Note: This page contains sample records for the topic tesla magnetic field from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Nikola Tesla: the man behind the magnetic field unit.  

PubMed

The magnetic field strength of both the magnet and gradient coils used in MR imaging equipment is measured in Tesla units, which are named for Nikola Tesla. This article presents the life and achievements of this Serbian-American inventor and researcher who discovered the rotating magnetic field, the basis of most alternating-current machinery. Nikola Tesla had 700 patents in the United States and Europe that covered every aspect of science and technology. Tesla's discoveries include the Tesla coil, AC electrical conduction, improved lighting, newer forms of turbine engines, robotics, fluorescent light, wireless transmission of electrical energy, radio, remote control, discovery of cosmic radio waves, and the use of the ionosphere for scientific purposes. He was a genius whose discoveries had a pivotal role in advancing us into the modern era. PMID:14994307

Roguin, Ariel

2004-03-01

2

Field Quality Measurements of a 2Tesla Transmission Line Magnet  

Microsoft Academic Search

A prototype 2-Tesla superconducting transmission line magnet for future hadron colliders was designed, built and tested at Fermilab. The 1.5 m long, combined-function gradient-dipole magnet has a vertical pole aperture of 20 mm. To measure the magnetic field quality in such a small magnet aperture, a specialized rotating coil of 15.2 mm diameter, 0.69 m long was fabricated. Using this

G. V. Velev; W. Foster; V. Kashikhin; P. Mazur; A. Oleck; H. Piekarz; P. Schlabach; C. Sylvester; M. Wake

2006-01-01

3

B > 1 Tesla low mass magnetic field sweep assembly  

NASA Astrophysics Data System (ADS)

We have designed, modeled and tested a variable magnetic field sweep unit over a wide temperature range, from cryogenic to 100 C. The unit provides a sweepable uniform magnetic field, independent of temperature, over an air gap of 2 mm and spatial extent of 4 mm x 4 mm. It consists of a small magnet yoke structure and a spur gear driven rotatable magnet to vary the gap field in a nearly sinusoidal manner as a function of the magnet rotation angle. In the present design a 20 g SmCo magnet has been used, which allows for low temperature operation to 15 K when attached to a cryogenic refrigerator cold finger. The shape of the magnetic yoke structure has been modeled and optimized using 3-D magnetic field software. The gap field uniformity can thus be modeled and tested experimentally. In a present working model (2 mm gap) the field B(?) = 1.0 sin(?) (Tesla) where ? is the magnet rotation angle. With 0.25 mm thick permunder pole tips the field amplitude has been increased to 1.2 Tesla over a gap of 1.5 mm.

Cadieu, F. J.; Heremans, J. J.; Griffin, J.; Caldwell, C.; von Molnar, S.

1997-03-01

4

Magnetic resonance electrical impedance tomography at 3 Tesla field strength.  

PubMed

Magnetic resonance electrical impedance tomography (MREIT) is a recently developed imaging technique that combines MRI and electrical impedance tomography (EIT). In MREIT, cross-sectional electrical conductivity images are reconstructed from the internal magnetic field density data produced inside an electrically conducting object when an electrical current is injected into the object. In this work we present the results of electrical conductivity imaging experiments, and performance evaluations of MREIT in terms of noise characteristics and spatial resolution. The MREIT experiment was performed with a 3.0 Tesla MRI system on a phantom with an inhomogeneous conductivity distribution. We reconstructed the conductivity images in a 128 x 128 matrix format by applying the harmonic B(z) algorithm to the z-component of the internal magnetic field density data. Since the harmonic B(z) algorithm uses only a single component of the internal magnetic field data, it was not necessary to rotate the object in the MRI scan. The root mean squared (RMS) errors of the reconstructed images were between 11% and 35% when the injection current was 24 mA. PMID:15170853

Oh, Suk H; Lee, Byung I; Park, Tae S; Lee, Soo Y; Woo, Eung J; Cho, Min H; Seo, Jin K; Kwon, Ohin

2004-06-01

5

Magnetic Semiconductor Quantum Wells in High Fields to 60 Tesla: Photoluminescence Linewidth Annealing at Magnetization Steps  

SciTech Connect

Magnetic semiconductors offer a unique possibility for strongly tuning the intrinsic alloy disorder potential with applied magnetic field. We report the direct observation of a series of step-like reductions in the magnetic alloy disorder potential in single ZnSe/Zn(Cd,Mn)Se quantum wells between O and 60 Tesla. This disorder, measured through the linewidth of low temperature photoluminescence spectra drops abruptly at -19, 36, and 53 Tesla, in concert with observed magnetization steps. Conventional models of alloy disorder (developed for nonmagnetic semiconductors) reproduce the general shape of the data, but markedly underestimate the size of the linewidth reduction.

Awschalom, D.D.; Crooker, S.A.; Lyo, S.K.; Rickel, D.G.; Samarth, N.

1999-05-24

6

Functionality of veterinary identification microchips following low- (0.5 tesla) and high-field (3 tesla) magnetic resonance imaging.  

PubMed

The ability to read patient identification microchips relies on the use of radiofrequency pulses. Since radiofrequency pulses also form an integral part of the magnetic resonance imaging (MRI) process, the possibility of loss of microchip function during MRI scanning is of concern. Previous clinical trials have shown microchip function to be unaffected by MR imaging using a field strength of 1 Tesla and 1.5. As veterinary MRI scanners range widely in field strength, this study was devised to determine whether exposure to lower or higher field strengths than 1 Tesla would affect the function of different types of microchip. In a phantom study, a total of 300 International Standards Organisation (ISO)-approved microchips (100 each of three different types: ISO FDX-B 1.4 × 9 mm, ISO FDX-B 2.12 × 12 mm, ISO HDX 3.8 × 23 mm) were tested in a low field (0.5) and a high field scanner (3.0 Tesla). A total of 50 microchips of each type were tested in each scanner. The phantom was composed of a fluid-filled freezer pack onto which a plastic pillow and a cardboard strip with affixed microchips were positioned. Following an MRI scan protocol simulating a head study, all of the microchips were accurately readable. Neither 0.5 nor 3 Tesla imaging affected microchip function in this study. PMID:23763334

Piesnack, Susann; Frame, Mairi E; Oechtering, Gerhard; Ludewig, Eberhard

2013-01-01

7

Optical Signatures from Magnetic 2-D Electron Gases in High Magnetic Fields to 60 Tesla  

SciTech Connect

We present experiments in the 60 Tesla Long-Pulse magnet at the Los Alamos National High Magnetic Field Lab (NHMFL) focusing on the high-field, low temperature photoluminescence (PL) from modulation-doped ZnSe/Zn(Cd,Mn)Se single quantum wells. High-speed charge-coupled array detectors and the long (2 second) duration of the magnet pulse permit continuous acquisition of optical spectra throughout a single magnet shot. High-field PL studies of the magnetic 2D electron gases at temperatures down to 350mK reveal clear intensity oscillations corresponding to integer quantum Hall filling factors, from which we determine the density of the electron gas. At very high magnetic fields, steps in the PL energy are observed which correspond to the partial unlocking of antiferromagnetically bound pairs of Mn2+ spins.

Crooker, S.A.; Kikkawa, J.M.; Awschalom, D.D.; Smorchikova, I.P.; Samarth, N.

1998-11-08

8

Resting brain metabolic activity in a 4 tesla magnetic field.  

PubMed

MRI is a major tool for mapping brain function; thus it is important to assess potential effects on brain neuronal activity attributable to the requisite static magnetic field. This study used positron emission tomography (PET) and (18)F-deoxyglucose ((18)FDG) to measure brain glucose metabolism (a measure of brain function) in 12 subjects while their heads were in a 4 T MRI field during the (18)FDG uptake period. The results were compared with those obtained when the subjects were in the earth's field (PET scanner), and when they were in a simulated MRI environment in the PET instrument that imitated the restricted visual field of the MRI experiment. Whole-brain metabolism, as well as metabolism in occipital cortex and posterior cingulate gyrus, was lower in the real (4 T) and simulated (0 T) MRI environments compared with the PET. This suggests that the metabolic differences are due mainly to the visual field differences characteristic of the MRI and PET instruments. We conclude that a static magnetic field of 4 T does not in itself affect this fairly sensitive measure of brain activity. PMID:11064404

Volkow, N D; Wang, G J; Fowler, J S; Rooney, W D; Felder, C A; Lee, J H; Franceschi, D; Maynard, L; Schlyer, D J; Pan, J W; Gatley, S J; Springer Jr, C S

2000-11-01

9

Magnetic field sensors applied to electropolishing of superconducting RF TESLA-type cavities  

NASA Astrophysics Data System (ADS)

In this work an electromagnetic non-invasive and contact-less technique using Flux-Gate first-order gradiometer is proposed to detect the magnetic field distribution during electropolishing of copper surface. The electropolishing of the copper surface employed in superconducting RF TESLA-type cavities has been monitored using magnetic field sensors. Local information regarding the dissolved copper surface during the electropolishing process has been obtained. An electromagnetic inversion of the magnetic field imaging have been implemented to better understand the effect of the cathode geometry on the electropolishing process.

Bonavolontà, C.; Valentino, M.; Palmieri, V.; Rampazzo, V.

2006-07-01

10

4.5 tesla magnetic field reduces range of high-energy positrons-potential implications for positron emission tomography  

Microsoft Academic Search

We have theoretically and experimentally investigated the extent to which homogeneous magnetic fields up to 7 Tesla reduce the spatial distance positrons travel before annihilation (positron range). Computer simulations of a noncoincident detector design using a Monte Carlo algorithm calculated the positron range as a function of positron energy and magnetic field strength. The simulation predicted improvements in resolution, defined

Andreas Wirrwar; Henning Vosberg; Hans Herzog; Horst Halling; Simone Weber; H. W. Mueller-Gaertner

1997-01-01

11

Impairment of chondrocyte biosynthetic activity by exposure to 3-tesla high-field magnetic resonance imaging is temporary  

PubMed Central

The influence of magnetic resonance imaging (MRI) devices at high field strengths on living tissues is unknown. We investigated the effects of a 3-tesla electromagnetic field (EMF) on the biosynthetic activity of bovine articular cartilage. Bovine articular cartilage was obtained from juvenile and adult animals. Whole joints or cartilage explants were subjected to a pulsed 3-tesla EMF; controls were left unexposed. Synthesis of sulfated glycosaminoglycans (sGAGs) was measured by using [35S]sulfate incorporation; mRNA encoding the cartilage markers aggrecan and type II collagen, as well as IL-1?, were analyzed by RT–PCR. Furthermore, effects of the 3-tesla EMF were determined over the course of time directly after exposure (day 0) and at days 3 and 6. In addition, the influence of a 1.5-tesla EMF on cartilage sGAG synthesis was evaluated. Chondrocyte cell death was assessed by staining with Annexin V and TdT-mediated dUTP nick end labelling (TUNEL). Exposure to the EMF resulted in a significant decrease in cartilage macromolecule synthesis. Gene expression of both aggrecan and IL-1?, but not of collagen type II, was reduced in comparison with controls. Staining with Annexin V and TUNEL revealed no evidence of cell death. Interestingly, chondrocytes regained their biosynthetic activity within 3 days after exposure, as shown by proteoglycan synthesis rate and mRNA expression levels. Cartilage samples exposed to a 1.5-tesla EMF remained unaffected. Although MRI devices with a field strength of more than 1.5 T provide a better signal-to-noise ratio and thereby higher spatial resolution, their high field strength impairs the biosynthetic activity of articular chondrocytes in vitro. Although this decrease in biosynthetic activity seems to be transient, articular cartilage exposed to high-energy EMF may become vulnerable to damage.

Sunk, Ilse-Gerlinde; Trattnig, Siegfried; Graninger, Winfried B; Amoyo, Love; Tuerk, Birgit; Steiner, Carl-Walter; Smolen, Josef S; Bobacz, Klaus

2006-01-01

12

Analytical studies of advanced high-field designs: 20-tesla large-bore superconducting magnets  

SciTech Connect

Several emerging technologies have been combined in a conceptual design study demonstrating the feasibility of producing ultrahigh magnetic fields from large-bore superconducting solenoid magnets. Several designs have been produced that approach peak fields of 20-T in 2.0-m diameter inner bores. The analytical expressions comprising the main features of CONDUCTOR and ADVMAGNET, the two computer programs used in the design of these advanced magnets, are also discussed. These magnets and design techniques will make a paramount contribution to the national mirror-fusion endeavor and to the newly emerging field of nuclear magnetic resonance (NMR) whole-body scanners.

Hoard, R.W.; Cornish, D.N.; Scanlan, R.M.; Zbasnik, J.P.; Leber, R.L.; Hickman, R.B.; Lee, J.D.

1983-09-30

13

Force-detected magnetic resonance in a field gradient of 250 000 Tesla per meter  

NASA Astrophysics Data System (ADS)

We report the detection of slice-selective electron spin resonance with an external magnetic field gradient comparable to local interatomic gradients, using the techniques of magnetic resonance force microscopy. An applied microwave field modulated the spin-gradient force between a paramagnetic DPPH sample and a micrometer-scale ferromagnetic tip on a force microscope cantilever. A sensitivity equivalent to 184 polarized electron moments in a one-Hertz detection bandwidth was attained. We mapped the tip magnetic field with a resonant slice thickness of order one nanometer, thereby demonstrating magnetic resonance on length scales comparable to molecular dimensions.

Bruland, K. J.; Dougherty, W. M.; Garbini, J. L.; Sidles, J. A.; Chao, S. H.

1998-11-01

14

A 10 tesla table-top controlled waveform magnet  

NASA Astrophysics Data System (ADS)

Controlled Waveform Magnets (CWMs) are a special class of pulsed magnets which provide semi-continuous, shape-controlled high magnetic field pulses. In this work we report a table-top CWM, driven by a capacitor bank, capable of producing virtually any user-shaped magnetic field waveform up to 10 Tesla. Insulated Gate Bipolar Transistor (IGBT) chips were paralleled to form the high current switch. Specimen pulse shapes including flat-tops up to 10 Tesla, and linear as well as some sinusoidal-top magnetic field waveforms have been successfully generated.

Roy Choudhury, Aditya N.; Venkataraman, V.

2012-06-01

15

Strain-Induced Pseudo-Magnetic Fields Greater Than 300 Tesla in Graphene Nanobubbles  

Microsoft Academic Search

Recent theoretical proposals suggest that strain can be used to engineer graphene electronic states through the creation of a pseudo-magnetic field. This effect is unique to graphene because of its massless Dirac fermion-like band structure and particular lattice symmetry (C3v). Here, we present experimental spectroscopic measurements by scanning tunneling microscopy of highly strained nanobubbles that form when graphene is grown

N. Levy; S. A. Burke; K. L. Meaker; M. Panlasigui; A. Zettl; F. Guinea; A. H. Castro Neto; M. F. Crommie

2010-01-01

16

Point contact spectrscopy of electron-doped cuprates in a magnetic field of 32 tesla  

NASA Astrophysics Data System (ADS)

Electron-doped cuprates have low values of the upper critical field (Hc2˜10 T at 1.5 K) and hence it is possible to study their normal state at low temperatures. Such studies have been done before and showed evidence of a ``pseudogap". However, to understand the origin of this pseudogap and which model of high-Tc superconductivity it supports, it is necessary to study the effect of high magnetic fields on this pseudogap. We have performed point contact spectroscopy experiments using junctions between a normal metal (Pt-Rh) and electron-doped Pr2-xCexCuO4 (PCCO) films for 0.13 < x < 0.17. To probe the normal state at low temperatures (˜ 0.4 K), we suppressed the superconductivity by applying high magnetic fields (up to 32T). We will show the effects of such high fields on the pseudogap and discuss our results in the context of present theories viz. preformed pairs and the presence of a quantum critical point.

Sung-Hee, Yun

2005-03-01

17

Mental rotation studied by functional magnetic resonance imaging at high field (4 tesla): performance and cortical activation.  

PubMed

We studied the performance and cortical activation patterns during a mental rotation task (Shepard & Metzler, 1971) using functional magnetic resonance imaging (fMlU) at high field (4 Tesla). Twenty-four human subjects were imaged (fMRI group), whereas six additional subjects performed the task without being imaged (control group). All subjects were shown pairs of perspective drawings of 31, objects and asked to judge whether they were the same or mirror images. The measures of performance examined included (1) the percentage of errors, (2) the speed of performance, calculated as the inverse of the average response time, and (3) the rate of rotation for those object pairs correctly identified as "same." We found the following: (1) Subjects in the fMRI group performed well outside and inside the magnet, and, in the latter case, before and during data acquisition. Moreover, performance over time improved in the same manner as in the control group. These findings indicate that exposure to high magnetic fields does not impair performance in mental rotation. (2) Functional activation data were analyzed from 16 subjects of the fMRI goup. Several cortical areas were activated during task performance. The relations between the measures of performance above and the magnitude of activation of specific cortical areas were investigated by anatomically demarcating these areas of interest and calculating a normalized activation for each one of them. (3) We used the multivariate technique of hierarchical tree modeling to determine functional clustering among areas of interest and performance measures. Two main branches were distinguished: One comprised areas in the right hemisphere and the extrastriate and superior parietal lobules bilaterally, whereas the other comprised areas of the left hemisphere and the frontal pole bilaterally; all three performance measures above clustered with the former branch. Specifically, performance outcome ("percentage of errors") clustered with the parieto-occipital subcluster, whereas both the speed of performance and the rate of mental rotation clustered with the right precentral gyms. We conclude that the mental rotation paradigm used involves the cooperative interaction of functional groups of cortical areas of which some are probably more specifically associated with performance, whereas others may serve a more general function within the task constraints. PMID:23968208

Tagaris, G A; Kim, S G; Strupp, J P; Andersen, P; U?urbil, K; Georgopoulos, A P

1997-07-01

18

First test of a power-pulsed electronics system on a GRPC detector in a 3-Tesla magnetic field  

NASA Astrophysics Data System (ADS)

Power-pulsed readout potentially offers a solution to the problem of high power consumption of the electronics for detectors at the future International Linear Collider (ILC) experiments. A 33 × 50cm2 Glass Resistive Plate Chamber (GRPC) equipped with a power-pulsed electronics board offering 1cm2 lateral segmentation was successfully tested in a 3-Tesla magnet. A significant reduction in power consumption with no deterioration of the detector performance was obtained when the power-pulsing mode was applied. This result shows that highly granular calorimeters for ILC experiments are not only an attractive but also a realistic option.

Caponetto, L.; Combaret, C.; de la Taille, C.; Dulucq, F.; Kieffer, R.; Laktineh, I.; Lumb, N.; Mirabito, L.; Seguin-Moreau, N.

2012-04-01

19

A 10 tesla table-top controlled waveform magnet.  

PubMed

Controlled waveform magnets (CWMs) are a class of pulsed magnets whose pulse shape with time can be programmed by the user. With a CWM, the user gains control not only over the magnitude of the field but also over its rate of change. In this work we present a table-top CWM, driven by a capacitor bank, capable of producing virtually any user-shaped magnetic field waveform up to 10 tesla. Insulated gate bipolar transistor chips have been paralleled to form the high current switch and paralleled chips of SiC Schottky diodes form the crowbar diode module. Sample controlled waveforms including flat-tops up to 10 tesla and some triangular magnetic field pulses have been successfully generated for 10-20 ms with a ripple <1%. PMID:22559572

Roy Choudhury, Aditya N; Venkataraman, V

2012-04-01

20

A 10 tesla table-top controlled waveform magnet  

NASA Astrophysics Data System (ADS)

Controlled waveform magnets (CWMs) are a class of pulsed magnets whose pulse shape with time can be programmed by the user. With a CWM, the user gains control not only over the magnitude of the field but also over its rate of change. In this work we present a table-top CWM, driven by a capacitor bank, capable of producing virtually any user-shaped magnetic field waveform up to 10 tesla. Insulated gate bipolar transistor chips have been paralleled to form the high current switch and paralleled chips of SiC Schottky diodes form the crowbar diode module. Sample controlled waveforms including flat-tops up to 10 tesla and some triangular magnetic field pulses have been successfully generated for 10-20 ms with a ripple <1%.

Roy Choudhury, Aditya N.; Venkataraman, V.

2012-04-01

21

Magnetic Field Interactions of Copper-Containing Intrauterine Devices in 3.0-Tesla Magnetic Resonance Imaging: In Vivo Study  

PubMed Central

Objective An ex vivo study found a copper-containing intrauterine device (IUD) to be safe for women undergoing an MRI examination at a 3.0-T field. No significant artifacts caused by the metallic implant were detected. However, there are still no in vivo data about these concerns. The aim of this study was to evaluate 3.0-T magnetic field interactions of copper-containing IUDs in vivo. Materials and Methods Magnetic field interactions and potential adverse events were evaluated in 33 women using a questionnaire-based telephone survey. Two experienced radiologists performed artifact evaluation on MR images of the pelvis. Results Eighteen patients were eligible for the survey. One patient reported a dislocation of the IUD after the MR examination. All other patients had no signs of field interactions. No IUD-related artifacts were found. Conclusion MRI at 3.0-T is possible for women with copper-containing IUDs. However, consulting a gynecologist to check the correct position of the IUD and exclude complications after an MR examination is highly recommended. High-quality clinical imaging of the female pelvis can be performed without a loss in image quality.

Einspieler, Henrik; Hachemian, Nilouparak; Prayer, Daniela; Trattnig, Siegfried; Weber, Michael; Ba-Ssalamah, Ahmed

2013-01-01

22

Some aspects of data processing for an optical absorption experiment in a pulsed 1000-Tesla magnet  

SciTech Connect

A procedure is given for the analysis of optical absorption data acquired in the hostile environment of a pulsed 1000-Tesla magnet. The 1000-Tesla magnetic field is achieved with an explosive charge which generates a shock wave that travels toward the sample of octachlorodirhenate.

Butler, L.G.; Maverick, A.W. [Louisiana State Univ., Baton Rouge, LA (United States). Dept. of Chemistry] [Louisiana State Univ., Baton Rouge, LA (United States). Dept. of Chemistry; Gallegos, C.H. [Bechtel-Nevada, Los Alamos, NM (United States)] [Bechtel-Nevada, Los Alamos, NM (United States); Goettee, J.D.; Fowler, C.M.; Rickel, D.G.; Gonzales, J.M.; Tabaka, L.J. [Los Alamos National Lab., NM (United States). National High Magnetic Field Lab.] [Los Alamos National Lab., NM (United States). National High Magnetic Field Lab.; Marshall, B.R. [Bechtel-Nevada, Santa Barbara, CA (United States). Special Technologies Lab.] [Bechtel-Nevada, Santa Barbara, CA (United States). Special Technologies Lab.

1998-11-01

23

Status of the NHMFL 60 tesla quasi-continuous magnet  

NASA Astrophysics Data System (ADS)

All components of the National High Magnetic Field Laboratory's (NHMFL) 60 T quasi-continuous magnet are now under construction, with complete delivery and installation expected in early 1996. This research magnet has a cold bore of 32 mm and will produce a constant 60 tesla for 100 ms plus a wide variety of other pulse shapes such as linear ramps, steps, crowbar decays, and longer flat-tops at lower fields. Fabrication and testing of prototype coils are described along with the layout, construction status, and protection philosophy of the 400 MW power supply. Examples of simulated pulse shapes are shown.

Campbell, L. J.; Boenig, H. J.; Rickel, D. G.; Schilig, J. B.; Sims, J. R.; Schneider-Muntau, H. J.

24

Singlet and triplet states of trions in ZuSe-based quantum wells probed by magnetic fields to 50 Tesla  

SciTech Connect

Singlet and triplet states of positively (X{sup +}) and negatively (X{sup -}) charged excitons in ZnSe-based quantum wells have been studied by means of photoluminescence in pulsed magnetic fields up to 50 T. The binding energy of the X{sup -} singlet state shows a monotonic increase with magnetic field with a tendency to saturation, while that of the X{sup +} slightly decreases. The triplet X{sup +} and X{sup -} states, being unbound at zero magnetic field, noticeably increase their binding energy in high magnetic fields. The experimental evidence for the interaction between the triplet and singlet states of lTions leading to their anticrossing in magnetic fields has been found.

Astakhov, G. V.; Yakovlev, D. R.; Crooker, S. A. (Scott A.); Barrick, T. (Todd); Dzyubenko, A. B.; Sander, Thomas; Kochereshko, V. P.; Ossau, W.; Faschinger, W.; Waag, A.

2002-01-01

25

Series tests of fine mesh photomultiplier tubes in magnetic fields of up to 1.2 Tesla  

NASA Astrophysics Data System (ADS)

The new lead/scintillating-fibre calorimeter ("SpaCal") for the backward region of the H1 experiment at HERA (DESY) is equipped with fine mesh phototubes which operate in a magnetic field close to 1 T. A large sample of these tubes of the types Hamamatsu R5505 and R5506, and Hamamatsu R2490-05, have been tested in fields of up to 1.2T. We have investigated the cathode homogeneity with and without magnetic field, the gain loss under the influence of the magnetic field, and stability with time. For a subsample of tubes, we have performed additional studies on stability with respect to temperature changes, variation of gain as a function of the magnetic field, high voltage discharges, single photo-electron response, and linearity. We finally summarize the experience with these tubes after one year of operation in the experiment.

Appuhn, R.-D.; Arndt, C.; Barrelet, E.; Barschke, R.; Bassler, U.; Bipp, T.; Boudry, V.; Brasse, F.; Bruncko, D.; Buchholz, R.; Chechelnitski, S.; Claxton, B.; Cozzika, G.; Cvach, J.; Dagoret-Campagne, S.; Dau, W. D.; Deckers, H.; Deckers, T.; Descamps, F.; Dirkmann, M.; Dowdell, J.; Efremenko, V.; Eisenhandler, E.; Eliseev, A. N.; Falley, G.; Ferencei, J.; Fleischer, M.; Fominykh, B.; Gadow, K.; Goerlach, U.; Gorbov, L. A.; Gorelov, I.; Grewe, M.; Hajduk, L.; Heck, A.; Herynek, I.; Hladký, J.; Hütte, M.; Hutter, H.; Janczur, W.; Janoth, J.; Jönsson, L.; Kolanoski, H.; Korbel, V.; Krivá?, F.; Lacour, D.; Laforge, B.; Lamarche, F.; Landon, M. P. J.; Laporte, J.-F.; Lehner, F.; Mara?ek, R.; Meier, K.; Meyer, A.; Migliori, A.; Moreau, F.; Müller, G.; Murín, P.; Nagovizin, V.; Nicholls, T. C.; Ozerov, D.; Perez, E.; Pharabod, J. P.; Pöschl, R.; Rostovtsev, A.; Royon, C.; Rybicki, K.; Schediwy, R.; Schleif, S.; Schmitt, K.; Schuhmacher, A.; Semenov, A.; Shekelyan, V.; Sirois, Y.; Smirnov, P. A.; Solochenko, V.; Špalek, J.; Spielmann, S.; Steiner, H.; Stellberger, A.; Stiewe, J.; Taševský, M.; Tchernyshov, V.; Thiele, K.; Tzamariudaki, E.; Valkár, S.; VanDenPlas, D.; Villet, G.; Wacker, K.; Walther, A.; Weber, M.; Wegener, D.; Wenk, T.; Žá?ek, J.; Zhokin, A.; Zuber, K.; H1 SpaCal Group

1998-02-01

26

The NHMFL 60 tesla, 100 millisecond pulsed magnet  

SciTech Connect

Among the new facilities to be offered by the National Science Foundation through the National High Magnetic Field Laboratory (NHMFL) are pulsed fields that can only be achieved at a national user facility by virtue of their strength, duration, and volume. In particular, a 44 mm bore pulsed magnet giving a 60 tesla field for 100 ms is in the final design stage. This magnet will be powered by a 1.4 GW motor-generator at Los Alamos and is an important step toward proving design principles that will be needed for the higher field quasi-stationary pulsed magnets that this power source is capable of driving. This report will discuss specifications and parameters of this magnet.

Boenig, H.J.; Campbell, L.J.; Rickel, D.G.; Rogers, J.D.; Schillig, J.B.; Sims, J.R. (Los Alamos National Lab., NM (United States)); Pernambuco-Wise, P.; Schneider-Muntau, H.J. (Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab.)

