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1

Probing Gravitational Sensitivity in Biological Systems Using Magnetic Body Forces  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

2

Interaction Forces Between Multiple Bodies in a Magnetic Field  

NASA Technical Reports Server (NTRS)

Some of the results from experiments to determine the interaction forces between multiple bodies in a magnetic field are presented in this paper. It is shown how the force values and the force directions depend on the configuration of the bodies, their relative positions to each other, and the vector of the primary magnetic field. A number of efficient new automatic loading and assembly machines, as well as manipulators and robots, have been created based on the relationship between bodies and magnetic fields. A few of these patented magnetic devices are presented. The concepts involved open a new way to design universal grippers for robot and other kinds of mechanisms for the manipulation of objects. Some of these concepts can be used for space applications.

Joffe, Benjamin

1996-01-01

3

Tunneling magnetic force microscopy  

NASA Technical Reports Server (NTRS)

We have developed a powerful new tool for studying the magnetic patterns on magnetic recording media. This was accomplished by modifying a conventional scanning tunneling microscope. The fine-wire probe that is used to image surface topography was replaced with a flexible magnetic probe. Images obtained with these probes reveal both the surface topography and the magnetic structure. We have made a thorough theoretical analysis of the interaction between the probe and the magnetic fields emanating from a typical recorded surface. Quantitative data about the constituent magnetic fields can then be obtained. We have employed these techniques in studies of two of the most important issues of magnetic record: data overwrite and maximizing data-density. These studies have shown: (1) overwritten data can be retrieved under certain conditions; and (2) improvements in data-density will require new magnetic materials. In the course of these studies we have developed new techniques to analyze magnetic fields of recorded media. These studies are both theoretical and experimental and combined with the use of our magnetic force scanning tunneling microscope should lead to further breakthroughs in the field of magnetic recording.

Burke, Edward R.; Gomez, Romel D.; Adly, Amr A.; Mayergoyz, Isaak D.

1993-01-01

4

Exploring Magnetism: Investigating the forces of magnets  

NSDL National Science Digital Library

This activity is a classroom and lab investigation of magnetism. Students gather results of experiments involving the forces of magnets. They use this data to develop their own experiments to test properties of magnets.

5

Three-Body Forces from n-BODY Inversion  

NASA Astrophysics Data System (ADS)

Within the context of the lowest order approximation to the calculation of the n-body bound state in the Hyperspherical Harmonic Expansion Method, the hypercentral potential may be determined from n-body spectral data. Previously, we showed how the two-body force can be determined exactly from the hypercentral potential in the absence of three-body forces. In this paper, we investigate to what extent the three-body force can be determined if the two-body force is assumed to be known. For this purpose, a three-quark system is considered.

Gavin, E. J. O.; Fiedeldey, H.; Sofianos, S. A.

6

Updates of the nuclear equation of state for core-collapse supernovae and neutron stars: effects of 3-body forces, QCD, and magnetic fields  

NASA Astrophysics Data System (ADS)

We summarize several new developments in the nuclear equation of state for supernova simulations and neutron stars. We discuss an updated and improved Notre-Dame-Livermore Equation of State (NDL EoS) for use in supernovae simulations. This Eos contains many updates. Among them are the effects of 3- body nuclear forces at high densities and the possible transition to a QCD chiral and/or super-conducting color phase at densities. We also consider the neutron star equation of state and neutrino transport in the presence of strong magnetic fields. We study a new quantum hadrodynamic (QHD) equation of state for neutron stars (with and without hyperons) in the presence of strong magnetic fields. The parameters are constrained by deduced masses and radii. The calculated adiabatic index for these magnetized neutron stars exhibit rapid changes with density. This may provide a mechanism for star-quakes and flares in magnetars. We also investigate the strong magnetic field effects on the moments of inertia and spin down of neutron stars. The change of the moment of inertia associated with emitted magnetic flares is shown to match well with observed glitches in some magnetars. We also discuss a perturbative calculation of neutrino scattering and absorption in hot and dense hyperonic neutron-star matter in the presence of a strong magnetic field. The absorption cross-sections show a remarkable angular dependence in that the neutrino absorption strength is reduced in a direction parallel to the magnetic field and enhanced in the opposite direction. The pulsar kick velocities associated with this asymmetry comparable to observed pulsar velocities and may affect the early spin down rate of proto-neutron star magnetars with a toroidal field configuration.

Mathews, G. J.; Meixner, M.; Olson, J. P.; Suh, I.-S.; Kajino, T.; Maruyama, T.; Hidaka, J.; Ryu, C.-Y.; Cheoun, M.-K.; Lan, N. Q.

2013-07-01

7

Advances in Magnetic Force Microscopy John Moreland, Chairman Magnetic dissipation force microscopy studies of magnetic  

E-print Network

Advances in Magnetic Force Microscopy John Moreland, Chairman Magnetic dissipation force microscopy dissipation force microscopy to magnetic materials. Energy dissipation is measured by simultaneous monitoring0021-8979 98 48611-0 Magnetic dissipation force microscopy1­4 is a working mode of an ac magnetic force

Grütter, Peter

8

NTNU Java: Free-Body Force Diagram  

NSDL National Science Digital Library

This applet illustrates the forces on a block on an inclined plane. A free-body diagram shows the gravitational, normal, frictional and net force vectors. The weight, angle of the plane, and coefficient of friction can be changed by the user. The user can also apply an external force to the block. The motion resulting from the forces is not shown.

Hwang, Fu-Kwun

2005-02-07

9

Three-body forces and the trinucleons  

SciTech Connect

Three-body forces are discussed in the context of classical, atomic, solid-state and nuclear physics. The basic theoretical ingredients used in the construction of such forces are reviewed. Experimental evidence for three-nucleon forces and an overview of the three-nucleon bound states are presented. 53 refs., 9 figs.

Friar, J.L.

1987-01-01

10

Investigating Magnetic Force Fields  

NSDL National Science Digital Library

In this classroom activity, the students will investigate the magnetic pull of a bar magnet at varying distances with the use of paper clips. Students will hypothesize, conduct the experiment, collect the data, and draw conclusions that support their data. Each student will record the experiment and their findings in their science journals. As a class, students will compare each groups' data and their interpretation of the results.

Daryl ("Tish") Monjeau, Bancroft Elementary School, Minneapolis, MN

2012-03-18

11

Magnetic elements for switching magnetization magnetic force microscopy tips.  

SciTech Connect

Using combination of micromagnetic calculations and magnetic force microscopy (MFM) imaging we find optimal parameters for novel magnetic tips suitable for switching magnetization MFM. Switching magnetization MFM is based on two-pass scanning atomic force microscopy with reversed tip magnetization between the scans. Within the technique the sum of the scanned data with reversed tip magnetization depicts local atomic forces, while their difference maps the local magnetic forces. Here we propose the design and calculate the magnetic properties of tips suitable for this scanning probe technique. We find that for best performance the spin-polarized tips must exhibit low magnetic moment, low switching fields, and single-domain state at remanence. The switching field of such tips is calculated and optimum shape of the Permalloy elements for the tips is found. We show excellent correspondence between calculated and experimental results for Py elements.

Cambel, V.; Elias, P.; Gregusova, D.; Martaus, J.; Fedor, J.; Karapetrov, G.; Novosad, V. (Materials Science Division); (Slovak Academy of Sciences)

2010-09-01

12

Three-body critical Casimir forces  

E-print Network

Within mean-field theory we calculate universal scaling functions associated with critical Casimir forces for a system consisting of three parallel cylindrical colloids immersed in a near-critical binary liquid mixture. For several geometrical arrangements and boundary conditions at the surfaces of the colloids we study the force between two colloidal particles along their center-to-center axis, analyzing the influence of the presence of a third particle on that force. Upon changing temperature or the relative positions of the particles we observe interesting features such as a change of sign of this force caused by the presence of the third particle. We determine the three-body component of the forces acting on one of the colloids by subtracting the pairwise forces from the total force. The three-body contribution to the total critical Casimir force turns out to be more pronounced for small surface-to-surface distances between the colloids as well as for temperatures close to criticality. Moreover we compare our results with similar ones for other physical systems such as three atoms interacting via van der Waals forces.

T. G. Mattos; L. Harnau; S. Dietrich

2015-01-07

13

Magnetic Resonance Force Microscope Development  

SciTech Connect

Our objectives were to develop the Magnetic Resonance Force Microscope (MRFM) into an instrument capable of scientific studies of buried structures in technologically and scientifically important electronic materials such as magnetic multilayer materials. This work resulted in the successful demonstration of MRFM-detected ferromagnetic resonance (FMR) as a microscopic characterization tool for thin magnetic films. Strong FMR spectra obtained from microscopic Co thin films (500 and 1000 angstroms thick and 40 x 200 microns in lateral extent) allowed us to observe variations in sample inhomogeneity and magnetic anisotropy field. We demonstrated lateral imaging in microscopic FMR for the first time using a novel approach employing a spatially selective local field generated by a small magnetically polarized spherical crystallite of yttrium iron garnet. These successful applications of the MRFM in materials studies provided the basis for our successful proposal to DOE/BES to employ the MRF M in studies of buried interfaces in magnetic materials.

Hammel, P.C.; Zhang, Z.; Suh, B.J.; Roukes, M.L.; Midzor, M.; Wigen, P.E.; Childress, J.R.

1999-06-03

14

Development of compact magnet for high magnetic force  

Microsoft Academic Search

A high magnetic force is useful for levitating diamagnetic or magnetic materials. The magnetic force is proportional to the product of B and dB\\/dz. Here the product is called the magnetic force Held. Normally, a high magnetic force field is available only with 20 T class magnets in a few, high-field magnet facilities worldwide. We therefore anticipate realizing zero gravity

Kazutomi Miyoshi; Hitoshi Shimizu; Shin-ichiro Meguro; Hisamichi Uetake; Noriyuki Hirota; Koichi Kitazawa

2002-01-01

15

Magnetic Force Three Wires Model  

NSDL National Science Digital Library

The Magnetic Force Three Wires model investigates the force between long straight current-carrying wires. Initially, the simulation shows a cross-section view of three long straight parallel wires, each on the corner of an equilateral triangle. The wires carry currents that have different magnitudes, and the currents are directed either into or out of the page. The task in this simulation is to rank the wires based on the magnitude of their currents, from largest to smallest. The Magnetic Force Three Wires model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_bu_Three_Wires.jar file will run the program if Java is installed. This is part of a collection of similar tutorial simulations created by the author.

Duffy, Andrew

2009-10-20

16

Investigation of a cuboidal permanent magnets force exerted on a robotic capsule  

PubMed Central

To control and drive a robotic capsule accurately from outside a patients body, we present a schema in which the capsule enclosing the imaging device, circuits, batteries, etc is looped by a permanent magnet ring that acts as an actuator. A cuboidal permanent magnet situated outside the patients body attracts or pushes the magnet ring from different directions to make the capsule move or rotate. A mathematic model of attractive or repulsive force that the cuboidal magnet exerts on the magnet ring is presented for accurate calculation of force. The experiments showed that the measuring force was in agreement with the theoretical one, and the relations between the dimensions of the cuboidal magnet and force are useful to produce a cuboidal magnet with optimal shape to get appropriate force. PMID:25170283

Yang, Wanan; Tang, Chengbing; Qin, Fengqing

2014-01-01

17

Force sensor using changes in magnetic flux  

NASA Technical Reports Server (NTRS)

A force sensor includes a magnetostrictive material and a magnetic field generator positioned in proximity thereto. A magnetic field is induced in and surrounding the magnetostrictive material such that lines of magnetic flux pass through the magnetostrictive material. A sensor positioned in the vicinity of the magnetostrictive material measures changes in one of flux angle and flux density when the magnetostrictive material experiences an applied force that is aligned with the lines of magnetic flux.

Pickens, Herman L. (Inventor); Richard, James A. (Inventor)

2012-01-01

18

Cryogenic magnetic force microscope M. Rosemana)  

E-print Network

Cryogenic magnetic force microscope M. Rosemana) and P. Gru¨tter Centre for the Physics for publication 27 June 2000 We describe our cryogenic magnetic force microscope, operating between 4.2 and 300 K. As an effective means of vibration isolation, we suspend the microscope from a soft bellows which attenuates

Grütter, Peter

19

A force calibration standard for magnetic tweezers  

NASA Astrophysics Data System (ADS)

To study the behavior of biological macromolecules and enzymatic reactions under force, advances in single-molecule force spectroscopy have proven instrumental. Magnetic tweezers form one of the most powerful of these techniques, due to their overall simplicity, non-invasive character, potential for high throughput measurements, and large force range. Drawbacks of magnetic tweezers, however, are that accurate determination of the applied forces can be challenging for short biomolecules at high forces and very time-consuming for long tethers at low forces below 1 piconewton. Here, we address these drawbacks by presenting a calibration standard for magnetic tweezers consisting of measured forces for four magnet configurations. Each such configuration is calibrated for two commonly employed commercially available magnetic microspheres. We calculate forces in both time and spectral domains by analyzing bead fluctuations. The resulting calibration curves, validated through the use of different algorithms that yield close agreement in their determination of the applied forces, span a range from 100 piconewtons down to tens of femtonewtons. These generalized force calibrations will serve as a convenient resource for magnetic tweezers users and diminish variations between different experimental configurations or laboratories.

Yu, Zhongbo; Dulin, David; Cnossen, Jelmer; Kber, Mariana; van Oene, Maarten M.; Ordu, Orkide; Berghuis, Bojk A.; Hensgens, Toivo; Lipfert, Jan; Dekker, Nynke H.

2014-12-01

20

May the Magnetic Force Be with You  

NSDL National Science Digital Library

After a demonstration of the deflection of an electron beam, students review their knowledge of the cross-product and the right-hand rule with example problems. Then they study the magnetic force on a charged particle, compared to the electric force. Provided lecture material covers the motion of a charged particle in a magnetic field with respect to the direction of the field. Finally, students apply these concepts to understand the magnetic force on a current carrying wire. Through the associated activity, students further explore the force on a current carrying wire.

VU Bioengineering RET Program, School of Engineering,

21

Magnetic particle separation using controllable magnetic force switches  

NASA Astrophysics Data System (ADS)

Magnetic particle separation is very important in biomedical applications. In this study, a magnetic particle microseparator is proposed that uses micro magnets to produce open/closed magnetic flux for switching on/off the separation. When all magnets are magnetized in the same direction, the magnetic force switch for separation is on; almost all magnetic particles are trapped in the channel side walls and the separation rate can reach 95%. When the magnetization directions of adjacent magnets are opposite, the magnetic force switch for separation is off, and most magnetic particles pass through the microchannel without being trapped. For the separation of multi-sized magnetic particles, the proposed microseparator is numerically demonstrated to have high separation rate.

Wei, Zung-Hang; Lee, Chiun-Peng; Lai, Mei-Feng

2010-01-01

22

Modeling solar force-free magnetic fields  

Microsoft Academic Search

A class of nonlinear force-free magnetic fields is presented, described in terms of the solutions to a second-order, nonlinear ordinary differential equation. These magnetic fields are three-dimensional, filling the infinite half-space above a plane where the lines of force are anchored. They model the magnetic fields of the sun over active regions with a striking geometric realism. The total energy

B. C. Low; Y. Q. Lou

1990-01-01

23

Development of a body force description for compressor stability assessment  

E-print Network

This thesis presents a methodology for a body force description of a compressor with particular application to compressor stability calculations. The methodology is based on extracting blade forces from an axisymmetric ...

Kiwada, George (George Ford)

2008-01-01

24

3420 IEEE TRANSACTIONS ON MAGNETICS, VOL. 39, NO. 5, SEPTEMBER 2003 Magnetic Force Microscopy Studies of  

E-print Network

3420 IEEE TRANSACTIONS ON MAGNETICS, VOL. 39, NO. 5, SEPTEMBER 2003 Magnetic Force Microscopy Studies of Patterned Magnetic Structures Xiaobin Zhu and Peter Grutter Abstract--Magnetic force microscopy force microscopy is a tool for imaging, manipulating, characterizing magnetization switching

Grütter, Peter

25

Light-induced attractive force between two metal bodies separated by a subwavelength slit  

NASA Astrophysics Data System (ADS)

A novel light-induced attractive force which acts as a force with negative light pressure has been revealed. The force arises by the interaction of plasmon polaritons which are excited at the surface of metal when a transverse magnetic mode propagates through a subwavelength slit between two metal bodies. The estimation of the repulsive force acting on the metal walls of the slit in the case of subwavelength TE mode propagation along the slit is presented. The explicit analytical expressions of light-induced forces between two macroscopic metal bodies or films separated by a subwavelength slit have been derived. These forces could be used to manipulate metallic macro-, micro- and nano-objects in vacuum or in a dielectric medium. Estimations of these light-induced forces show that the forces are sufficient for measurements and practical applications.

Nesterov, Vladimir; Frumin, Leonid

2011-09-01

26

Body Force Model for the Aerodynamics of Inclined Perforated Surfaces  

E-print Network

Body Force Model for the Aerodynamics of Inclined Perforated Surfaces Juntao Xiong, Andrew Johnson of perforated surfaces inclined to a freestream. The goal is to characterize the key parameters affecting coefficient Cp = pressure coefficient D = hole size on plane of freestream FB = body force H = nozzle height h

Papamoschou, Dimitri

27

Magnetic force and work: an accessible example  

NASA Astrophysics Data System (ADS)

Despite their physics instructors arguments to the contrary, introductory students can observe situations in which there seems to be compelling evidence for magnetic force doing work. The counterarguments are often highly technical and require physics knowledge beyond the experience of novice students, however. A simple example is presented which can illustrate that all may not be what it seems when energy transfer and the magnetic force are involved. Excel and Python simulations of the process are also provided.

Gates, Joshua

2014-05-01

28

Ideal bodies for Mars magnetics  

Microsoft Academic Search

The high-amplitude magnetic anomalies observed by the Mars Global Surveyor imply the presence of a large intensity of magnetization in the Martian crust. We investigate the mathematical question of determining the distribution of magnetization that has the smallest possible intensity, without any assumptions about the direction of magnetization. The greatest lower bound on intensity found in this way depends on

Robert L. Parker

2003-01-01

29

Manipulation and identification of objects by magnetic forces  

NASA Technical Reports Server (NTRS)

An overview is presented of the results of research and engineering design activities over the past 20 years in the area of identification and manipulation of objects by magnetic forces. The relationship is discussed between the properties of objects and the parameters of magnetic fields, with the view toward being able to create forces for efficient manipulation and identification of different kinds of parts. Some of this information, particularly regarding nonferromagnetic materials, is relatively new and can be used to solve a variety of engineering problems by creating new types of automation systems. Topics covered include identification and orientation of bodies by magnetostatic and electrodynamic forces, electromagnetic recognition and orientation of nonsymmetric parts, and assembly and position control of parts by electromagnetic forces.

Joffe, Benjamin

1992-01-01

30

Treatment of body forces in boundary element design sensitivity analysis  

NASA Technical Reports Server (NTRS)

The inclusion of body forces has received a good deal of attention in boundary element research. The consideration of such forces is essential in the desgin of high performance components such as fan and turbine disks in a gas turbine engine. Due to their critical performance requirements, optimal shapes are often desired for these components. The boundary element method (BEM) offers the possibility of being an efficient method for such iterative analysis as shape optimization. The implicit-differentiation of the boundary integral equations is performed to obtain the sensitivity equations. The body forces are accounted for by either the particular integrals for uniform body forces or by a surface integration for non-uniform body forces. The corresponding sensitivity equations for both these cases are presented. The validity of present formulations is established through a close agreement with exact analytical results.

Saigal, Sunil; Kane, James H.; Aithal, R.; Cheng, Jizu

1989-01-01

31

Magnetic force microscopy: quantitative issues in biomaterials.  

PubMed

Magnetic force microscopy (MFM) is an atomic force microscopy (AFM) based technique in which an AFM tip with a magnetic coating is used to probe local magnetic fields with the typical AFM spatial resolution, thus allowing one to acquire images reflecting the local magnetic properties of the samples at the nanoscale. Being a well established tool for the characterization of magnetic recording media, superconductors and magnetic nanomaterials, MFM is finding constantly increasing application in the study of magnetic properties of materials and systems of biological and biomedical interest. After reviewing these latter applications, three case studies are presented in which MFM is used to characterize: (i) magnetoferritin synthesized using apoferritin as molecular reactor; (ii) magnetic nanoparticles loaded niosomes to be used as nanocarriers for drug delivery; (iii) leukemic cells labeled using folic acid-coated core-shell superparamagnetic nanoparticles in order to exploit the presence of folate receptors on the cell membrane surface. In these examples, MFM data are quantitatively analyzed evidencing the limits of the simple analytical models currently used. Provided that suitable models are used to simulate the MFM response, MFM can be used to evaluate the magnetic momentum of the core of magnetoferritin, the iron entrapment efficiency in single vesicles, or the uptake of magnetic nanoparticles into cells. PMID:25050758

Passeri, Daniele; Dong, Chunhua; Reggente, Melania; Angeloni, Livia; Barteri, Mario; Scaramuzzo, Francesca A; De Angelis, Francesca; Marinelli, Fiorenzo; Antonelli, Flavia; Rinaldi, Federica; Marianecci, Carlotta; Carafa, Maria; Sorbo, Angela; Sordi, Daniela; Arends, Isabel Wce; Rossi, Marco

2014-01-01

32

Dynamical friction force exerted on spherical bodies  

E-print Network

We present a rigorous calculation of the dynamical friction force exerted on a spherical massive perturber moving through an infinite homogenous system of field stars. By calculating the shape and mass of the polarization cloud induced by the perturber in the background system, which decelerates the motion of the perturber, we recover Chandrasekhar's drag force law with a modified Coulomb logarithm. As concrete examples we calculate the drag force exerted on a Plummer sphere or a sphere with the density distribution of a Hernquist profile. It is shown that the shape of the perturber affects only the exact form of the Coulomb logarithm. The latter converges on small scales, because encounters of the test and field stars with impact parameters less than the size of the massive perturber become inefficient. We confirm this way earlier results based on the impulse approximation of small angle scatterings.

O. Esquivel; B. Fuchs

2007-04-30

33

Quantification of magnetic force microscopy using a micronscale current ring  

E-print Network

Quantification of magnetic force microscopy using a micronscale current ring Linshu Konga magnetic force microscopy MFM . A MFM tip's effective magnetic charge, q, and effective magnetic moment to be 0.1 Oe/nm2 . © 1997 American Institute of Physics. S0003-6951 97 03115-X Magnetic force microscopy

34

How to Classify Three-Body Forces -- and Why  

Microsoft Academic Search

To add 3-body forces when theory and data disagree is untenable when predictions are required. For the ``pion-less'' Effective Field Theory at momenta below the pion-mass, I provide a recipe to systematically estimate the typical size of 3-body forces in all partial waves and orders, including external currents [1]. It is based on the superficial degree of divergence of the

Harald W. Griesshammer

2006-01-01

35

How to Classify Three-Body Forces -- and Why  

Microsoft Academic Search

To add 3-body forces when theory and data disagree is untenable when predictions are required. For the ``pion-less'' Effective Field Theory at momenta below the pion-mass, I provide a recipe to systematically estimate the typical size of 3-body forces in all partial waves and orders, including external currents [1]. It is based on the superficial degree of divergence of the

Harald W. Griesshammer

2007-01-01

36

Levitation forces in bearingless permanent magnet motors  

SciTech Connect

Bearingless motors combine brushless AC-motors with active magnetic bearings by the integration of two separate winding systems (torque and radial levitation force windings with different pole pairs) in one housing. This paper gives an insight into the influences of the motor design on the levitation force and torque generation. It is shown that especially for machines with small air gaps it can be very important to choose the right design parameters. Increasing the permanent magnet height in order to increase the motor torque can result in a remarkable reduction of radial forces. The interrelationships are discussed on the basis of Maxwell and Lorentz forces acting upon the stator surface. The investigations are presented for a bearingless low cost motor, suited for pump, fan or blower applications. The presented motor needs only four coils for operation.

Amrhein, W.; Silber, S.; Nenninger, K.

1999-09-01

37

Modeling Forces on the Human Body.  

ERIC Educational Resources Information Center

Presents five models of the human body as a mechanical system which can be used in introductory physics courses: human arms as levers, humans falling from small heights, a model of the human back, collisions during football, and the rotating gymnast. Gives ideas for discussions and activities, including Interactive Physics (TM) simulations. (WRM)

Pagonis, Vasilis; Drake, Russel; Morgan, Michael; Peters, Todd; Riddle, Chris; Rollins, Karen

1999-01-01

38

Magnetic Force Microscopy Images of Magnetic Garnet With Thin-Film Magnetic Tip  

NASA Technical Reports Server (NTRS)

We present magnetic force microscopy images of YGdTmGa/YSmTmGa magnetic garnet, usinga thin Fe film deposited on Si_3N_5 tips. We have found correlations between the topography andthe magnetic domain structure. We have observed the domain wall contrast with a iron thin-film tip. We report on domain wall imaging of garnet with magnetic force microscopy.

Wadas, A.; Moreland, J.; Rice, P.; Katti, R.

1993-01-01

39

Magnetic Force and Work: An Accessible Example  

ERIC Educational Resources Information Center

Despite their physics instructors' arguments to the contrary, introductory students can observe situations in which there seems to be compelling evidence for magnetic force doing work. The counterarguments are often highly technical and require physics knowledge beyond the experience of novice students, however. A simple example is presented

Gates, Joshua

2014-01-01

40

Many-body effects for critical Casimir forces  

E-print Network

Within mean-field theory we calculate the scaling functions associated with critical Casimir forces for a system consisting of two spherical colloids immersed in a binary liquid mixture near its consolute point and facing a planar, homogeneous substrate. For several geometrical arrangements and boundary conditions we analyze the normal and the lateral critical Casimir forces acting on one of the two colloids. We find interesting features such as a change of sign of these forces upon varying either the position of one of the colloids or the temperature. By subtracting the pairwise forces from the total force we are able to determine the many-body forces acting on one of the colloids. We have found that the many-body contribution to the total critical Casimir force is more pronounced for small colloid-colloid and colloid-substrate distances, as well as for temperatures close to criticality, where the many-body contribution to the total force can reach up to 25%.

T. G. Mattos; L. Harnau; S. Dietrich

2013-01-28

41

A compact high field magnetic force microscope.  

PubMed

We present the design and performance of a simple and compact magnetic force microscope (MFM), whose tip-sample coarse approach is implemented by the piezoelectric tube scanner (PTS) itself. In brief, a square rod shaft is axially spring-clamped on the inner wall of a metal tube which is glued inside the free end of the PTS. The shaft can thus be driven by the PTS to realize image scan and inertial stepping coarse approach. To enhance the inertial force, each of the four outer electrodes of the PTS is driven by an independent port of the controller. The MFM scan head is so compact that it can easily fit into the 52mm low temperature bore of a 20T superconducting magnet. The performance of the MFM is demonstrated by imaging a manganite thin film at low temperature and in magnetic fields up to 15T. PMID:25189114

Zhou, Haibiao; Wang, Ze; Hou, Yubin; Lu, Qingyou

2014-12-01

42

Magnetic forces and DNA mechanics in multiplexed magnetic tweezers.  

PubMed

Magnetic tweezers (MT) are a powerful tool for the study of DNA-enzyme interactions. Both the magnet-based manipulation and the camera-based detection used in MT are well suited for multiplexed measurements. Here, we systematically address challenges related to scaling of multiplexed magnetic tweezers (MMT) towards high levels of parallelization where large numbers of molecules (say 10(3)) are addressed in the same amount of time required by a single-molecule measurement. We apply offline analysis of recorded images and show that this approach provides a scalable solution for parallel tracking of the xyz-positions of many beads simultaneously. We employ a large field-of-view imaging system to address many DNA-bead tethers in parallel. We model the 3D magnetic field generated by the magnets and derive the magnetic force experienced by DNA-bead tethers across the large field of view from first principles. We furthermore experimentally demonstrate that a DNA-bead tether subject to a rotating magnetic field describes a bicircular, Limaon rotation pattern and that an analysis of this pattern simultaneously yields information about the force angle and the position of attachment of the DNA on the bead. Finally, we apply MMT in the high-throughput investigation of the distribution of the induced magnetic moment, the position of attachment of DNA on the beads, and DNA flexibility. The methods described herein pave the way to kilo-molecule level magnetic tweezers experiments. PMID:22870220

De Vlaminck, Iwijn; Henighan, Thomas; van Loenhout, Marijn T J; Burnham, Daniel R; Dekker, Cees

2012-01-01

43

Frequency domain multiplexing of force signals with application to magnetic resonance force microscopy  

E-print Network

Frequency domain multiplexing, using an actively damped micromechanical cantilever, is used to detect multiple force signals simultaneously. The measurement principle is applied to magnetic resonance force microscopy to ...

Degen, Christian

44

Controlling a magnetic force microscope to track a magnetized nanosize particle  

E-print Network

--Nanotechnology, magnetic force microscopy (MFM), nonlinear systems, particle tracking I. INTRODUCTION Magnetic1 Controlling a magnetic force microscope to track a magnetized nanosize particle Dimitar Baronov moving in three-dimensions using a magnetic force microscope (MFM). The stray magnetic field

Andersson, Sean B.

45

Nave dimensional analysis for three-body forces without pions  

Microsoft Academic Search

For systems of three identical particles in which short-range forces produce shallow two-particle bound states, and in particular for the ``pionless'' effective field theory of nuclear physics, I extend and systematise the power-counting of three-body forces to all partial waves and orders, including external currents. With low-energy observables independent of the details of short-distance dynamics, the typical strength of a

Harald W. Griehammer

2005-01-01

46

Nave dimensional analysis for three-body forces without pions  

Microsoft Academic Search

For systems of three identical particles in which short-range forces produce shallow two-particle bound states, and in particular for the pionless effective field theory of nuclear physics, I extend and systematise the power-counting of three-body forces to all partial waves and orders, including external currents. With low-energy observables independent of the details of short-distance dynamics, the typical strength of a

Harald W. Griehammer

2005-01-01

47

Magnetic Resonance Imaging in Lewy Body Dementias  

Microsoft Academic Search

Dementia with Lewy bodies (DLB) and Parkinsons disease dementia (PDD) share common clinical, neuropsychological and pathological features. In clinical diagnosis, distinguishing between these conditions and other dementia subtypes such as Alzheimers disease (AD) can be difficult. Despite the development of consensus diagnostic criteria, sensitivity for diagnosis remains low, especially outside specialist centres. Neuroimaging techniques using magnetic resonance (MR) can assess

Rosie Watson; Andrew M. Blamire; John T. OBrien

2009-01-01

48

Microrheology of cells with magnetic force modulation atomic force microscopy.  

PubMed

We propose a magnetic force modulation method to measure the stiffness and viscosity of living cells using a modified AFM apparatus. An oscillating magnetic field makes a magnetic cantilever oscillate in contact with the sample, producing a small AC indentation. By comparing the amplitude of the free cantilever motion (A0) with the motion of the cantilever in contact with the sample (A1), we determine the sample stiffness and viscosity. To test the method, the frequency-dependent stiffness of 3T3 fibroblasts was determined as a power law k(s)(f) = ? + ?(f/f)(?) (? = 7.6 10(-4) N m(-1), ? = 1.0 10(-4) N m(-1), f = 1 Hz, ? = 0.6), where the coefficient ? = 0.6 is in good agreement with rheological data of actin solutions with concentrations similar to those in cells. The method also allows estimation of the internal friction of the cells. In particular we found an average damping coefficient of 75.1 ?N s m(-1) for indentation depths ranging between 1.0 ?m and 2.0 ?m. PMID:24651941

Reblo, L M; de Sousa, J S; Mendes Filho, J; Schpe, J; Doschke, H; Radmacher, M

2014-04-01

49

Three-body forces and shell structure in calcium isotopes  

E-print Network

Understanding and predicting the formation of shell structure from nuclear forces is a central challenge for nuclear physics. While the magic numbers N=2,8,20 are generally well understood, N=28 is the first standard magic number that is not reproduced in microscopic theories with two-nucleon forces. In this Letter, we show that three-nucleon forces give rise to repulsive interactions between two valence neutrons that are key to explain 48Ca as a magic nucleus, with a high 2+ excitation energy and a concentrated magnetic dipole transition strength. The repulsive three-nucleon mechanism improves the agreement with experimental binding energies.

Jason D. Holt; Takaharu Otsuka; Achim Schwenk; Toshio Suzuki

2012-07-02

50

Estimating the magnetic penetration depth using constant-height magnetic force  

E-print Network

Estimating the magnetic penetration depth using constant-height magnetic force microscopy images November 2001 Published 19 December 2001 Abstract. We present constant-height magnetic force microscopy the application of magnetic force microscopy to determine the magnetic penetration depth of Nb, a conventional

Grütter, Peter

51

Study of magnetic properties of magnetic force microscopy probes using micronscale current rings  

E-print Network

Study of magnetic properties of magnetic force microscopy probes using micronscale current rings, fabricated using electron-beam lithography, were used to calibrate magnetic force microscopy MFM . A MFM tip magnetic force microscopy MFM is an essential tool for characterizing magnetic ma- terials in submicron

52

Novel magnetic tips developed for the switching magnetization magnetic force microscopy.  

SciTech Connect

Using micromagnetic calculations we search for optimal magnetic properties of novel magnetic tips to be used for a Switching Magnetization Magnetic Force Microscopy (SM-MFM), a novel technique based on two-pass scanning with reversed tip magnetization. Within the technique the sum of two scans images local atomic forces and their difference maps the local magnetic forces. The tip magnetization is switched during the scanning by a small magnetic field. The technology of novel low-coercitive magnetic tips is proposed. For best performance the tips must exhibit low magnetic moment, low switching field, and single-domain state at remanence. Such tips are equipped with Permalloy objects of a precise shape that are defined on their tilted sides. We calculate switching fields of such tips by solving the micromagnetic problem to find the optimum shape and dimensions of the Permalloy objects located on the tips. Among them, hexagon was found as the best shape for the tips.

Cambel, V.; Elias, P.; Gregusova, D.; Fedor, J.; Martaus, J.; Karapetrov, G.; Novosad, V.; Kostic, I.; Materials Science Division; Slovak Academy of Sciences

2010-07-01

53

Distinguishing magnetic and electrostatic interactions by a Kelvin probe force microscopymagnetic force microscopy combination  

PubMed Central

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 2550 nm such that the long range tipsample 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 tipsample 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

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

2011-01-01

54

Investigation of many-body forces in krypton and xenon  

SciTech Connect

The simplicity of the state dependence at relatively high temperatures ofthe many-body potential contribution to the pressure and energy has been pointed out previously (J. Ram and P. A. Egelstaff, J. Phys. Chem. Liq. 14, 29 (1984); A. Teitsima and P. A. Egelstaff, Phys. Rev. A 21, 367 (1980)). In this paper, we investigate how far these many-body potential terms may be represented by simple models in the case of krypton on the 423-, 273-, 190-, and 150-K isotherms, and xenon on the 170-, 210-, and 270-K isotherms. At the higher temperatures the best agreement is found for the mean-field type of theory, and some consequences are pointed out. On the lower isotherms a state point is found where the many-body energy vanishes, and large departures from mean-field behavior are observed. This is attributed to the influence of short-ranged many-body forces.

Salacuse, J.J.; Egelstaff, P.A.

1988-10-15

55

Magnetic resonance imaging of the body  

SciTech Connect

This text provides reference to magnetic resonance imaging (MRI) of the body. Beginning with explanatory chapters on the physics, instrumentation, and interpretation of MRI, it proceeds to the normal anatomy of the neck, thorax, abdomen, and pelvis. Other chapters cover magnetic resonance imaging of blood flow, the larynx, the lymph nodes, and the spine, as well as MRI in obstetrics. The text features detailed coverage of magnetic resonance imaging of numerous disorders and disease states, including neck disease, thoracic disease; breast disease; congenital and acquired heart disease; vascular disease; diseases of the liver, pancreas, and spleen; diseases of the kidney, adrenals, and retroperitoneum; diseases of the male and female pelvis; and musculoskeletal diseases. Chapters on the biological and environmental hazards of MRI, the current clinical status of MRI in comparison to other imaging modalities, and economic considerations are also included.

Higgins, C.B.; Hricak, H.

1987-01-01

56

Forced magnetic reconnection in Tokamak plasmas  

NASA Astrophysics Data System (ADS)

This dissertation addresses two related problems in the study of forced magnetic reconnection in Tokamak plasmas. First, a recent controversy concerning a model forced magnetic reconnection problem, the Taylor problem, has been resolved. The criticisms of Ishizawa and Tokuda [21] concerning the original analysis of Hahm and Kulsrud [17] are shown to be unwarranted, both analytically and numerically. Second, one possible reason for the discrepancy between recent experimental [29] and previous theoretical [13] scaling of the critical error-field penetration threshold with device parameters is addressed. The theory in question is entirely based on a single-fluid MHD (magnetohydrodynamical) treatment of the plasma. As is well-known, high temperature plasmas are far better modeled using the drift-MHD ordering.[18] Hence we develop a drift-MHD theory of error-field penetration. Although two new drift-MHD plasma response regimes are identified, the overall threshold scaling with device parameters is not altogether different from that predicted by single-fluid MHD.

Cole, Andrew Joseph

57

Optical fibre bragg gratings based magnetic force measurement of magnetic bearings  

Microsoft Academic Search

Magnetic bearings are typical electromechanical systems of high performance. Current-displacement-force relationship between stator and rotor is an important research topic of magnetic bearings. The critical issue is to realize magnetic force online dynamic measurement. This paper presents a novel method on magnetic force measurement of magnetic bearings with optical fibre bragg gratings (FBG), which realizes a non-contact and online force

Guoping Ding; Zude Zhou; Yefa Hu; Jianhua Zhou

2008-01-01

58

Magnetic dissipation force microscopy P. Grutter,a)  

E-print Network

Magnetic dissipation force microscopy P. Gru¨tter,a) Y. Liu, and P. LeBlanc Department of Physics American Institute of Physics. S0003-6951 97 01428-9 In magnetic force microscopy MFM , the interaction; accepted for publication 6 May 1997 A method of measuring magnetic dissipation on a sub-100 nm scale

Grütter, Peter

59

Exchange Bias Systems studied by High Resolution Quantitative Magnetic Force  

E-print Network

Exchange Bias Systems studied by High Resolution Quantitative Magnetic Force Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2 Introduction to Quantitative MFM 12 2.1 Magnetic Force Microscope study F/AF heterostructure-samples by VSM and quantitative, high resolution MFM. MFM works in magnetic

Amrhein, Valentin

60

Muscle force redistributes segmental power for body progression during walking.  

PubMed

The ankle plantar flexors were previously shown to support the body in single-leg stance to ensure its forward progression [J. Biomech. 34 (2001) 1387]. The uni- (SOL) and biarticular (GAS) plantar flexors accelerated the trunk and leg forward, respectively, with each opposing the effect of the other. Around mid-stance their net effect on the trunk and the leg was negligible, consistent with the body acting as an inverted pendulum. In late stance, their net effect was to accelerate the leg and trunk forward, consistent with an active push-off. Because other muscles are active in the beginning and end of stance, we hypothesized that their active concentric and eccentric force generation also supports the body and redistributes segmental power to enable body forward progression. Muscle-actuated forward dynamical simulations that emulated observed walking kinematics and kinetics of young adult subjects were analyzed to quantify muscle contributions to the vertical and horizontal ground reaction force, and to the acceleration and mechanical power of the leg and trunk. The eccentric uniarticular knee extensors (vasti, VAS) and concentric uniarticular hip extensors (gluteus maximus, GMAX) were found to provide critical support to the body in the beginning of stance, before the plantar flexors became active. VAS also decelerated the forward motion of both the trunk and the leg. Afterwards when VAS shortens in mid-stance, it delivered the power produced to accelerate the trunk and also redistributed segmental power to the trunk by continuing to decelerate the leg. When present, rectus femoris (RF) activity in the beginning of stance had a minimal effect. But in late stance the lengthening RF accelerated the knee and hip into extension, which opposed swing initiation. Though RF was lengthening, it still accelerated the trunk forward by decelerating the leg and redistributing the leg segmental power to the trunk, as SOL does though it is shortening instead of lengthening. Force developed from highly stretched passive hip structures and active force produced by the uniarticular hip flexors assisted GAS in swing initiation. Hamstrings (HAM) decelerated the leg in late swing while lengthening and accelerated the leg in the beginning of stance while shortening. We conclude that the uniarticular knee and hip extensor muscles are critical to body support in the beginning of stance and redistribution of segmental power by muscles throughout the gait cycle is critical to forward progression of the trunk and legs. PMID:15013508

Neptune, R R; Zajac, F E; Kautz, S A

2004-04-01

61

Electric and Magnetic Forces between Parallel-Wire Conductors.  

ERIC Educational Resources Information Center

Discusses electric and magnetic forces between parallel-wire conductors and derives, in a simple fashion, order of magnitude estimates of the ratio of the likely electrostatic and electromagnetic forces for a simple parallel-wire balance. (Author/HM)

Morton, N.

1979-01-01

62

Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy  

Microsoft Academic Search

Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. Here we describe these techniques and illustrate them with examples highlighting current capabilities and limitations.

Attila Nagy; Keir C Neuman

2008-01-01

63

Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy  

PubMed Central

Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. These techniques are described and illustrated with examples highlighting current capabilities and limitations. PMID:18511917

Neuman, Keir C.; Nagy, Attila

2012-01-01

64

May the Magnetic Force Be with You  

ERIC Educational Resources Information Center

Although most elementary students have had experiences with magnets, they generally have misconceptions about magnetism (Driver et al. 1994; Burgoon, Heddle, and Duran 2010). For example, students may think magnets can attract all metals or that larger magnets are stronger than smaller magnets. Students often confuse magnets with magnetic

Wilcox, Jesse; Richey, Lindsey R.

2012-01-01

65

Origin of the short-range part of generalized two- and three-body nuclear force  

NASA Astrophysics Data System (ADS)

Origin of the short-range baryon-baryon interactions is discussed from the quark substructure viewpoints of baryons. It is pointed out that the generalized nuclear force, recently obtained from the lattice QCD calculations, can be interpreted at short distances by the combinatory effects of the Pauli exclusion principle and the color-magnetic spin-spin interactions among the quarks. Classifications according to the spin-flavor SU(6) symmetry representations give us a general guidance on the features of the short-range interactions. The SU(6) analysis of the three-body baryon interactions reveals that the genuine three-body force is repulsive at short distances due to the quark antisymmetrization.

Oka, Makoto

2012-05-01

66

Magnetic imaging and dissipation force microscopy of vortices on superconducting Nb films  

E-print Network

Magnetic imaging and dissipation force microscopy of vortices on superconducting Nb films M: Magnetic force microscopy; Dissipation force microscopy; Superconducting film; Vortex state Abstract Constant height imaging using a custom built low temperature magnetic force microscope has been

Grütter, Peter

67

Spin-motive force due to a gyrating magnetic vortex.  

PubMed

A change of magnetic flux through a circuit induces an electromotive force. By analogy, a recently predicted force that results from the motion of non-uniform spin structures has been termed the spin-motive force. Although recent experiments seem to confirm its presence, a direct signature of the spin-motive force has remained elusive. Here we report the observation of a real-time spin-motive force produced by the gyration of a magnetic vortex core. We find a good agreement between the experimental results, theory and micromagnetic simulations, which taken as a whole provide strong evidence in favour of a spin-motive force. PMID:22617285

Tanabe, K; Chiba, D; Ohe, J; Kasai, S; Kohno, H; Barnes, S E; Maekawa, S; Kobayashi, K; Ono, T

2012-01-01

68

Floating body second order slow drift force spectrum  

SciTech Connect

In this paper it is shown that the slow drift force spectrum of a floating body, obtained from the quadratic transfer function, can be approximated, in the range of interest ({mu} {much_lt} 1) by a white noise of the form S{sub F}({mu}) = S{sub F}(0) + O({mu}{sup 2}) where S{sub F}(0) can be computed from the known drift force coefficient in harmonic waves and the wave energy spectrum. It is also shown here that a special and normally used form of Newman`s approximation represents the spectrum S{sub F}({mu}) with an error [1 + O({mu}{sup 2})] in the low frequency regime. It is also shown that a well chosen Newman`s Approximations may be O({mu}{sup 2}) instead of only O({mu}).

Aranha, J.A.P. [Univ. of Sao Paulo (Brazil). Dept. of Naval Architecture and Ocean Engineering; Fernandes, A.C. [PETROBRAS, E and P/GETINP/GESEM, Rio de Janeiro (Brazil)

1996-12-31

69

Superadiabatic Forces in Brownian Many-Body Dynamics  

NASA Astrophysics Data System (ADS)

Theoretical approaches to nonequilibrium many-body dynamics generally rest upon an adiabatic assumption, whereby the true dynamics is represented as a sequence of equilibrium states. Going beyond this simple approximation is a notoriously difficult problem. For the case of classical Brownian many-body dynamics, we present a simulation method that allows us to isolate and precisely evaluate superadiabatic correlations and the resulting forces. Application of the method to a system of one-dimensional hard particles reveals the importance for the dynamics, as well as the complexity, of these nontrivial out-of-equilibrium contributions. Our findings help clarify the status of dynamical density functional theory and provide a rational basis for the development of improved theories.

Fortini, Andrea; de las Heras, Daniel; Brader, Joseph M.; Schmidt, Matthias

2014-10-01

70

Journal of Magnetism and Magnetic Materials 286 (2005) 324328 Light-free magnetic resonance force microscopy for studies of  

E-print Network

Journal of Magnetism and Magnetic Materials 286 (2005) 324­328 Light-free magnetic resonance force for Physical Sciences, College Park, MD, USA Available online 4 November 2004 Abstract Magnetic resonance force microscopy is a scanned probe technique capable of three-dimensional magnetic resonance imaging. Its

71

Drag measurements on a body of revolution in Langley's 13-inch Magnetic Suspension and Balance System  

NASA Technical Reports Server (NTRS)

NASA Langley's 13-inch Magnetic Suspension and Balance System (MSBS) has been used to conduct low-speed wind tunnel drag force measurements on a laminar-flow body-of-revolution free of support system interference, in order to verify the drag force measurement capabilities of the MSBS. The drag force calibrations and wind-on repeatability data obtained have verified the design capabilities for this system. A drag-prediction code has been used to assess the MSBS's usefulness in body drag estimation.

Dress, David A.

1988-01-01

72

Magnetic Force Microscopy Imaging of the Magnetic Domains in Co Y-branch Structures  

E-print Network

UG-23 Magnetic Force Microscopy Imaging of the Magnetic Domains in Co Y Force Microscopy (MFM) to measure the relative attraction/repulsion between the tip and sample, which the various magnetic domains in the Cobalt Y-branch structure resulting from different external magnetic

73

A 3D Magnetic Force Manipulator DC Prototype  

E-print Network

of utilize a microscopic bead as a mechanical probe, the position of which can be sensed, and the forceA 3D Magnetic Force Manipulator DC Prototype Leandra Vicci Microelectronic Systems Laboratory effects on in-vivo experiments. Alternatively, magnetic techniques use a mag- netic bead driven by low

North Carolina at Chapel Hill, University of

74

The measurement of Magnus force and moment using a magnetically suspended wind tunnel model  

Microsoft Academic Search

The magnetic suspension system makes an ideal facility for the measurement of the aerodynamic Magnus force acting on a wind tunnel model which is spinning about an axis inclined at an angle to the air flow. The Southampton University system was modified to allow the suspended model freedom to spin whilst retaining control of the other rigid body degrees of

M. Goodyer; R. Henderson; M. Judd

1975-01-01

75

Magnetic Forces and Field Line Density  

NSDL National Science Digital Library

This is an activity about depicting the relative strength of magnetic fields using field line density. Learners will use the magnetic field line drawing of six magnetic poles created in a previous activity and identify the areas of strong, weak, and medium magnetic intensity using the density of magnetic field lines. This is the fifth activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website. How to Draw Magnetic Fields - II in the Magnetic Math booklet must be completed prior to this activity.

