induced tunnelling effects and, hence, works well at temperatures and electron tunnel broadenings by far exceeding the tunnel splittings and even E itself. We deduce that the TMA for a single Fe4 molecule captured in a junction is substantially larger than the bulk value. Work supported by the Polish Ministry of Science and Education as `Iuventus Plus' project (IP2014 030973) in years 2015-2016.

  3. Magnetic-nanoparticle-doped carbogenic nanocomposite: an effective magnetic resonance/fluorescence multimodal imaging probe.

    PubMed

    Srivastava, Sachchidanand; Awasthi, Rishi; Tripathi, Deepak; Rai, Mohit K; Agarwal, Vikas; Agrawal, Vinita; Gajbhiye, Namdeo S; Gupta, Rakesh K

    2012-04-10

    A novel and facile approach is developed to synthesize a magnetic nanoparticle (iron oxide)-doped carbogenic nanocomposite (IO-CNC) for magnetic resonance (MR)/fluorescence imaging applications. IO-CNC is synthesized by thermal decomposition of organic precursors in the presence of Fe(3) O(4) nanoparticles with an average size of 6 nm. IO-CNC shows wavelength-tunable fluorescence properties with high quantum yield. Magnetic studies confirm the superparamagnetic nature of IO-CNC at room temperature. IO-CNC shows MR contrast behavior by affecting the proton relaxation phenomena. The measured longitudinal (r(1) ) and transverse (r(2) ) relaxivity values are 4.52 and 34.75 mM(-1) s(-1) , respectively. No apparent cytotoxicity is observed and the nanocomposite shows a biocompatible nature. In vivo MR studies show both T(1) and T(2) * contrast behavior of the nanocomposite. Fluorescence imaging indicates selective uptake of IO-CNC by macrophages in spleen. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. High Temperature Magnetic Shape Memory Ni-Mn-Ga Alloys for a New Class of Actuators and Sensor

    DTIC Science & Technology

    2005-01-01

    sensors. Specifics of the project are: (i) the complex theoretical and experimental study of a correlation between electronic, magnetic, and crystalline ... structure and the phase transformation temperatures with occurrence of magnetic shape memory effect (MSME) using various experimental techniques and

  5. Bi and InSb Nano-Hall Probes for direct magnetic imaging with Room Temperature Scanning Hall Probe Microscopy(RT-SHPM)

    NASA Astrophysics Data System (ADS)

    Oral, Ahmet; Dede, Munir; Sandhu, Adarsh; Masuda, Hiroshi; Bending, Simon J.

    2002-03-01

    Scanning Hall Probe Microscopy (SHPM)[1] is a quantitative and non-invasive technique to image magnetic samples with high spatial and magnetic field resolution: ~ 120nm & 60mG/Hz^1/2 at room temperature. A nano-Hall probe is scanned over the sample surface to measure the surface magnetic fields using conventional scanning tunneling microscopy-positioning techniques. We have developed new down to ~120x120nm size Bi and InSb Hall probes machined FIB milling. 120nm Bi sensors[2] have a sensitivity of 3.3x10-4 Ω/G and a noise level of 7.2 G/Hz^1/2 . The new InSb sensors have a sensitivity of 0.03 Ω/G and a noise level of 8 mG/Hz^1/2 at room temperature. This corresponds to ×8 better noise performance compared to conventional GaAs, based sensors used in RT-SHPM. We used these new sensors to study magnetic domain structures of crystalline garnet films and Ni_80Fe_20 rectangular permalloy microstructures microfabricated by lift-off technique. Bi and InSb nano-Hall probes are shown to be high spatial resolution, high sensitivity and low noise alternatives to GaAs sensors for RT-SHPM. There seems to be more room for improving the spatial resolution down to <50nm and the noise of Hall probes to 1mG/Hz^1/2 at room temperature. [1] A. Oral et. al. Appl. Phys. Lett., 69, 1324 (1996), A. Sandhu et. al., Jpn. J. Appl. Phys. 40(5B), L524 (2001) [2] A. Sandhu, H. Masuda, K. Kurosawa K, A. Oral and S.J. Bending, Electronics Letters 37 (22), 1335-1336 (2001).

  6. Magnetic rotational spectroscopy with nanorods to probe time-dependent rheology of microdroplets.

    PubMed

    Tokarev, Alexander; Luzinov, Igor; Owens, Jeffery R; Kornev, Konstantin G

    2012-07-03

    In situ characterization of minute amounts of fluids that rapidly change their rheological properties is a challenge. In this paper, the rheological properties of fluids were evaluated by examining the behavior of magnetic nanorods in a rotating magnetic field. We proposed a theory describing the rotation of a magnetic nanorod in a fluid when its viscosity increases with time exponentially fast. To confirm the theory, we studied the time-dependent rheology of microdroplets of 2-hydroxyethyl-methacrylate (HEMA)/diethylene glycol dimethacylate (DEGDMA)-based hydrogel during photopolymerization synthesis. We demonstrated that magnetic rotational spectroscopy provides rich physicochemical information about the gelation process. The method allows one to completely specify the time-dependent viscosity by directly measuring characteristic viscosity and characteristic time. Remarkably, one can analyze not only the polymer solution, but also the suspension enriched with the gel domains being formed. Since the probing nanorods are measured in nanometers, this method can be used for the in vivo mapping of the rheological properties of biofluids and polymers on a microscopic level at short time intervals when other methods fall short.