1992-11-09

27

Series tests of fine mesh photomultiplier tubes in magnetic fields of up to 1.2 Tesla  

Microsoft Academic Search

The new lead\\/scintillating-fibre calorimeter (“SpaCal”) for the backward region of the H1 experiment at HERA (DESY) is equipped with fine mesh phototubes which operate in a magnetic field close to 1 T. A large sample of these tubes of the types Hamamatsu R5505 and R5506, and Hamamatsu R2490-05, have been tested in fields of up to 1.2T. We have investigated

R.-D. Appuhn; C. Arndt; E. Barrelet; R. Barschke; U. Bassler; T. Bipp; V. Boudry; F. Brasse; D. Bruncko; R. Buchholz; S. Chechelnitski; B. Claxton; G. Cozzika; J. Cvach; S. Dagoret-Campagne; W. D. Dau; H. Deckers; T. Deckers; F. Descamps; M. Dirkmann; J. Dowdell; V. Efremenko; E. Eisenhandler; A. N. Eliseev; G. Falley; J. Ferencei; M. Fleischer; B. Fominykh; K. Gadow; U. Goerlach; L. A. Gorbov; I. Gorelov; M. Grewe; L. Hajduk; A. Heck; I. Herynek; J. Hladký; M. Hütte; H. Hutter; W. Janczur; J. Janoth; L. Jönsson; H. Kolanoski; V. Korbel; F. Kriván; D. Lacour; B. Laforge; F. Lamarche; M. P. J. Landon; J.-F. Laporte; F. Lehner; R. Maracek; K. Meier; A. Meyer; A. Migliori; F. Moreau; G. Müller; P. Murín; V. Nagovizin; T. C. Nicholls; D. Ozerov; E. Perez; J. P. Pharabod; R. Pöschl; A. Rostovtsev; C. Royon; K. Rybicki; R. Schediwy; S. Schleif; K. Schmitt; A. Schuhmacher; A. Semenov; V. Shekelyan; Y. Sirois; P. A. Smirnov; V. Solochenko; J. Špalek; S. Spielmann; H. Steiner; A. Stellberger; J. Stiewe; M. Tasevský; V. Tchernyshov; K. Thiele; E. Tzamariudaki; S. Valkár; D. Vandenplas; G. Villet; K. Wacker; A. Walther; M. Weber; D. Wegener; T. Wenk; J. Žá?ek; A. Zhokin; K. Zuber

1998-01-01

28

Occupational exposure of healthcare and research staff to static magnetic stray fields from 1.5-7 Tesla MRI scanners is associated with reporting of transient symptoms  

PubMed Central

Objectives Limited data is available about incidence of acute transient symptoms associated with occupational exposure to static magnetic stray fields from MRI scanners. We aimed to assess the incidence of these symptoms among healthcare and research staff working with MRI scanners, and their association with static magnetic field exposure. Methods We performed an observational study among 361 employees of 14 clinical and research MRI facilities in The Netherlands. Each participant completed a diary during one or more work shifts inside and/or outside the MRI facility, reporting work activities and symptoms (from a list of potentially MRI-related symptoms, complemented with unrelated symptoms) experienced during a working day. We analysed 633 diaries. Exposure categories were defined by strength and type of MRI scanner, using non-MRI shifts as the reference category for statistical analysis. Non-MRI shifts originated from MRI staff who also participated on MRI days, as well as CT radiographers who never worked with MRI. Results Varying per exposure category, symptoms were reported during 16–39% of the MRI work shifts. We observed a positive association between scanner strength and reported symptoms among healthcare and research staff working with closed-bore MRI scanners of 1.5 Tesla (T) and higher (1.5?T OR=1.88; 3.0?T OR=2.14; 7.0?T OR=4.17). This finding was mainly driven by reporting of vertigo and metallic taste. Conclusions The results suggest an exposure-response association between exposure to strong static magnetic fields (and associated motion-induced time-varying magnetic fields) and reporting of transient symptoms on the same day of exposure. Trial registration number 11-032/C

Schaap, Kristel; Christopher-de Vries, Yvette; Mason, Catherine K; de Vocht, Frank; Portengen, Lutzen; Kromhout, Hans

2014-01-01

29

Functional magnetic resonance imaging of eye dominance at 4 tesla.  

PubMed

We studied eye dominance in visual cortex and lateral geniculate nucleus (LGN) using functional magnetic resonance imaging (fMRI) at a very high magnetic field (4 tesla). Eight normal volunteers were studied with fMRI at 4 tesla during alternating monocular visual stimulation. The acquisition was repeated twice in 4 subjects to confirm reproducibility. In addition, magnetic resonance signal intensities during three conditions (right eye stimulation, left eye stimulation, and control condition) were compared to determine whether the observed area was truly or relatively monocular in 2 subjects. In both the individual and group analyses, the anterior striate cortex was consistently activated by the contralateral eye more than the ipsilateral eye. Additionally, we found evidence that there were areas in the bilateral LGN which were more active during the stimulation of the contralateral eye than during the stimulation of the ipsilateral eye. The activated areas were reproducible, and the mean ratio of the overlapping area was 0.71 for the repeated scans. The additional experiment revealed that the area in the anterior visual cortex could be divided into two parts, one truly monocular and the other relatively monocular. Our finding confirmed previous fMRI results at 1.5 tesla showing that eye dominance was observed in the contralateral anterior visual cortex. However, the eye dominance in the visual cortex was found not only in the most anterior area corresponding to the monocular temporal crescent but also in the more posterior area, presumably showing the greater sensitivity of the temporal visual field (nasal retina) as compared with the nasal visual field (temporal retina) in the peripheral visual field (peripheral retina). In addition, it is suggested that the nasotemporal asymmetry of the retina and the visual fields is represented in the LGN as well as in the visual cortex. PMID:11586061

Miki, A; Liu, G T; Englander, S A; van Erp, T G; Bonhomme, G R; Aleman, D O; Liu, C S; Haselgrove, J C

2001-01-01

30

RHQT Nb3Al 15Tesla magnet design study  

Microsoft Academic Search

Feasibility study of 15-Tesla dipole magnets wound with a new copper stabilized RHQT NbâAl Rutherford cable is presented. A new practical long copper stabilized RHQT NbâAl strand is presented, which is being developed and manufactured at the National Institute of Material Science (NIMS) in Japan. It has achieved a non-copper J{sub c} of 1000A\\/mm² at 15 Tesla at 4.2K, with

R. Yamada; G. Ambrosio; E. Barzi; V. Kashikin; A. Kikuchi; I. Novitski; T. Takeuchi; M. Wake; A. Zlobin

2005-01-01

31

Test results of a single aperture 10 tesla dipole model magnet for the Large Hadron Collider  

Microsoft Academic Search

A single aperture dipole magnet has been developed with a design magnetic field of 10 tesla by using Nb-Ti\\/Cu conductor to be operated at 1.8 K in pressurized super fluid helium, The magnet features double shell coil design by using high keystone Rutherford cable and compact non-magnetic steel collars to be adaptable in split\\/symmetric coil\\/collar design for twin aperture dipoles.

Akira Yamamoto; Takakazu Shintomi; Nobuhiro Kimura; Yoshikuni Doi; Tomiyoshi Haruyama; Norio Higashi; Hiromi Hirabayashi; Hiroshi Kawamata; Seog-Whan Kim; Takamitsu M. Kobayashi; Yasuhiro Makida; Toru Ogitsu; Norihito Ohuchi; Ken-ichi Tanaka; Akio Terashima; Kiyosumi Tsuchiya; Hiroshi Yamaoka; Giorgio Brianti; Daniel Leroy; Romeo Perin; Shoichi Mizumaki; Shuichi Kato

1996-01-01

32

Test results of HD1b, an upgraded 16 tesla Nb3Sn dipole magnet  

Microsoft Academic Search

The Superconducting Magnet Group at Lawrence Berkeley National Laboratory has been developing high-field, brittle-superconductor, accelerator magnet technology, in which the conductor's support system can significantly impact conductor performance (as well as magnet training). A recent H-dipole coil test (HD1) achieved a peak bore-field of 16 Tesla, using two, flat-racetrack, double-layer Nb3Sn coils. However, its 4.5 K training was slow, with

A. F. Lietzke; S. E. Bartlett; P. Bish; S. Caspi; D. Dietderich; P. Ferracin; S. A. Gourlay; A. R. Hafalia; C. R. Hannaford; H. Higley; W. Lau; N. Liggins; S. Mattafirri; M. Nyman; G. Sabbi; R. Scanlan; J. Swanson

2005-01-01

33

Radio frequency magnetic field mapping of a 3 Tesla birdcage coil: experimental and theoretical dependence on sample properties.  

PubMed

The RF B(1) distribution was studied, theoretically and experimentally, in phantoms and in the head of volunteers using a 3 T MRI system equipped with a birdcage coil. Agreement between numerical simulation and experiment demonstrates that B(1) distortion at high field can be explained with 3D full-Maxwell calculations. It was found that the B(1) distribution in the transverse plane is strongly dependent on the dielectric properties of the sample. We show that this is a consequence of RF penetration effects combined with RF standing wave effects. In contrast, along the birdcage coil z-axis the B(1) distribution is determined mainly by the coil geometry. In the transverse plane, the region of B(1) uniformity (within 10% of the maximum) was 15 cm with oil, 6 cm with distilled water, 11 cm with saline, and 10 cm in the head. Along z the B(1) uniformity was 9 cm with phantoms and 7 cm in the head. PMID:11477643

Alecci, M; Collins, C M; Smith, M B; Jezzard, P

2001-08-01

34

2 Tesla class magnet fabrication using Bi2212 Ag-sheathed tape  

Microsoft Academic Search

Three test magnets of pancake-shaped coils using Bi-2212 tape were prepared by the wind-and-react technique. At liquid helium\\u000a temperature, 16 pancake coils which were stacked in a volume of l4? ?48?x 75H mm generated a magnetic field of 2.25 Tesla (T), which was within 1% of the calculated B0. The load lines of the magnet at every temperature from 4.2

S. Yuhya; M. Hiraoka

1995-01-01

35

Prospects for 6 to 10 tesla magnets for a TEVATRON upgrade  

SciTech Connect

The first SSC physics is at least 10 years away. An upgrade of the Fermilab Tevatron will ensure the continuity of a vigorous high-energy physics program until the SSC turns on. Three basic proposals are under consideration: /bar p/p at 3 /times/ 10/sup 31/ --Increase luminosity by improvements to the p source. pp at 1 TeV and 2 /times/ 10/sup 32/--Move the main ring to a new tunnel, build a second Tevatron ring, and /bar p/p > 1.5 TeV and 7 /times/ 10/sup 30/--Replace the tevatron with a higher energy ring. The last two options requires about a hundred 6.6-tesla dipoles in addition to a ring of Tevatron strength (4.4 T) magnets. These higher-field magnets are necessary in both rings to lengthen the straight sections in order to realize the collision optics. The third option requires a ring of magnets of 6.6 T or slightly higher to replace the present Tevatron plus a number of special 8--9 tesla magnets. The viability of the high-energy option then depends on the practicality of sizable numbers of reliable 8--9 tesla dipoles as well as 800 6.6-tesla dipoles. The following develops a specification for an 8.8 T dipole, examines the design considerations and reviews the current state of high-field magnet development. 22 figs., 3 tabs.

Mantsch, Paul M.

1988-07-08

36

Nikola Tesla: 145 years of visionary ideas  

Microsoft Academic Search

The paper gives a short review of Tesla's major inventions including the rotating magnetic field, the Tesla coil and transformer, and the power struggle between Edison's direct current systems and the Tesla-Westinghouse alternating current approach. It also looks at some of Tesla's visionary ideas

Jasmina Vujic; Aleksandar Marincic; Milos Ercegovac; Bratislav Milovanovic

2001-01-01

37

Science at 100 Tesla  

NASA Astrophysics Data System (ADS)

Within the last year, Los Alamos National Labs produced magnetic fields of 100 tesla strength non-destructively for the first time. Fields of such a strength open up many new possibilities for condensed matter research. I will present some recent examples of condensed matter physics experiments performed in magnetic fields reaching 100 tesla, which includes recent work on high temperature superconductivity, magnetism and low dimensional materials.

Harrison, Neil

2012-10-01

38

RHQT Nb3Al 15-Tesla magnet design study  

SciTech Connect

Feasibility study of 15-Tesla dipole magnets wound with a new copper stabilized RHQT Nb{sub 3}Al Rutherford cable is presented. A new practical long copper stabilized RHQT Nb{sub 3}Al strand is presented, which is being developed and manufactured at the National Institute of Material Science (NIMS) in Japan. It has achieved a non-copper J{sub c} of 1000A/mm{sup 2} at 15 Tesla at 4.2K, with a copper over non-copper ratio of 1.04, and a filament size less than 50 microns. For this design study a short Rutherford cable with 28 Nb{sub 3}Al strands of 1 mm diameter will be fabricated late this year. The cosine theta magnet cross section is designed using ROXIE, and the stress and strain in the coil is estimated and studied with the characteristics of the Nb{sub 3}Al strand. The advantages and disadvantages of the Nb{sub 3}Al cable are compared with the prevailing Nb{sub 3}Sn cable from the point of view of stress-strain, J{sub c}, and possible degradation of stabilizer due to cabling. The Nb{sub 3}Al coil of the magnet, which will be made by wind and react method, has to be heat treated at 800 degree C for 10 hours. As preparation for the 15 Tesla magnet, a series of tests on strand and Rutherford cables are considered.

Yamada, R.; Ambrosio, G.; Barzi, E.; Kashikin, V.; Kikuchi, A.; Novitski, I.; Takeuchi, T.; Wake, M.; Zlobin, A.; /Fermilab /NIMC, Tsukuba /KEK, Tsukuba

2005-09-01

39

Thirteen tesla magnet constructed with MJR wire  

Microsoft Academic Search

The authors have constructed an insert booster superconducting magnet of 20 mm clear bore and outside diameter of 100 mm and height 130 mm, wound and reacted from the Teledyne patented foraminous layered foil (jelly roll) wire fabricated by low cost, non-rebundled reduction to wire. This magnet was placed inside the 101 mm bore of a NbTi wound solenoid which

M. Siddall; W. McDonald; K. Efferson

1983-01-01

40

High-field 4.23 tesla magnetic resonance imaging: initial experience in turbo-inversion recovery imaging and fMRI physics  

Microsoft Academic Search

High-field magnetic resonance imaging (MRI) offers functional, biochemical and physiological information. High field is advantageous for both fMRI signal generated from deoxyhemoglobin and blood oxygen, and intracellular sodium by inversion recovery MRI imaging. High field MRI was used to image human and primates for sodium MRI imaging.

Rakesh Sharma

2004-01-01

41

Dobutamine stress cardiovascular magnetic resonance at 3 Tesla  

PubMed Central

Purpose The assessment of inducible wall motion abnormalities during high-dose dobutamine-stress cardiovascular magnetic resonance (DCMR) is well established for the identification of myocardial ischemia at 1.5 Tesla. Its feasibility at higher field strengths has not been reported. The present study was performed to prospectively determine the feasibility and diagnostic accuracy of DCMR at 3 Tesla for depicting hemodynamically significant coronary artery stenosis (? 50% diameter stenosis) in patients with suspected or known coronary artery disease (CAD). Materials and methods Thirty consecutive patients (6 women) (66 ± 9.3 years) were scheduled for DCMR between January and May 2007 for detection of coronary artery disease. Patients were examined with a Philips Achieva 3 Tesla system (Philips Healthcare, Best, The Netherlands), using a spoiled gradient echo cine sequence. Technical parameters were: spatial resolution 2 × 2 × 8 mm3, 30 heart phases, spoiled gradient echo TR/TE: 4.5/2.6 msec, flip angle 15°. Images were acquired at rest and stress in accordance with a standardized high-dose dobutamine-atropine protocol during short breath-holds in three short and three long-axis views. Dobutamine was administered using a standard protocol (10 ?g increments every 3 minutes up to 40 ?g dobutamine/kg body weight/minute plus atropine if required to reach target heart rate). The study protocol included administration of 0.1 mmol/kg/body weight Gd-DTPA before the cine images at rest were acquired to improve the image quality. The examination was terminated if new or worsening wall-motion abnormalities or chest pain occurred or when > 85% of age-predicted maximum heart rate was reached. Myocardial ischemia was defined as new onset of wall-motion abnormality in at least one segment. In addition, late gadolinium enhancement (LGE) was performed. Images were evaluated by two blinded readers. Diagnostic accuracy was determined with coronary angiography as the reference standard. Image quality and wall-motion at rest and maximum stress level were evaluated using a four-point scale. Results In 27 patients DCMR was performed successfully, no patient had to be excluded due to insufficient image quality. Twenty-two patients were examined by coronary angiography, which depicted significant stenosis in 68.2% of the patients. Patient-based sensitivity and specificity were 80.0% and 85.7% respectively and accuracy was 81.8%. Interobserver variability for assessment of wall motion abnormalities was 88% (? = 0.760; p < 0.0001). Negative and positive predictive values were 66.7% and 92.3%, respectively. No significant differences in average image quality at rest versus stress for short or long-axis cine images were found. Conclusion High-dose DCMR at 3T is feasible and an accurate method to depict significant coronary artery stenosis in patients with suspected or known CAD.

Kelle, S; Hamdan, A; Schnackenburg, B; Kohler, U; Klein, C; Nagel, E; Fleck, E

2008-01-01

42

A 4 Tesla Superconducting Magnet Developed for a 6 Circle Huber Diffractometer at the XMaS Beamline  

Microsoft Academic Search

We report here on the development and testing of a 4 Tesla cryogen free superconducting magnet designed to fit within the Euler cradle of a 6 circle Huber diffractometer, allowing scattering in both the vertical and horizontal planes. The geometry of this magnet allows the field to be applied in three orientations. The first being along the beam direction, the

P. B. J. Thompson; S. D. Brown; L. Bouchenoire; D. Mannix; D. F. Paul; C. A. Lucas; J. Kervin; M. J. Cooper; P. Arakawa; G. Laughon

2007-01-01

43

Point-contact spectroscopy of the electron-doped cuprate superconductor Pr2-xCexCuO4 in magnetic fields up to 32 tesla  

NASA Astrophysics Data System (ADS)

Tunneling spectra of the normal state of electron-doped cuprates at low temperatures and in magnetic fields higher than the upper critical field (Hc2) have shown evidence of a “pseudogap”. However, to understand if the origin of this pseudogap is the same as the pseudogap observed in hole-doped cuprates and to determine the theoretical model it supports, it is necessary to study the effect of high magnetic fields on this pseudogap. Point contact spectroscopy (PCS) was carried out on junctions between electron doped cuprate Pr2-xCexCuO4 (PCCO, 0.13 < x < 0.17) single crystals and normal metal (Pt-Rh). To probe the normal state at low temperatures (T ˜ 1.5 K), the superconductivity was suppressed by applying high magnetic fields (up to 32 T). These experiments showed that the normal state gap is present for all the dopings, including the overdoped one. These results at high magnetic fields can be interpreted as a combined effect of precursor superconductivity and the presence of disorder in these materials.

Yun, Sunghee; Dhakal, Tara; Tosado, Jacob; Biswas, Amlan; Liang, Bing; Greene, Richard

2006-03-01

44

Design and Evaluation of a Hybrid Radiofrequency Applicator for Magnetic Resonance Imaging and RF Induced Hyperthermia: Electromagnetic Field Simulations up to 14.0 Tesla and Proof-of-Concept at 7.0 Tesla  

PubMed Central

This work demonstrates the feasibility of a hybrid radiofrequency (RF) applicator that supports magnetic resonance (MR) imaging and MR controlled targeted RF heating at ultrahigh magnetic fields (B0?7.0T). For this purpose a virtual and an experimental configuration of an 8-channel transmit/receive (TX/RX) hybrid RF applicator was designed. For TX/RX bow tie antenna electric dipoles were employed. Electromagnetic field simulations (EMF) were performed to study RF heating versus RF wavelength (frequency range: 64 MHz (1.5T) to 600 MHz (14.0T)). The experimental version of the applicator was implemented at B0?=?7.0T. The applicators feasibility for targeted RF heating was evaluated in EMF simulations and in phantom studies. Temperature co-simulations were conducted in phantoms and in a human voxel model. Our results demonstrate that higher frequencies afford a reduction in the size of specific absorption rate (SAR) hotspots. At 7T (298 MHz) the hybrid applicator yielded a 50% iso-contour SAR (iso-SAR-50%) hotspot with a diameter of 43 mm. At 600 MHz an iso-SAR-50% hotspot of 26 mm in diameter was observed. RF power deposition per RF input power was found to increase with B0 which makes targeted RF heating more efficient at higher frequencies. The applicator was capable of generating deep-seated temperature hotspots in phantoms. The feasibility of 2D steering of a SAR/temperature hotspot to a target location was demonstrated by the induction of a focal temperature increase (?T?=?8.1 K) in an off-center region of the phantom. Temperature simulations in the human brain performed at 298 MHz showed a maximum temperature increase to 48.6C for a deep-seated hotspot in the brain with a size of (19×23×32)mm3 iso-temperature-90%. The hybrid applicator provided imaging capabilities that facilitate high spatial resolution brain MRI. To conclude, this study outlines the technical underpinnings and demonstrates the basic feasibility of an 8-channel hybrid TX/RX applicator that supports MR imaging, MR thermometry and targeted RF heating in one device.

Winter, Lukas; Ozerdem, Celal; Hoffmann, Werner; Santoro, Davide; Muller, Alexander; Waiczies, Helmar; Seemann, Reiner; Graessl, Andreas; Wust, Peter; Niendorf, Thoralf

2013-01-01

45

Development of a nano-tesla magnetic field shielded chamber and highly precise AC-susceptibility measurement coil at μK temperatures  

NASA Astrophysics Data System (ADS)

A special sample measurement chamber has been developed to perform experiments at ultralow temperatures and ultralow magnetic field. A high permeability material known as cryoperm 10 and Pb is used to shield the measurement space consisting of the signal detecting set-up and the sample. The detecting setup consists of a very sensitive susceptibility coil wound on OFHC Cu bobbin.

Kumar, Anil; Prakash, Om; Ramakrishanan, S.

2014-04-01

46

A test of a 2 Tesla superconducting transmission line magnet system  

SciTech Connect

Superconducting transmission line magnet test system for an injector accelerator of a staged VLHC proton-proton colliding beam accelerator has been built and operated at Fermilab. The 1.5 m long, twin-aperture, combined function dipole magnet of 2 Tesla field is excited by a single turn 100 kA transmission line superconductor. The 100 kA dc current is generated using dc-dc switching converters powered by a bulk 240 kW supply. A pair of horizontally placed conventional leads facilitates transfer of this current to the magnet transmission line superconductor operating at liquid helium temperature. Fabrication of magnet components and magnet assembly work are described. The magnet test system and its operation are presented, and the performance is summarized.

Piekarz, Henryk; Carcagno, Ruben; Claypool, Brad; Foster, George W.; Hays, Steven L.; Huang, Yuenian; Kashikhin, Vladimir; Malamud, Ernest; Mazur, Peter O.; Nehring, Roger; Oleck, Andrew; Rabehl, Roger; Schlabach, Phil; Sylvester, Cosmore; Velev, Gueorgui; Volk, James; /Fermilab; Wake, Masayoshi; /KEK, Tsukuba

2005-09-01

47

High spatial resolution and temporally resolved T2* mapping of normal human myocardium at 7.0 Tesla: an ultrahigh field magnetic resonance feasibility study.  

PubMed

Myocardial tissue characterization using T(2)(*) relaxation mapping techniques is an emerging application of (pre)clinical cardiovascular magnetic resonance imaging. The increase in microscopic susceptibility at higher magnetic field strengths renders myocardial T(2)(*) mapping at ultrahigh magnetic fields conceptually appealing. This work demonstrates the feasibility of myocardial T(2)(*) imaging at 7.0 T and examines the applicability of temporally-resolved and high spatial resolution myocardial T(2)(*) mapping. In phantom experiments single cardiac phase and dynamic (CINE) gradient echo imaging techniques provided similar T(2)(*) maps. In vivo studies showed that the peak-to-peak B(0) difference following volume selective shimming was reduced to approximately 80 Hz for the four chamber view and mid-ventricular short axis view of the heart and to 65 Hz for the left ventricle. No severe susceptibility artifacts were detected in the septum and in the lateral wall for T(2)(*) weighting ranging from TE = 2.04 ms to TE = 10.2 ms. For TE >7 ms, a susceptibility weighting induced signal void was observed within the anterior and inferior myocardial segments. The longest T(2)(*) values were found for anterior (T(2)(*) = 14.0 ms), anteroseptal (T(2)(*) = 17.2 ms) and inferoseptal (T(2)(*) = 16.5 ms) myocardial segments. Shorter T(2)(*) values were observed for inferior (T(2)(*) = 10.6 ms) and inferolateral (T(2)(*) = 11.4 ms) segments. A significant difference (p = 0.002) in T(2)(*) values was observed between end-diastole and end-systole with T(2)(*) changes of up to approximately 27% over the cardiac cycle which were pronounced in the septum. To conclude, these results underscore the challenges of myocardial T(2)(*) mapping at 7.0 T but demonstrate that these issues can be offset by using tailored shimming techniques and dedicated acquisition schemes. PMID:23251708

Hezel, Fabian; Thalhammer, Christof; Waiczies, Sonia; Schulz-Menger, Jeanette; Niendorf, Thoralf

2012-01-01

48

High Spatial Resolution and Temporally Resolved T2* Mapping of Normal Human Myocardium at 7.0 Tesla: An Ultrahigh Field Magnetic Resonance Feasibility Study  

PubMed Central

Myocardial tissue characterization using T2* relaxation mapping techniques is an emerging application of (pre)clinical cardiovascular magnetic resonance imaging. The increase in microscopic susceptibility at higher magnetic field strengths renders myocardial T2* mapping at ultrahigh magnetic fields conceptually appealing. This work demonstrates the feasibility of myocardial T2* imaging at 7.0 T and examines the applicability of temporally-resolved and high spatial resolution myocardial T2* mapping. In phantom experiments single cardiac phase and dynamic (CINE) gradient echo imaging techniques provided similar T2* maps. In vivo studies showed that the peak-to-peak B0 difference following volume selective shimming was reduced to approximately 80 Hz for the four chamber view and mid-ventricular short axis view of the heart and to 65 Hz for the left ventricle. No severe susceptibility artifacts were detected in the septum and in the lateral wall for T2* weighting ranging from TE?=?2.04 ms to TE?=?10.2 ms. For TE >7 ms, a susceptibility weighting induced signal void was observed within the anterior and inferior myocardial segments. The longest T2* values were found for anterior (T2*?=?14.0 ms), anteroseptal (T2*?=?17.2 ms) and inferoseptal (T2*?=?16.5 ms) myocardial segments. Shorter T2* values were observed for inferior (T2*?=?10.6 ms) and inferolateral (T2*?=?11.4 ms) segments. A significant difference (p?=?0.002) in T2* values was observed between end-diastole and end-systole with T2* changes of up to approximately 27% over the cardiac cycle which were pronounced in the septum. To conclude, these results underscore the challenges of myocardial T2* mapping at 7.0 T but demonstrate that these issues can be offset by using tailored shimming techniques and dedicated acquisition schemes.

Hezel, Fabian; Thalhammer, Christof; Waiczies, Sonia; Schulz-Menger, Jeanette; Niendorf, Thoralf

2012-01-01

49

Design study of 15Tesla RHQT Nb3Al block type dipole magnet  

Microsoft Academic Search

The design study of the block type 15-Tesla RHQT NbâAl dipole magnet, and its merits over NbâSn magnets are presented. The copper stabilized RHQT NbâAl strand is now becoming commercially available for the application to the accelerator magnets. A 1 mm diameter RHQT NbâAl strand with filament size about 50 μ, non-copper Jc about 1000 A\\/mm² at 15 Tesla at

R. Yamada; G. Ambrosio; E. Barzi; V. Kashikin; A. Kikuchi; I. Novitski; T. Takeuchi; M. Wake; A. Zlobin

2005-01-01

50

[3 Tesla MRI: successful results with higher field strengths].  