76

MAGNETIC HELICITY OF SELF-SIMILAR AXISYMMETRIC FORCE-FREE FIELDS  

SciTech Connect

In this paper, we continue our theoretical studies addressing the possible consequences of magnetic helicity accumulation in the solar corona. Our previous studies suggest that coronal mass ejections (CMEs) are natural products of coronal evolution as a consequence of magnetic helicity accumulation and that the triggering of CMEs by surface processes such as flux emergence also have their origin in magnetic helicity accumulation. Here, we use the same mathematical approach to study the magnetic helicity of axisymmetric power-law force-free fields but focus on a family whose surface flux distributions are defined by self-similar force-free fields. The semi-analytical solutions of the axisymmetric self-similar force-free fields enable us to discuss the properties of force-free fields possessing a huge amount of accumulated magnetic helicity. Our study suggests that there may be an absolute upper bound on the total magnetic helicity of all bipolar axisymmetric force-free fields. With the increase of accumulated magnetic helicity, the force-free field approaches being fully opened up with Parker-spiral-like structures present around a current-sheet layer as evidence of magnetic helicity in the interplanetary space. It is also found that among the axisymmetric force-free fields having the same boundary flux distribution, the one that is self-similar is the one possessing the maximum amount of total magnetic helicity. This gives a possible physical reason why self-similar fields are often found in astrophysical bodies, where magnetic helicity accumulation is presumably also taking place.

Zhang Mei [Key Laboratory of Solar Activity, National Astronomical Observatory, Chinese Academy of Sciences, Datun Road A20, Chaoyang District, Beijing 100012 (China); Flyer, Natasha [Institute for Mathematics Applied to Geosciences, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States); Low, Boon Chye [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States)

2012-08-10

77

Distortion of magnetic field and magnetic force of a brushless dc motor due to deformed rubber magnet  

NASA Astrophysics Data System (ADS)

This paper investigates the distortion of magnetic field of a brushless dc (BLDC) motor due to deformed rubber magnet. Global or local deformation of rubber magnet in the BLDC motor is mathematically modeled by using the Fourier series. Distorted magnetic field is calculated by using the finite element method, and unbalanced magnetic force is calculated by using the Maxwell stress tensor. When the rubber magnet is globally or locally deformed, the unbalanced magnetic force has the frequencies with the first harmonic and the harmonics of slot number 1. However, the harmonic deformation with multiple of common divisor of pole and slot does not generate unbalanced magnetic force due to the rotational symmetry.

Lee, C. J.; Jang, G. H.

2008-04-01

78

Power dissipation and magnetic forces and MAGLEV rebars  

SciTech Connect

Concrete guideways for proposed MAGLEV vehicles may be reinforced with electrically conducting and magnetizable steel rebars. Transient magnetic fields due to passing MAGLEV vehicles will then induce transient currents in the rebars leading to power dissipation and temperature rise as well as Lorentz and magnetization forces on the rebars. In order to evaluate if this heating and force on the rebars affects concrete life and performance, analysis is presented for an infinitely long conducting and magnetizable cylinder in imposed uniform axial or transverse magnetic fields. Exact and approximate solutions are presented for sinusoidal steady state and step transient magnetic fields inside and outside the cylinder, the induced current density, the vector potential for transverse magnetic fields, the time average dissipated power in the sinusoidal steady state, and the total energy dissipated for step transients. Forces are approximately calculated for imposed magnetic fields` with a weak spatial gradient. The analysis is applied to representative rebar materials.

Zahn, M. [Massachusetts Inst. of Tech., Cambridge, MA (United States)] [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1997-03-01

79

Nonconservative electric and magnetic optical forces on submicron dielectric particles  

SciTech Connect

We present a study of the total force on a small lossless dielectric particle, which presents both an electric and magnetic response, in a optical vortex wave field. We show that the force is a simple combination of conservative and nonconservative steady forces that can rectify the flow of magnetodielectric particles. In a vortex lattice the electric-magnetic dipolar interaction can spin the particles either in or out of the whirl sites leading to trapping or diffusion. Specifically, we analyze force effects on submicron silicon spheres in the near infrared, proving that the results previously discussed for hypothetical magnetodielectric particles can be observed for these Si particles.

Gomez-Medina, Raquel; Nieto-Vesperinas, Manuel [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Campus de Cantoblanco, Madrid E-28049 (Spain); Saenz, Juan Jose [Departamento de Fisica de la Materia Condensada, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Donostia International Physics Center (DIPC), Paseo Manuel Lardizabal 4, 20018 Donostia-San Sebastian (Spain)

2011-03-15

80

ENSC 283: Center of Pressure and Hydrostatic Force on a submerged body School of Engineering Science  

E-print Network

ENSC 283: Center of Pressure and Hydrostatic Force on a submerged body 1 School of Engineering and bottom faces are concentric circular arcs centered on the pivot so that the resultant hydrostatic force of the apparatus. #12;ENSC 283: Center of Pressure and Hydrostatic Force on a submerged body 2 School

Bahrami, Majid

81

MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS B. Fornberg,2  

E-print Network

MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS N. Flyer,1 B Axisymmetric force-free magnetic fields external to a unit sphere are studied as solutions to boundary value against expansion into the unbounded space. This property as a basic mechanism for solar coronal mass

Fornberg, Bengt

82

Forced heat loss from body surface reduces heat flow to body surface.  

PubMed

Heat stress is commonly relieved by forced evaporation from body surfaces. The mode of heat stress relief by heat extraction from the periphery is not clear, although it reduces rectal temperature. Radiant surface temperature (Ts) of the right half of the body surface was examined by thermovision in 4 lactating Holstein cows (30 kg of milk/d) during 7 repeated cycles of forced evaporation created by 30s of wetting followed by 4.5 min of forced airflow. Wetting was performed by an array of sprinklers (0.76 m(3)/h), and forced airflow (>3m/s velocity) over the right side of the body surface was produced by fans mounted at a height of 3m above the ground. Sprinkling wetted the hind legs, rump, and chest, but not the lower abdomen side, front legs, or neck. The animals were maintained in shade at an air temperature of 28 degrees C and relative humidity of 47%. Coat thickness was 1 to 2mm, so Ts closely represented skin temperature. Mean Ts of 5 x 20cm areas on the upper and lower hind and front legs, rump, chest, abdomen side, and neck were obtained by converting to temperature their respective gray intensity in single frames obtained at 10-s intervals. Little change occurred in Ts during the first wetting (0.1+/-0.6 degrees C), but it decreased rapidly thereafter (1.6+/-0.6 degrees C in the fifth wetting). The Ts also decreased, to a smaller extent, in areas that remained dry (0.7+/-1.0 degrees C). In all body sites, a plateau in Ts was reached by 2 min after wetting. The difference between dry and wet areas in the first cooling cycle was approximately 1.2 degrees C. The Ts of different body areas decreased during consecutive cooling cycles and reached a plateau by 3 cooling cycles in dry sites (front leg, neck, abdomen side), by 5 cooling cycles in the hind leg, and 7 cooling cycles in the rump and chest. The reduction in mean Ts produced by 7 cycles was 4.0 to 6.0 degrees C in wetted areas and 1.6 to 3.7 degrees C in sites that were not wetted. Initial rectal temperature was 38.9+/-0.1 degrees C; it remained unchanged during first 5 cooling cycles, decreased by 0.1 degrees C after 7 cooling cycles, and decreased to 38.4+/-0.06 degrees C after 8 to 10 cooling cycles, with no additional subsequent decrease. The concomitant reduction in Ts in dry and wet areas suggests an immediate vasoconstrictor response associated with heat extraction and later development of a cooler body shell. The reduction in rectal temperature represents a response involving transfer of heat from the body core to the body shell. This response mode requires consideration in settings of heat stress relief. PMID:20059922

Berman, A

2010-01-01

83

Optical fibre bragg gratings based magnetic force measurement of magnetic bearings  

NASA Astrophysics Data System (ADS)

Magnetic bearings are typical electromechanical systems of high performance. Current-displacement-force relationship between stator and rotor is an important research topic of magnetic bearings. The critical issue is to realize magnetic force online dynamic measurement. This paper presents a novel method on magnetic force measurement of magnetic bearings with optical fibre bragg gratings (FBG), which realizes a non-contact and online force measurement with simple configuration, good noise immunity even when the rotor is running. A novel micro force transducer is designed and fabricated, which is mounted within the stator magnetic pole. To obtain current-displacement-force relationship a FBG based magnetic force measurement test rig is setup to simulate magnetic bearing working states as the stator coils currents, air gap between stator and rotor, rotor speed is adjustable. Magnetic force is measured under three classifications of test conditions and test results are presented. The measurement data show good consistency with the theory analysis and calculation, which means that the FBG based magnetic force measurement is available and of good accuracy.

Ding, Guoping; Zhou, Zude; Hu, Yefa; Zhou, Jianhua

2008-12-01

84

Mitigated-force carriage for high magnetic field environments  

DOEpatents

A carriage for high magnetic field environments includes a first work-piece holding means for holding a first work-piece, the first work-piece holding means being disposed in an operable relationship with a work-piece processing magnet having a magnetic field strength of at least 1 Tesla. The first work-piece holding means is further disposed in operable connection with a second work-piece holding means for holding a second work-piece so that, as the first work-piece is inserted into the magnetic field, the second work-piece is simultaneously withdrawn from the magnetic field, so that an attractive magnetic force imparted on the first work-piece offsets a resistive magnetic force imparted on the second work-piece.

Ludtka, Gerard M; Ludtka, Gail M; Wilgen, John B; Murphy, Bart L

2014-05-20

85

Electromotive force and huge magnetoresistance in magnetic tunnel junctions.  

PubMed

The electromotive force (e.m.f.) predicted by Faraday's law reflects the forces acting on the charge, -e, of an electron moving through a device or circuit, and is proportional to the time derivative of the magnetic field. This conventional e.m.f. is usually absent for stationary circuits and static magnetic fields. There are also forces that act on the spin of an electron; it has been recently predicted that, for circuits that are in part composed of ferromagnetic materials, there arises an e.m.f. of spin origin even for a static magnetic field. This e.m.f. can be attributed to a time-varying magnetization of the host material, such as the motion of magnetic domains in a static magnetic field, and reflects the conversion of magnetic to electrical energy. Here we show that such an e.m.f. can indeed be induced by a static magnetic field in magnetic tunnel junctions containing zinc-blende-structured MnAs quantum nanomagnets. The observed e.m.f. operates on a timescale of approximately 10(2)-10(3) seconds and results from the conversion of the magnetic energy of the superparamagnetic MnAs nanomagnets into electrical energy when these magnets undergo magnetic quantum tunnelling. As a consequence, a huge magnetoresistance of up to 100,000 per cent is observed for certain bias voltages. Our results strongly support the contention that, in magnetic nanostructures, Faraday's law of induction must be generalized to account for forces of purely spin origin. The huge magnetoresistance and e.m.f. may find potential applications in high sensitivity magnetic sensors, as well as in new active devices such as 'spin batteries'. PMID:19270681

Pham, Nam Hai; Ohya, Shinobu; Tanaka, Masaaki; Barnes, Stewart E; Maekawa, Sadamichi

2009-03-26

86

Many-body central force potentials for tungsten  

NASA Astrophysics Data System (ADS)

Tungsten and tungsten-based alloys are the primary candidate materials for plasma facing components in fusion reactors. The exposure to high-energy radiation, however, severely degrades the performance and lifetime limits of the in-vessel components. In an effort to better understand the mechanisms driving the materials' degradation at the atomic level, large-scale atomistic simulations are performed to complement experimental investigations. At the core of such simulations lies the interatomic potential, on which all subsequent results hinge. In this work we review 19 central force many-body potentials and benchmark their performance against experiments and density functional theory (DFT) calculations. As basic features we consider the relative lattice stability, elastic constants and point-defect properties. In addition, we also investigate extended lattice defects, namely: free surfaces, symmetric tilt grain boundaries, the 1/2<1?1?1>{1?1?0} and 1/2<1?1?1> {1?1?2} stacking fault energy profiles and the 1/2<1?1?1> screw dislocation core. We also provide the Peierls stress for the 1/2<1?1?1> edge and screw dislocations as well as the glide path of the latter at zero Kelvin. The presented results serve as an initial guide and reference list for both the modelling of atomically-driven phenomena in bcc tungsten, and the further development of its potentials.

Bonny, G.; Terentyev, D.; Bakaev, A.; Grigorev, P.; Van Neck, D.

2014-07-01

87

Sensitive magnetic force detection with a carbon nanotube resonator  

SciTech Connect

We propose a technique for sensitive magnetic point force detection using a suspended carbon nanotube (CNT) mechanical resonator combined with a magnetic field gradient generated by a ferromagnetic gate electrode. Numerical calculations of the mechanical resonance frequency show that single Bohr magneton changes in the magnetic state of an individual magnetic molecule grafted to the CNT can translate to detectable frequency shifts, on the order of a few kHz. The dependences of the resonator response to device parameters such as length, tension, CNT diameter, and gate voltage are explored and optimal operating conditions are identified. A signal-to-noise analysis shows that, in principle, magnetic switching at the level of a single Bohr magneton can be read out in a single shot on timescales as short as 10??s. This force sensor should enable new studies of spin dynamics in isolated single molecule magnets, free from the crystalline or ensemble settings typically studied.

Willick, Kyle [Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Haapamaki, Chris [Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Baugh, Jonathan, E-mail: baugh@iqc.ca [Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

2014-03-21

88

Fundamental study of phosphor separation by controlling magnetic force  

NASA Astrophysics Data System (ADS)

The phosphor wastes consist of phosphors with different emission colors, green (LAP), red (YOX), blue (BAM) and white (HP). It is required to recover and reuse the rare earth phosphors with high market value. In this study, we tried to separate the phosphor using the magnetic separation by HTS bulk magnet utilizing the differences of magnetic susceptibility by the type of phosphors. We succeeded in the successive separation of HP with low market value from YOX and BAM including the rare earth using the magnetic Archimedes method. In this method, vertical and radial components of the magnetic force were used.

Wada, Kohei; Mishima, Fumihito; Akiyama, Yoko; Nishijima, Shigehiro

2013-11-01

89

Force Measurements in Magnetic Suspension and Balance System  

NASA Technical Reports Server (NTRS)

The description of an infrared telemetry system for measurement of drag forces in Magnetic Suspension and Balance Systems (MSBS) is presented. This system includes a drag force sensor, electronic pack and transmitter placed in the model which is of special construction, and receiver with a microprocessor-based measuring device, placed outside of the test section. Piezosensitive resonators as sensitive elements and non-magnetic steel as the material for the force sensor are used. The main features of the proposed system for load measurements are discussed and the main characteristics are presented.

Kuzin, Alexander; Shapovalov, George; Prohorov, Nikolay

1996-01-01

90

Critical Casimir forces in a magnetic system: An experimental protocol  

NASA Astrophysics Data System (ADS)

We numerically test an experimentally realizable method for the extraction of the critical Casimir force based on its thermodynamic definition as the derivative of the excess free energy with respect to system size. Free energy differences are estimated for different system sizes by integrating the order parameter along an isotherm. The method could be developed for experiments on magnetic systems and could give access to the critical Casimir force for any universality class. By choosing an applied field that opposes magnetic ordering at the boundaries, the Casimir force is found to increase by an order of magnitude over zero-field results.

Lopes Cardozo, David; Jacquin, Hugo; Holdsworth, Peter C. W.

2014-11-01

91

A Model for Quantum Jumps in Magnetic Resonance Force Microscopy  

E-print Network

We propose a simple model which describes the statistical properties of quantum jumps in a single-spin measurement using the oscillating cantilever-driven adiabatic reversals technique in magnetic resonance force microscopy. Our computer simulations based on this model predict the average time interval between two consecutive quantum jumps and the correlation time to be proportional to the characteristic time of the magnetic noise and inversely proportional to the square of the magnetic noise amplitude.

G. P. Berman; F. Borgonovi; V. I. Tsifrinovich

2004-02-09

92

A Model for Quantum Jumps in Magnetic Resonance Force Microscopy  

E-print Network

We propose a simple model which describes the statistical properties of quantum jumps in a single-spin measurement using the oscillating cantilever-driven adiabatic reversals technique in magnetic resonance force microscopy. Our computer simulations based on this model predict the average time interval between two consecutive quantum jumps and the correlation time to be proportional to the characteristic time of the magnetic noise and inversely proportional to the square of the magnetic noise amplitude.

Berman, G P; Tsifrinovich, V I

2004-01-01

93

A magnetic gradient induced force in NMR restricted diffusion experiments  

SciTech Connect

We predict that the phase cancellation of a precessing magnetisation field carried by a diffusing species in a bounded geometry under certain nuclear magnetic resonance pulsed magnetic field gradient sequences results in a small force over typically micrometre length scales. Our calculations reveal that the total magnetisation energy in a pore under the influence of a pulsed gradient will be distance-dependent thus resulting in a force acting on the boundary. It is shown that this effect of the magnetisation of diffusing particles will appear as either an attractive or repulsive force depending on the geometry of the pore and magnetic properties of the material. A detailed analysis is performed for the case of a pulsed gradient spin-echo experiment on parallel planes. It is shown that the force decays exponentially in terms of the spin-spin relaxation. The proof is based on classical electrodynamics. An application of this effect to soft matter is suggested.

Ghadirian, Bahman; Stait-Gardner, Tim; Castillo, Reynaldo; Price, William S., E-mail: w.price@uws.edu.au [Nanoscale Organisation and Dynamics Group, University of Western Sydney, Penrith, NSW 2751 (Australia)

2014-03-28

94

Bld10/Cep135 stabilizes basal bodies to resist cilia-generated forces  

PubMed Central

Basal bodies nucleate, anchor, and organize cilia. As the anchor for motile cilia, basal bodies must be resistant to the forces directed toward the cell as a consequence of ciliary beating. The molecules and generalized mechanisms that contribute to the maintenance of basal bodies remain to be discovered. Bld10/Cep135 is a basal body outer cartwheel domain protein that has established roles in the assembly of nascent basal bodies. We find that Bld10 protein first incorporates stably at basal bodies early during new assembly. Bld10 protein continues to accumulate at basal bodies after assembly, and we hypothesize that the full complement of Bld10 is required to stabilize basal bodies. We identify a novel mechanism for Bld10/Cep135 in basal body maintenance so that basal bodies can withstand the forces produced by motile cilia. Bld10 stabilizes basal bodies by promoting the stability of the A- and C-tubules of the basal body triplet microtubules and by properly positioning the triplet microtubule blades. The forces generated by ciliary beating promote basal body disassembly in bld10? cells. Thus Bld10/Cep135 acts to maintain the structural integrity of basal bodies against the forces of ciliary beating in addition to its separable role in basal body assembly. PMID:23115304

Bayless, Brian A.; Giddings, Thomas H.; Winey, Mark; Pearson, Chad G.

2012-01-01

95

Dual-tip magnetic force microscopy with suppressed influence on magnetically soft samples.  

PubMed

Standard magnetic force microscopy (MFM) is considered as a powerful tool used for magnetic field imaging at nanoscale. The method consists of two passes realized by the magnetic tip. Within the first one, the topography pass, the magnetic tip directly touches the magnetic sample. Such contact perturbs the magnetization of the sample explored. To avoid the sample touching the magnetic tip, we present a new approach to magnetic field scanning by segregating the topological and magnetic scans with two different tips located on a cut cantilever. The approach minimizes the disturbance of sample magnetization, which could be a major problem in conventional MFM images of soft magnetic samples. By cutting the cantilever in half using the focused ion beam technique, we create one sensor with two different tips-one tip is magnetized, and the other one is left non-magnetized. The non-magnetized tip is used for topography and the magnetized one for the magnetic field imaging. The method developed we call dual-tip magnetic force microscopy (DT-MFM). We describe in detail the dual-tip fabrication process. In the experiments, we show that the DT-MFM method reduces significantly the perturbations of the magnetic tip as compared to the standard MFM method. The present technique can be used to investigate microscopic magnetic domain structures in a variety of magnetic samples and is relevant in a wide range of applications, e.g., data storage and biomedicine. PMID:25586704

Precner, Marin; Fedor, Jn; olts, Jn; Cambel, Vladimr

2015-02-01

96

Dual-tip magnetic force microscopy with suppressed influence on magnetically soft samples  

NASA Astrophysics Data System (ADS)

Standard magnetic force microscopy (MFM) is considered as a powerful tool used for magnetic field imaging at nanoscale. The method consists of two passes realized by the magnetic tip. Within the first one, the topography pass, the magnetic tip directly touches the magnetic sample. Such contact perturbs the magnetization of the sample explored. To avoid the sample touching the magnetic tip, we present a new approach to magnetic field scanning by segregating the topological and magnetic scans with two different tips located on a cut cantilever. The approach minimizes the disturbance of sample magnetization, which could be a major problem in conventional MFM images of soft magnetic samples. By cutting the cantilever in half using the focused ion beam technique, we create one sensor with two different tipsone tip is magnetized, and the other one is left non-magnetized. The non-magnetized tip is used for topography and the magnetized one for the magnetic field imaging. The method developed we call dual-tip magnetic force microscopy (DT-MFM). We describe in detail the dual-tip fabrication process. In the experiments, we show that the DT-MFM method reduces significantly the perturbations of the magnetic tip as compared to the standard MFM method. The present technique can be used to investigate microscopic magnetic domain structures in a variety of magnetic samples and is relevant in a wide range of applications, e.g., data storage and biomedicine.

Precner, Marin; Fedor, Jn; olts, Jn; Cambel, Vladimr

2015-02-01

97

Electrical body forces and electrical tractions in the nonlinear response of ferroelectric actuators  

Microsoft Academic Search

The influence of the electrical body forces and electrical tractions on the nonlinear response of ferroelectric stack actuators is analytically investigated. While the role of the electrical body forces and tractions in the response of piezoelectric actuators is well documented (and in many cases is not significant), the questions of their effect on ferroelectric active materials is still of interest.

Uri Kushnir; Oded Rabinovitch

2011-01-01

98

Magnetic foreign body on the nasal septum.  

PubMed

A 9-year-old boy presented to our department 8 days after attempting to insert a non-piercing magnetic ear stud on either side of his nose. He had been unable to remove them, and both magnetic parts of the ear studs were still present in his nose. Examination of the nose was difficult, as he was unco-operative and his nose was filled with mucus and crusts. X-rays of the nose revealed the two ear studs on either side of the nasal septum (Fig. 1). The magnets had caused compression and thinning of the septal cartilage. Examination under general anaesthesia revealed the two magnets embedded into the mucosa across the septum. The magnets were removed under general anaesthesia by clamping and sliding them in opposite directions. The exposed compressed cartilage was gradually covered by granulation tissue and eventually nasal mucosa. PMID:18069584

Jonas, N E; Meyer, E

2007-11-01

99

Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic  

E-print Network

Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy force microscopy (AFM), micro-needle manipulation1, biomembrane force probe2 and flow-induced stretching

Ritort, Felix

100

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

PubMed

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

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

2014-01-01

101

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

PubMed Central

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

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

2014-01-01

102

Secular changes in body dimensions of Royal Australian Air Force aircrew (19712005)  

Microsoft Academic Search

The aim of this study was to quantify the secular changes in body dimensions of Royal Australian Air Force aircrew. Following corrections for methodological differences, two samples (matched for age and overall body size) of male aircrew measured in 1971 (n=220) and 2005 (n=220) were compared across 13 absolute and proportional body dimensions. Changes in means were expressed as standardised

Grant R. Tomkinson; Adam J. Clark; Peter Blanchonette

2010-01-01

103

Forced oscillations in magnetized accretion disks and QPOs  

E-print Network

We propose a new model for these QPOs based on forced oscillations induced in the accretion disk due to the stellar magnetic field. First, it is shown that a magnetized accretion disk evolving in a rotating nonaxisymmetric magnetic field anchored to a neutron star will be subject to three kinds of resonances: a corotation resonance, a Lindblad resonance due to a driving force, and a parametric resonance due to the time varying epicyclic frequencies. In the second part of the paper, we focus on the linear response of a thin accretion disk, developing the density perturbation as the sum of free wave solutions and non-wavelike disturbances. In the last part, we show results of 2D numerical simulations of a simplified version of the accretion disk consisting of a column of plasma threaded by a vertical magnetic field. It is argued that the nearly periodic motion induced in the disk will produce high quality factor QPOs.

J. Ptri

2005-07-06

104

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

105

Magnetoelectric force microscopy based on magnetic force microscopy with modulated electric field.  

PubMed

We present the realization of a mesoscopic imaging technique, namely, the Magnetoelectric Force Microscopy (MeFM), for visualization of local magnetoelectric effect. The basic principle of MeFM is the lock-in detection of local magnetoelectric response, i.e., the electric field-induced magnetization, using magnetic force microscopy. We demonstrate MeFM capability by visualizing magnetoelectric domains on single crystals of multiferroic hexagonal manganites. Results of several control experiments exclude artifacts or extrinsic origins of the MeFM signal. The parameters are tuned to optimize the signal to noise ratio. PMID:24880381

Geng, Yanan; Wu, Weida

2014-05-01

106

Multiplexed Single-molecule Force Proteolysis Measurements Using Magnetic Tweezers  

PubMed Central

The generation and detection of mechanical forces is a ubiquitous aspect of cell physiology, with direct relevance to cancer metastasis1, atherogenesis2 and wound healing3. In each of these examples, cells both exert force on their surroundings and simultaneously enzymatically remodel the extracellular matrix (ECM). The effect of forces on ECM has thus become an area of considerable interest due to its likely biological and medical importance4-7. Single molecule techniques such as optical trapping8, atomic force microscopy9, and magnetic tweezers10,11 allow researchers to probe the function of enzymes at a molecular level by exerting forces on individual proteins. Of these techniques, magnetic tweezers (MT) are notable for their low cost and high throughput. MT exert forces in the range of ~1-100 pN and can provide millisecond temporal resolution, qualities that are well matched to the study of enzyme mechanism at the single-molecule level12. Here we report a highly parallelizable MT assay to study the effect of force on the proteolysis of single protein molecules. We present the specific example of the proteolysis of a trimeric collagen peptide by matrix metalloproteinase 1 (MMP-1); however, this assay can be easily adapted to study other substrates and proteases. PMID:22871786

Adhikari, Arjun S.; Chai, Jack; Dunn, Alexander R.

2012-01-01

107

Local nonlinear rf forces in inhomogeneous magnetized plasmas  

SciTech Connect

The local nonlinear forces induced by radio frequency (rf) waves are derived in inhomogeneous magnetized plasmas, where the inhomogeneity exists in the rf fields, in the static magnetic field as well as in the equilibrium density and temperature. The local parallel force is completely resonant, but a novel component dependent on those inhomogeneities is obtained as the result of the inhomogeneous transport of parallel resonant-absorbed momentum by the nonlinear perpendicular drift flux. In the local poloidal force, the component induced by the inhomogeneity of rf power absorption is also confirmed and it can be recognized as the residual effect from the incomplete cancellation between the rate of the diamagnetic poloidal momentum gain and the Lorentz force due to the radial diffusion-like flux. The compact expression for radial force is also obtained for the first time, whose nonresonant component is expressed as the sum of the ponderomotive force on particles and the gradients of the nonresonant perpendicular pressure and of the nonresonant momentum flux due to the finite temperature effect. Numerical calculations in a 1-D slab model show that the resonant component dependent on the inhomogeneities may be significant when the ion absorption dominates the resonant wave-particle interaction. A quantitative estimation shows that the novel component in the parallel force is important to understand the experiments of the ion-cyclotron-frequency mode-conversion flow drive.

Chen, Jiale, E-mail: chen@ipp.ac.cn [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Gao, Zhe [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)

2014-06-15

108

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

109

DRAG FORCE RELATED TO BODY DIMENSIONS IN FRONT CRAWL SWIMMING  

Microsoft Academic Search

So far, a great deal of attention has been given to find out relationship between body dimensions (anthropometrical variables) and hydrodynamic resistance for actively swimming subjects. The development of a new indirect method for determining active drag (IMAD) warranted a reevaluation of this relationship, which was the aim of present study. Twenty one novice male swimmers with different body shape

Morteza Shahbazi; Mohammad R. Bahadoran; Shahla Hojjat

110

LA-UR-97-40 Magnetic Resonance Force Microscopy With a  

E-print Network

LA-UR-97-40 Magnetic Resonance Force Microscopy With a Ferromagnetic Tip Mounted on the Force Resonance Force Microscope (MRFM) presents the oppor- tunity for a magnetic resonance imaging probe MRFM techniques. A crucial remaining challenge in the development of the magnetic resonance force

Hammel, P. Chris

111

Quantification of magnetic force microscopy images using combined electrostatic and magnetostatic imaging  

E-print Network

Quantification of magnetic force microscopy images using combined electrostatic and magnetostatic-contrast magnetic force microscopy MFM is introduced. It is based upon the combined electrostatic force microscopy American Institute of Physics. S0021-8979 98 27711-5 I. INTRODUCTION Magnetic force microscopy MFM has

Gomez, Romel D.

112

Magnetic Resonance Force Microscopy Measurement of Entangled Spin States  

E-print Network

We simulate magnetic resonance force microscopy measurements of an entangled spin state. One of the entangled spins drives the resonant cantilever vibrations, while the other remote spin does not interact directly with the quasiclassical cantilever. The Schr\\"odinger cat state of the cantilever reveals two possible outcomes of the measurement for both entangled spins.

G. P. Berman; F. Borgonovi; G. Chapline; P. C. Hammel; V. I. Tsifrinovich

2001-10-10

113

Corroboration of magnetic forces in US Maglev design  

SciTech Connect

Four System Concept Definition (SCD) contractors to the National Maglev Initiative (NMI) developed conceptual designs of maglev systems in 1991--1992. The objective of the work reported here was to perform independent calculations of the magnetic forces and fields of these four systems to assess the ``reasonableness`` of the results presented to the government. Commercial computer software was used for computing forces in the system employing nonlinear ferromagnetic materials and for some calculations of induced eddy current effects in finite-sized systems. Other cases required the use of models developed at ANL and verified by experiment, or in a few cases, new computer programs that have not been validated by experiment. The magnetic forces calculated by the contractors were found to be credible in every case evaluated. The stray fields were also found to be in reasonable agreement with those calculated by the contractors, but, for lack of spice, are not reported here.

Coffey, H.; He, J.; Wang, Z.

1993-06-01

114

Corroboration of magnetic forces in US Maglev design  

SciTech Connect

Four System Concept Definition (SCD) contractors to the National Maglev Initiative (NMI) developed conceptual designs of maglev systems in 1991--1992. The objective of the work reported here was to perform independent calculations of the magnetic forces and fields of these four systems to assess the reasonableness'' of the results presented to the government. Commercial computer software was used for computing forces in the system employing nonlinear ferromagnetic materials and for some calculations of induced eddy current effects in finite-sized systems. Other cases required the use of models developed at ANL and verified by experiment, or in a few cases, new computer programs that have not been validated by experiment. The magnetic forces calculated by the contractors were found to be credible in every case evaluated. The stray fields were also found to be in reasonable agreement with those calculated by the contractors, but, for lack of spice, are not reported here.

Coffey, H.; He, J.; Wang, Z.

1993-01-01

115

Ferromagnetic resonance imaging of Co films using magnetic resonance force microscopy  

E-print Network

Ferromagnetic resonance imaging of Co films using magnetic resonance force microscopy B. J. Suh, P is similar to that used in magnetic force microscopy MFM ,4 where only the spin magnetization in the vicinity of microscopic ferromagnetic resonance FMR detected using the magnetic resonance force microscope MRFM

Hammel, P. Chris

116

Analytical equation of state with three-body forces: Application to noble gases  

SciTech Connect

We developed an explicit equation of state (EOS) for small non polar molecules by means of an effective two-body potential. The average effect of three-body forces was incorporated as a perturbation, which results in rescaled values for the parameters of the two-body potential. These values replace the original ones in the EOS corresponding to the two-body interaction. We applied this procedure to the heavier noble gases and used a modified Kihara function with an effective Axilrod-Teller-Muto (ATM) term to represent the two- and three-body forces. We also performed molecular dynamics simulations with two- and three-body forces. There was good agreement between predicted, simulated, and experimental thermodynamic properties of neon, argon, krypton, and xenon, up to twice the critical density and up to five times the critical temperature. In order to achieve 1% accuracy of the pressure at liquid densities, the EOS must incorporate the effect of ATM forces. The ATM factor in the rescaled two-body energy is most important at temperatures around and lower than the critical one. Nonetheless, the rescaling of two-body diameter cannot be neglected at liquid-like densities even at high temperature. This methodology can be extended straightforwardly to deal with other two- and three-body potentials. It could also be used for other nonpolar substances where a spherical two-body potential is still a reasonable coarse-grain approximation.

Ro, Fernando del, E-mail: fdr@xanum.uam.mx; Daz-Herrera, Enrique; Guzmn, Orlando; Moreno-Razo, Jos Antonio [Departamento de Fsica, Universidad Autnoma Metropolitana, Iztapalapa, Apdo 55 534, Mxico DF, 09340 (Mexico)] [Departamento de Fsica, Universidad Autnoma Metropolitana, Iztapalapa, Apdo 55 534, Mxico DF, 09340 (Mexico); Ramos, J. Eloy [Colegio de Ciencia y Tecnologa, Universidad Autnoma de la Ciudad de Mxico, Mexico DF (Mexico)] [Colegio de Ciencia y Tecnologa, Universidad Autnoma de la Ciudad de Mxico, Mexico DF (Mexico)

2013-11-14

117

Force prediction in permanent magnet flat linear motors (abstract)  

NASA Astrophysics Data System (ADS)

The advent of neodymium iron boron rare-earth permanent magnet material has afforded the opportunity to construct linear machines of high force to weight ratio. The paper describes the design and construction of an axial flux machine and rotating drum test rig. The machine occupies an arc of 45 on a drum 1.22 m in diameter. The excitation is provided by blocks of NdFeB material which are skewed in order to minimize the force variations due to slotting. The stator carries a three-phase short-chorded double-layer winding of four poles. The machine is supplied by a PWM inverter the fundamental component of which is phase locked to the rotor position so that a ``dc brushless'' drive system is produced. Electromagnetic forces including ripple forces are measured at supply frequencies up to 100 Hz. They are compared with finite-element analysis which calculates the force variation over the time period. The paper then considers some of the causes of ripple torque. In particular, the force production due solely to the permanent magnet excitation is considered. This has two important components each acting along the line of motion of the machine, one is due to slotting and the other is due to the finite length of the primary. In the practical machine the excitation poles are skewed to minimize the slotting force and the effectiveness of this is confirmed by both results from the experiments and the finite-element analysis. The end effect force is shown to have a space period of twice that of the excitation. The amplitude of this force and its period are again confirmed by practical results.

Eastham, J. F.; Akmese, R.

1991-11-01

118

Characterization of magnetic force microscopy probe tip remagnetization for measurements in external in-plane magnetic fields  

SciTech Connect

A quantitative analysis of magnetic force microscopy (MFM) images taken in external in-plane magnetic fields is difficult because of the influence of the magnetic field on the magnetization state of the magnetic probe tip. We prepared calibration samples by ion bombardment induced magnetic patterning with a topographically flat magnetic pattern magnetically stable in a certain external magnetic field range for a quantitative characterization of the MFM probe tip magnetization in point-dipole approximation.

Weis, Tanja; Engel, Dieter; Ehresmann, Arno [Institute of Physics and Centre for Interdisciplinary Nanostructure Science and Technology, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel (Germany); Krug, Ingo [DSM IRAMIS SPCSI, CEA-Saclay, 91191 Gif sur Yvette (France); Hoeink, Volker; Schmalhorst, Jan; Reiss, Guenter [Department of Physics, Thin Films and Nanostructures, Bielefeld University, P.O. Box 100131, 33501 Bielefeld (Germany)

2008-12-15

119

Magnetic Forces and DNA Mechanics in Multiplexed Magnetic Tweezers  

E-print Network

molecule is tethered between a paramagnetic bead and the surface of a flow cell. Tension and torque can in real time by tracking the xyz-position of the paramagnetic bead using video microscopy, thereby, Delft University of Technology, Delft, The Netherlands Abstract Magnetic tweezers (MT) are a powerful

Dekker, Cees

120

Ball lightning as a force-free magnetic knot  

PubMed

The stability of fireballs in a recent model of ball lightning is studied. It is shown that the balls shine while relaxing in an almost quiescent expansion, and that three effects contribute to their stability: (i) the formation in each one during a process of Taylor relaxation of a force-free magnetic field, a concept introduced in 1954 in order to explain the existence of large magnetic fields and currents in stable configurations of astrophysical plasmas; (ii) the so called Alfven conditions in magnetohydrodynamics; and (iii) the approximate conservation of the helicity integral. The force-free fields that appear are termed "knots" because their magnetic lines are closed and linked. PMID:11102074

Ranada; Soler; Trueba

2000-11-01

121

On unsteady-motion theory of magnetic force for maglev systems.  

SciTech Connect

Motion-dependent magnetic forces are the key elements in the study of magnetically levitated vehicle (maglev) system dynamics. This paper presents an experimental and analytical study that will enhance our understanding of the role of unsteady-motion-dependent magnetic forces and demonstrate an experimental technique that can be used to measure those unsteady magnetic forces directly. The experimental technique is a useful tool for measuring motion-dependent magnetic forces for the prediction and control of maglev systems.

Chen, S. S.; Zhu, S.; Cai, Y.; Energy Technology

1995-12-14

122

A Study of Laminar Compressible Viscous Pipe Flow Accelerated by an Axial Body Force, with Application to Magnetogasdynamics  

NASA Technical Reports Server (NTRS)

A study is made of the steady laminar flow of a compressible viscous fluid in a circular pipe when the fluid is accelerated by an axial body force. The application of the theory to the magnetofluidmechanics of an electrically conducting gas accelerated by electric and magnetic fields is discussed. Constant viscosity, thermal conductivity, and electrical conductivity are assumed. Fully developed flow velocity and temperature profiles are shown, and detailed results of the accelerating flow development, including velocity and pressure as functions of distance, are given for the case where the axial body force is constant and for the case where it is a linear function of velocity. From these results are determined the pipe entry length and the pressure difference required.

Martin, E. Dale

1961-01-01

123

Paramagnetic Beads and Magnetically Mediated Strain Enhance Cardiomyogenesis in Mouse Embryoid Bodies  

PubMed Central

Mechanical forces play an important role in proper embryologic development, and similarly such forces can directly impact pluripotency and differentiation of mouse embryonic stem cells (mESC) in vitro. In addition, manipulation of the embryoid body (EB) microenvironment, such as by incorporation of microspheres or microparticles, can similarly influence fate determination. In this study, we developed a mechanical stimulation regimen using permanent neodymium magnets to magnetically attract cells within an EB. Arginine-Glycine-Aspartic Acid (RGD)-conjugated paramagnetic beads were incorporated into the interior of the EBs during aggregation, allowing us to exert force on individual cells using short-term magnetization. EBs were stimulated for one hour at different magnetic field strengths, subsequently exerting a range of force intensity on the cells at different stages of early EB development. Our results demonstrated that following exposure to a 0.2 Tesla magnetic field, ESCs respond to magnetically mediated strain by activating Protein Kinase A (PKA) and increasing phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2) expression. The timing of stimulation can also be tailored to guide ESC differentiation: the combination of bone morphogenetic protein 4 (BMP4) supplementation with one hour of magnetic attraction on Day 3 enhances cardiomyogenesis by increasing contractile activity and the percentage of sarcomeric ?-actin-expressing cells compared to control samples with BMP4 alone. Interestingly, we also observed that the beads alone had some impact on differentiation by increasingly slightly, albeit not significantly, the percentage of cardiomyocytes. Together these results suggest that magnetically mediated strain can be used to enhance the percentage of mouse ESC-derived cardiomyocytes over current differentiation protocols. PMID:25501004

Geuss, Laura R.; Wu, Douglas C.; Ramamoorthy, Divya; Alford, Corinne D.; Suggs, Laura J.

2014-01-01

124

Energy buildup in sheared force-free magnetic fields  

NASA Technical Reports Server (NTRS)

Photospheric displacement of the footpoints of solar magnetic field lines results in shearing and twisting of the field, and consequently in the buildup of electric currents and magnetic free energy in the corona. The sudden release of this free energy may be the origin of eruptive events like coronal mass ejections, prominence eruptions, and flares. An important question is whether such an energy release may be accompanied by the opening of magnetic field lines that were previously closed, for such open field lines can provide a route for matter frozen into the field to escape the sun altogether. This paper presents the results of numerical calculations showing that opening of the magnetic field is permitted energetically, in that it is possible to build up more free energy in a sheared, closed, force-free magnetic field than is in a related magnetic configuration having both closed and open field lines. Whether or not the closed force-free field attains enough energy to become partially open depends on the form of the shear profile; the results presented compare the energy buildup for different shear profiles. Implications for solar activity are discussed briefly.

Wolfson, Richard; Low, Boon C.

1992-01-01

125

Influence of effective three-body force on the spectroscopy of ¹⁹O  

Microsoft Academic Search

The purpose of the present paper is to investigate the influence of effective three-body force on the spectroscopy of ¹⁹O. The model space was chosen as the configuration space which consists of the j-j coupling states of three valence neutrons in the s-d shell. The effective interaction including two- and three-body forces was then derived in the framework of the

W. Haung; H. Song; Z. Wang; T. T. S. Kuo

1983-01-01

126

Magnetic nasal foreign bodies: a result of fashion mania.  

PubMed

The fashion of body piercing among adults has encouraged children to have similar procedures or imitate them by applying small magnets to sustain the jewelery used in piercing in position [Emerg. Med. J. 19 (2002) 71]. We present cases of children who have placed magnets on their nasal alae that became misplaced on to the nasal septum causing severe pain and in some cases nasal bleeding and septal perforation. We describe management of these cases. PMID:14643479

Karkos, P D; Karagama, Y G; Manivasagam, A; El Badawey, M Reda

2003-12-01

127

DRAG FORCE ,RELATED TO BODY OIMENSIONS IN BUITERFLY SWIMMING  

Microsoft Academic Search

During four last decades, a great deal of attention has been given to the presupposed relationship between body dimensions and hydrodynamic resistance related drag for actively swimming subjects to anthropometrical variables. The development of a new indirect method of determining active drag (IMAD) warranted a reevaluation of this relationship, which was the aim of present study. Twenty female swimmers with

Morteza Shahbazi-Moghaddam; Safoora Sabbaghian

128

Muscle force redistributes segmental power for body progression during walking  

Microsoft Academic Search

The ankle plantar flexors were previously shown to support the body in single-leg stance to ensure its forward progression [J. Biomech. 34 (2001) 1387]. The uni- (SOL) and biarticular (GAS) plantar flexors accelerated the trunk and leg forward, respectively, with each opposing the effect of the other. Around mid-stance their net effect on the trunk and the leg was negligible,

R. R. Neptune; F. E. Zajac; S. A. Kautz

2004-01-01

129

Magnetic force micropiston: an integrated force/microfluidic device for the application of compressive forces in a confined environment.  

PubMed

Cellular biology takes place inside confining spaces. For example, bacteria grow in crevices, red blood cells squeeze through capillaries, and chromosomes replicate inside the nucleus. Frequently, the extent of this confinement varies. Bacteria grow longer and divide, red blood cells move through smaller and smaller passages as they travel to capillary beds, and replication doubles the amount of DNA inside the nucleus. This increase in confinement, either due to a decrease in the available space or an increase in the amount of material contained in a constant volume, has the potential to squeeze and stress objects in ways that may lead to changes in morphology, dynamics, and ultimately biological function. Here, we describe a device developed to probe the interplay between confinement and the mechanical properties of cells and cellular structures, and forces that arise due to changes in a structure's state. In this system, the manipulation of a magnetic bead exerts a compressive force upon a target contained in the confining space of a microfluidic channel. This magnetic force microfluidic piston is constructed in such a way that we can measure (a) target compliance and changes in compliance as induced by changes in buffer, extract, or biochemical composition, (b) target expansion force generated by changes in the same parameters, and (c) the effects of compression stress on a target's structure and function. Beyond these issues, our system has general applicability to a variety of questions requiring the combination of mechanical forces, confinement, and optical imaging. PMID:24593368

Fisher, J K; Kleckner, N

2014-02-01

130

Magnetic force micropiston: An integrated force/microfluidic device for the application of compressive forces in a confined environment  

NASA Astrophysics Data System (ADS)

Cellular biology takes place inside confining spaces. For example, bacteria grow in crevices, red blood cells squeeze through capillaries, and chromosomes replicate inside the nucleus. Frequently, the extent of this confinement varies. Bacteria grow longer and divide, red blood cells move through smaller and smaller passages as they travel to capillary beds, and replication doubles the amount of DNA inside the nucleus. This increase in confinement, either due to a decrease in the available space or an increase in the amount of material contained in a constant volume, has the potential to squeeze and stress objects in ways that may lead to changes in morphology, dynamics, and ultimately biological function. Here, we describe a device developed to probe the interplay between confinement and the mechanical properties of cells and cellular structures, and forces that arise due to changes in a structure's state. In this system, the manipulation of a magnetic bead exerts a compressive force upon a target contained in the confining space of a microfluidic channel. This magnetic force microfluidic piston is constructed in such a way that we can measure (a) target compliance and changes in compliance as induced by changes in buffer, extract, or biochemical composition, (b) target expansion force generated by changes in the same parameters, and (c) the effects of compression stress on a target's structure and function. Beyond these issues, our system has general applicability to a variety of questions requiring the combination of mechanical forces, confinement, and optical imaging.

Fisher, J. K.; Kleckner, N.

2014-02-01

131

Body force term comparison in lattice Boltzmann method for shallow water equations  

NASA Astrophysics Data System (ADS)

We present the Lattice Boltzmann method for modelling shallow water equations with a focus on external forces. Three different approximations for modelling the body force terms are used and compared in a 1D steady flow simulation over a bump. The accuracy, the mass conservation and the CPU time are discussed in this study.

Raizer, O.; Smaoui, H.; Ouahsine, A.; Sergent, P.

2013-10-01

132

REVIEW OF TERMS FOR REGULATED VERSUS FORCED, NEUROCHEMICAL-INDUCED CHANGES IN BODY TEMPERATURE  

EPA Science Inventory

Deviations of the body temperature of homeothermic animals may be regulated or forced. A regulated change in core temperature is caused by a natural or synthetic compound that displaces the set-point temperature. A forced shift occurs when an excessive environmental or endogenous...

133

Three-body radiative heat transfer and Casimir-Lifshitz force out of thermal equilibrium for arbitrary bodies  

NASA Astrophysics Data System (ADS)

We study the Casimir-Lifshitz force and the radiative heat transfer in a system consisting of three bodies held at three independent temperatures and immersed in a thermal environment, the whole system being in a stationary configuration out of thermal equilibrium. The theory we develop is valid for arbitrary bodies, i.e., for any set of temperatures, dielectric, and geometrical properties, and describes each body by means of its scattering operators. For the three-body system we provide a closed-form unified expression of the radiative heat transfer and of the Casimir-Lifshitz force (both in and out of thermal equilibrium). This expression is thus first applied to the case of three planar parallel slabs. In this context we discuss the nonadditivity of the force at thermal equilibrium, as well as the equilibrium temperature of the intermediate slab as a function of its position between two external slabs having different temperatures. Finally, we consider the force acting on an atom inside a planar cavity. We show that, differently from the equilibrium configuration, the absence of thermal equilibrium admits one or more positions of minima for the atomic potential. While the corresponding atomic potential depths are very small for typical ground-state atoms, they may become particularly relevant for Rydberg atoms, becoming a promising tool to produce an atomic trap.