  7. Probing the spinor nature of electronic states in nanosize non-collinear magnets (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Fischer, Jeison A.; Sander, Dirk; Parkin, Stuart

    2016-10-01

    Non-collinear magnets (NCM) exhibit a spatial variation of the magnetization direction, where helical and skyrmionic spin orders in materials have lately attracted considerable interest. This interest is spurred by both, exploring the physical origin of nanoscale NCM and applications in spintronics. Our study advances the understanding of nanoscale NCM by revealing the effect of nanoscale lateral confinement on the physical properties of NCM. We combine spin-polarized scanning tunneling microscopy/spectroscopy (sp-STM/S) and first-principles calculations to study prototypical helical NCM of some nm extension in proximity to both ferromagnetic Co and vacuum regions. We report a non-uniform distortion of the spin helix in an Fe bilayer on Cu(111)[1], where the spin orientation deviates from that of an ideal helical structure. The proximity to either Co or vacuum leads to distortions of the spin orientation within nm range of the respective interface. The distortions give rise to a specific energy dependent phenomenon of non-collinearity between the local magnetization in the sample and the electronic magnetization probed above its surface. This phenomenon is a direct consequence of the spinor nature of the electronic states in NCM. The symmetry breaking due to lateral confinement makes the spinor nature of electronic states observable in sp-STM/S experiments. [1] Phark, S. H.; Fischer, J. A.; Corbetta, M.; Sander, D.; Nakamura, K. and Kirschner, J. Reduced-dimensionality-induced helimagnetism in iron nanoislands Nat. Commun. 5 (2014) 5183.

  8. Magnetic hydroxyapatite coatings as a new tool in medicine: A scanning probe investigation.

    PubMed

    Gambardella, A; Bianchi, M; Kaciulis, S; Mezzi, A; Brucale, M; Cavallini, M; Herrmannsdoerfer, T; Chanda, G; Uhlarz, M; Cellini, A; Pedna, M F; Sambri, V; Marcacci, M; Russo, A

    2016-05-01

    Hydroxyapatite films enriched with magnetite have been fabricated via a Pulsed Plasma Deposition (PPD) system with the final aim of representing a new platform able to disincentivate bacterial adhesion and biofilm formation. The chemical composition and magnetic properties of films were respectively examined by X-ray photoelectron spectroscopy (XPS) and Superconducting Quantum Interference Device (SQUID) measurements. The morphology and conductive properties of the magnetic films were investigated via a combination of scanning probe technologies including atomic force microscopy (AFM), electrostatic force microscopy (EFM), and scanning tunneling microscopy (STM). Interestingly, the range of adopted techniques allowed determining the preservation of the chemical composition and magnetic properties of the deposition target material while STM analysis provided new insights on the presence of surface inhomogeneities, revealing the presence of magnetite-rich islands over length scales compatible with the applications. Finally, preliminary results of bacterial adhesion tests, indicated a higher ability of magnetic hydroxyapatite films to reduce Escherichia coli adhesion at 4h from seeding compared to control hydroxyapatite films.

  9. Oblique ion collection in the drift approximation: How magnetized Mach probes really work

    SciTech Connect

    Hutchinson, I. H.

    2008-12-15

    The anisotropic fluid equations governing a frictionless obliquely flowing plasma around an essentially arbitrarily shaped three-dimensional ion-absorbing object in a strong magnetic field are solved analytically in the quasineutral drift approximation, neglecting parallel temperature gradients. The effects of transverse displacements traversing the magnetic presheath are also quantified. It is shown that the parallel collection flux density dependence upon the external Mach number is n{sub {infinity}}c{sub s} exp[-1-(M{sub parallel}{infinity}-M{sub perpendicular}cot {theta})], where {theta} is the angle (in the plane of field and drift velocity) of the object-surface to the magnetic-field and M{sub parallel{infinity}} is the external parallel flow. The perpendicular drift, M{sub perpendicular}, appearing here consists of the external E and B drift plus a weighted sum of the ion and electron diamagnetic drifts that depends upon the total angle of the surface to the magnetic field. It is that somewhat counterintuitive combination that an oblique (transverse) Mach probe experiment measures.

  10. Probing Planets: Magnetic Fields and Angular Momentum Evolution in Exoplanetary Systems

    NASA Astrophysics Data System (ADS)