PubMed

The recent development of 3 Tesla MRI (3T MRI) has been fueled by promise of increased signal-to-noise ratio(SNR). Many are excited about the opportunity to not only use the increased SNR for clearer images, but also the chance to exchange it for better resolution or faster scans. These possibilities have caused a rapid increase in the market for 3T MRI, where the faster scanning tips an already advantageous economic outlook in favor of the user. As a result, the global market for 3T has grown from a research only market just a few years ago to an ever-increasing clinically oriented customer base. There are, however, significant obstacles to 3T MRI presented by the physics at higher field strengths. For example, the T1 relaxation times are prolonged with increasing magnet field strength. Further, the increased RF-energy deposition (SAR), the larger the chemical shift and the stronger susceptibility effect have to be considered as challenges. It is critical that one looks at both the advantages and disadvantages of using 3T. While there are many issues to address aand a number of different methods for doing so, to properly tackle each of these concerns will take time and effort on the part od researchers and clinicians. The optimization of 3T MRI scanning will have to be a combined effort, though much of the work to date has been in neuroimaging. Multiple applications have been explored in addition to clinical anatomical imaging, where resolution is improved showing structure in the brain never seen before in human MRI. Body and cardiac imaging provide a great challenge but are also achievable at 3T. As an example, the full range of clinical applications currently achieved on today's state-of-the-art 1.5T cardiac MR scanners has also been demonstrated at 3T. In the body, the full range of contrast is available over large fields of view allowing whole liver studies in the clinic or, as needed, one may choose a smaller field of view for high-resolution imaging of the pancreas. The ability to increase resolution for musculoskeletal imaging has provided previously unseen detail. Bone structure, cartilage, and tendons and ligaments can be clearly visualized and pathology more easily detected due to an increased image quality. As the increase in field strength continues, a push to look at 7T has begun. The design philosophy is to keep the system as similar as possible, while changing only the frequency-dependent components. To date, both animal and human imaging have been performed on a whole body 7T scanner. Results show promise for both detailed imaging and functional MRI, but the road ahead is too long to be able to predict where it will end. The move toward higher field strengths is an exciting adventure in which 3T plays the role of trailblazer. PMID:14997868

Schmitt, F; Grosu, D; Mohr, C; Purdy, D; Salem, K; Scott, K T; Stoeckel, B

2004-01-01

51

MR imaging at high magnetic fields  

Microsoft Academic Search

Recently, more investigators have been applying higher magnetic field strengths (3–4 Tesla) in research and clinical settings. Higher magnetic field strength is expected to afford higher spatial resolution and\\/or a decrease in the length of total scan time due to its higher signal intensity. Besides MR signal intensity, however, there are several factors which are magnetic field dependent, thus the

Masaya Takahashi; Hidemasa Uematsu; Hiroto Hatabu

2003-01-01

52

Extreme Material Physical Properties and Measurements above 100 tesla  

Microsoft Academic Search

The National High Magnetic Field Laboratory (NHMFL) Pulsed Field Facility (PFF) at Los Alamos National Laboratory (LANL) offers extreme environments of ultra high magnetic fields above 100 tesla by use of the Single Turn method as well as fields approaching 100 tesla with more complex methods. The challenge of metrology in the extreme magnetic field generating devices is complicated by

Charles Mielke

2011-01-01

53

Organic Superconductors at Extremely High Magnetic Fields  

ScienceCinema

Intense magnetic fields are an essential tool for understanding layered superconductors. Fundamental electronic properties of organic superconductors are revealed in intense (60 tesla) magnetic fields. Properties such as the topology of the Fermi surface and the nature of the superconducting order parameter are revealed. With modest maximum critical temperatures {approx}13K the charge transfer salt organic superconductors prove to be incredibly valuable materials as their electronically clean nature and layered (highly anisotropic) structures yield insights to the high temperature superconductors. Observation of de Haas-van Alphen and Shubnikov-de Haas quantum oscillatory phenomena, magnetic field induced superconductivity and re-entrant superconductivity are some of the physical phenomena observed in the charge transfer organic superconductors. In this talk, I will discuss the nature of organic superconductors and give an overview of the generation of intense magnetic fields; from the 60 tesla millisecond duration to the extreme 1000 tesla microsecond pulsed magnetic fields.

54

Magnetic Fields  

NSDL National Science Digital Library

Students visualize the magnetic field of a strong permanent magnet using a compass. The lesson begins with an analogy to the effect of the earth's magnetic field on a compass. Students see the connection that the compass simply responds to the earth's magnetic field since it is the closest, strongest field, and therefore the compass will respond to the field of the permanent magnets, allowing them the ability to map the field of that magnet in the activity. This information will be important in designing a solution to the grand challenge in activity 4 of the unit.

Vu Bioengineering Ret Program

55

Advanced High-Field Coil Designs: 20 TESLA.  

National Technical Information Service (NTIS)

This study of the technology required for producing large high-field coils has shown that, with some extensions to our present technological base, feasible designs are achievable. The resulting magnets could well make a paramount contribution to the natio...

R. W. Hoard D. N. Cornish R. M. Scanlan J. P. Zbasnik R. L. Leber

1983-01-01

56

High field superconducting magnets  

NASA Technical Reports Server (NTRS)

A superconducting magnet includes an insulating layer disposed about the surface of a mandrel; a superconducting wire wound in adjacent turns about the mandrel to form the superconducting magnet, wherein the superconducting wire is in thermal communication with the mandrel, and the superconducting magnet has a field-to-current ratio equal to or greater than 1.1 Tesla per Ampere; a thermally conductive potting material configured to fill interstices between the adjacent turns, wherein the thermally conductive potting material and the superconducting wire provide a path for dissipation of heat; and a voltage limiting device disposed across each end of the superconducting wire, wherein the voltage limiting device is configured to prevent a voltage excursion across the superconducting wire during quench of the superconducting magnet.

Hait, Thomas P. (Inventor); Shirron, Peter J. (Inventor)

2011-01-01

57

Reproducibility of subregional trabecular bone micro-architectural measures derived from 7-Tesla magnetic resonance images  

PubMed Central

High-resolution magnetic resonance imaging (MRI) of trabecular bone combined with quantitative image analysis represents a powerful technique to gain insight into trabecular bone micro-architectural derangements in osteoporosis and osteoarthritis. The increased signal-to-noise ratio of ultra high-field MR (?7 Tesla) permits images to be obtained with higher resolution and/or decreased scan time compared to scanning at 1.5/3T. In this small feasibility study, we show high measurement precision for subregional trabecular bone micro-architectural analysis performed on 7T knee MR images. The results provide further support for the use of trabecular bone measures as biomarkers in clinical studies of bone disorders.

Wang, Ligong; Liang, Guoyuan; Babb, James S.; Saha, Punam K.; Regatte, Ravinder R.

2013-01-01

58

Design study of 15-Tesla RHQT Nb3Al block type dipole magnet  

SciTech Connect

The design study of the block type 15-Tesla RHQT Nb{sub 3}Al dipole magnet, and its merits over Nb{sub 3}Sn magnets are presented. The copper stabilized RHQT Nb{sub 3}Al strand is now becoming commercially available for the application to the accelerator magnets. A 1 mm diameter RHQT Nb{sub 3}Al strand with filament size about 50 {mu}, non-copper Jc about 1000 A/mm{sup 2} at 15 Tesla at 4.2K, copper ratio of 50%, can now be produced over several hundred meters. The stress and strain characteristics of the Nb{sub 3}Al strand are superior to the Nb{sub 3}Sn strand. Another advantage is that it can tolerate a longitudinal strain up to 0.55%. The RHQT Nb{sub 3}Al Rutherford cable will have less chance of contamination of the stabilizer, compared to Nb{sub 3}Sn cable. These characteristics of the RHQT Nb{sub 3}Al will be beneficial for designing and producing 15-Tesla dipole magnets. An example 15-Tesla magnet cross section, utilizing the RHQT Nb{sub 3}Sn strand is presented. A systematic investigation on RHQT Nb{sub 3}Al strands, its Rutherford cables, and building a small racetrack magnet for cable testing are proposed.

Yamada, R.; Ambrosio, G.; Barzi, E.; Kashikin, V.; Kikuchi, A.; Novitski, I.; Takeuchi, T.; Wake, M.; Zlobin, A.; /Fermilab /NIMC, Tsukuba /KEK, Tsukuba

2005-09-01

59

Development of the 19 T high field magnet system  

Microsoft Academic Search

A high field magnet system, up to 19 tesla at 1.8K, with magnet bore of 75mm was developed. The magnet consists of Nb3Sn solenoids (3 sections) and NbTi solenoids (2 sections). A liquid helium vessel is divided into two parts (4.2K upper part and 1.8K lower part) by a fiberglass reinforced plastics separator. The central field is 17 tesla at

T. Kamikado; M. Taneda; O. Ozaki; M. Sugimoto; Y. Murakami; M. Yoshikawa; K. Matsumoto; R. Ogawa; Y. Kawate

1994-01-01

60

6. 4 tesla dipole magnet for the SSC. Revision  

SciTech Connect

A design is presented for a dipole magnet suitable for the proposed SSC facility. Test results are given for model magnets of this design 1 m long and 4.5 m long. Flattened wedge-shaped cables (''keystoned'') are used in a graded, two-layer ''cos theta'' configuration with three wedges to provide sufficient field uniformity and mechanical rigidity. Stainless steel collars 15 mm in radial depth, fastened with rectangular keys, provide structural support, and there is a ''cold'' iron flux return. The outer-layer cable has 30 strands of 0.648 mm diameter NbTi multifilamentary wire with Cu/S.C. = 1.8, and the inner has 23 strands of 0.808 mm diameter wire with Cu/S.C. = 1.3. Performance data are given, including training behavior, winding stresses, collar deformation, and field uniformity. 10 refs., 11 figs.

Taylor, C.E.; Caspi, S.; Gilbert, W.; Hassenzahl, W.; Meuser, R.; Mirk, K.; Peters, C.; Scanlan, R.; Dahl, P.; Cottingham, J.

1985-08-01

61

6. 4 Tesla dipole magnet for the SSC  

SciTech Connect

A design is presented for a dipole magnet suitable for the proposed SSC facility. Test results are given for model magnets of this design 1 m long and 4.5 m long. Flattened wedge-shaped cables (''keystoned'') are used in a graded, two-layer ''cos theta'' configuration with three wedges to provide sufficient field uniformity and mechanical rigidity. Stainless steel collars 15 mm wide, fastened with rectangular keys, provide structural support, and there is a ''cold'' iron flux return. The outer-layer cable has 30 strands of 0.0255 in. dia NbTi multifilamentary wire with Cu/S.C. = 1.8, and the inner has 23 strands of .0318 in. dia wire with Cu/S.C. = 1.3. Performance data is given including training behavior, winding stresses, collar deformation, and field uniformity.

Taylor, C.E.; Caspi, S.; Gilbert, W.; Meuser, R.; Mirk, K.; Peters, C.; Scanlan, R.; Dahl, P.; Cottingham, J.; Hassenzahl, W.

1985-05-01

62

Progress in the manufacture of the cable-in-conduit Nb3Sn outsert coils for the 45 tesla hybrid magnet  

NASA Astrophysics Data System (ADS)

The 45 Tesla Hybrid Magnet is being built in a collaborative effort between the National High Magnetic Field Laboratory at Florida State University and the Francis Bitter National Magnet Laboratory at the Massachusetts Institute of Technology. The Hybrid Magnet combines a resistive insert magnet with two Nb3Sn and one NbTi superconducting cable-in-conduit outsert coil to produce the required field on axis. The Nb3Sn outsert coils are being built at Intermagnetics General Corporation under contract with FSU. A design summary for the entire 100 MJ outsert magnet is presented. The design criteria and manufacturing status for the two Nb3Sn outsert coils are described.

Painter, Thomas A.; Miller, John R.; Summers, Leonard T.; Bonito-Oliva, Alessandro; Devernoe, Alan L.; Ciancetta, Gary M.; King, Martin J.; Bascunan, Juan; Rutman, Grigory; Schaedler, Robert M.

1994-07-01

63

Progress in the manufacture of the cable-in-conduit Nb{sub 3}Sn outsert coils for the 45 Tesla Hybrid Magnet  

SciTech Connect

The 45 Tesla Hybrid Magnet is being built in a collaborative effort between the National High Magnetic Field Laboratory at Florida State University and the Francis Bitter National Magnet Laboratory at the Massachusetts Institute of Technology. The Hybrid Magnet combines a resistive insert magnet with two Nb3Sn and one NbTi superconducting cable-in-conduit outsert coil to produce the required field on axis. The Nb3Sn outsert coils are being built at Intermagnetics General Corporation under contract with FSU. A design summary for the entire 100 MJ outsert magnet is presented. The design criteria and manufacturing status for the two Nb3Sn outsert coils are described.

Painter, T.A.; Miller, J.R.; Summers, L.T. [Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab.] [and others] [Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab.; and others

1994-07-01

64

Magnetic Fields  

NSDL National Science Digital Library

This page and its annex describes, in trivial terms, the physics of magnetic fields and the history of its discovery. Included is the work of Halley, Oersted, Ampere and Maxwell. It also describes a way of demonstrating it in the classroom, using a vu-graph projector. Later sections #5, #5a and #6 extend this to magnetic field lines and electromagnetism.

Stern, David

2005-01-04

65

Magnetic resonance imaging systems: evaluation of 1.5-Tesla systems.  

PubMed

Magnetic resonance imaging (MRI) systems manipulate magnetic fields and radio-frequency signals to create diagnostic images of human anatomy. An MR system is an essential clinical tool, but the cost of buying and installing one is high, so it's crucial that hospitals choose a model carefully. The selection process is made more complex by the numerous options available: different field strengths, gradient systems, coils, and channels, to name just a few. Also, some systems are better than others at facilitating specialized imaging, such as breast and cardiac studies. Our Evaluation is intended to help clarify the choices. We tested three 1.5-tesla systems from three suppliers--GE, Siemens, and Toshiba. We rate the systems for two different uses: inpatient imaging (performed in hospitals) and outpatient imaging (most often performed in imaging centers). For inpatient facilities, which are likely to have less responsive patients and to treat more complex medical problems, the most important purchase considerations will be patient positioning features, advanced imaging capabilities, and system integration. For outpatient facilities, the ability to perform routine exams efficiently and comfortably will be most important. We also provide separate ratings for each system's ability to meet the needs of three specialized applications--breast imaging, cardiac imaging, and functional MRI. PMID:16893049

2006-06-01

66

Focused tight dressing does not prevent cochlear implant magnet migration under 1.5 Tesla MRI.  

PubMed

We report a retrospective case of inner magnet migration, which occurred after 1.5 Tesla MRI scanning in an adult recipient of a bilateral cochlear implant (CI) despite a focused head dressing. The patient, bilaterally implanted with Nucleus 5 CIs (Cochlear LTD, Sydney, Australia), underwent a 1.5 Tesla cholangio-MRI scan for biliary duct pathology. In subsequent days, a focal skin alteration appeared over the left inner coil. Plain skull radiographs showed partial magnet migration on the left side. Surgical exploration confirmed magnet twisting; the magnet was effectively repositioned. Left CI performance was restored to pre-migration level. The wound healed without complications. Thus, focused dressing does not prevent magnet migration in CI recipients undergoing 1.5 Tesla MRI. All patients should be counselled on this potential complication. A minor surgical procedure is required to reposition the magnet. Nevertheless, timely diagnosis is necessary to prevent skin breakdown and subsequent device contamination. Plain skull radiograph is very effective in identifying magnet twisting; it should be performed systematically after MRI or minimally on all suspected cases. PMID:23853406

Cuda, D; Murri, A; Succo, G

2013-04-01

67

High Field Solenoid Magnets for Muon Cooling  

Microsoft Academic Search

Magnets made with high-temperature superconducting (HTS) coils operating at low temperatures have the potential to produce extremely high fields for use in accelerators and beam lines. The specific application of interest that we are proposing is to use a very high field (of the order of 50 Tesla) solenoid to provide a very small beta region for the final stages

S. A. Kahn; M. Alsharo; P. Hanlet; R. P. Johnson; M. Kuchnir; D. Newsham; R. C. Gupta; R. B. Palmer; E. Willen

68

High magnetic field effects on human deoxygenated hemoglobin light absorption  

Microsoft Academic Search

The effect of high static magnetic field on human deoxyhemoglobin spectrophotometric characteristics is studied. Five samples of partially deoxygenated hemoglobin in aqueous solution were tested. Magnetic field was applied in steps of 2 T (tesla), from 0 to 18 T. Spectral analysis showed a higher light absorption at wavelengths of 546 nm and at 581 nm. The applied magnetic field

Mauricy Motta; Yousef Haik; Abolghasem Gandhari; Ching-Jen Chen

1998-01-01

69

High-Field Magnetization of DY2O3.  

National Technical Information Service (NTIS)

The magnetization of powdered samples of Dy2O3 has been measured at temperatures between 1.45 deg and 4.2 K, in applied magnetic fields ranging to 7 Teslas. A linear dependence of magnetization on applied field is observable in high field region, the slop...

D. J. Flood

1974-01-01

70

Team one (GA/MCA) effort of the DOE 12 Tesla Coil Development Program. 12 Tesla ETF toroidal field coil helium bath cooled NbTi alloy concept  

SciTech Connect

This report presents the conceptual design of an ETF compatible toroidal field coil, employing helium bath cooled NbTi alloy conductor. The ten TF-coil array generates a peak field of 11-1/2 tesla at 2.87 m radius, corresponding to a major axis field of 6.1 tesla. The 10 kA conductor is an uninsulated, unsoldered Rutherford cable, employing NbTiTa ally as developed in Phase I of this effort. The conductor is encased within a four element frame of stainless steel strips to provide hoop and bearing load support.

Not Available

1980-07-01

71

Aligning Paramecium caudatum with Static Magnetic Fields  

Microsoft Academic Search

As they negotiate their environs, unicellular organisms adjust their swimming in response to various physical fields such as temperature, chemical gradients, and electric fields. Because of the weak magnetic properties of most biological materials, however, they do not respond to the earth’s magnetic field (5×10?5 Tesla) except in rare cases. Here, we show that the trajectories of Paramecium caudatum align

Karine Guevorkian; James M. Valles

2006-01-01

72

Magnetic resonance of the pulmonary parenchyma: Initial experience at 0.6 Tesla  

Microsoft Academic Search

Twenty-one patients with a variety of pulmonary parenchymal abnormalities were imaged by MR utilizing 0.6 Tesla superconducting\\u000a magnet. Because of the relative paucity of protons in the pulmonary parenchyma, there is minimal MR signal from normal lungs.\\u000a Parenchymal abnormalities, however, are almost invariably associated with increased proton density in the pulmonary parenchyma.\\u000a Because of this, abnormalities were apparent on MR

Peter B. O'Donovan; Jeffrey S. Ross

1986-01-01

73

Application of the double relaxation oscillation superconducting quantum interference device sensor to micro-tesla 1H nuclear magnetic resonance experiments  

Microsoft Academic Search

We developed an ultra-low field (ULF)-nuclear magnetic resonance (NMR) measurement system capable of working with a measurement field (Bm) of several micro-tesla and performed basic NMR studies with a double relaxation oscillation superconducting quantum interference device (DROS) instead of conventional dc-SQUIDs. DROS is a SQUID sensor utilizing a relaxation oscillation between a dc-SQUID and a relaxation circuit; the new unit

Chan Seok Kang; Kiwoong Kim; Seong-Joo Lee; Seong-Min Hwang; Jin-Mok Kim; Kwon Kyu Yu; Hyukchan Kwon; Sang Kil Lee; Yong-Ho Lee

2011-01-01

74

Collective cyclotron modes in high-mobility two-dimensional hole systems in GaAs - (Ga, Al)As heterojunctions: II. Experiments at magnetic fields of up to forty Tesla  

Microsoft Academic Search

The cyclotron resonance of very high-mobility holes in GaAs - (Ga, Al)As heterojunctions grown on (111), (311) and (100) substrates has been studied in high magnetic fields of up to 40 T. As the temperature is increased from 0953-8984\\/9\\/23\\/012\\/img11 to 0953-8984\\/9\\/23\\/012\\/img12, the cyclotron resonance is found to shift to lower magnetic fields, the size of shift depending on the cyclotron

B. E. Cole; W. Batty; J. Singleton; J. M. Chamberlain; L. Li; L. van Bockstal; Y. Imanaka; Y. Shimamoto; N. Miura; F. M. Peeters; M. Henini; T. Cheng

1997-01-01

75

In vivo estimation of bone stiffness at the distal femur and proximal tibia using ultra-high-field 7-Tesla magnetic resonance imaging and micro-finite element analysis.  

PubMed

The goal of this study was to demonstrate the feasibility of using 7-Tesla (7T) magnetic resonance imaging (MRI) and micro-finite element analysis (µFEA) to evaluate mechanical and structural properties of whole, cortical, and trabecular bone at the distal femur and proximal tibia in vivo. 14 healthy subjects were recruited (age 40.7 ± 15.7 years). The right knee was scanned on a 7T MRI scanner using a 28 channel-receive knee coil and a three-dimensional fast low-angle shot sequence (TR/TE 20 ms/5.02 ms, 0.234 mm × 0.234 mm × 1 mm, 80 axial images, 7 min 9 s). Bone was analyzed at the distal femoral metaphysis, femoral condyles, and tibial plateau. Whole, cortical, and trabecular bone stiffness was computed using µFEA. Bone volume fraction (BVF), bone areas, and cortical thickness were measured. Trabecular bone stiffness (933.7 ± 433.3 MPa) was greater than cortical bone stiffness (216 ± 152 MPa) at all three locations (P < 0.05). Across locations, there were no differences in bone stiffness (whole, cortical, or trabecular). Whole, cortical, and trabecular bone stiffness correlated with BVF (R ? 0.69, P < 0.05) and inversely correlated with corresponding whole, cortical, and trabecular areas (R ? -0.54, P < 0.05), but not with cortical thickness (R < -0.11, P > 0.05). Whole, cortical, and trabecular stiffness correlated with body mass index (R ? 0.62, P < 0.05). In conclusion, at the distal femur and proximal tibia, trabecular bone contributes 66-74% of whole bone stiffness. 7T MRI and µFEA may be used as a method to provide insight into how structural properties of cortical or trabecular bone affect bone mechanical competence in vivo. PMID:22124539

Chang, Gregory; Rajapakse, Chamith S; Babb, James S; Honig, Stephen P; Recht, Michael P; Regatte, Ravinder R

2012-03-01

76

In vivo estimation of bone stiffness at the distal femur and proximal tibia using ultra-high-field 7-Tesla magnetic resonance imaging and micro-finite element analysis  

PubMed Central

The goal of this study was to demonstrate the feasibility of using 7-Tesla (7T) magnetic resonance imaging (MRI) and micro-finite element analysis (?FEA) to evaluate mechanical and structural properties of whole, cortical, and trabecular bone at the distal femur and proximal tibia in vivo. 14 healthy subjects were recruited (age 40.7 ± 15.7 years). The right knee was scanned on a 7T MRI scanner using a 28 channel-receive knee coil and a three-dimensional fast low-angle shot sequence (TR/TE 20 ms/5.02 ms, 0.234 mm × 0.234 mm × 1 mm, 80 axial images, 7 min 9 s). Bone was analyzed at the distal femoral metaphysis, femoral condyles, and tibial plateau. Whole, cortical, and trabecular bone stiffness was computed using ?FEA. Bone volume fraction (BVF), bone areas, and cortical thickness were measured. Trabecular bone stiffness (933.7 ± 433.3 MPa) was greater than cortical bone stiffness (216 ± 152 MPa) at all three locations (P < 0.05). Across locations, there were no differences in bone stiffness (whole, cortical, or trabecular). Whole, cortical, and trabecular bone stiffness correlated with BVF (R ? 0.69, P < 0.05) and inversely correlated with corresponding whole, cortical, and trabecular areas (R ? ?0.54, P < 0.05), but not with cortical thickness (R < ?0.11, P > 0.05). Whole, cortical, and trabecular stiffness correlated with body mass index (R ? 0.62, P < 0.05). In conclusion, at the distal femur and proximal tibia, trabecular bone contributes 66–74% of whole bone stiffness. 7T MRI and ?FEA may be used as a method to provide insight into how structural properties of cortical or trabecular bone affect bone mechanical competence in vivo.

Rajapakse, Chamith S.; Babb, James S.; Honig, Stephen P.; Recht, Michael P.; Regatte, Ravinder R.

2013-01-01

77

The 20 MW50 mm bore diameter magnet of the Grenoble High Magnetic Field Laboratory  

Microsoft Academic Search

A 30 Tesla-20 MW magnet with a 50 mm bore was set into operation at the Grenoble High Magnetic Field Laboratory (GHMFL) in April 1998. It is made of two 10 MW magnets. The inner magnet is composed of a series of 10 helices, electrically in parallel with two thin Bitter coils connected in series. We give the specifications of

G. Aubert; F. Debray; W. Joss; H. Jongbloets; M. Ohl

2000-01-01

78

Novel magnetic textures in SrCu2(BO3)2 from magnetostriction up to 97.4 tesla  

NASA Astrophysics Data System (ADS)

Quantum magnets are model systems wherein strongly frustrated spin interactions generate a variety of exotic magnetic phases of current interest, including quantum spin ices, spin liquids, spin supersolids and complex magnetic superstructures. SrCu2(BO3)2, the only classic realization of the spin-1/2 Heisenberg antiferromagnet in the Shastry-Sutherland (orthogonal spin dimer) lattice is known to exhibit numerous magnetization plateaus due formation of stripe-like magnetic textures in high fields. However, the fine structure of these plateaus remains controversial on both experimental and theoretical fronts due to the existing limits for achievable magnetic fields in the laboratory, the sensitivity of current magnetization techniques, and the uncontrolled nature of available theoretical approaches for highly frustrated magnetic lattices. This talk will describe how we probe magnetic textures in SrCu2(BO3)2 via a recently-developed magnetostriction technique based on optical fiber Bragg gratings [1]. We achieve microstrain (nm-resolution) sensitivity in ultrahigh pulsed fields to 97.4 T using the NHMFL 100 tesla multi-pulse magnet system [2]. The magnetostriction data reveal fine structure corresponding to all magnetization plateaus, and a significant lattice response to the long-predicted 1/2-saturation plateau at 82 T, as well as a new feature at 73.6 T that we attribute to a never before observed structure corresponding to 2/5 of magnetization saturation [3]. These data are complemented by simultaneous magnetocaloric-effect measurements, and are supported by numerical results obtained using a controlled density matrix renormalization group method.[4pt] [1] Daou R. et al., Rev. Sci. Instrum. 81, 033909 (2010).[0pt] [2] Sims J.R., et al. IEEE Trans. Appl. Supercond. 18, 587-591 (2008).[0pt] [3] M. Jaime et al., submitted. In collaboration with R. Daou, S.A. Crooker, F. Weickert, A. Uchida, A. Feiguin, C.D. Batista, H. Dabkowska, and B. Gaulin.

Jaime, Marcelo

2012-02-01

79

Ultrahigh-Field MRI in Human Ischemic Stroke - a 7 Tesla Study  

PubMed Central

Introduction Magnetic resonance imaging (MRI) using field strengths up to 3 Tesla (T) has proven to be a powerful tool for stroke diagnosis. Recently, ultrahigh-field (UHF) MRI at 7 T has shown relevant diagnostic benefits in imaging of neurological diseases, but its value for stroke imaging has not been investigated yet. We present the first evaluation of a clinically feasible stroke imaging protocol at 7 T. For comparison an established stroke imaging protocol was applied at 3 T. Methods In a prospective imaging study seven patients with subacute and chronic stroke were included. Imaging at 3 T was immediately followed by 7 T imaging. Both protocols included T1-weighted 3D Magnetization-Prepared Rapid-Acquired Gradient-Echo (3D-MPRAGE), T2-weighted 2D Fluid Attenuated Inversion Recovery (2D-FLAIR), T2-weighted 2D Fluid Attenuated Inversion Recovery (2D-T2-TSE), T2* weighted 2D Fast Low Angle Shot Gradient Echo (2D-HemoFLASH) and 3D Time-of-Flight angiography (3D-TOF). Results The diagnostic information relevant for clinical stroke imaging obtained at 3 T was equally available at 7 T. Higher spatial resolution at 7 T revealed more anatomical details precisely depicting ischemic lesions and periinfarct alterations. A clear benefit in anatomical resolution was also demonstrated for vessel imaging at 7 T. RF power deposition constraints induced scan time prolongation and reduced brain coverage for 2D-FLAIR, 2D-T2-TSE and 3D-TOF at 7 T versus 3 T. Conclusions The potential of 7 T MRI for human stroke imaging is shown. Our pilot study encourages a further evaluation of the diagnostic benefit of stroke imaging at 7 T in a larger study.

Bauer, Miriam; Stengl, Katharina L.; Mutke, Matthias A.; Tovar-Martinez, Elena; Wuerfel, Jens; Endres, Matthias; Niendorf, Thoralf; Sobesky, Jan

2012-01-01

80

3.0 Tesla vs 1.5 Tesla breast magnetic resonance imaging in newly diagnosed breast cancer patients  

PubMed Central

AIM: To compare 3.0 Tesla (T) vs 1.5T magnetic resonance (MR) imaging systems in newly diagnosed breast cancer patients. METHODS: Upon Institutional Review Board approval, a Health Insurance Portability and Accountability Act-compliant retrospective review of 147 consecutive 3.0T MR examinations and 98 consecutive 1.5T MR examinations in patients with newly diagnosed breast cancer between 7/2009 and 5/2010 was performed. Eleven patients who underwent neoadjuvant chemotherapy in the 3.0T group were excluded. Mammographically occult suspicious lesions (BIRADS Code 4 and 5) additional to the index cancer in the ipsilateral and contralateral breast were identified. Lesion characteristics and pathologic diagnoses were recorded, and results achieved with both systems compared. Statistical significance was analyzed using Fisher’s exact test. RESULTS: In the 3.0T group, 206 suspicious lesions were identified in 55% (75/136) of patients and 96% (198/206) of these lesions were biopsied. In the 1.5T group, 98 suspicious lesions were identified in 53% (52/98) of patients and 90% (88/98) of these lesions were biopsied. Biopsy results yielded additional malignancies in 24% of patients in the 3.0T group vs 14% of patients in the 1.5T group (33/136 vs 14/98, P = 0.07). Average size and histology of the additional cancers was comparable. Of patients who had a suspicious MR imaging study, additional cancers were found in 44% of patients in the 3.0T group vs 27% in the 1.5T group (33/75 vs 14/52, P = 0.06), yielding a higher positive predictive value (PPV) for biopsies performed with the 3.0T system. CONCLUSION: 3.0T MR imaging detected more additional malignancies in patients with newly diagnosed breast cancer and yielded a higher PPV for biopsies performed with the 3.0T system.