Messina, Riccardo; Antezza, Mauro

2014-05-01

134

On transition from Alfvn resonance to forced magnetic reconnection  

SciTech Connect

We revisit the transition from Alfvn resonance to forced magnetic reconnection with a focus on the property of their singularities. As the driven frequency tends to zero, the logarithmic singularity of Alfvn resonance shifts to the power-law singularity of forced reconnection, due to merging of the two resonance layers. The transition criterion depends on either kinetic effects or dissipations that resolve the singularity. As an example, a small but finite resistivity ? is introduced to investigate the transition process. The transition threshold is then obtained as the driven frequency reaches a level of ?O((?/k){sup 1/3})

Luan, Q. [MOE Key Lab of Materials Modification by Beams and School of Physics and Optoelectrical Technology, Dalian University of Technology, Dalian 116024 (China); Wang, X., E-mail: xgwang@hit.edu.cn [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China)

2014-07-15

135

Effect of magnet/slot combination on triple-frequency magnetic force and vibration of permanent magnet motors  

NASA Astrophysics Data System (ADS)

The relationship between magnet/slot combination and magnetic forces including unbalanced magnetic force (UMF) and cogging torque (CT) of permanent magnet (PM) motors is investigated by using superposition principle and mechanical and magnetic symmetries. The results show that magnetic force can be produced by all magnets passing a single slot, by all slots passing a single magnet, or by eccentricity, which respectively correspond to three frequency components. The results further show that net force/torque can be classified into three typical cases: UMF is suppressed and CT is excited, UMF excited and CT suppressed, and UMF and CT both suppressed, and consequently possible vibrations include three unique groups: rotational modes, translational modes, and balanced modes. The conclusion that combinations with the greatest common divisor (GCD) greater than unity can avoid UMF is mathematically verified, and at the same time lower CT harmonics are preliminarily addressed by the typical excitations. The above findings can create simple guidelines for the suppression of certain UMF and/or CT by using suitable combinations, which in turn can present approach to yield a more desirable response in high performance applications. The superposition effect and predicted relationship are verified by the transient magnetic Finite Element method. Since this work is motivated by symmetries, comparisons are made in order to give further insight into the inner force and vibration behaviors of general rotary power-transmission systems.

Huo, Mina; Wang, Shiyu; Xiu, Jie; Cao, Shuqian

2013-10-01

136

Model calculation of effective three-body forces  

Microsoft Academic Search

We propose a scheme for extracting an effective three-body interaction originating from a two-nucleon interaction. This is based on the Q?-box method of Kuo and collaborators, where folded diagrams are obtained by differentiating a sum of nonfolded diagrams with respect to the starting energy. To gain insight we have studied several examples using the Lipkin model where the perturbative approach

Paul J Ellis; T. Engeland; M. Hjorth-Jensen; M. P. Kartamyshev; E. Osnes

2005-01-01

137

Distinguishing ferritin from apoferritin using magnetic force microscopy.  

PubMed

Estimating the amount of iron-replete ferritin versus iron-deficient apoferritin proteins is important in biomedical and nanotechnology applications. This work introduces a simple and novel approach to quantify ferritin by using magnetic force microscopy (MFM). We demonstrate how high magnetic moment probes enhance the magnitude of MFM signal, thus enabling accurate quantitative estimation of ferritin content in ferritin/apoferritin mixtures in vitro. We envisage MFM could be adapted to accurately determine ferritin content in protein mixtures or in small aliquots of clinical samples. PMID:25355655

Nocera, Tanya M; Zeng, Yuzhi; Agarwal, Gunjan

2014-11-21

138

The Aerodynamic Forces on Slender Plane- and Cruciform-Wing and Body Combinations  

NASA Technical Reports Server (NTRS)

The load distribution, forces, and moments are calculated theoretically for inclined slender wing-body combinations consisting of a slender body of revolution and either a plane or cruciform arrangement of low-aspect-ratio pointed wings. The results are applicable at subsonic and transonic speeds, and at supersonic speeds, provided the entire wing-body combination lies near the center of the Mach cone.

Spreiter, John R

1950-01-01

139

Effect of horizontal magnetization reversal of the tips on magnetic force microscopy images.  

PubMed

The effect of magnetization reversal of magnetic force microscope (MFM) tips based on low coercive thin-films on MFM images has been studied both experimentally and theoretically. By analyzing the MFM images obtained on structures with high magnetic stray fields we show that during the imaging process the magnetic state of the probe is modified anisotropically: the horizontal component of the magnetization follows the external field, whereas the vertical component of the magnetization stays almost constant. The observed complex magnetic behavior of the tip is explained theoretically based on the shape anisotropy of the tip. The obtained results are important for interpretation of MFM images of structures with high magnetic moment. Moreover, these results can be used for characterization of both laboratory-made and commercially available MFM tips. PMID:24051098

Alekseev, Alexander; Popkov, Anatoliy; Shubin, Andrey; Pudonin, Feodor; Djuzhev, Nikolay

2014-01-01

140

On the unsteady-motion theory of magnetic forces for maglev  

SciTech Connect

Motion-dependent magnetic forces are the key elements in the study of magnetically levitated vehicle (maglev) system dynamics. In the past, most maglev-system designs were based on a quasisteady-motion theory of magnetic forces. This report presents an experimental and analytical study that will enhance our understanding of the role of unsteady-motion-dependent magnetic forces and demonstrate an experimental technique that can be used to measure those unsteady magnetic forces directly. The experimental technique provides a useful tool to measure motion-dependent magnetic forces for the prediction and control of maglev systems.

Chen, S.S.; Zhu, S.; Cai, Y.

1993-11-01

141

Effect of three-body forces on response functions in infinite neutron matter  

NASA Astrophysics Data System (ADS)

We study the impact of three-body forces on the response functions of cold neutron matter. These response functions are determined in the random phase approximation from a residual interaction expressed in terms of Landau parameters. Special attention is paid to the noncentral part, including all terms allowed by the relevant symmetries. Using Landau parameters derived from realistic nuclear two- and three-body forces grounded in chiral effective field theory, we find that the three-body term has a strong impact on the excited states of the system and in the static and long-wavelength limit of the response functions for which a new exact formula is established.

Davesne, D.; Holt, J. W.; Pastore, A.; Navarro, J.

2015-01-01

142

Dynamic nanomagnetism characterization of individual magnetic nanoparticles by frequency-modulated magnetic force microscopy  

NASA Astrophysics Data System (ADS)

In this study, stroboscopic imaging of an alternating magnetic field (AC magnetic field) from individual superparamagnetic Fe3O4 nanoparticles was achieved using the developed frequency modulated-magnetic force microscopy (FM-MFM) technique, which enables the imaging of the vector signals of AC magnetic fields, such as a combination of in-phase and quadrature signals or that of amplitude and phase signals. FM-MFM uses the frequency modulation of cantilever oscillation, caused by the application of an off-resonant AC magnetic field to a mechanically oscillated cantilever, and visualises the vector signals of the AC magnetic field by adding a frequency demodulator and a lock-in amplifier to a conventional magnetic force microscope. Stroboscopic imaging of an AC magnetic field was carried out by varying the phase of the measured in-phase and quadrature signals via a signal processing technique. For the superparamagnetic Fe3O4 nanoparticles, stroboscopic imaging of the time-variable AC magnetic field, caused by the rotation of the magnetic moments within the particles, was demonstrated. This article describes the present status of FM-MFM technology, with particular attention to the feasibility of detecting magnetic moments of individual nanoparticles, and the possible application of FM-MFM in biological imaging.

Li, Xiang; Li, Zhenghua; Pan, Deng; Yoshimura, Satoru; Saito, Hitoshi

2014-05-01

143

Test of response linearity for magnetic force microscopy data R. Yongsunthon and E. D. Williamsa)  

E-print Network

Test of response linearity for magnetic force microscopy data R. Yongsunthon and E. D. Williamsa has been explored for magnetic force microscopy MFM data from current-carrying wires, by comparing-induced failure.1­3 Various groups have previously used magnetic force microscopy MFM to image current

Williams, Ellen D.

144

A GLRT AND BOOTSTRAP APPROACH TO DETECTION IN MAGNETIC RESONANCE FORCE MICROSCOPY  

E-print Network

A GLRT AND BOOTSTRAP APPROACH TO DETECTION IN MAGNETIC RESONANCE FORCE MICROSCOPY Pei­Jung Chung, USA moura@ece.cmu.edu ABSTRACT Magnetic resonance force microscopy (MRFM) is a tech- nology = 0.05, at SNR= -20 dB. 1. MOTIVATION Magnetic resonance force microscopy (MRFM), [3], and single spin

Moura, José

145

Single-spin measurement and decoherence in magnetic-resonance force microscopy G. P. Berman,1  

E-print Network

Single-spin measurement and decoherence in magnetic-resonance force microscopy G. P. Berman,1 F inversion CAI technique in magnetic-resonance force microscopy MRFM . We study the problem: What component.67.Lx I. INTRODUCTION Magnetic-resonance force microscopy MRFM is striv- ing for its ultimate goal

Goan, Hsi-Sheng

146

Theory of spin relaxation in magnetic resonance force microscopy D. Mozyrsky and I. Martina)  

E-print Network

Theory of spin relaxation in magnetic resonance force microscopy D. Mozyrsky and I. Martina; accepted 31 December 2002 We study relaxation of a spin in magnetic resonance force microscopy MRFM fluctuations. © 2003 American Institute of Physics. DOI: 10.1063/1.1554769 Magnetic resonance force microscopy

Hammel, P. Chris

147

Application of Magnetic Resonance Force Microscopy Cyclic Adiabatic Inversion for a Single-Spin Measurement  

E-print Network

Application of Magnetic Resonance Force Microscopy Cyclic Adiabatic Inversion for a Single using magnetic resonance force microscopy (MRFM) with a cyclic adiabatic inversion (CAI). This technique, 14].) One of them is based on a magnetic resonance force microscopy (MRFM). A MRFM was first proposed

Hammel, P. Chris

148

Static Stern-Gerlach effect in magnetic force microscopy G. P. Berman,1  

E-print Network

Static Stern-Gerlach effect in magnetic force microscopy G. P. Berman,1 G. D. Doolen,1 P. C. Hammel February 2002 We examine static single-spin measurements using magnetic-force microscopy methods. We show the magnetic- resonance force microscopy MRFM was proposed as a new method for performing a SG measurement

Hammel, P. Chris

149

Magnetic tweezers: micromanipulation and force measurement at the molecular level.  

PubMed

Cantilevers and optical tweezers are widely used for micromanipulating cells or biomolecules for measuring their mechanical properties. However, they do not allow easy rotary motion and can sometimes damage the handled material. We present here a system of magnetic tweezers that overcomes those drawbacks while retaining most of the previous dynamometers properties. Electromagnets are coupled to a microscope-based particle tracking system through a digital feedback loop. Magnetic beads are first trapped in a potential well of stiffness approximately 10(-7) N/m. Thus, they can be manipulated in three dimensions at a speed of approximately 10 microm/s and rotated along the optical axis at a frequency of 10 Hz. In addition, our apparatus can work as a dynamometer relying on either usual calibration against the viscous drag or complete calibration using Brownian fluctuations. By stretching a DNA molecule between a magnetic particle and a glass surface, we applied and measured vertical forces ranging from 50 fN to 20 pN. Similarly, nearly horizontal forces up to 5 pN were obtained. From those experiments, we conclude that magnetic tweezers represent a low-cost and biocompatible setup that could become a suitable alternative to the other available micromanipulators. PMID:12023254

Gosse, Charlie; Croquette, Vincent

2002-06-01

150

NMR Spectroscopy for Thin Films by Magnetic Resonance Force Microscopy  

PubMed Central

Nuclear magnetic resonance (NMR) is a fundamental research tool that is widely used in many fields. Despite its powerful applications, unfortunately the low sensitivity of conventional NMR makes it difficult to study thin film or nano-sized samples. In this work, we report the first NMR spectrum obtained from general thin films by using magnetic resonance force microscopy (MRFM). To minimize the amount of imaging information inevitably mixed into the signal when a gradient field is used, we adopted a large magnet with a flat end with a diameter of 336??m that generates a homogeneous field on the sample plane and a field gradient in a direction perpendicular to the plane. Cyclic adiabatic inversion was used in conjunction with periodic phase inversion of the frequency shift to maximize the SNR. In this way, we obtained the 19F NMR spectrum for a 34?nm-thick CaF2 thin film. PMID:24217000

Won, Soonho; Saun, Seung-Bo; Lee, Soonchil; Lee, SangGap; Kim, Kiwoong; Han, Yunseok

2013-01-01

151

Dielectrophoresis-magnetophoresis force driven magnetic nanoparticle movement in transformer oil based magnetic fluids.  

PubMed

Magnetic fluid is a stable colloidal mixture contained magnetic nanoparticles coated with a surfactant. Recently, it was found that the fluid has properties to increase heat transfer and dielectric characteristics due to the added magnetic nanoparticles in transformer oils. The magnetic nanoparticles in the fluid experience an electrical force directed toward the place of maximum electric field strength when the electric field is applied. And when the external magnetic field is applied, the magnetic nanoparticles form long chains oriented along the direction of the field. The behaviors of magnetic nanoparticles in both the fields must play an important role in changing the heat transfer and dielectric characteristics of the fluids. In this study, we visualized the movement of magnetic nanoparticles influenced by both the fields applied in-situ. It was found that the magnetic nanoparticles travel in the region near the electrode by the electric field and form long chains along the field direction by the magnetic field. It can be inferred that the movement of magnetic nanoparticles appears by both the fields, and the breakdown voltage of transformer oil based magnetic fluids might be influenced according to the dispersion of magnetic nanoparticles. PMID:24205624

Lee, Jong-Chul; Lee, Sangyoup

2013-09-01

152

The inverse problem in magnetic force microscopyinferring sample magnetization from MFM images  

NASA Astrophysics Data System (ADS)

Nanomagnetic structures have the potential to surpass silicons scaling limitations both as elements in hybrid CMOS logic and as novel computational elements. Magnetic force microscopy (MFM) offers a convenient characterization technique for use in the design of such nanomagnetic structures. MFM measures the magnetic field and not the samples magnetization. As such the question of the uniqueness of the relationship between an external magnetic field and a magnetization distribution is a relevant one. To study this problem we present a simple algorithm which searches for magnetization distributions consistent with an external magnetic field and solutions to the micromagnetic equations qualitative features. The algorithm is not computationally intensive and is found to be effective for our test cases. On the basis of our results we propose a systematic approach for interpreting MFM measurements.

Rawlings, Colin; Durkan, Colm

2013-08-01

153

Compensation of magnetic disturbances improves inertial and magnetic sensing of human body segment orientation  

Microsoft Academic Search

This paper describes a complementary Kalman filter design to estimate orientation of human body segments by fusing gyroscope, accelerometer, and magnetometer signals from miniature sensors. Ferromagnetic materials or other magnetic fields near the sensor module disturb the local earth magnetic field and, therefore, the orientation estimation, which impedes many (ambulatory) applications. In the filter, the gyroscope bias error, orientation error,

Daniel Roetenberg; Henk J. Luinge; Chris T. M. Baten; Peter H. Veltink

2005-01-01

154

Nuclear three-body force effect on a kaon condensate in neutron star matter  

SciTech Connect

We explore the effects of a microscopic nuclear three-body force on the threshold baryon density for kaon condensation in chemical equilibrium neutron star matter and on the composition of the kaon condensed phase in the framework of the Brueckner-Hartree-Fock approach. Our results show that the nuclear three-body force affects strongly the high-density behavior of nuclear symmetry energy and consequently reduces considerably the critical density for kaon condensation provided that the proton strangeness content is not very large. The dependence of the threshold density on the symmetry energy becomes weaker as the proton strangeness content increases. The kaon condensed phase of neutron star matter turns out to be proton rich instead of neutron rich. The three-body force has an important influence on the composition of the kaon condensed phase. Inclusion of the three-body force contribution in the nuclear symmetry energy results in a significant reduction of the proton and kaon fractions in the kaon condensed phase which is more proton-rich in the case of no three-body force. Our results are compared to other theoretical predictions by adopting different models for the nuclear symmetry energy. The possible implications of our results for the neutron star structure are also briefly discussed.

Zuo, W. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); School of Physics and Technology, Lanzhou University, Lanzhou 730000 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Institut fuer Theoretische Physik der Justus-Liebig-Universitaet, D-35392, Giessen (Germany); Li, A. [School of Physics and Technology, Lanzhou University, Lanzhou 730000 (China); Li, Z.H. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Lombardo, U. [INFN-LNS, Via Santa Sofia 44, I-95123 Catania (Italy)

2004-11-01

155

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

E-print Network

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

Prozorov, Ruslan

156

Magnetic evidence for a partially differentiated carbonaceous chondrite parent body  

PubMed Central

The textures of chondritic meteorites demonstrate that they are not the products of planetary melting processes. This has long been interpreted as evidence that chondrite parent bodies never experienced large-scale melting. As a result, the paleomagnetism of the CV carbonaceous chondrite Allende, most of which was acquired after accretion of the parent body, has been a long-standing mystery. The possibility of a core dynamo like that known for achondrite parent bodies has been discounted because chondrite parent bodies are assumed to be undifferentiated. Resolution of this conundrum requires a determination of the age and timescale over which Allende acquired its magnetization. Here, we report that Allendes magnetization was acquired over several million years (Ma) during metasomatism on the parent planetesimal in a >?20?T field up to approximately 910Ma after solar system formation. This field was present too recently and directionally stable for too long to have been generated by the protoplanetary disk or young Sun. The field intensity is in the range expected for planetesimal core dynamos, suggesting that CV chondrites are derived from the outer, unmelted layer of a partially differentiated body with a convecting metallic core.

Carporzen, Laurent; Weiss, Benjamin P.; Elkins-Tanton, Linda T.; Shuster, David L.; Ebel, Denton; Gattacceca, Jrme

2011-01-01

157

Magnetic force microscopy reveals meta-stable magnetic domain states that prevent reliable absolute palaeointensity experiments  

NASA Astrophysics Data System (ADS)

Obtaining reliable estimates of the absolute palaeointensity of the Earths magnetic field is notoriously difficult. The heating of samples in most methods induces magnetic alterationa process that is still poorly understood, but prevents obtaining correct field values. Here we show induced changes in magnetic domain state directly by imaging the domain configurations of titanomagnetite particles in samples that systematically fail to produce truthful estimates. Magnetic force microscope images were taken before and after a heating step typically used in absolute palaeointensity experiments. For a critical temperature (250?C), we observe major changes: distinct, blocky domains before heating change into curvier, wavy domains thereafter. These structures appeared unstable over time: after 1-year of storage in a magnetic-field-free environment, the domain states evolved into a viscous remanent magnetization state. Our observations qualitatively explain reported underestimates from otherwise (technically) successful experiments and therefore have major implications for all palaeointensity methods involving heating.

de Groot, Lennart V.; Fabian, Karl; Bakelaar, Iman A.; Dekkers, Mark J.

2014-08-01

158

Magnetic vortex observation in FeCo nanowires by quantitative magnetic force microscopy  

NASA Astrophysics Data System (ADS)

An approach is presented that allows quantifying the three dimensional magnetization pattern of a magnetic nanoobject from measured two dimensional Magnetic Force Microscopy (MFM) data. This is based on a MFM deconvolution approach, which quantitatively determines the effective surface charges, on a micromagnetic calculation of the total magnetic charges at and below the sample surface, and on a projection of the lower lying charges onto the sample surface for a comparison of the such obtained effective surface charges with the experimentally determined ones. Thus, by making use of the depth sensitivity of MFM and by applying a quantitative contrast analysis, we are able to reconstruct the inhomogeneous magnetization state at the end of individual cylindrical Fe52Co48 nanowires arranged in a triangular array. As a result, we prove the existence of a magnetic vortex state at their ends.

Vock, S.; Hengst, C.; Wolf, M.; Tschulik, K.; Uhlemann, M.; Sasvri, Z.; Makarov, D.; Schmidt, O. G.; Schultz, L.; Neu, V.

2014-10-01

159

Magnetic force microscopy reveals meta-stable magnetic domain states that prevent reliable absolute palaeointensity experiments.  

PubMed

Obtaining reliable estimates of the absolute palaeointensity of the Earth's magnetic field is notoriously difficult. The heating of samples in most methods induces magnetic alteration--a process that is still poorly understood, but prevents obtaining correct field values. Here we show induced changes in magnetic domain state directly by imaging the domain configurations of titanomagnetite particles in samples that systematically fail to produce truthful estimates. Magnetic force microscope images were taken before and after a heating step typically used in absolute palaeointensity experiments. For a critical temperature (250?C), we observe major changes: distinct, blocky domains before heating change into curvier, wavy domains thereafter. These structures appeared unstable over time: after 1-year of storage in a magnetic-field-free environment, the domain states evolved into a viscous remanent magnetization state. Our observations qualitatively explain reported underestimates from otherwise (technically) successful experiments and therefore have major implications for all palaeointensity methods involving heating. PMID:25145681

de Groot, Lennart V; Fabian, Karl; Bakelaar, Iman A; Dekkers, Mark J

2014-01-01

160

Impact force measurement of a spherical body dropping onto a water surface.  

PubMed

We propose a method for measuring the impact force of a spherical body dropping onto a water surface. The velocity of the center of gravity of a metal spherical body, in which a cube corner prism is embedded so that its optical center coincides with the center of gravity of the sphere, is accurately measured using an optical interferometer. The acceleration, displacement, and inertial force of the sphere are calculated from the velocity. The sphere is also observed using a high-speed camera. The uncertainty in measuring the instantaneous value of the impact force with a sampling interval of approximately 1 ms is estimated to be 8 mN, which corresponds to 0.8% of the maximum force of approximately 1.0 N. PMID:25085174

Araki, R; Takita, A; Ishima, T; Kawashima, H; Pornsuwancharoen, N; Punthawanunt, S; Carcasona, E; Fujii, Y

2014-07-01

161

Impact force measurement of a spherical body dropping onto a water surface  

NASA Astrophysics Data System (ADS)

We propose a method for measuring the impact force of a spherical body dropping onto a water surface. The velocity of the center of gravity of a metal spherical body, in which a cube corner prism is embedded so that its optical center coincides with the center of gravity of the sphere, is accurately measured using an optical interferometer. The acceleration, displacement, and inertial force of the sphere are calculated from the velocity. The sphere is also observed using a high-speed camera. The uncertainty in measuring the instantaneous value of the impact force with a sampling interval of approximately 1 ms is estimated to be 8 mN, which corresponds to 0.8% of the maximum force of approximately 1.0 N.

Araki, R.; Takita, A.; Ishima, T.; Kawashima, H.; Pornsuwancharoen, N.; Punthawanunt, S.; Carcasona, E.; Fujii, Y.

2014-07-01

162

Magnetic anisotropy considerations in magnetic force microscopy studies of single superparamagnetic nanoparticles.  

PubMed

In recent years, superparamagnetic nanoparticles (SPNs) have become increasingly important in applications ranging from solid state memory devices to biomedical diagnostic and therapeutic tools. However, detection and characterization of the small and unstable magnetic moment of an SPN at the single particle level remains a challenge. Further, depending on their physical shape, crystalline structure or orientation, SPNs may also possess magnetic anisotropy, which can govern the extent to which their magnetic moments can align with an externally applied magnetic field. Here, we demonstrate how we can exploit the magnetic anisotropy of SPNs to enable uniform, highly-sensitive detection of single SPNs using magnetic force microscopy (MFM) in ambient air. Superconducting quantum interference device magnetometry and analytical transmission electron microscopy techniques are utilized to characterize the collective magnetic behavior, morphology and composition of the SPNs. Our results show how the consideration of magnetic anisotropy can enhance the ability of MFM to detect single SPNs at ambient room temperature with high force sensitivity and spatial resolution. PMID:23149438

Nocera, Tanya M; Chen, Jun; Murray, Christopher B; Agarwal, Gunjan

2012-12-14

163

Influence of the Reynolds number on normal forces of slender bodies of revolution  

NASA Technical Reports Server (NTRS)

Comprehensive force, moment, and pressure distribution measurements as well as flow visualization experiments were carried out to determine the influence of the Reynolds number on nonlinear normal forces of slender bodies of revolution. Experiments were performed in transonic wind tunnels at angles of attack up to 90 deg in the Mach number range 0.5 to 2.2 at variable Reynolds numbers. The results were analysed theoretically and an empirical theory was developed which describes the test results satisfactory.

Hartmann, K.

1982-01-01

164

Three-body force in bound trinucleon system with explicit ▵ (1236) components  

Microsoft Academic Search

It is shown that the sum of all time-ordered diagrams which contribute to the two-meson-exchange three-body potential due to the excitation of one nucleon into a ▵ isobar can be reproduced by the second order iteration of the nonrelativistic one-meson-exchange transition potential in the coupled channels approach. [NUCLEAR STRUCTURE Two-meson-exchange three-body force, effects of Delta(1236), validity of coupled channels approach.

Shin Nan Yang

1981-01-01

165

Atomic micromotion and geometric forces in a triaxial magnetic trap  

E-print Network

Non-adiabatic motion of Bose-Einstein condensates of rubidium atoms arising from the dynamical nature of a time-orbiting-potential (TOP) trap was observed experimentally. The orbital micromotion of the condensate in velocity space at the frequency of the rotating bias field of the TOP was detected by a time-of-flight method. A dependence of the equilibrium position of the atoms on the sense of rotation of the bias field was observed. We have compared our experimental findings with numerical simulations. The nonadiabatic following of the atomic spin in the trap rotating magnetic field produces geometric forces acting on the trapped atoms.

Mller, J H; Ciampini, D; Anderlini, M; Mannella, R; Arimondo, E

2000-01-01

166

Atomic micromotion and geometric forces in a triaxial magnetic trap  

E-print Network

Non-adiabatic motion of Bose-Einstein condensates of rubidium atoms arising from the dynamical nature of a time-orbiting-potential (TOP) trap was observed experimentally. The orbital micromotion of the condensate in velocity space at the frequency of the rotating bias field of the TOP was detected by a time-of-flight method. A dependence of the equilibrium position of the atoms on the sense of rotation of the bias field was observed. We have compared our experimental findings with numerical simulations. The nonadiabatic following of the atomic spin in the trap rotating magnetic field produces geometric forces acting on the trapped atoms.

J. H. Mller; O. Morsch; D. Ciampini; M. Anderlini; R. Mannella; E. Arimondo

2000-05-30

167

Variable force, eddy-current or magnetic damper  

NASA Technical Reports Server (NTRS)

An object of the invention is to provide variable damping for resonant vibrations which may occur at different rotational speeds in the range of rpms in which a rotating machine is operated. A variable force damper in accordance with the invention includes a rotating mass carried on a shaft which is supported by a bearing in a resilient cage. The cage is attached to a support plate whose rim extends into an annular groove in a housing. Variable damping is effected by tabs of electrically conducting nonmagnetic material which extend radially from the cage. The tabs at an index position lie between the pole face of respective C shaped magnets. The magnets are attached by cantilever spring members to the housing.

Cunningham, R. E. (inventor)

1985-01-01

168

Drag measurements on a laminar-flow body of revolution in the 13-inch magnetic suspension and balance system  

NASA Technical Reports Server (NTRS)

Low speed wind tunnel drag force measurements were taken on a laminar flow body of revolution free of support interference. This body was tested at zero incidence in the NASA Langley 13 in. Magnetic Suspension and Balance System (MSBS). The primary objective of these tests was to substantiate the drag force measuring capabilities of the 13 in. MSBS. The drag force calibrations and wind-on repeatability data provide a means of assessing these capabilities. Additional investigations include: (1) the effects of fixing transition; (2) the effects of fins installed in the tail; and (3) surface flow visualization using both liquid crystals and oil flow. Also two simple drag prediction codes were used to assess their usefulness in estimating overall body drag.

Dress, David A.

1989-01-01

169

Local field loop measurements by magnetic force microscopy  

NASA Astrophysics Data System (ADS)

Magnetic force microscopy (MFM) is a valuable technique to investigate the reversal mechanisms of the magnetization in micrometric and sub-micrometric-patterned thin films that cannot be studied by means of magneto-optical methods because of their limited resolution. However, acquiring tens or hundreds of images consecutively at different applied magnetic fields is often impossible or impractical. Therefore, a field-dependent MFM-derived technique is discussed and applied on square and circular dots of different materials (Ni80Fe20, Co67Fe4Si14.5B14.5, Fe78Si9B13) having sizes ranging from 800 nm to 20 m. Experimental local hysteresis loops are obtained by properly analysing the phase signal of the MFM along a selected profile of the studied patterned structure, as a function of the applied magnetic field. Characteristic features of the magnetization process, such as vortex nucleation and expulsion, transition from C-state to saturated state or domain wall motion in Landau-like domain configuration are identified, and their evolution with the applied field is followed. The necessity to combine experimental and theoretical analyses is addressed by micromagnetic simulations on a model system (a Ni80Fe20 square dot with a lateral size of 800 nm), comparable to one of the studied samples. The agreement between experimental and simulated MFM maps, at different applied fields, and hysteresis loops provides the necessary validation for the technique. Additionally, the simulations have been proven to be necessary to understand the magnetization reversal processes occurring in the studied sub-micrometric structures and to associate them with characteristic features of the hysteresis loops measured with the proposed technique.

Cosson, Marco; Barrera, Gabriele; Celegato, Federica; Enrico, Emanuele; Manzin, Alessandra; Olivetti, Elena S.; Tiberto, Paola; Vinai, Franco

2014-08-01

170

Wing and body motion and aerodynamic and leg forces during take-off in droneflies.  

PubMed

Here, we present a detailed analysis of the take-off mechanics in droneflies performing voluntary take-offs. Wing and body kinematics of the insects during take-off were measured using high-speed video techniques. Based on the measured data, the inertia force acting on the insect was computed and the aerodynamic force of the wings was calculated by the method of computational fluid dynamics. Subtracting the aerodynamic force and the weight from the inertia force gave the leg force. In take-off, a dronefly increases its stroke amplitude gradually in the first 10-14 wingbeats and becomes airborne at about the 12th wingbeat. The aerodynamic force increases monotonously from zero to a value a little larger than its weight, and the leg force decreases monotonously from a value equal to its weight to zero, showing that the droneflies do not jump and only use aerodynamic force of flapping wings to lift themselves into the air. Compared with take-offs in insects in previous studies, in which a very large force (5-10 times of the weight) generated either by jumping legs (locusts, milkweed bugs and fruit flies) or by the 'fling' mechanism of the wing pair (butterflies) is used in a short time, the take-off in the droneflies is relatively slow but smoother. PMID:24132205

Chen, Mao Wei; Zhang, Yan Lai; Sun, Mao

2013-12-01

171

Realistic simulations of single-spin nondemolition measurement by magnetic resonance force microscopy  

E-print Network

-spin detection, magnetic reso- nance force microscopy MRFM has been suggested 7­9 as one of the most promisingRealistic simulations of single-spin nondemolition measurement by magnetic resonance force resonance force microscopy MRFM , including the effects of thermal noise and back action from monitoring. We

Goan, Hsi-Sheng

172

Sensitivity and spatial resolution for electron-spin-resonance detection by magnetic resonance force microscopy  

E-print Network

The signal intensity of electron spin resonance in magnetic resonance force microscopy MRFM experiments that magnetic resonance force microscopy MRFM is a new 3D imaging technique8,9 with the potential of achieving force microscopy Z. Zhanga) Condensed Matter and Thermal Physics Group, Materials Science and Technology

Hammel, P. Chris

173

Observation of ferromagnetic resonance in a microscopic sample using magnetic resonance force microscopy  

E-print Network

can be measured. Employing magnetic resonance force microscopy MRFM we have observed a strong FMRObservation of ferromagnetic resonance in a microscopic sample using magnetic resonance force resonance force microscopy MRFM . The large signal intensity in the resonance spectra suggests that MRFM

Hammel, P. Chris

174

Evyatar Hacker Title: Nonlinear Dynamics and Orbital Instabilities in Magnetic Resonance Force Microscopy  

E-print Network

Microscopy Magnetic resonance force microscopy (MRFM) is an imaging technique that enables acquisitionEvyatar Hacker Title: Nonlinear Dynamics and Orbital Instabilities in Magnetic Resonance Force) with atomic force microscopy (AFM), and is implemented mechanically using a vibrating sensor to directly

Moriah, Yoav

175

A numerical method for the evaluation of hydrodynamic forces of translating bodies under a free surface  

Microsoft Academic Search

This paper presents a numerical method to evaluate the hydrodynamic forces of translating bodies under a free surface. Both steady and unsteady problems are considered. Analytical and numerical studies are carried out based on the Havelock wave-source function and the integral equation method. Two main problems arising inherently in the proposed solution method are overcome in order to facilitate the

S. A. Yang

2000-01-01

176

The Physical Connection and Magnetic Coupling of the MICE CoolingChannel Magnets and the Magnet Forces for Various MICE OperatingModes  

SciTech Connect

A key issue in the construction of the MICE cooling channel is the magnetic forces between various elements in the cooling channel and the detector magnets. This report describes how the MICE cooling channel magnets are hooked to together so that the longitudinal magnetic forces within the cooling channel can be effectively connected to the base of the experiment. This report presents a magnetic force and stress analysis for the MICE cooling channel magnets, even when longitudinal magnetic forces as large as 700 kN (70 tons) are applied to the vacuum vessel of various magnets within the MICE channel. This report also shows that the detector magnets can be effectively separated from the central MICE cooling channel magnets without damage to either type of magnet component.

Yang, Stephanie Q.; Baynham, D.E.; Fabricatore, Pasquale; Farinon, Stefania; Green, Michael A.; Ivanyushenkov, Yury; Lau, Wing W.; Maldavi, S.M.; Virostek, Steve P.; Witte, Holger

2006-08-20

177

Many-body effects are essential in a physically motivated CO2 force field.  

PubMed

We develop a physically motivated many-body force field for CO(2), incorporating explicit three-body interactions parameterized on the basis of two- and three-body symmetry adapted perturbation theory (SAPT) calculations. The potential is parameterized consistently with, and builds upon, our successful SAPT-based two-body CO(2) model ("Schmidt, Yu, and McDaniel" (SYM) model) [K. Yu, J. G. McDaniel, and J. R. Schmidt, J. Phys Chem B 115, 10054 (2011)]. We demonstrate that three-body interactions are essential to achieve an accurate description of bulk properties, and that previous two-body models have therefore necessarily exploited large error cancellations to achieve satisfactory results. The resulting three-body model exhibits excellent second/third virial coefficients and bulk properties over the phase diagram, yielding a nearly empirical parameter-free model. We show that this explicit three-body model can be converted into a computationally efficient, density/temperature-dependent two-body model that reduces almost exactly to our prior SYM model in the high-density limit. PMID:22280763

Yu, Kuang; Schmidt, J R

2012-01-21

178

Many-body effects are essential in a physically motivated CO2 force field  

NASA Astrophysics Data System (ADS)

We develop a physically motivated many-body force field for CO2, incorporating explicit three-body interactions parameterized on the basis of two- and three-body symmetry adapted perturbation theory (SAPT) calculations. The potential is parameterized consistently with, and builds upon, our successful SAPT-based two-body CO2 model ("Schmidt, Yu, and McDaniel" (SYM) model) [K. Yu, J. G. McDaniel, and J. R. Schmidt, J. Phys Chem B 115, 10054 (2011), 10.1021/jp204563n]. We demonstrate that three-body interactions are essential to achieve an accurate description of bulk properties, and that previous two-body models have therefore necessarily exploited large error cancellations to achieve satisfactory results. The resulting three-body model exhibits excellent second/third virial coefficients and bulk properties over the phase diagram, yielding a nearly empirical parameter-free model. We show that this explicit three-body model can be converted into a computationally efficient, density/temperature-dependent two-body model that reduces almost exactly to our prior SYM model in the high-density limit.

Yu, Kuang; Schmidt, J. R.

2012-01-01

179

Wing/body kinematics measurement and force and moment analyses of the takeoff flight of fruitflies  

NASA Astrophysics Data System (ADS)

In the paper, we present a detailed analysis of the takeoff mechanics of fruitflies which perform voluntary takeoff flights. Wing and body kinematics of the insects during takeoff were measured using high-speed video techniques. Based on the measured data, inertia force acting on the insect was computed and aerodynamic force and moment of the wings were calculated by the method of computational fluid dynamics. Subtracting the aerodynamic force and the weight from the inertia force gave the leg force. The following has been shown. In its voluntary takeoff, a fruitfly jumps during the first wingbeat and becomes airborne at the end of the first wingbeat. When it is in the air, the fly has a relatively large "initial" pitch-up rotational velocity (more than 5 000/s) resulting from the jumping, but in about 5 wing-beats, the pitch-up rotation is stopped and the fly goes into a quasi-hovering flight. The fly mainly uses the force of jumping legs to lift itself into the air (the force from the flapping wings during the jumping is only about 5%-10% of the leg force). The main role played by the flapping wings in the takeoff is to produce a pitch-down moment to nullify the large "initial" pitch-up rotational velocity (otherwise, the fly would have kept pitching-up and quickly fallen down).

Chen, Mao-Wei; Sun, Mao

2014-08-01

180

Forced three-dimensional magnetic reconnection due to linkage of magnetic flux tubes  

SciTech Connect

During periods of southward interplanetary magnetic field (IMF) orientation the magnetic field geometry at the dayside magnetopause is susceptible to magnetic reconnection. It has been suggested that reconnection may occur in a localized manner at several patches on the magnetopause. A major problem with this picture is the interaction of magnetic flux ropes which are generated by different reconnection processes. An individual flux rope is bent elbowlike where it intersects the magnetopause and the magnetic field changes from magnetospheric to interplanetary magnetic field orientation. Multiple patches of reconnection can lead to the formation of interlinked magnetic flux tubes. Although the corresponding flux is connected to the IMF the northward and southward connected branches are hooked into each other and cannot develop independently. We have studied this problem in the framework of three-dimensional magnetohydrodynamic simulations. The results indicate that a singular current sheet forms at the interface of two interlinked flux tubes if no resistivity is present in the simulation. This current sheet is strongly tilted compared to the original current sheet. In the presence of resistivity the interaction of the two flux tubes forces a fast reconnection process which generates helically twisted closed magnetospheric flux. This linkage induced reconnection generates a boundary layer with layers of open and closed magnetospheric flux and may account for the brightening of auroral arcs poleward of the boundary between open and closed magnetic flux.

Otto, A. [Univ. of Alaska, Fairbanks, AK (United States)

1995-07-01

181

Forced three-dimensional magnetic reconnection due to linkage of magnetic flux tubes  

NASA Technical Reports Server (NTRS)

During periods of southward interplanetary magnetic field (IMF) orientation the magnetic field geometry at the dayside magnetopause is susceptible to magnetic reconnection. It has been suggested that reconnection may occur in a localized manner at several patches on the magnetopause. A major problem with this picture is the interaction of magnetic flux ropes which are generated by different reconnection processes. An individual flux rope is bent elbowlike where it intersects the magnetopause and the magnetic field changes from magnetospheric to interplanetary magnetic field orientation. Multiple patches of reconnection can lead to the formation of interlinked magnetic flux tubes. Although the corresponding flux is connected to the IMF the northward and southward connected branches are hooked into each other and cannot develop independently. We have studied this problem in the framework of three-dimensional magnetohydrodynamic simulations. The results indicate that a singular current sheet forms at the interface of two interlinked flux tubes if no resistivity is present in the simulation. This current sheet is strongly tilted compared to the original current sheet. In the presence of resistivity the interaction of the two flux tubes forces a fast reconnection process which generates helically twisted closed magnetospheric flux. This linkage induced reconnection generates a boundary layer with layers of open and closed magnetospheric flux and may account for the brightening of auroral arcs poleward of the boundary between open and closed magnetic flux.

Otto, A.

1995-01-01

182

Magnetic aftereffect and magnetic force microscopy studies of Fe-B/FePt-type nanocomposite ribbons  

NASA Astrophysics Data System (ADS)

Magnetic aftereffect and surface magnetic domain structure of (Fe0.675Pt0.325)100-xBx(x=12-20) nanocomposites have been investigated for correlating with their corresponding phases and magnetic properties. Exchange-coupling effect between grains is present for all the studied ribbons as evidenced by Henkel plot. The volume fraction of magnetically soft phases decreases with increasing B concentration from x=12 to x=18. It leads to the reduction in the activation volume of the reverse domain. Among all samples, the (Fe0.675Pt0.325)82B18 ribbon having the highest intrinsic coercivity (iHc) exhibits minimum value in activation volume V=1.110-18 cm3, because it possesses the least volume fraction of the magnetic soft phases, i.e., Fe2B or Fe3B phases. Magnetic force microscopy studies reveal the magnetic domain structures of the ribbons, confirming the existence of strong exchange coupling between magnetic grains.

Chang, C. W.; Chang, H. W.; Chiu, C. H.; Chang, W. C.; Fang, Y. K.; Han, B. S.

2006-04-01

183

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

184

Flow and Force Equations for a Body Revolving in a Fluid  

NASA Technical Reports Server (NTRS)

Part I gives a general method for finding the steady-flow velocity relative to a body in plane curvilinear motion, whence the pressure is found by Bernoulli's energy principle. Integration of the pressure supplies basic formulas for the zonal forces and moments on the revolving body. Part II, applying this steady-flow method, finds the velocity and pressure at all points of the flow inside and outside an ellipsoid and some of its limiting forms, and graphs those quantities for the latter forms. Part III finds the pressure, and thence the zonal force and moment, on hulls in plane curvilinear flight. Part IV derives general equations for the resultant fluid forces and moments on trisymmetrical bodies moving through a perfect fluid, and in some cases compares the moment values with those found for bodies moving in air. Part V furnishes ready formulas for potential coefficients and inertia coefficients for an ellipsoid and its limiting forms. Thence are derived tables giving numerical values of those coefficients for a comprehensive range of shapes.

Zahm, A F

1930-01-01

185

Ground reaction forces during level ground walking with body weight unloading  

PubMed Central

Background: Partial body weight support (BWS) systems have been broadly used with treadmills as a strategy for gait training of individuals with gait impairments. Considering that we usually walk on level ground and that BWS is achieved by altering the load on the plantar surface of the foot, it would be important to investigate some ground reaction force (GRF) parameters in healthy individuals walking on level ground with BWS to better implement rehabilitation protocols for individuals with gait impairments. Objective: To describe the effects of body weight unloading on GRF parameters as healthy young adults walked with BWS on level ground. Method: Eighteen healthy young adults (274 years old) walked on a walkway, with two force plates embedded in the middle of it, wearing a harness connected to a BWS system, with 0%, 15%, and 30% BWS. Vertical and horizontal peaks and vertical valley of GRF, weight acceptance and push-off rates, and impulse were calculated and compared across the three experimental conditions. Results: Overall, participants walked more slowly with the BWS system on level ground compared to their normal walking speed. As body weight unloading increased, the magnitude of the GRF forces decreased. Conversely, weight acceptance rate was similar among conditions. Conclusions: Different amounts of body weight unloading promote different outputs of GRF parameters, even with the same mean walk speed. The only parameter that was similar among the three experimental conditions was the weight acceptance rate. PMID:25590450

Barela, Ana M. F.; de Freitas, Paulo B.; Celestino, Melissa L.; Camargo, Marcela R.; Barela, Jos A.

2014-01-01

186

Development of a Force Measurement Device for Lower-Body Muscular Strength Measuring of Skaters  

NASA Astrophysics Data System (ADS)

This paper presents a force measurement system that can measure a lower-body muscular strength of skaters. The precise measurement and analysis of the left and right lower-body strength of skaters is necessary, because a left/right lower-body strength balance is helpful to improve the athletes' performance and to protect them from injury. The system is constructed with a skate sliding board, a couple of sensor-units with load cell, indicator and control box, guard, force pad, and support bracket. The developed force measurement system is calibrated by the calibration setup, and the uncertainty of the force sensing unit on the left is within 0.087% and the uncertainty of the force sensing unit on the right is within 0.109%. In order to check the feasibility of the developed measurement device, a kinematic analysis is conducted with skater. As a result, the subject shows the deviation of left and right of 12.1 N with respect to average strength and 39.1 N with respect to the maximum strength. This evaluation results are reliable enough to make it possible to measure a lower-body muscular strength of skaters. The use of this measurement system will be expected to correct the posture of skaters and record the sports dynamics data for each athlete. It is believed that through the development of this equipment, skaters in elementary, middle, high schools, colleges, and the professional level have the systematic training to compete with world-class skaters.

Kim, Dong Ki; Lee, Jeong Tae

187

Importance of the three-body effective force in the spectra of some 0p shell nuclei  

Microsoft Academic Search

In this paper we have tried to ascertain the importance of the three-body effective force in the normal parity spectra of nuclei with A = 7, 13 and 14 by calculating their spectra with and without the three-body diagram. It is found that for the heavier nuclei, neglect of this part of the effective force is not justified. The calculations

B. Singh

1974-01-01

188

Test bodies and naked singularities: is the self-force the cosmic censor?  

PubMed

Jacobson and Sotiriou showed that rotating black holes could be spun up past the extremal limit by the capture of nonspinning test bodies, if one neglects radiative and self-force effects. This would represent a violation of the cosmic censorship conjecture in four-dimensional, asymptotically flat spacetimes. We show that for some of the trajectories giving rise to naked singularities, radiative effects can be neglected. However, for these orbits the conservative self-force is important, and seems to have the right sign to prevent the formation of naked singularities. PMID:21231640

Barausse, Enrico; Cardoso, Vitor; Khanna, Gaurav

2010-12-31

189

A preliminary investigation of the dynamic force-calibration of a magnetic suspension and balance system  

NASA Technical Reports Server (NTRS)

The aerodynamic forces and moments acting upon a magnetically suspended wind tunnel model are derived from calibrations of suspension electro magnet currents against known forces. As an alternative to the conventional calibration method of applying steady forces to the model, early experiences with dynamic calibration are outlined, that is a calibration obtained by oscillating a model in suspension and deriving a force/current relationship from its inertia force and the unsteady components of currents. Advantages of dynamic calibration are speed and simplicity. The two methods of calibration applied to one force component show good agreement.

Goodyer, M. J.

1985-01-01

190

Induction of electromotive force by an autonomously moving magnetic bot.  

PubMed

We report the observation of the induction of electromotive force (emf) into a Faraday coil by an autonomously moving composite magnetic particle in aqueous medium. The particle consisted of a micron-sized polymer sphere, which was decorated with catalytic Pd nanoparticles (NPs) and attached to a micron-scale (N-42 grade) rare-earth magnet. The Pd NPs catalytically decomposed H2 O2 to generate O2 , resulting in buoyancy-driven vertical motion of the particle, while the micromagnet induced emf during the flight. Because a small volume of ethanol was layered on top of the liquid, the bubble burst when the particle ascended to the top and thus nearly continuous vertical motion was achieved. Spikes of alternating electrical signal could be observed up to 20?times per minute. The signal was sufficiently strong to illuminate light-emitting diodes following appropriate amplification. This distinctive approach is expected to pave the way to developing synthetic bots which are autonomously propelled, generating their own signal for running complex circuitry. PMID:24492970

Sailapu, Sunil Kumar; Chattopadhyay, Arun

2014-02-01

191

Optical Response of Magnetic-Fluorescent Microspheres Used for Force Spectroscopy in the Evanescent Field  

PubMed Central

Force spectroscopy based on magnetic tweezers is a powerful technique to manipulate single biomolecules and study their interactions. The resolution in a magnetic probe displacement, however, needs to be commensurate with molecular sizes. To achieve the desirable sensitivity in tracking displacements of the magnetic probe, some recent approaches have combined magnetic tweezers with total internal reflection fluorescence microscopy. In this situation, a typical force probe is a polymer microsphere containing two types of optically active components a pure absorber (magnetic nanoparticles for providing the pulling force) and a luminophore (semiconducting nanoparticles or organic dyes for fluorescent imaging). In order to fully assess the systems capability for tracking the position of the force probe with sub-nanometer accuracy, we developed a body-of-revolution formulation of the method of auxiliary sources (BOR-MAS) to simulate absorption, scattering, and fluorescence of microscopic spheres in an evanescent electromagnetic field. The theoretical formulation uses the axial symmetry of the system to reduce the dimensionality of the modeling problem and produces excellent agreement with the reported experimental data on forward scattering intensity. Using the BOR-MAS numerical model, we investigated the probe detection sensitivity for a high numerical aperture objective. The analysis of both backscattering and fluorescence observation modes shows that the total intensity of the bead image decays exponentially with the distance from the surface (or the length of a biomolecule). Our investigations demonstrate that the decay lengths of observable optical power are smaller than the penetration depth of the unperturbed excitation evanescent wave. In addition, our numerical modeling results illustrate that the expected sensitivity for the decay length changes with the incident angle, tracking the theoretical penetration depth for a two-media model, and is sensitive to the bead size. The BOR-MAS methodology developed in this work for near field modeling of bead tracking experiments fully describes the fundamental photonic response of microscopic BOR probes at the sub-wavelength level and can be used for future improvements in the design of these probes or in the setup of bead tracking experiments. PMID:20486724

Bijamov, Alex; Shubitidze, Fridon; Oliver, Piercen M.; Vezenov, Dmitri V.