    Shkolnik, Evgenya

    Hot Jupiters, located only a few stellar radii from their parent stars, provide a laboratory in which we can study fundamental system parameters including planetary magnetic fields, a key component to understanding the planet s internal structure and atmospheric conditions. Over a dozen studies of hot Jupiter systems have independently converged on the same scenario: a short-period planet can induce activity on the photosphere and upper atmosphere of its host star, making the star itself a probe of its planet. This makes star- planet interactions currently the most promising way to study exoplanetary magnetic fields. Small data sets and possible selection effects in statistical studies have limited the opportunities to test the models and provide robust measurements. We aim to remedy this by analyzing large, high-quality spectroscopic and spectropolarimetric data sets recently acquired and specifically designed to accomplish our research goals. By combining these data with force-free models of magnetic star-planet interactions and simple scaling laws, we propose to: (1) Measure relative exoplanetary magnetic field strengths in a representative population of hot Jupiters. Detecting the presence or absence of a planetary magnetic field would: (a) Evaluate the planet s internal structure and its thermal evolution using dynamo theory, thereby informing us of its formation and evolution. (b) Provide a constraint on the rapid hydrodynamic escape of its atmosphere. (c) Determine the rotation period of the planet using the field s dependence on angular momentum and relationships known for Solar System planets. This will test the tidal models that predict that hot Jupiters are tidally locked to their stars. (2) Determine the planet s effect on the star s angular momentum evolution, either by hindering the star s magnetic braking mechanism or via tidal spin-up. Preliminary evidence shows that the age-rotation-activity relationship of these systems systematically

  11. A novel opto-electromagnetic actuator coupled to the tympanic membrane.

    PubMed

    Lee, Chia-Fone; Shih, Chih-Hua; Yu, Jen-Fang; Chen, Jyh-Horng; Chou, Yuan-Fang; Liu, Tien-Chen

    2008-12-05

    A new type of electromagnetic vibration transducer designed to be placed onto the tympanic membrane was developed. The actuator consisted of two photodiodes, two permanent magnets, an aluminum ring, two opposing wound coils, a latex membrane and a Provil Novo membrane. An optic probe was designed to allow sound and light signals to enter the ear canal, thereby preventing the acoustic occlusion effect of traditional ear molds. Two light-emitting diodes were used for carrying the input signals. The corresponding photodiodes were used for receiving the light signals and generating currents in the actuator. The opto-electromagnetic vibration actuator was fabricated and tested using a Laser Doppler vibrometer. The actuator showed displacements of vibration between 30 and 1 nm from 300 to 6500Hz and reduced in amplitude at higher frequencies. The average gain of the actuator with 140microA on the umbo displacement was about 20 dB relative to 87 dBA at the distance of 6cm from the tympanic membrane and 0microA in actuator.

  12. Study of Current Sheath Velocity and Its Distribution Using Tridimensional Magnetic Probe in Sahand Plasma Focus

    NASA Astrophysics Data System (ADS)

    A. Mohammadi, M.; Hedyeh, S.

    2015-05-01

    The current sheath velocity in 0.25 Torr gas pressure of Filippov type plasma focus is studied experimentally. By using two tridimensional magnetic probes on top of the anode surface, the current sheath velocity is measured for argon, oxygen and nitrogen. Additionally, the effect of charging voltage on the current sheath velocity is studied in both axial and radial phases. We found that, the maximum current sheath velocities at both radial and axial phases are respectively 4.33 ± 0.28 (cm/μs) and 3.92 ± 0.75 (cm/μs) with argon as the working gas at 17 kV. Also, the minimum values of current sheath velocity are 1.48 ± 0.15 (cm/μs) at the radial phase and 1.14 ± 0.09 (cm/μs) at the axial phase with oxygen at 12 kV. The current sheath velocity at the radial phase is higher than that at the axial phase for all gases and voltages. In this study, variation of the full width half maximum (FWHM) of magnetic probe signals with voltage is investigated for different gases at radial and axial phases.

  13. Magnetism in Complex Oxides Probed by Magnetocaloric Effect and Transverse Susceptibility

    NASA Astrophysics Data System (ADS)

    Bingham, Nicholas S.

    Magnetic oxides exhibit rich complexity in their fundamental physical properties determined by the intricate interplay between structural, electronic and magnetic degrees of freedom. The common themes that are often present in these systems are the phase coexistence, strong magnetostructural coupling, and possible spin frustration induced by lattice geometry. While a complete understanding of the ground state magnetic properties and cooperative phenomena in this class of compounds is key to manipulating their functionality for applications, it remains among the most challenging problems facing condensed-matter physics today. To address these outstanding issues, it is essential to employ experimental methods that allow for detailed investigations of the temperature and magnetic field response of the different phases. In this PhD dissertation, I will demonstrate the relatively unconventional experimental methods of magnetocaloric effect (MCE) and radio-frequency transverse susceptibility (TS) as powerful probes of multiple magnetic transitions, glassy phenomena, and ground state magnetic properties in a large class of complex magnetic oxides, including La0.7Ca0.3- xSrxMnO3 (x = 0, 0.05, 0.1, 0.2 and 0.25), Pr0.5Sr0.5MnO3, Pr1-xSrxCoO 3 (x = 0.3, 0.35, 0.4 and 0.5), La5/8- xPrxCa3/8MnO3 (x = 0.275 and 0.375), and Ca3Co2O 6. First, the influences of strain and grain boundaries, via chemical substitution and reduced dimensionality, were studied via MCE in La0.7Ca 0.3-xSrxMnO 3. Polycrystalline, single crystalline, and thin-film La0.7Ca 0.3-xSrxMnO 3 samples show a paramagnetic to ferromagnetic transition at a wide variety of temperatures as well as an observed change in the fundamental nature of the transition (i.e. first-order magnetic transition to second order magnetic transition) that is dependent on the chemical concentration and dimensionality. Systematic TS and MCE experiments on Pr0.5Sr0.5MnO 3 and Pr0.5Sr0.5CoO3 have uncovered the different nature of low

  14. Development of Magnetically Insulated Baffled Probe Cluster for Measurement of Energy Flux and Particle Flux in the Texas Helimak

    NASA Astrophysics Data System (ADS)

    Nogami, S. H.; Koepke, M.; Demidov, V.; Williams, C.; Gentle, K.