Butler, Reni S; Chen, Christine; Vashi, Reena; Hooley, Regina J; Philpotts, Liane E

2013-01-01

81

Experiences with functional magnetic resonance imaging at 1 tesla  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) has been performed on a standard 1 T system using a pulse sequence developed to utilize blood oxygen level dependent (BOLD) contrast and an oV-line analysis routine using correlation techniques. The sequence and the data analysis routine have been validated by reproducing the conventional hand movement paradigm studies reported by numerous other workers. Our work

A P JONES; D G HUGHES; D S BRETTLE; L ROBINSON; J R SYKES; Q AZIZ; S HAMDY; D G THOMPSON; S W G DERBYSHIRE; A C N CHEN

1998-01-01

82

30 Tesla hybrid magnet facility at the Francis bitter national magnet laboratory, Massachusetts Institute of Technology  

Microsoft Academic Search

The design, construction and testing of a hybrid magnet system which provides fields up to 30 T is described. The system consists of a superconducting magnet which generates 7.5 T in a 40 cm bore and a family of watercooled insert magnets operating at 10 mw. The superconducting magnet has an overall current density of nearly 6500 A\\/cm² and a

M. J. Leupold; J. R. Hale; Y. Iwasa; L. G. Rubin; R. J. Weggel

1981-01-01

83

NMR probes for measuring magnetic fields and field dynamics in MR systems  

Microsoft Academic Search

High-resolution magnetic field probes based on pulsed liquid- state NMR are presented. Static field measurements with an error of 10 nanotesla or less at 3 tesla are readily obtained in 100 ms. The further ability to measure dynamic magnetic fields results from using small (! 1 ! L) droplets of MR-active liquid surrounded by susceptibility-matched materials. The conse- quent high

Nicola De Zanche; Christoph Barmet; Jurek A. Nordmeyer-Massner; Klaas P. Pruessmann

2008-01-01

84

Tests on Mutagenic Effects of Strong Magnetic Fields.  

National Technical Information Service (NTIS)

Studies on effects of magnetic fields on Tradescantia included pink stamen hair mutations, pollen abortion, and micronuclei formation in the tetrad stages of pollen production. Exposures were made using permanent magnets for fields up to 0.7 tesla, an ele...

J. W. Baum L. A. Schairer K. L. Lindahl

1978-01-01

85

High-field magnetization of Dy2O3  

NASA Technical Reports Server (NTRS)

The magnetization of powdered samples of Dy2O3 has been measured at temperatures between 1.45 deg and 4.2 K, in applied magnetic fields ranging to 7 Teslas. A linear dependence of magnetization on applied field is observable in high field region, the slope of which is independent of temperature over the range investigated. The extrapolated saturation magnetic moment is 2.77 + or - 0.08 Bohr magnetons per ion.

Flood, D. J.

1974-01-01

86

30 Tesla hybrid magnet facility at the Francis Bitter National Magnet Laboratory, Massachusetts Institute of Technology  

SciTech Connect

The design, construction and testing of a hybrid magnet system which provides fields up to 30 T is described. The system consists of a superconducting magnet which generates 7.5 T in a 40 cm bore and a family of watercooled insert magnets operating at 10 mw. The superconducting magnet has an overall current density of nearly 6500 A/cm/sup 2/ and a surface heat flux of 0.5 W/cm/sup 2/. The helium management system whereby both helium and refrigeration are recovered from the magnet cryostat is also described. 4 refs.

Leupold, M.J.; Hale, J.R.; Iwasa, Y.; Rubin, L.G.; Weggel, R.J.

1981-09-01

87

Experiences using 3-tesla magnetic resonance imaging in the treatment of Moyamoya disease  

Microsoft Academic Search

\\u000a \\u000a Purpose  To introduce our initial experiences using 3-tesla (3T) magnetic resonance (MR) imaging in the treatment of moyamoya disease\\u000a (MMD).\\u000a \\u000a \\u000a \\u000a Methods  3T MR imaging was used to study 63 consecutive patients with MMD. Evaluation of regional cerebral blood flow (rCBF) was performed\\u000a with 123IMP-SPECT or 15O2 gas steady-state PET. T2*-weighted gradient-echo imaging was used to study the incidence of asymptomatic cerebral microbleeds

Ken-ichiro Kikuta

88

Aligning Paramecium caudatum with static magnetic fields.  

PubMed

As they negotiate their environs, unicellular organisms adjust their swimming in response to various physical fields such as temperature, chemical gradients, and electric fields. Because of the weak magnetic properties of most biological materials, however, they do not respond to the earth's magnetic field (5 x 10(-5) Tesla) except in rare cases. Here, we show that the trajectories of Paramecium caudatum align with intense static magnetic fields >3 Tesla. Otherwise straight trajectories curve in magnetic fields and eventually orient parallel or antiparallel to the applied field direction. Neutrally buoyant immobilized paramecia also align with their long axis in the direction of the field. We model this magneto-orientation as a strictly passive, nonphysiological response to a magnetic torque exerted on the diamagnetically anisotropic components of the paramecia. We have determined the average net anisotropy of the diamagnetic susceptibility, Deltachi(p), of a whole Paramecium: Deltachi(p) = (6.7+/- 0.7) x 10(-23) m(3). We show how the measured Deltachi(p) compares to the anisotropy of the diamagnetic susceptibilities of the components in the cell. We suggest that magnetic fields can be exploited as a novel, noninvasive, quantitative means to manipulate swimming populations of unicellular organisms. PMID:16461406

Guevorkian, Karine; Valles, James M

2006-04-15

89

Experimental studies of protozoan response to intense magnetic fields and forces  

Microsoft Academic Search

Intense static magnetic fields of up to 31 Tesla were used as a novel tool to manipulate the swimming mechanics of unicellular organisms. It is shown that homogenous magnetic fields alter the swimming trajectories of the single cell protozoan Paramecium caudatum, by aligning them parallel to the applied field. Immobile neutrally buoyant paramecia also oriented in magnetic fields with similar

Karine Guevorkian

2006-01-01

90

Processing of polymers in high magnetic fields  

SciTech Connect

Many organic molecules and polymers have an anisotropic diamagnetic susceptibility, and thus can be aligned in high magnetic fields. The presence of liquid crystallinity allows cooperative motions of the individual molecules, and thus the magnetic energy becomes greater than the thermal energy at experimentally obtainable field strengths. This work has determined the effect of magnetic field alignment on the thermal expansion and mechanical properties of liquid crystalline thermosets in the laboratory. Further advances in magnet design are needed to make magnetic field alignment a commercially viable approach to polymer processing. The liquid crystal thermoset chosen for this study is the diglycidyl ether of dihydroxy-{alpha}-methylstilbene cured with the diamine sulfamilamide. This thermoset has been cured at field strengths up to 18 Tesla.

Douglas, E.P.; Smith, M.E.; Benicewicz, B.C. [Los Alamos National Lab., NM (United States); Earls, J.D.; Priester, R.D. Jr. [Dow Chemical Co., Freeport, TX (United States)

1996-05-01

91

Recurrent ulnar nerve entrapment at the elbow: Correlation of surgical findings and 3-Tesla magnetic resonance neurography.  

PubMed

The authors describe the correlation between 3-Tesla magnetic resonance neurography (MRN) and surgical findings in two patients who underwent multiple previous failed ulnar nerve surgeries. MRN correctly localized the site of the abnormality. Prospectively observed MRN findings of perineural fibrosis, ulnar nerve re-entrapment abnormalities, medial antebrachial cutaneous neuroma and additional median nerve entrapment were confirmed surgically. PMID:24421652

Chhabra, Avneesh; Wadhwa, Vibhor; Thakkar, Rashmi S; Carrino, John A; Dellon, A Lee

2013-01-01

92

Quench problems of Nb3 Sn cosine theta high field dipole model magnets  

Microsoft Academic Search

We have developed and tested several cosine theta high field dipole model magnets for accelerator application, utilizing NbSn strands made by MJR method and PIT method. With Rutherford cables made with PIT strand we achieved 10.1 Tesla central field at 2.2 K operation, and 9.5 Tesla at 4.5 K operation. The magnet wound with the MJR cable prematurely quenched at

Ryuji Yamada; Masayoshi Wake

2004-01-01

93

Quench problems of Nb3Sn cosine theta high field dipole model magnets  

Microsoft Academic Search

We have developed and tested several cosine theta high field dipole model magnets for accelerator application, utilizing Nb3Sn strands made by MJR method and PIT method. With Rutherford cables made with PIT strand we achieved 10.1 Tesla central field at 2.2 K operation, and 9.5 Tesla at 4.5 K operation. The magnet wound with the MJR cable prematurely quenched at

Ryuji Yamada; Masayoshi Wake

2005-01-01

94

Crystal field and magnetic properties  

NASA Technical Reports Server (NTRS)

Magnetization and magnetic susceptibility measurements have been made in the temperature range 1.3 to 4.2 K on powdered samples of ErH3. The susceptibility exhibits Curie-Weiss behavior from 4.2 to 2 K, and intercepts the negative temperature axis at theta = 1.05 + or - 0.05 K, indicating that the material is antiferromagnetic. The low field effective moment is 6.77 + or - 0.27 Bohr magnetons per ion. The magnetization exhibits a temperature independent contribution, the slope of which is (5 + or - 1.2) x 10 to the -6th Weber m/kg Tesla. The saturation moment is 3.84 + or - 1 - 0.15 Bohr magnetons per ion. The results can be qualitatively explained by the effects of crystal fields on the magnetic ions. No definitive assignment of a crystal field ground state can be given, nor can a clear choice between cubically or hexagonally symmetric crystal fields be made. For hexagonal symmetry, the first excited state is estimated to be 86 to 100 K above the ground state. For cubic symmetry, the splitting is on the order of 160 to 180 K.

Flood, D. J.

1977-01-01

95

Coulomb Blockade Thermometry in the Milli-Kelvin Temperature Range in High Magnetic Fields  

Microsoft Academic Search

We have investigated the usability of a Coulomb blockade thermometer (CBT) at low temperatures around 50 mK and in high magnetic fields up to 27 Tesla. The experiments performed extend previous investigations both to lower temperatures and higher magnetic fields. We show that CBTs provide an easy way of magnetic field independent thermometry in an up to now problematic temperature

J. P. Pekola; J. K. Suoknuuti; J. P. Kauppinen; M. Weiss; P. v. d. Linden; A. G. M. Jansen

2002-01-01

96

Brain metabolism and cognitive impairment in HIV infection: a 3 Tesla Magnetic Resonance Spectroscopy Study  

PubMed Central

Background and Purpose HIV-associated dementia (HAD) has been extensively studied using magnetic resonance spectroscopy (MRS) at field strengths of 1.5 Tesla (T). Higher magnetic field strengths (such as 3T) allow for more reliable determination of certain compounds, such as glutamate (Glu) and glutamine (Gln). The current study was undertaken to investigate the utility of 3T MRS for evaluating HIV+ patients with different levels of cognitive impairment with emphasis on the measurement of Glu and Glx (the sum of Glu and Gln). Methods Eighty six HIV+ subjects were evaluated at 3T using quantitative short echo time single voxel MRS of frontal white matter (FWM) and basal ganglia (BG). Subjects were divided into 3 groups according to the Memorial Sloan Kettering (MSK) HIV dementia stage: 21 had normal cognition (NC) (MSK 0), 31 had mild cognitive impairment (MCI) without dementia, (clinical MSK stage = 0.5) and 34 had dementia (HAD) (MSK > 1). HIV+ subjects had also undergone standardized cognitive testing covering the domains of executive function, verbal memory, attention, information processing speed, and motor and psychomotor speed. Between group differences in metabolite levels in FWM and BG were evaluated using ANOVA. Pearson correlation coefficients were used to explore the associations between the Glu and Glx metabolites and neurocognitive (NP) results. Results FWM Glx (combined Glu and Gln) was lower in HAD (8.1±2.1 mM) compared to both the MCI (9.17±2.1 mM) and NC groups (10.0±1.6 mM), (P = 0.006). FWM myo-inositol (mI) was higher in HAD (4.15±0.75 mM) compared to both MCI (3.86±0.85 mM) and NC status (3.4±0.67 mM), (P = 0.006). FWM Glx/Creatine (Cr) was lower and FWM mI/Cr significantly higher in the HAD compared to MCI and NC groups (P = 0.01) and (P = 0.004) respectively. BG NAA was lower in the HAD group (6.79±1.53 mM), compared to the MCI (7.5±1.06 mM), and NC groups (7.6±1.01 mM), (P = 0.036). Significant negative correlations were observed between Glu, Glx, and NAA concentrations with Trail-making test B (P= 0.006, 0.0001, and 0.007 respectively) and significant positive correlation was found with Digit symbol test (P= 0.02, 0.002, and 0.008 respectively). FWM Glx and NAA concentrations showed negative correlation with Grooved pegboard non-dominant hand (P= 0.02 and 0.04 respectively). Conclusion Patients with HAD have lower levels of Glx concentrations and Glx/Cr ratio in FWM, which was associated with impaired performance in specific cognitive domains, including executive functioning, fine motor, attention and working memory performance. 3T MRS measurements of Glx may be a useful indicator of neuronal loss/dysfunction in patients with HIV infection.

Mohamed, M.A.; Barker, P.B.; Skolasky, R.L.; Selnes, O. A.; Moxley, R.T.; Pomper, M.G.; Sacktor, N.C.

2010-01-01

97

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

NASA Astrophysics Data System (ADS)

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

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

2002-03-01

98

Interaction mechanisms and biological effects of static magnetic fields  

SciTech Connect

Mechanisms through which static magnetic fields interact with living systems are described and illustrated by selected experimental observations. These mechanisms include electrodynamic interactions with moving, ionic charges (blood flow and nerve impulse conduction), magnetomechanical interactions (orientation and translation of molecules structures and magnetic particles), and interactions with electronic spin states in charge transfer reactions (photo-induced electron transfer in photosynthesis). A general summary is also presented of the biological effects of static magnetic fields. There is convincing experimental evidence for magnetoreception mechanisms in several classes of lower organisms, including bacteria and marine organisms. However, in more highly evolved species of animals, there is no evidence that the interactions of static magnetic fields with flux densities up to 2 Tesla (1 Tesla [T] = 10{sup 4} Gauss) produce either behavioral or physiolocical alterations. These results, based on controlled studies with laboratory animals, are consistent with the outcome of recent epidemiological surveys on human populations exposed occupationally to static magnetic fields.

Tenforde, T.S.

1994-06-01

99

Magnetic fields in astrophysics  

Microsoft Academic Search

The evidence of cosmic magnetism is examined, taking into account the Zeeman effect, beats in atomic transitions, the Hanle effect, Faraday rotation, gyro-lines, and the strength and scale of magnetic fields in astrophysics. The origin of magnetic fields is considered along with dynamos, the conditions for magnetic field generation, the topology of flows, magnetic fields in stationary flows, kinematic turbulent

Ia. B. Zeldovich; A. A. Ruzmaikin; D. D. Sokolov

1983-01-01

100

Magnetic field measurements of the superEBIS superconducting magnet. Informal report.  

National Technical Information Service (NTIS)

SuperEBIS was designed to have a solenoidal magnetic field of a 5 Tesla strength with a 120 cm long bore. The field was specified to be straight within 1 part in 10000 within the bore, and uniform to within 1 part in 1000 within the central 90 cm. Magneti...

A. Herschcovitch A. Kponou R. Clipperton W. Hensel F. Usack

1994-01-01

101

Characterization of transceive surface element designs for 7 tesla magnetic resonance imaging of the prostate: radiative antenna and microstrip  

NASA Astrophysics Data System (ADS)

Ultra-high field magnetic resonance (?7 tesla) imaging (MRI) faces challenges with respect to efficient spin excitation and signal reception from deeply situated organs. Traditional radio frequency surface coil designs relying on near-field coupling are suboptimal at high field strengths. Better signal penetration can be obtained by designing a radiative antenna in which the energy flux is directed to the target location. In this paper, two different radiative antenna designs are investigated to be used as transceive elements, which employ different dielectric permittivities for the antenna substrate. Their transmit and receive performances in terms of B+1, local SAR (specific absorption rate) and SNR (signal-to-noise ratio) were compared using extensive electromagnetic simulations and MRI measurements with traditional surface microstrip coils. Both simulations and measurements demonstrated that the radiative element shows twofold gain in B+1 and SNR at 10 cm depth, and additionally a comparable SAR peak value. In terms of transmit performance, the radiative antenna with a dielectric permittivity of 37 showed a 24% more favorable local SAR10g?avg/(B+1)2 ratio than the radiative antenna with a dielectric permittivity of 90. In receive, the radiative element with a dielectric permittivity of 90 resulted in a 20% higher SNR for shallow depths, but for larger depths this difference diminished compared to the radiative element with a dielectric permittivity of 37. Therefore, to image deep anatomical regions effectively, the radiative antenna with a dielectric permittivity of 37 is favorable.

Ipek, Ö.; Raaijmakers, A. J. E.; Klomp, D. W. J.; Lagendijk, J. J. W.; Luijten, P. R.; van den Berg, C. A. T.

2012-01-01

102

D-zero rototrack: first stage of D-zero 2 Tesla solenoid field mapping device  

SciTech Connect

A simple and portable field mapping device was developed at Fermilab and successfully used to test the D0 2 Tesla solenoid at Toshiba Works in Japan. A description of the mechanical structure, electric driving and control system, and software of the field mapping device is given. Four Hall probe elements of Group3 Digital Gaussmeters are mounted on the radial extension arm of a carriage, which is mounted on a central rotating beam. The system gives two dimensional motions (axial and rotational) to the Hall probes. To make the system compact and portable, we used a laptop computer with PCMCIA cards. For the control system we used commercially available software LabVIEW and Motion Toolbox, and for the data analysis we used Microsoft Excel.

Yamada, R.; Korienek, J.; Krider, J.; Lindenmeyer, C.; Miksa, D.; Miksa, R.

1997-09-01

103

The National High Magnetic Field Laboratory  

NASA Astrophysics Data System (ADS)

The National High Magnetic Field Laboratory (NHMFL) is a collaboration between Florida State University, the University of Florida, and the Los Alamos National Laboratory. The DC Field Facilities are located at the main campus for the NHMFL in Tallahassee, Florida and are described in this paper. The DC Field Facility has a variety of resistive and superconducting magnets. The DC Field Facility infrastructure, the most powerful in the world, is able to provide 57 MW of continuous low noise DC power. Constant magnetic fields of up to 45 tesla in a 32 mm bore and 20 tesla in 195 mm bore are available at no charge to the user community. The users of the facility are selected by a peer reviewed process. Roughly 400 research groups visit the lab to conduct experiments each year. Experimental capabilities provided by the NHMFL are magneto-optics, millimeter wave spectroscopy, magnetization, dilatometry, specific heat, electrical transport, ultrasound, low to medium resolution NMR, EMR, and materials processing. Measurements of properties can be made on samples at temperatures from 20 mK to 1000 K, pressures from ambient to 10 GPa, orientation and currents from 1 pA to 10 kA.

Hannahs, S. T.; Palm, E. C.

2010-04-01

104

Performance analysis of HD1: a 16 Tesla Nb3Sn dipole magnet  

Microsoft Academic Search

The Superconducting Magnet Group at Lawrence Berkeley National Laboratory (LBNL) has been developing technology for high field accelerator magnets from brittle conductors. HD1 is a single bore block dipole magnet using two, double-layer Nb3Sn flat racetrack coils. The magnet was tested in October 2003 and reached a bore peak field of 16 T (94.5% of short sample). The average quench

S. Mattafirri; S. E. Bartlett; P. A. Bish; S. Caspi; D. R. Dietderich; P. Ferracin; S. A. Gourlay; C. R. Hannaford; A. R. Hafalia; W. G. Lau; A. F. Lietzke; A. D. McInturff; M. Nyman; G. L. Sabbi; R. M. Scanlan

2005-01-01

105

Exploring Magnetic Field Lines  

NSDL National Science Digital Library

In this activity, learners explore the magnetic field of a bar magnet as an introduction to understanding Earth's magnetic field. First, learners explore and play with magnets and compasses. Then, learners trace the field lines of the magnet using the compass on a large piece of paper. This activity will also demonstrate why prominences are always "loops."

Nasa

2012-06-26

106

Earth's Inconstant Magnetic Field  

NSDL National Science Digital Library

This NASA site describes long-term changes in Earth's magnetic field, and how magnetic stripes in the Atlantic seafloor provide evidence for reversals of this field. The site presents a model of Earth's interior that helps explain how Earth's magnetic field is generated and how the reversals occur. A computer-generated image shows the complicated magnetic field in-between reversals.

2007-04-27

107

Exploring Magnetic Fields  

NSDL National Science Digital Library

This is an activity about magnetic fields. Using iron filings, learners will observe magnets in various arrangements to investigate the magnetic field lines of force. This information is then related to magnetic loops on the Sun's surface and the magnetic field of the Earth. This is the second activity in the Exploring the Earth's Magnetic Field: An IMAGE Satellite Guide to the Magnetosphere educators guide.

108

Cylindrical isentropic compression by ultrahigh magnetic field  

NASA Astrophysics Data System (ADS)

The cylindrical isentropic compression by ultrahigh magnetic field (MC-1) is a kind of unique high energy density technique. It has characters like ultrahigh pressure and low temperature rising, and would have widely used in areas like high pressure physics, new material synthesis and ultrahigh magnetic field physics. The Institute of Fluid Physics, Chinese Academy of Engineering Physics (IFP, CAEP) has begun the experiment since 2011 and a primary experimental device had been set-up. In the experiments, a seed magnetic field of 5 Tesla were set-up first and compressed by a stainless steel liner which is driven by high explosive initiated synchronously. The internal diameter of the liner is 97 mm, and its thickness is 1.5 mm. The movement of liner was recorded optically and a typical turnaround phenomenon was observed. From the photography results the liner was compressed smoothly and evenly and its average velocity was about 5-6 km/s. In the experiment a axial magnetic field of over 1400 Tesla has been recorded. The MC-1 process was numerical simulated by 1D MHD code MC11D and the simulations are in accord with the experiments.

Gu, Zhuowei; Luo, Hao; Zhang, Hengdi; Zhao, Shichao; Tang, Xiaosong; Tong, Yanjin; Song, Zhenfei; Tan, Fuli; Zhao, Jianheng; Sun, Chengwei

2014-05-01

109

Exploring Magnetic Fields  

NSDL National Science Digital Library

In this activity, students investigate the presence of magnetic fields around magnets, the sun and the earth. They will explore magnetic field lines, understand that magnetic lines of force show the strength and direction of magnetic fields, determine how field lines interact between attracting and repelling magnetic poles, and discover that the earth and sun have magnetic properties. They will also discover that magnetic force is invisible and that a "field of force" is a region or space in which one object can attract or repel another.

110

Magnetic Fields Matter  

NSDL National Science Digital Library

This lesson introduces students to the effects of magnetic fields in matter addressing permanent magnets, diamagnetism, paramagnetism, ferromagnetism, and magnetization. First students must compare the magnetic field of a solenoid to the magnetic field of a permanent magnet. Students then learn the response of diamagnetic, paramagnetic, and ferromagnetic material to a magnetic field. Now aware of the mechanism causing a solid to respond to a field, students learn how to measure the response by looking at the net magnetic moment per unit volume of the material.

VU Bioengineering RET Program, School of Engineering,

111

Design status of the US 100 tesla non-destructive magnet system  

SciTech Connect

A collaborative effort is now underway in the US between the Department of Energy and the National Science Foundation to design, build, and use a 100 T non-destructive magnet for studying the properties of materials at high fields. The National High Magnetic Field Laboratory (NHMFL) at Tallahassee, Florida, and Los Alamos, New Mexico, where the magnet will be sited, is carrying out this task. This magnet will join other pulsed magnets at NHMFL, to provide magnetic fields at strengths, time durations, and volumes that are longer (in combination) than any now available. In particular, the goal for the 100 T magnet is a time duration above 80 T of about 15 ms in a cold bore of 24 mm. The present status of the design effort and various design issues are presented here.

Schneider-Muntau, H.; Eyssa, Y.; Pernambuco-Wise, P. [Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab.; Boenig, H.; Campbell, L.J.; Eberl, K.R.; Parkin, D.M.; Schillig, J.; Sims, J. [Los Alamos National Lab., NM (United States)

1996-09-01

112

MIT 12 Tesla Coil test results  

Microsoft Academic Search

Test results from the MIT 12 Tesla Coil experiment are presented. The coil was tested in the High Field Test Facility (HFTF) of the Lawrence Livermore National Laboratory in October 1984 and January 1985. The experiment measured the performance of an Internally Cooled, Cabled Superconductor (ICCS) of practical size, intended for use in magnetic fusion experiments. The MIT coil carried

M. M. Steeves; M. O. Hoenig

1985-01-01

113

Visualizing Magnetic Field Lines  

NSDL National Science Digital Library

In this activity, students take the age old concept of etch-a-sketch a step further. Using iron filings, students begin visualizing magnetic field lines. To do so, students use a compass to read the direction of the magnet's magnetic field. Then, students observe the behavior of iron filings near that magnet as they rotate the filings about the magnet. Finally, students study the behavior of iron filings suspended in mineral oil which displays the magnetic field in three dimensions.

VU Bioengineering RET Program, School of Engineering,

114

3 tesla magnetic resonance imaging of the occipitoatlantoaxial region in the normal horse.  

PubMed

The aim of this study was to describe the appearance of the ligamentous structures of the occipitoatlantoaxial (OAA) region in the normal horse by 3 tesla (3T) magnetic resonance imaging (MRI). The MRI images of the longitudinal odontoid ligament, tectorial membrane, dorsal and ventral atlantoaxial ligaments, dorsal atlantooccipital membrane with its reinforcing ligaments, and the lateral atlantooccipital ligaments of 10 horse cadavers were evaluated. All ligaments and membranes were identified in all planes, except for the lateral atlantooccipital ligament in the sagittal plane due to its cranioventrolateral course. All were iso to mildly hypointense to musculature of the neck in T1W with the exception of the tectorial membrane that was moderately hypointense; moderately hypointense in PD-SPIR, and markedly hypointense (isointense to cortical bone) in T2W. The PD-SPIR was the best sequence to identify all ligaments and membranes from their cranial and caudal attachments. The longitudinal odontoid ligament, ventral atlantoaxial ligament, and reinforcing bands of the dorsal atlantooccipital membrane presented a characteristic striped heterogeneous signal behavior thought to be due to fibrocartilaginous content. The remaining ligaments and membranes showed homogeneous signal intensity. Special anatomical features in this species such as the fan-shaped longitudinal odontoid ligament, absence of the transverse ligament and presence of the ventral atlantoaxial ligament were documented. Ligamentous structures that stabilize the equine OAA region were described with MRI in this study and these findings could serve as an anatomic reference for those cases where instability of this region is suspected. PMID:24219352

Gutiérrez-Crespo, Beatriz; Kircher, Patrick R; Carrera, Ines

2014-05-01

115

Effects of Magnetic Field on Biological Cells and Applications  

NASA Astrophysics Data System (ADS)

While there has been extensive research performed in the physics of magnetic fields and the physics and chemistry in life sciences, independent of each other, there has been a paucity of scientific research and development investigating the possible applications of magnetic fields in life sciences. The focus of this presentation is to present the stimulation mechanism by which magnetic fields affect (a) yeast cells (b) plant cells and (c) mammalian normal and cancer cells. Recently we have found that the Saccharomyces Cerevsa yeast growth increases by about 30to a 1 tesla field and the production of CO2 increases by about 30of yeast metabolism may be due to an increase in intercellular interaction and protein channel alignment, the introduction of an alteration in the DNA from the magnetic field exposure or a combination of these mechanisms. We also have found that the application of high magnetic fields (1 tesla and above) can have marked effects on the germination and growth of plants, especially corn, beans and peas. This finding has opened up the possibility of technology developments in botanical growth systems to accelerate seed germination and crop harvesting. Most recently we have investigated the application of high magnetic fields on leukemia, CaCoII and HEP G2 cancer cell lines. We found that when leukemia are exposed to a 12 tesla field for 2 hours has an increase in cell death by about 30that were not exposed to the magnetic field. Viability of CaCoII cells sandwiched between permanent magnets of maximum strength of 1.2 tesla was measured. A decrease in viable cells by 33unexposed cells. HSP 70 was measured for HEPG2 cells that were exposed to permanent magnetic field of 1.2 tesla for 40 minutes and for unexposed cells. It was found that the exposed cells produce 19 times more HSP70 compared to unexposed cells. Our results together with other investigators report suggest a strong evidence of a reduction in the cell growth rate for cancer cells when subjected to high magnetic field. Devices that utilize an applied steady magnetic filed in it operation such as devices for blood component separation and diagnostic sensors have been developed.