2010-01-01

192

Some results of adding solar radiation pressure force to the restricted three-body problem  

NASA Astrophysics Data System (ADS)

This work explores the generation of bounded orbits in the Elliptic Restricted Three-Body Problem (ER3BP), and some of the results of adding the solar radiation pressure force to the ER3BP are presented. The focus is limited to the equilibrium points defined in the Sun-Earth ER3BP. (These equilibrium points are also referred to as libration points or Lagrange points.) The addition of solar radiation pressure to the gravitational and centrifugal force structure alters the locations and conditions for linear stability of the equilibrium points in the Sun-Earth ER3BP. Solar radiation pressure also consequently affects the spacecraft orbits computed near these points. One equilibrium point in this three-body system is located between the Sun and the Earth; orbits near this point are the primary focus for the study of solar effects on the terrestrial environment and are therefore the orbits considered here.

Gordon, Steven C.

1991-09-01

193

Numerical Pattern Formation on Magnetothermal Convection of Diamagnetic Liquids in a Cylindrical Vessel of RayleighBenard Model: Effects of Axisymmetric Horizontal Magnetic Forces on Vertical Magnetic Forces  

NASA Astrophysics Data System (ADS)

We carried out three-dimensional computations of the magnetothermal convection of diamagnetic liquids (e.g., water) in a shallow cylindrical vessel of the RayleighBenard model to investigate the effects of the radial components of the magnetic force (MFR) and the vertical components of the magnetic force (MFZ) on heat transfer and pattern formation. For the purpose of examining various magnitudes of radial and vertical components of the magnetic force, we used a 1800-turn coil instead of an actual conventional magnet, and a 2-turn coil as a new proposal. In the computation, the Prandtl number was constant at 6.0 (i.e., water at room temperature), and the Rayleigh number was 1.0 104. As a result, an axisymmetric pattern and a spokelike pattern appeared in the convection. Subsequently, we arranged all the results with a new parameter, which is the absolute ratio of the radial component of magnetic force at the vessel sidewall to the vertical resultant force at the vessel center. This parameter represents the relative contribution of MFR to the vertical resultant force (RFZ). The RFZ is the sum of the gravitational force and MFZ, and is associated with the magnetic Rayleigh number. By using this parameter, the spoke pattern convection appeared when the parameter was within 0.11 to 0.85. This result suggests that not only the MFR but also the MFZ plays an important role in determining whether the convection flow pattern transited to the axisymmetric flow or not. This parameter range is easily satisfied in a conventional superconducting magnet. We can say that the spoke pattern convection may be a common phenomenon in the magnet. On the other hand, the flow pattern had little effect on the heat transfer in convection. Thus, the effects of MFR and MFZ on the pattern formation in the magnet are much more complicated than those previously considered.

Maki, Syou; Sumitani, Mariko; Udagawa, Chikako; Morimoto, Shotaro; Tanimoto, Yoshifumi

2014-07-01

194

Formation of magnetic discontinuities through superposition of force-free magnetic fields: Periodic boundaries  

NASA Astrophysics Data System (ADS)

In ideal magnetohydrodynamics characterized by an infinite electrical conductivity, the magnetic flux across an arbitrary fluid surface is conserved in time. The magnetofluid then can be partitioned into contiguous subvolumes of fluid, each of which entraps its own subsystem of magnetic flux. During dynamical evolution of the magnetofluid, these subvolumes press into each other; and in the process, two such subvolumes may come into direct contact while ejecting a third interstitial subvolume. Depending on the orientations of magnetic fields of the two interacting subvolumes, the magnetic field at the common surface of interaction may become discontinuous and a current sheet is formed there. This process of current sheet formation and their subsequent decay is believed to be a plausible mechanism for coronal heating and may also be responsible for various eruptive phenomena at the solar corona. In this work, we explore this theoretical concept through numerical simulations of a viscous, incompressible magnetofluid characterized by infinite electrical conductivity. In particular, we show that if the initial magnetic field is prescribed by superposition of two linear force-free fields with different torsion coefficients, then formation of current sheets are numerically realizable in the neighborhood of magnetic nulls.

Kumar, Dinesh; Bhattacharyya, R.; Smolarkiewicz, P. K.

2013-11-01

195

Transformation of body force localized near the surface of a half-space into equivalent surface stresses.  

PubMed

An electromagnetic acoustic transducer (EMAT) or a laser used to generate elastic waves in a component is often described as a source of body force confined in a layer close to the surface. On the other hand, models for elastic wave radiation more efficiently handle sources described as distributions of surface stresses. Equivalent surface stresses can be obtained by integrating the body force with respect to depth. They are assumed to generate the same field as the one that would be generated by the body force. Such an integration scheme can be applied to Lorentz force for conventional EMAT configuration. When applied to magnetostrictive force generated by an EMAT in a ferromagnetic material, the same scheme fails, predicting a null stress. Transforming body force into equivalent surface stresses therefore, requires taking into account higher order terms of the force moments, the zeroth order being the simple force integration over the depth. In this paper, such a transformation is derived up to the second order, assuming that body forces are localized at depths shorter than the ultrasonic wavelength. Two formulations are obtained, each having some advantages depending on the application sought. They apply regardless of the nature of the force considered. PMID:24116402

Rouge, Clmence; Lhmery, Alain; Sgur, Damien

2013-10-01

196

Multi-body simulation of a canine hind limb: model development, experimental validation and calculation of ground reaction forces  

PubMed Central

Background Among other causes the long-term result of hip prostheses in dogs is determined by aseptic loosening. A prevention of prosthesis complications can be achieved by an optimization of the tribological system which finally results in improved implant duration. In this context a computerized model for the calculation of hip joint loadings during different motions would be of benefit. In a first step in the development of such an inverse dynamic multi-body simulation (MBS-) model we here present the setup of a canine hind limb model applicable for the calculation of ground reaction forces. Methods The anatomical geometries of the MBS-model have been established using computer tomography- (CT-) and magnetic resonance imaging- (MRI-) data. The CT-data were collected from the pelvis, femora, tibiae and pads of a mixed-breed adult dog. Geometric information about 22 muscles of the pelvic extremity of 4 mixed-breed adult dogs was determined using MRI. Kinematic and kinetic data obtained by motion analysis of a clinically healthy dog during a gait cycle (1 m/s) on an instrumented treadmill were used to drive the model in the multi-body simulation. Results and Discussion As a result the vertical ground reaction forces (z-direction) calculated by the MBS-system show a maximum deviation of 1.75%BW for the left and 4.65%BW for the right hind limb from the treadmill measurements. The calculated peak ground reaction forces in z- and y-direction were found to be comparable to the treadmill measurements, whereas the curve characteristics of the forces in y-direction were not in complete alignment. Conclusion In conclusion, it could be demonstrated that the developed MBS-model is suitable for simulating ground reaction forces of dogs during walking. In forthcoming investigations the model will be developed further for the calculation of forces and moments acting on the hip joint during different movements, which can be of help in context with the in silico development and testing of hip prostheses. PMID:19930616

2009-01-01

197

Numerical analysis on the action of centrifuge force in magnetic fluid rotating shaft seals  

NASA Astrophysics Data System (ADS)

The magnetic fluid seal is suitable for high-speed rotating shaft seal applications. Centrifuge force will have evident influence on magnetic fluid rotating shaft seals. The seal capacity of the rotating shaft seal can be improved or increased by some measures. Through hydrodynamic analysis the moving status of the magnetic fluid is worked out. By numerical method, the magnetic field and the isobars in the magnetic fluid of a seal device are computed. Then the influence of the centrifuge force on the magnetic fluid seal is calculated quantitatively.

Zou, Jibin; Li, Xuehui; Lu, Yongping; Hu, Jianhui

2002-11-01

198

High-field magnetic force microscopy as susceptibility imaging Casey Israel, Weida Wu, and Alex de Lozannea  

E-print Network

High-field magnetic force microscopy as susceptibility imaging Casey Israel, Weida Wu, and Alex de an extension of variable-temperature magnetic force microscopy MFM that allows spatial discrimination between.1063/1.2221916 Magnetic force microscopy MFM was developed as a scanning probe technique for mapping out magnetic field

Wu, Weida

199

Effects of three-nucleon forces and two-body currents on gamow-teller strengths.  

PubMed

We optimize chiral interactions at next-to-next-to leading order to observables in two- and three-nucleon systems and compute Gamow-Teller transitions in ^{14}C and ^{22,24}O using consistent two-body currents. We compute spectra of the daughter nuclei ^{14}N and ^{22,24}F via an isospin-breaking coupled-cluster technique, with several predictions. The two-body currents reduce the Ikeda sum rule, corresponding to a quenching factor q^{2}?0.84-0.92 of the axial-vector coupling. The half-life of ^{14}C depends on the energy of the first excited 1^{+} state, the three-nucleon force, and the two-body current. PMID:25615316

Ekstrm, A; Jansen, G R; Wendt, K A; Hagen, G; Papenbrock, T; Bacca, S; Carlsson, B; Gazit, D

2014-12-31

200

Investigation of Body Force Effects on Flow Boiling Critical Heat Flux  

NASA Technical Reports Server (NTRS)

The bubble coalescence and interfacial instabilities that are important to modeling critical heat flux (CHF) in reduced-gravity systems can be sensitive to even minute body forces. Understanding these complex phenomena is vital to the design and safe implementation of two-phase thermal management loops proposed for space and planetary-based thermal systems. While reduced gravity conditions cannot be accurately simulated in 1g ground-based experiments, such experiments can help isolate the effects of the various forces (body force, surface tension force and inertia) which influence flow boiling CHF. In this project, the effects of the component of body force perpendicular to a heated wall were examined by conducting 1g flow boiling experiments at different orientations. FC-72 liquid was boiled along one wall of a transparent rectangular flow channel that permitted photographic study of the vapor-liquid interface at conditions approaching CHF. High-speed video imaging was employed to capture dominant CHF mechanisms. Six different CHF regimes were identified: Wavy Vapor Layer, Pool Boiling, Stratification, Vapor Counterflow, Vapor Stagnation, and Separated Concurrent Vapor Flow. CHF showed great sensitivity to orientation for flow velocities below 0.2 m/s, where very small CHF values where measured, especially with downflow and downward-facing heated wall orientations. High flow velocities dampened the effects of orientation considerably. Figure I shows representative images for the different CHF regimes. The Wavy Vapor Layer regime was dominant for all high velocities and most orientations, while all other regimes were encountered at low velocities, in the downflow and/or downward-facing heated wall orientations. The Interfacial Lift-off model was modified to predict the effects of orientation on CHF for the dominant Wavy Vapor Layer regime. The photographic study captured a fairly continuous wavy vapor layer travelling along the heated wall while permitting liquid contact only in wetting fronts, located in the troughs of the interfacial waves. CHF commenced when wetting fronts near the outlet were lifted off the wall. The Interfacial Lift-off model is shown to be an effective tool for predicting the effects of body force on CHF at high velocities.

Zhang, Hui; Mudawar, Issam; Hasan, Mohammad M.

2002-01-01

201

Orthodontic magnets. A study of force and field pattern, biocompatibility and clinical effects.  

PubMed

Magnetic forces have been incorporated into orthodontic mechanics during recent years. However, the biocompatibility of magnet alloys and the possible risk of harmful or unusual reactions in tissues exposed to static magnetic fields have been characterized as inconsistent and often contradictory. It has also been questioned whether magnetic forces have significant advantages over traditional mechanics. The present series of studies aimed to analyse the force and field properties, the biocompatibility and the clinical effects of rare earth magnets as well as to compare the efficiency of tooth movement between magnets and another force system. Samarium-cobalt magnets for molar distalization were tested in experimental models for force and field properties. The cytotoxicity of different magnet alloys (rare earth types) as well as of clinically used and recycled magnets was assessed by two in vitro methods, the millipore filter method and an extraction method. The effect of static magnetic fields on human gingival tissue and dental pulp was examined histologically for alterations in cell pattern and cell morphology. The effects of using repelling samarium-cobalt magnets for simultaneous distalization of maxillary first and second molars were analysed in individuals with Class II malocclusion. The efficiency of molar distalization was also intra-individually compared between repelling magnets and superelastic NiTi-coils in individuals with Class II malocclusion and deep bite. The magnet forces decreased approximately with the reciprocal square of the separation distance between the magnets. No fatigue of force over time could be seen. The static magnetic fields were weak and had a limited extent and the flux density dropped exponentially in all directions with increased distance from the magnets, implying a small exposure area when the magnets are used clinically. Rare earth magnets showed good biocompatibility, particularly coated magnets. However, uncoated samarium-cobalt magnets showed significant cytotoxicity. It was also found that stainless-steel-coated samarium-cobalt magnets could be recycled with maintained good biocompatibility. After exposure to static magnetic fields, normal clinical and histological conditions in the human gingival tissue and normal histological features in the human dental pulp were found. Repelling magnets were effective in producing maxillary molar distalization but some side effects like anchorage loss and molar tipping were found. The superelastic coils were shown to be even more efficient than the repelling magnets for maxillary molar distalization in individuals with Class II malocclusion and deep bite. PMID:7801229

Bondemark, L

1994-01-01

202

Task III: Development of an Effective Computational Methodology for Body Force Representation of High-speed Rotor 37  

NASA Technical Reports Server (NTRS)

A framework for an effective computational methodology for characterizing the stability and the impact of distortion in high-speed multi-stage compressor is being developed. The methodology consists of using a few isolated-blade row Navier-Stokes solutions for each blade row to construct a body force database. The purpose of the body force database is to replace each blade row in a multi-stage compressor by a body force distribution to produce same pressure rise and flow turning. To do this, each body force database is generated in such a way that it can respond to the changes in local flow conditions. Once the database is generated, no hrther Navier-Stokes computations are necessary. The process is repeated for every blade row in the multi-stage compressor. The body forces are then embedded as source terms in an Euler solver. The method is developed to have the capability to compute the performance in a flow that has radial as well as circumferential non-uniformity with a length scale larger than a blade pitch; thus it can potentially be used to characterize the stability of a compressor under design. It is these two latter features as well as the accompanying procedure to obtain the body force representation that distinguish the present methodology from the streamline curvature method. The overall computational procedures have been developed. A dimensional analysis was carried out to determine the local flow conditions for parameterizing the magnitudes of the local body force representation of blade rows. An Euler solver was modified to embed the body forces as source terms. The results from the dimensional analysis show that the body forces can be parameterized in terms of the two relative flow angles, the relative Mach number, and the Reynolds number. For flow in a high-speed transonic blade row, they can be parameterized in terms of the local relative Mach number alone.

Tan, Choon-Sooi; Suder, Kenneth (Technical Monitor)

2003-01-01

203

Frustrated magnetic vortices in a triad of permalloy rings: Magneto-optical Kerr effect, magnetic force microscopy, and micromagnetic simulations  

Microsoft Academic Search

The field dependent magnetization of three mutually touching permalloy rings were investigated by means of the magneto-optical Kerr effect, magnetic force microscopy, and micromagnetic simulations. Each ring has a width of 0.2-1.8mum , an outer diameter of 4mum , and a thickness of 17nm . Decreasing an applied magnetic field from saturation leads to the nucleation and annihilation of magnetic

V. Rose; K. Buchanan; S.-H. Chung; M. Grimsditch; V. Metlushko; A. Hoffmann; V. Novosad; S. D. Bader; H. Ibach

2006-01-01

204

GravitoMagnetic force in modified Newtonian dynamics  

NASA Astrophysics Data System (ADS)

We introduce the Gauge Vector-Tensor (GVT) theory by extending the AQUAL's approach to the GravitoElectroMagnetism (GEM) approximation of gravity. GVT is a generally covariant theory of gravity composed of a pseudo Riemannian metric and two U(1) gauge connections that reproduces MOND in the limit of very weak gravitational fields while remains consistent with the Einstein-Hilbert gravity in the limit of strong and Newtonian gravitational fields. GVT also provides a simple framework to study the GEM approximation to gravity. We illustrate that the gravitomagnetic force at the edge of a galaxy can be in accord with either GVT or ?CDM but not both. We also study the physics of the GVT theory around the gravitational saddle point of the Sun and Jupiter system. We notice that the conclusive refusal of the GVT theory demands measuring either both of the gravitoelectric and gravitomagnetic fields inside the Sun-Jupiter MOND window, or the gravitoelectric field inside two different solar GVT MOND windows. The GVT theory, however, will be favored by observing an anomaly in the gravitoelectric field inside a single MOND window.

Exirifard, Qasem

2013-08-01

205

Estimation of the radial force using a disturbance force observer for a magnetically levitated centrifugal blood pump.  

PubMed

Evaluation of the hydraulic forces in a magnetically levitated (maglev) centrifugal blood pump is important from the point of view of the magnetic bearing design. Direct measurement is difficult due to the absence of a rotor shaft, and computational fluid dynamic analysis demands considerable computational resource and time. To solve this problem, disturbance force observers were developed, using the radial controlled magnetic bearing of a centrifugal blood pump, to estimate the radial forces on the maglev impeller. In order to design the disturbance observer, the radial dynamic characteristics of a maglev impeller were evaluated under different working conditions. It was observed that the working fluid affects the additional mass and damping, while the rotational speed affects the damping and stiffness of the maglev system. Based on these results, disturbance force observers were designed and implemented. The designed disturbance force observers present a bandwidth of 45 Hz. In non-pulsatile conditions, the magnitude of the estimated radial thrust increases in proportion to the flowrate, and the rotational speed has little effect on the force direction. At 5 l/min against 100 mmHg, the estimated radial thrust is 0.95 N. In pulsatile conditions, this method was capable of estimating the pulsatile radial thrust with good response. PMID:20839658

Pai, C N; Shinshi, T; Shimokohbe, A

2010-01-01

206

Aerodynamic force generation, performance and control of body orientation during gliding in sugar gliders (Petaurus breviceps).  

PubMed

Gliding has often been discussed in the literature as a possible precursor to powered flight in vertebrates, but few studies exist on the mechanics of gliding in living animals. In this study I analyzed the 3D kinematics of sugar gliders (Petaurus breviceps) during short glides in an enclosed space. Short segments of the glide were captured on video, and the positions of marked anatomical landmarks were used to compute linear distances and angles, as well as whole body velocities and accelerations. From the whole body accelerations I estimated the aerodynamic forces generated by the animals. I computed the correlations between movements of the limbs and body rotations to examine the control of orientation during flight. Finally, I compared these results to those of my earlier study on the similarly sized and distantly related southern flying squirrel (Glaucomys volans). The sugar gliders in this study accelerated downward slightly (1.0+/-0.5 m s(-2)), and also accelerated forward (2.1+/-0.6 m s(-2)) in all but one trial, indicating that the body weight was not fully supported by aerodynamic forces and that some of the lift produced forward acceleration rather than just balancing body weight. The gliders used high angles of attack (44.15+/-3.12 degrees ), far higher than the angles at which airplane wings would stall, yet generated higher lift coefficients (1.48+/-0.18) than would be expected for a stalled wing. Movements of the limbs were strongly correlated with body rotations, suggesting that sugar gliders make extensive use of limb movements to control their orientation during gliding flight. In addition, among individuals, different limb movements were associated with a given body rotation, suggesting that individual variation exists in the control of body rotations. Under similar conditions, flying squirrels generated higher lift coefficients and lower drag coefficients than sugar gliders, yet had only marginally shallower glides. Flying squirrels have a number of morphological specializations not shared by sugar gliders that may help to explain their greater lift generating performance. PMID:17644674

Bishop, Kristin L

2007-08-01

207

Phase combination for self-cancellation of magnetic force in undulators  

NASA Astrophysics Data System (ADS)

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

Kinjo, Ryota; Tanaka, Takashi

2014-12-01

208

Equal sensation curves for whole-body vibration expressed as a function of driving force  

NASA Astrophysics Data System (ADS)

Previous studies have shown that the seated human is most sensitive to whole-body vertical vibration at about 5 Hz. Similarly, the body shows an apparent mass resonance at about 5 Hz. Considering these similarities between the biomechanical and subjective responses, it was hypothesized that, at low frequencies, subjective ratings of whole-body vibration might be directly proportional to the driving force. Twelve male subjects participated in a laboratory experiment where subjects sat on a rigid seat mounted on a shaker. The magnitude of a test stimulus was adjusted such that the subjective intensity could be matched to a reference stimulus, using a modified Bruceton test protocol. The sinusoidal reference stimulus was 8-Hz vibration with a magnitude of 0.5 m/s2 rms (or 0.25 m/s2 rms for the 1-Hz test); the sinusoidal test stimuli had frequencies of 1, 2, 4, 16, and 32 Hz. Equal sensation contours in terms of seat acceleration showed data similar to those in the literature. Equal sensation contours in terms of force showed a nominally linear response at 1, 2, and 4 Hz, but an increasing sensitivity at higher frequencies. This is in agreement with a model derived from published subjective and objective fitted data. .

Mansfield, Neil J.; Maeda, Setsuo

2005-06-01

209

Modified approach to single-spin detection using magnetic resonance force microscopy  

Microsoft Academic Search

The magnetic moment of a single spin interacting with a cantilever in magnetic resonance force microscopy (MRFM) experiences quantum jumps in orientation rather than smooth oscillations. These jumps cannot be detected by a conventional MRFM based on observation of driven resonant oscillations of a cantilever. In this paper, we propose a method which should allow detection of the magnetic signal

Gennady P. Berman; Vladimir I. Tsifrinovich

2000-01-01

210

Bifurcation of force-free solar magnetic fields: A numerical approach  

Microsoft Academic Search

Numerical calculations of two-dimensional force-free fields as models of solar active regions are presented. For a given toroidal component of the photospheric magnetic field two branches of solutions are numerically obtained which merge at the critical point of maximum allowed toroidal magnetic field. Depending on boundary conditions magnetic islands may or may not form. The results are discussed with respect

Klaus Jockers

1978-01-01

211

Ordered behaviour in force-free magnetic fields  

NASA Astrophysics Data System (ADS)

Conditions in order that the trajectories of a force-free vectorfield lie on the level sets of a given function are studied. Force-free vectorfields symmetric under translations, rotations and roto-translations are also considered.

Gonzalez-Gascon, F.; Peralta-Salas, D.

2001-12-01

212

Inversion of magnetic forces between microparticles and its effect on the magnetorheology of extremely bidisperse magnetic fluids  

E-print Network

1 Inversion of magnetic forces between microparticles and its effect on the magnetorheology are in contact and aligned in the field direction. This is the basic phenomenon underlying the magnetorheological

Paris-Sud XI, Université de

213

Constraint Force Equation Methodology for Modeling Multi-Body Stage Separation Dynamics  

NASA Technical Reports Server (NTRS)

This paper discusses a generalized approach to the multi-body separation problems in a launch vehicle staging environment based on constraint force methodology and its implementation into the Program to Optimize Simulated Trajectories II (POST2), a widely used trajectory design and optimization tool. This development facilitates the inclusion of stage separation analysis into POST2 for seamless end-to-end simulations of launch vehicle trajectories, thus simplifying the overall implementation and providing a range of modeling and optimization capabilities that are standard features in POST2. Analysis and results are presented for two test cases that validate the constraint force equation methodology in a stand-alone mode and its implementation in POST2.

Toniolo, Matthew D.; Tartabini, Paul V.; Pamadi, Bandu N.; Hotchko, Nathaniel

2008-01-01

214

Verification of a Constraint Force Equation Methodology for Modeling Multi-Body Stage Separation  

NASA Technical Reports Server (NTRS)

This paper discusses the verification of the Constraint Force Equation (CFE) methodology and its implementation in the Program to Optimize Simulated Trajectories II (POST2) for multibody separation problems using three specially designed test cases. The first test case involves two rigid bodies connected by a fixed joint; the second case involves two rigid bodies connected with a universal joint; and the third test case is that of Mach 7 separation of the Hyper-X vehicle. For the first two cases, the POST2/CFE solutions compared well with those obtained using industry standard benchmark codes, namely AUTOLEV and ADAMS. For the Hyper-X case, the POST2/CFE solutions were in reasonable agreement with the flight test data. The CFE implementation in POST2 facilitates the analysis and simulation of stage separation as an integral part of POST2 for seamless end-to-end simulations of launch vehicle trajectories.

Tartabini, Paul V.; Roithmayr, Carlos; Toniolo, Matthew D.; Karlgaard, Christopher; Pamadi, Bandu N.

2008-01-01

215

Gravitational self-force corrections to two-body tidal interactions and the effective one-body formalism  

NASA Astrophysics Data System (ADS)

Tidal interactions have a significant influence on the late dynamics of compact binary systems, which constitute the prime targets of the upcoming network of gravitational-wave detectors. We refine the theoretical description of tidal interactions (hitherto known only to the second post-Newtonian level) by extending our recently developed analytic self-force formalism, for extreme-mass-ratio binary systems, to the computation of several tidal invariants. Specifically, we compute, to linear order in the mass ratio and to the 7.5th post-Newtonian order, the following tidal invariants: the square and the cube of the gravitoelectric quadrupolar tidal tensor, the square of the gravitomagnetic quadrupolar tidal tensor, and the square of the gravitoelectric octupolar tidal tensor. Our high-accuracy analytic results are compared to recent numerical self-force tidal data by Dolan et al. [arXiv:1406.4890 [Phys. Rev. D (to be published)] ], and, notably, provide an analytic understanding of the light ring asymptotic behavior found by them. We transcribe our kinematical tidal-invariant results in the more dynamically significant effective one-body description of the tidal interaction energy. By combining, in a synergetic manner, analytical and numerical results, we provide simple, accurate analytic representations of the global, strong-field behavior of the gravitoelectric quadrupolar tidal factor. A striking finding is that the linear-in-mass-ratio piece in the latter tidal factor changes sign in the strong-field domain, to become negative (while its previously known second post-Newtonian approximant was always positive). We, however, argue that this will be more than compensated by a probable fast growth, in the strong-field domain, of the nonlinear-in-mass-ratio contributions in the tidal factor.

Bini, Donato; Damour, Thibault

2014-12-01

216

Gravitational self-force corrections to two-body tidal interactions and the effective one-body formalism  

E-print Network

Tidal interactions have a significant influence on the late dynamics of compact binary systems, which constitute the prime targets of the upcoming network of gravitational-wave detectors. We refine the theoretical description of tidal interactions (hitherto known only to the second post-Newtonian level) by extending our recently developed analytic self-force formalism, for extreme mass-ratio binary systems, to the computation of several tidal invariants. Specifically, we compute, to linear order in the mass ratio and to the 7.5$^{\\rm th}$ post-Newtonian order, the following tidal invariants: the square and the cube of the gravitoelectric quadrupolar tidal tensor, the square of the gravitomagnetic quadrupolar tidal tensor, and the square of the gravitoelectric octupolar tidal tensor. Our high-accuracy analytic results are compared to recent numerical self-force tidal data by Dolan et al. \\cite{Dolan:2014pja}, and, notably, provide an analytic understanding of the light ring asymptotic behavior found by them. We transcribe our kinematical tidal-invariant results in the more dynamically significant effective one-body description of the tidal interaction energy. By combining, in a synergetic manner, analytical and numerical results, we provide simple, accurate analytic representations of the global, strong-field behavior of the gravitoelectric quadrupolar tidal factor. A striking finding is that the linear-in-mass-ratio piece in the latter tidal factor changes sign in the strong-field domain, to become negative (while its previously known second post-Newtonian approximant was always positive). We, however, argue that this will be more than compensated by a probable fast growth, in the strong-field domain, of the nonlinear-in-mass-ratio contributions in the tidal factor.

Donato Bini; Thibault Damour

2014-09-24

217

Nonlinear force-free modeling of the solar coronal magnetic field  

E-print Network

The coronal magnetic field is an important quantity because the magnetic field dominates the structure of the solar corona. Unfortunately direct measurements of coronal magnetic fields are usually not available. The photospheric magnetic field is measured routinely with vector magnetographs. These photospheric measurements are extrapolated into the solar corona. The extrapolated coronal magnetic field depends on assumptions regarding the coronal plasma, e.g. force-freeness. Force-free means that all non-magnetic forces like pressure gradients and gravity are neglected. This approach is well justified in the solar corona due to the low plasma beta. One has to take care, however, about ambiguities, noise and non-magnetic forces in the photosphere, where the magnetic field vector is measured. Here we review different numerical methods for a nonlinear force-free coronal magnetic field extrapolation: Grad-Rubin codes, upward integration method, MHD-relaxation, optimization and the boundary element approach. We briefly discuss the main features of the different methods and concentrate mainly on recently developed new codes.

T. Wiegelmann

2008-01-18

218

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

E-print Network

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

Grütter, Peter

219

IEEE TRANSACTIONS ON NANOTECHNOLOGY, VOL. 9, NO. 3, MAY 2010 367 Controlling a Magnetic Force Microscope to Track a  

E-print Network

Terms--Magnetic force microscopy (MFM), nanotechnol- ogy, nonlinear systems, particle tracking. IIEEE TRANSACTIONS ON NANOTECHNOLOGY, VOL. 9, NO. 3, MAY 2010 367 Controlling a Magnetic Force moving in three dimensions using a mag- netic force microscope (MFM). The stray magnetic field

220

Force measurements in magnetic bearings using fiber optic strain gauges  

E-print Network

on Magnetic Bearings, Zurich, pp. 157-163. Bendat, J. , Piersol, A. , 1980, Engineering Applications of Correlation and Spectral Analysis, Wiley Interscience, New York. Fiber Dynamics Inc. , 1999, SCU-/00 Signal Conditioning Unit Instruction Manual..., " The Fourth International Symposium on Magnetic Bearings, Zurich, pp. 305-309. Revolve Magnetic Bearings Inc. , "Magnetic Bearing Systems Basic Principles of Operation", 2000 [Accessed March 2000], Available: http: //www. revolve. corn. Rouvas, C. , 1993...

Raymer, Stephen Geoffrey

2000-01-01

221

Turbulence Modeling of Non-equilibrium Flows Using Turbulent Body Force Potentials  

NASA Astrophysics Data System (ADS)

Results of a new turbulence model for non-equilibrium flow which is based on turbulent body force potentials are presented. Initial predictions of the model for basic turbulent flows produced promising results. This work concentrates on predicting more complex and realistic turbulent flows that are similar to the problems in design and manufacturing process. Three major cases are presented and the computational results are compared with existing experimental data and DNS data whenever possible. First, backwards-facing step flows at both high and low Reynolds numbers are investigated in order to evaluate the model's ability for correctly predicting separation and reattachment. Second, two adverse pressure gradient flows are analyzed, namely, the classic Samuel & Joubert flow and more severe case documented by Schubauer & Spangenberg. Finally, the performance of the model in predicting stagnation flows is evaluated by investigating planar and axisymmetric impinging jets. Comparisons show that model predictions match well with experimental data and DNS data. It is demonstrated that by introducing turbulent body force potentials this new non-equilibrium turbulence model is able to predict complex turbulent flows as well as Reynolds stress transport models with significant less computational cost and complexity.

Wang, Hudong; Perot, Blair

1998-11-01

222

Lorentz force time-optimal transfer trajectory design in Jovian magnetic field  

NASA Astrophysics Data System (ADS)

In this paper, the Lorentz force in Jupiter's magnetic field is used to design the transfer trajectory between Galileo moons' Lagrange points. The equatorial orbits of charged spacecraft in three-body axis-aligned nontilted-dipole magnetic field model are analyzed and the results show that the libration point L1 and L2 become nearer or further away from Europa with the variable size and polarity of the charge. The bang-bang charge control with the variable size and polarity of the charge can be used to change orbit's direction and shape. Analytical and numerical iteration methods give the fast and accurate bang-bang charge control to send the spacecraft to the L2 point of Europa, respectively. Finally, two numerical methods, the indirect and direct methods, give the time-optimal charge controls which are similar to but different from the semi-revolution variable polarity control maneuver. The optimal results achieve the final position and the flight angle at the same time, and need less time and less magnitude of charge compared with the numerical iteration method.

Zhang, Zhiguo; Gong, Shengping; Li, Junfeng

2015-02-01

223

Different types of ferrite thin films as magnetic cantilever coating for magnetic force microscopy  

NASA Astrophysics Data System (ADS)

Different types of ferrites are employed in the form of thin films as magnetic coating on cantilevers for magnetic force microscopy (MFM) use. This is especially needed for cantilevers employed in high-frequency MFM (HF-MFM), where stray fields of hard disk recording heads are investigated. Our experiments show that we can operate HF-MFM successfully at carrier frequencies up 2 GHz using such ferrite-coated cantilevers. Thin films of two ferrites, NiZnFe 2O 4 spinel ferrite and Co 2 Z-type hexaferrite (Ba 3Co 2Fe 24O 41, BCFO) were prepared by RF sputtering. As a basis for these probes, we employ commercial micromachined silicon cantilevers. Additionally, films on Si (1 0 0) and Si (1 1 1)-oriented substrates with a thickness up to 100 nm were prepared for analysis purposes, enabling the optimization of the sputter process. For a high spatial resolution of MFM, however, thinner magnetic coatings are required. Therefore, the third type, c, was prepared by laser-ablation with a thickness of 30 nm, also directly onto the Si without additional buffer layer.

Koblischka, M. R.; Kirsch, M.; Pfeifer, R.; Getlawi, S.; Rigato, F.; Fontcuberta, J.; Sulzbach, T.; Hartmann, U.

2010-05-01

224

Energy balance and body composition during US Army special forces training.  

PubMed

Small Unit Tactics (SUT) is a 64-day phase of the Special Forces Qualification Course designed to simulate real-world combat operations. Assessing the metabolic and physiological responses of such intense training allows greater insights into nutritional requirements of soldiers during combat. The purpose of this study was to examine energy balance around specific training events, as well as changes in body mass and composition. Data were collected from 4 groups of soldiers (n = 36) across 10-day periods. Participants were 28 5 years old, 177 6 cm tall, and weighed 83 7 kg. Doubly labeled water (D2(18)O) was used to assess energy expenditure. Energy intake was calculated by subtracting energy in uneaten foods from known energy in distributed foods in individually packaged combat rations or in the dining facility. Body composition was estimated from skinfold thickness measurements on days 0 and 64 of the course. Simulated urban combat elicited that largest energy deficit (11.3 2.3 MJday(-1) (2700 550 kcalday(-1)); p < 0.05), and reduction in body mass (3.3 1.9 kg; p < 0.05), during SUT, while energy balance was maintained during weapons familiarization training and platoon size raids. Over the entire course body mass decreased by 4.2 3.7 kg (p < 0.01), with fat mass decreasing by 2.8 2.0 kg (p < 0.01) and fat-free mass decreasing by 1.4 2.8 kg (p < 0.05). The overall reduction in body mass suggests that soldiers were in a negative energy balance during SUT, with high energy deficit being observed during strenuous field training. PMID:23713532

Margolis, Lee M; Rood, Jennifer; Champagne, Catherine; Young, Andrew J; Castellani, John W

2013-04-01

225

Investigation of the behavior of a magnetic fluid in displacement and force transducers  

SciTech Connect

The behavior of a drop of magnetic fluid in a capillary tube was investigated with reference to displacement and force transducers. The design of the sensing element of a magnetic fluid transducer was examined to investigate the shape of the meniscus of the column of magnetic fluid in a glass capillary tube under a longitudinal uniform magnetic field stress, the effect of magnetization of the fluid on drop elongation in the tube, the dependence of magnetic field strength and gradient on the current of the electromagnet for various points of the magnetic system gap, and the relation between the displacement of the magnetic fluid and the measurable force of the field stress. Experiments showed that the shape of the cylindrical column of magnetic fluid in the capillary tube depended substantially not only on the longitudinal uniform magnetic field stress but also on orientation of the column relative to the field. Fluid MMT-52 was used (magnetic phase-magnetite, stabilizer-oleic acid). One of the conditions necessary for its reliable operation was a convex shape of the magnetic fluid meniscus. It was found that transducer magnetic systems with a transverse field with respect to the sensing element were preferable since the magnetic fluid in the column retains its shape.

Bashtovoi, V.G.; Mikhalev, V.P.; Reks, A.G.

1988-01-01

226

Lamination and mixing in three fundamental flow sequences driven by electromagnetic body forces  

NASA Astrophysics Data System (ADS)

This article pursues the idea that the degree of striations, called lamination, could be engineered to complement stretching and to design new sequential mixers. It explores lamination and mixing in three new mixing sequences experimentally driven by electromagnetic body forces. To generate these three mixing sequences, Lorentz body forces are dynamically controlled to vary the flow geometry produced by a pair of local jets. The first two sequences are inspired from the tendril and whorl and blinking vortex flows. The third novel sequence is called the cat's eyes flip. These three mixing sequences exponentially stretch and laminate material lines representing the interface between two domains to be mixed. Moreover, the mixing coefficient (defined as 1-?2/?02 where ?2/?02 is the rescaled variance) and its rate grow exponentially before saturation. This saturation of the mixing process is related to the departure of the mixing rate from an exponential growth when the striations thicknesses reach the diffusive length scale of the measurements or species and dyes. Incidentally, in our experiments, for the same energy or forcing input, the cat's eyes flip sequence has higher lamination, stretching, and mixing rates than the tendril and whorl and the blinking vortex sequences. These features show that bakerlike in situ mixers can be conceived by dynamically controlling a pair of local jets and by integrating lamination during stirring stages with persistent geometries. Combined with novel insights provided by the quantification of the lamination, this paper should offer perspectives for the development of new sequential mixers, possibly on all scales.

Rossi, L.; Doorly, D.; Kustrin, D.

2012-08-01

227

A Magnetic Resonance Force Microscopy Quantum Computer with Tellurium Donors in Silicon  

E-print Network

We propose a magnetic resonance force microscopy (MRFM)-based nuclear spin quantum computer using tellurium impurities in silicon. This approach to quantum computing combines the well-developed silicon technology with expected advances in MRFM.

G. P. Berman; G. D. Doolen; V. I. Tsifrinovich

2000-03-18

228

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

PubMed

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. PMID:23720016

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

2013-07-01

229

Detection of silica-mediated dissolution of magnetic grains in sediments using FORC diagrams  

NASA Astrophysics Data System (ADS)

Recently silica-mediated dissolution has been recognized as a potentially important factor influencing magnetic studies of marine and lacustrine sediments. Although direct evidence for the dissolution of magnetic particles in silica-rich environments is lacking, the process is expected to produce changes in the magnetic grain-size distribution, a hypothesis that is tested in this study on sediments from Lake Tanganyika, East Africa, using First Order Reversal Curves (FORCs). Results from different magnetic intensity zones within the studied samples clearly show changes in the grain-size distribution of magnetic minerals. In particular, zones with high biogenic silica content (BSi) correlated with depletion in fine-grained magnetic material, whereas zones with lower BSi showed no depletion. These results are consistent with the idea that silica-mediated dissolution results in the preferential removal of fine-grained magnetic material, and indicate that FORC diagrams are effective in characterizing silica-mediated dissolution in sediments.

Wetter, Laura; Verosub, Ken; Russell, James

2007-06-01

230

The Development of the Separation Apparatus of Phosphor by Controlling the Magnetic Force  

NASA Astrophysics Data System (ADS)

The phosphor wastes contain the multiple kinds of rare-earth phosphors with high market value. Because of increasing demand for rare-earth, the technique to recover and reuse the rare-earth in the phosphor wastes is required. In this study, we focused on the difference of physical property such as magnetic susceptibility and density for each type of phosphor and tried to separate and recover the phosphors by using the magnetic separation technique utilizing the difference of the traction force to the magnet acting on the particles. Magneto-Archimedes method is method separation technique utilizi g the difference of magnetic susceptibility and density. We developed the magnetic separation apparatus by applying this technique. To develop the practical separation apparatus, the continuous process is required. Hence the fundamental experiment utilizing High Temperature Superconducting (HTS) Bulk Magnet which can generate the strong magnetic force was conducted. As a result, we succeeded the continuous separation of the phosphor wastes.

Wada, K.; Mishima, F.; Akiyama, Y.; Nishijima, S.

231

Comparison of seat belt force-limiting methods using the MADYMO multi-body/finite element program.  

PubMed

Belt force can be limited by a device in the belt retractor hardware or with force-limiting as an integral part of the webbing force/strain properties. In this research, MADYMO multi-body/finite element models of a 50th percentile Hybrid-3 male passenger in an airbag-equipped 4-door mid-size sedan were set up to compare occupant injury response under loading 1) from a baseline standard (non-force-limiting) belt system, 2) from a retractor-based force-limiting system, and 3) from a webbing-based force-limiting system. Chest acceleration was similar for the two force-limiting designs but the peak was approximately 10% greater for the standard belt. The magnitude of the head acceleration was similar for all three belts while the duration of these accelerations was much narrower for the force-limiting belts. Chest compression was similar for both force-limiting methods, and was about 60% less than the standard belt case. Compared to the baseline system and the retractor-based system, webbing-based force-limiting allowed greater pelvic excursion and a corresponding increase in femur force. It is concluded that webbing-based force limiting has some potential for reducing head and chest responses but these reductions must be evaluated with respect to other considerations such as submarining potential, non-frontal impact response, and future concepts like programmable force limiting. PMID:12214345

Sieveka, E M; Kent, R W; Crandall, J R

2001-01-01

232

Lift force acting on a cylindrical body in a fluid near the boundary of a cavity performing translational vibrations  

NASA Astrophysics Data System (ADS)

The averaged lift force acting on a cylindrical body near the boundary of a cavity with a fluid performing translational vibrations was studied. Experiments were performed with variation the viscosity of the fluid, the size and relative density of the body, and vibration parameters were varied. The lift force was measured by the method of dynamic suspension of a body in a gravitational field in the case where the body performed inertial vibrations without touching the walls. It was found that the vibrations generated a repulsion force which held the heavy body over the bottom of the cavity, and the light body at a certain distance from the top wall. It was shown that the effect of the repulsion forces manifested itself at a distance comparable to the thickness of the Stokes layer and increased with approach to the wall. A description of the mechanism of generation of the lift force is given. It is shown that in the case of high dimensionless frequencies, the experimental and theoretical results are in agreement.

Ivanova, A. A.; Kozlov, V. G.; Shchipitsyn, V. D.

2014-09-01

233

Body mass penalties in the physical fitness tests of the Army, Air Force, and Navy.  

PubMed

Recent research has empirically documented a consistent penalty against heavier service members for events identical or similar to those in the physical fitness tests of the Army, Air Force, and Navy. These penalties, which are not related to body fatness, are based on biological scaling models and have a physiological basis. Using hypothetical cases, we quantified the penalties for men, with body mass of 60 vs. 90 kg, and women, 45 vs. 75 kg, to be 15% to 20% for the fitness tests of these three services. Such penalties alone can adversely affect awards and promotions for heavier service members. To deal equitably with these penalties in a practical manner, we offer two recommendations, i.e., (1) implementation of revised fitness tests with balanced events, in which the penalties of one event for heavier service members are balanced by an equal and opposite bias against lighter service members, or (2) development of correction factors that can be multiplied by raw scores to yield adjusted scores free of body mass bias. PMID:16933817

Vanderburgh, Paul M; Crowder, Todd A

2006-08-01

234

Isotropic contact forces in arbitrary representation: Heterogeneous few-body problems and low dimensions  

NASA Astrophysics Data System (ADS)

The Bethe-Peierls asymptotic approach which models pairwise short-range forces by contact conditions is introduced in arbitrary representation for spatial dimensions less than or equal to 3. The formalism is applied in various situations and emphasis is put on the momentum representation. In the presence of a transverse harmonic confinement, dimensional reduction toward two-dimensional (2D) or one-dimensional (1D) physics is derived within this formalism. The energy theorem relating the mean energy of an interacting system to the asymptotic behavior of the one-particle density matrix illustrates the method in its second quantized form. Integral equations that encapsulate the Bethe-Peierls contact condition for few-body systems are derived. In three dimensions, for three-body systems supporting Efimov states, a nodal condition is introduced in order to obtain universal results from the Skorniakov-Ter-Martirosian equation and the Thomas collapse is avoided. Four-body bound state eigenequations are derived and the 2D '3+1' bosonic ground state is computed as a function of the mass ratio.

Pricoupenko, Ludovic

2011-06-01

235

Determination of constant alpha force-free solar magnetic fields from magnetograph data  

Microsoft Academic Search

It is shown that a magnetic field that is force-free with alpha constant (alpha is not equal to 0) in the whole volume outside the sun cannot have a finite energy content and that such a field cannot be determined uniquely from only one magnetic field component given at the photosphere. Therefore, the extension of a global scale constant-alpha force-free

N. Seehafer

1978-01-01

236

Spin-selective Imaging by Magnetic Exchange Force Microscopy Using Ferromagnetic Resonance.  

PubMed

Techniques to analyze the surface of magnetic memory devices with high spatial resolution are very important to develop today's information technology. The magnetic exchange force is an interaction between spins and is very important for analyzing magnetic properties. Magnetic exchange force microscopy (MExFM), which can detect the magnetic exchange force between the magnetic tip and the magnetic surface, has achieved the atomic-resolution imaging of the spin state on anti-ferromagnetic surface of NiO(001) [1]. In MExFM, however, the separation between a structure and a magnetic state on the surface has not been performed.Here, we propose a new MExFM using ferromagnetic resonance to separate the magnetic and non-magnetic tip-sample interaction. In this method, magnetic tip apex is irradiated by the frequency-modulated microwave with the frequency of ferromagnetic resonance. The magnetization of magnetic tip apex is modulated from on resonance to off resonance. Tip-sample interaction is measured with frequency modulation method. Magnetic images are obtained by detecting the modulation component of the frequency shift of the oscillating cantilever using a lock-in amplifier. Topographic images are obtained by the feedback signal for the constant tip-sample interaction. As a magnetic tip, magnetic cantilever tip coated with FePt with a high coercivity was used to detect the magnetic exchange force without an external magnetic field [2]. We performed imaging on antiferromagnetic material NiO(001) surface (Fig.1(a)) by MExFM using ferromagnetic resonance. We obtained spin selective image in atomic resolution (Fig.1(b)). This is the first demonstration of magnetization modulation of the magnetic tip apex using ferromagnetic resonance as well as the separation of the magnetic and non-magnetic tip-sample interaction in MExFM.jmicro;63/suppl_1/i11-a/DFU053F1F1DFU053F1Fig. 1.(a) Structure of NiO(001) surface and (b) its image (phase) obtained with MExFM using ferromagnetic resonance. (4 nm x 4 nm). PMID:25359800

Sugawara, Yasuhiro; Arima, Eiji; Naitoh, Yoshitaka; Li, Yan Jun

2014-11-01

237

Repulsive force generation due to topological effect of circulating magnetic fluids  

Microsoft Academic Search

The basic conception and technology for gravity control of spaceship are proposed. Gravitational repulsive force is generated due to the de Rham cohomology effect of four-dimensional angular momentum by means of the clockwise circulation flow of magnetic fluid where occurs the vast positive energy of magnons consisting of spin waves. Repulsive force generator is constructed by two toroidal tubes where

Hideo Hayasaka; Yoshinari Minami

1999-01-01

238

Urethral foreign body: removal of degraded magnetic spheres using Hartmann ear forceps.  

PubMed

Lower urinary tract foreign bodies have been reported in both children and adults. It is helpful for urologists to review foreign body case reports to become familiar with alternative approaches for removal that may prove helpful during challenging cases. To our knowledge, we describe for the first time a degraded rare-earth magnet within the body and use of Hartmann ear forceps to remove a foreign body from the urethra under cystoscopic guidance through a limited urethrotomy. PMID:25443938

Chung, Paul H; Traylor, Janelle; Baker, Linda A

2014-11-01

239

Noninvasive detection of unevenly magnetized permanent magnet of a brushless dc motor by characterizing back electromotive force  

NASA Astrophysics Data System (ADS)

Uneven magnetization of permanent magnets (PMs) is one of the major sources of unbalanced magnetic force and torque ripple, which excite a brushless dc (BLDC) motor. This paper investigates the frequency contents of the back electromotive force (BEMF) due to the unevenly magnetized PMs in a BLDC motor. The magnetic field of a BLDC motor is solved by using the finite element method, and the BEMF is calculated by differentiating the flux linkage with respect to time. The characteristics of BEMF are investigated by using the spectral analysis. Magnetic flux density of the ideally magnetized PMs has the harmonics of the pole-pair number, but unevenly magnetized PMs generate the additional harmonics. This research shows numerically and experimentally that the frequency components of the BEMF are determined by the least common multiple between the frequency contents of magnetic flux density from the PMs and the slot number per phase. It also shows that the magnetized status of the PMs of a BLDC can be noninvasively identified by monitoring the frequencies and the amplitudes of BEMF.