    2015-11-01

    Progress is reported in employing magnetically insulated baffled (MIB) probes in the Texas Helimak. Radial scans at the plasma edge of dc and ac space potential are presented. Like the Ball-Pen probe, the MIB probe shares the Langmuir probe simplicity and overcomes its shortcomings in the ability to make real-time measurements of plasma space potential, temperature, and energy/particle fluxes in magnetized plasma. By rotating the probe shaft to change the extent to which the baffle ``masks'' the probe collection area, the ratio between electron and ion probe current, and consequently the relative sensitivity of the floating-probe oscillations to space potential and electron/ion temperature, can be adjusted, thus allowing space potential fluctuations and electron/ion temperature fluctuations to be distinguished when measured at two different rotation angles. At the optimal rotation angle, the contribution of electron temperature and its fluctuations to the floating-potential measurement are eliminated and the space potential fluctuation phase is preserved. Support from DOE is gratefully acknowledged.

  15. Methanol masers probing the ordered magnetic field of W75N

    NASA Astrophysics Data System (ADS)

    Surcis, G.; Vlemmings, W. H. T.; Dodson, R.; van Langevelde, H. J.

    2009-11-01

    Context: The role of magnetic fields during the protostellar phase of high-mass star-formation is a debated topic. In particular, it is still unclear how magnetic fields influence the formation and dynamic of disks and outflows. Most current information on magnetic fields close to high-mass protostars comes from H2O and OH maser observations. Recently, the first 6.7 GHz methanol maser polarization observations were made, and they reveal strong and ordered magnetic fields. Aims: The morphology of the magnetic field during high-mass star-formation needs to be investigated on small scales, which can only be done using very long baseline interferometry observations. The massive star-forming region W75N contains three radio sources and associated masers, while a large-scale molecular bipolar outflow is also present. Polarization observations of the 6.7 GHz methanol masers at high angular resolution probe the strength and structure of the magnetic field and determine its relation to the outflow. Methods: Eight of the European VLBI network antennas were used to measure the linear polarization and Zeeman-splitting of the 6.7 GHz methanol masers in the star-forming region W75N. Results: We detected 10 methanol maser features, 4 of which were undetected in previous work. All arise near the source VLA 1 of W75N. The linear polarization of the masers reveals a tightly ordered magnetic field over more than 2000 AU around VLA 1 that is exactly aligned with the large-scale molecular outflow. This is consistent with the twisted magnetic field model proposed for explaining dust polarization observations. The Zeeman-splitting measured on 3 of the maser features indicates a dynamically important magnetic field in the maser region of the order of 50 mG. We suggest VLA 1 is the powering sources of the bipolar outflow. Member of the International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the Universities of Bonn and Cologne.

  16. Design and Testing of Three-Axis Satellite Attitude Determination and Stabilization Systems That Are Based on Magnetic Sensing and Actuation

    NASA Astrophysics Data System (ADS)

    Psiaki, Mark L.; Guelman, Moshe

    2002-11-01

    Three-axis satellite attitude determination and active stabilization systems have been designed and tested using both flight experiments and simulation studies. These are being developed for use on low-Earth-orbiting name- satellites. Such satellites can be used as elements of constellations that implement synthetic aperture radar or that serve as nudes in a communications network. The research has addressed the problems of under-sensing and under-actuation that are present in magnetic-based systems. Magnetometer outputs are insensitive to rotation about the local Earth magnetic field, and magnetic torque coils cannot produce torque slump the field direction. A new attitude representation and a special globally-convergent extended Kalman filter have been used to solve the 3-axis attitude estimation problem. The efficacy of this system has been demonstrated using data from the missions, the Hubble Space Telescope and the Far-Ultraviolet Spectroscopic Explorer. Semi-active global 3-axis stabilization has been demonstrated using a simplified magnetometer output feedback control law in combination with weak passive stabilization of the axes. The passive stabilization can come from a very small momentum wheel or from a new aerodynamic system. The momentum-wheel-based concept has been successfully tested on the TechSat Gurwin II spacecraft.

  17. Digital linear actuator

    SciTech Connect

    Birchard, W.G.

    1988-06-21

    A digital actuator is described comprising: (a) digital actuator cells, each digital actuator cell having an axis of expansion and first and second end surfaces; (b) third connecting means, each for connecting the first end surface of one digital actuator cell to the second end surface of an adjacent actuator cell, the plurality of digital actuator cells being connected in series by respective ones of the third connecting means to form the digital linear actuator.

  18. Mono-dispersed high magnetic resonance sensitive magnetite nanocluster probe for detection of nascent tumors by magnetic resonance molecular imaging.