Chen, Ching-Jen

2001-03-01

116

Fabrication and test results of a high field, Nb3Sn superconducting racetrack dipole magnet  

Microsoft Academic Search

The LBNL Superconducting Magnet Program is extending accelerator magnet technology to the highest possible fields. A 1 meter long, racetrack dipole magnet, utilizing state-of-the-art Nb3Sn superconductor, has been built and tested. A record dipole filed of 14.7 Tesla has been achieved. Relevant features of the final assembly and test results are discussed

R. Benjegerdes; P. Bish; D. Byford; S. Caspi; D. R. Dietderich; S. A. Gourlay; R. Hafalia; R. Hannaford; H. Higley; A. Jackson; A. Lietzke; N. Liggins; A. D. McInturff; J. O'Neill; E. Palmerston; G. Sabbi; R. M. Scanlan; J. Swanson

2001-01-01

117

Radiation exposure and magnetic performance of the undulator system for the VUV FEL at the TESLA Test Facility Phase1 after 3 years of operation  

Microsoft Academic Search

Radiation damage to undulator systems made of permanent magnet materials like NdFeB or SmCo is a critical issue in SASE projects. It is of even more interest in high-duty cycle machines using superconducting accelerators such as the TESLA Test Facility (TTF), which is a prototype for the future X-FEL at TESLA. This paper reports on experience on the undulator system

J Pflüger; B Faatz; M Tischer; T Vielitz

2003-01-01

118

Mapping Magnetic Fields  

NSDL National Science Digital Library

This is an activity about bar magnets and their invisible magnetic fields. Learners will experiment with magnets and a compass to detect and draw magnetic fields. This is Activity 1 of a larger resource, entitled Exploring the Sun. The NASA spacecraft missions represented by this material include SOHO, TRACE, STEREO, Hinode, and SDO.

119

Magnetic field mapper  

NASA Technical Reports Server (NTRS)

Magnetic field mapper locates imperfections in cadmium sulphide solar cells by detecting and displaying the variations of the normal component of the magnetic field resulting from current density variations. It can also inspect for nonuniformities in other electrically conductive materials.

Masters, R. M.; Stenger, F. J.

1969-01-01

120

A functional magnetic resonance imaging study of listening comprehension of languages in human at 3 tesla-comprehension level and activation of the language areas.  

PubMed

Passive listening comprehension of native and non-native language was investigated using high resolution functional magnetic resonance imaging (fMRI) at a static magnetic field strength of 3 tesla. Wernicke's area was activated by comprehensive and non-comprehensive languages indicating that this area is associated with common phonological processing of language. The task with comprehensive but non-native language activated Broca's area and angular gyrus most frequently. The activations in these areas may be related to demand in semantic and syntactic processing in listening comprehension. Supplementary motor area and pre-motor area were activated by comprehensive languages but not by non-comprehensive language. These motor controlling areas may be involved in semantic processing. Listening to comprehensive but non-native language seems to demand more networked co-processing. PMID:10218904

Nakai, T; Matsuo, K; Kato, C; Matsuzawa, M; Okada, T; Glover, G H; Moriya, T; Inui, T

1999-03-19

121

Construction of a sub-Kelvin ultrahigh vacuum scanning tunneling microscope in high magnetic field  

Microsoft Academic Search

A sub-Kelvin ultrahigh vacuum (UHV) scanning tunneling microscope (STM) high magnetic field has been designed and constructed, and has been tested at ˜ 1K and in high magnetic field up to 9 teslas. A four-chamber ultrahigh vacuum system creates reliable environment for tip and sample preparation, surface characterization, and exchanging samples, tips, and evaporating materials. The pressure of chambers is

Ungdon Ham

2007-01-01

122

The Declining Magnetic Field  

NSDL National Science Digital Library

This is an activity about the declining strength of Earth's magnetic field. Learners will review a graph of magnetic field intensity and calculate the amount by which the field has changed its intensity in the last century, the rate of change of its intensity, and when the field should decrease to zero strength at the current rate of change. Learners will also use evidence from relevant sources to create a conjecture on the effects on Earth of a vanished magnetic field. Access to information sources about Earth's magnetic field strength is needed for this activity. This is Activity 7 in the Exploring Magnetism on Earth teachers guide.

123

Experimental studies on thermal behavior of 6 Tesla cryogen-free superconducting magnet system  

NASA Astrophysics Data System (ADS)

A 6 T cryogen-free superconducting magnet system (CFMS) with warm bore has been designed, built and tested for carrying out physical property measurements at high magnetic field. The CFMS has a vertical ? 50 mm clear room temperature working bore. A two-stage GM-cryocooler of 35 W at 50 K and 1.5 W at 4 K cooling capacity has been used to cool the thermal radiation shield, hybrid current leads and the NbTi magnet. The magnet was charged to 102 A, which produced a field of 6 T, in less than 20 minutes. The outer surface temperature of magnet rose from 3.3 K at zero current to 3.9 K at 102 A current. The thermal link between cold head and magnet greatly influences the excitation rate and the stability of the magnet. Based upon our thermal analysis on the magnet system, an experimental study has been carried out on the thermal behavior of the magnet during its operation. A novel technique has been used for connecting the high temperature superconducting current leads to the magnet so as to reduce both electrical and thermal contact resistance at the 2nd stage of the cryocooler. This paper briefly describes the design, development and results of experimental studies of thermal behavior of the system.

Kar, Soumen; Konduru, Phaneendra; Kumar, Rajesh; Kumar, Manoj; Choudhury, Anup; Sharma, Ram Gopal; Datta, Tripti Sekhar

2012-06-01

124

Solar Magnetic Field  

NASA Astrophysics Data System (ADS)

Electrical currents flowing in the solar plasma generate a magnetic field, which is detected in the SOLAR ATMOSPHERE by spectroscopic and polarization measurements (SOLAR MAGNETIC FIELD: INFERENCE BY POLARIMETRY). The SOLAR WIND carries the magnetic field into interplanetary space where it can be measured directly by instruments on space probes....

Schüssler, M.; Murdin, P.

2000-11-01

125

Noninvasive magnetic resonance thermography of recurrent rectal carcinoma in a 1.5 Tesla hybrid system.  

PubMed

To implement noninvasive thermometry, we installed a hybrid system consisting of a radiofrequency multiantenna applicator (SIGMA-Eye) for deep hyperthermia (BSD-2000/3D) integrated into the gantry of a 1.5 Tesla magnetic resonance (MR) tomograph Symphony. This system can record MR data during radiofrequency heating and is suitable for application and evaluation of methods for MR thermography. In 15 patients with preirradiated pelvic rectal recurrences, we acquired phase data sets (25 slices) every 10 to 15 minutes over the treatment time (60-90 minutes) using gradient echo sequences (echo time = 20 ms), transformed the phase differences to MR temperatures, and fused the color-coded MR-temperature distributions with anatomic T1-weighted MR data sets. We could generate one complete series of MR data sets per patient with satisfactory quality for further analysis. In fat, muscle, water bolus, prostate, bladder, and tumor, we delineated regions of interest (ROI), used the fat ROI for drift correction by transforming these regions to a phase shift zero, and evaluated the MR-temperature frequency distributions. Mean MR temperatures (T(MR)), maximum T(MR), full width half maximum (FWHM), and other descriptors of tumors and normal tissues were noninvasively derived and their dependencies outlined. In 8 of 15 patients, direct temperature measurements in reference points were available. We correlated the tumor MR temperatures with direct measurements, clinical response, and tumor features (volume and location), and found reasonable trends and correlations. Therefore, the mean T(MR) of the tumor might be useful as a variable to evaluate the quality and effectivity of heat treatments, and consequently as optimization variable. Feasibility of noninvasive MR thermography for regional hyperthermia has been shown and should be further investigated. PMID:15994965

Gellermann, Johanna; Wlodarczyk, Waldemar; Hildebrandt, Bert; Ganter, Hildegard; Nicolau, Anett; Rau, Beate; Tilly, Wolfgang; Fähling, Horst; Nadobny, Jacek; Felix, Roland; Wust, Peter

2005-07-01

126

The U.S. NHMFL 100 tesla multi-shot magnet  

SciTech Connect

The design, analysis and fabrication progress of the 100 T Multi-Shot Magnet is described. The description includes the structural analysis of the outer coil set, the fabrication of the 100 T prototype coil 1, the fabrication of a coil 1 test shell, and the analysis of the electrical busbar assembly. Fabrication issues and their solutions are presented. This magnet will be installed as part of the user facility research equipment at the U.S. National High Magnetic Field Laboratory (NHMFL) Pulsed Field Facility at Los Alamos National Laboratory.

Ammerman, C. N. (Curtt N.); Coe, H. (Hideyoshi); Ellis, G. G. (Gretchen G.); Lesch, B. L. (Bernard L.); Sims, J. R. (James R.); Schillig, J. B. (Josef B.); Swenson, C. A. (Charles A.); Bacon, J. L. (James L.)

2001-01-01

127

Effect of homogeneous and inhomogeneous high magnetic fields on the growth of Escherichia coli  

Microsoft Academic Search

The growth of Escherichia coli B was investigated under homogenous 7 Tesla (T) magnetic field, and inhomogeneous 5.2?6.1 T and 3.2?6.7 T magnetic fields which are produced by a newly constructed superconducting magnet biosystem (SBS). These high magnetic field adversely affected on the growth of the bacterium in the early logarithmic growth phase. However, in the stationary phase, the cell

Koji Tsuchiya; Kazuhiro Nakamura; Kazumasa Okuno; Takashi Ano; Makoto Shoda

1996-01-01

128

Early Knee Changes in Dancers Identified by Ultra High Field 7 Tesla MRI  

PubMed Central

Introduction We aimed to determine whether a unique, ultra high-field 7 Tesla (T) MRI scanner could detect occult cartilage and meniscal injuries in asymptomatic female dancers. Materials and Methods This study had institutional review board approval. We recruited eight pre-professional female dancers and nine non-athletic, female controls. We scanned the dominant knee on a 7T MRI scanner using a 3D-FLASH sequence and a proton density, fast spin-echo sequence to evaluate cartilage and menisci, respectively. Two radiologists scored cartilage (International Cartilage Repair Society classification) and meniscal (Stoller classification) lesions. We applied two-tailed z- and t-tests to determine statistical significance. Results There were no cartilage lesions in dancers or controls. For the medial meniscus, the dancers compared to controls demonstrated higher mean MRI score (2.38±0.61 vs. 1.0±0.97, p<0.0001) and higher frequency of mean grade 2 lesions (88% vs. 11%, p<0.01). For the lateral meniscus, there was no difference in score (0.5±0.81 vs. 0.5±0.78, p=0.78) in dancers compared to controls. Discussion Asymptomatic dancers demonstrate occult medial meniscal lesions. Because this has been described in early osteoarthritis, close surveillance of dancers’ knee symptoms and function with appropriate activity modification may help maintain their long-term knee health.

Chang, Gregory; Diamond, Matthew; Nevsky, Gregory; Regatte, Ravinder R.; Weiss, David S.

2012-01-01

129

Drawing Magnetic Fields  

NSDL National Science Digital Library

Students use a compass and a permanent magnet to trace the magnetic field lines produced by the magnet. By positioning the compass in enough spots around the magnet, the overall magnet field will be evident from the collection of arrows representing the direction of the compass needle. In activities 3 and 4 of this unit, students will use this information to design a way to solve the grand challenge of separating metal for a recycling company.

Vu Bioengineering Ret Program

130

The Magnetic Field  

NSDL National Science Digital Library

This demonstration of the magnetic field lines of Earth uses a bar magnet, iron filings, and a compass. The site explains how to measure the magnetic field of the Earth by measuring the direction a compass points from various points on the surface. There is also an explanation of why the north magnetic pole on Earth is actually, by definition, the south pole of a magnet.

Barker, Jeffrey

131

Circuits and Magnetic Fields  

NSDL National Science Digital Library

In this activity, students use the same method as in the activity from lesson 2 to explore the magnetism due to electric current instead of a permanent magnet. Students use a compass and circuit to trace the magnetic field lines induced by the electric current moving through the wire. Students develop an understanding of the effect of the electrical current on the compass needle through the induced magnetic field and understand the complexity of a three dimensional field system.

Vu Bioengineering Ret Program

132

Photospheric magnetic fields  

NASA Technical Reports Server (NTRS)

Knowledge on the nature of magnetic fields on the solar surface is reviewed. At least a large part of the magnetic flux in the solar surface is confined to small bundles of lines of force within which the field strength is of the order of 500 gauss. Magnetic fields are closely associated with all types of solar activity. Magnetic flux appears at the surface at the clearly defined birth or regeneration of activity of an active region. As the region ages, the magnetic flux migrates to form large-scale patterns and the polar fields. Some manifestations of the large-scale distribution are discussed.

Howard, R.

1972-01-01

133

New measurements of magnetic field decay in 1 meter SSC-type dipoles  

SciTech Connect

Previous studies of magnetic field decay in model SSC dipoles due to changes in magnetization currents caused by flux creep have used the assumed SSC injection energy of 1 TeV, or 0.33 tesla central dipole field, and an excitation to the storage field of 6.6 tesla. More recently, it has been decided to inject at 2 TeV, or 0.66 tesla and so more recent tests have been carried out at the new injection field, or at both the new and old fields. Additionally, the effect of temperature changes and excitation cycles on the field decay have been studied. 6 refs., 11 figs., 2 tabs.

Gilbert, W.S.; Althaus, R.F.; Barale, P.J.; Benjegerdes, R.W.; Green, M.A.; Green, M.I.; Scanlan, R.M.

1990-09-01

134

Mapping Magnetic Field Lines  

NSDL National Science Digital Library

This is a lesson about the magnetic field of a bar magnet. The lesson begins with an introductory discussion with learners about magnetism to draw out any misconceptions that may be in their minds. Then, learners freely experiment with bar magnets and various materials, such as paper clips, rulers, copper or aluminum wire, and pencils, to discover that magnets attract metals containing iron, nickel, and/or cobalt but not most other materials. Next, learners experiment with using a magnetic compass to discover how it is affected by the magnet and then draw the magnetic field lines of the magnet by putting dots at the location of the compass arrow. This is the first lesson in the first session of the Exploring Magnetism teacher guide.

135

HD1: Design and Fabrication of a 16 Tesla Nb3Sn DipoleMagnet  

SciTech Connect

The Lawrence Berkeley National Laboratory (LBNL) Superconducting Magnet Group has completed the design, fabrication and test of HD1, a 16 T block-coil dipole magnet. State of the art Nb{sub 3}Sn conductor was wound in double-layer racetrack coils and supported by an iron yoke and a tensioned aluminum shell. In order to prevent conductor movement under magnetic forces up to the design field, a coil pre-stress of 150 MPa was required. To achieve this level without damaging the brittle conductor, the target stress was generated during cool-down to 4.2 K by exploiting the thermal contraction differentials between yoke and shell. Accurate control of the shell tension during assembly was obtained using pressurized bladders and interference load keys. An integrated 3D CAD model was used to optimize magnetic and mechanical design and analysis.

Hafalia, A.R.; Bartlett, S.E.; Capsi, S.; Chiesa, L.; Dietderich,D.R.; Ferracin, P.; Goli, M.; Gourlay, S.A.; Hannaford, C.R.; Highley,H.; Lietzke, A.F.; Liggins, N.; Mattafirri, S.; McInturff, A.D.; Nyman,M.; Sabbi, G.L.; Scanlan, R.M.; Swanson, J.

2003-11-10

136

Melatonin and magnetic fields.  

PubMed

There is public health concern raised by epidemiological studies indicating that extremely low frequency electric and magnetic fields generated by electric power distribution systems in the environment may be hazardous. Possible carcinogenic effects of magnetic field in combination with suggested oncostatic action of melatonin lead to the hypothesis that the primary effects of electric and magnetic fields exposure is a reduction of melatonin synthesis which, in turn, may promote cancer growth. In this review the data on the influence of magnetic fields on melatonin synthesis, both in the animals and humans, are briefly presented and discussed. PMID:12019358

Karasek, Michal; Lerchl, Alexander

2002-04-01

137

Experimental studies of axial magnetic fields generated in ultrashort-pulse laser-plasma interaction  

Microsoft Academic Search

The quasistatic axial magnetic fields in plasmas produced by ultrashort laser pulses were measured by measuring the Faraday\\u000a rotation angle of the backscattered emission. The spatial distribution of the axial magnetic field was obtained with a peak\\u000a value as high as 170 Tesla. Theory suggests that the axial magnetic field is generated by dynamo effect in laser-plasma interaction.

Yutong Li; Jie Zhang; Liming Chen; Lizeng Zhao; Jiangfan Xia; Zhiyi Wei; Wenmian Jiang

2000-01-01

138

Hyperemic stress myocardial perfusion cardiovascular magnetic resonance in mice at 3 Tesla: initial experience and validation against microspheres  

PubMed Central

Background Dynamic first pass contrast-enhanced myocardial perfusion is the standard CMR method for the estimation of myocardial blood flow (MBF) and MBF reserve in man, but it is challenging in rodents because of the high temporal and spatial resolution requirements. Hyperemic first pass myocardial perfusion CMR during vasodilator stress in mice has not been reported. Methods Five C57BL/6 J mice were scanned on a clinical 3.0 Tesla Achieva system (Philips Healthcare, Netherlands). Vasodilator stress was induced via a tail vein catheter with an injection of dipyridamole. Dynamic contrast-enhanced perfusion imaging (Gadobutrol 0.1 mmol/kg) was based on a saturation recovery spoiled gradient echo method with 10-fold k-space and time domain undersampling (k-t PCA). One week later the mice underwent repeat anaesthesia and LV injections of fluorescent microspheres at rest and at stress. Microspheres were analysed using confocal microscopy and fluorescence-activated cell sorting. Results Mean MBF at rest measured by Fermi-function constrained deconvolution was 4.1?±?0.5 ml/g/min and increased to 9.6?±?2.5 ml/g/min during dipyridamole stress (P?=?0.005). The myocardial perfusion reserve was 2.4 ±?0.54. The mean count ratio of stress to rest microspheres was 2.4 ±?0.51 using confocal microscopy and 2.6?±?0.46 using fluorescence. There was good agreement between cardiovascular magnetic resonance CMR and microspheres with no significant difference (P?=?0.84). Conclusion First-pass myocardial stress perfusion CMR in a mouse model is feasible at 3 Tesla. Rest and stress MBF values were consistent with existing literature and perfusion reserve correlated closely to microsphere analysis. Data were acquired on a 3 Tesla scanner using an approach similar to clinical acquisition protocols, potentially facilitating translation of imaging findings between rodent and human studies.

2013-01-01

139

Time-Varying Magnetic Fields: Effect on DNA Synthesis  

Microsoft Academic Search

Human fibroblasts have exhibited enhanced DNA synthesis when exposed to sinusoidally varying magnetic fields for a wide range of frequencies (15 hertz to 4 kilohertz) and amplitudes (2.3 × 10-6 to 5.6 × 10-4 tesla). This effect, which is at maximum during the middle of the S phase of the cell cycle, appears to be independent of the time derivative

A. R. Liboff; T. Williams; D. M. Strong; R. Wistar

1984-01-01

140

[Optimized magnetic resonance sequences and parameters with operative assisted images for radical prostatectomy at 3 tesla-magnetic resonance image].  

PubMed

The objective of our study was to optimize magnetic resonance image (MRI) sequences and parameters using operative assisted images (three-dimensional images) for radical prostatectomy at 3 tesla (T) MRI. Five healthy volunteers underwent MRI on the 3.0 T scanner. Various sequences and parameters [Cube (TE/TR = 18, 50, 90 ms/2000 ms), FIESTA (TE/TR/FA = 2.4 ms/5 ms/40 degrees, 90 degrees), fSPGR (TE/TR/FA = 2.3 ms/11.2 ms/20 degrees), slice thickness = 1.2 mm, matrix = 192 x 160] were respectively compared. Several structures of the pelvis (the central zones and transition zones of the prostate, the peripheral zones of the prostate, seminal vesicles, rectum wall, bladder, muscle and fat) were determined. The signal intensities of these structures were measured on reformatted axial images and compared against several structures of the pelvis. Correlation with various sequences and parameters was based on the signal-to-noise ratio (SNR), the contrast ratio (CR) and the presence of artifacts. Student's t-test was used for statistical analysis. With Cube (TE/TR = 50 ms/2000 ms), the average value of visual evaluation with artifacts was high, and SNR and CR were higher than for other sequence and parameters. Optimized MRI sequences and parameters were Cube (TE/TR = 50 ms/2000 ms) which provides improved SNR and CR and the presence of artifacts with operative assisted images for radical prostatectomy. These operative assisted images obtained from Cube (TE/TR = 50 ms/2000 ms) are likely to be useful for surgery. PMID:23964533

Shirase, Ryuji; Sakurai, Yuuki; Nagahama, Hiroshi; Harada, Kuniaki; Takashima, Hiroyuki; Nakanishi, Mitsuhiro; Harada, Kohei; Shishido, Hiroki; Imamura, Rui; Sakata, Motomichi; Hatakenaka, Masamitsu

2013-05-01

141

Magnetic Field Viewing Cards  

NASA Astrophysics Data System (ADS)

For some years now laminated cards containing a green, magnetically sensitive film have been available from science education suppliers. When held near a magnet, these cards appear dark green in regions where the field is perpendicular to the card and light green where the field is parallel to the card. The cards can be used to explore the magnetic field near a variety of magnets as well as near wire loops. In this paper we describe how to make these cards and how we have used them in our physics classrooms and labs.

Kanim, Stephen; Thompson, John R.

2005-09-01

142

The galactic magnetic field  

Microsoft Academic Search

Estimates for the scale, geometry and strength of the magnetic field in the galactic system can be derived from observations of polarization properties of radio emission from the Galaxy, extragalactic radio sources and pulsars, and polarization of starlight. Within distances of about 500 parsecs (1 parsec = 3.26 lightyears) from the solar system the magnetic field is directed towards galactic

T A Spoelstra; T. A. T

1977-01-01

143

Interplanetary Magnetic Field Lines  

NSDL National Science Digital Library

This web page provides information and a graphical exercise for students regarding the interaction between magnetic field lines and a plasma. The activity involves tracing a typical interplanetary magnetic field line, dragged out of a location on the Sun by the radial flow of the solar wind. This illustrates the way magnetic field lines are "frozen to the plasma" and the wrapping of field lines due to the rotation of the sun. This is part of the work "The Exploration of the Earth's Magnetosphere". A Spanish translation is available.

Stern, David

2005-04-27

144

Static Magnetic Fields in Semiconductor Floating-Zone Growth  

NASA Technical Reports Server (NTRS)

Heat and mass transfer in semiconductor float-zone processing are strongly influenced by convective flows in the zone, originating from sources such as buoyancy convection, thermocapillary (Marangoni) convection, differential rotation, or radio frequency heating. Because semiconductor melts are conducting, flows can be damped by the use of static magnetic fields to influence the interface shape and the segregation of dopants and impurities. An important objective is often the suppression of time-dependent flows and the ensuing dopant striations. In RF-heated Si-FZ - crystals, fields up to O.STesla show some flattening of the interface curvature and a reduction of striation amplitudes. In radiation-heated (small-scale) SI-FZ crystals, fields of 0.2 - 0.5 Tesla already suppress the majority of the dopant striations. The uniformity of the radial segregation is often compromised by using a magnetic field, due to the directional nature of the damping. Transverse fields lead to an asymmetric interface shape and thus require crystal rotation (resulting in rotational dopant striations) to achieve a radially symmetric interface, whereas axial fields introduce a coring effect. A complete suppression of dopant striations and a reduction of the coring to insignificant values, combined with a shift of the axial segregation profile towards a more diffusion-limited case, are possible with axial static fields in excess of 1 Tesla. Strong static magnetic fields, however, can also lead to the appearance of thermoelectromagnetic convection, caused by the interaction of thermoelectric currents with the magnetic field.

Croll, Arne; Benz, K. W.

1999-01-01

145

Magnetic fields at Neptune  

SciTech Connect

The National Aeronautics and Space Administration Goddard Space Flight Center-University of Delaware Bartol Research Institute magnetic field experiment on the Voyager 2 spacecraft discovered a strong and complex intrinsic magnetic field of Neptune and an associated magnetosphere and magnetic tail. A maximum magnetic field of nearly 10,000 nanoteslas (1 nanotesla = 10{sup {minus}5} gauss) was observed near closest approach, at a distance of 1.18 R{sub N}. The planetary magnetic field between 4 and 15 R{sub N} can be well represented by an offset tilted magnetic dipole (OTD), displaced from the center of Neptune by the surprisingly large amount of 0.55 R{sub N} and inclined by 47{degrees} with respect to the rotation axis. Within 4 R{sub N}, the magnetic field representation must include localized sources or higher order magnetic multipoles, or both, which are not yet well determined. As the spacecraft exited the magnetosphere, the magnetic tail appeared to be monopolar, and no crossings of an imbedded magnetic field reversal or plasma neutral sheet were observed. The auroral zones are most likely located far from the rotation poles and may have a complicated geometry. The rings and all the known moons of Neptune are imbedded deep inside the magnetosphere, except for Nereid, which is outside when sunward of the planet. The radiation belts will have a complex structure owing to the absorption of energetic particles by the moons and rings of Neptune and losses associated with the significant changes in the diurnally varying magnetosphere configuration. In an astrophysical context, the magnetic field of Neptune, like that of Uranus, may be described as that of an oblique rotator.

Ness, N.F. (Univ. of Delaware, Newark (USA)); Acuna, M.H.; Burlaga, L.F.; Connerney, J.E.P.; Lepping, R.P. (NASA, Greenbelt, MD (USA)); Neubauer, F.M. (Universitaet zu Koln (West Germany))

1989-12-15

146

Sonoluminescence in High Magnetic Fields  

Microsoft Academic Search

We have made a detailed study of sonoluminescence (SL) in high magnetic fields. In magnetic field sweeps at constant levels of acoustic drive, SL disappears above a pressure-dependent threshold magnetic field. Sweeps of acoustic drive at fixed magnetic fields show that the upper and lower bounds of forcing pressure that determine the region of SL increase dramatically with magnetic field.

J. B. Young; T. Schmiedel; Woowon Kang

1996-01-01

147

Magnetic Bar Field Model  

NSDL National Science Digital Library

The EJS Magnetic Bar Field Model shows the field of a bar magnet and has a movable compass that reports the magnetic field values. The bar magnet model is built by placing a group of magnetic dipoles along the bar magnet. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. The Magnetic Bar Field 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_em_MagneticBarField.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Christian, Wolfgang; Franciscouembre; Cox, Anne

2009-09-18

148

Aortic Vessel Wall Magnetic Resonance Imaging at 3.0 Tesla  

PubMed Central

The purpose of this study was to evaluate a free-breathing three-dimensional (3D) dual inversion recovery (DIR) segmented k-space gradient-echo (TFE) imaging sequence at 3.0 Tesla for the quantification of aortic vessel wall dimensions. The effect of respiratory motion suppression on image quality was tested. Furthermore, the reproducibility of the aortic vessel wall measurements was investigated. Seven healthy subjects underwent 3D DIR TFE imaging of the aortic vessel wall with and without respiratory navigator. Subsequently, this sequence with respiratory navigator was performed twice in 10 healthy subjects to test its reproducibility. Signal-to-noise (SNR), contrast-to-noise ratio (CNR), vessel wall sharpness and vessel wall volume (VWV) were assessed. Data were compared using the paired t-test and the reproducibility of VWV measurements was evaluated using intra-class correlation coefficients (ICC). SNR, CNR, and vessel wall sharpness were superior in scans performed with respiratory navigator compared to scans performed without. The ICC’s concerning intra-, inter-observer and interscan reproducibility were excellent (resp.0.99, 0.94, 0.95). In conclusion, respiratory motion suppression substantially improves image quality of 3D DIR TFE imaging of the aortic vessel wall at 3.0 Tesla. Furthermore, this optimized technique with respiratory motion suppression enables assessment of aortic vessel wall dimensions with high reproducibility.