Lee, C. I.; Jang, G. H.

2009-04-01

240

Many-body Interactions in Magnetic Films and Nanostructures  

SciTech Connect

We describe results supported by DOE grant DE-FG02-04ER46158, which focused on magnetic interaction at surfaces, in thin films, and in metallic nanostructures. We report on three general topics: 1) The Rashba spin splitting at magnetic surfaces of rare earth metals, 2) magnetic nanowires self-assembled on stepped tungsten single crystals, and 3) magnetic interaction in graphene films doped with hydrogen atoms.

Stephen D. Kevan

2012-12-12

241

Magnetic force microscopy of epitaxial magnetite films through the Verwey transition  

Microsoft Academic Search

Magnetic force microscopy was performed on 300 nm thick magnetite films grown epitaxially on MgO (001) at temperatures ranging from well below to well above the Verwey transition temperature, TV. Frequency shift images were acquired at different locations on the sample as temperature was increased through the Verwey transition. The magnetic domain features are persistent at all temperatures, which indicates

A. K. H. Lee; P. B. Jayathilaka; C. A. Bauer; M. C. Monti; J. T. Markert; A. de Lozanne; Casey W. Miller

2010-01-01

242

Determination of constant ? force-free solar magnetic fields from magnetograph data  

Microsoft Academic Search

At first it is shown that a magnetic field being force-free, i.e. satisfying ? B = aB, with a = constant (a ? 0) in the whole exterior of the Sun cannot have a finite energy content and cannot be determined uniquely from only one magnetic field component given at the photosphere. Then the boundary value problem for a

N. Seehafer

1978-01-01

243

Magnetic-field-induced ferroelectric polarization reversal in magnetoelectric composites revealed by piezoresponse force microscopy.  

PubMed

Controlling electric polarization (or magnetization) in multiferroic materials with external magnetic fields (or electric fields) is very important for fundamental physics and spintronic devices. Although there has been some progress on magnetic-field-induced polarization reversal in single-phase multiferroics, such behavior has so far never been realized in composites. Here we show that it is possible to reverse ferroelectric polarization using magnetic fields in a bilayer Terfenol-D/PMN-33%PT composite. We realized this by ferroelectric domain imaging using piezoresponse force microscopy (PFM) under applied magnetic field loading. The internal electric field caused by the magnetoelectric (ME) effect in the PMN-PT crystal is considered as the driving force for the 180 polarization switching, and its existence is verified by switching spectroscopy PFM testing under a series of external magnetic fields. A quantitative method is further suggested to estimate the local ME coefficient based on the switching spectroscopy PFM testing results. PMID:24953042

Miao, Hongchen; Zhou, Xilong; Dong, Shuxiang; Luo, Haosu; Li, Faxin

2014-08-01

244

Magnetic force microscopy method and apparatus to detect and image currents in integrated circuits  

DOEpatents

A magnetic force microscopy method and improved magnetic tip for detecting and quantifying internal magnetic fields resulting from current of integrated circuits are disclosed. Detection of the current is used for failure analysis, design verification, and model validation. The interaction of the current on the integrated chip with a magnetic field can be detected using a cantilevered magnetic tip. Enhanced sensitivity for both ac and dc current and voltage detection is achieved with voltage by an ac coupling or a heterodyne technique. The techniques can be used to extract information from analog circuits. 17 figs.

Campbell, A.N.; Anderson, R.E.; Cole, E.I. Jr.

1995-11-07

245

Magnetic force microscopy method and apparatus to detect and image currents in integrated circuits  

DOEpatents

A magnetic force microscopy method and improved magnetic tip for detecting and quantifying internal magnetic fields resulting from current of integrated circuits. Detection of the current is used for failure analysis, design verification, and model validation. The interaction of the current on the integrated chip with a magnetic field can be detected using a cantilevered magnetic tip. Enhanced sensitivity for both ac and dc current and voltage detection is achieved with voltage by an ac coupling or a heterodyne technique. The techniques can be used to extract information from analog circuits.

Campbell, Ann. N. (13170-B Central SE #188, Albuquerque, NM 87123); Anderson, Richard E. (2800 Tennessee NE, Albuquerque, NM 87110); Cole, Jr., Edward I. (2116 White Cloud NE, Albuquerque, NM 87112)

1995-01-01

246

A discrete-forcing immersed boundary method for the fluid-structure interaction of an elastic slender body  

NASA Astrophysics Data System (ADS)

We present an immersed boundary (IB) method for the simulation of flow around an elastic slender body. The present method is based on the discrete-forcing IB method for a stationary, rigid body proposed by Kim, Kim and Choi (2001) [25]. The discrete-forcing approach is used to relieve the limitation on the computational time step size. The incompressible Navier-Stokes equations are implicitly coupled with the dynamic equation for an elastic slender body motion. The first is solved in the Eulerian coordinate and the latter is described in the Lagrangian coordinate. The elastic slender body is modeled as a thin and flexible solid and is segmented by finite number of thin blocks. Each block is moved by external and internal forces such as the hydrodynamic, elastic and buoyancy forces, where the hydrodynamic force is obtained directly from the discrete forcing used in the IB method. All the spatial derivative terms are discretized with the second-order central difference scheme. The present method is applied to three different fluid-structure interaction problems: flows around a flexible filament, a flapping flag in a free stream, and a flexible flapping wing in normal hovering, respectively. Computations are performed at maximum CFL numbers of 0.75-1. The results obtained agree very well with those from previous studies.

Lee, Injae; Choi, Haecheon

2015-01-01

247

Magnetic damping forces in figure-eight-shaped null-flux coil suspension systems  

SciTech Connect

This paper discusses magnetic damping forces in figure-eight-shaped null-flux coil suspension systems, focusing on the Holloman maglev rocket system. The paper also discusses simulating the damping plate, which is attached to the superconducting magnet by two short-circuited loop coils in the guideway. Closed-form formulas for the magnetic damping coefficient as functions of heave-and-sway displacements are derived by using a dynamic circuit model. These formulas are useful for dynamic stability studies.

He, Jianliang; Coffey, H.

1997-08-01

248

Magnetic damping forces in figure-eight-shaped null-flux coil suspension systems  

Microsoft Academic Search

This paper discusses magnetic damping forces in figure-eight-shaped null-flux coil suspension systems, focusing on the Holloman Maglev rocket system. The paper also discusses simulating the damping plate, which is attached to the superconducting magnet by two short-circuited loop coils interacting with the figure-eight-shaped null-flux coils in the guideway. Closed-form formulas for the magnetic damping coefficient as functions of heave-and-sway displacements

Jianliang He; H. Coffey

1997-01-01

249

Direct Measurements of the Penetration Depth in a Superconducting Film using Magnetic Force Microscopy  

SciTech Connect

We report the local measurements of the magnetic penetration depth in a superconducting Nb film using magnetic force microscopy (MFM). We developed a method for quantitative extraction of the penetration depth from single-parameter simultaneous fits to the lateral and height profiles of the MFM signal, and demonstrate that the obtained value is in excellent agreement with that obtained from the bulk magnetization measurements.

E Nazaretski; J Thibodaux; I Vekhter; L Civale; J Thompson; R Movshovich

2011-12-31

250

Magnetic Circuit Model of PM Motor-Generator to Predict Radial Forces  

NASA Technical Reports Server (NTRS)

A magnetic circuit model is developed for a PM motor for flywheel applications. A sample motor is designed and modeled. Motor configuration and selection of materials is discussed, and the choice of winding configuration is described. A magnetic circuit model is described, which includes the stator back iron, rotor yoke, permanent magnets, air gaps and the stator teeth. Iterative solution of this model yields flux linkages, back EMF, torque, power, and radial force at the rotor caused by eccentricity. Calculated radial forces are then used to determine motor negative stiffness.

McLallin, Kerry (Technical Monitor); Kascak, Peter E.; Dever, Timothy P.; Jansen, Ralph H.

2004-01-01

251

Enhanced quality factors and force sensitivity by attaching magnetic beads to cantilevers for atomic force microscopy in liquid  

E-print Network

Dynamic-mode atomic force microscopy (AFM) in liquid remains complicated due to the strong viscous damping of the cantilever resonance. Here we show that a high-quality resonance (Q>20) can be achieved in aqueous solution by attaching a microgram-bead at the end of the nanogram-cantilever. The resulting increase in cantilever mass causes the resonance frequency to drop significantly. However, the force sensitivity --- as expressed via the minimum detectable force gradient --- is hardly affected, because of the enhanced quality factor. Via the enhancement of the quality factor, the attached bead also reduces the relative importance of noise in the deflection detector. It can thus yield an improved signal-to-noise ratio when this detector noise is significant. We describe and analyze these effects for a set-up which includes magnetic actuation of the cantilevers and which can be easily implemented in any AFM system that is compatible with an inverted optical microscope.

Hoof, Sebastian; Hoogenboom, Bart W

2012-01-01

252

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

NASA Astrophysics Data System (ADS)

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

Minteer, Timothy M.

2015-01-01

253

Invincible DNA tethers: covalent DNA anchoring for enhanced temporal and force stability in magnetic tweezers experiments.  

PubMed

Magnetic tweezers are a powerful single-molecule technique that allows real-time quantitative investigation of biomolecular processes under applied force. High pulling forces exceeding tens of picoNewtons may be required, e.g. to probe the force range of proteins that actively transcribe or package the genome. Frequently, however, the application of such forces decreases the sample lifetime, hindering data acquisition. To provide experimentally viable sample lifetimes in the face of high pulling forces, we have designed a novel anchoring strategy for DNA in magnetic tweezers. Our approach, which exploits covalent functionalization based on heterobifunctional poly(ethylene glycol) crosslinkers, allows us to strongly tether DNA while simultaneously suppressing undesirable non-specific adhesion. A complete force and lifetime characterization of these covalently anchored DNA-tethers demonstrates that, compared to more commonly employed anchoring strategies, they withstand 3-fold higher pulling forces (up to 150 pN) and exhibit up to 200-fold higher lifetimes (exceeding 24 h at a constant force of 150 pN). This advance makes it possible to apply the full range of biologically relevant force scales to biomolecular processes, and its straightforward implementation should extend its reach to a multitude of applications in the field of single-molecule force spectroscopy. PMID:25140010

Janissen, Richard; Berghuis, Bojk A; Dulin, David; Wink, Max; van Laar, Theo; Dekker, Nynke H

2015-01-01

254

Electromagnetic Forces in a Hybrid Magnetic-Bearing Switched-Reluctance Motor  

NASA Technical Reports Server (NTRS)

Analysis and experimental measurement of the electromagnetic force loads on the hybrid rotor in a novel hybrid magnetic-bearing switched-reluctance motor (MBSRM) have been performed. A MBSRM has the combined characteristics of a switched-reluctance motor and a magnetic bearing. The MBSRM discussed in this report has an eight-pole stator and a six-pole hybrid rotor, which is composed of circular and scalloped lamination segments. The hybrid rotor is levitated using only one set of four stator poles, while a second set of four stator poles imparts torque to the scalloped portion of the rotor, which is driven in a traditional switched reluctance manner by a processor. Static torque and radial force analysis were done for rotor poles that were oriented to achieve maximum and minimum radial force loads on the rotor. The objective is to assess whether simple one-dimensional magnetic circuit analysis is sufficient for preliminary evaluation of this machine, which may exhibit strong three-dimensional electromagnetic field behavior. Two magnetic circuit geometries, approximating the complex topology of the magnetic fields in and around the hybrid rotor, were employed in formulating the electromagnetic radial force equations. Reasonable agreement between the experimental and the theoretical radial force loads predictions was obtained with typical magnetic bearing derating factors applied to the predictions.

Morrison, Carlos R.; Siebert, Mark W.; Ho, Eric J.

2008-01-01

255

An individual and dynamic Body Segment Inertial Parameter validation method using ground reaction forces.  

PubMed

Over the last decades a variety of research has been conducted with the goal to improve the Body Segment Inertial Parameters (BSIP) estimations but to our knowledge a real validation has never been completely successful, because no ground truth is available. The aim of this paper is to propose a validation method for a BSIP identification method (IM) and to confirm the results by comparing them with recalculated contact forces using inverse dynamics to those obtained by a force plate. Furthermore, the results are compared with the recently proposed estimation method by Dumas et al. (2007). Additionally, the results are cross validated with a high velocity overarm throwing movement. Throughout conditions higher correlations, smaller metrics and smaller RMSE can be found for the proposed BSIP estimation (IM) which shows its advantage compared to recently proposed methods as of Dumas et al. (2007). The purpose of the paper is to validate an already proposed method and to show that this method can be of significant advantage compared to conventional methods. PMID:24704168

Hansen, Clint; Venture, Gentiane; Rezzoug, Nasser; Gorce, Philippe; Isableu, Brice

2014-05-01

256

Magnetic Force Microscopy Imaging of Current Paths R. Yongsunthon1  

E-print Network

the entire tip pyramid (of about 8µm height and 8µm base) resulting in a large magnetic volume but limited-carrying devices, which are subject to the difficulties discussed above, as well as generating heat due to power

Williams, Ellen D.

257

Dynamics of a Levitron under a periodic magnetic forcing  

NASA Astrophysics Data System (ADS)

The Levitron is a toy that consists of a spinning top that levitates over a magnetic base for a few minutes, until air drag decreases the spin rate below a certain limit. Stable levitation, lasting hours or even days, has been achieved for Levitrons that were externally driven by either an air jet or an alternating magnetic field. We report measurements of stable levitation for the latter case. We show that the top precession couples with the frequency of the alternating field, so that the precession period equals the period of the field. In addition, the top rotates around itself with the same period. We present numerical simulations that reproduce the essential features of this dynamics. It is also shown that the magnetic torque that drives the top is due to a misalignment between the magnetic dipole moment and the mechanical axis of the top.

Prez, Alberto T.; Garca-Snchez, Pablo

2015-02-01

258

The Inverse-Cube Law of Magnetic Forces  

NSDL National Science Digital Library

This is an activity about the magnetic deflection. Learners will observe and measure the deflection that an iron mass causes in a soda bottle magnetometer and plot the data. The data should show the inverse-square cube law of change in the magnetic field. This is the twelfth activity in the guide and requires prior use and construction of a soda bottle magnetometer, as well as a six to ten pound container of iron nails (or an equivalent iron mass).

259

Influence of stator slots on the development of noise-generating magnetic force waves  

NASA Astrophysics Data System (ADS)

The calculation of noise in electrical machines is important in the design of these machines. It is shown that the magnetic anisotropy of a laminated stator core caused by stator slots has a substantial effect on the force waves acting on the yoke. The force waves are described simply using a modulation function and the Fourier coefficients of the waves. The effects of the amplitude of the magnetic force waves are discussed, and the effectiveness of stator slot skewing is determined. It is shown that subharmonics can be generated by the slotting (affecting the harmonic number of the force waves), and that for specific harmonic numbers, a reversal in the direction of rotation of force waves takes place. The effectiveness of the method is substantiated by a practical example.

Wachta, B.

260

Tensile Force-Dependent Neurite Elicitation via Anti-?1 Integrin Antibody-Coated Magnetic Beads  

PubMed Central

Previous work using glass microneedles to apply calibrated, localized force to neurons showed that tensile force is a sufficient signal for neurite initiation and elongation. However, previous studies did not examine the kinetics or probability of neurite initiation as a function of force or the rate of force application. Here we report the use of a new techniquemagnetic bead force applicationto systematically investigate the role of force in these phenomena with better ease of use and control over force than glass microneedles. Force-induced neurite initiation from embryonic chick forebrain neurons appeared to be a first-order random process whose rate increased with increasing force, and required the presence of peripheral microtubules. In addition, the probability of initiation was more than twofold lower for neurons exposed to rapid initial force ramps (450 pN/s) than for neurons exposed to slower ramps (1.5 and 11 pN/s). We observed a low force threshold for elongation (15100 pN), which was not previously detected in chick forebrain neurites elongated by glass microneedles. Finally, neurites subjected to constant force elongated at variable instantaneous rates, and switched abruptly between elongation and retraction, similar to spontaneous, growth-cone-mediated outgrowth and microtubule dynamic instability. PMID:12829516

Fass, Joseph N.; Odde, David J.

2003-01-01

261

Prediction of ocean-induced magnetic signals in the satellite observations due to tidal forcing  

NASA Astrophysics Data System (ADS)

An increase in accuracy of the Earth's magnetic field observations by the future SWARM satellite mission strengths the interest of dealing with magnetic signals of small amplitudes but a global support. An example of such a signal is the magnetic field variation induced by global ocean dynamics. Since sea-water is a good electrical conductor, the ocean currents represent electrical currents moving in the main magnetic field. According to the Faraday's law, they induce a secondary magnetic field that is, in principle, observable by ground and satellite observations. Although they are of small amplitudes, they have recently been identified for ocean currents forced by the tidal wave M2. The identification of small magnetic components in the total magnetic signal can be helpt by their numerical prediction. The 2-D theory for computing the magnetic field generated by ocean currents that has been proposed by Tyler et al. (1997) is combined with the ocean tidal flows simulated by the numerical ocean model for circulation and tides (OMCT; Thomas 2002) and used to calculate secondary magnetic field generated by lunar-solar tidal potential for individual tidal waves. Unlike to some recent studies where the ocean currents have been deduced from altimetry data by applying the geostrophic method, the ocean flows calculated by the OMCT approach are forced directly by the lunisolar tidal potential that is deduced from analytical ephemerides. As a result, the method provides the radial component of the ocean-induced magnetic signal at the sea surface and satellite altitude. A comparison with published results by Tyler et al. (2003) and Maus et al. (2004) shows a good agreement in terms of global spatial pattern and magnitude, though some minor differences occur. This new method simplifies the calculation of ocean-induced magnetic fields and allows the prediction of the secondary magnetic fields induced by the complete lunisolar tidal forcing. This numerical approach can be used to estimate the opportunities in detecting ocean-induced magnetic signals in satellite observations.

Dostal, J.; Dobslaw, H.; Thomas, M.

2009-04-01

262

Approximating edges of source bodies from magnetic or gravity anomalies.  

USGS Publications Warehouse

Cordell and Grauch (1982, 1985) discussed a technique to estimate the location of abrupt lateral changes in magnetization or mass density of upper crustal rocks. The final step of their procedure is to identify maxima on a contoured map of horizontal gradient magnitudes. Attempts to automate their final step. The method begins with gridded magnetic or gravity anomaly data and produces a plan view of inferred boundaries of magnetic or gravity sources. The method applies to both local surveys and to continent-wide compilations of magnetic and gravity data.-from Authors

Blakely, R.J.; Simpson, R.W.

1986-01-01

263

Drag measurements on a laminar flow body of revolution in Langley's 13 inch magnetic suspension and balance system. M.S. Thesis  

NASA Technical Reports Server (NTRS)

Low-speed wind tunnel drag force measurements were taken on a laminar flow body of revolution free of support interference. This body was tested at zero incidence in the NASA Langley 13 inch Magnetic Suspension and Balance System (MSBS). The primary objective of these tests was to substantiate the drag force measuring capabilities of the 13 inch MSBS. A secondary objective was to obtain support interference free drag measurements on an axisymmetric body of interest. Both objectives were met. The drag force calibrations and wind-on repeatability data provide a means of assessing the drag force measuring capabilities of the 13 inch MSBS. The measured drag coefficients for this body are of interest to researchers actively involved in designing minimum drag fuselage shapes. Additional investigations included: the effects of fixing transition; the effects of fins installed in the tail; surface flow visualizations using both liquid crystals and oil flow; and base pressure measurements using a one-channel telemetry system. Two drag prediction codes were used to assess their usefulness in estimating overall body drag. These theoretical results did not compare well with the measured values because of the following: incorrect or non-existent modeling of a laminar separation bubble on the body and incorrect of non-existent estimates of base pressure drag.

Dress, David A.

1988-01-01

264

Received 30 Oct 2013 | Accepted 27 Jun 2014 | Published 22 Aug 2014 Magnetic force microscopy reveals meta-stable  

E-print Network

ARTICLE Received 30 Oct 2013 | Accepted 27 Jun 2014 | Published 22 Aug 2014 Magnetic force microscopy reveals meta-stable magnetic domain states that prevent reliable absolute palaeointensity to produce truthful estimates. Magnetic force microscope images were taken before and after a heating step

Utrecht, Universiteit

265

Multiple degree-of-freedom force and moment measurement for static propulsion testing using magnetic suspension technology  

Microsoft Academic Search

Innovative Information Systems (IIS), Inc. is in the process of designing and fabricating a high bandwidth force and moment measuring device (i.e. the Magnetic Thruster Test Stand). This device will use active magnetic suspension to allow direct measurements of the forces and torques generated by the rocket engines of the missile under test. The principle of operation of the Magnetic

Keith Stuart; Blake Bartosh

1993-01-01

266

FORCE-FREENESS OF SOLAR MAGNETIC FIELDS IN THE PHOTOSPHERE Q1 Y.-J. Moon,1,2  

E-print Network

FORCE-FREENESS OF SOLAR MAGNETIC FIELDS IN THE PHOTOSPHERE Q1 Y.-J. Moon,1,2 G. S. Choe,3 H. S. Yun It is widely believed that solar magnetic fields are force-free in the solar corona but not in the solar photo: photosphere 1. INTRODUCTION It is generally believed that magnetic fields play a central role in solar

267

Magnetic Field, Force, and Inductance Computations for an Axially Symmetric Solenoid  

NASA Technical Reports Server (NTRS)

The pumping of liquid oxygen (LOX) by magnetic fields (B field), using an array of electromagnets, is a current topic of research and development at Kennedy Space Center, FL. Oxygen is paramagnetic so that LOX, like a ferrofluid, can be forced in the direction of a B field gradient. It is well known that liquid oxygen has a sufficient magnetic susceptibility that a strong magnetic gradient can lift it in the earth's gravitational field. It has been proposed that this phenomenon can be utilized in transporting (i.e., pumping) LOX not only on earth, but on Mars and in the weightlessness of space. In order to design and evaluate such a magnetic pumping system, it is essential to compute the magnetic and force fields, as well as inductance, of various types of electromagnets (solenoids). In this application, it is assumed that the solenoids are air wrapped, and that the current is essentially time independent.

Lane, John E.; Youngquist, Robert C.; Immer, Christopher D.; Simpson, James C.

2001-01-01

268

The Effect of Field Representation on Student Responses to Magnetic Force Questions  

NASA Astrophysics Data System (ADS)

We examine student understanding of the magnetic force exerted on a charged particle and report three findings from a series of tests administered to introductory physics students. First, we expand on previous findings that many students believe in "charged" magnetic poles and find that although students may answer according to a model where a positive charge is attracted to a south pole and repulsed by a north, these students may not believe that the poles are charged. Additional models produce identical answer schemes, the primary being magnetic force parallel to magnetic field. Second, the representation format affects responses: students answer differently when the magnetic field is portrayed by a field source vs. by field lines. Third, after traditional instruction improvement in student performance is greater on questions portraying field lines than for questions portraying field sources.

Scaife, Thomas M.; Heckler, Andrew F.

2007-11-01

269

Magnetic energy dissipation in force-free jets  

NASA Technical Reports Server (NTRS)

It is shown that a magnetic pressure-dominated, supersonic jet which expands or contracts in response to variations in the confining external pressure can dissipate magnetic energy through field-line reconnection as it relaxes to a minimum-energy configuration. In order for a continuous dissipation to occur, the effective reconnection time must be a fraction of the expansion time. The dissipation rate for the axisymmetric minimum-energy field configuration is analytically derived. The results indicate that the field relaxation process could be a viable mechanism for powering the synchrotron emission in extragalactic jets if the reconnection time is substantially shorter than the nominal resistive tearing time in the jet.

Choudhuri, Arnab Rai; Konigl, Arieh

1986-01-01

270

Structural responses of cells to intracellular magnetic force induced by superparamagnetic iron oxide nanoparticles  

PubMed Central

In this paper, we study the effects of intracellular force on human umbilical vein endothelial cells. We generated intracellular force on endothelial cells under different magnetic fields using the cell uptake of superparamagnetic iron oxide nanoparticles. Cell responses to intracellular force were observed using fluorescent microscopy. Our results indicated that nanoparticles were taken up by the cell by endocytosis and were deposited in lysosomes. Nanoparticles and lysosomes inside the cell could be relocated by the application of a magnetic force. The intracellular magnetic force could also be used to accelerate cell migration by adjusting the magnetic fields and giving the cell free culture space. No cytotoxicity of nanoparticles was found in our experiments. By comparing intracellular relocalization with migration of the whole cell, we obtained a better understanding of the self-defence mechanisms of cells based on their mechanical properties. Based on the promising mechanical properties and low cytotoxicity of our magnetic nanoparticles, their potential applications in cytomechanics and cell patterning are discussed. PMID:24336693

Shen, Han; Tong, Sheng; Bao, Gang; Wang, Biao

2014-01-01

271

Long-lived magnetism from solidification-driven convection on the pallasite parent body  

NASA Astrophysics Data System (ADS)

Palaeomagnetic measurements of meteorites suggest that, shortly after the birth of the Solar System, the molten metallic cores of many small planetary bodies convected vigorously and were capable of generating magnetic fields. Convection on these bodies is currently thought to have been thermally driven, implying that magnetic activity would have been short-lived. Here we report a time-series palaeomagnetic record derived from nanomagnetic imaging of the Imilac and Esquel pallasite meteorites, a group of meteorites consisting of centimetre-sized metallic and silicate phases. We find a history of long-lived magnetic activity on the pallasite parent body, capturing the decay and eventual shutdown of the magnetic field as core solidification completed. We demonstrate that magnetic activity driven by progressive solidification of an inner core is consistent with our measured magnetic field characteristics and cooling rates. Solidification-driven convection was probably common among small body cores, and, in contrast to thermally driven convection, will have led to a relatively late (hundreds of millions of years after accretion), long-lasting, intense and widespread epoch of magnetic activity among these bodies in the early Solar System.

Bryson, James F. J.; Nichols, Claire I. O.; Herrero-Albillos, Julia; Kronast, Florian; Kasama, Takeshi; Alimadadi, Hossein; van der Laan, Gerrit; Nimmo, Francis; Harrison, Richard J.

2015-01-01

272

Long-lived magnetism from solidification-driven convection on the pallasite parent body.  

PubMed

Palaeomagnetic measurements of meteorites suggest that, shortly after the birth of the Solar System, the molten metallic cores of many small planetary bodies convected vigorously and were capable of generating magnetic fields. Convection on these bodies is currently thought to have been thermally driven, implying that magnetic activity would have been short-lived. Here we report a time-series palaeomagnetic record derived from nanomagnetic imaging of the Imilac and Esquel pallasite meteorites, a group of meteorites consisting of centimetre-sized metallic and silicate phases. We find a history of long-lived magnetic activity on the pallasite parent body, capturing the decay and eventual shutdown of the magnetic field as core solidification completed. We demonstrate that magnetic activity driven by progressive solidification of an inner core is consistent with our measured magnetic field characteristics and cooling rates. Solidification-driven convection was probably common among small body cores, and, in contrast to thermally driven convection, will have led to a relatively late (hundreds of millions of years after accretion), long-lasting, intense and widespread epoch of magnetic activity among these bodies in the early Solar System. PMID:25612050

Bryson, James F J; Nichols, Claire I O; Herrero-Albillos, Julia; Kronast, Florian; Kasama, Takeshi; Alimadadi, Hossein; van der Laan, Gerrit; Nimmo, Francis; Harrison, Richard J

2015-01-22

273

Quantitative magnetic force microscopy on permalloy dots using an iron filled carbon nanotube probe.  

PubMed

An iron filled carbon nanotube (FeCNT), a 10-40 nm ferromagnetic nanowire enclosed in a protective carbon tube, is an attractive candidate for a magnetic force microscopy (MFM) probe as it provides a mechanically and chemically robust, nanoscale probe. We demonstrate the probe's capabilities with images of the magnetic field gradients close to the surface of a Py dot in both the multi-domain and vortex states. We show the FeCNT probe is accurately described by a single magnetic monopole located at its tip. Its effective magnetic charge is determined by the diameter of the iron wire and its saturation magnetization 4?M(s) ? 2.2 10(4)G. A magnetic monopole probe is advantageous as it enables quantitative measurements of the magnetic field gradient close to the sample surface. The lateral resolution is defined by the diameter of the iron wire and the probe-sample separation. PMID:21864777

Wolny, F; Obukhov, Y; Mhl, T; Weissker, U; Philippi, S; Leonhardt, A; Banerjee, P; Reed, A; Xiang, G; Adur, R; Lee, I; Hauser, A J; Yang, F Y; Pelekhov, D V; Bchner, B; Hammel, P C

2011-07-01

274

Thin-foil magnetic force system for high-numerical-aperture microscopy  

PubMed Central

Forces play a key role in a wide range of biological phenomena from single-protein conformational dynamics to transcription and cell division, to name a few. The majority of existing microbiological force application methods can be divided into two categories: those that can apply relatively high forces through the use of a physical connection to a probe and those that apply smaller forces with a detached probe. Existing magnetic manipulators utilizing high fields and high field gradients have been able to reduce this gap in maximum applicable force, but the size of such devices has limited their use in applications where high force and high-numerical-aperture (NA) microscopy must be combined. We have developed a magnetic manipulation system that is capable of applying forces in excess of 700 pN on a 1 ?m paramagnetic particle and 13 nN on a 4.5 ?m paramagnetic particle, forces over the full 4? sr, and a bandwidth in excess of 3 kHz while remaining compatible with a commercially available high-NA microscope objective. Our system design separates the pole tips from the flux coils so that the magnetic-field geometry at the sample is determined by removable thin-foil pole plates, allowing easy change from experiment to experiment. In addition, we have combined the magnetic manipulator with a feedback-enhanced, high-resolution (2.4 nm), high-bandwidth (10 kHz), long-range (100 ?m xyz range) laser tracking system. We demonstrate the usefulness of this system in a study of the role of forces in higher-order chromosome structure and function. PMID:16858495

Fisher, J. K.; Cribb, J.; Desai, K. V.; Vicci, L.; Wilde, B.; Keller, K.; Taylor, R. M.; Haase, J.; Bloom, K.; O'Brien, E. Timothy; Superfine, R.

2006-01-01

275

qPlus Magnetic Force Microscopy in Frequency-Modulation Mode with milli-Hertz Resolution  

E-print Network

Magnetic force microscopy (MFM) allows one to image the domain structure of ferromagnetic samples by probing the dipole forces between a magnetic probe tip and a magnetic sample. The magnetic domain structure of the sample depends on the atomic arrangement of individual electron spins. It is desirable to be able to image both individual atoms and domain structures with a single probe. However, the force gradients of the interactions responsible for atomic contrast and those causing domain contrast are orders of magnitude apart - ranging from up to 100N/m for atomic interactions down to 0.0001N/m for magnetic dipole interactions. Here, we show that this gap can be bridged with a qPlus sensor, with a stiffness of 1800N/m (optimized for atomic interaction), that is sensitive enough to measure milli-Hertz frequency contrast caused by magnetic dipole-dipole interactions. Thus we have succeeded to establish a sensing technique that performs Scanning Tunneling Microscopy, Atomic Force Microscopy and MFM with a singl...

Schneiderbauer, M

2011-01-01

276

Magnetic Tweezers: Micromanipulation and Force Measurement at the Molecular Level  

Microsoft Academic Search

Cantilevers and optical tweezers are widely used for micromanipulating cells or biomolecules for measuring their mechanical properties. However, they do not allow easy rotary motion and can sometimes damage the handled material. We present here a system of magnetic tweezers that overcomes those drawbacks while retaining most of the previous dynamometers properties. Electromagnets are coupled to a microscope-based particle tracking

Charlie Gosse; Vincent Croquette

2002-01-01

277

Modified approach to single-spin detection using magnetic resonance force microscopy  

SciTech Connect

The magnetic moment of a single spin interacting with a cantilever in magnetic resonance force microscopy (MRFM) experiences quantum jumps in orientation rather than smooth oscillations. These jumps cannot be detected by a conventional MRFM based on observation of driven resonant oscillations of a cantilever. In this paper, we propose a method which should allow detection of the magnetic signal from a single spin using a modification of a conventional MRFM. We estimate the opportunity to detect the magnetic signal from a single proton. (c) 2000 The American Physical Society.

Berman, Gennady P. [Theoretical Division, T-13, MS B213, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Theoretical Division, T-13, MS B213, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Tsifrinovich, Vladimir I. [IDS Department, Polytechnic University, Six Metrotech Center, Brooklyn, New York 11201 (United States)] [IDS Department, Polytechnic University, Six Metrotech Center, Brooklyn, New York 11201 (United States)

2000-02-01

278

Detection of secondary phases in duplex stainless steel by magnetic force microscopy and scanning Kelvin probe force microscopy  

SciTech Connect

The secondary phase transformations in a commercial super duplex stainless steel were investigated by micro-chemical analyses and high resolution scanning probe microscopy. Energy dispersive X-ray and electron probe detected ferrite and austenite as well as secondary phases in unetched aged duplex stainless steel type 25Cr-7Ni-3Mo. Volta potential indicated that nitride and sigma appeared more active than ferrite, while secondary austenite and austenite presented a nobler potential. Reversal order in nobility is thought to be attributable to the potential ranking provided by oxide nature diversity as a result of secondary phase surface compositions on steel. After eutectoid transformation, secondary austenite was detected by electron probe microanalysis, whereas atomic force microscopy distinguished this phase from former austenite by image contrast. Magnetic force microscopy revealed a ghosted effect on the latter microstructure probably derived from metal memory reminiscence of mechanical polishing at passivity and long range magnetic forces of ferrite phase. - Highlights: Nobility detection of secondary phases by SKPFM in DSS particles is not a straightforward procedure. As Volta potential and contrast are not always consistent SKPFM surface oxides is thought played an important role in detection. AFM distinguished secondary austenite from former austenite by image contrast though SEM required EPMA.

Ramrez-Salgado, J. [Instituto Mexicano del Petrleo, Direccin de Investigacin y Posgrado, Eje Central Norte Lzaro Crdenas, No. 152, 07730 D.F., Mxico (Mexico); Domnguez-Aguilar, M.A., E-mail: madoming@imp.mx [Instituto Mexicano del Petrleo, Direccin de Investigacin y Posgrado, Eje Central Norte Lzaro Crdenas, No. 152, 07730 D.F., Mxico (Mexico); Castro-Domnguez, B. [University of Tokyo, Department of Chemical System Engineering, Faculty of Engineering Bldg. 5, 7F 722, 7-3-1 Hongo, Bunkyo-ku, Tokyo 1138656 (Japan); Hernndez-Hernndez, P. [Instituto Mexicano del Petrleo, Direccin de Investigacin y Posgrado, Eje Central Norte Lzaro Crdenas, No. 152, 07730 D.F., Mxico (Mexico); Newman, R.C. [University of Toronto, Department of Chemical Engineering and Applied Chemistry, 200 College Street, Toronto M5S 3E5 (Canada)

2013-12-15

279

Detection of Silica-Mediated Dissolution of Magnetic Grains in Sediments Using FORC Diagrams  

NASA Astrophysics Data System (ADS)

Recently silica-mediated dissolution has been recognized as a potentially important factor in magnetic studies of marine and lacustrine sediments. Although direct evidence for the dissolution of magnetic particles in silica-rich environments is still lacking, the process is expected to produce changes in the magnetic grain-size distribution. This hypothesis can be tested using FORC diagrams, which provide detailed information about the magnetic grain-size distributions of small quantities of material. For the present study, four cores were investigated from Lake Tanganyika in East Africa, where high levels of dissolved silica are present. Large variations in both natural and artificial remanent magnetization intensities were observed during the initial paleomagnetic investigation of the cores. These variations in magnetic intensity could not be explained by simple dilution by inert silica in the sediment, suggesting that silica-mediated dissolution might be involved. To study this phenomenon, FORC diagrams were collected from zones of both high and low magnetic intensity. Results from the different zones clearly show that changes in the magnetic intensity are associated with changes in the magnetic grain-size distribution. In particular, zones with high silica content correlated with a depletion in fine-grained magnetic material, whereas zones with lower silica content showed no depletion. These results are consistent with the idea that silica-mediated dissolution results in the preferential removal of fine-grained magnetic material. The results of this study suggest that FORC diagrams are an effective way of determining the presence of silica-mediated dissolution in sediments.

Wetter, L.; Verosub, K.; Acton, G.; Russell, J.

2005-12-01

280

Atomic-scale friction measurements using friction force microscopy. Part 2: Application to magnetic media  

NASA Astrophysics Data System (ADS)

Atomic Force/Friction Force Microscopes (AFM/FFM) were used to study tribological properties of metal-particle tapes with two roughnesses, Co gamma Fe2O3 tapes (unwiped and wiped), and unlubricated and lubricated thin-film magnetic rigid disks (as-polished and standard textured). Nanoindentation studies showed that the hardness of the tapes through the magnetic coating is not uniform. These results are consistent with the fact that the tape surface is a composite and is not homogeneous. Nanoscratch experiments performed on magnetic tapes using silicon nitride tips revealed that deformation and displacement of tape surface material occurred after one pass under light loads. A comparison between friction force profiles and the corresponding surface roughness profiles of all samples tested shows a poor correlation between localized values of friction and surface roughness.

Bhushan, Bharat; Ruan, Ju-Ai

1993-10-01

281

Nanoscale Investigation of Au Islands-Ni Film Interactions by Magnetic-Force-Controlled Atomic Force Microscopy  

NASA Astrophysics Data System (ADS)

The study of metal-metal interactions is both interesting and of technological importance for various thin-film structures. We carried out surface elemental analysis of several metal-plated films using magnetic-force-controlled atomic force microscopy (MFC-AFM) to evaluate the quality of wireless bondings and the films themselves. We reached the following two conclusions. First, the stiffness of the two types of plated metal film can be differentiated by MFC-AFM, whereby the difference in stiffness between the plated metal films can be imaged. Simultaneous imaging of the surface properties and stiffness of the samples produced by wet processes can be achieved at high resolution. Secondly, the Ni atoms that diffused to the Au-plated film surface annealed at 180 C for 5 min can also be imaged by MFC-AFM. The relationship of these metal-metal interactions to the electronic packaging are discussed in this paper.

Yamamoto, Shin-ichi; Yamada, Hirofumi

2009-08-01

282

An investigation of three-body effects in intermolecular forces. III. Far infrared laser vibration-rotation-tunneling spectroscopy  

E-print Network

An investigation of three-body effects in intermolecular forces. III. Far infrared laser vibration.2 cm-`, com- pleting the high resolution far infrared measurements of the three lowest-lying Ar by high resolution microwave," far in- frared, l2 and near infraredi spectroscopy. In particular

Cohen, Ronald C.

283

Effects of Rigid Body Collisions and Tide-Forced Drift on Large Tabular Icebergs of the Antarctic  

E-print Network

1 Effects of Rigid Body Collisions and Tide-Forced Drift on Large Tabular Icebergs of the Antarctic ICEBERGS #12;2 Abstract. Following the calving of an iceberg from an ice shelf, many collisions between the new iceberg and the remaining shelf can occur as the iceberg responds to time-varying oceanic

Macayeal, Douglas R.

284

Characteristics and computer model simulation of magnetic damping forces in maglev systems  

SciTech Connect

This report discusses the magnetic damping force in electrodynamic suspension (EDS) maglev systems. The computer model simulations, which combine electrical system equations with mechanical motion equations on the basis of dynamic circuit theory, were conducted for a loop-shaped coil guideway. The intrinsic damping characteristics of the EDS-type guideway are investigated, and the negative damping phenomenon is confirmed by the computer simulations. The report also presents a simple circuit model to aid in understanding damping-force characteristics.

He, J.L.; Rote, D.M.; Chen, S.S.

1994-05-01

285

Estimation of the total magnetization direction of approximately spherical bodies  

NASA Astrophysics Data System (ADS)

We have developed a fast total-field anomaly inversion to estimate the magnetization direction of multiple sources with approximately spherical shape and known centres. Our method can be applied to interpret multiple sources with different magnetization directions. It neither requires the prior computation of any transformation like reduction to the pole nor the use of regularly spaced data on a horizontal grid. The method contains flexibility to be implemented as a linear or non-linear inverse problem, which results, respectively, in a least-squares or robust estimate of the components of the magnetization vector of the sources. Applications to synthetic data show the robustness of our method against interfering anomalies and errors in the location of the sources' centre. Besides, we show the feasibility of applying the upward continuation to interpret non-spherical sources. Applications to field data over the Gois Alkaline Province (GAP), Brazil, show the good performance of our method in estimating geological meaningful magnetization directions. The results obtained for a region of the GAP, near from the alkaline complex of Diorama, suggest the presence of non-outcropping sources marked by strong remanent magnetization with inclination and declination close to -70.35 and -19.81, respectively. This estimated magnetization direction leads to predominantly positive reduced-to-the-pole anomalies, even for other region of the GAP, in the alkaline complex of Montes Claros de Gois. These results show that the non-outcropping sources near from the alkaline complex of Diorama have almost the same magnetization direction of that ones in the alkaline complex of Montes Claros de Gois, strongly suggesting that these sources have emplaced the crust almost within the same geological time interval.

Oliveira, V. C., Jr.; Sales, D. P.; Barbosa, V. C. F.; Uieda, L.

2014-09-01

286

Evolution of Magnetic Field in AR 5747 and Its Approximation as a Linear Force Free Field  

E-print Network

The evolution of nonpotential characteristics of magnetic fields in AR 5747 is presented using Mees Solar Observatory magnetograms taken on Oct. 20, 1989 to Oct. 22, 1989. The active region showed such violent flaring activities during the observational span that strong X-ray flares took place including a 2B/X3 flare. The magnetogram data were obtained by the Haleakala Stokes Polarimeter which provides simultaneous Stokes profiles of the Fe I doublet 6301.5 and 6302.5. A nonlinear least square method was adopted to derive the magnetic field vectors from the observed Stokes profiles and a multi-step ambiguity solution method was employed to resolve the 180 degree ambiguity. From the ambiguity-resolved vector magnetograms, we have derived a set of physical quantities characterizing the field configuration, which are magnetic flux, vertical current density, magnetic shear angle, angular shear, magnetic free energy density and a measure of magnetic field discontinuity MAD (Maximum Angular Difference between two adjacent field vectors). In our results, all the physical parameters decreased with time, which implies that the active region was in a relaxation stage of its evolution. To examine the force-free characteristics of the field, we calculated the integrated Lorentz force and and also compared the longitudinal field component with the corresponding vertical current density. In this investigation, we found that the magnetic field in this active region was approximately linearly force-free throughout the observing period. The time variation of the linear force-free coefficient is consistent with the evolutionary trend of other nonpotentiality parameters. This suggests that the linear force-free coefficient could be a good indicator of the evolutionary status of active regions.

Y. -J. Moon; H. S. Yun; G. S. Choe; Y. D. Park; D. L. Mickey

1999-10-05

287

Domain-wall structure in thin films with perpendicular anisotropy: Magnetic force microscopy and polarized neutron reflectometry study  

E-print Network

Ferromagnetic domain patterns and three-dimensional domain-wall configurations in thin CoCrPt films with perpendicular magnetic anisotropy were studied in detail by combining magnetic force microscopy and polarized neutron ...

Navas, David

288

Height, weight and body mass index (BMI) in psychiatrically ill US Armed Forces personnel  

PubMed Central

Background In both psychiatrically ill and psychiatrically healthy adults, the connection between health and individuals height and weight has long been examined. Specifically, research on the idea that individuals with certain body types were prone to particular psychiatric diseases has been explored sporadically for centuries. The hypothesis that psychiatrically ill individuals were shorter and weighed less than psychiatrically healthy counterparts would correspond with the neurodevelopmental model of psychiatric disease. Method To evaluate possible links between psychiatric illness and physique, the height, weight and BMI of 7514 patients and 85 940 controls were compared. All subjects were part of the National Collaborative Study of Early Psychosis and Suicide (NCSEPS). Patients were US military active duty personnel hospitalized for either bipolar disorder, major depressive disorder, or schizophrenia and controls were psychiatrically-healthy US military active duty personnel matched for date of entry into the service. Results No consistent differences in height, weight or BMI were found between patients and controls, or between patient groups. Some weak ANOVA differences were found between age at the time of entering active duty and weight, as well as BMI, but not height. Conclusions Unlike most previous studies that have looked at the links between height and psychiatric illness, this study of the NCSEPS cohort found that, at entry into the US Armed Forces, there were no consistent decreases in height for patients with bipolar disorder, major depressive disorder or schizophrenia compared with a large control group. Furthermore, there were no consistent differences for weight or BMI. PMID:12622316

WYATT, R. J.; HENTER, I. D.; MOJTABAI, R.; BARTKO, J. J.

2015-01-01

289

Navier-Stokes Computations of Longitudinal Forces and Moments for a Blended Wing Body  

NASA Technical Reports Server (NTRS)

The object of this paper is to investigate the feasibility of applying CFD methods to aerodynamic analyses for aircraft stability and control. The integrated aerodynamic parameters used in stability and control, however, are not necessarily those extensively validated in the state of the art CFD technology. Hence, an exploratory study of such applications and the comparison of the solutions to available experimental data will help to assess the validity of the current computation methods. In addition, this study will also examine issues related to wind tunnel measurements such as measurement uncertainty and support interference effects. Several sets of experimental data from the NASA Langley 14x22-Foot Subsonic Tunnel and the National Transonic Facility are presented. Two Navier-Stokes flow solvers, one using structured meshes and the other unstructured meshes, were used to compute longitudinal static stability derivatives for an advanced Blended Wing Body configuration over a wide range of angles of attack. The computations were performed for two different Reynolds numbers and the resulting forces and moments are compared with the above mentioned wind tunnel data.

Pao, S. Paul; Biedron, Robert T.; Park, Michael A.; Fremaux, C. Michael; Vicroy, Dan D.

2005-01-01

290

Navier-Stokes Computations of Longitudinal Forces and Moments for a Blended Wing Body  

NASA Technical Reports Server (NTRS)

The object of this paper is to investigate the feasibility of applying CFD methods to aerodynamic analyses for aircraft stability and control. The integrated aerodynamic parameters used in stability and control, however, are not necessarily those extensively validated in the state of the art CFD technology. Hence, an exploratory study of such applications and the comparison of the solutions to available experimental data will help to assess the validity of the current computation methods. In addition, this study will also examine issues related to wind tunnel measurements such as measurement uncertainty and support interference effects. Several sets of experimental data from the NASA Langley 14x22-Foot Subsonic Tunnel and the National Transonic Facility are presented. Two Navier-Stokes flow solvers, one using structured meshes and the other unstructured meshes, were used to compute longitudinal static stability derivatives for an advanced Blended Wing Body configuration over a wide range of angles of attack. The computations were performed for two different Reynolds numbers and the resulting forces and moments are compared with the above mentioned wind tunnel data.

Pao, S. Paul; Biedron, Robert T.; Park, Michael A.; Fremaux, C. Michael; Vicroy, Dan D.

2004-01-01

291

Magnetic Resonance Force Microscopy of paramagnetic electron spins at millikelvin temperatures  

E-print Network

Magnetic Resonance Force Microscopy (MRFM) is a powerful technique to detect a small number of spins that relies on force-detection by an ultrasoft magnetically tipped cantilever and selective magnetic resonance manipulation of the spins. MRFM would greatly benefit from ultralow temperature operation, because of lower thermomechanical noise and increased thermal spin polarization. Here, we demonstrate MRFM operation at temperatures as low as 30 mK, thanks to a recently developed SQUID-based cantilever detection technique which avoids cantilever overheating. In our experiment, we detect dangling bond paramagnetic centers on a silicon surface down to millikelvin temperatures. Fluctuations of such kind of defects are supposedly linked to 1/$f$ magnetic noise and decoherence in SQUIDs and in several superconducting and single spin qubits. We find evidence that spin diffusion plays a key role in the low temperature spin dynamics.