    PubMed

    Zhang, Chunfu; Xie, Xuan; Liang, Sheng; Li, Mingli; Liu, Yajie; Gu, Hongchen

    2012-08-01

    Sensitive molecular imaging and detection of tumors or their supporting neovascularity require high-avidity, target-specific probes, which produce robust signal amplification compatible with a sensitive high-resolution imaging modality. In this context, we fabricated a high magnetic resonance (MR)-sensitive magnetite nanocluster (MNC) probe specific for tumor angiogenesis by assembly of hydrophobic superparamagnetic iron oxide nanoparticles (SPIONs) with (Mal)mPEG-PLA copolymer into cluster and subsequent encoding c(RGDyC) peptide on the cluster (RGD-MNC) for detection of nascent tumors. We found that RGD-MNC is highly sensitive (r(2) = 464.94 s(-1)mM(-1)) and specific for αvβ3-positive cells. Both nascent (35 ± 6.6 mm(3)) and large tumors (256 ± 22.3 mm(3)) can be registered by RGD-MNC and detected by MR imaging (MRI), with the nascent tumors demonstrating more pronounced MR contrast. Immunohistochemical studies revealed that MR signal decrease was closely correlated with histological characteristics of tumors (microvessel density and αvβ3 expression levels) at different growth stages.

  19. Analysis of Van Allen Probes Data Showing Nonlinear Electric Field Feedback During a Magnetic Storm

    NASA Astrophysics Data System (ADS)

    Liemohn, M. W.; Katus, R. M.; Smith, L. K.; Skoug, R. M.; Niehof, J. T.; Spence, H.; Wygant, J. R.; Bonnell, J. W.; Smith, C. W.; Kletzing, C.; Ilie, R.; Ganushkina, N.

    2013-12-01

    Van Allen Probes data was examined to assess the role of nonlinear feedback in relationship to the spatial structure of hot ions in the inner magnetosphere. During the magnetic storm that peaked on June 1, 2013, localized electric field perturbations from the EFW instrument were observed in relationship to the plasma pressure peak (as identified by the HOPE H+ and O+ fluxes in the 1-40 keV range, as well as magnetic field perturbations from EMFISIS) with a systematic sinusoidal perturbation. Near apogee, it takes the Van Allen Probes 30-60 minutes to traverse a peak in the ion fluxes. Therefore, the electric field was averaged over several minutes to remove the higher-frequency wave oscillations, revealing the longer-baseline perturbation associated with the pressure peak. While the fluxes indicate that the satellite is passing through a pressure peak, the magnetic field perturbation reveals the spatial location of the pressure extrema relative to the spacecraft location. The pattern of these electric fields relative to the location of the plasma pressure peak is in agreement with the hypothesis based on theory and numerical simulation results that an azimuthally localized pressure peak should create a systematic and predictable small-scale reconfiguration of the electric field. This electric field modification is because the field-aligned currents near each end of the pressure crescent close via Pedersen currents, perturbing the electric field in this region, as regulated by the ionospheric conductance. The level of this reconfiguration, relative to the expected dawn-dusk electric field within the magnetosphere, indicates the intensity of the nonlinear feedback.

  20. Probing the Chemical Stability of Mixed Ferrites: Implications for Magnetic Resonance Contrast Agent Design

    SciTech Connect

    Schultz-Sikma, Elise A.; Joshi, Hrushikesh M.; Ma, Qing; MacRenaris, Keith W.; Eckermann, Amanda L.; Dravid, Vinayak P.; Meade, Thomas J.

    2011-09-16

    Nanomaterials with mixed composition, in particular magnetic spinel ferrites, are emerging as efficient contrast agents for magnetic resonance imaging. Many factors, including size, composition, atomic structure, and surface properties, are crucial in the design of such nanoparticle-based probes because of their influence on the magnetic properties. Silica-coated iron oxide (IO-SiO{sub 2}) and cobalt ferrite (CoIO-SiO{sub 2}) nanoparticles were synthesized using standard high-temperature thermal decomposition and base-catalyzed water-in-oil microemulsion techniques. Under neutral aqueous conditions, it was found that 50-75% of the cobalt content in the CoIO-SiO{sub 2} nanoparticles leached out of the core structure. Leaching caused a 7.2-fold increase in the longitudinal relaxivity and an increase in the saturation magnetization from {approx}48 to {approx}65 emu/g of the core. X-ray absorption fine structure studies confirmed that the atomic structure of the ferrite core was altered following leaching, while transmission electron microscopy and dynamic light scattering confirmed that the morphology and size of the nanoparticle remained unchanged. The CoIO-SiO{sub 2} nanoparticles converted from a partially inverted spinel cation arrangement (unleached state) to an inverse spinel arrangement (leached state). The control IO-SiO{sub 2} nanoparticles remained stable with no change in the structure and negligible changes in the magnetic behavior. This detailed analysis highlights how important understanding the properties of nanomaterials is in the development of reliable agents for diagnostic and therapeutic applications.

  1. Magnetic Susceptibility of Ancient and Modern Potsherds Using a Fast, Cheap and Portable Probe

    NASA Astrophysics Data System (ADS)

    Glover, P. W.