Roes, Stijntje D.; Westenberg, Jos J.M.; Doornbos, Joost; van der Geest, Rob J.; Angelie, Emmanuelle; de Roos, Albert; Stuber, Matthias

2008-01-01

149

Mapping Magnetic Field Lines  

NSDL National Science Digital Library

This is an activity about electromagnetism. Learners will use a compass to map the magnetic field lines surrounding a coil of wire that is connected to a battery. This activity requires a large coil or spool of wire, a source of electricity such as 3 D-cell batteries or an AC to DC power adapter, alligator-clipped wire, and magnetic compasses. This is the third lesson in the second session of the Exploring Magnetism teachers guide.

150

Science up to 100 tesla  

SciTech Connect

100 Tesla is the highest attainable field that can be held for milli-sec in a non-destructive magnet. The strongest steels turn soft under stresses of 4GPa, which is the magnetic pressure of 100 T. Until there is a breakthrough in materials, magnets having all the low temperature and high pressure trimmings will be limited to about 100 T. Within the field range 1-100 T far more resources are now devoted to producing the highest possible continuous fields (40+5 T) than to producing longer pulsed fields above 50 T. This illustrates that the utility of the field can be more important than the strength of the field to researchers in condensed matter. Discoveries are typically made in new territory, but this can be new combinations of pressure, temperature, and magnetic field, or new probes and new materials. If any activity has kept up with the proliferation of new experiments and new facilities in high magnetic field research it is the listing of experiments that could and should be done in high fields. Part of the reason for the vitality of high field research is that high fields provide a generic environment. Compared to particle accelerators and plasma machines a high field laboratory is a setting for generic science, like synchrotron light sources or neutron scattering centers. Although the latter two installations probes states, while a magnetic field creates a state. Because it is unrealistic to try to list all the science opportunities at high fields, the author list sources for lists in the public domain and gives a few examples.

Campbell, L.J. [Los Alamos National Lab., NM (United States). National High Magnetic Field Lab.

1995-05-01

151

Magnetic Field Lines  

NSDL National Science Digital Library

This activity will introduce students to the idea of magnetic field lines--a concept they have probably encountered but may not fully grasp. Completing this activity and reading the corresponding background information should enable students to understand

Horton, Michael

2009-05-30

152

Solar Magnetic Fields.  

National Technical Information Service (NTIS)

The research work was directed towards the following: (1) Perform necessary laboratory experiments, including a study on the Zeeman effect in absorption. Make observations of the sunspot and general magnetic fields of the sun. (2) Conduct a program of int...

M. Cimino

1966-01-01

153

Coronal magnetic fields  

Microsoft Academic Search

The use of coronal X-ray emission in determining the configuration of the magnetic field lines in the corona is discussed. Spatially-resolved X-ray observations provided by Skylab and subsequently by missions such as OSO-8 and SMM show the solar corona to be inhomogeneous, with open and closed structures determined by the topology of the magnetic field. The scenario provided by observations

R. Pallavicini

1986-01-01

154

Solar Wind Magnetic Fields  

NASA Technical Reports Server (NTRS)

The magnetic fields originate as coronal fields that are converted into space by the supersonic, infinitely conducting, solar wind. On average, the sun's rotation causes the field to wind up and form an Archimedes Spiral. However, the field direction changes almost continuously on a variety of scales and the irregular nature of these changes is often interpreted as evidence that the solar wind flow is turbulent.

Smith, E. J.

1995-01-01

155

Development of a 3 tesla - 10 Hz pulsed magnet-modulator system  

SciTech Connect

In order to support the experimental work done at the Los Alamos Meson Physics Facility new instrumentation and data collection systems of advanced design are developed on a regular basis. Within the instrumentation system for an experiment at LAMPF, The Photo-Excitation of the H/sup -/ Ion Resonances, there exists a need for a pulsed air-core electromagnet and modulator system. The magnet must be capable of producing a field strength of 0 to 3T in a volume of 3.5 cm/sup 3/. In addition it must be radiation resistant, have a uniform field, operate in a high vacuum with little or no outgassing, and the physical layout of the magnet must provide minimal azimuthal obstruction to both the ion and laser beams. The modulator must be capable of producing up to a 15KA pulse with duration of two ..mu..s at a maximum repetition rate of 10 Hz. Modulator layout must be extremely reliable so that data collection time is not lost during the experiment. This paper describes in detail the development of the system.

Krausse, G.J.; Butterfield, K.B.

1984-01-01

156

The nonequilibrium of magnetic fields  

Microsoft Academic Search

The more subtle properties of magnetic fields which create nonequilibrium and lead to vigorous activity in otherwise sluggish gas-field systems are evaluated for gross hydromagnetic effects. The gentle manipulation of magnetic fields on a large scale leads to the production of small scale variations and discontinuities, providing intense dissipation of magnetic field in a large scale system. A magnetic field

E. N. Parker

1981-01-01

157

Magnetic resonance microimaging of human skin vasculature in vivo at 3 Tesla.  

PubMed

MRI can be used to investigate human skin microvasculature in vivo, provided adequate spatial resolution. Therefore, the sensitivity of the experiment has to be optimized to achieve sufficient signal-to-noise ratio (SNR) within reasonable measurement time to minimize motion artifacts, improve patient comfort and save costs. In this work, the high sensitivity of a 15 mm surface coil and the signal strength of a 3 Tesla scanner, together with a three-dimensional gradient echo sequence and post-processing have been combined to obtain high SNR. Images of human skin with isotropic spatial resolution of 100 ?m were acquired within 10 min and the cutaneous vasculature could be visualized in 3D [Correction made here after initial online publication.], based on three averaged scans. The presented method can be used for diagnosis and, due to its non-invasiveness, treatment monitoring of vascular pathologies in the skin, such as inflammation, vascular malformation, or neoangiogenesis in superficial tumors. PMID:21254205

Laistler, Elmar; Loewe, Robert; Moser, Ewald

2011-06-01

158

Microinhomogeneities in Magnetic Fields  

Microsoft Academic Search

Small variations in the fields of magnets, caused by structures or domains in the pole faces, were investigated by moving a small coil in a circular path. It was found that for a given pole face the variations in the field were all about the same size, and decreased exponentially from the pole face. None of the materials tested as

H. H. Brown Jr.; F. Bitter

1956-01-01

159

Magnetic Field Solver  

NASA Technical Reports Server (NTRS)

The Magnetic Field Solver computer program calculates the magnetic field generated by a group of collinear, cylindrical axisymmetric electromagnet coils. Given the current flowing in, and the number of turns, axial position, and axial and radial dimensions of each coil, the program calculates matrix coefficients for a finite-difference system of equations that approximates a two-dimensional partial differential equation for the magnetic potential contributed by the coil. The program iteratively solves these finite-difference equations by use of the modified incomplete Cholesky preconditioned-conjugate-gradient method. The total magnetic potential as a function of axial (z) and radial (r) position is then calculated as a sum of the magnetic potentials of the individual coils, using a high-accuracy interpolation scheme. Then the r and z components of the magnetic field as functions of r and z are calculated from the total magnetic potential by use of a high-accuracy finite-difference scheme. Notably, for the finite-difference calculations, the program generates nonuniform two-dimensional computational meshes from nonuniform one-dimensional meshes. Each mesh is generated in such a way as to minimize the numerical error for a benchmark one-dimensional magnetostatic problem.

Ilin, Andrew V.

2006-01-01

160

Cerebral magnetic resonance: comparison of high and low field strength imaging.  

PubMed

Low field strength (0.12 Tesla resistive) and high field strength (1.0, 1.4, or 1.5 Tesla superconductive) magnetic resonance imagers were compared for their ability to detect central nervous system lesions. Sixteen adult patients with known lesions and three normal volunteers were studied. Contrast-enhanced computed tomography was used as the standard. The data demonstrate that imaging at high magnetic field strength is superior to low field strength imaging for the detection and delineation of lesions. This finding can be explained by the superior signal-to-noise ratio achievable at the higher magnetic field strengths. High field MR imaging was also found to outperform CT in demonstrating anatomic details and relationships. It is predicted that the use of low saturation (e.g., long TR spin echo technique) will make the gain in contrast-to-noise ratio even more significant. PMID:6541355

Bilaniuk, L T; Zimmerman, R A; Wehrli, F W; Goldberg, H I; Grossman, R I; Bottomley, P A; Edelstein, W A; Glover, G H; MacFall, J R; Redington, R W

1984-11-01

161

Magnetic Field-Induced Superconductivity in the Ferromagnet URhGe  

NASA Astrophysics Data System (ADS)

In several metals, including URhGe, superconductivity has recently been observed to appear and coexist with ferromagnetism at temperatures well below that at which the ferromagnetic state forms. However, the material characteristics leading to such a state of coexistence have not yet been fully elucidated. We report that in URhGe there is a magnetic transition where the direction of the spin axis changes when a magnetic field of 12 tesla is applied parallel to the crystal b axis. We also report that a second pocket of superconductivity occurs at low temperature for a range of fields enveloping this magnetic transition, well above the field of 2 tesla at which superconductivity is first destroyed. Our findings strongly suggest that excitations in which the spins rotate stimulate superconductivity in the neighborhood of a quantum phase transition under high magnetic field.

Lévy, F.; Sheikin, I.; Grenier, B.; Huxley, A. D.

2005-08-01

162

Effect of a high-intensity static magnetic field on sciatic nerve regeneration in the rat  

SciTech Connect

The effect of a high-intensity static magnetic field on peripheral nerve regeneration is evaluated in rat sciatic nerve. Forty-four rats underwent sciatic nerve repair using polyethylene nerve guides. Postoperatively, the animals were exposed to a 1-tesla magnetic field for 12 hours per day for 4 weeks with appropriate controls. Our results demonstrate that a 1-tesla static magnetic field has no statistically significant effect on nerve regeneration as determined by myelinated axon counts and electrophysiologic studies. Also, the specific orientation of the sciatic nerve with respect to the magnetic field has no influence on axonal growth or nerve conduction. Periods of restraint of 12 hours per day for 4 weeks significantly inhibit weight gain but have no effect on peripheral nerve regeneration.

Cordeiro, P.G.; Seckel, B.R.; Miller, C.D.; Gross, P.T.; Wise, R.E.

1989-02-01

163

Magnetic ionization fronts. I. Parallel magnetic fields  

NASA Astrophysics Data System (ADS)

We solve the continuity equations across an ionization front. By including a plane parallel magnetic field we find significant differences in the allowed velocities of the R- and D-type solutions between the magnetized and non-magnetized cases. These results may have implications for the study of ionization bounded diffuse sources where a moderate or strong magnetic field is expected.

Redman, M. P.; Williams, R. J. R.; Dyson, J. E.; Hartquist, T. W.; Fernandez, B. R.

1998-03-01

164

Eruptive solar magnetic fields  

NASA Technical Reports Server (NTRS)

The quasi-steady evolution of solar magnetic fields in response to gradual photospheric changes is considered, with particular attention given to the threshold of a sudden eruption in the solar atmosphere. The formal model of an evolving, force-free field dependent on two Cartesian coordinates is extended to a field which is not force free but in static equilibrium with plasma pressure and gravity. The basic physics is illustrated through the evolution of a loop-shaped electric current sheet enclosing a potential bipolar field with footpoints rooted in the photosphere. A free-boundary problem is posed and then solved for the equilibrium configuration of the current sheet in a hydrostatically supported isothermal atmosphere. As the footpoints move apart to spread a constant photospheric magnetic flux over a larger region, the equilibria available extend the field to increasing heights.

Low, B. C.

1981-01-01

165

The Sun and Magnetic Fields  

NSDL National Science Digital Library

In this activity about magnetic fields and their relation to the Sun, learners will simulate sunspots by using iron filings to show magnetic fields around a bar or cow magnet, and draw the magnetic field surrounding two dipole magnets, both in parallel and perpendicular alignments. Finally, learners examine images of sunspots to relate their magnetic field drawings and observations to what is seen on the Sun.

166

HMI Magnetic Field Products  

NASA Astrophysics Data System (ADS)

The Helioseismic and Magnetic Imager (HMI) on SDO has measured magnetic field, velocity, and intensity in the photosphere over the full disk continuously since May 2010 with arc-second resolution. Scalar images are measured every 45 seconds. From these basic observables the pipeline automatically identifies and tracks active regions on the solar disk. The vector magnetic field and a variety of summary quantities are determined every 720s in these tracked Space-weather HMI Active Region Patches (SHARPS). Synoptic and synchronic maps are constructed daily and after each Carrington Rotation Most data products are available with definitive scientific calibration after a few day deal at and in a quick-look near-real-time version a few minutes after the observations are made. Uncertainties are determined for the derived products. All of the magnetic field products along with movies and images suitable for browsing are available at http:://Hmi.stanford.edu/magnetic. Other products, e.g. coronal field over active regions, can be computed on demand.

Hoeksema, Jon T.; HMI Magnetic Field Team

2013-07-01

167

High magnetic field enhances stationary phase-specific transcription activity of Escherichia coli  

Microsoft Academic Search

When Escherichia coli B was aerobically grown at 37°C under inhomogeneous 5.2–6.1 Tesla (T) magnetic fields in the superconducting magnet biosystem (SBS), the cell number in the stationary phase after the growth had leveled off, was about 3 times higher than that under a geomagnetic field. When the E. coli defective in the rpoS gene which encodes a sigma factor,

Kohji Tsuchiya; Kazumasa Okuno; Takashi Ano; Kan Tanaka; Hideo Takahashi; Makoto Shoda

1999-01-01

168

Magnetic Field and Life  

NSDL National Science Digital Library

This is a lesson where learners explore magnetic forces, fields, and the relationship between electricity. Learners will use this information to infer how the Earth generates a protective magnetic field. The lesson models scientific inquiry using the 5E instructional model and includes teacher notes, prerequisite concepts, common misconceptions, student journal and reading. This is lesson seven in the Astro-Venture Geology Training Unit that were developed to increase students' awareness of and interest in astrobiology and the many career opportunities that utilize science, math and technology skills. The lessons are designed for educators to use with with the Astro-Venture multimedia modules.

169

Spontaneous magnetic field generation in hypervelocity impacts. [of meteoroids onto lunar and planetary surfaces  

NASA Technical Reports Server (NTRS)

Hypervelocity impacts of meteoroids onto early planetary surfaces may have generated short-lived magnetic fields. The high specific power densities of the impacts, plasma production in the ejecta clouds, and the chemically layered targets of the meteoroids are analyzed in describing the evolution of the magnetic fields. Durations from about one millionth of a minute to one minute, as well as strengths up to 100 tesla, are posited for the impact-generated magnetic fields. The analogy of magnetic-field generation in laser-target experiments is also mentioned. The acquisition of shock remanence and thermoremanence by the ejecta and nearby rock following impact is discussed.

Srnka, L. J.

1977-01-01

170

High resolution T2(*)-weighted Magnetic Resonance Imaging at 3 Tesla using PROPELLER-EPI.  

PubMed

We report the application of PROPELLER-EPI for high resolution T2(*)-weighted imaging with sub-millimeter in-plane resolution on a clinical 3 Tesla scanner. Periodically rotated blades of a long-axis PROPELLER-EPI sequence were acquired with fast gradient echo readout and acquisition matrix of 320 × 50 per blade. Images were reconstructed by using 2D-gridding, phase and geometric distortion correction and compensation of resonance frequency drifts that occurred during extended measurements. To characterize these resonance frequency offsets, short FID calibration measurements were added to the PROPELLER-EPI sequence. Functional PROPELLER-EPI was performed with volunteers using a simple block design of right handed finger tapping. Results indicate that PROPELLER-EPI can be employed for fast, high resolution T2(*)-weighted imaging provided geometric distortions and possible resonance frequency drifts are properly corrected. Even small resonance frequency drifts below 10 Hz as well as non-corrected geometric distortions degraded image quality substantially. In the initial fMRI experiment image quality and signal-to-noise ratio was sufficient for obtaining high resolution functional activation maps. PMID:24439698

Krämer, Martin; Reichenbach, Jürgen R

2014-05-01

171

Determination of the tesla-to-ampere ratio for the KRISS\\/VNIIM ?'P-experiment  

Microsoft Academic Search

Tesla-to-ampere ratio giving the largest error in the ?'P-low-field-experiment has been determined using a modified noncontacting method. The total uncertainty of 0.164×10 -6 has been attained. The constant of a solenoid and the ?'P-value have been corrected for magnetic susceptibility of air. The result is ?'P=2.675 154 18×108 s-1 T-1 (Tesla BI-90) with the total uncertainty of 0.18×10-6

Vladlen Y. Shifrin; Po Gyu Park; V. N. Khorev; Chang Ho Choi; Sekyung Lee

1999-01-01

172

Oxford pulsed magnetic field facility  

NASA Astrophysics Data System (ADS)

We give here a description of the newly commissioned 60 tesla or more pulsed field facility constructed over the last three years. It comprises a 800 kJ 32 mF capacitor bank, a high current switch using either an ignitron or thyristor stack, and a crowbar circuit. The system is designed to be flexible enough to cope with a wide variety of coils allowing pulse lengths of up to 100 ms to be produced. The design philosophy, control, monitoring, data collection, and safety will be discussed.

Siertsema, W. John; Jones, Harry

1994-07-01

173

The interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

Large-scale properties of the interplanetary magnetic field as determined by the solar wind velocity structure are examined. The various ways in which magnetic fields affect phenomena in the solar wind are summarized. The dominant role of high and low velocity solar wind streams that persist, with fluctuations and evolution, for weeks or months is emphasized. It is suggested that for most purposes the sector structure is better identified with the stream structure than with the magnetic polarity and that the polarity does not necessarily change from one velocity sector to the next. Several mechanisms that might produce the stream structure are considered. The interaction of the high and low velocity streams is analyzed in a model that is steady state when viewed in a frame that corotates with the sun.

Davis, L., Jr.

1972-01-01

174

HD1: design and fabrication of a 16 Tesla Nb3Sn dipole magnet  

Microsoft Academic Search

The Lawrence Berkeley National Laboratory (LBNL) Superconducting Magnet Group has completed the design, fabrication and test of HD1, a 16 T block-coil dipole magnet. State of the art Nb3Sn conductor was wound in double-layer racetrack coils and supported by an iron yoke and a tensioned aluminum shell. In order to prevent conductor movement under magnetic forces up to the design

A. R. Hafalia; S. E. Bartlett; S. Caspi; L. Chiesa; D. R. Dietderich; P. Ferracin; M. Goli; S. A. Gourlay; C. R. Hannaford; H. Higley; A. F. Lietzke; N. Liggins; S. Mattafirri; A. D. McInturff; M. Nyman; G. L. Sabbi; R. M. Scanlan; J. Swanson

2004-01-01

175

The Earth's Magnetic Field  

NSDL National Science Digital Library

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

Johnson, Roberta

2000-07-01

176

The Heliospheric Magnetic Field  

NASA Astrophysics Data System (ADS)

The Heliospheric Magnetic Field (HMF) is the physical framework in which energetic particles and cosmic rays propagate. Changes in the large scale structure of the magnetic field lead to short- and long term changes in cosmic ray intensities, in particular in anti-phase with solar activity. The origin of the HMF in the corona is well understood and inner heliospheric observations can generally be linked to their coronal sources. The structure of heliospheric magnetic polarities and the heliospheric current sheet separating the dominant solar polarities are reviewed here over longer than a solar cycle, using the three dimensional heliospheric observations by Ulysses. The dynamics of the HMF around solar minimum activity is reviewed and the development of stream interaction regions following the stable flow patterns of fast and slow solar wind in the inner heliosphere is described. The complex dynamics that affects the evolution of the stream interaction regions leads to a more chaotic structure of the HMF in the outer heliosphere is described and discussed on the basis of the Voyager observations. Around solar maximum, solar activity is dominated by frequent transients, resulting in the interplanetary counterparts of Coronal Mass Ejections (ICMEs). These produce a complex aperiodic pattern of structures in the inner heliosphere, at all heliolatitudes. These structures continue to interact and evolve as they travel to the outer heliosphere. However, linking the observations in the inner and outer heliospheres is possible in the case of the largest solar transients that, despite their evolutions, remain recognizably large structures and lead to the formation of Merged Interaction Regions (MIRs) that may well form a quasi-spherical, "global" shell of enhanced magnetic fields around the Sun at large distances. For the transport of energetic particles and cosmic rays, the fluctuations in the magnetic field and their description in alternative turbulent models remains a very important research topic. These are also briefly reviewed in this paper.

Balogh, André; Erdõs, Géza

2013-06-01

177

[Nikola Tesla in medicine, too].  

PubMed

Using primary and secondary sources we have shown in this paper the influence of Nikola Tesla's work on the field of medicine. The description of his experiments conduced within secondary-school education programs aimed to present the popularization of his work in Croatia. Although Tesla was dedicated primarily to physics and was not directly involved in biomedical research, his work significantly contributed to paving the way of medical physics particularly radiology and high-frequency electrotherapy. PMID:18383745

Hanzek, Branko; Jakobovi?, Zvonimir

2007-12-01

178

Visual language and handwriting movement: functional magnetic resonance imaging at 3 tesla during generation of ideographic characters.  

PubMed

A functional magnetic resonance imaging experiment at 3 tesla was performed to investigate the collaborative mechanism between visuospatial processing and motor execution in performing visual language generation tasks. Japanese Kanji, ideographic characters, were utilized to design tasks. The bilateral border portions between the inferior parietal lobule and the occipital lobe were involved during a Kanji puzzle task, which required subjects to combine several parts into a Kanji. The higher motor areas, such as the premotor areas and the pre-supplementary motor areas, were also activated bilaterally during the puzzle task. The parieto-occipital activation may be related to analysis of configuration or segmentation/integration of Kanji figures. Activation in the higher motor areas may be induced by cognitive components related to motor function to perform the visuospatial language task, such as intense reference for displayed characters and finding a proper character for puzzle solution. A collaborative mechanism in these areas may explain the effectiveness of tactile reading in letter recognition by patients with pure alexia or kinesthetic facilitation by Kanji users when recalling difficult Kanji. PMID:11543956

Matsuo, K; Kato, C; Tanaka, S; Sugio, T; Matsuzawa, M; Inui, T; Moriya, T; Glover, G H; Nakai, T

2001-07-01

179

Effect of super high magnetic field on the growth of Escherichia coli  

Microsoft Academic Search

Summary Auxotrophic mutants ofEscherichia coli were grown under the super high magnetic field (11.7 Tesla) and the effect of the field both on the growth and mutation frequency of the bacteria was investigated. When the bacteria were cultivated in complex media, the growth was stimulated under 11.7T in comparison with that in geomagnetic field. When the bacteria were grown in

Kazumasa Okuno; Takashi Ano; Makoto Shoda

1991-01-01

180

Quench problems of Nb3 Sn cosine theta high field dipole model magnets  

SciTech Connect

We have developed and tested several cosine theta high field dipole model magnets for accelerator application, utilizing Nb{sub 3}Sn strands made by MJR method and PIT method. With Rutherford cables made with PIT strand we achieved 10.1 Tesla central field at 2.2 K operation, and 9.5 Tesla at 4.5 K operation. The magnet wound with the MJR cable prematurely quenched at 6.8 Tesla at 4.5 K due to cryo-instability. Typical quench behaviors of these magnets are described for both types of magnets, HFDA-04 of MJR and HFDA-05 of PIT. Their characteristics parameters are compared on d{sub eff}, RRR, thermal conductivity and others, together with other historical Nb{sub 3}Sn magnets. It is suggested a larger RRR value is essential for the stability of the epoxy impregnated high field magnets made with high current density strands. It is shown that a magnet with a larger RRR value has a longer MPZ value and more stable, due to its high thermal conductivity and low resistivity.

Yamada, Ryuji; /Fermilab; Wake, Masayoshi; /KEK, Tsukuba

2004-12-01

181

Magnetic Field of the Earth  

NSDL National Science Digital Library

Students can learn about how the magnetic field of the earth is similar to magnets. Go to the following link: Magnetic Field of the Earth 1. What makes the earth like a magnet? 2. How do we measure magnetism? Be sure to check out the fun games and activities on this web site too!! Now click on the following link and listen to a 2 minute presentation about magnetism: Pulse Planet Next go to ...

Merritt, Mrs.

2005-10-18

182

Transformative effects of higher magnetic field in Fourier transform ion cyclotron mass spectrometry  

PubMed Central

The relationship of magnetic field strength and Fourier transform ion cyclotron resonance mass spectrometry performance was tested using three instruments with the same designs but different fields of 4.7, 7 and 9.4 tesla. We found that the theoretically predicted “transformative” effects of magnetic field are indeed observed experimentally. The most striking effects were that mass accuracy demonstrated approximately 2nd–3rd-order improvement with the magnetic field, depending upon the charge state of the analyte, and that peak splitting, which prohibited automated data analysis at 4.7 T, was not observed at 9.4 T.

Karabacak, N. Murat; Easterling, Michael L.; Agar, N.Y.R.; Agar, Jeffrey N.

2010-01-01

183

[Nikola Tesla: flashes of inspiration].  

PubMed

Nikola Tesla (1856-1943) was one of the greatest inventors in history and a key player in the revolution that led to the large-scale use of electricity. He also made important contributions to such diverse fields as x-rays, remote control, radio, the theory of consciousness or electromagnetism. In his honour, the international unit of magnetic induction was named after him. Yet, his fame is scarce in comparison with that of other inventors of the time, such as Edison, with whom he had several heated arguments. He was a rather odd, reserved person who lived for his inventions, the ideas for which came to him in moments of inspiration. In his autobiography he relates these flashes with a number of neuropsychiatric manifestations, which can be seen to include migraine auras, synaesthesiae, obsessions and compulsions. PMID:23307357

Villarejo-Galende, Albero; Herrero-San Martín, Alejandro

2013-01-16

184

Comparison Between and Strands and Cables for High Field Accelerator Magnets  

Microsoft Academic Search

The Nb3Al small racetrack magnet, SR07, has been successfully built and tested to its short sample limit beyond 10 Tesla without any training. Thus the practical application of Nb3Al strands for high field accelerator magnets is established. The characteristics of the representative F4 strand and cable, are compared with the typical Nb3Sn strand and cable. It is represented by the

Ryuji Yamada; Akihiro Kikuchi; Emanuela Barzi; Guram Chlachidze; Allen Rusy; Takao Takeuchi; Michael Tartaglia; Daniel Turrioni; Vesselin Velev; Masayoshi Wake; Alexander A. Zlobin

2010-01-01

185

Single voxel magnetic resonance spectroscopy at 3 Tesla in a memory disorders clinic: early right hippocampal NAA/Cr loss in mildly impaired subjects.  

PubMed

In this study, we use magnetic resonance spectroscopy (MRS) at 3 Tesla to measure N-acetyl aspartate (NAA), myo-inositol (mI) and choline (Cho) to creatine (Cr) ratios in R (right) and L (left) hippocampi (H) in 8 mildly memory impaired (MMI), 6 probable Alzheimer's Disease (PRAD), and 17 control subjects. NAA/Cr was significantly reduced in the RH in the MMI group and bilaterally in the PRAD group vs. controls. No other metabolite differences were noted between the three groups. Five MMI subjects have converted to PRAD in follow-up. These findings suggest that RH NAA/Cr ratios measured at 3 Tesla may be a sensitive marker of future progression to dementia in a clinically defined population with isolated memory complaints. PMID:18930637

Caserta, Maria T; Ragin, Ann; Hermida, Adriana P; Ahrens, R John; Wise, Leon

2008-11-30

186

Design of a prototype 20 Tesla, single turn, toroidal field coil for the Fusion Ignition Experiment (IGNITEX)  

Microsoft Academic Search

The electromagnetic design of the Fusion Ignition Experiment (IGNITEX) combines unconventional pulsed-power and magnet technologies. The experiment should produce an ignited plasma in a relatively simple and low-cost way. The proposed IGNITEX toroidal field (TF) coil is a 20-T, single-turn, toroidal magnet powered by homopolar generators (HPGs). In order to demonstrate the magnet technologies, a 0.06-scale prototype toroidal field coil

M. D. Werst; G. W. Brunson; K. T. Hsieh; R. L. Sledge; W. F. Weldon

1989-01-01

187

THE GALACTIC MAGNETIC FIELD  

SciTech Connect

With this Letter, we complete our model of the Galactic magnetic field (GMF), by using the WMAP7 22 GHz total synchrotron intensity map and our earlier results to obtain a 13-parameter model of the Galactic random field, and to determine the strength of the striated random field. In combination with our 22-parameter description of the regular GMF, we obtain a very good fit to more than 40,000 extragalactic Faraday rotation measures and the WMAP7 22 GHz polarized and total intensity synchrotron emission maps. The data call for a striated component to the random field whose orientation is aligned with the regular field, having zero mean and rms strength Almost-Equal-To 20% larger than the regular field. A noteworthy feature of the new model is that the regular field has a significant out-of-plane component, which had not been considered earlier. The new GMF model gives a much better description of the totality of data than previous models in the literature.