Vinante, A; Usenko, O; Wijts, G; Oosterkamp, T H

2011-01-01

292

Magnetic Resonance Force Microscopy of paramagnetic electron spins at millikelvin temperatures  

E-print Network

Magnetic Resonance Force Microscopy (MRFM) is a powerful technique to detect a small number of spins that relies on force-detection by an ultrasoft magnetically tipped cantilever and selective magnetic resonance manipulation of the spins. MRFM would greatly benefit from ultralow temperature operation, because of lower thermomechanical noise and increased thermal spin polarization. Here, we demonstrate MRFM operation at temperatures as low as 30 mK, thanks to a recently developed SQUID-based cantilever detection technique which avoids cantilever overheating. In our experiment, we detect dangling bond paramagnetic centers on a silicon surface down to millikelvin temperatures. Fluctuations of such kind of defects are supposedly linked to 1/f magnetic noise and decoherence in SQUIDs as well as in several superconducting and single spin qubits. We find evidence that spin diffusion plays a key role in the low temperature spin dynamics.

A. Vinante; G. Wijts; O. Usenko; L. Schinkelshoek; T. H. Oosterkamp

2011-05-17

293

Nonlinear force-free coronal magnetic field extrapolation scheme based on the direct boundary integral formulation  

NASA Astrophysics Data System (ADS)

The boundary integral equation (BIE) method was first proposed by Yan and Sakurai (2000) and used to extrapolate the nonlinear force-free magnetic field in the solar atmosphere. Recently, Yan and Li (2006) improved the BIE method and proposed the direct boundary integral equation (DBIE) formulation, which represents the nonlinear force-free magnetic field by direct integration of the magnetic field on the bottom boundary surface. On the basis of this new method, we devised a practical calculation scheme for the nonlinear force-free field extrapolation above solar active regions. The code of the scheme was tested by the analytical solutions of Low and Lou (1990) and was applied to the observed vector magnetogram of solar active region NOAA 9077. The results of the calculations show that the improvement of the new computational scheme to the scheme of Yan and Li (2006) is significant, and the force-free and divergence-free constraints are well satisfied in the extrapolated fields. The calculated field lines for NOAA 9077 present the X-shaped structure and can be helpful for understanding the magnetic configuration of the filament channel as well as the magnetic reconnection process during the Bastille Day flare on 14 July 2000.

He, Han; Wang, Huaning

2008-05-01

294

Magnetic buoyancy force acting on bubbles in nonconducting and diamagnetic fluids under microgravity  

SciTech Connect

The magnetic buoyancy force acting on a bubble in a one-dimensional magnetic field can be represented as F=({chi}{sub G}{minus}{chi}{sub L}){integral}H(dH/dx)dVol{sub B}, where {chi}{sub G} and {chi}{sub L} are the volume magnetic susceptibilities of the gas and liquid, respectively, and {ital H} is the magnetic field strength. Since {vert_bar}{chi}{sub L}{vert_bar}{gt}{vert_bar}{chi}{sub G}{vert_bar} and most liquids are diamagnetic, this expression indicates that the magnetic buoyancy forces act in the direction of increasing magnetic field strength. Because the magnetic buoyancy force in a diamagnetic fluid is small, the motion of bubbles under normal gravity is difficult to study, but microgravity offers the possibility of detailed observations. Using a compact permanent magnet under microgravity conditions, N{sub 2} bubbles in pure water (0.01 dyne s/cm{sup 2}) and in a 69:31 glycerol/water mixture (0.21 dyne s/cm{sup 2}) were found to move in the direction of increasing {ital H}, and to be held stationary at the point of maximum {ital H}. The motion of the bubbles was also simulated with a theoretical model and was found to agree with measurements made under microgravity conditions. These results indicate that magnetic buoyancy can be used to control bubble motion. Since most fluids are diamagnetic, magnetic buoyancy can be used to control bubbles in many fluidic devices used in space applications.{copyright} {ital 1997 American Institute of Physics.}

Wakayama, N.I. [National Institute of Materials and Chemical Research, Higashi 1-1, Tsukuba, Ibaraki 305 (Japan)] [National Institute of Materials and Chemical Research, Higashi 1-1, Tsukuba, Ibaraki 305 (Japan)

1997-04-01

295

Mechanical characterization of journal superconducting magnetic bearings: stiffness, hysteresis and force relaxation  

NASA Astrophysics Data System (ADS)

Superconducting magnetic bearings (SMBs) can provide stable levitation without direct contact between them and a magnetic source (typically a permanent magnet). In this context, superconducting magnetic levitation provides a new tool for mechanical engineers to design non-contact mechanisms solving the tribological problems associated with contact at very low temperatures. In the last years, different mechanisms have been proposed taking advantage of superconducting magnetic levitation. Flywheels, conveyors or mechanisms for high-precision positioning. In this work the mechanical stiffness of a journal SMBs have been experimentally studied. Both radial and axial stiffness have been considered. The influence of the size and shape of the permanent magnets (PM), the size and shape of the HTS, the polarization and poles configuration of PMs of the journal SMB have been studied experimentally. Additionally, in this work hysteresis behavior and force relaxation are considered because they are essential for mechanical engineer when designing bearings that hold levitating axles.

Cristache, Cristian; Valiente-Blanco, Ignacio; Diez-Jimenez, Efren; Alvarez-Valenzuela, Marco Antonio; Pato, Nelson; Perez-Diaz, Jose Luis

2014-05-01

296

An energy-conserving formalism for adaptive gravitational force softening in SPH and N-body codes  

E-print Network

In this paper we describe an adaptive softening length formalism for collisionless N-body and self-gravitating Smoothed Particle Hydrodynamics (SPH) calculations which conserves momentum and energy exactly. This means that spatially variable softening lengths can be used in N-body calculations without secular increases in energy. The formalism requires the calculation of a small additional term to the gravitational force related to the gradient of the softening length. The extra term is similar in form to the usual SPH pressure force (although opposite in direction) and is therefore straightforward to implement in any SPH code at almost no extra cost. For N-body codes some additional cost is involved as the formalism requires the computation of the density via a summation over neighbouring particles using the smoothing kernel. The results of numerical tests demonstrate that, for homogeneous mass distributions, the use of adaptive softening lengths gives a softening which is always close to the `optimal' choic...

Price, D J

2006-01-01

297

Single-Spin Measurement and Decoherence in Magnetic Resonance Force Microscopy  

E-print Network

We consider a simple version of a cyclic adiabatic inversion (CAI) technique in magnetic resonance force microscopy (MRFM). We study the problem: What component of the spin is measured in the CAI MRFM? We show that the non-destructive detection of the cantilever vibrations provides a measurement of the spin component along the effective magnetic field. This result is based on numerical simulations of the Hamiltonian dynamics (the Schrodinger equation) and the numerical solution of the master equation.

G. P. Berman; F. Borgonovi; H. S. Goan; S. A. Gurvitz; V. I. Tsifrinovich

2002-10-07

298

Fuzzy modeling of disturbance torques\\/forces in rotational\\/linear interior permanent magnet synchronous motors  

Microsoft Academic Search

We propose several artificial intelligence techniques for fuzzy modeling of electromagnetic and disturbance (friction, ripples) torques\\/ forces in permanent magnet rotational\\/linear motors. Based on a model taking into account several nonlinear phenomena such as non-sinusoidal flux linkage, saturation effects, cross-magnetization etc we use observer-based parameter identifiers approach to plan identification experiments. We investigate and compare several training algorithms to tune

J. Kabzinski

2005-01-01

299

Confinement of Plasma along Shaped Open Magnetic Fields from the Centrifugal Force of Supersonic Plasma Rotation  

SciTech Connect

Interferometric density measurements in plasmas rotating in shaped, open magnetic fields demonstrate strong confinement of plasma parallel to the magnetic field, with density drops of more than a factor of 10. Taken together with spectroscopic measurements of supersonic ExB rotation of sonic Mach 2, these measurements are in agreement with ideal MHD theory which predicts large parallel pressure drops balanced by centrifugal forces in supersonically rotating plasmas.

Teodorescu, C.; Young, W. C.; Swan, G. W. S.; Ellis, R. F.; Hassam, A. B.; Romero-Talamas, C. A. [University of Maryland, College Park, Maryland 20742 (United States)

2010-08-20

300

Electric contributions to magnetic force microscopy response from graphene and MoS2 nanosheets  

NASA Astrophysics Data System (ADS)

Magnetic force microscopy (MFM) signals have recently been detected from whole pieces of mechanically exfoliated graphene and molybdenum disulfide (MoS2) nanosheets, and magnetism of the two nanomaterials was claimed based on these observations. However, non-magnetic interactions or artefacts are commonly associated with MFM signals, which make the interpretation of MFM signals not straightforward. A systematic investigation has been done to examine possible sources of the MFM signals from graphene and MoS2 nanosheets and whether the MFM signals can be correlated with magnetism. It is found that the MFM signals have significant non-magnetic contributions due to capacitive and electrostatic interactions between the nanosheets and conductive cantilever tip, as demonstrated by electric force microscopy and scanning Kevin probe microscopy analyses. In addition, the MFM signals of graphene and MoS2 nanosheets are not responsive to reversed magnetic field of the magnetic cantilever tip. Therefore, the observed MFM response is mainly from electric artefacts and not compelling enough to correlate with magnetism of graphene and MoS2 nanosheets.

Li, Lu Hua; Chen, Ying

2014-12-01

301

Computer program to determine pressure distributions and forces on blunt bodies of revolution  

NASA Technical Reports Server (NTRS)

Program was written to include integration of surface pressure in order to obtain axial-force, normal-force, and pitching-moment coefficients. Program was written in CDC FORTRAN for the CDC-6600 computer system.

Jackson, C. M., Jr.; Sawyer, W. C.; Smith, R. S.

1973-01-01

302

Wave function collapses in a single spin magnetic resonance force microscopy  

E-print Network

We study the effects of wave function collapses in the oscillating cantilever driven adiabatic reversals (OSCAR) magnetic resonance force microscopy (MRFM) technique. The quantum dynamics of the cantilever tip (CT) and the spin is analyzed and simulated taking into account the magnetic noise on the spin. The deviation of the spin from the direction of the effective magnetic field causes a measurable shift of the frequency of the CT oscillations. We show that the experimental study of this shift can reveal the information about the average time interval between the consecutive collapses of the wave function

Berman, G P; Tsifrinovich, V I

2004-01-01

303

Wave function collapses in a single spin magnetic resonance force microscopy  

E-print Network

We study the effects of wave function collapses in the oscillating cantilever driven adiabatic reversals (OSCAR) magnetic resonance force microscopy (MRFM) technique. The quantum dynamics of the cantilever tip (CT) and the spin is analyzed and simulated taking into account the magnetic noise on the spin. The deviation of the spin from the direction of the effective magnetic field causes a measurable shift of the frequency of the CT oscillations. We show that the experimental study of this shift can reveal the information about the average time interval between the consecutive collapses of the wave function

G. P. Berman; F. Borgonovi; V. I. Tsifrinovich

2004-04-20

304

Quantitative assessment of pinning forces and magnetic penetration depth in NbN thin films from complementary magnetic force microscopy and transport measurements  

NASA Astrophysics Data System (ADS)

Epitaxial niobium nitride thin films with a critical temperature of Tc=16 K and a thickness of 100 nm were fabricated on MgO (100) substrates by pulsed laser deposition. Low-temperature magnetic-force-microscopy (MFM) images of the supercurrent vortices were measured after field cooling in a magnetic field of 3 mT at various temperatures. The temperature dependence of the penetration depth has been evaluated by a two-dimensional fitting of the vortex profiles in the monopole-monopole model. Its subsequent fit to a single s-wave-gap function results in the superconducting gap amplitude, ?(0)=(2.90.4) meV =(2.10.3)kBTc, which perfectly agrees with the previous reports. The pinning force has been independently estimated from the local depinning of individual vortices by the lateral forces exerted by the MFM tip and from transport measurements. A good quantitative agreement between the two techniques shows that for low fields, B??0Hc2, MFM is a powerful and reliable technique to probe the local variations of the pinning landscape. We also demonstrate that the monopole model can be successfully applied even for thin films with a thickness comparable to the penetration depth.

Shapoval, T.; Stopfel, H.; Haindl, S.; Engelmann, J.; Inosov, D. S.; Holzapfel, B.; Neu, V.; Schultz, L.

2011-06-01

305

Realistic simulations of single-spin nondemolition measurement by magnetic resonance force microscopy  

E-print Network

A requirement for many quantum computation schemes is the ability to measure single spins. This paper examines one proposed scheme: magnetic resonance force microscopy, including the effects of thermal noise and back-action from monitoring. We derive a simplified equation using the adiabatic approximation, and produce a stochastic pure state unraveling which is useful for numerical simulations.

Brun, T A; Brun, Todd A.; Goan, Hsi-Sheng

2003-01-01

306

Realistic simulations of single-spin nondemolition measurement by magnetic resonance force microscopy  

E-print Network

A requirement for many quantum computation schemes is the ability to measure single spins. This paper examines one proposed scheme: magnetic resonance force microscopy, including the effects of thermal noise and back-action from monitoring. We derive a simplified equation using the adiabatic approximation, and produce a stochastic pure state unraveling which is useful for numerical simulations.

Todd A. Brun; Hsi-Sheng Goan

2003-02-25

307

Generation of magnetic field, vortices and relativistic particles by the nonpotential ponderomotive force  

Microsoft Academic Search

Effects of nonpotential ponderomotive force on kinetic phenomena in a plasma are presented. The particle distribution function is derived, which allows one to calculate the particle and heat fluxes. A novel relativistic hydrodynamic equation of motion, incorporating self-generated magnetic fields, is obtained, which admits no frozen-in condition. The generation of electron fluid vortices by a laser pulse in initially unmagnetized

Nodar L. Tsintsadze; Kunioki Mima; Levan N. Tsintsadze; Kyoji Nishikawa

2002-01-01

308

Simulations of a Single Spin Measurement Using Magnetic Resonance Force Microscopy  

Microsoft Academic Search

We simulated classical and quantum dynamics of a single spin measurement in magnetic resonant force microscopy (MRFM). A frequency shift of the cantilever is calculated analytically and numerically in the regime of driven oscillations of the cantilever. We study the problem: What component of the spin is measured in the cyclic adiabatic inversion MRFM? We show that a MRFM technique

Gennady Berman; Fausto Borgonovi; Vyacheslav Gorshkov; Shmuel Gurvitz; Dmitry Kamenev; Vladimir Tsifrinovich

2003-01-01

309

Misorientations in [001] magnetite thin films studied by electron backscatter diffraction and magnetic force microscopy  

Microsoft Academic Search

Magnetite thin films grown on [001] oriented MgO substrates are analyzed by means of electron backscatter diffraction (EBSD) analysis and magnetic force microscopy in applied fields. The EBSD technique enables the crystallographic orientation of individual grains to be determined with a high spatial resolution up to 20 nm on such ceramic samples. A high image quality of the recorded Kikuchi

A. Koblischka-Veneva; M. R. Koblischka; J. D. Wei; Y. Zhou; S. Murphy; F. Mcklich; U. Hartmann; I. V. Shvets

2007-01-01

310

Automated SolidPhase Subcloning Based on Beads Brought into Proximity by Magnetic Force  

Microsoft Academic Search

In the fields of proteomics, metabolic engineering and synthetic biology there is a need for high-throughput and reliable cloning methods to facilitate construction of expression vectors and genetic pathways. Here, we describe a new approach for solid-phase cloning in which both the vector and the gene are immobilized to separate paramagnetic beads and brought into proximity by magnetic force. Ligation

Elton P. Hudson; Andrej Nikoshkov; Mathias Uhlen; Johan Rockberg

2012-01-01

311

Magnetic force microscopy study of edge overwrite characteristics in thin film media  

Microsoft Academic Search

In this paper, track edge overwrite characteristics in planar isotropic longitudinal thin film media were studied by direct magnetic force microscopy imaging of the edge overwrite patterns. It is found that edge erasure strongly depends on the phase difference between the transitions in the overwriting and overwritten tracks at track edges. If the transitions in the adjacent tracks are in-phase,

Jian-Gang Zhu; Yansheng Luo; Juren Ding

1994-01-01

312

An energy-conserving formalism for adaptive gravitational force softening in SPH and N-body codes  

E-print Network

In this paper we describe an adaptive softening length formalism for collisionless N-body and self-gravitating Smoothed Particle Hydrodynamics (SPH) calculations which conserves momentum and energy exactly. This means that spatially variable softening lengths can be used in N-body calculations without secular increases in energy. The formalism requires the calculation of a small additional term to the gravitational force related to the gradient of the softening length. The extra term is similar in form to the usual SPH pressure force (although opposite in direction) and is therefore straightforward to implement in any SPH code at almost no extra cost. For N-body codes some additional cost is involved as the formalism requires the computation of the density via a summation over neighbouring particles using the smoothing kernel. The results of numerical tests demonstrate that, for homogeneous mass distributions, the use of adaptive softening lengths gives a softening which is always close to the `optimal' choice of fixed softening parameter, removing the need for fine-tuning. For a heterogeneous mass distribution (as may be found in any large scale N-body simulation) we find that the errors on the least-dense component are lowered by an order of magnitude compared to the use of a fixed softening length tuned to the densest component. For SPH codes our method presents a natural and elegant choice of softening formalism which makes a small improvement to both the force resolution and the total energy conservation at almost zero additional cost.

D. J. Price; J. J. Monaghan

2006-10-30

313

ON THE FORCE-FREE NATURE OF PHOTOSPHERIC SUNSPOT MAGNETIC FIELDS AS OBSERVED FROM HINODE (SOT/SP)  

SciTech Connect

A magnetic field is force-free if there is no interaction between it and the plasma in the surrounding atmosphere, i.e., electric currents are aligned with the magnetic field, giving rise to zero Lorentz force. The computation of various magnetic parameters, such as magnetic energy (using the virial theorem), gradient of twist of sunspot magnetic fields (computed from the force-free parameter {alpha}), and any kind of extrapolation, heavily hinges on the force-free approximation of the photospheric sunspot magnetic fields. Thus, it is of vital importance to inspect the force-free behavior of sunspot magnetic fields. The force-free nature of sunspot magnetic fields has been examined earlier by some researchers, ending with incoherent results. Accurate photospheric vector field measurements with high spatial resolution are required to inspect the force-free nature of sunspots. For this purpose, we use several vector magnetograms of high spatial resolution obtained from the Solar Optical Telescope/Spectro-Polarimeter on board Hinode. Both the necessary and sufficient conditions for force-free nature are examined by checking the global and local nature of equilibrium magnetic forces over sunspots. We find that sunspot magnetic fields are not very far from the force-free configuration, although they are not completely force-free on the photosphere. The umbral and inner penumbral fields are more force-free than the middle and outer penumbral fields. During their evolution, sunspot magnetic fields are found to maintain their proximity to force-free field behavior. Although a dependence of net Lorentz force components is seen on the evolutionary stages of the sunspots, we do not find a systematic relationship between the nature of sunspot magnetic fields and the associated flare activity. Further, we examine whether the fields at the photosphere follow linear or nonlinear force-free conditions. After examining this in various complex and simple sunspots, we conclude that, in either case, photospheric sunspot magnetic fields are closer to satisfying the nonlinear force-free field approximation.

Tiwari, Sanjiv Kumar, E-mail: tiwari@mps.mpg.de [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur 313 001 (India)

2012-01-01

314

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

PubMed

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. PMID:24896585

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

2014-06-27

315

Two-Dimensional Lorentz Force Image Reconstruction for Magnetoacoustic Tomography with Magnetic Induction  

NASA Astrophysics Data System (ADS)

Magnetoacoustic tomography with magnetic induction has shown potential applications in imaging the electrical impedance for biological tissues. We present a novel methodology for the inverse problem solution of the 2-D Lorentz force distribution reconstruction based on the acoustic straight line propagation theory. The magnetic induction and acoustic generation as well as acoustic detection are theoretically provided as explicit formulae and also validated by the numerical simulations for a multilayered cylindrical phantom model. The reconstructed 2-D Lorentz force distribution reveals not only the conductivity configuration in terms of shape and size but also the amplitude value of the Lorentz force in the examined layer. This study provides a basis for further study of conductivity distribution reconstruction of MAT-MI in medical imaging.

Li, Yi-Ling; Liu, Zhen-Bo; Ma, Qing-Yu; Guo, Xia-Sheng; Zhang, Dong

2010-08-01

316

Paramagnetic and ferromagnetic resonance imaging with a tip-on-cantilever magnetic resonance force microscope  

NASA Astrophysics Data System (ADS)

A magnetic resonance force microscope with a "tip-on-cantilever" configuration was used to compare imaging characteristics of paramagnetic and ferromagnetic samples. Three-dimensional electron paramagnetic resonance (EPR) imaging of diphenylpicrylhydrazil (DPPH) particles was accomplished by scanning the sample in two dimensions while stepping an external field. The EPR force map showed broad response reflecting the size and shape of the sample, allowing a three-dimensional real-space magnetization image to be successfully reconstructed. In contrast to the EPR case, ferromagnetic resonance imaging of a micron-scale yttrium iron garnet sample showed no significant line broadening despite the strong field gradient (10 G/?m). Two-dimensional force maps revealed spatial dependence of magnetostatic and magnetoelastic modes.

Wago, K.; Botkin, D.; Yannoni, C. S.; Rugar, D.

1998-05-01

317

Fictitious forces and simulated magnetic fields in rotating reference frames.  

PubMed

We show that the Wigner-Bargmann program of grounding nonrelativistic quantum mechanics in the unitary projective representations of the Galilei group can be extended to include all noninertial reference frames. The key concept is the Galilean line group, the group of transformations that ties together all accelerating reference frames, and its representations. These representations are constructed under the natural constraint that they reduce to the well-known unitary, projective representations of the Galilei group when the transformations are restricted to inertial reference frames. This constraint can be accommodated only for a class of representations with a sufficiently rich cocycle structure. Unlike the projective representations of the Galilei group, these cocycle representations of the Galilean line group do not correspond to central extensions of the group. Rather, they correspond to a class of nonassociative extensions, known as loop prolongations, that are determined by three-cocycles. As an application, we show that the phase shifts due to the rotation of Earth that have been observed in neutron interferometry experiments and the rotational effects that lead to simulated magnetic fields in optical lattices can be rigorously derived from the representations of the loop prolongations of the Galilean line group. PMID:24182238

Klink, W H; Wickramasekara, S

2013-10-18

318

The Effect of Tension and a Longitudinal Magnetic Field on the ThermoelectroMotive Forces in Permalloy  

Microsoft Academic Search

Measurements have been made on the combined effect of tension and a longitudinal magnetic field on the thermoelectromotive force in three specimens of permalloy. The specimens were in the form of wires, the composition being 78, 81 and 84 percent nickel with the remaining part iron. In all cases the magnetic field produces a decrease in the thermoelectromotive force. Annealing

Alpheus W. Smith; Joy Dillinger

1929-01-01

319

High-force NdFeB-based magnetic tweezers device optimized for microrheology experiments.  

PubMed

We present the design, calibration, and testing of a magnetic tweezers device that employs two pairs of permanent neodymium iron boron magnets surrounded by low-carbon steel focusing tips to apply large forces to soft materials for microrheology experiments. Our design enables the application of forces in the range of 1-1800 pN to ?4.5 ?m paramagnetic beads using magnet-bead separations in the range of 0.3-20 mm. This allows the use of standard coverslips and sample geometries. A high speed camera, custom LED-based illumination scheme, and mechanically stabilized measurement platform are employed to enable the measurement of materials with viscoelastic moduli as high as ?1 kPa. PMID:22667631

Lin, Jun; Valentine, Megan T

2012-05-01

320

High-force NdFeB-based magnetic tweezers device optimized for microrheology experiments  

SciTech Connect

We present the design, calibration, and testing of a magnetic tweezers device that employs two pairs of permanent neodymium iron boron magnets surrounded by low-carbon steel focusing tips to apply large forces to soft materials for microrheology experiments. Our design enables the application of forces in the range of 1-1800 pN to {approx}4.5 {mu}m paramagnetic beads using magnet-bead separations in the range of 0.3-20 mm. This allows the use of standard coverslips and sample geometries. A high speed camera, custom LED-based illumination scheme, and mechanically stabilized measurement platform are employed to enable the measurement of materials with viscoelastic moduli as high as {approx}1 kPa.

Lin Jun [Department of Mechanical Engineering, University of California, Santa Barbara, California 93106 (United States); Biomolecular Science and Engineering Program, University of California, Santa Barbara, California 93106 (United States); Valentine, Megan T. [Department of Mechanical Engineering, University of California, Santa Barbara, California 93106 (United States)

2012-05-15

321

Quantitative magnetic resonance analysis and a morphometric predictive model reveal lean body mass changes in migrating Nearctic-Neotropical passerines.  

PubMed

Most studies of lean mass dynamics in free-living passerine birds have focused on Old World species at geographical barriers where they are challenged to make the longest non-stop flight of their migration. We examined lean mass variation in New World passerines in an area where the distribution of stopover habitat does not require flights to exceed more than a few hours and most migrants stop flying well before fat stores near exhaustion. We used either quantitative magnetic resonance (QMR) analysis or a morphometric model to measure or estimate, respectively, the fat and lean body mass of migrants during stopovers in New York, USA. With these data, we examined (1) variance in total body mass explained by lean body mass, (2) hourly rates of fat and lean body mass change in single-capture birds, and (3) net changes in fat and lean mass in recaptured birds. Lean mass contributed to 50% of the variation in total body mass among white-throated sparrows Zonotrichia albicollis and hermit thrushes Catharus guttatus. Lean mass of refueling gray catbirds Dumetella carolinensis and white-throated sparrows, respectively, increased 1.123 and 0.320gh(-1). Lean mass of ovenbirds Seiurus aurocapillus accounted for an estimated 33-40% of hourly gains in total body mass. On average 35% of the total mass gained among recaptured birds was lean mass. Substantial changes in passerine lean mass are not limited to times when birds are forced to make long, non-stop flights across barriers. Protein usage during migration is common across broad taxonomic groups, migration systems, and migration strategies. PMID:21079970

Seewagen, Chad L; Guglielmo, Christopher G

2011-04-01

322

Electromotive force and large-scale magnetic dynamo in a turbulent flow with a mean shear.  

PubMed

An effect of sheared large-scale motions on a mean electromotive force in a nonrotating turbulent flow of a conducting fluid is studied. It is demonstrated that in a homogeneous divergence-free turbulent flow the alpha effect does not exist, however a mean magnetic field can be generated even in a nonrotating turbulence with an imposed mean velocity shear due to a "shear-current" effect. A mean velocity shear results in an anisotropy of turbulent magnetic diffusion. A contribution to the electromotive force related to the symmetric parts of the gradient tensor of the mean magnetic field (the kappa effect) is found in nonrotating turbulent flows with a mean shear. The kappa effect and turbulent magnetic diffusion reduce the growth rate of the mean magnetic field. It is shown that a mean magnetic field can be generated when the exponent of the energy spectrum of the background turbulence (without the mean velocity shear) is less than 2. The shear-current effect was studied using two different methods: the tau approximation (the Orszag third-order closure procedure) and the stochastic calculus (the path integral representation of the solution of the induction equation, Feynman-Kac formula, and Cameron-Martin-Girsanov theorem). Astrophysical applications of the obtained results are discussed. PMID:14524884

Rogachevskii, Igor; Kleeorin, Nathan

2003-09-01

323

NONLINEAR FORCE-FREE MAGNETIC FIELD FITTING TO CORONAL LOOPS WITH AND WITHOUT STEREOSCOPY  

SciTech Connect

We developed a new nonlinear force-free magnetic field (NLFFF) forward-fitting algorithm based on an analytical approximation of force-free and divergence-free NLFFF solutions, which requires as input a line-of-sight magnetogram and traced two-dimensional (2D) loop coordinates of coronal loops only, in contrast to stereoscopically triangulated three-dimensional loop coordinates used in previous studies. Test results of simulated magnetic configurations and from four active regions observed with STEREO demonstrate that NLFFF solutions can be fitted with equal accuracy with or without stereoscopy, which relinquishes the necessity of STEREO data for magnetic modeling of active regions (on the solar disk). The 2D loop tracing method achieves a 2D misalignment of {mu}{sub 2} = 2. Degree-Sign 7 {+-} 1. Degree-Sign 3 between the model field lines and observed loops, and an accuracy of Almost-Equal-To 1.0% for the magnetic energy or free magnetic energy ratio. The three times higher spatial resolution of TRACE or SDO/AIA (compared with STEREO) also yields a proportionally smaller misalignment angle between model fit and observations. Visual/manual loop tracings are found to produce more accurate magnetic model fits than automated tracing algorithms. The computation time of the new forward-fitting code amounts to a few minutes per active region.

Aschwanden, Markus J., E-mail: aschwanden@lmsal.com [Lockheed Martin Advanced Technology Center, Solar and Astrophysics Laboratory, Org. ADBS, Bldg. 252, 3251 Hanover St., Palo Alto, CA 94304 (United States)

2013-02-15

324

Three-body forces in nuclear matter from intermediate Delta-states in three-nucleon clusters  

Microsoft Academic Search

Those three-body force contributions in nuclear matter usually generated through a piN scattering amplitude dominated by the Delta(1236) resonance, are here treated as a three-nucleon cluster, in which one of the nucleons becomes, in an intermediate state, a Delta-resonance. All exchange diagrams are calculated and found to significantly reduce the energy per particle from the direct graph. This is contrary

T. Kouki; L. E. W. Smulter; A. M. Green

1977-01-01

325

Grey box-based inverse wagon model to predict wheelrail contact forces from measured wagon body responses  

Microsoft Academic Search

A grey box-based inverse wagon model was developed to estimate wheelrail contact forces using only measurements of wagon body responses as inputs. The project is based on a similar application using a deterministic inverse wagon model [F. Xia, C. Cole, and P. Wolfs, An inverse railway wagon model and its applications, Veh. Syst. Dyn. 45 (6) (2007), pp. 583605]. The

Fujie Xia; Colin Cole; Peter Wolfs

2008-01-01

326

Robust tracking control of a magnetically suspended rigid body  

NASA Technical Reports Server (NTRS)

This study is an application of H-infinity and micro-synthesis for designing robust tracking controllers for the Large Angle Magnetic Suspension Test Facility. The modeling, design, analysis, simulation, and testing of a control law that guarantees tracking performance under external disturbances and model uncertainties is investigated. The type of uncertainties considered and the tracking performance metric used is discussed. This study demonstrates the tradeoff between tracking performance at low frequencies and robustness at high frequencies. Two sets of controllers were designed and tested. The first set emphasized performance over robustness, while the second set traded off performance for robustness. Comparisons of simulation and test results are also included. Current simulation and experimental results indicate that reasonably good robust tracking performance can be attained for this system using multivariable robust control approach.

Lim, Kyong B.; Cox, David E.

1994-01-01

327

Magnetic susceptibility variations in Loess sequences and their relationship to astronomical forcing  

NASA Technical Reports Server (NTRS)

The long, well-exposed and often continuous sequences of loess found throughout the world are generally thought to provide an excellent opportunity for studying long-term, large-scale environmental change during the last few million years. In recent years, the most fruitful loess studies have been those involving the deposits of the loess in China. One of the most intriguing results of that work has been the discovery of an apparent correlation between variations in the magnetic susceptibility of the loess sequence and the oxygen isotope record of the deep sea. This correlation implies that magnetic susceptibility variations are being driven by astronomical parameters. However, the basic data have been interpreted in various ways by different authors, most of whom assumed that the magnetic minerals in the loess have not been affected by post-depositional processes. Using a chemical extraction procedure that allows us to separate the contribution of secondary pedogenic magnetic minerals from primary inherited magnetic minerals, we have found that the magnetic susceptibility of the Chinese paleosols is largely due to a pedogenic component which is present to a lesser degree in the loess. We have also found that the smaller inherited component of the magnetic susceptibility is about the same in the paleosols and the loess. These results demonstrate the need for additional study of the processes that create magnetic susceptibility variations in order to interpret properly the role of astronomical forcing in producing these variations.

Verosub, Kenneth L.; Singer, Michael J.

1992-01-01

328

Atomic-scale friction measurements using friction force microscopy. Part 2: Application to magnetic media  

NASA Astrophysics Data System (ADS)

Atomic Force/Friction Force Microscopes (AFM/FFM) were used to study tribological properties of metal-particle tapes with two roughnesses, Co-gamma Fe2O3 tapes (unwiped and wiped), and unlubricated and lubricated thin-film magnetic rigid disks (as-polished and standard textured). Nanoindentation studies showed that the hardness of the tapes through the magnetic coating is not uniform. These results are consistent with the fact that the tape surface is a composite and is not homogeneous. Nanoscratch experiments performed on magnetic tapes using silicon nitride tips revealed that deformation and displacement of tape surface material occurred after one pass under light loads (approx. 100 nN). A comparison between friction force profiles and the corresponding surface roughness profiles of all samples tested shows a poor correlation between localized values of friction and surface roughness. Detailed studies of friction and surface profiles demonstrate an excellent correlation between localized variation of the slope of the surface roughness along the sliding direction and the localized variation of friction. Atomic-scale friction in magnetic media and natural diamond appears to be due to adhesive and ratchet (roughness) mechanisms. Directionality in the local variation of atomic-scale friction data was observed as the samples were scanned in either direction, resulting from the scanning direction and the anisotropy in the surface topography. Atomic-scale coefficient of friction is generally found to be smaller than the macrocoefficient of friction as there may be less ploughing contribution in atomic-scale measurements.

Bhushan, Bharat; Ruan, Ju-Ai

1993-05-01

329

Observation of force-detected nuclear magnetic resonance in a homogeneous field  

PubMed Central

We report the experimental realization of BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient), a sensitive and general method of magnetic resonance. The prototype millimeter-scale NMR spectrometer shows signal and noise levels in agreement with the design principles. We present 1H and 19F NMR in both solid and liquid samples, including time-domain Fourier transform NMR spectroscopy, multiple-pulse echoes, and heteronuclear J spectroscopy. By measuring a 1H-19F J coupling, this last experiment accomplishes chemically specific spectroscopy with force-detected NMR. In BOOMERANG, an assembly of permanent magnets provides a homogeneous field throughout the sample, while a harmonically suspended part of the assembly, a detector, is mechanically driven by spin-dependent forces. By placing the sample in a homogeneous field, signal dephasing by diffusion in a field gradient is made negligible, enabling application to liquids, in contrast to other force-detection methods. The design appears readily scalable to ?m-scale samples where it should have sensitivity advantages over inductive detection with microcoils and where it holds great promise for application of magnetic resonance in biology, chemistry, physics, and surface science. We briefly discuss extensions of the BOOMERANG method to the ?m and nm scales. PMID:15326302

Madsen, L. A.; Leskowitz, G. M.; Weitekamp, D. P.

2004-01-01

330

A comparison of 60 Hz uniform magnetic and electric induction in the human body  

NASA Astrophysics Data System (ADS)

High-resolution computations of induced fields are used to assess equivalent source levels for human exposure to uniform low-frequency electric and magnetic fields. These results pertain to 60 Hz foot-to-head electric excitation of the body in three positions with respect to a ground plane, and to magnetic excitation by three orthogonal source orientations. All computations are based on an anatomically derived human body model composed of 1736 873 cubic voxels with 3.6 mm edges. The data for magnetic excitation are computed using a scalar potential finite difference (SPFD) method, while those for electric excitation are computed using a hybrid method based on the SPFD method coupled with a quasistatic finite difference time domain code. The data are analysed in two ways, using an induced current density threshold of . Firstly, the various field strengths required to produce a whole-body average current density magnitude equal to the threshold are derived for each configuration, and the associated current density levels in various organs and tissues are presented. It is found that the average current density magnitude values in at least one tissue group can be up to 3 (5) times greater than the whole-body average under electric (magnetic) excitation, and that the associated maximum values can be up to 46 (28) times greater than the whole-body average under electric (magnetic) excitation, for at least one source/body configuration. Secondly, the data are analysed from the opposite point of view, in which the source levels required to induce average or maximum induced current density magnitudes at the threshold level in specific tissue groups are determined. Evaluations such as the present one should prove useful in the development of protection standards, and are also expected to aid in the understanding of results from various animal and tissue culture studies.

Dawson, Trevor W.; Caputa, Kris; Stuchly, Maria A.

1997-12-01

331

Expanded Equations for Torque and Force on a Cylindrical Permanent Magnet Core in a Large-Gap Magnetic Suspension System  

NASA Technical Reports Server (NTRS)

The expanded equations for torque and force on a cylindrical permanent magnet core in a large-gap magnetic suspension system are presented. The core is assumed to be uniformly magnetized, and equations are developed for two orientations of the magnetization vector. One orientation is parallel to the axis of symmetry, and the other is perpendicular to this axis. Fields and gradients produced by suspension system electromagnets are assumed to be calculated at a point in inertial space which coincides with the origin of the core axis system in its initial alignment. Fields at a given point in the core are defined by expanding the fields produced at the origin as a Taylor series. The assumption is made that the fields can be adequately defined by expansion up to second-order terms. Examination of the expanded equations for the case where the magnetization vector is perpendicular to the axis of symmetry reveals that some of the second-order gradient terms provide a method of generating torque about the axis of magnetization and therefore provide the ability to produce six-degree-of-freedom control.

Groom, Nelson J.

1997-01-01

332

Report of the Task Force on SSC Magnet System Test Site  

SciTech Connect

The Task Force on SSC Magnet Systems test Site was appointed by Maury Tigner, Director of the SSC, Phase 1 in August 1984. In brief, the charge asked the Task Force to make a critical evaluation of potential test sites for a major SSC magnet System Test Facility (STF) with regard to: (1) availability of the needed space, utilities, staff and other requirements on the desired time scale; and (2) the cost of preparing the sites for the tests and for operating the facilities during the test period. The charge further suggests that, by virtue of existing facilities and availability of experienced staff, BNL and FNAL are the two best candidate sites and that is therefore appears appropriate to restrict the considerations of the Task Force to these sites. During the subsequent deliberations of the Task Force, no new facts were revealed that altered the assumptions of the charge in this regard. The charge does not ask for a specific site recommendation for the STF. Indeed, an agreement on such a recommendation would be difficult to achieve considering the composition of the Task Force, wherein a large fraction of the membership is drawn from the two contending laboratories. Instead, we have attempted to describe the purpose of the facility, outline a productive test program, list the major facilities required, carefully review the laboratories` responses to the facility requirements, and make objective comparisons of the specific features and capabilities offered.

NONE

1984-10-01

333

Ferromagnetic resonance imaging of Co films using magnetic resonance force microscopy  

SciTech Connect

Lateral one-dimensional imaging of cobalt (Co) films by means of microscopic ferromagnetic resonance (FMR) detected using the magnetic resonance force microscope (MRFM) is demonstrated. A novel approach involving scanning a localized magnetic probe is shown to enable FMR imaging in spite of the broad resonance linewidth. We introduce a spatially selective local field by means of a small, magnetically polarized spherical crystallite of yttrium iron garnet (YIG). Using MRFM-detected FMR signals from a sample consisting of two Co films, we can resolve the {approximately}20 {mu}m lateral separation between the films. The results can be qualitatively understood by consideration of the calculated spatial profiles of the magnetic field generated by the YIG sphere. {copyright} {ital 1998 American Vacuum Society.}

Suh, B.J.; Hammel, P.C.; Zhang, Z. [Condensed Matter and Thermal Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Condensed Matter and Thermal Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Midzor, M.M.; Roukes, M.L. [Condensed Matter Physics, California Institute of Technology, Pasadena, California 91125 (United States)] [Condensed Matter Physics, California Institute of Technology, Pasadena, California 91125 (United States); Childress, J.R. [University of Florida, Gainesville, Florida 32611 (United States)] [University of Florida, Gainesville, Florida 32611 (United States)

1998-07-01

334

Enhanced ferromagnetism in grain boundary of Co-doped ZnO films: A magnetic force microscopy study  

NASA Astrophysics Data System (ADS)

Microscopic grain structures and magnetic properties of Co-doped ZnO-patterned films were studied by combinatorial atomic force microscopy and magnetic force microscopy (MFM) imaging. Whereas Co-doped ZnO was not uniformly magnetized, Co ions were homogeneously doped in the films and substitute from the Zn sites. Most Co:ZnO grains were weakly ferromagnetic (FM) and surrounded by strong FM foamlike grain boundaries networks. No MFM contrast was observed in pure ZnO films grown under similar conditions. The findings clearly demonstrate that defective grain boundaries and magnetic doping have key roles FM properties of diluted magnetic oxides.

Lin, M. N.; Hsu, H. S.; Lai, J. Y.; Guo, M. C.; Lin, C. Y.; Li, G. Y.; Chen, F. Y.; Huang, J. J.; Chen, S. F.; Liu, C. P.; Huang, J. C. A.

2011-05-01

335

Asymptotic analysis of force-free magnetic fields of cylindrical symmetry  

NASA Technical Reports Server (NTRS)

It is known from computer calculations that if a force-free magnetic-field configuration is stressed progressively by footpoint displacements, the configuration expands and approaches the open configuration with the same surface flux distribution, and, in the process, the energy of the field increases progressively. Analysis of a simple model of force-free fields of cylindrical symmetry leads to simple asymptotic expressions for the extent and energy of such a configuration. The analysis is carried through for both spherical and planar source surfaces. According to this model, the field evolves in a well-behaved manner with no indication of instability or loss of equilibrium.

Sturrock, P. A.; Antiochos, S. K.; Roumeliotis, G.

1995-01-01

336

Modeling of a linear PM Machine including magnetic saturation and end effects: maximum force-to-current ratio  

Microsoft Academic Search

The use of linear permanent-magnet (PM) actuators increases in a wide variety of applications because of their high force density, robustness, and accuracy. These linear PM motors are often heavily loaded during short intervals of high acceleration, so that magnetic saturation occurs. This paper models saturation and end effects in linear PM motors using magnetic circuit models. The saturating parts

Henk Polinder; Johannes G. Slootweg; Martin J. Hoeijmakers; John C. Compter

2003-01-01

337

The Use of Magnets for Introducing Primary School Students to Some Properties of Forces through Small-Group Pedagogy  

ERIC Educational Resources Information Center

Seventeen Grade Six students were divided into small groups to study the concept of forces in the context of magnets and their properties. The researcher, a pre-service primary school teacher, encouraged the students into conversation about magnets and it was found that, without hesitation, they talked about their prior experience of magnets. The

Carruthers, Rebecca; de Berg, Kevin

2010-01-01

338

Scaling the energy conversion rate from magnetic field reconnection to different bodies  

SciTech Connect

Magnetic field reconnection is often invoked to explain electromagnetic energy conversion in planetary magnetospheres, stellar coronae, and other astrophysical objects. Because of the huge dynamic range of magnetic fields in these bodies, it is important to understand energy conversion as a function of magnetic field strength and related parameters. It is conjectured theoretically and shown experimentally that the energy conversion rate per unit area in reconnection scales as the cube of an appropriately weighted magnetic field strength divided by the square root of an appropriately weighted density. With this functional dependence, the energy release in flares on the Sun, the large and rapid variation of the magnetic flux in the tail of Mercury, and the apparent absence of reconnection on Jupiter and Saturn, may be understood. Electric fields at the perihelion of the Solar Probe Plus mission may be tens of V/m.

Mozer, F. S.; Hull, A. [Space Sciences Laboratory, University of California, Berkeley, California 94720 (United States)

2010-10-15

339

MEMS-Based Force-Detected Nuclear Magnetic Resonance (FDNMR) Spectrometer  

NASA Technical Reports Server (NTRS)

Nuclear Magnetic Resonance (NMR) spectroscopy allows assignment of molecular structure by acquiring the energy spectrum of nuclear spins in a molecule, and by interpreting the symmetry and positions of resonance lines in the spectrum. As such, NMR has become one of the most versatile and ubiquitous spectroscopic methods. Despite these tremendous successes, NMR experiments suffer from inherent low sensitivity due to the relatively low energy of photons in the radio frequency (rt) region of the electromagnetic spectrum. Here, we describe a high-resolution spectroscopy in samples with diameters in the micron range and below. We have reported design and fabrication of force-detected nuclear magnetic resonance (FDNMR).

Lee, Choonsup; Butler, Mark C.; Elgammal, Ramez A.; George, Thomas; Hunt, Brian; Weitekamp, Daniel P.

2006-01-01

340

Many-Body Electrostatic Forces Between Colloidal Particles at Vanishing Ionic Strength  

E-print Network

Electrostatic forces between small groups of colloidal particles are measured using blinking optical tweezers. When the electrostatic screening length is significantly larger than the particle radius, forces are found to be non-pairwise additive. Both pair and multi-particle forces are well described by the linearized Poisson-Boltzmann equation with constant potential boundary conditions. These findings may play an important role in understanding the structure and stability of a wide variety of systems, from micron-sized particles in oil to aqueous nanocolloids.

Jason W. Merrill; Sunil K. Sainis; Eric R. Dufresne

2009-07-03

341

Estimating Three-Dimensional Orientation of Human Body Parts by Inertial/Magnetic Sensing  

PubMed Central

User-worn sensing units composed of inertial and magnetic sensors are becoming increasingly popular in various domains, including biomedical engineering, robotics, virtual reality, where they can also be applied for real-time tracking of the orientation of human body parts in the three-dimensional (3D) space. Although they are a promising choice as wearable sensors under many respects, the inertial and magnetic sensors currently in use offer measuring performance that are critical in order to achieve and maintain accurate 3D-orientation estimates, anytime and anywhere. This paper reviews the main sensor fusion and filtering techniques proposed for accurate inertial/magnetic orientation tracking of human body parts; it also gives useful recipes for their actual implementation. PMID:22319365

Sabatini, Angelo Maria

2011-01-01

342

Estimating three-dimensional orientation of human body parts by inertial/magnetic sensing.  

PubMed

User-worn sensing units composed of inertial and magnetic sensors are becoming increasingly popular in various domains, including biomedical engineering, robotics, virtual reality, where they can also be applied for real-time tracking of the orientation of human body parts in the three-dimensional (3D) space. Although they are a promising choice as wearable sensors under many respects, the inertial and magnetic sensors currently in use offer measuring performance that are critical in order to achieve and maintain accurate 3D-orientation estimates, anytime and anywhere. This paper reviews the main sensor fusion and filtering techniques proposed for accurate inertial/magnetic orientation tracking of human body parts; it also gives useful recipes for their actual implementation. PMID:22319365

Sabatini, Angelo Maria

2011-01-01

343

Investigation of Force-Freeness of Solar Emerging Magnetic Field via Application of the Virial Theorem to MHD Simulations  

E-print Network

Force-freeness of a solar magnetic field is a key to reconstructing invisible coronal magnetic structure of an emerging flux region on the Sun where active phenomena such as flares and coronal mass ejections frequently occur. We have performed magnetohydrodynamic (MHD) simulations which are adjusted to investigate force-freeness of an emerging magnetic field by using the virial theorem. Our focus is on how the force-free range of an emerging flux region develops and how it depends on the twist of a pre-emerged magnetic field. As an emerging flux region evolves, the upper limit of the force-free range continuously increases while the lower limit is asymptotically reduced to the order of a photospheric pressure scale height above the solar surface. As the twist becomes small the lower limit increases and then seems to be saturated. We also discuss the applicability of the virial theorem to an evolving magnetic structure on the Sun.

Kang, Jihye

2014-01-01

344

Magnetic dipole super-resonances and their impact on mechanical forces at optical frequencies.  

PubMed

Artificial magnetism enables various transformative optical phenomena, including negative refraction, Fano resonances, and unconventional nanoantennas, beamshapers, polarization transformers and perfect absorbers, and enriches the collection of electromagnetic field control mechanisms at optical frequencies. We demonstrate that it is possible to excite a magnetic dipole super-resonance at optical frequencies by coating a silicon nanoparticle with a shell impregnated with active material. The resulting response is several orders of magnitude stronger than that generated by bare silicon nanoparticles and is comparable to electric dipole super-resonances excited in spaser-based nanolasers. Furthermore, this configuration enables an exceptional control over the optical forces exerted on the nanoparticle. It expedites huge pushing or pulling actions, as well as a total suppression of the force in both far-field and near-field scenarios. These effects empower advanced paradigms in electromagnetic manipulation and microscopy. PMID:24718235

Liberal, Iigo; Ederra, Iigo; Gonzalo, Ramn; Ziolkowski, Richard W

2014-04-01

345

Large-scale magnetic field generation by randomly forced shearing waves.  