    2009-05-01

    It has been estimated that there exist over 100 million ancient potsherds in various collections worldwide, many of which have never been studied and for which the provenance is ambiguous or unknown. Indeed, many collections are extremely badly catalogued or completely mixed-up. We have been using a novel portable probe to measure the magnetic susceptibility and electrical conductivity of potsherds in the hope that this fast, cheap and portable measurement can provide data that will help to sort similar looking potsherds into sets in a manner which may help to define their provenance. The probe, which resembles a firearm, uses the Hall effect to make a non-destructive measurement on the potsherd. The probe is attached to an Dell Axim X51 PDA, which runs software that allows the measurement to be carried out and logged. Each measurement, which is made by pressing a button on the gun, takes only a few seconds. We have made measurements on three suites of ancient potsherds as well as a suite of modern potsherds that were created by using a garden centre and a hammer! In each case a set of 5 stacked measurements were taken on the inside and outside faces of the potsherd in two perpendicular directions. Potsherds which were either (i) so flat that the inside and outside could not be distinguished, (ii) so curved (radius of curvature less than 5 cm) that the probe tip could not approach the surface sufficiently closely, or (iii) smaller than the probe tip, were excluded from the suite of measurements. Each suite contained over 50 measureable potsherds. All measurements were completed within one day. In this pilot study we found that (1) each suite was represented by a normal distribution of magnetic susceptibility values, (2) the four different suites could be distinguished statistically on the basis of their magnetic susceptibility measurements, but (3) the distinction was not sufficiently powerful to separate all potsherds (i.e., there was a significant overlap of the

  2. Zeeman effect in sulfur monoxide. A tool to probe magnetic fields in star forming regions

    NASA Astrophysics Data System (ADS)

    Cazzoli, Gabriele; Lattanzi, Valerio; Coriani, Sonia; Gauss, Jürgen; Codella, Claudio; Ramos, Andrés Asensio; Cernicharo, José; Puzzarini, Cristina

    2017-09-01

    Context. Magnetic fields play a fundamental role in star formation processes and the best method to evaluate their intensity is to measure the Zeeman effect of atomic and molecular lines. However, a direct measurement of the Zeeman spectral pattern from interstellar molecular species is challenging due to the high sensitivity and high spectral resolution required. So far, the Zeeman effect has been detected unambiguously in star forming regions for very few non-masing species, such as OH and CN. Aims: We decided to investigate the suitability of sulfur monoxide (SO), which is one of the most abundant species in star forming regions, for probing the intensity of magnetic fields via the Zeeman effect. Methods: We investigated the Zeeman effect for several rotational transitions of SO in the (sub-)mm spectral regions by using a frequency-modulated, computer-controlled spectrometer, and by applying a magnetic field parallel to the radiation propagation (i.e., perpendicular to the oscillating magnetic field of the radiation). To support the experimental determination of the g factors of SO, a systematic quantum-chemical investigation of these parameters for both SO and O2 has been carried out. Results: An effective experimental-computational strategy for providing accurate g factors as well as for identifying the rotational transitions showing the strongest Zeeman effect has been presented. Revised g factors have been obtained from a large number of SO rotational transitions between 86 and 389 GHz. In particular, the rotational transitions showing the largest Zeeman shifts are: N,J = 2, 2 ← 1, 1 (86.1 GHz), N,J = 4, 3 ← 3, 2 (159.0 GHz), N,J = 1, 1 ← 0, 1 (286.3 GHz), N,J = 2, 2 ← 1, 2 (309.5 GHz), and N,J = 2, 1 ← 1, 0 (329.4 GHz). Our investigation supports SO as a good candidate for probing magnetic fields in high-density star forming regions. The complete list of measured Zeeman components is only available at the CDS via anonymous ftp to http

  3. Modular droplet actuator drive

    NASA Technical Reports Server (NTRS)

    Pollack, Michael G. (Inventor); Paik, Philip (Inventor)

    2011-01-01

    A droplet actuator drive including a detection apparatus for sensing a property of a droplet on a droplet actuator; circuitry for controlling the detection apparatus electronically coupled to the detection apparatus; a droplet actuator cartridge connector arranged so that when a droplet actuator cartridge electronically is coupled thereto: the droplet actuator cartridge is aligned with the detection apparatus; and the detection apparatus can sense the property of the droplet on a droplet actuator; circuitry for controlling a droplet actuator coupled to the droplet actuator connector; and the droplet actuator circuitry may be coupled to a processor.

  4. A wide linear range Eddy Current Displacement Sensor equipped with dual-coil probe applied in the Magnetic Suspension Flywheel.

    PubMed

    Fang, Jiancheng; Wen, Tong

    2012-01-01

    The Eddy Current Displacement Sensor (ECDS) is widely used in the Magnetic Suspension Flywheel (MSFW) to measure the tiny clearance between the rotor and the magnetic bearings. The linear range of the ECDS is determined by the diameter of its probe coil. Wide clearances must be measured in some new MSFWs recently designed for the different space missions, but the coil diameter is limited by some restrictions. In this paper, a multi-channel ECDS equipped with dual-coil probes is proposed to extend the linear range to satisfy the demands of such MSFWs. In order to determine the best configuration of the dual-coil probe, the quality factors of the potential types of the dual-coil probes, the induced eddy current and the magnetic intensity on the surface of the measuring object are compared with those of the conventional single-coil probe. The linear range of the ECDS equipped with the selected dual-coil probe is extended from 1.1 mm to 2.4 mm under the restrictions without adding any cost for additional compensation circuits or expensive coil materials. The effectiveness of the linear range extension ability and the dynamic response of the designed ECDS are confirmed by the testing and the applications in the MSFW.