Jansson, Ronnie; Farrar, Glennys R. [Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, NY 10003 (United States)

2012-12-10

188

Magnetic Field Topology in Jets  

NASA Technical Reports Server (NTRS)

We present results on the magnetic field topology in a pulsed radiative. jet. For initially helical magnetic fields and periodic velocity variations, we find that the magnetic field alternates along the, length of the jet from toroidally dominated in the knots to possibly poloidally dominated in the intervening regions.

Gardiner, T. A.; Frank, A.

2000-01-01

189

The WIND magnetic field investigation  

Microsoft Academic Search

The magnetic field experiment on WIND will provide data for studies of a broad range of scales of structures and fluctuation characteristics of the interplanetary magnetic field throughout the mission, and, where appropriate, relate them to the statics and dynamics of the magnetosphere. The basic instrument of the Magnetic Field Investigation (MFI) is a boom-mounted dual triaxial fluxgate magnetometer and

R. P. Lepping; M. H. Ac?na; L. F. Burlaga; W. M. Farrell; J. A. Slavin; K. H. Schatten; F. Mariani; N. F. Ness; F. M. Neubauer; Y. C. Whang; J. B. Byrnes; R. S. Kennon; P. V. Panetta; J. Scheifele; E. M. Worley

1995-01-01

190

Low field magnetic resonance imaging  

DOEpatents

A method and system of magnetic resonance imaging does not need a large homogenous field to truncate a gradient field. Spatial information is encoded into the spin magnetization by allowing the magnetization to evolve in a non-truncated gradient field and inducing a set of 180 degree rotations prior to signal acquisition.

Pines, Alexander (Berkeley, CA); Sakellariou, Dimitrios (Billancourt, FR); Meriles, Carlos A. (Fort Lee, NJ); Trabesinger, Andreas H. (London, GB)

2010-07-13

191

Electric and magnetic fields  

NASA Technical Reports Server (NTRS)

A number of energy momentum anomalies are described that result from the use of Abraham-Lorentz electromagnetic theory. These anomalies have in common the motion of charged bodies or current carrying conductors relative to the observer. The anomalies can be avoided by using the nonflow approach, based on internal energy of the electromagnetic field. The anomalies can also be avoided by using the flow approach, if all contributions to flow work are included. The general objective of this research is a fundamental physical understanding of electric and magnetic fields which, in turn, might promote the development of new concepts in electric space propulsion. The approach taken is to investigate quantum representations of these fields.

Kaufman, H. R.; Robinson, R. S.; Etters, R. D.

1982-01-01

192

Predesign study of a 4-5 Tesla superconducting Wiggler magnet for the ESRF.  

National Technical Information Service (NTIS)

The European Synchrotron Radiation Facility will provide a beam line for very hard photons well above 250 keV which requires a high field three pole wavelength shifter. The nominal and design fields of the proposed wiggler are 4 and 5 T respectively while...

A. Ravex R. Lagnier P. Elleaume H. H. J. Ten Kate D. Ter Avest

1993-01-01

193

Reactivation and operation of the large six-tesla CFFF superconducting magnet  

SciTech Connect

The second MHD superconducting magnet system constructed at the Argonne National Laboratory, originally intended for use in the coal-fired plasma MHD power generation program, has been in storage at Argonne since its assembly and short-term testing a decade ago. At that time it was energized for only a few days and then decommissioned. The magnet, a 6-T dipole having an effective length of 300 cm and a tapered warm bore of 80 to 100 cm, has recently been reactivated and put into service for sea water MHD propulsion research. This report describes the technical aspects of the reactivation process, as well as the operational characterization of the reconstituted system.

Hill, D.; Libera, J.; Petrick, M.

1992-01-01

194

Reactivation and operation of the large six-tesla CFFF superconducting magnet  

SciTech Connect

The second MHD superconducting magnet system constructed at the Argonne National Laboratory, originally intended for use in the coal-fired plasma MHD power generation program, has been in storage at Argonne since its assembly and short-term testing a decade ago. At that time it was energized for only a few days and then decommissioned. The magnet, a 6-T dipole having an effective length of 300 cm and a tapered warm bore of 80 to 100 cm, has recently been reactivated and put into service for sea water MHD propulsion research. This report describes the technical aspects of the reactivation process, as well as the operational characterization of the reconstituted system.

Hill, D.; Libera, J.; Petrick, M.

1992-07-01

195

Extreme Material Physical Properties and Measurements above 100 tesla  

NASA Astrophysics Data System (ADS)

The National High Magnetic Field Laboratory (NHMFL) Pulsed Field Facility (PFF) at Los Alamos National Laboratory (LANL) offers extreme environments of ultra high magnetic fields above 100 tesla by use of the Single Turn method as well as fields approaching 100 tesla with more complex methods. The challenge of metrology in the extreme magnetic field generating devices is complicated by the millions of amperes of current and tens of thousands of volts that are required to deliver the pulsed power needed for field generation. Methods of detecting physical properties of materials are essential parts of the science that seeks to understand and eventually control the fundamental functionality of materials in extreme environments. De-coupling the signal of the sample from the electro-magnetic interference associated with the magnet system is required to make these state-of-the-art magnetic fields useful to scientists studying materials in high magnetic fields. The cutting edge methods that are being used as well as methods in development will be presented with recent results in Graphene and High-Tc superconductors along with the methods and challenges.

Mielke, Charles

2011-03-01

196

High-magnetic-field MHD-generator program  

NASA Astrophysics Data System (ADS)

Progress in an experimental and theoretical program designed to investigate MHD channel phenomena which are important at high magnetic fields is described. The areas of research include nonuniformity effects, boundary layers, Hall field breakdown, the effects of electrode configuration and current concentrations, and studies of steady-state combustion disk and linear channels in an existing 6 Tesla magnet of small dimensions. In the study of the effects of nonuniformities, experiments were performed to test a multi-channel, fiber optics diagnostic system that yields time-resolved temperature profiles in an MHD chanel. For the study of magneto-acoustic fluctuation phenomena, a one dimensional model was developed to describe the performance of a non-ideal MHD generator with a generalized electrical configuration. A two dimensional MHD computer code was developed which predicts the dependence on electrode and insulator dimensions of the onset of interelectrode Hall field breakdown, as initiated either by breakdown in the insulator or in the plasma.

Nakamura, T.; Eustis, R. H.; Mitchner, M.; Self, S. A.; Koester, J. K.; Kruger, C. H.

1981-07-01

197

Fast superconducting magnetic field switch  

SciTech Connect

The superconducting magnetic switch or fast kicker magnet is employed with an electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater than the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles. Magnetic switches and particularly fast kicker magnets are used in the accelerator industry to quickly deflect particle beams into and out of various transport lines, storage rings, dumps, and specifically to differentially route individual bunches of particles from a train of bunches which are injected or ejected from a given ring.

Goren, Y.; Mahale, N.K.

1995-12-31

198

Apparatus and method for magnetically processing a specimen  

DOEpatents

An apparatus for magnetically processing a specimen that couples high field strength magnetic fields with the magnetocaloric effect includes a high field strength magnet capable of generating a magnetic field of at least 1 Tesla and a magnetocaloric insert disposed within a bore of the high field strength magnet. A method for magnetically processing a specimen includes positioning a specimen adjacent to a magnetocaloric insert within a bore of a magnet and applying a high field strength magnetic field of at least 1 Tesla to the specimen and to the magnetocaloric insert. The temperature of the specimen changes during the application of the high field strength magnetic field due to the magnetocaloric effect.

Ludtka, Gerard M; Ludtka, Gail M; Wilgen, John B; Kisner, Roger A; Jaramillo, Roger A

2013-09-03

199

Photonic Magnetic Field Sensor  

NASA Astrophysics Data System (ADS)

Small, in-line polarization rotators or isolators to reduce feedback in fiber optic links can be the basis for excellent magnetic field sensors. Based on the giant magneto-optical (GMO) or Faraday effect in iron garnets, they with a magnetic field of a few hundred Gauss, (20 mT) for an interaction length for an optical beam of a few millimeters achieve a polarization rotation or phase shift of 45 deg (1/8 cycle). When powered by a small laser diode, with the induced linear phase shift recovered at the shot noise limit, we have demonstrated sensitivities at the 3.3 nT/Hz1/2 level for frequencies from less than 1 Hz to frequencies into the high kHz range. Through further improvements; an increase in interaction length, better materials and by far the greatest factor, the addition of a flux concentrator, sensitivities at the pT/Hz1/2 level appear to be within reach. We will detail such a design and discuss the issues that may limit achieving these goals.

Wyntjes, Geert

2002-02-01

200

The Heliospheric Magnetic Field  

NASA Astrophysics Data System (ADS)

The heliospheric magnetic field (HMF) is the extension of the coronal magnetic field carried out into the solar system by the solar wind. It is the means by which the Sun interacts with planetary magnetospheres and channels charged particles propagating through the heliosphere. As the HMF remains rooted at the solar photosphere as the Sun rotates, the large-scale HMF traces out an Archimedean spiral. This pattern is distorted by the interaction of fast and slow solar wind streams, as well as the interplanetary manifestations of transient solar eruptions called coronal mass ejections. On the smaller scale, the HMF exhibits an array of waves, discontinuities, and turbulence, which give hints to the solar wind formation process. This review aims to summarise observations and theory of the small- and large-scale structure of the HMF. Solar-cycle and cycle-to-cycle evolution of the HMF is discussed in terms of recent spacecraft observations and pre-spaceage proxies for the HMF in geomagnetic and galactic cosmic ray records.

Owens, Mathew J.; Forsyth, Robert J.

2013-11-01

201

Magnetic Fields: Visible and Permanent.  

ERIC Educational Resources Information Center

Children will be able to see the concept of a magnetic field translated into a visible reality using the simple method outlined. Standard shelf paper, magnets, iron filings, and paint in a spray can are used to prepare a permanent and well-detailed picture of the magnetic field. (Author/JN)

Winkeljohn, Dorothy R.; Earl, Robert D.

1983-01-01

202

A 3.5 Tesla Laboratory Electromagnet  

NASA Astrophysics Data System (ADS)

We report the design and construction of a laboratory electromagnet utilizing HTS coils in an iron yoke with a magnetic flux density of 3.5 Tesla in a 50-mm air-gap. With continuing improvement in the performance of HTS ``BSCCO'' wire, several niche HTS magnet applications have become viable at current wire prices. In this instance, the HTS conductor confers the advantages of high field strength combined with compact size and energy efficiency, in an electromagnet of a format suitable for many materials' characterization techniques, such as vibrating-sample magnetometry, for which the current magnet will be employed. The magnet employs four HTS coils, with a total of 1.6 km of BSCCO wire, which are conduction cooled using a single-stage Gifford-McMahon cryocooler, delivering approximately 25 W of cooling power at the target 35 K operating temperature; HTS current leads are utilized to minimize heat leak to the cryogenic environment.

Pooke, D. M.; Chamritski, V.; Gibson, S.; Fee, M.; King, T.; Staines, M. P.; Flower, N. E.; Buckley, R. G.

2004-06-01

203

Magnetic Resonance Microscopy at 14 Tesla and Correlative Histopathology of Human Brain Tumor Tissue  

PubMed Central

Magnetic Resonance Microscopy (MRM) can provide high microstructural detail in excised human lesions. Previous MRM images on some experimental models and a few human samples suggest the large potential of the technique. The aim of this study was the characterization of specific morphological features of human brain tumor samples by MRM and correlative histopathology. We performed MRM imaging and correlative histopathology in 19 meningioma and 11 glioma human brain tumor samples obtained at surgery. To our knowledge, this is the first MRM direct structural characterization of human brain tumor samples. MRM of brain tumor tissue provided images with 35 to 40 µm spatial resolution. The use of MRM to study human brain tumor samples provides new microstructural information on brain tumors for better classification and characterization. The correlation between MRM and histopathology images allowed the determination of image parameters for critical microstructures of the tumor, like collagen patterns, necrotic foci, calcifications and/or psammoma bodies, vascular distribution and hemorrhage among others. Therefore, MRM may help in interpreting the Clinical Magnetic Resonance images in terms of cell biology processes and tissue patterns. Finally, and most importantly for clinical diagnosis purposes, it provides three-dimensional information in intact samples which may help in selecting a preferential orientation for the histopathology slicing which contains most of the informative elements of the biopsy. Overall, the findings reported here provide a new and unique microstructural view of intact human brain tumor tissue. At this point, our approach and results allow the identification of specific tissue types and pathological features in unprocessed tumor samples.

Gonzalez-Segura, Ana; Morales, Jose Manuel; Gonzalez-Darder, Jose Manuel; Cardona-Marsal, Ramon; Lopez-Gines, Concepcion; Cerda-Nicolas, Miguel; Monleon, Daniel

2011-01-01

204

Magnetic resonance elastography detected with a SQUID in microtesla magnetic fields  

NASA Astrophysics Data System (ADS)

We have used a SQUID-based microtesla magnetic resonance imaging (MRI) system to perform magnetic resonance elastography (MRE) experiments in a measurement field of 132 microtesla. Magnetic resonance elastography is based on MRI and measures three-dimensional displacement and strain fields in a sample. With appropriate data processing this allows for a quantitative map of the physical response of a material to an applied deformation. In the past, MRE experiments using conventional (1.5 tesla and above) MRI systems have demonstrated that MRE may be used as a non-invasive method for measuring stiffness of human tissues, which may aid in the detection and diagnosis of breast cancer and other cancers. Our MRE experiment consists of applying a small axial deformation to a cylindrical sample of 0.5% agarose gel. For samples approximately 30 mm in height, we were able to measure displacements on the order of 500 micrometers. Supported by USDOE.

Kelso, Nathan; Koski, Kristie; Reimer, Jeffrey

2005-03-01

205

Magnetic Resonance Imaging of Neonatal Encephalopathy at 4.7 Tesla: Initial Experiences  

Microsoft Academic Search

OBJECTIVES.The goals were to develop safe 4.7-T MRI examination protocols for newborn infants and to explore the advantages of this field strength in neonatal encephalopathy. METHODS.Nine ventilated newborn infants with moderate or severe encephalopathy were studied at 4.7 T, with ethical approval and informed parental consent. The custom-made, 4.7-T-compatible, neonatal patient management system included acoustic noise protection and physiologic monitoring.

Alan Bainbridge; Jeanie L. Y. Cheong; Cornelia Hagmann; Rosarie Lombard; Wui K. Chong; John S. Wyatt; Ernest B. Cady; Roger J. Ordidge; Nicola J. Robertson

2010-01-01

206

Magnetic field dependent photoluminescence studies of InGaAs/GaAs strained-single-quantum wells  

SciTech Connect

Magnetoluminescence determined conduction-band and valence-band dispersion curves are presented for n-type InGaAs/GaAs stained-single-quantum well structures. The magnetic field range was 0 to 30 tesla, and the temperature varied between 4.2 and 77.4 K.

Jones, E.D.; Dawson, L.R.; Klem, J.F.; Lyo, S.K. [Sandia National Labs., Albuquerque, NM (United States); Heiman, D.; Liu, X.C. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Francis Bitter National Magnet Lab.

1994-08-01

207

High-field magnets using high-critical-temperature superconducting thin films  

DOEpatents

High-field magnets fabricated from high-critical-temperature superconducting ceramic (HTSC) thin films which can generate fields greater than 4 Tesla are disclosed. The high-field magnets are made of stackable disk-shaped substrates coated with HTSC thin films, and involves maximizing the critical current density, superconducting film thickness, number of superconducting layers per substrate, substrate diameter, and number of substrates while minimizing substrate thickness. The HTSC thin films are deposited on one or both sides of the substrates in a spiral configuration with variable line widths to increase the field. 4 figures.

Mitlitsky, F.; Hoard, R.W.

1994-05-10

208

High-field magnets using high-critical-temperature superconducting thin films  

DOEpatents

High-field magnets fabricated from high-critical-temperature superconducting ceramic (HTSC) thin films which can generate fields greater than 4 Tesla. The high-field magnets are made of stackable disk-shaped substrates coated with HTSC thin films, and involves maximizing the critical current density, superconducting film thickness, number of superconducting layers per substrate, substrate diameter, and number of substrates while minimizing substrate thickness. The HTSC thin films are deposited on one or both sides of the substrates in a spiral configuration with variable line widths to increase the field.

Mitlitsky, Fred (Livermore, CA); Hoard, Ronald W. (Livermore, CA)

1994-01-01

209

Ventricular Assist Device implant (AB 5000) prototype cannula: In vitro assessment of MRI issues at 3Tesla  

Microsoft Academic Search

PURPOSE: To evaluate MRI issues at 3-Tesla for a ventricular assist device (VAD). METHODS: The AB5000 Ventricle with a prototype Nitinol wire-reinforced In-Flow Cannula and Out-Flow Cannula attached (Abiomed, Inc., Danvers, MA) was evaluated for magnetic field interactions, heating, and artifacts at 3-Tesla. MRI-related heating was assessed with the device in a gelled-saline-filled, head\\/torso phantom using a transmit\\/received RF body

Frank G Shellock; Samuel Valencerina

2008-01-01

210

Fast superconducting magnetic field switch  

DOEpatents

The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles.

Goren, Yehuda (Mountain View, CA); Mahale, Narayan K. (The Woodlands, TX)

1996-01-01

211

Fast superconducting magnetic field switch  

DOEpatents

The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles. 6 figs.

Goren, Y.; Mahale, N.K.

1996-08-06

212

Study of the development of fetal baboon brain using magnetic resonance imaging at 3 Tesla  

PubMed Central

Direct observational data on the development of the brains of human and nonhuman primates is on remarkably scant, and most of our understanding of primate brain development is extrapolated from findings in rodent models. Magnetic resonance imaging (MRI) is a promising tool for the noninvasive, longitudinal study of the developing primate brain. We devised a protocol to scan pregnant baboons serially at 3 T for up to 3 h per session. Seven baboons were scanned 1–6 times, beginning as early as 56 days post-conceptional age, and as late as 185 days (term ~185 days). Successful scanning of the fetal baboon required careful animal preparation and anesthesia, in addition to optimization of the scanning protocol. We successfully acquired maps of relaxation times (T1 and T2) and high-resolution anatomical images of the brains of fetal baboons at multiple time points during the course of gestation. These images demonstrated the convergence of gray and white matter contrast near term, and furthermore demonstrated that the loss of contrast at that age is a consequence of the continuous change in relaxation times during fetal brain development. These data furthermore demonstrate that maps of relaxation times have clear advantages over the relaxation time weighted images for the tracking of the changes in brain structure during fetal development. This protocol for in utero MRI of fetal baboon brains will help to advance the use of nonhuman primate models to study fetal brain development longitudinally.

Liu, Feng; Garland, Marianne; Duan, Yunsuo; Stark, Raymond I.; Xu, Dongrong; Dong, Zhengchao; Bansal, Ravi; Peterson, Bradley S.; Kangarlu, Alayar

2008-01-01

213

Evolution of twisted magnetic fields  

SciTech Connect

The magnetic field of the solar corona evolves quasistatically in response to slowly changing photospheric boundary conditions. The magnetic topology is preserved by the low resistivity of the solar atmosphere. We show that a magnetic flux coordinate system simplifies the problem of calculating field evolution with invariant topology. As an example, we calculate the equilibrium of a thin magnetic flux tube with small twist per unit length.

Zweibel, E.G.; Boozer, A.H.

1985-02-01

214

Reconnection of Magnetic Fields  

NASA Astrophysics Data System (ADS)

Preface; Part I. Introduction: 1.1 The Sun E. R. Priest; 1.2 Earth's magnetosphere J. Birn; Part II. Basic Theory of MHD Reconnection: 2.1 Classical theory of two-dimensional reconnection T. G. Forbes; 2.2 Fundamental concepts G. Hornig; 2.3 Three-dimensional reconnection in the absence of magnetic null points G. Hornig; 2.4 Three-dimensional reconnection at magnetic null points D. Pontin; 2.5 Three-dimensional flux tube reconnection M. Linton; Part III. Basic Theory of Collisionless Reconnection: 3.1 Fundamentals of collisionless reconnection J. Drake; 3.2 Diffusion region physics M. Hesse; 3.3 Onset of magnetic reconnection P. Pritchett; 3.4 Hall-MHD reconnection A. Bhattacharjee and J. Dorelli; 3.5 Role of current-aligned instabilities J. Büchner and W. Daughton; 3.6 Nonthermal particle acceleration M. Hoshino; Part IV. Reconnection in the Magnetosphere: 4.1 Reconnection at the magnetopause: concepts and models J. G. Dorelli and A. Bhattacharjee; 4.2 Observations of magnetopause reconnection K.-H. Trattner; 4.3 On the stability of the magnetotail K. Schindler; 4.4 Simulations of reconnection in the magnetotail J. Birn; 4.5 Observations of tail reconnection W. Baumjohann and R. Nakamura; 4.6 Remote sensing of reconnection M. Freeman; Part V. Reconnection in the Sun's Atmosphere: 5.1 Coronal heating E. R. Priest; 5.2 Separator reconnection D. Longcope; 5.3 Pinching of coronal fields V. Titov; 5.4 Numerical experiments on coronal heating K. Galsgaard; 5.5 Solar flares K. Kusano; 5.6 Particle acceleration in flares: theory T. Neukirch; 5.7 Fast particles in flares: observations L. Fletcher; 6. Open problems J. Birn and E. R. Priest; Bibliography; Index.

Birn, J.; Priest, E. R.

2007-01-01

215

Magnetic field effect on the photocrosslinking of a butadiene-styrene copolymer modified by benzoyl or phenylacetyl groups  

Microsoft Academic Search

A butadiene-styrene copolymer was partially modified by Friedel-Crafts reaction of phenyl groups with benzoyl chloride or phenylacetyl chloride. The resulting benzoylphenyl and phenylacetylphenyl groups served as photosensitizers for a subsequent crosslinking by u.v. irradiation. The extent of crosslinking was measured by sol\\/gel analysis. Crosslinking was carried out without magnetic field and with magnetic field of flux density 1.0 Tesla. The

Klaus Hummel; Raimund Schaller; Michael G. Martl

1987-01-01

216

Assessment of the right ventricle with cardiovascular magnetic resonance at 7 Tesla  

PubMed Central

Background Functional and morphologic assessment of the right ventricle (RV) is of clinical importance. Cardiovascular magnetic resonance (CMR) at 1.5T has become gold standard for RV chamber quantification and assessment of even small wall motion abnormalities, but tissue analysis is still hampered by limited spatial resolution. CMR at 7T promises increased resolution, but is technically challenging. We examined the feasibility of cine imaging at 7T to assess the RV. Methods Nine healthy volunteers underwent CMR at 7T using a 16-element TX/RX coil and acoustic cardiac gating. 1.5T served as gold standard. At 1.5T, steady-state free-precession (SSFP) cine imaging with voxel size (1.2x1.2x6) mm3 was used; at 7T, fast gradient echo (FGRE) with voxel size (1.2x1.2x6) mm3 and (1.3x1.3x4) mm3 were applied. RV dimensions (RVEDV, RVESV), RV mass (RVM) and RV function (RVEF) were quantified in transverse slices. Overall image quality, image contrast and image homogeneity were assessed in transverse and sagittal views. Results All scans provided diagnostic image quality. Overall image quality and image contrast of transverse RV views were rated equally for SSFP at 1.5T and FGRE at 7T with voxel size (1.3x1.3x4)mm3. FGRE at 7T provided significantly lower image homogeneity compared to SSFP at 1.5T. RVEDV, RVESV, RVEF and RVM did not differ significantly and agreed close between SSFP at 1.5T and FGRE at 7T (p=0.5850; p=0.5462; p=0.2789; p=0.0743). FGRE at 7T with voxel size (1.3x1.3x4) mm3 tended to overestimate RV volumes compared to SSFP at 1.5T (mean difference of RVEDV 8.2±9.3ml) and to FGRE at 7T with voxel size (1.2x1.2x6) mm3 (mean difference of RVEDV 9.3±8.6ml). Conclusions FGRE cine imaging of the RV at 7T was feasible and provided good image quality. RV dimensions and function were comparable to SSFP at 1.5T as gold standard.

2013-01-01

217

Matter in strong magnetic fields  

Microsoft Academic Search

The properties of matter are drastically modified by strong magnetic fields, B>>m2ee3c\\/h3=2.35×109 G (1 G=10-4 T), as are typically found on the surfaces of neutron stars. In such strong magnetic fields, the Coulomb force on an electron acts as a small perturbation compared to the magnetic force. The strong-field condition can also be mimicked in laboratory semiconductors. Because of the

Dong Lai

2001-01-01

218

Dynamic Shimming of the Human Brain at 7 Tesla  

PubMed Central

Dynamic shim updating (DSU) of the zero- to second-order spherical harmonic field terms has previously been shown to improve the magnetic field homogeneity in the human brain at 4 Tesla. The increased magnetic field inhomogeneity at 7 Tesla can benefit from inclusion of third-order shims during DSU. However, pulsed higher-order shims can generate a multitude of temporally varying magnetic fields arising from eddy-currents that can strongly degrade the magnetic field homogeneity. The first realization of zero- to third-order DSU with full preemphasis and B0 compensation enabled improved shimming of the human brain at 7 Tesla not only in comparison with global (i.e. static) shimming, but also when compared to state-of-the-art zero- to second-order DSU. Temporal shim-to-shim interactions were measured for each of the 16 zero- to third-order shim coils along 1D column projections on a spherical phantom. The decomposition into up to 3 exponentials allowed full preemphasis and B0 compensation of all 16 shims covering 67 potential shim-to-shim interactions. Despite the significant improvements achievable with DSU, the magnetic field homogeneity is still not perfect even when updating all zero- through third-order shims. This is because DSU is still inherently limited by the shallowness of the low order spherical harmonic fields and their inability to compensate the higher-order inhomogeneities encountered in vivo. However, DSU maximizes the usefulness of conventional shim coil systems and provides magnetic field homogeneity that is adequate for a wide range of applications.

Juchem, Christoph; Nixon, Terence W.; Diduch, Piotr; Rothman, Douglas L.; Starewicz, Piotr; de Graaf, Robin A.

2010-01-01

219

Thermal expansion of a La1.87Sr0.13CuO4 single crystal at Tc in high magnetic fields  

Microsoft Academic Search

We present high-resolution dilatometry measurements of a La1.87Sr0.13CuO4-single crystal parallel and perpendicular to the CuO2-planes in magnetic fields up to 14 Tesla. We find a strong suppression of the thermal expansion anomalies for magnetic fields parallel to the c-axis. In contrast, a magnetic field perpendicular to the c-axis affects the anomalies only weakly.

Th. Auweiler; Th. Lorenz; W. Schlabitz; H. Kierspel; B. Büchner; A. Freimuth; H. Micklitz; I. Tanaka; H. Kojima

1994-01-01

220

Magnetic fields around evolved stars  

NASA Astrophysics Data System (ADS)

A number of mechanisms, such as magnetic fields, (binary) companions and circumstellar disks have been suggested to be the cause of non-spherical PNe and in particular collimated outflows. This work investigates one of these mechanisms: the magnetic fields. While MHD simulations show that the fields can indeed be important, few observations of magnetic fields have been done so far. We used the VLBA to observe five evolved stars, with the goal of detecting the magnetic field by means of water maser polarization. The sample consists in four AGB stars (IK Tau, RT Vir, IRC+60370 and AP Lyn) and one pPN (OH231.8+4.2). In four of the five sources, several strong maser features were detected allowing us to measure the linear and/or circular polarization. Based on the circular polarization detections, we infer the strength of the component of the field along the line of sight to be between ~30 mG and ~330 mG in the water maser regions of these four sources. When extrapolated to the surface of the stars, the magnetic field strength would be between a few hundred mG and a few Gauss when assuming a toroidal field geometry and higher when assuming more complex magnetic fields. We conclude that the magnetic energy we derived in the water maser regions is higher than the thermal and kinetic energy, leading to the conclusion that, indeed, magnetic fields probably play an important role in shaping Planetary Nebulae.

Leal-Ferreira, M.; Vlemmings, W.; Kemball, A.; Amiri, N.; Maercker, M.; Ramstedt, S.; Olofsson, G.

2014-04-01

221

The Sun's global magnetic field.  

PubMed

Our present-day understanding of solar and stellar magnetic fields is discussed from both an observational and theoretical viewpoint. To begin with, observations of the Sun's large-scale magnetic field are described, along with recent advances in measuring the spatial distribution of magnetic fields on other stars. Following this, magnetic flux transport models used to simulate photospheric magnetic fields and the wide variety of techniques used to deduce global coronal magnetic fields are considered. The application and comparison of these models to the Sun's open flux, hemispheric pattern of solar filaments and coronal mass ejections are then discussed. Finally, recent developments in the construction of steady-state global magnetohydrodynamic models are considered, along with key areas of future research. PMID:22665897

Mackay, Duncan H

2012-07-13

222

Magnetic response to applied electrostatic field in external magnetic field  

NASA Astrophysics Data System (ADS)

We show, within QED and other possible nonlinear theories, that a static charge localized in a finite domain of space becomes a magnetic dipole, if it is placed in an external (constant and homogeneous) magnetic field in the vacuum. The magnetic moment is quadratic in the charge, depends on its size and is parallel to the external field, provided the charge distribution is at least cylindrically symmetric. This magneto-electric effect is a nonlinear response of the magnetized vacuum to an applied electrostatic field. Referring to the simple example of a spherically symmetric applied field, the nonlinearly induced current and its magnetic field are found explicitly throughout the space; the pattern of the lines of force is depicted, both inside and outside the charge, which resembles that of a standard solenoid of classical magnetostatics.