PubMed

A rigorous theory for the generation of a large-scale magnetic field by random nonhelically forced motions of a conducting fluid combined with a linear shear is presented in the analytically tractable limit of low magnetic Reynolds number (Rm) and weak shear. The dynamo is kinematic and due to fluctuations in the net (volume-averaged) electromotive force. This is a minimal proof-of-concept quasilinear calculation aiming to put the shear dynamo, a new effect recently found in numerical experiments, on a firm theoretical footing. Numerically observed scalings of the wave number and growth rate of the fastest-growing mode, previously not understood, are derived analytically. The simplicity of the model suggests that shear dynamo action may be a generic property of sheared magnetohydrodynamic turbulence. PMID:22243085

Heinemann, T; McWilliams, J C; Schekochihin, A A

2011-12-16

346

Vibration Suppression of a Helicopter Fuselage by Pendulum Absorbers : Rigid-Body Blades with Aerodynamic Excitation Force  

NASA Astrophysics Data System (ADS)

Currently, some kinds of helicopters use pendulum absorbers in order to reduce vibrations. Present pendulum absorbers are designed based on the antiresonance concept used in the linear theory. However, since the vibration amplitudes of the pendulum are not small, it is considered that the nonlinearity has influence on the vibration characteristics. Therefore, the best suppression cannot be attained by using the linear theory. In a helicopter, periodic forces act on the blades due to the influences of the air thrust. These periodic forces act on the blades with the frequency which is the integer multiple of the rotational speed of the rotor. Our previous study proposed a 2-degree-of-freedom (2DOF) model composed of a rotor blade and a pendulum absorber. The blade was considered as a rigid body and it was excited by giving a sinusoidal deflection at its end. The present paper proposes a 3DOF model that is more similar to the real helicopter, since the freedom of the fuselage is added and the periodic forces are applied to the blade by aerodynamic force. The vibration is analyzed considering the nonlinear characteristics. The resonance curves of rotor blades with pendulum absorbers are obtained analytically and experimentally. It is clarified that the most efficient condition is obtained when the natural frequency of the pendulum is a little bit different from the frequency of the external force. Various unique nonlinear characteristics, such as bifurcations, are also shown.

Nagasaka, Imao; Ishida, Yukio; Koyama, Takayuki; Fujimatsu, Naoki

347

The drag of a body with a proper magnetic field in supersonic flow of a partially ionized gas  

Microsoft Academic Search

Experimental results are presented on the effect of the proper magnetic field on the drag of bodies of a simple geometrical shape (e.g., a sphere, a cylinder, or a cone). The dependence of the drag on the magnetic field intensity is determined. The possibility of the efficient MHD braking of bodies in supersonic flow of a rarefied plasma is demonstrated.

V. V. Gubin; V. A. Shuvalov

1990-01-01

348

A uniqueness result for a simple force-free magnetic field submitted to a topological constraint  

Microsoft Academic Search

A proof is given of the following statement: if B is a smooth force-free magnetic field contained in a cylindrical domain of axis parallel to z and of star-shaped cross-section, and if B is topologically equivalent to the uniform field B0=B0z, then B=B0. In addition to being a very first step in the general study of the uniqueness of a

J. J. Aly

2005-01-01

349

Solid-State Nuclear Spin Quantum Computer Based on Magnetic Resonance Force Microscopy  

E-print Network

We propose a nuclear spin quantum computer based on magnetic resonance force microscopy (MRFM). It is shown that an MRFM single-electron spin measurement provides three essential requirements for quantum computation in solids: (a) preparation of the ground state, (b) one- and two- qubit quantum logic gates, and (c) a measurement of the final state. The proposed quantum computer can operate at temperatures up to 1K.

G. P. Berman; G. D. Doolen; P. C. Hammel; V. I. Tsifrinovich

1999-09-09

350

Stationary cantilever vibrations in the oscillating cantilever-driven adiabatic reversals -- magnetic resonance force microscopy technique  

E-print Network

We consider theoretically the novel technique in magnetic resonance force microscopy which is called ``oscillating cantilever-driven adiabatic reversals''. We present analytical and numerical analysis for the stationary cantilever vibrations in this technique. For reasonable values of parameters we estimate the resonant frequency shift as 6Hz per the Bohr magneton. We analyze also the regime of small oscillations of the paramagnetic moment near the transversal plane and the frequency shift of the damped cantilever vibrations.

G. P. Berman; D. I. Kamenev; V. I. Tsifrinovich

2002-03-04

351

Transient Dynamics in Magnetic Force Microscopy for a Single-Spin Measurement  

E-print Network

We analyze a single-spin measurement using a transient process in magnetic force microscopy (MFM) which could increase the maximum operating temperature by a factor of Q (the quality factor of the cantilever) in comparison with the static Stern-Gerlach effect. We obtain an exact solution of the master equation, which confirms this result. We also discuss the conditions required to create a macroscopic Schrodinger cat state in the cantilever.

G. P. Berman; F. Borgonovi; G. V. Lopez; V. I. Tsifrinovich

2002-10-01

352

Power law dependence of magnetic force vs. distance for a Y-Ba-Cu-O superconductor  

SciTech Connect

The repulsive force between a magnet and a superconducting Y-Ba-Cu-O disk has been measured as a function of the distance with emphasis on the exponent for F proportional to d{sup 11}. Two experimental protocols have been used: Initial application of field with subsequent transition to the superconducting state and vice versa. Several theoretical models are discussed in an attempt to explain the results.

Hecking, P.; Bacon, M. (Dept. of Physics, Thiel College, Greenville, PA (US))

1991-01-20

353

Imaging Carbon Nanotubes in High Performance Polymer Composites via Magnetic Force Microscope  

NASA Technical Reports Server (NTRS)

Application of carbon nanotubes as reinforcement in structural composites is dependent on the efficient dispersion of the nanotubes in a high performance polymer matrix. The characterization of such dispersion is limited by the lack of available tools to visualize the quality of the matrix/carbon nanotube interaction. The work reported herein demonstrates the use of magnetic force microscopy (MFM) as a promising technique for characterizing the dispersion of nanotubes in a high performance polymer matrix.

Lillehei, Peter T.; Park, Cheol; Rouse, Jason H.; Siochi, Emilie J.; Bushnell, Dennis M. (Technical Monitor)

2002-01-01

354

Magnetic force microscopy/current contrast imaging: A new technique for internal current probing of ICs  

SciTech Connect

This invited paper describes recently reported work on the application of magnetic force microscopy (MFM) to image currents in IC conductors [1]. A computer model for MFM imaging of IC currents and experimental results demonstrating the ability to determine current direction and magnitude with a resolution of {approximately} 1 mA dc and {approximately} 1 {mu}A ac are presented. The physics of MFM signal generation and applications to current imaging and measurement are described.

Campbell, A.N.; Cole, E.I. Jr.; Dodd, B.A.; Anderson, R.E.

1993-09-01

355

Quantitative Determination of the Adiabatic Condition Using Force-Detected Nuclear Magnetic Resonance  

E-print Network

The adiabatic condition governing cyclic adiabatic inversion of proton spins in a micron-sized ammonium chloride crystal was studied using room temperature nuclear magnetic resonance force microscopy. A systematic degradation of signal-to-noise was observed as the adiabatic condition became violated. A theory of adiabatic following applicable to cyclic adiabatic inversion is reviewed and implemented to quantitatively determine an adiabaticity threshold $(\\gamma H_1)^2/(\\omega_{osc}\\Omega) = 6.0$ from our experimental results.

Casey W. Miller; John T. Markert

2006-09-29

356

Energy expectation value of the two-pion-exchange three-body force in the triton  

NASA Astrophysics Data System (ADS)

The energetic shift caused by the two-pion-exchange three-nucleon force in the triton is estimated in first order perturbation theory. The triton wave function ? is gained through a Faddeev calculation using the Reid potential. Within the restricted presentation of ? strong cancellations between terms of the order of 1 MeV lead to an unimportant small effect. NUCLEAR STRUCTURE Energy expectation value of the two-pion-exchange three-nuclear force, Faddeev calculation.

Bmelburg, A.

1983-07-01

357

The Effective CSR Forces on an Energy-Chirped Bunch under Magnetic Compression  

SciTech Connect

Following our earlier formulation of the coherent synchrotron radiation (CSR) effect on bunch dynamics in magnetic bends, here we investigate the behavior of the effective CSR forces for an energy-chirped Gaussian bunch in the bending plane around full compression, with special care being taken in the incorporation of the retardation relation. Our results show clearly a delayed response of the CSR forces to the compression or lengthening of the bunch length. In addition, around full compression, our results reveal sensitivity of the effective CSR forces on the particles' transverse position, as a consequence of the geometry of particle interaction and retardation in this regime. These results can serve as benchmarks to the numerical simulation of the CSR effects.

Rui Li

2007-06-25

358

Hypervelocity impacts and magnetization of small bodies in the Solar System  

NASA Technical Reports Server (NTRS)

The observed magnetism of asteroids such as Gaspra and Ida (and other small bodies in the solar system including the Moon and meteorites) may have resulted from an impact-induced shock wave producing a thermodynamic state in which iron-nickel alloy, dispersed in a silicate matrix, is driven from the usual low-temperature, low-pressure, alpha, kaemacite, phase to the paramagnetic, epsilon (hcp), phase. The magnetization was acquired upon rarefaction and reentry into the ferromagnetic, alpha, structure. The degree of remagnetization depends on the strength of the ambient field, which may have been associated with a Solar-System-wide magnetic field. A transient field induced by the impact event itself may have resulted in a significant, or possibly, even a dominant contribution, as well. The scaling law of Housen et al. (Housen, K. R., R. M. Schmidt, and K. A. Holsapple 1991) for catastrophic asteroid impact disaggregation imposes a constraint on the degree to which small planetary bodies may be magnetized and yet survive fragmentation by the same event. Our modeling results show it is possible that Ida was magnetized when a large impact fractured a 125 +/- 22-km-radius protoasteroid to form the Koronis family. Similarly, we calculate that Gaspra could be a magnetized fragment of a 45 +/- 15 km-radius protoasteroid.

Chen, Guangqing; Ahrens, Thomas J.; Hide, Raymond

1995-01-01

359

Solid-state nuclear-spin quantum computer based on magnetic resonance force microscopy G. P. Berman and G. D. Doolen  

E-print Network

Solid-state nuclear-spin quantum computer based on magnetic resonance force microscopy G. P. Berman September 1999 We propose a nuclear-spin quantum computer based on magnetic resonance force microscopy MRFM for a small number of spins.6­8 Magnetic resonance force microscopy MRFM has ma- tured over the past few years

Hammel, P. Chris

360

Geometry of halo and Lissajous orbits in the circular restricted three-body problem with drag forces  

NASA Astrophysics Data System (ADS)

In this paper, we determine the effect of radiation pressure, Poynting-Robertson drag and solar wind drag on the Sun-(Earth-Moon) restricted three-body problem. Here, we take the larger body of the Sun as a larger primary, and the Earth+Moon as a smaller primary. With the help of the perturbation technique, we find the Lagrangian points, and see that the collinear points deviate from the axis joining the primaries, whereas the triangular points remain unchanged in their configuration. We also find that Lagrangian points move towards the Sun when radiation pressure increases. We have also analysed the stability of the triangular equilibrium points and have found that they are unstable because of the drag forces. Moreover, we have computed the halo orbits in the third-order approximation using the Lindstedt-Poincar method and have found the effect of the drag forces. According to this prevalence, the Sun-(Earth-Moon) model is used to design the trajectory for spacecraft travelling under drag forces.

Pal, Ashok Kumar; Kushvah, Badam Singh

2015-01-01

361

Development of a magnetic sensing device for tooth displacement under orthodontic forces.  

PubMed

We have developed a system for measuring tooth displacement from orthodontic force. Eight small magnetic sensors and a magnet are combined to measure three-dimensional displacement. Sensors, arranged cubically in the three planes of space, are placed in the mouth and fixed to the posterior teeth by a splint. A magnet is placed in the center of the eight sensors and attached to a front tooth that is subjected to orthodontic force. Sensors detect the magnet's movement as target tooth displacement. The system was designed to achieve displacement resolution of 1 microm. The mean percentage of measurement errors was determined to be less than 1% in a 600-cubic-microm volume from calibration. The system was tested clinically on human teeth. Although the oral environment, with high temperature and humidity, was not agreeable with the sensors, this system was stable and accurate enough for quantitative measurement of tooth displacement. The advantage of this system is the ability to detect tooth trajectories by decomposing displacement into translation and rotation and to determine the position of the center of rotation from these parameters. PMID:11327504

Yoshida, N; Koga, Y; Saimoto, A; Ishimatsu, T; Yamada, Y; Kobayashi, K

2001-03-01

362

A Method for Embedding Circular Force-Free Flux Ropes in Potential Magnetic Fields  

NASA Astrophysics Data System (ADS)

We propose a method for constructing approximate force-free equilibria in pre-eruptive configurations that locally are a bipolar-type potential magnetic field with a thin force-free flux rope embedded inside it. The flux rope is assumed to have a circular-arc axis, circular cross-section, and electric current that is either concentrated in a thin layer at the boundary of the rope or smoothly distributed across it with a maximum of the current density at the center.The entire solution is described in terms of the magnetic vector potential in order to facilitate the implementation of the method in numerical magnetohydrodynamic (MHD) codes that evolve the vector potential rather than the magnetic field itself. The parameters of the flux rope can be chosen so that its subsequent MHD relaxation under photospheric line-tied boundary conditions leads to nearly exact numerical equilibria. To show the capabilities of our method, we apply it to several cases with different ambient magnetic fields and internal flux-rope structures. These examples demonstrate that the proposed method is a useful tool for initializing data-driven simulations of solar eruptions.

Titov, Viacheslav; Torok, Tibor; Mikic, Zoran; Linker, Jon A.

2014-06-01

363

Molecular dynamics simulation of Lorentz force microscopy in magnetic nano-disks  

NASA Astrophysics Data System (ADS)

In this paper, we present a molecular dynamics simulation to model the Lorentz force microscopy experiment. Experimentally, this technique consists in the scattering of electrons by magnetic structures in surfaces and gases. Here, we will explore the behavior of electrons colliding with nano-magnetic disks. The computational molecular dynamics experiment allows us to follow the trajectory of individual electrons all along the experiment. In order to compare our results with the experimental one reported in literature, we model the experimental electron detectors in a simplified way: a photo-sensitive screen is simulated in such way that it counts the number of electrons that collide at a certain position. The information is organized to give in grey scale the image information about the magnetic properties of the structure in the target. Computationally, the sensor is modeled as a square matrix in which we count how many electrons collide at each specific point after being scattered by the magnetic structure. We have used several configurations of the magnetic nano-disks to understand the behavior of the scattered electrons, changing the orientation direction of the magnetic moments in the nano-disk in several ways. Our results match very well with the experiments, showing that this simulation can become a powerful technique to help to interpret experimental results.

Dias, R. A.; Mello, E. P.; Coura, P. Z.; Leonel, S. A.; Maciel, I. O.; Toscano, D.; Rocha, J. C. S.; Costa, B. V.

2013-04-01

364

ON THE STABILITY OF NON-FORCE-FREE MAGNETIC EQUILIBRIA IN STARS  

SciTech Connect

The existence of stable magnetic configurations in white dwarfs, neutron stars, and various non-convective stellar regions is now well recognized. It has recently been shown numerically that various families of equilibria, including axisymmetric mixed poloidal-toroidal configurations, are stable. Here we test the stability of an analytically derived non-force-free magnetic equilibrium resulting from an initial relaxation (self-organization) process, using three-dimensional magnetohydrodynamic simulations: the obtained mixed configuration is compared with the dynamical evolution of its purely poloidal and purely toroidal components, both known to be unstable. The mixed equilibrium shows no sign of instability under white noise perturbations. This configuration therefore provides a good description of magnetic equilibrium topology inside non-convective stellar objects and will be useful to initialize magneto-rotational transport in stellar evolution codes and in multi-dimensional magnetohydrodynamic simulations.

Duez, V.; Braithwaite, J. [Argelander Institut fuer Astronomie, Universitaet Bonn, Auf dem Huegel 71, D-53111 Bonn (Germany); Mathis, S., E-mail: vduez@astro.uni-bonn.d [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, IRFU/SAp Centre de Saclay, F-91191 Gif-sur-Yvette (France)

2010-11-20

365

Temporal and preparation effects in the magnetic nanoparticles of Apis mellifera body parts  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles in the Apis mellifera abdomens are well accepted as involved in their magnetoreception mechanism. The effects of sample preparation on the time evolution of magnetic particles in the honeybee body parts (antennae, head, thorax and abdomen) were investigated by Ferromagnetic Resonance (FMR) at room temperature (RT), for about 100 days. Three preparations were tested: (a) washed with water (WT); (b) as (a), kept in glutaraldehyde 2.5% in 0.1 M cacodylate buffer (pH 7.4) for 24 h and washed with cacodylate buffer (C); (c) as (a), kept in glutaraldehyde 2.5% for 24 h and washed with glutaraldehyde 2.5% in cacodylate buffer (GLC). The four body parts of young and adult worker presented magnetic nanoparticles. The Mn 2+ lines are observed except for the antennae spectra. The high field (HF) and low field (LF) components previously observed in the spectra of social insects, are confirmed in these spectra. The HF line is present in all spectra while the LF is easily observed in the spectra of the young bee and it appears as a baseline shift in spectra of some adult parts. The HF intensity of the abdomen is commonly one order of magnitude larger than any other body parts. This is the first systematic study on the conservation of magnetic material in all body parts of bees. The results show that the time evolution of the spectra depends on the body part, conserving solution and bee age. Further measurements are necessary to understand these effects and extend it to other social insects.

Chambarelli, L. L.; Pinho, M. A.; Abraado, L. G.; Esquivel, D. M. S.; Wajnberg, E.

366

A continuum body force sensor designed for flexible surgical robotics devices.  

PubMed

This paper presents a novel three-axis force sensor based on optical photo interrupters and integrated with the robot arm STIFF-FLOP (STIFFness controllable Flexible and Learnable Manipulator for Surgical Operations) to measure external interacting forces and torques. The ring-shape bio-compatible sensor presented here embeds the distributed actuation and sensing system of the STIFF-FLOP manipulator and is applicable to the geometry of its structure as well to the structure of any other similar soft robotic manipulator. Design and calibration procedures of the device are introduced: experimental results allow defining a stiffness sensor matrix for real-time estimation of force and torque components and confirm the usefulness of the proposed optical sensing approach. PMID:25570797

Yohan Noh; Secco, Emanuele Lindo; Sareh, Sina; Wurdemann, Helge; Faragasso, Angela; Back, Junghwan; Hongbin Liu; Sklar, Elizabeth; Althoefer, Kaspar

2014-08-01

367

Magnetic susceptibility of the body-centred orthorhombic La2CuO4 system  

NASA Astrophysics Data System (ADS)

A model Hamiltonian representing the Cu spins in La2CuO4 in its low-temperature body-centred orthorhombic phase, that includes both spin-orbit-generated Dzyaloshinskii-Moriya interactions and interplanar exchange, is examined within the RPA utilizing a Tyablikov decoupling of various high-order Green's functions. The magnetic susceptibility is evaluated as a function of temperature and the parameters quantifying these interactions, and compared to recently obtained experimental data of Lavrov, Ando, and collaborators. An effective Hamiltonian corresponding to a simple tetragonal structure is shown to reproduce both the magnon spectra and the susceptibility of the more complicated body-centred orthorhombic model.

Tabunshchyk, Kyrylo V.; Gooding, R. J.

2005-10-01

368

Magnetism on the angrite parent body and the early differentiation of planetesimals.  

PubMed

Angrites are among the oldest known pristine basaltic meteorites and record the earliest stages of planet formation and differentiation. Our paleomagnetic analysis of three angrites found that they record a past magnetic field of approximately 10 microteslas on the angrite parent body extending from 4564 to at least 4558 million years ago. Because the angrite paleomagnetic record extends beyond the expected lifetime of the early circumstellar disk, these paleofields were probably generated internally on the angrite parent body, possibly by an early dynamo in a rapidly formed metallic core. PMID:18974346

Weiss, Benjamin P; Berdahl, James S; Elkins-Tanton, Linda; Stanley, Sabine; Lima, Eduardo A; Carporzen, Laurent

2008-10-31

369

Numerical simulations of mass outflows driven from accretion disks by radiation and magnetic forces  

E-print Network

We study the two-dimensional, time-dependent MHD of radiation-driven winds from luminous accretion disks initially threaded by a purely axial magnetic field. The radiation force is mediated primarily by spectral lines. We use ideal MHD to compute the evolution of Keplerian disks, varying the magnetic field strengths and the luminosity of the disk, the central accreting object or both. We find that the magnetic fields very quickly start deviating from purely axial due to the magnetorotational instability. This leads to fast growth of the toroidal magnetic field. As a result the toroidal field dominates over the poloidal field above the disk and the gradient of the former drives a slow and dense disk outflow, which conserves specific angular momentum. Depending on the strength of the magnetic field relative to the system luminosity the disk wind can be radiation- or MHD driven. The pure radiation-driven wind consists of a dense, slow outflow that is bounded on the polar side by a high-velocity stream. The mass-loss rate is mostly due to the fast stream. As the magnetic field strength increases first the slow part of the flow is affected, namely it becomes denser and slightly faster and begins to dominate the mass-loss rate. In very strong magnetic field or pure MHD cases, the wind consists of only a dense, slow outflow without the presence of the distinctive fast stream so typical to pure radiation-driven winds. Our simulations indicate that winds launched by the magnetic fields are likely to remain dominated by the fields downstream because of their relatively high densities.

D. Proga

2002-10-29

370

Mechanism of the combustion of condensed systems with solid admixtures in a field of body forces  

Microsoft Academic Search

of the agglomerates under the action of centrifugal forces at a number of points on the surface [7], which results in an intensification of the pyrolysis of the propellant. The increase in the combustion rate of aluminized propellants when the acceleration is increased is associated with an enhancement of the agglomeration of the aluminum particles [8]. In order to explain

V. I. Yukhvid; . I. Maksimov; A. G. Merzhanov; B. I. Khaikin; V. S. Kozlov

1973-01-01

371

Laminar Forced Convection Heat Transfer From Isothermal Bodies With Unity Aspect Ratio in Coaxial Air Flow  

Microsoft Academic Search

In this article a semianalytical approach is employed to obtain dimensionless heat transfer correlations for forced convection over three geometriessphere, cone, and cylinder with unity aspect ratio in laminar axial air flow. The comparison of the present results for a sphere with the previous work shows very good agreement. For example, the average difference between the results of the present

Yaser Hadad; Khosrow Jafarpur

2012-01-01

372

Measurements of magnetism-related forces and torque moments affecting medical instruments, implants, and foreign objects during magnetic resonance imaging at all degrees of freedom.  

PubMed

We designed a novel force/torque moment transducer with six degrees of freedom. This new sensor is used for measuring the forces and torque moments exerted by static magnetic resonance imaging (MRI) fields on various medical implants, instruments, and ballistic shell fragments. To determine the location of strongest effect the inhomogeneity of the magnetic field between the entrance of the MRI-tube (portal), and the imaging section was measured. Force and torque moments of a sample of 45 objects were measured at two positions, at the portal, and in the center of the imaging section. We classified the objects regarding to the magnetism-related forces measured in the homogeneous part of the MRI tube. About one-third of the objects was non- or weakly magnetic, one-third moderately, and the last third was strongly magnetic. Forces within the inhomogeneous area of the magnetic field at the entrance part of the tube were up to half a magnitude larger than forces inside the homogeneous imaging section. Here the greatest potential risks to patients might occur. PMID:8798170

Planert, J; Modler, H; Vosshenrich, R

1996-06-01

373

Three-body force in bound trinucleon system with explicit. delta. (1236) components  

Microsoft Academic Search

It is shown that the sum of all time-ordered diagrams which contribute to the two-meson-exchange three-body potential due to the excitation of one nucleon into a ..delta.. isobar can be reproduced by the second order interaction of the nonrelativistic one-meson-exchange transition potential in the coupled channels approach.

Shin Yang

1981-01-01

374

Nuggets of Mechanical Engineering - Revisit of the Free-Body Diagram Analysis and Force Flow Concept  

Microsoft Academic Search

Several key concepts in mechanical engineering, such as free-body diagram analysis, fo rce flow concept, stiffness network, observing coordina tes for kinematics, stress analysis, electric circuit analy sis, tolerancing, etc, often present great difficulties to students. In this paper, the author starts an atte mpt to revisit some fundamentals. It will be called nugge ts of mechanical engineering. Although no

Jay F. Tu

375

Clinical examination or whole-body magnetic resonance imaging: the Holy Grail of spondyloarthritis imaging  

PubMed Central

Whole-body magnetic resonance imaging allows acquisition of diagnostic images in the shortest scan time, leading to better patient compliance and artifact-free images. Methods of clinical examination of the anterior chest wall joints vary between physician groups and consideration of the rules of rib motion is suggested. The type of joint and its synovial lining may also aid imaging/clinical correlation. This well-written study by experts in the field with a standardized design and methodology allows good scientific analysis and suggests the advantages of whole-body magnetic resonance imaging in anterior chest wall imaging. Selection of clinical examination criteria and specific joints may have had an influence on the study results and the lack of association reported. PMID:22380535

2012-01-01

376

Intraoral conversion of occlusal force to electricity and magnetism by biting of piezoelectric elements.  

PubMed

Very weak electrical, magnetic and ultrasound signal stimulations are known to promote the formation, metabolism, restoration and stability of bone and surrounding tissues after treatment and operations. We have therefore investigated the possibility of intraoral generation of electricity and magnetism by occlusal force in an in vitro study. Biting bimorph piezoelectric elements with lead zirconate titanate (PZT) using dental models generated appropriate magnetism for bone formation, i. e. 0.5-0.6 gauss, and lower electric currents and higher voltages, i. e. 2.0-6.0 ?A at 10-22 V (appropriate levels are 30 ?A and 1.25 V), as observed by a universal testing machine. The electric currents and voltages could be changed using amplifier circuits. These results show that intraoral generation of electricity and magnetism is possible and could provide post-operative stabilization and activation of treated areas of bone and the surrounding tissues directly and/or indirectly by electrical, magnetic and ultrasound stimulation, which could accelerate healing. PMID:23207207

Kameda, Takashi; Ohkuma, Kazuo; Sano, Natsuki; Ogura, Hideo; Terada, Kazuto

2012-01-01

377

Effects of a Circulating-water Garment and Forced-air Warming on Body Heat Content and Core Temperature  

PubMed Central

Background: Forced-air warming is sometimes unable to maintain perioperative normothermia. We therefore compared heat transfer, regional heat distribution, and core rewarming of forced-air warming with a novel circulating-water garment. Methods: Nine volunteers were each evaluated on two randomly ordered study days. They were anesthetized and cooled to a core temperature near 34C. The volunteers were subsequently warmed for 2.5 hours with either a circulating-water garment or forced-air cover. Overall, heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Average arm and leg (peripheral) tissue temperatures were determined from 18 intramuscular needle thermocouples, 15 skin thermal flux transducers, and deep arm and foot thermometers. Results: Heat production (? 60 kcal/h) and loss (?45 kcal/h) were similar with each treatment before warming. The increase in heat transfer across anterior portions of the skin surface was similar with each warming system (?65 kcal/h). Forced-air warming had no effect on posterior heat transfer whereas circulating-water transferred 21 9 kcal/h through the posterior skin surface after a half hour of warming. Over 2.5 h, circulating-water thus increased body heat content 56% more than forced air. Core temperatures thus increased faster than with circulating water than forced air, especially during the first hour, with the result that core temperature was 1.1 0.7C greater after 2.5 h (P < 0.001). Peripheral tissue heat content increased twice as much as core heat content with each device, but the core-to-peripheral tissue temperature gradient remained positive throughout the study. Conclusions: The circulating-water system transferred more heat than forced air, with the difference resulting largely from posterior heating. Circulating water rewarmed patients 0.4C/h faster than forced air. A substantial peripheral-to-core tissue-temperature gradient with each device indicated that peripheral tissues insulated the core, thus slowing heat transfer. PMID:15114200

Taguchi, Akiko; Ratnaraj, Jebadurai; Kabon, Barbara; Sharma, Neeru; Lenhardt, Rainer; Sessler, Daniel I.

2005-01-01

378

Measurement of the dynamical dipolar coupling in a pair of magnetic nano-disks using a Ferromagnetic Resonance Force Microscope  

E-print Network

by the magnetic tip of a ferromagnetic resonance force microscope (f-MRFM) to continuously tune and detune a Ferromagnetic Resonance Force Microscope B. Pigeau, C. Hahn, G. de Loubens, V. V. Naletov, and O. Klein Service the relative resonance frequencies between two adjacent nano-objects. This reveals the anti

Paris-Sud XI, Université de

379

Lorentz Force on Sodium and Chlorine Ions in a Salt Water Solution Flow under a Transverse Magnetic Field  

ERIC Educational Resources Information Center

It is shown that, by applying elementary concepts in electromagnetism and electrochemistry to a system consisting of salt water flowing in a thin rectangular pipe at an average velocity v[subscript A] under the influence of a transverse magnetic field B[subscript 0], an electromotive force generator can be conceived. In fact, the Lorentz force

De Luca, R.

2009-01-01

380

Rigid-body rotation of an electron cloud in divergent magnetic fields  

SciTech Connect

For a given voltage across a divergent poloidal magnetic field, two electric potential distributions, each supported by a rigid-rotor electron cloud rotating with a different frequency, are found analytically. The two rotation frequencies correspond to the slow and fast rotation frequencies known in uniform plasma. Due to the centrifugal force, the equipotential surfaces, that correspond to the two electric potential distributions, diverge more than the magnetic surfaces do, the equipotential surfaces in the fast mode diverge largely in particular. The departure of the equipotential surfaces from the magnetic field surfaces may have a significant focusing effect on the ions accelerated by the electric field. The focusing effect could be important for laboratory plasma accelerators as well as for collimation of astrophysical jets.

Fruchtman, A. [H.I.T.Holon Institute of Technology, Holon 58102 (Israel)] [H.I.T.Holon Institute of Technology, Holon 58102 (Israel); Gueroult, R.; Fisch, N. J. [Princeton Plasma Physics Laboratory, Princeton University, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton University, New Jersey 08543 (United States)

2013-07-15

381

Isotropic contact forces in arbitrary representation: Heterogeneous few-body problems and low dimensions  

Microsoft Academic Search

The Bethe-Peierls asymptotic approach which models pairwise short-range forces by contact conditions is introduced in arbitrary representation for spatial dimensions less than or equal to 3. The formalism is applied in various situations and emphasis is put on the momentum representation. In the presence of a transverse harmonic confinement, dimensional reduction toward two-dimensional (2D) or one-dimensional (1D) physics is derived

Ludovic Pricoupenko

2011-01-01

382

Computations of fully nonlinear three-dimensional wave wave and wave body interactions. Part 2. Nonlinear waves and forces on a body  

NASA Astrophysics Data System (ADS)

The mixed-Eulerian Lagrangian method using high-order boundary elements, described in Xue et al. (2001) for the simulation of fully nonlinear three-dimensional wave wave and wave body interactions, is here extended and applied to the study of two nonlinear three-dimensional wave body problems: (a) the development of bow waves on an advancing ship; and (b) the steep wave diffraction and nonlinear high-harmonic loads on a surface-piercing vertical cylinder. For (a), we obtain convergent steady-state bow wave profiles for a flared wedge, and the Wigley and Series 60 hulls. We compare our predictions with experimental measurements and find good agreement. It is shown that upstream influence, typically not accounted for in quasi-two-dimensional theory, plays an important role in bow wave prediction even for fine bows. For (b), the primary interest is in the higher-harmonic ringing excitations observed and quantified in experiments. From simulations, we obtain fully nonlinear steady-state force histories on the cylinder in incident Stokes waves. Fourier analysis of such histories provides accurate predictions of harmonic loads for which excellent comparisons to experiments are obtained even at third order. This confirms that ringing excitations are directly a result of nonlinear wave diffraction.

Liu, Yuming; Xue, Ming; Yue, Dick K. P.

2001-07-01

383

Design of a self-aligned, wide temperature range (300 mK-300 K) atomic force microscope/magnetic force microscope with 10 nm magnetic force microscope resolution  

NASA Astrophysics Data System (ADS)

We describe the design of a wide temperature range (300 mK-300 K) atomic force microscope/magnetic force microscope with a self-aligned fibre-cantilever mechanism. An alignment chip with alignment groves and a special mechanical design are used to eliminate tedious and time consuming fibre-cantilever alignment procedure for the entire temperature range. A low noise, Michelson fibre interferometer was integrated into the system for measuring deflection of the cantilever. The spectral noise density of the system was measured to be 12 fm/?Hz at 4.2 K at 3 mW incident optical power. Abrikosov vortices in BSCCO(2212) single crystal sample and a high density hard disk sample were imaged at 10 nm resolution to demonstrate the performance of the system.

Karc?, zgr; Dede, Mnir; Oral, Ahmet

2014-10-01

384

Non-linear evolution of tidally forced inertial waves in rotating fluid bodies  

NASA Astrophysics Data System (ADS)

We perform one of the first studies into the non-linear evolution of tidally excited inertial waves in a uniformly rotating fluid body, exploring a simplified model of the fluid envelope of a planet (or the convective envelope of a solar-type star) subject to the gravitational tidal perturbations of an orbiting companion. Our model contains a perfectly rigid spherical core, which is surrounded by an envelope of incompressible uniform density fluid. The corresponding linear problem was studied in previous papers which this work extends into the non-linear regime, at moderate Ekman numbers (the ratio of viscous to Coriolis accelerations). By performing high-resolution numerical simulations, using a combination of pseudo-spectral and spectral element methods, we investigate the effects of non-linearities, which lead to time-dependence of the flow and the corresponding dissipation rate. Angular momentum is deposited non-uniformly, leading to the generation of significant differential rotation in the initially uniformly rotating fluid, i.e. the body does not evolve towards synchronism as a simple solid body rotator. This differential rotation modifies the properties of tidally excited inertial waves, changes the dissipative properties of the flow and eventually becomes unstable to a secondary shear instability provided that the Ekman number is sufficiently small. Our main result is that the inclusion of non-linearities eventually modifies the flow and the resulting dissipation from what linear calculations would predict, which has important implications for tidal dissipation in fluid bodies. We finally discuss some limitations of our simplified model, and propose avenues for future research to better understand the tidal evolution of rotating planets and stars.

Favier, B.; Barker, A. J.; Baruteau, C.; Ogilvie, G. I.

2014-03-01

385

Baseband Detection of Bistatic Electron Spin Signals in Magnetic Resonance Force Microscopy (MRFM)  

E-print Network

In single spin Magnetic Resonance Force Microscopy (MRFM), the objective is to detect the presence of an electron (or nuclear) spin in a sample volume by measuring spin-induced attonewton forces using a micromachined cantilever. In the OSCAR method of single spin MRFM, the spins are manipulated by an external rf field to produce small periodic deviations in the resonant frequency of the cantilever. These deviations can be detected by frequency demodulation followed by conventional amplitude or energy detection. In this paper, we present an alternative to these detection methods, based on optimal detection theory and Gibbs sampling. On the basis of simulations, we show that our detector outperforms the conventional amplitude and energy detectors for realistic MRFM operating conditions. For example, to achieve a 10% false alarm rate and an 80% correct detection rate our detector has an 8 dB SNR advantage as compared with the conventional amplitude or energy detectors. Furthermore, at these detection rates it co...

Yip, C; Rugar, D; Fessler, J A; Yip, Chun-yu; Hero, Alfred O.; Rugar, Daniel; Fessler, Jeffrey A.

2003-01-01

386

Effect of radiation forces on disk accretion by weakly magnetic neutron stars  

NASA Technical Reports Server (NTRS)

Radiation forces are shown to be more important than general relativistic corrections to Newtonian gravitational forces in determining the motion of particles accreting onto a slowly rotating neutron star if the luminosity of the star is greater than about 1 percent of the Eddington critical luminosity (ECL). This is so even if the radius of the star is less than the radius of the innermost stable orbit. In particular, radiation drag causes matter accreting from a disk to lose angular momentum and spiral inward. At luminosities greater than about 0.2 ECL, a substantial fraction of the accreting matter can transfer most of its angular momentum and gravitational binding energy to the radiation field before reaching the stellar surface. These results have important implications for the X-ray spectra, time variability, and spin evolution of neutron stars with very weak magnetic fields and the prospects for detecting general relativistic effects near such stars.

Miller, M. C.; Lamb, Frederick K.

1993-01-01

387

Asymptotic forms for the energy of force-free magnetic field ion figurations of translational symmetry  

NASA Technical Reports Server (NTRS)

It is known from computer calculations that if a force-free magnetic field configuration is stressed progressively by footpoint displacements, the configuration expands and approaches the open configuration with the same surface flux distribution and the energy of the field increases progressively. For configurations of translationalsymmetry, it has been found empirically that the energy tends asymptotically to a certain functional form. It is here shown that analysis of a simple model of the asymptotic form of force-free fields of translational symmetry leads to and therefore justifies this functional form. According to this model, the field evolves in a well-behaved manner with no indication of instability or loss of equilibrium.

Sturrock, P. A.; Antiochos, S. K.; Klinchuk, J. A.; Roumeliotis, G.

1994-01-01

388

Computational unsteady forced convection over a stretching sheet with magnetic and radiative physical effects to the fluid flow field  

Microsoft Academic Search

A heat transfer for steady two-dimensional forced convection with magnetic hydrodynamic flow (MHD) with radiative effect of an incompressible fluid over an unsteady thermal forming stretching sheet has been studied. The parameters M and R which are used to represent the dominance of the magnetic effect and radiative effect have been presented in governing equations. The similar transformation and an

Kai-Long Hsiao

2011-01-01

389

Method for locating a small magnetic object in the human body  

SciTech Connect

A piece of a thin acupuncture needle lodged under the right scapula of a patient could not be found in surgical procedures accompanied by studies of 30 standard x-ray images. To locate it, the authors mapped the magnetic-field component normal to a plane lying above the object, using a superconducting quantum interference device (SQUID). Assuming that the needle could be modeled as a magnetic dipole, the authors were able to infer its lateral position, depth, orientation, and magnetic moment. With this information, directed CT scans, high-resolution x-ray films, and the subsequent surgical removal of the needle proved that it could be located in the body with an accuracy of about three millimeters.

Kaufman, L.; Williamson, S.J.; Ilmoniemi, R.J.; Weinberg, H.; Boyd, A.D.

1988-02-29

390

Novel System for Bite-Force Sensing and Monitoring Based on Magnetic Near Field Communication  

PubMed Central

Intraoral devices for bite-force sensing have several applications in odontology and maxillofacial surgery, as bite-force measurements provide additional information to help understand the characteristics of bruxism disorders and can also be of help for the evaluation of post-surgical evolution and for comparison of alternative treatments. A new system for measuring human bite forces is proposed in this work. This system has future applications for the monitoring of bruxism events and as a complement for its conventional diagnosis. Bruxism is a pathology consisting of grinding or tight clenching of the upper and lower teeth, which leads to several problems such as lesions to the teeth, headaches, orofacial pain and important disorders of the temporomandibular joint. The prototype uses a magnetic field communication scheme similar to low-frequency radio frequency identification (RFID) technology (NFC). The reader generates a low-frequency magnetic field that is used as the information carrier and powers the sensor. The system is notable because it uses an intra-mouth passive sensor and an external interrogator, which remotely records and processes information regarding a patient's dental activity. This permits a quantitative assessment of bite-force, without requiring intra-mouth batteries, and can provide supplementary information to polysomnographic recordings, current most adequate early diagnostic method, so as to initiate corrective actions before irreversible dental wear appears. In addition to describing the system's operational principles and the manufacture of personalized prototypes, this report will also demonstrate the feasibility of the system and results from the first in vitro and in vivo trials. PMID:23112669

Lantada, Andres Diaz; Bris, Carlos Gonzlez; Morgado, Pilar Lafont; Maudes, Jess Sanz

2012-01-01

391

Novel system for bite-force sensing and monitoring based on magnetic near field communication.  

PubMed

Intraoral devices for bite-force sensing have several applications in odontology and maxillofacial surgery, as bite-force measurements provide additional information to help understand the characteristics of bruxism disorders and can also be of help for the evaluation of post-surgical evolution and for comparison of alternative treatments. A new system for measuring human bite forces is proposed in this work. This system has future applications for the monitoring of bruxism events and as a complement for its conventional diagnosis. Bruxism is a pathology consisting of grinding or tight clenching of the upper and lower teeth, which leads to several problems such as lesions to the teeth, headaches, orofacial pain and important disorders of the temporomandibular joint. The prototype uses a magnetic field communication scheme similar to low-frequency radio frequency identification (RFID) technology (NFC). The reader generates a low-frequency magnetic field that is used as the information carrier and powers the sensor. The system is notable because it uses an intra-mouth passive sensor and an external interrogator, which remotely records and processes information regarding a patient's dental activity. This permits a quantitative assessment of bite-force, without requiring intra-mouth batteries, and can provide supplementary information to polysomnographic recordings, current most adequate early diagnostic method, so as to initiate corrective actions before irreversible dental wear appears. In addition to describing the system's operational principles and the manufacture of personalized prototypes, this report will also demonstrate the feasibility of the system and results from the first in vitro and in vivo trials. PMID:23112669

Lantada, Andres Diaz; Bris, Carlos Gonzlez; Morgado, Pilar Lafont; Maudes, Jess Sanz

2012-01-01

392

A nonlinear eigenvalue problem for self-similar spherical force-free magnetic fields  

NASA Astrophysics Data System (ADS)

An axisymmetric force-free magnetic field B(r, ?) in spherical coordinates is defined by a function r sin ? B ? = Q ( A ) relating its azimuthal component to its poloidal flux-function A. The power law r sin ? B ? = a A | A | 1/ n, n a positive constant, admits separable fields with A = An/(?)rn, posing a nonlinear boundary-value problem for the constant parameter a as an eigenvalue and An(?) as its eigenfunction [B. C. Low and Y. Q Lou, Astrophys. J. 352, 343 (1990)]. A complete analysis is presented of the eigenvalue spectrum for a given n, providing a unified understanding of the eigenfunctions and the physical relationship between the field's degree of multi-polarity and rate of radial decay via the parameter n. These force-free fields, self-similar on spheres of constant r, have basic astrophysical applications. As explicit solutions they have, over the years, served as standard benchmarks for testing 3D numerical codes developed to compute general force-free fields in the solar corona. The study presented includes a set of illustrative multipolar field solutions to address the magnetohydrodynamics (MHD) issues underlying the observation that the solar corona has a statistical preference for negative and positive magnetic helicities in its northern and southern hemispheres, respectively; a hemispherical effect, unchanging as the Sun's global field reverses polarity in successive eleven-year cycles. Generalizing these force-free fields to the separable form B = H/(? ,?)rn+2 promises field solutions of even richer topological varieties but allowing for ?-dependence greatly complicates the governing equations that have remained intractable. The axisymmetric results obtained are discussed in relation to this generalization and the Parker Magnetostatic Theorem. The axisymmetric solutions are mathematically related to a family of 3D time-dependent ideal MHD solutions for a polytropic fluid of index ? = 4/3 as discussed in the Appendix.

Lerche, I.; Low, B. C.

2014-10-01

393

Solutions of the Helmholtz equation with boundary conditions for force-free magnetic fields  

NASA Technical Reports Server (NTRS)

It is shown that the solution, with one ignorable coordinate, for the Taylor minimum energy state (resulting in a force-free magnetic field) in either a straight cylindrical or a toroidal geometry with arbitrary cross section can be reduced to the solution of either an inhomogeneous Helmholtz equation or a Grad-Shafranov equation with simple boundary conditions. Standard Green's function theory is, therefore, applicable. Detailed solutions are presented for the Taylor state in toroidal and cylindrical domains having a rectangular cross section. The focus is on solutions corresponding to the continuous eigenvalue spectra. Singular behavior at 90 deg corners is explored in detail.

Rasband, S. N.; Turner, L.

1981-01-01

394

Quantum Dynamics of the Oscillating Cantilever-Driven Adiabatic Reversals in Magnetic Resonance Force Microscopy  

E-print Network

We simulated the quantum dynamics for magnetic resonance force microscopy (MRFM) in the oscillating cantilever-driven adiabatic reversals (OSCAR) technique. We estimated the frequency shift of the cantilever vibrations and demonstrated that this shift causes the formation of a Schrodinger cat state which has some similarities and differences from the conventional MRFM technique which uses cyclic adiabatic reversals of spins. The interaction of the cantilever with the environment is shown to quickly destroy the coherence between the two possible cantilever trajectories. We have shown that using partial adiabatic reversals, one can produce a significant increase in the OSCAR signal.

Berman, G P; Tsifrinovich, V I

2004-01-01

395

Quantum Dynamics of the Oscillating Cantilever-Driven Adiabatic Reversals in Magnetic Resonance Force Microscopy  

E-print Network

We simulated the quantum dynamics for magnetic resonance force microscopy (MRFM) in the oscillating cantilever-driven adiabatic reversals (OSCAR) technique. We estimated the frequency shift of the cantilever vibrations and demonstrated that this shift causes the formation of a Schrodinger cat state which has some similarities and differences from the conventional MRFM technique which uses cyclic adiabatic reversals of spins. The interaction of the cantilever with the environment is shown to quickly destroy the coherence between the two possible cantilever trajectories. We have shown that using partial adiabatic reversals, one can produce a significant increase in the OSCAR signal.

G. P. Berman; F. Borgonovi; V. I. Tsifrinovich

2003-06-16

396

The simulation of a propulsive jet and force measurement using a magnetically suspended wind tunnel model  

NASA Technical Reports Server (NTRS)

Models featuring the simulation of exhaust jets were developed for magnetic levitation in a wind tunnel. The exhaust gas was stored internally producing a discharge of sufficient duration to allow nominal steady state to be reached. The gas was stored in the form of compressed gas or a solid rocket propellant. Testing was performed with the levitated models although deficiencies prevented the detection of jet-induced aerodynamic effects. Difficulties with data reduction led to the development of a new force calibration technique, used in conjunction with an exhaust simulator and also in separate high incidence aerodynamic tests.

Garbutt, K. S.; Goodyer, M. J.

1994-01-01

397

Hard-sphere fluid adsorbed in an annular wedge: The depletion force of hard-body colloidal physics  

NASA Astrophysics Data System (ADS)

Many important issues of colloidal physics can be expressed in the context of inhomogeneous fluid phenomena. When two large colloids approach one another in solvent, they interact at least partly by the response of the solvent to finding itself adsorbed in the annular wedge formed between the two colloids. At shortest range, this fluid mediated interaction is known as the depletion force/interaction because solvent is squeezed out of the wedge when the colloids approach closer than the diameter of a solvent molecule. An equivalent situation arises when a single colloid approaches a substrate/wall. Accurate treatment of this interaction is essential for any theory developed to model the phase diagrams of homogeneous and inhomogeneous colloidal systems. The aim of our paper is a test of whether or not we possess sufficient knowledge of statistical mechanics that can be trusted when applied to systems of large size asymmetry and the depletion force in particular. When the colloid particles are much larger than a solvent diameter, the depletion force is dominated by the effective two-body interaction experienced by a pair of solvated colloids. This low concentration limit of the depletion force has therefore received considerable attention. One route, which can be rigorously based on statistical mechanical sum rules, leads to an analytic result for the depletion force when evaluated by a key theoretical tool of colloidal science known as the Derjaguin approximation. A rival approach has been based on the assumption that modern density functional theories (DFT) can be trusted for systems of large size asymmetry. Unfortunately, these two theoretical predictions differ qualitatively for hard sphere models, as soon as the solvent density is higher than about 2/3 that at freezing. Recent theoretical attempts to understand this dramatic disagreement have led to the proposal that the Derjaguin and DFT routes represent opposite limiting behavior, for very large size asymmetry and molecular sized mixtures, respectively. This proposal implies that nanocolloidal systems lie in between the two limits, so that the depletion force no longer scales linearly with the colloid radius. That is, by decreasing the size ratio from mesoscopic to molecular sized solutes, one moves smoothly between the Derjaguin and the DFT predictions for the depletion force scaled by the colloid radius. We describe the results of a simulation study designed specifically as a test of compatibility with this complex scenario. Grand canonical simulation procedures applied to hard-sphere fluid adsorbed in a series of annular wedges, representing the depletion regime of hard-body colloidal physics, confirm that neither the Derjaguin approximation, nor advanced formulations of DFT, apply at moderate to high solvent density when the geometry is appropriate to nanosized colloids. Our simulations also allow us to report structural characteristics of hard-body solvent adsorbed in hard annular wedges. Both these aspects are key ingredients in the proposal that unifies the disparate predictions, via the introduction of new physics. Our data are consistent with this proposed physics, although as yet limited to a single colloidal size asymmetry.