  5. Comparative measurements of plasma potential with ball-pen and Langmuir probe in low-temperature magnetized plasma

    SciTech Connect

    Zanáška, M.; Kudrna, P.; Tichý, M.; Adámek, J.; Peterka, M.

    2015-03-15

    The ball-pen probe (BPP) is used for direct plasma potential measurements in magnetized plasma. The probe can adjust the ratio of the electron and ion saturation currents I{sub sat}{sup −}/I{sub sat}{sup +} to be close to one and therefore its I-V characteristic becomes nearly symmetric. If this is achieved, the floating potential of the BPP is close to the plasma potential. Because of its rather simple construction, it offers an attractive probe for measurements in magnetized plasma. Comparative measurements of plasma potential by BPPs of different dimensions as well as one Langmuir probe (LP) in an argon discharge plasma of a cylindrical magnetron were performed at various experimental conditions. An additional comparison by an emissive probe was also performed. All these types of probes provide similar values of plasma potential in a wide range of plasma parameters. Our results for three different BPP dimensions indicate that the BPP can be operated in a cylindrical magnetron DC argon discharge if the value of the ratio of the magnetic field and neutral gas pressure, B/p, is greater than approximately 10 mT/Pa.

  6. A Wide Linear Range Eddy Current Displacement Sensor Equipped with Dual-Coil Probe Applied in the Magnetic Suspension Flywheel

    PubMed Central

    Fang, Jiancheng; Wen, Tong

    2012-01-01

    The Eddy Current Displacement Sensor (ECDS) is widely used in the Magnetic Suspension Flywheel (MSFW) to measure the tiny clearance between the rotor and the magnetic bearings. The linear range of the ECDS is determined by the diameter of its probe coil. Wide clearances must be measured in some new MSFWs recently designed for the different space missions, but the coil diameter is limited by some restrictions. In this paper, a multi-channel ECDS equipped with dual-coil probes is proposed to extend the linear range to satisfy the demands of such MSFWs. In order to determine the best configuration of the dual-coil probe, the quality factors of the potential types of the dual-coil probes, the induced eddy current and the magnetic intensity on the surface of the measuring object are compared with those of the conventional single-coil probe. The linear range of the ECDS equipped with the selected dual-coil probe is extended from 1.1 mm to 2.4 mm under the restrictions without adding any cost for additional compensation circuits or expensive coil materials. The effectiveness of the linear range extension ability and the dynamic response of the designed ECDS are confirmed by the testing and the applications in the MSFW. PMID:23112623

  7. Probing structure-property relationships in perpendicularly magnetized Fe/Cu(001) using MXLD and XPD

    SciTech Connect

    Cummins, T.R.; Waddill, G.D.; Goodman, K.W.

    1997-04-01

    Magnetic X-ray Linear Dichroism (MXLD) in Photoelectron Spectroscopy and X-Ray Photoelectron Diffraction (XPD) of the Fe 3p core level have been used to probe the magnetic structure-property relationships of perpendicularly magnetized Fe/Cu(001), in an element-specific fashion. A strong MEXLD effect was observed in the high resolution photoelectron spectroscopy of the Fe 3p at {open_quotes}normal{close_quotes} emission and was used to follow the loss of perpendicular ferromagnetic ordering as the temperature was raised toward room temperature. In parallel with this, {open_quotes}Forward Focussing{close_quotes} in XPD was used as a direct measure of geometric structure in the overlayer. These results and the implications of their correlation will be discussed. Additionally, an investigation of the effect of Mn doping of the Fe/Cu(001) will be described. These measurements were performed at the Spectromicroscopy Facility (Beamline 7.0.1) of the Advanced Light Source.

  8. Detection of Escherichia coli in drinking water using T7 bacteriophage-conjugated magnetic probe.

    PubMed

    Chen, Juhong; Alcaine, Samuel D; Jiang, Ziwen; Rotello, Vincent M; Nugen, Sam R

    2015-09-01

    In this study, we demonstrate a bacteriophage (phage)-based magnetic separation scheme for the rapid detection of Escherichia coli (E. coli) in drinking water. T7 phage is a lytic phage with a broad host range specificity for E. coli. Our scheme was as follows: (1) T7 bacteriophage-conjugated magnetic beads were used to capture and separate E. coli BL21 from drinking water; (2) subsequent phage-mediated lysis was used to release endemic β-galactosidase (β-gal) from the bound bacterial cells; (3) the release of β-gal was detected using chlorophenol red-β-d-galactopyranoside (CRPG), a colorimetric substrate which changes from yellow to red in the presence of β-gal. Using this strategy, we were able to detect E. coli at a concentration of 1 × 10(4) CFU·mL(-1) within 2.5 h. The specificity of the proposed magnetic probes toward E. coli was demonstrated against a background of competing bacteria. By incorporating a pre-enrichment step in Luria-Bertani (LB) broth supplemented with isopropyl β-d-thiogalactopyranoside (IPTG), we were able to detect 10 CFU·mL(-1) in drinking water after 6 h of pre-enrichment. The colorimetric change can be determined either by visual observation or with a reader, allowing for a simple, rapid quantification of E. coli in resource-limited settings.

  9. Circularly polarized high harmonic generation for element-selective probing of magnetic materials on a tabletop

    NASA Astrophysics Data System (ADS)

    Grychtol, Patrick; Turgut, Emrah; Zusin, Dmitriy; Popmintchev, Dimitar; Popmintchev, Tenio; Kapteyn, Henry; Murnane, Margaret; Knut, Ronny; Nembach, Hans; Shaw, Justin; Kfir, Ofer; Fleischer, Avner; Cohen, Oren

    2014-03-01

    Ultrafast short wavelength sources based on high harmonic upconversion of femtosecond lasers are unique in their ability to simultaneously probe the magnetically-sensitive M absorption edges of the 3d ferromagnets Fe, Co and Ni. This novel capability to capture the fastest spin dynamics in materials has uncovered a wealth of new fundamental understanding about spin scattering and transport on few-femtosecond timescales. However, to date these investigations have used linearly polarized higher harmonics, since it has not been possible to generate circularly polarized harmonics with sufficient flux for scientific applications. In this contribution, we present a simple setup that enables the efficient generation of circularly polarized harmonics, and demonstrates that they are bright enough for studies of magnetic materials. The fundamental and second harmonic of a Ti:sapphire laser are focused into a gas filled waveguide under good phase matching conditions, with opposite chirality circular polarizations. Thus, circularly-polarized harmonics are produced that are then used to perform magnetic circular dichroism studies in the extreme ultraviolet photon energy range.

  10. Preparation and Characterization of a Magnetic and Optical Dual-Modality Molecular Probe

    PubMed Central

    Bumb, A; Regino, C A S; Perkins, M R; Bernardo, M; Ogawa, M; Fugger, L; Choyke, P L; Dobson, P J; Brechbiel, M W

    2010-01-01

    Multi-modality imaging probes combine the advantages of individual imaging techniques to yield highly detailed anatomic and molecular information in living organisms. Herein, we report the synthesis and characterization of a dual-modality nanoprobe that couples the magnetic properties of ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) with the near infrared fluorescence of Cy5.5. The fluorophore is encapsulated in a biocompatible shell of silica surrounding the iron oxide core for a final diameter of ~17 nm. This silica-coated iron oxide nanoparticle (SCION) has been analyzed by transmission electron microscopy, dynamic light scattering, and superconducting quantum interference device (SQUID). The particle demonstrates a strong negative surface charge and maintains colloidal stability in the physiological pH range. Magnetic hysteresis analysis confirms superparamagnetic properties that could be manipulated for thermotherapy. The viability of primary human monocytes, T cells, and B cells incubated with particle has been examined in vitro. In vivo analysis of agent leakage into subcutaneous A431 tumors in mice was also conducted. This particle has been designed for diagnostic application with magnetic resonance and fluorescence imaging, and has future potential to serve as a heat-sensitive targeted drug delivery platform. PMID:20368682

  11. Probing boundary magnetization through exchange bias in heterostructures with competing anisotropy

    NASA Astrophysics Data System (ADS)

    Wang, Yi; Binek, Christian

    2013-03-01

    Cr2O3 (chromia) is a magnetoelectric antiferromagnet with a bulk TN of 307 K. It has been utilized for electrically controlled exchange bias (EB) by taking advantage of voltage-controllable boundary magnetization (BM) occurring as a generic property in magnetoelectric single domain antiferromagnets.[2] In the perpendicular Cr2O3(0001)/CoPd EB system the EB-field shows an order parameter type T-dependence close to TN reflecting the T-dependence of the BM. At about 150 K a decrease of the EB-field sets in with decreasing temperature suggesting canting of the BM. To evidence this mechanism we use EB as a probe. Specifically, we investigate EB in Permalloy(5nm)/Cr2O3 (0001)(100nm) with Permalloy and chromia having competing anisotropies. We measure easy axis magnetic hysteresis loops via longitudinal magneto-optical Kerr effect for various temperatures after perpendicular and in-plane magnetic field-cooling. The T-dependence of the EB field supports the canting mechanism. In addition to the all thin film EB system, we explore a Permalloy(10nm)/Cr2O3(0001 single crystal) heterostructure where magnetoelectric annealing allows selecting Cr2O3 single domain states. Here the effect of T-dependent canting of the BM is compared with findings in the complementary perpendicular EB system. Financial support by NSF through MRSEC and the Nanoelectronic Research Initiative.

  12. Improved Electrohydraulic Linear Actuators

    NASA Technical Reports Server (NTRS)

    Hamtil, James

    2002-01-01

    A product line of improved electrohydraulic linear actuators has been developed. These actuators are designed especially for use in actuating valves in rocket-engine test facilities. They are also adaptable to similar industrial uses. Advantageous features of the electrohydraulic linear actuators with respect to shortcomings of prior electrohydraulic linear actuators are described.

  13. Two-axis probing system for atomic force m