Herring, A. R.; Henderson, J. R.

2007-01-01

398

Hard-sphere fluid adsorbed in an annular wedge: the depletion force of hard-body colloidal physics.  

PubMed

Many important issues of colloidal physics can be expressed in the context of inhomogeneous fluid phenomena. When two large colloids approach one another in solvent, they interact at least partly by the response of the solvent to finding itself adsorbed in the annular wedge formed between the two colloids. At shortest range, this fluid mediated interaction is known as the depletion force/interaction because solvent is squeezed out of the wedge when the colloids approach closer than the diameter of a solvent molecule. An equivalent situation arises when a single colloid approaches a substrate/wall. Accurate treatment of this interaction is essential for any theory developed to model the phase diagrams of homogeneous and inhomogeneous colloidal systems. The aim of our paper is a test of whether or not we possess sufficient knowledge of statistical mechanics that can be trusted when applied to systems of large size asymmetry and the depletion force in particular. When the colloid particles are much larger than a solvent diameter, the depletion force is dominated by the effective two-body interaction experienced by a pair of solvated colloids. This low concentration limit of the depletion force has therefore received considerable attention. One route, which can be rigorously based on statistical mechanical sum rules, leads to an analytic result for the depletion force when evaluated by a key theoretical tool of colloidal science known as the Derjaguin approximation. A rival approach has been based on the assumption that modern density functional theories (DFT) can be trusted for systems of large size asymmetry. Unfortunately, these two theoretical predictions differ qualitatively for hard sphere models, as soon as the solvent density is higher than about 23 that at freezing. Recent theoretical attempts to understand this dramatic disagreement have led to the proposal that the Derjaguin and DFT routes represent opposite limiting behavior, for very large size asymmetry and molecular sized mixtures, respectively. This proposal implies that nanocolloidal systems lie in between the two limits, so that the depletion force no longer scales linearly with the colloid radius. That is, by decreasing the size ratio from mesoscopic to molecular sized solutes, one moves smoothly between the Derjaguin and the DFT predictions for the depletion force scaled by the colloid radius. We describe the results of a simulation study designed specifically as a test of compatibility with this complex scenario. Grand canonical simulation procedures applied to hard-sphere fluid adsorbed in a series of annular wedges, representing the depletion regime of hard-body colloidal physics, confirm that neither the Derjaguin approximation, nor advanced formulations of DFT, apply at moderate to high solvent density when the geometry is appropriate to nanosized colloids. Our simulations also allow us to report structural characteristics of hard-body solvent adsorbed in hard annular wedges. Both these aspects are key ingredients in the proposal that unifies the disparate predictions, via the introduction of new physics. Our data are consistent with this proposed physics, although as yet limited to a single colloidal size asymmetry. PMID:17358145

Herring, A R; Henderson, J R

2007-01-01

399

Quantum Measurement of a Single Spin using Magnetic Resonance Force Microscopy  

E-print Network

Single-spin detection is one of the important challenges facing the development of several new technologies, e.g. single-spin transistors and solid-state quantum computation. Magnetic resonance force microscopy with a cyclic adiabatic inversion, which utilizes a cantilever oscillations driven by a single spin, is a promising technique to solve this problem. We have studied the quantum dynamics of a single spin interacting with a quasiclassical cantilever. It was found that in a similar fashion to the Stern-Gerlach interferometer the quantum dynamics generates a quantum superposition of two quasiclassical trajectories of the cantilever which are related to the two spin projections on the direction of the effective magnetic field in the rotating reference frame. Our results show that quantum jumps will not prevent a single-spin measurement if the coupling between the cantilever vibrations and the spin is small in comparison with the amplitude of the radio-frequency external field.

G. P. Berman; F. Borgonovi; G. Chapline; S. A. Gurvitz; P. C. Hammel; D. V. Pelekhov; A. Suter; V. I. Tsifrinovich

2001-08-06

400

Measurement and calculation of levitation forces between magnets and granular superconductors  

NASA Technical Reports Server (NTRS)

Recent developments indicate that exploitation of the phenomenon of magnetic levitation may become one of the most important near-term applications of high-T(sub c) superconductivity. Because of this, the interaction between a strong permanent magnet(PM) and bulk high-T(sub c) superconductor (HTSC) is currently a subject of much interest. We have studied central features of the mechanics of PM-HTSC systems of simple geometries. Here we report experimental results for the components of the levitation force, their associated stiffness and mechanical ac-loss. To analyze the observed behavior a theoretical framework based on critical-state considerations is developed. It will be shown that all the mechanical properties can be explained consistently at a quantitative level wing a minimum of model parameters.

Johansen, T. H.; Bratsberg, H.; Baziljevich, M.; Hetland, P. O.; Riise, A. B.

1995-01-01

401

Equilibrium points and stability under effect of radiation and perturbing forces in the restricted problem of three oblate bodies  

NASA Astrophysics Data System (ADS)

This paper presents a generalized problem of the restricted three body studied in Abdul Raheem and Singh with the inclusion that the third body is an oblate spheroidal test particle of infinitesimally mass. The positions and stability of the equilibrium point of this problem is studied for a model in which the primaries is the binary system Struve 2398 (Gliese 725) in the constellation Draco; which consist of a pair of radiating oblate stars. It is seen that additional equilibrium points exist on the line collinear with the primaries, for some combined parameters of the problem. Hence, there can be up to five collinear equilibrium points. Two triangular points exist and depends on the oblateness of the participating bodies, radiation pressure of the primaries and a small perturbation in the centrifugal force. The stability analysis ensures that, the collinear equilibrium points are unstable in the linear sense while the triangular points are stable under certain conditions. Illustrative numerical exploration is given to indicate significant improvement of the problem in Abdul Raheem and Singh.

Singh, Jagadish; Haruna, Sunusi

2014-01-01

402

Changes in the nanoparticle aggregation rate due to the additional effect of electrostatic and magnetic forces on mass transport coefficients  

PubMed Central

The need may arise to be able to simulate the migration of groundwater nanoparticles through the ground. Transportation velocities of nanoparticles are different from that of water and depend on many processes that occur during migration. Unstable nanoparticles, such as zero-valent iron nanoparticles, are especially slowed down by aggregation between them. The aggregation occurs when attracting forces outweigh repulsive forces between the particles. In the case of iron nanoparticles that are used for remediation, magnetic forces between particles contribute to attractive forces and nanoparticles aggregate rapidly. This paper describes the addition of attractive magnetic forces and repulsive electrostatic forces between particles (by particle, we mean both single nanoparticles and created aggregates) into a basic model of aggregation which is commonly used. This model is created on the basis of the flow of particles in the proximity of observed particles that gives the rate of aggregation of the observed particle. By using a limit distance that has been described in our previous work, the flow of particles around one particle is observed in larger spacing between the particles. Attractive magnetic forces between particles draw the particles into closer proximity and result in aggregation. This model fits more closely with rapid aggregation which occurs between magnetic nanoparticles. PMID:23302651

2013-01-01

403

Analysis of adipose tissue distribution using whole-body magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Obesity is an increasing problem in the western world and triggers diseases like cancer, type two diabetes, and cardiovascular diseases. In recent years, magnetic resonance imaging (MRI) has become a clinically viable method to measure the amount and distribution of adipose tissue (AT) in the body. However, analysis of MRI images by manual segmentation is a tedious and time-consuming process. In this paper, we propose a semi-automatic method to quantify the amount of different AT types from whole-body MRI data with less user interaction. Initially, body fat is extracted by automatic thresholding. A statistical shape model of the abdomen is then used to differentiate between subcutaneous and visceral AT. Finally, fat in the bone marrow is removed using morphological operators. The proposed method was evaluated on 15 whole-body MRI images using manual segmentation as ground truth for adipose tissue. The resulting overlap for total AT was 93.7% +/- 5.5 with a volumetric difference of 7.3% +/- 6.4. Furthermore, we tested the robustness of the segmentation results with regard to the initial, interactively defined position of the shape model. In conclusion, the developed method proved suitable for the analysis of AT distribution from whole-body MRI data. For large studies, a fully automatic version of the segmentation procedure is expected in the near future.

Wald, Diana; Schwarz, Tobias; Dinkel, Julien; Delorme, Stefan; Teucher, Birgit; Kaaks, Rudolf; Meinzer, Hans-Peter; Heimann, Tobias

2011-03-01

404

Time Evolution of Force-Free Parameter and Free Magnetic Energy in Active Region NOAA 10365  

NASA Astrophysics Data System (ADS)

We describe the variation of the accumulated coronal helicity derived from the magnetic helicity flux through the photosphere in active region (AR) NOAA 10365, where several large flares and coronal mass ejections (CMEs) occurred. We used SOHO/MDI full-disk line-of-sight magnetograms to measure the helicity flux, and the integral of GOES X-ray flux as a proxy of the coronal energy variations due to flares or CMEs. Using the linear force-free field model, we transformed the accumulated helicity flux into a time sequence of the force-free parameter ? accounting for flares or CMEs via the proxy derived from GOES observations. This method can be used to derive the value of ? at different times during the AR evolution, and is a partial alternative to the commonly used match of field lines with EUV loops. By combining the accumulated helicity obtained from the observations with the linear force-free theory, we describe the main phases of the emergence process of the AR, and relate them temporally with the occurrence of flares or CMEs. Additionally, a comparison with the loop-matching method of fixing alpha at each time independently shows that the proposed method may be helpful in avoiding unrealistic or undetermined values of alpha that may originate from an insufficient quality of the image used to identify coronal loops at a given time. For the relative intensity of the considered events, the linear force-free field theory implies that there is a direct correlation between the released energy on the one hand and the product of the coronal helicity with the variation of ? due to the event on the other. Therefore, the higher the value of the accumulated coronal helicity, the smaller the force-free parameter variation required to produce the same decrease in the free energy during the CMEs.

Valori, G.; Romano, P.; Malanushenko, A.; Ermolli, I.; Giorgi, F.; Steed, K.; van Driel-Gesztelyi, L.; Zuccarello, F.; Malherbe, J.-M.

2015-02-01

405

Eruption triggering of giant magma bodies by internal versus external forcing: A rhyolite-MELTS study  

NASA Astrophysics Data System (ADS)

Silicic volcanism, particularly supereruptions, raises questions about the mechanisms by which magma bodies destabilize and erupt. Are external events necessary to initiate an eruption of a large silicic system, or is possible for internal processes (crystallization, volatile exsolution) to destabilize a system and drive it to erupt? If external triggers are critically important to prompting eruption, are all felsic magma bodies equally prone to erupt? To respond to these questions, we use rhyolite-MELTS (Gualda et al. 2012) to investigate the pre-eruptive chemical evolution and the resultant changes to physical properties of giant (super-eruptive) felsic magma bodies. Simulations are conducted using pumice and glass compositions from the Peach Spring (Southwestern USA) and the Bishop (California USA) Tuffs, two giant high-silica rhyolite deposits. In our simulations, we vary initial pressure (150-350 MPa in 50 MPa intervals), volatile content (initial water ranging from 1-7 wt. %), mode of crystallization (equilibrium vs. fractional), and rheology of the magma reservoir (isobaric vs. isochoric vs. transitional). We run simulations through as much of the crystallization interval as possible, but focus on the first ~50 wt. % crystallization, most relevant for volcanic systems. In all simulations, we observe near-invariant behavior when the system becomes saturated in quartz, two feldspars and a fluid phase, from which point crystallization is essentially isothermal. Prior to the near-invariant, crystallization leads to gradual changes in bulk properties (e.g., < 1% volume decrease over 50 C), which effectively results in modest pressure changes within the magma body (i.e., ~10 MPa). Upon reaching the near-invariant, the bulk properties change abruptly (e.g., > 5% volume increase in 0.1 C), causing significant overpressurization of the magma body. The magnitude of this overpressurization (i.e. 10s to 100s of MPa depending on system conditions) is sufficient to exceed the yield strength of the country rocks, effectively making eruption possible independent of any external triggers. Our simulations reveal that the Peach Spring and Bishop Tuff magmatic systems represent two contrasting types of behavior. In the Bishop case, only ~5-25 wt.% of crystallization over a short temperature interval (~30 C cooling) is needed to reach near-invariant behavior, making it plausible that crystallization led to eruption without external triggers. This is consistent with the lack of evidence for interaction of Bishop magma with mafic magmas. In the Peach Spring case, 30-70 wt. % crystallization over a much longer temperature interval (~60-130 C cooling) is needed for the system to reach the near-invariant. Given that Peach Spring pumice and fiamme are characterized by <30 wt. % crystals, it seems unlikely that crystallization alone led to eruption, suggesting the action of an external trigger in promoting eruption. This is consistent with evidence for significant heating and mush remobilization preserved in intracaldera Peach Spring rocks. Our results show that phase-equilibria constrains whether a magma system is likely to destabilize itself and erupt as a result of overpressurization by closed-system crystallization and volatile exsolution.

Carley, T. L.; Gualda, G. A.; Ghiorso, M. S.; Miller, C. F.

2012-12-01

406

Thin-foil magnetic force system for high-numerical-aperture microscopy J. K. Fisher, J. Cribb, and K. V. Desai  

E-print Network

Thin-foil magnetic force system for high-numerical-aperture microscopy J. K. Fisher, J. Cribb where high force and high-numerical-aperture NA microscopy must be combined. We have developed a magnetic manipulation system that is capable of applying forces in excess of 700 pN on a 1 m paramagnetic

407

A multipole accelerated desingularized method for computing nonlinear wave forces on bodies  

SciTech Connect

Nonlinear wave forces on offshore structures are investigated. The fluid motion is computed using an Euler-Lagrange time domain approach. Nonlinear free surface boundary conditions are stepped forward in time using an accurate and stable integration technique. The field equation with mixed boundary conditions that result at each time step are solved at N nodes using a desingularized boundary integral method with multipole acceleration. Multipole accelerated solutions require O(N) computational effort and computer storage while conventional solvers require O(N{sup 2}) effort and storage for an iterative solution and O(N{sup 3}) effort for direct inversion of the influence matrix. These methods are applied to the three dimensional problem of wave diffraction by a vertical cylinder.

Scorpio, S.M.; Beck, R.F. [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Naval Architecture and Marine Engineering

1996-12-31

408

Force-based many-body interatomic potential for ZrC  

NASA Astrophysics Data System (ADS)

A classical potential for ZrC is developed in the form of a modified second-moment approximation with emphasis on the strong directional dependence of the C-Zr interactions. The model has a minimal set of parameters, 4 for the pure metal and 6 for the cross interactions, which are fitted to the database of cohesive energies of B1-, B2-, and B3-ZrC, the heat of formation, and most importantly, the atomic force constants of B1-ZrC from first-principles calculations. The potential is then extensively tested against various physical properties, none of which were considered in the fitting. Finite temperature properties such as thermal expansion and melting point are in excellent agreement with experiments. We believe our model should be a good template for metallic ceramics.

Li, Ju; Liao, Dongyi; Yip, Sidney; Najafabadi, Reza; Ecker, Lynne

2003-06-01

409

A Lorentz force actuated magnetic field sensor with capacitive read-out  

NASA Astrophysics Data System (ADS)

We present a novel design of a resonant magnetic field sensor with capacitive read-out permitting wafer level production. The device consists of a single-crystal silicon cantilever manufactured from the device layer of an SOI wafer. Cantilevers represent a very simple structure with respect to manufacturing and function. On the top of the structure, a gold lead carries AC currents that generate alternating Lorentz forces in an external magnetic field. The free end oscillation of the actuated cantilever depends on the eigenfrequencies of the structure. Particularly, the specific design of a U-shaped structure provides a larger force-to-stiffness-ratio than standard cantilevers. The electrodes for detecting cantilever deflections are separately fabricated on a Pyrex glass-wafer. They form the counterpart to the lead on the freely vibrating planar structure. Both wafers are mounted on top of each other. A custom SU-8 bonding process on wafer level creates a gap which defines the equilibrium distance between sensing electrodes and the vibrating structure. Additionally to the capacitive read-out, the cantilever oscillation was simultaneously measured with laser Doppler vibrometry through proper windows in the SOI handle wafer. Advantages and disadvantages of the asynchronous capacitive measurement configuration are discussed quantitatively and presented by a comprehensive experimental characterization of the device under test.

Stifter, M.; Steiner, H.; Kainz, A.; Keplinger, F.; Hortschitz, W.; Sauter, T.

2013-05-01

410

Analysis and parallel implementation of a forced N-body problem  

NASA Astrophysics Data System (ADS)

The understanding of particle dynamics in N-body problems is of importance to many applications in astrophysics, molecular dynamics and cloud/plasma physics where the theoretical representation results in a coupled system of equations for a large number of entities. This paper concerns algorithms for solving a specific N-body problem, namely, a system of disturbance velocities for hydrodynamically interacting particles in a particle-laden turbulent flow. The system is derived from the improved superposition method of [1]. Targeting for scalable computations on petascale computers, we have carried out a thorough study of a parallel implementation of GMRes with different features, such as preconditioners, matrix-free and parallel sparse representation of the matrix through 1D and 2D spatial domain decompositions. Gauss-Seidel method is also studied as a reference iterative algorithm. The range of conditions for efficiency and failure of each method is discussed in detail. Through perturbation analysis, we have conducted a series of experiments to understand the effect of particle sizes, interaction symmetry, inter-particle distances and interaction truncation on the eigenvalues and normality of the linear system. For situations where the system is ill-conditioned, we introduce a restricted Schwarz type preconditioner. We verified the parallel efficiency of the preconditioner using 1D domain decomposition on a parallel machine. A benchmark problem of particle laden turbulence at 5123 resolution with 2106 particles is studied to understand the scalability of the proposed methods on parallel machines. We have developed a stable and highly scalable parallel solver with an affordable computational cost even for ill-conditioned systems through preconditioning. On 64 cores, using GMRes in 2D domain decomposition, we achieved a speed-up of 5.6x (relative to 1D domain decomposition on the same number of processors). Our complexity analysis showed that for large N-body problems, the proposed GMRes scheme scales well for moderate to large number of processors in current tera to petascale computers.

Torres, C. E.; Parishani, H.; Ayala, O.; Rossi, L. F.; Wang, L.-P.

2013-07-01

411

Boxfish swimming paradox resolved: forces by the flow of water around the body promote manoeuvrability.  

PubMed

The shape of the carapace protecting the body of boxfishes has been attributed an important hydrodynamic role in drag reduction and in providing automatic, flow-direction realignment and is therefore used in bioinspired design of cars. However, tight swimming-course stabilization is paradoxical given the frequent, high-performance manoeuvring that boxfishes display in their spatially complex, coral reef territories. Here, by performing flow-tank measurements of hydrodynamic drag and yaw moments together with computational fluid dynamics simulations, we reverse several assumptions about the hydrodynamic role of the boxfish carapace. Firstly, despite serving as a model system in aerodynamic design, drag-reduction performance was relatively low compared with more generalized fish morphologies. Secondly, the current theory of course stabilization owing to flow over the boxfish carapace was rejected, as destabilizing moments were found consistently. This solves the boxfish swimming paradox: destabilizing moments enhance manoeuvrability, which is in accordance with the ecological demands for efficient turning and tilting. PMID:25505133

Van Wassenbergh, S; van Manen, K; Marcroft, T A; Alfaro, M E; Stamhuis, E J

2015-02-01

412

Magnetically operated check valve  

NASA Technical Reports Server (NTRS)

A magnetically operated check valve is disclosed. The valve is comprised of a valve body and a movable poppet disposed therein. A magnet attracts the poppet to hold the valve shut until the force of fluid flow through the valve overcomes the magnetic attraction and moves the poppet to an unseated, open position. The poppet and magnet are configured and disposed to trap a magnetically attracted particulate and prevent it from flowing to a valve seating region.

Morris, Brian G. (inventor); Bozeman, Richard J., Jr. (inventor)

1994-01-01

413

COMPARISON OF FORCE-FREE CORONAL MAGNETIC FIELD MODELING USING VECTOR FIELDS FROM HINODE AND SOLAR DYNAMICS OBSERVATORY  

SciTech Connect

Photospheric magnetic vector maps from two different instruments are used to model the nonlinear force-free coronal magnetic field above an active region. We use vector maps inferred from polarization measurements of the Solar Dynamics Observatory/Helioseismic and Magnetic Imager (HMI) and the Solar Optical Telescope's Spectropolarimeter (SP) on board Hinode. Besides basing our model calculations on HMI data, we use both SP data of original resolution and scaled down to the resolution of HMI. This allows us to compare the model results based on data from different instruments and to investigate how a binning of high-resolution data affects the model outcome. The resulting three-dimensional magnetic fields are compared in terms of magnetic energy content and magnetic topology. We find stronger magnetic fields in the SP data, translating into a higher total magnetic energy of the SP models. The net Lorentz forces of the HMI and SP lower boundaries verify their force-free compatibility. We find substantial differences in the absolute estimates of the magnetic field energy but similar relative estimates, e.g., the fraction of excess energy and of the flux shared by distinct areas. The location and extension of neighboring connectivity domains differ and the SP model fields tend to be higher and more vertical. Hence, conclusions about the magnetic connectivity based on force-free field models are to be drawn with caution. We find that the deviations of the model solution when based on the lower-resolution SP data are small compared to the differences of the solutions based on data from different instruments.

Thalmann, J. K.; Tiwari, S. K.; Wiegelmann, T., E-mail: thalmann@mps.mpg.de [Max-Plank-Institut fuer Sonnensystemforschung, Max-Planck-Str. 2, D-37191 Katlenburg-Lindau (Germany)

2013-05-20

414

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

NASA Astrophysics Data System (ADS)

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

Dobrot?, Costin-Ionu?; Stancu, Alexandru

2015-01-01

415

Modeling of hysteretic behavior of the levitation force between superconductor and permanent magnet  

NASA Astrophysics Data System (ADS)

The hysteretic behavior of the levitation force between a permanent magnet and a melt-textured-growth YBCO bulk has been investigated under both zero-field cooling (ZFC) and field cooling (FC) processes. It is found that both in ZFC and FC measurements, the hysteresis loop for the first descent/ascent cycle of magnet is relatively larger than that for the second or third cycle, and the hysteresis loops for Cycle 2-4 have the same area. These results can be qualitatively understood in terms of the critical state model. To describe these experimental results, we develop an updated frozen-image model, which is obtained by modifying the change rules of the vertical movement image in the advanced frozen-image model proposed by Yang et al. Comparing with the advanced frozen-image model proposed by Yang et al., our model cannot only give the hysteretic characteristic in the first descent-ascent cycle of magnet, but also show the hysteresis loops with the same area for the second and subsequent cycles.

Wu, Xing-da; Xu, Ke-Xi; Cao, Yue; Hu, Shun-bo; Zuo, Peng-xiang; Li, Guan-dong

2013-03-01

416

Physics of forced magnetic reconnection in coaxial helicity injection experiments in National Spherical Torus Experiment  

SciTech Connect

We numerically examine the physics of fast flux closure in transient coaxial helicity injection (CHI) experiments in National Spherical Torus Experiment (NSTX). By performing resistive Magnetohydrodynamics (MHD) simulations with poloidal injector coil currents held constant in time, we find that closed flux surfaces are formed through forced magnetic reconnection. Through a local Sweet-Parker type reconnection with an elongated current sheet in the injector region, closed flux surfaces expand in the NSTX global domain. Simulations demonstrate outflows approaching poloidally Alfvnic flows and reconnection times consistent with the Sweet-Parker model. Critical requirements for magnetic reconnection and flux closure are studied in detail. These primary effects, which are magnetic diffusivity, injector flux, injector flux footprint width, and rate of injector voltage reduction, are simulated for transient CHI experiments. The relevant time scales for effective reconnection are ?{sub V}

Ebrahimi, F.; Bhattacharjee, A. [Department of Astrophysical Sciences, and Princeton Plasma Physics Laboratory, Princeton University, New Jersey 08544 (United States)] [Department of Astrophysical Sciences, and Princeton Plasma Physics Laboratory, Princeton University, New Jersey 08544 (United States); Raman, R. [University of Washington, Seattle, Washington 98195 (United States)] [University of Washington, Seattle, Washington 98195 (United States); Hooper, E. B. [Lawrence Livermore National Laboratory, Livermore, California 94526 (United States)] [Lawrence Livermore National Laboratory, Livermore, California 94526 (United States); Sovinec, C. R. [University of Wisconsin, Madison, Wisconsin 53706 (United States)] [University of Wisconsin, Madison, Wisconsin 53706 (United States)

2014-05-15

417

Variability of height, weight, and body mass index in a Swiss armed forces 2005 census.  

PubMed

The influence of the environment and genetics on individual biological characteristics, such as body mass and stature is well known. Many studies of these relationships have been based on conscript data. These studies often suffer from the fact that their data cover only a part of the population. Characterized by prosperity, democratic stability and enormous micro-regional cultural diversity, Switzerland is in the unique situation of offering data covering more than 80% of annual male birth cohorts. The aim of this study is to assess the impact of socioeconomic success, cultural differences, month of birth, and altitude (among other factors) on individual anthropometric characteristics of conscripts (N approximately 28,000) in the 2005 census. Our result highlights in such a large male sample the relationship between economic environment, regional cultural diversity, climate, and other factors, such as individual month of birth on stature and weight. Socioeconomic status, culture (as reflected by mother tongue), and month of birth were found to have significant effects on height and weight, while altitude did not show such effects. In general, weight is more affected by all these variables than height. Taking weight-dependent mortality and morbidity into account, it is of foremost public interest to know more about paired effects of living conditions on stature and weight in a highly developed society. PMID:18668685

Rhli, Frank; Henneberg, Maciej; Woitek, Ulrich

2008-12-01

418

Solar Wind Effects on Atmospheres of the Weakly Magnetized Bodies: Mars, Titan and the Moon  

NASA Technical Reports Server (NTRS)

The atmospheres of planetary bodies without significant intrinsic magnetic fields exhibit unique features because they interact with the external plasma flows in their space environment. The plasma interactions also have the potential of altering the evolutionary paths of these atmospheres since the processes (such as ion pickup and sputtering) that lead to loss of constituents have effects unlike those of other escape mechanisms. This ongoing investigation has been concentrating on the characterization of the plasma interactions and the associated plasma physical escape processes at Mars and Titan. The results are relevant to both mission planning and interpretation of data from past and future Mars and Lunar missions, and to tour and mission operations planning for the Cassini Orbiter. The also contribute to our general understanding, from a comparative planetology standpoint, of the role that planetary magnetic field play in determining the state and fate of a planetary atmosphere.

Luhmann, Janet G.

1996-01-01

419

Magnetism  

NSDL National Science Digital Library

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

Team, University C.

2007-12-12

420

Comparison between magnetic force microscopy and electron back-scatter diffraction for ferrite quantification in type 321 stainless steel.  

PubMed

Several analytical techniques that are currently available can be used to determine the spatial distribution and amount of austenite, ferrite and precipitate phases in steels. The application of magnetic force microscopy, in particular, to study the local microstructure of stainless steels is beneficial due to the selectivity of this technique for detection of ferromagnetic phases. In the comparison of Magnetic Force Microscopy and Electron Back-Scatter Diffraction for the morphological mapping and quantification of ferrite, the degree of sub-surface measurement has been found to be critical. Through the use of surface shielding, it has been possible to show that Magnetic Force Microscopy has a measurement depth of 105-140nm. A comparison of the two techniques together with the depth of measurement capabilities are discussed. PMID:25195013

Warren, A D; Harniman, R L; Collins, A M; Davis, S A; Younes, C M; Flewitt, P E J; Scott, T B

2015-01-01

421

Cell membrane deformations under magnetic force modulation characterized by optical tracking and non-interferometric widefield profilometry.  

PubMed

We measured cell membrane deformations under the modulation of piconewton magnetic force by using optical tracking and noninterferometric widefield optical profilometry. The magnetic force was applied to fibronectin-coated paramagnetic beads that bound to transmembrane protein integrins. At an image-acquisition rate of 20 frame/min, optical tracking provided positioning accuracy better than 70 nm for bead displacements on cell membranes, and optical profilometry obtained membrane topography with 20 nm depth resolution. We elucidated the correlation between the bead movements and membrane deformations. When the magnetic force dominated the bead movements, the membrane arose in front of the bead and the height increased with the bead velocity. On the other hand, when the bead was mainly driven by the cytoskeletons, the membrane profiles showed no relevance to the motion of the bead. In this case, the bead moved faster on smooth membranes. A model based on the dynamics of actin cytoskeletons is proposed to explain these observation results. PMID:18452190

Wang, Chun-Chieh; Jian, Hung-Jhang; Wu, Chih-Wei; Lee, Chau-Hwang

2008-08-01

422

A nonlinear eigenvalue problem for self-similar spherical force-free magnetic fields  

SciTech Connect

An axisymmetric force-free magnetic field B(r, ?) in spherical coordinates is defined by a function r?sin??B{sub ?}=Q(A) relating its azimuthal component to its poloidal flux-function A. The power law r?sin??B{sub ?}=aA|A|{sup 1/n}, n a positive constant, admits separable fields with A=(A{sub n}(?))/(r{sup n}) , posing a nonlinear boundary-value problem for the constant parameter a as an eigenvalue and A{sub n}(?) as its eigenfunction [B. C. Low and Y. Q Lou, Astrophys. J. 352, 343 (1990)]. A complete analysis is presented of the eigenvalue spectrum for a given n, providing a unified understanding of the eigenfunctions and the physical relationship between the field's degree of multi-polarity and rate of radial decay via the parameter n. These force-free fields, self-similar on spheres of constant r, have basic astrophysical applications. As explicit solutions they have, over the years, served as standard benchmarks for testing 3D numerical codes developed to compute general force-free fields in the solar corona. The study presented includes a set of illustrative multipolar field solutions to address the magnetohydrodynamics (MHD) issues underlying the observation that the solar corona has a statistical preference for negative and positive magnetic helicities in its northern and southern hemispheres, respectively; a hemispherical effect, unchanging as the Sun's global field reverses polarity in successive eleven-year cycles. Generalizing these force-free fields to the separable form B=(H(?,?))/(r{sup n+2}) promises field solutions of even richer topological varieties but allowing for ?-dependence greatly complicates the governing equations that have remained intractable. The axisymmetric results obtained are discussed in relation to this generalization and the Parker Magnetostatic Theorem. The axisymmetric solutions are mathematically related to a family of 3D time-dependent ideal MHD solutions for a polytropic fluid of index ??=?4/3 as discussed in the Appendix.

Lerche, I. [Institut fr Geowissenschaften, Naturwissenschaftliche Fakultt III, Martin-Luther Universitt, D-06099 Halle (Germany); Low, B. C. [High Altitude Observatory, National Center for Atmospheric Research, Boulder, Colorado 80307 (United States)

2014-10-15

423

EFFECT OF POLARIMETRIC NOISE ON THE ESTIMATION OF TWIST AND MAGNETIC ENERGY OF FORCE-FREE FIELDS  

SciTech Connect

The force-free parameter {alpha}, also known as helicity parameter or twist parameter, bears the same sign as the magnetic helicity under some restrictive conditions. The single global value of {alpha} for a whole active region gives the degree of twist per unit axial length. We investigate the effect of polarimetric noise on the calculation of global {alpha} value and magnetic energy of an analytical bipole. The analytical bipole has been generated using the force-free field approximation with a known value of constant {alpha} and magnetic energy. The magnetic parameters obtained from the analytical bipole are used to generate Stokes profiles from the Unno-Rachkovsky solutions for polarized radiative transfer equations. Then we add random noise of the order of 10{sup -3} of the continuum intensity (I {sub c}) in these profiles to simulate the real profiles obtained by modern spectropolarimeters such as Hinode (SOT/SP), SVM (USO), ASP, DLSP, POLIS, and SOLIS etc. These noisy profiles are then inverted using a Milne-Eddington inversion code to retrieve the magnetic parameters. Hundred realizations of this process of adding random noise and polarimetric inversion is repeated to study the distribution of error in global {alpha} and magnetic energy values. The results show that (1) the sign of {alpha} is not influenced by polarimetric noise and very accurate values of global twist can be calculated, and (2) accurate estimation of magnetic energy with uncertainty as low as 0.5% is possible under the force-free condition.

Tiwari, Sanjiv Kumar; Venkatakrishnan, P.; Gosain, Sanjay; Joshi, Jayant [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313 001 (India)], E-mail: stiwari@prl.res.in, E-mail: pvk@prl.res.in, E-mail: sgosain@prl.res.in, E-mail: jayant@prl.res.in

2009-07-20

424

One-dimensional particle simulation of the filamentation instability: electrostatic field driven by the magnetic pressure gradient force  

E-print Network

Two counter-propagating cool and equally dense electron beams are modelled with particle-in-cell (PIC) simulations. The electron beam filamentation instability is examined in one spatial dimension, which is an approximation for a quasi-planar filament boundary. It is confirmed, that the force on the electrons imposed by the electrostatic field, which develops during the nonlinear stage of the instability, oscillates around a mean value that equals the magnetic pressure gradient force. The forces acting on the electrons due to the electrostatic and the magnetic field have a similar strength. The electrostatic field reduces the confining force close to the stable equilibrium of each filament and increases it farther away, limiting the peak density. The confining time-averaged total potential permits an overlap of current filaments with an opposite flow direction.

Dieckmann, M E; Borghesi, M; Rowlands, G

2009-01-01

425

One-dimensional particle simulation of the filamentation instability: Electrostatic field driven by the magnetic pressure gradient force  

SciTech Connect

Two counterpropagating cool and equally dense electron beams are modeled with particle-in-cell simulations. The electron beam filamentation instability is examined in one spatial dimension, which is an approximation for a quasiplanar filament boundary. It is confirmed that the force on the electrons imposed by the electrostatic field, which develops during the nonlinear stage of the instability, oscillates around a mean value that equals the magnetic pressure gradient force. The forces acting on the electrons due to the electrostatic and the magnetic field have a similar strength. The electrostatic field reduces the confining force close to the stable equilibrium of each filament and increases it farther away, limiting the peak density. The confining time-averaged total potential permits an overlap of current filaments with an opposite flow direction.

Dieckmann, M. E.; Kourakis, I.; Borghesi, M. [Centre for Plasma Physics, Queen's University Belfast, Belfast BT7 1NN (United Kingdom); Rowlands, G. [Department of Physics, Warwick University, Coventry CV4 7AL (United Kingdom)

2009-07-15

426

Solar wind interaction with small bodies. 2: What can Galileo's detection of magnetic rotations tell us about Gaspra and Ida  

NASA Technical Reports Server (NTRS)

As the Galileo spacecraft passed the asteroids Gaspra in 1990 and Ida in 1993, the magnetometer recorded changes in the solar wind magnetic field that we associate with the presence of the nearby body. This paper focuses on the types of interactions that can produce perturbations in the solar wind. We have suggested that the interaction at Gaspra is consistent with expectations of flow diversion by a magnetic dipole moment and an associated 'magnetosphere' whose scale size is much larger than the diameter of the solid body. The conditions for the Ida flyby leave more room for ambiguity. The observations could plausibly be related to either interaction with a magnetized body or with a conducting body. We will report on details of the observations that may enable us to distinguish between the different types of interaction and to provide quantitative estimates of the physical properties of the asteroids themselves.

Kivelson, M. G.; Wang, Z.; Joy, S.; Khurana, K. K.; Polanskey, C.; Southwood, D. J.; Walker, R. J.

1995-01-01

427

Reduction of Cogging Force in a Linear Flux-Switching Permanent-Magnet Brushless AC Machine for Direct-Drive Applications  

Microsoft Academic Search

The linear flux-switching permanent-magnet (LFSPM) machine is a novel linear brushless ac machine with magnets and armature windings in the short mover, which isa competitivecandidatefor direct-drive applications due to the inherent sinusoidalback-electromotive force and high force capability. However, the resulting cogging force is serious because of the double salient structure. In this paper, a one-tooth model for the cogging force

Shigui Zhou; Haitao Yu; Minqiang Hu; Chongxue Jiang; Li Hao

2011-01-01

428

Magnetic Energy and Helicity Budgets in the Active-Region Solar Corona. I. Linear Force-Free Approximation  

E-print Network

We self-consistently derive the magnetic energy and relative magnetic helicity budgets of a three-dimensional linear force-free magnetic structure rooted in a lower boundary plane. For the potential magnetic energy we derive a general expression that gives results practically equivalent to those of the magnetic Virial theorem. All magnetic energy and helicity budgets are formulated in terms of surface integrals applied to the lower boundary, thus avoiding computationally intensive three-dimensional magnetic field extrapolations. We analytically and numerically connect our derivations with classical expressions for the magnetic energy and helicity, thus presenting a so-far lacking unified treatment of the energy/helicity budgets in the constant-alpha approximation. Applying our derivations to photospheric vector magnetograms of an eruptive and a noneruptive solar active regions, we find that the most profound quantitative difference between these regions lies in the estimated free magnetic energy and relative magnetic helicity budgets. If this result is verified with a large number of active regions, it will advance our understanding of solar eruptive phenomena. We also find that the constant-alpha approximation gives rise to large uncertainties in the calculation of the free magnetic energy and the relative magnetic helicity. Therefore, care must be exercised when this approximation is applied to photospheric magnetic field observations. Despite its shortcomings, the constant-alpha approximation is adopted here because this study will form the basis of a comprehensive nonlinear force-free description of the energetics and helicity in the active-region solar corona, which is our ultimate objective.

M. K. Georgoulis; Barry J. LaBonte

2007-06-27

429

Testing non-linear force-free coronal magnetic field extrapolations with the Titov-Demoulin equilibrium  

E-print Network

CONTEXT: As the coronal magnetic field can usually not be measured directly, it has to be extrapolated from photospheric measurements into the corona. AIMS: We test the quality of a non-linear force-free coronal magnetic field extrapolation code with the help of a known analytical solution. METHODS: The non-linear force-free equations are numerically solved with the help of an optimization principle. The method minimizes an integral over the force-free and solenoidal condition. As boundary condition we use either the magnetic field components on all six sides of the computational box in Case I or only on the bottom boundary in Case II. We check the quality of the reconstruction by computing how well force-freeness and divergence-freeness are fulfilled and by comparing the numerical solution with the analytical solution. The comparison is done with magnetic field line plots and several quantitative measures, like the vector correlation, Cauchy Schwarz, normalized vector error, mean vector error and magnetic energy. RESULTS: For Case I the reconstructed magnetic field shows good agreement with the original magnetic field topology, whereas in Case II there are considerable deviations from the exact solution. This is corroborated by the quantitative measures, which are significantly better for Case I. CONCLUSIONS: Despite the strong nonlinearity of the considered force-free equilibrium, the optimization method of extrapolation is able to reconstruct it; however, the quality of reconstruction depends significantly on the consistency of the input data, which is given only if the known solution is provided also at the lateral and top boundaries, and on the presence or absence of flux concentrations near the boundaries of the magnetogram.

Thomas Wiegelmann; Bernd Inhester; Bernhard Kliem; Gherardo Valori; Thomas Neukirch

2006-12-21

430

Influence of Critical Current Density on Magnetic Force of Htsc Bulk above Pmr with 3D-MODELING Numerical Solutions  

NASA Astrophysics Data System (ADS)

Numerical electromagnetic field simulations of high-temperature superconductors (HTSC) bulk were carried out to calculate the magnetic force between the HTSC bulk and the permanent magnet railway (PMR). A 3D-modeling numerical calculation method is proposed using the finite element method. The model is formulated with the magnetic field vector (H-method). The resulting code was written with FORTRAN language. The electric field intensity E and the current density J constitutive relation of HTSC were described with E-J power law. The Kim macro-model is used to describe critical current density Jc of HTSC bulk. Two virtual HTSC bulks were used to solve the critical current density Jc anisotropic properties of HTSC materials. A superconducting levitation system composed of one HTSC bulk and PMR is successfully investigated using the proposed method. By this method, the influence of critical current density on magnetic levitation force of the superconducting levitation system is mathematically studied.

Lu, Yiyun; Lu, Bingjuan; Ge, Yunwang; Chen, Wenqing

431

Direct current force sensing device based on compressive spring, permanent magnet, and coil-wound magnetostrictive/piezoelectric laminate.  

PubMed

A force sensing device capable of sensing dc (or static) compressive forces is developed based on a NAS106N stainless steel compressive spring, a sintered NdFeB permanent magnet, and a coil-wound Tb(0.3)Dy(0.7)Fe(1.92)/Pb(Zr, Ti)O3 magnetostrictive?piezoelectric laminate. The dc compressive force sensing in the device is evaluated theoretically and experimentally and is found to originate from a unique force-induced, position-dependent, current-driven dc magnetoelectric effect. The sensitivity of the device can be increased by increasing the spring constant of the compressive spring, the size of the permanent magnet, and/or the driving current for the coil-wound laminate. Devices of low-force (20 N) and high-force (200 N) types, showing high output voltages of 262 and 128 mV peak, respectively, are demonstrated at a low driving current of 100 mA peak by using different combinations of compressive spring and permanent magnet. PMID:24387458

Leung, Chung Ming; Or, Siu Wing; Ho, S L

2013-12-01

432

Direct current force sensing device based on compressive spring, permanent magnet, and coil-wound magnetostrictive/piezoelectric laminate  

NASA Astrophysics Data System (ADS)

A force sensing device capable of sensing dc (or static) compressive forces is developed based on a NAS106N stainless steel compressive spring, a sintered NdFeB permanent magnet, and a coil-wound Tb0.3Dy0.7Fe1.92/Pb(Zr, Ti)O3 magnetostrictive/piezoelectric laminate. The dc compressive force sensing in the device is evaluated theoretically and experimentally and is found to originate from a unique force-induced, position-dependent, current-driven dc magnetoelectric effect. The sensitivity of the device can be increased by increasing the spring constant of the compressive spring, the size of the permanent magnet, and/or the driving current for the coil-wound laminate. Devices of low-force (20 N) and high-force (200 N) types, showing high output voltages of 262 and 128 mV peak, respectively, are demonstrated at a low driving current of 100 mA peak by using different combinations of compressive spring and permanent magnet.

Leung, Chung Ming; Or, Siu Wing; Ho, S. L.

2013-12-01

433

Numerical computation for a new way to reduce vibration and noise due to magnetostriction and magnetic forces of transformer cores  

NASA Astrophysics Data System (ADS)

Magnetostriction (MS) caused by the global magnetization of limbs and yokes and magnetic forces are the undisputed causes of the vibration and noise in power transformer cores. This paper presents a novel way to reduce the vibration and noise, in which nanocrystalline soft magnetic composite (NSMC) material with high permeability is used to fill the step-lap joint gaps of the power transformer magnetic cores. In order to numerically predict the effectiveness of the proposed method, a 3-D magneto-mechanical strong coupled model including MS and magnetic anisotropy of steel sheet was founded. Then, the numerical model was applied to analyze the step-lap joint region of the corner of magnetic cores. The analysis results illustrated that the deformation and noise of core with NSMC are lower than with the traditional epoxy damping material. Moreover, the validity of the proposed new way was verified by the simplified step-lap joint cores, which were achieved based on Epstein Frames.

Zhu, Lihua; Yang, Qingxin; Yan, Rongge; Li, Yongjian; Zhang, Xian; Yan, Weili; Zhu, Jianguo

2013-05-01

434

Frustrated magnetic vortices in a triad of permalloy rings: Magneto-optical Kerr effect, magnetic force microscopy, and micromagnetic simulations  

E-print Network

Frustrated magnetic vortices in a triad of permalloy rings: Magneto-optical Kerr effect, magnetic of magnetic vortices, leaving at least one ring in a magnetically frustrated state. The properties October 2005; published 28 March 2006 The field dependent magnetization of three mutually touching

Metlushko, Vitali

435

Baseband Detection of Bistatic Electron Spin Signals in Magnetic Resonance Force Microscopy (MRFM)  

E-print Network

In single spin Magnetic Resonance Force Microscopy (MRFM), the objective is to detect the presence of an electron (or nuclear) spin in a sample volume by measuring spin-induced attonewton forces using a micromachined cantilever. In the OSCAR method of single spin MRFM, the spins are manipulated by an external rf field to produce small periodic deviations in the resonant frequency of the cantilever. These deviations can be detected by frequency demodulation followed by conventional amplitude or energy detection. In this paper, we present an alternative to these detection methods, based on optimal detection theory and Gibbs sampling. On the basis of simulations, we show that our detector outperforms the conventional amplitude and energy detectors for realistic MRFM operating conditions. For example, to achieve a 10% false alarm rate and an 80% correct detection rate our detector has an 8 dB SNR advantage as compared with the conventional amplitude or energy detectors. Furthermore, at these detection rates it comes within 4 dB of the omniscient matched-filter lower bound.

Chun-yu Yip; Alfred O. Hero; Daniel Rugar; Jeffrey A. Fessler

2003-07-07

436

The dust motion inside the magnetized sheath - The effect of drag forces  

SciTech Connect

The isolated charged dust inside the magnetized plasma sheath moves under the influence of the electron and ion drag force and the sheath electrostatic field. The charge on the dust is a function of its radius as well as the value of the ambient sheath potential. It is shown that the charge on the dust determines its trajectory and dust performs the spiraling motion inside the sheath. The location of the turning spiral is determined by the number of negative charge on the dust, which in turn is a function of the dust radius. The back and forth spiraling motion finally causes the dust to move in a small, narrow region of the sheath. For a bigger dust particle, the dust moves closer to the sheath presheath boundary suggesting that the bigger grains, owing to the strong repulsion between the wall and dust, will be unable to travel inside the sheath. Only small, micron-sized grains can travel closer to the wall before repulsion pushes it back toward the plasma-sheath boundary. The temporal behavior of the spiraling dust motion appears like a damped harmonic oscillation, suggesting that the plasma drag force causes dissipation of the electrostatic energy. However, after initial damping, the grain keeps oscillating although with much smaller amplitude. The possible application of the present results to the ongoing sheath experiments is discussed.

Pandey, B. P. [Department of Physics and Astronomy, Macquarie University, Sydney, New South Wales 2109 (Australia); Samarian, A.; Vladimirov, S. V. [School of Physics, University of Sydney, New South Wales 2006 (Australia)

2010-08-15

437

Health sensor for human body by using infrared, acoustic energy and magnetic signature  

NASA Astrophysics Data System (ADS)

There is a general chain of events that applies to infections. Human body infection could causes by many different types of bacteria and virus in different areas or organ systems. In general, doctor can't find out the right solution/treatment for infections unless some certain types of bacteria or virus are detected. These detecting processes, usually, take few days to one week to accomplish. However, some infections of the body may not be able to detect at first round and the patient may lose the timing to receive the proper treatment. In this works, we base on Chi's theory which is an invisible circulation system existed inside the body and propose a novel health sensor which summarizes human's infrared, acoustic energy and magnetic signature and find out, in minutes, the most possible area or organ system that cause the infection just like what Chi-Kung master can accomplish. Therefore, the detection process by doctor will be shortened and it raises the possibility to give the proper treatment to the patient in the earliest timing.

Wu, Jerry

2013-05-01

438

Vertically polarizing undulator with the dynamic compensation of magnetic forces for the next generation of light sources  

NASA Astrophysics Data System (ADS)

A short prototype (847-mm-long) of an Insertion Device (ID) with the dynamic compensation of ID magnetic forces has been designed, built, and tested at the Advanced Photon Source (APS) of the Argonne National Laboratory. The ID magnetic forces were compensated by the set of conical springs placed along the ID strongback. Well-controlled exponential characteristics of conical springs permitted a very close fit to the ID magnetic forces. Several effects related to the imperfections of actual springs, their mounting and tuning, and how these factors affect the prototype performance has been studied. Finally, series of tests to determine the accuracy and reproducibility of the ID magnetic gap settings have been carried out. Based on the magnetic measurements of the ID Beff, it has been demonstrated that the magnetic gaps within an operating range were controlled accurately and reproducibly within 1 ?m. Successful tests of this ID prototype led to the design of a 3-m long device based on the same concept. The 3-m long prototype is currently under construction. It represents R&D efforts by the APS toward APS Upgrade Project goals as well as th