Adorno, T. C.; Gitman, D. M.; Shabad, A. E.

2014-04-01

223

Theory of an Active Magnetic Regenerative Refrigerator.  

National Technical Information Service (NTIS)

The adiabatic temperature change with field is limited to about 2 K/Tesla for ferromagnets near their Curie temperatures by the change of magnetization with temperature and the lattice heat capacity. Hence, practical magnetic refrigerators operate on a re...

J. A. Barclay

1982-01-01

224

The Extended Coronal Magnetic Field.  

National Technical Information Service (NTIS)

The coronal magnetic field should contain many field lines connecting the photosphere to interplanetary space. A sharp boundary separates two adjacent sectors of opposite polarity. The large-scale structure of the corona is related to the photospheric sec...

J. M. Wilcox

1970-01-01

225

Flares and Changing Magnetic Fields.  

National Technical Information Service (NTIS)

One of the principal objectives of the magnetic field observing program at the Sacramento Peak Observatory has been to discover whether there are any observable changes in the photospheric fields at the time of flares.

D. M. Rust

1972-01-01

226

Feasibility study of Nb3Al Rutherford cable for high field accelerator magnet application  

Microsoft Academic Search

Feasibility study of Cu stabilized NbAl strand and Rutherford cable for the application to high field accelerator magnets are being done at Fermilab in collaboration with NIMS. The NbAl strand, which was developed and manufactured at NIMS in Japan, has a non-copper Jc of about 844 A\\/mm² at 15 Tesla at 4.2 K, a copper content of 50%, and filament

R. Yamada; A. Kikuchi; G. Ambrosio; N. Andreev; E. Barzi; C. Cooper; S. Feher; V. V. Kashikhin; M. Lamm; I. Novitski; T. Takeuchi; M. Tartaglia; D. Turrioni; A. P. Verweij; M. Wake; G Willering; A. V. Zlobin

2006-01-01

227

Feasibility Study of Nb3Al Rutherford Cable for High Field Accelerator Magnet Application  

Microsoft Academic Search

Feasibility study of Cu stabilized Nb3Al strand and Rutherford cable for the application to high field accelerator magnets are being done at Fermilab in collaboration with NIMS. The Nb3Al strand, which was developed and manufactured at NIMS in Japan, has a non-copper Jc of about 844 A\\/mm2 at 15 Tesla at 4.2 K, a copper content of 50%, and filament

R. Yamada; A. Kikuchi; G. Ambrosio; N. Andreev; E. Barzi; C. Cooper; S. Feher; V. V. Kashikin; M. Lamm; I. Novitski; T. Takeuchi; M. Tartaglia; D. Turrioni; A. P. Verweij; M. Wake; G. Willering; A. V. Zlobin

2007-01-01

228

Homopolar generator powered high field magnet experiment for the ignitex fusion device  

Microsoft Academic Search

The design of a scaled down prototype of the IGNITEX (Texas Ignition Experiment) toroidal field (TF) magnet is discussed. The IGNITEX concept is a single-tum tokamak designed to produce and control an ignited plasma with ohmic heating alone[l,2]. The objective of the IGNITEX Technology Demonstrator (ITD) is to design, fabricate and test the operation of a single turn, 20 tesla,

M. D. Werst; G. W. Brunson; M. D. Driga; K. T. Hsieh; R. L. Sledge; W. F. Weldon; H. H. Woodson

1989-01-01

229

High Magnetic Field Optical Studies of Charged Exciton in CdTe 2D Electron Gases  

Microsoft Academic Search

Photoluminescence (PL) and reflectivity spectroscopy in magnetic fields up to 60 Tesla are used to investigate the excitonic optical transitions within CdTe\\/(Cd,Mg)Te 2D electron gases. The samples are 100 A and 200 A wide quantum well (QW) wherein the electron density is varied smoothly from 1 × 1011 to 4.5 × 1011 cm-3 across the wafer. This allows us to

N. Negre; S. A. Crooker; A. Wojs; G. Karczewski

2002-01-01

230

A paramagnetic bonding mechanism for diatomics in strong magnetic fields.  

PubMed

Elementary chemistry distinguishes two kinds of strong bonds between atoms in molecules: the covalent bond, where bonding arises from valence electron pairs shared between neighboring atoms, and the ionic bond, where transfer of electrons from one atom to another leads to Coulombic attraction between the resulting ions. We present a third, distinct bonding mechanism: perpendicular paramagnetic bonding, generated by the stabilization of antibonding orbitals in their perpendicular orientation relative to an external magnetic field. In strong fields such as those present in the atmospheres of white dwarfs (on the order of 10(5) teslas) and other stellar objects, our calculations suggest that this mechanism underlies the strong bonding of H(2) in the (3)?(u)(+)(1?(g)1?(u)*) triplet state and of He(2) in the (1)?(g)(+)(1?(g)(2)1?(u)(*2)) singlet state, as well as their preferred perpendicular orientation in the external field. PMID:22822146

Lange, Kai K; Tellgren, E I; Hoffmann, M R; Helgaker, T

2012-07-20

231

Dresden pulsed magnetic field facility  

NASA Astrophysics Data System (ADS)

We report on the status quo of the Dresden High Magnetic Field Laboratory (HLD) that is being set up at the Forschungszentrum Dresden-Rossendorf in Dresden, Germany. First pulsed-field coils reaching up to 71 T with a pulse duration of about 100 ms have been designed, constructed, and tested. A two-coil 100 T magnet and a long-pulse (1000 ms) 60 T magnet are under construction. Electrical-transport and magnetization experiments are running routinely in the pilot laboratory at the IFW Dresden. The feasibility of NMR experiments in pulsed-field environments has been proven.

Wosnitza, J.; Bianchi, A. D.; Freudenberger, J.; Haase, J.; Herrmannsdörfer, T.; Kozlova, N.; Schultz, L.; Skourski, Y.; Zherlitsyn, S.; Zvyagin, S. A.

2007-03-01

232

Origin of cosmic magnetic fields.  

PubMed

We calculate, in the free Maxwell theory, the renormalized quantum vacuum expectation value of the two-point magnetic correlation function in de Sitter inflation. We find that quantum magnetic fluctuations remain constant during inflation instead of being washed out adiabatically, as usually assumed in the literature. The quantum-to-classical transition of super-Hubble magnetic modes during inflation allow us to treat the magnetic field classically after reheating, when it is coupled to the primeval plasma. The actual magnetic field is scale independent and has an intensity of few×10(-12)??G if the energy scale of inflation is few×10(16)??GeV. Such a field accounts for galactic and galaxy cluster magnetic fields. PMID:23971556

Campanelli, Leonardo

2013-08-01

233

Magnetic field sensor by orthoferrites  

Microsoft Academic Search

Among all ferromagnets orthoferrites possess the highest velocities of domain wall motion. Dynamic properties of a magnetic field meter based on domain wall dynamics in yttrium orthoferrite are reported. It is shown that at low driving magnetic fields and at frequencies up to the MHz band domain wall dynamics can be adequately described by linear equations. In a wide range

Y. S. Didosyan; V. Y. Barash; N. A. Bovarin; H. Hauser; P. Fulmek

1997-01-01

234

THE CLUSTER MAGNETIC FIELD INVESTIGATION  

Microsoft Academic Search

The Cluster mission provides a new opportunity to study plasma processes and structures in the near-Earth plasma environment. Four-point measurements of the magnetic field will enable the analysis of the three dimensional structure and dynamics of a range of phenomena which shape the macroscopic properties of the magnetosphere. Difference measurements of the magnetic field data will be combined to derive

A. Balogh; M. W. Dunlop; S. W. H. Cowley; D. J. Southwood; J. G. Thomlinson; K. H. Glassmeier; G. Musmann; H. Luhr; S. Buchert; M. H. AcuÑA; D. H. Fairfield; J. A. Slavin; W. Riedler; K. Schwingenschuh; M. G. Kivelson

1997-01-01

235

Image distortion and artifacts caused by the use of a titanium aneurism clip in 1.5 tesla- and 3 tesla-magnetic resonance imaging: effect on (60)cobalt stereotactic radiosurgery treatment planning.  

PubMed

In gamma knife stereotactic radiosurgery (GKSRS) treatment planning, 1.5 tesla (T)-magnetic resonance imaging (MRI) is normally used to identify the target lesion. Image artifacts and distortion arise in MRI if a titanium clip is surgically implanted in the brain to treat cerebral aneurysm. 3-T MRI scanners, which are increasingly being adopted, provide imaging of anatomic structures with better clinical usefulness than 1.5-T MRI machines. We investigated signal defects and image distortions both close to and more distant from the titanium clip in 1.5-T and 3-T MRI. Two kinds of phantoms were scanned using 1.5-T and 3-T MRI. Acquisitions with and without the clip were performed under the same scan parameters. No difference was observed between 1.5 T and 3 T in local decrease of signal intensity; however, image distortion was observed at 20 mm from the clip in 3 T. Over the whole region, the distortions caused by the clip were less than 0.3 mm and 1.6 mm under 1.5-T and 3-T MRI, respectively. The geometric accuracy of 1.5-T MRI was better than 3-T MRI and thus better for GKSRS treatment planning. 3-T MRI, however, appears less suitable for use in treatment planning. PMID:24953318

Nakazawa, Hisato; Yamamuro, Osamu; Uchiyama, Yukio; Komori, Masataka

2014-06-01

236

Dresden pulsed magnetic field facility  

Microsoft Academic Search

We report on the status quo of the Dresden High Magnetic Field Laboratory (HLD) that is being set up at the Forschungszentrum Dresden-Rossendorf in Dresden, Germany. First pulsed-field coils reaching up to 71T with a pulse duration of about 100ms have been designed, constructed, and tested. A two-coil 100T magnet and a long-pulse (1000ms) 60T magnet are under construction. Electrical-transport

J. Wosnitza; A. D. Bianchi; J. Freudenberger; J. Haase; T. Herrmannsdörfer; N. Kozlova; L. Schultz; Y. Skourski; S. Zherlitsyn; S. A. Zvyagin

2007-01-01

237

PLACD-7T Study: Atherosclerotic Carotid Plaque Components Correlated with Cerebral Damage at 7 Tesla Magnetic Resonance Imaging  

PubMed Central

Introduction: In patients with carotid artery stenosis histological plaque composition is associated with plaque stability and with presenting symptomatology. Preferentially, plaque vulnerability should be taken into account in pre-operative work-up of patients with severe carotid artery stenosis. However, currently no appropriate and conclusive (non-) invasive technique to differentiate between the high and low risk carotid artery plaque in vivo is available. We propose that 7 Tesla human high resolution MRI scanning will visualize carotid plaque characteristics more precisely and will enable correlation of these specific components with cerebral damage. Study objective: The aim of the PlaCD-7T study is 1: to correlate 7T imaging with carotid plaque histology (gold standard); and 2: to correlate plaque characteristics with cerebral damage ((clinically silent) cerebral (micro) infarcts or bleeds) on 7 Tesla high resolution (HR) MRI. Design: We propose a single center prospective study for either symptomatic or asymptomatic patients with haemodynamic significant (70%) stenosis of at least one of the carotid arteries. The Athero-Express (AE) biobank histological analysis will be derived according to standard protocol. Patients included in the AE and our prospective study will undergo a pre-operative 7 Tesla HR-MRI scan of both the head and neck area. Discussion: We hypothesize that the 7 Tesla MRI scanner will allow early identification of high risk carotid plaques being associated with micro infarcted cerebral areas, and will thus be able to identify patients with a high risk of periprocedural stroke, by identification of surrogate measures of increased cardiovascular risk.

den Hartog, A.G; Bovens, S.M; Koning, W; Hendrikse, J; Pasterkamp, G; Moll, F.L; de Borst, G.J

2011-01-01

238

Superconductivity at High Magnetic Fields  

Microsoft Academic Search

Using pulsed-magnetic-field techniques, we have studied the magnetic-field-induced superconducting transitions of alloys in the systems Ti-V, Ti-Nb, Ti-Ta, Ti-Mo, Zr-Nb, Hf-Nb, Hf-Ta, U-Nb, and U-Mo. For concentrated alloys the low-current-density resistive critical field Hr(J<~10 A\\/cm2) is nearly independent of the amount of cold working and the relative orientations of magnetic field, current, and anisotropic defect structure. The observed values of

T. G. Berlincourt; R. R. Hake

1963-01-01

239

High latitude solar magnetic fields  

NASA Technical Reports Server (NTRS)

Kitt Peak magnetograms are used to measure polar magnetic fields. The polar mean absolute field increases at the same time as the polar mean field decreases. That is, the polar mean absolute field varies in phase with solar activity, in contrast to the out of phase variation of the mean polar field. It is found that the polar fields have a large bipolar component even at solar minimum, with a magnitude equal to that found at low latitudes outside the active latitude bands.

Murray, Norman

1992-01-01

240

A Simulation Study of a Method to Reduce Positron Annihilation Spread Distributions Using a Strong Magnetic Field in Positron Emission Tomography  

Microsoft Academic Search

The positron trajectories have been three-dimensionally simulated using a Monte-Carlo method under various strength of the magnetic field. More than 5 tesla of the field confined the positrons effectively, resulting in increase of the probability of the annihilation within a limited small region, hence the higher spatial resolution in positron emission tomography.

H. Iida; I. Kanno; S. Miura; M. Murakami; K. Takahashi; K. Uemura

1986-01-01

241

PREPROCESSING MAGNETIC FIELDS WITH CHROMOSPHERIC LONGITUDINAL FIELDS  

SciTech Connect

Nonlinear force-free field (NLFFF) extrapolation is a powerful tool for the modeling of the magnetic field in the solar corona. However, since the photospheric magnetic field does not in general satisfy the force-free condition, some kind of processing is required to assimilate data into the model. In this paper, we report the results of new preprocessing for the NLFFF extrapolation. Through this preprocessing, we expect to obtain magnetic field data similar to those in the chromosphere. In our preprocessing, we add a new term concerning chromospheric longitudinal fields into the optimization function proposed by Wiegelmann et al. We perform a parameter survey of six free parameters to find minimum force- and torque-freeness with the simulated-annealing method. Analyzed data are a photospheric vector magnetogram of AR 10953 observed with the Hinode spectropolarimeter and a chromospheric longitudinal magnetogram observed with SOLIS spectropolarimeter. It is found that some preprocessed fields show the smallest force- and torque-freeness and are very similar to the chromospheric longitudinal fields. On the other hand, other preprocessed fields show noisy maps, although the force- and torque-freeness are of the same order. By analyzing preprocessed noisy maps in the wave number space, we found that small and large wave number components balance out on the force-free index. We also discuss our iteration limit of the simulated-annealing method and magnetic structure broadening in the chromosphere.

Yamamoto, Tetsuya T. [Solar-Terrestrial Environment Laboratory, Nagoya University, Chikusa-ku, Nagoya 464-8601 (Japan); Kusano, K., E-mail: tyamamot@stelab.nagoya-u.ac.jp [Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Kanagawa 236-0001 (Japan)

2012-06-20

242

Magnetic field structure evolution in rotating magnetic field plasmas  

SciTech Connect

A study of magnetic field structure evolution during 40-ms plasma discharge has been performed in a new device with 80 cm long/40 cm diameter cylindrical chamber, in which a plasma current I{sub p}{approx_equal}2 kA was driven and sustained by a rotating magnetic field. The main focus of the experiments is on how the changes in externally applied magnetic field affect the current profile and magnetic field in plasma. During plasma discharge, a pulse current was briefly fed to a magnetic coil located at the midplane (middle coil). The magnetic field in cross section of plasma was scanned with pickup probes. Two regimes were studied: without and with an external toroidal field (TF) produced by axial I{sub z} current. With a relatively small current (I{sub m} {<=} 600 A) in the middle coil, the plasma current is boosted up to 5 kA. The magnetic flux surfaces become extended along the axial Z direction, sometimes with the formation of doublet shape plasma. The regime without TF appears to be less stable, presumably due to the reversal of plasma current in central area of plasma column.

Petrov, Yuri; Yang Xiaokang; Huang, T.-S. [Prairie View A and M University, Prairie View, Texas 77446 (United States)

2008-07-15

243

Magnetic field measurements of a superconducting undulator for a Harmonic Generation FEL experiment at the NSLS  

SciTech Connect

An 18mm period, 0.54 Tesla, 8mm gap superconducting undulator with both horizontal and vertical focusing has been built and tested. This magnet, which is fabricated in 25 cm length sections, is being tested for use in the radiator section (total magnet length of 1.5 m) of the Harmonic Generation Free Electron Laser experiment at the National Synchrotron Light Source - Accelerator Test Facility at Brookhaven National Lab., in collaboration with Grumman Corp. The measurement system is outlined, sources and estimates of errors are described, and some magnetic field data are presented and discussed.

Solomon, L.; Ingold, G.; Ben-Zvi, I.; Krinsky, S.; Yu, L.H.; Sampson, W.; Robins, K.

1993-07-01

244

Spinning magnetic fields  

Microsoft Academic Search

A possible electrical charge model based on the spinning time invariant point magnetic dipole within the framework of classical physics is outlined, as suggested by the admissible circular trajectory of a test charge around the magnetic dipole in its equatorial plane. The model depends on the moving force line hypothesis which has been claimed to have been disproved. The controversy

Jovan Djuric

1975-01-01

245

Studies on highly anisotropic conductors and superconductors in high magnetic fields and low temperatures  

SciTech Connect

Transport properties in high magnetic fields and at low temperatures were studied in a number of highly anisotropic organic superconductors and high-{Tc} cuprate superconductors. The magnetothermopower of (TMTSF){sub 2}ClO{sub 4} was systematically studied through the entire range of magnetic-field-induced spin-density-wave (FISDW) transitions. The data provide strong evidence of the collective nature of the extremely stable state between 8 to 25 Tesla resembling the 1/3 fractional quantized Hall effect. A new phase transition into a semiconducting state at 2.6K in a field of 30 Tesla was identified. The FISDW phase diagram in the field range of 15-18 Tesla was studied in detail to sort out the relationship between the fast oscillations (FO) and the reentrant FISDW. The study shows that there are no oscillations in the phase boundary correlated to the FO, in contrast to a theory proposed by Lebed and Bak. Transport properties of the high-{Tc} superconductors were systematically studied. The temperature and carrier concentration dependence of the thermopower suggested that the suprates were strongly correlated systems.

Yu, Rangchen.

1990-01-01

246

Photoluminescence studies of modulation doped coupled double quantum wells in magnetic fields  

SciTech Connect

We have studied the photoluminescence spectra of a series of mudulation doped couple double quantum well structures in parallel and perpendicular magnetic fields to 62 tesla at 4K and 77K, for B{parallel}a, the spectra display distinct Landau level transitions which show anti-crossing with the e1-hh1 exciton. At high fields, the lowest conduction band-valence exciton approaches the extrapolated 0- 0 Landau level. About 25 Tesla, there is valence band mixing of the e1-lh1, e1-hh2, e1-hh1 transitions. The spectral peaks display a diamagnetic shift in low in-plane magnetic fields which become linear in high fields. At magnetic fields beyond 40T, spin splitting is observed for both B{parallel}z and B{perpendicular} geometries. The partial energy gap discovered in conductance measurements in in-plane fields was not conclusively observed using photoluminescence spectroscopy, although anomalies in the energy dependence of the lowest level with magnetic field were evident at similar field values.

Kim, Y.; Perry, C.H. [Northeastern Univ., Boston, MA (United States)]|[Los Alamos National Lab., NM (United States); Simmons, J.A.; Klem, J.F.; Jones, E.D. [Sandia National Labs., Albuquerque, NM (United States); Rickel, D.G. [Los Alamos National Lab., NM (United States)

1996-09-01

247

Comparison Between { {Nb}}_{3}{ {Al}} and { {Nb}}_{3}{ {Sn}} Strands and Cables for High Field Accelerator Magnets  

Microsoft Academic Search

The NbAl small racetrack magnet, SR07, has been successfully built and tested to its short sample limit beyond 10 Tesla without any training. Thus the practical application of NbAl strands for high field accelerator magnets is established. The characteristics of the representative F4 strand and cable, are compared with the typical NbSn strand and cable. It is represented by the

Ryuji Yamada; Akihiro Kikuchi; Emanuela Barzi; Guram Chlachidze; Allen Rusy; Takao Takeuchi; Michael Tartaglia; Daniel Turrioni; Vesselin Velev; Masayoshi Wake; Alexander A. Zlobin

2010-01-01

248

Crystal field and magnetic properties of ErH3  

NASA Technical Reports Server (NTRS)

Magnetization and magnetic susceptibility measurements have been made in the temperature range 1.3 to 4.2 K on powdered samples of ErH3. The susceptibility exhibits Curie-Weiss behavior from 4.2 to 2 K, and intercepts the negative temperature axis at 1.05 + or - 0.05 K, indicating that the material is antiferromagnetic. The low field effective moment is 6.77 + or - 0.27 Bohr magnetons per ion. The magnetization exhibits a temperature independent contribution, the slope of which is (5 + or - 1.2) times 10 to the minus 6 Weber m/kg Tesla. The saturation moment is 3.84 + or - 0.15 Bohr magnetons per ion. The results can be qualitatively explained by the effects of crystal fields on the magnetic ions. No definitive assignment of a crystal field ground state can be given, nor can a clear choice between cubically or hexagonally symmetric crystal fields be made. For hexagonal symmetry, the first excited state is estimated to be 86 to 100 K above the ground state. For cubic symmetry, the splitting is of the order of 160 to 180 K.

Flood, D. J.

1977-01-01

249

Affecting weak light localization by strong magnetic fields  

NASA Astrophysics Data System (ADS)

We report an experimental study of the magneto-optical Faraday effect in strongly multiple scattering media using magnetic fields up to 23 Tesla. Faraday rotation of the polarization of laser light, diffusing through samples consisting of colloidal particles embedded in a Faraday-active glass matrix, is found to destroy coherent backscattering. The angular shape of the coherent backscattering cone varies as a function of the applied field B in agreement with a simple model and with numerical simulations. In particular, the intensity at backscattering is found to decrease with B like the intensity with scattering angle at B = 0, as predicted. The multiple scattering Faraday effect provides a unique experimental way to destroy constructive interferences between time reversed optical scattering paths. It is thus expected to affect light localization and may be used to prove (or disprove) its existence.

Lenke, R.; Maret, G.

1993-01-01

250

Magnetic fields in galaxy clusters  

NASA Astrophysics Data System (ADS)

While it is established that galaxy clusters host magnetic fields of the order of a few ?G, both, their origin as well as their role in the intracluster medium (ICM) remain unclear. I will review the observational evidence for magnetic fields in galaxy clusters and present various lines of research that study the effects of magnetic fields in the ICM. Magnetic fields affect the way in which galaxies interact with the ICM, they may render the ICM buoyantly unstable in the presence of anisotropic thermal conduction, and they affect the thermal structure of the gas in cluster cores. Finally, opportunities for future research in this field, in particular in light of new radio telescopes is highlighted.

Brüggen, M.

2013-06-01

251

Preflare magnetic and velocity fields  

NASA Technical Reports Server (NTRS)

A characterization is given of the preflare magnetic field, using theoretical models of force free fields together with observed field structure to determine the general morphology. Direct observational evidence for sheared magnetic fields is presented. The role of this magnetic shear in the flare process is considered within the context of a MHD model that describes the buildup of magnetic energy, and the concept of a critical value of shear is explored. The related subject of electric currents in the preflare state is discussed next, with emphasis on new insights provided by direct calculations of the vertical electric current density from vector magnetograph data and on the role of these currents in producing preflare brightenings. Results from investigations concerning velocity fields in flaring active regions, describing observations and analyses of preflare ejecta, sheared velocities, and vortical motions near flaring sites are given. This is followed by a critical review of prevalent concepts concerning the association of flux emergence with flares

Hagyard, M. J.; Gaizauskas, V.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.; Karpen, J. T.; Martres, M.-J.; Porter, J. G.; Schmeider, B.

1986-01-01

252

Cryogenics for a 5 Tesla Superconducting Solenoid with Large Aperture at DESY  

SciTech Connect

A large aperture superconducting solenoid-magnet with fields up to 5.25 Tesla is being set up as high field test facility at DESY. It is used to measure prototype time projection chambers foreseen as detectors for a future high energy physics collider experiment. The new cryogenic supply of this magnet within the existing HERA cryogenic helium system is described. The cryogenic control, operation and results are outlined.

Gadwinkel, E.; Lierl, H.; Notz, D.; Schaffran, J.; Schoeneburg, B. [Deutsches Elektronen-Synchrotron, DESY, Hamburg, 22607 (Germany); Herzog, H. [Deutsches Elektronen-Synchrotron, DESY, Hamburg, 22607 (Germany); Linde Kryotechnik A.G., plant operation section at DESY, Pfungen, 8422 (Switzerland)

2004-06-23

253

Magnetic Field Effect Transistors.  

National Technical Information Service (NTIS)

It has been demonstrated that magnetic Cr02 can be selectively deposited on semiconductor substrates and polymide resin plastics with feature resolution smaller than micron. In addition, hard coatings have been fabricated to protect active devices as well...

J. T. Spencer P. A. Dowben

1990-01-01

254

Magnetic Fields in the Sun.  

National Technical Information Service (NTIS)

The observed properties of solar magnetic fields are reviewed, with particular reference to the complexities imposed on the field by motions of the highly conducting gas. Turbulent interactions between gas and field lead to heating or cooling of the gas a...

D. J. Mullan

1974-01-01

255

Measurements of Rayleigh-Taylor-Induced Magnetic Fields in the Linear and Non-linear Regimes  

NASA Astrophysics Data System (ADS)

Magnetic fields are generated in plasmas by the Biermann-battery, or thermoelectric, source driven by non-collinear temperature and density gradients. The ablation front in laser-irradiated targets is susceptible to Rayleigh-Taylor (RT) growth that produces gradients capable of generating magnetic fields. Measurements of these RT-induced magnetic fields in planar foils have been made using a combination of x-ray and monoenergetic-proton radiography techniques. At a perturbation wavelength of 120 ?m, proton radiographs indicate an increase of the magnetic-field strength from ˜1 to ˜10 Tesla during the linear growth phase. A characteristic change in field structure was observed later in time for irradiated foils of different initial surface perturbations. Proton radiographs show a regular cellular configuration initiated at the same time during the drive, independent of the initial foil conditions. This non-linear behavior has been experimentally investigated and the source of these characteristic features will be discussed.

Manuel, Mario

2012-10-01

256

Feasibility study of Nb3Al Rutherford cable for high field accelerator magnet application  

SciTech Connect

Feasibility study of Cu stabilized Nb{sub 3}Al strand and Rutherford cable for the application to high field accelerator magnets are being done at Fermilab in collaboration with NIMS. The Nb{sub 3}Al strand, which was developed and manufactured at NIMS in Japan, has a non-copper Jc of about 844 A/mm{sup 2} at 15 Tesla at 4.2 K, a copper content of 50%, and filament size of about 50 microns. Rutherford cables with 27 Nb{sub 3}Al strands of 1.03 mm diameter were fabricated and tested. Quench tests on a short cable were done to study its stability with only its self field, utilizing a high current transformer. A pair of 2 meter long Nb{sub 3}Al cables was tested extensively at CERN at 4.3 and 1.9 K up to 11 Tesla including its self field with a high transport current of 20.2 kA. In the low field test we observed instability near splices and in the central region. This is related to the flux-jump like behavior, because of excessive amount of Nb in the Nb{sub 3}Al strand. There is possibility that the Nb in Nb{sub 3}Al can cause instability below 2 Tesla field regions. We need further investigation on this problem. Above 8 Tesla, we observed quenches near the critical surface at fast ramp rate from 1000 to 3000 A/sec, with quench velocity over 100 m/sec. A small racetrack magnet was made using a 14 m of Rutherford cable and successfully tested up to 21.8 kA, corresponding to 8.7 T.

Yamada, R.; /Fermilab; Kikuchi, A.; /Tsukuba Magnet Lab.; Ambrosio, G.; Andreev, N.; Barzi, E.; Cooper, C.; Feher, S.; Kashikhin, V.V.; Lamm, M.; Novitski, I.; /Fermilab; Takeuchi, T.; /Tsukuba Magnet Lab.; Tartaglia, M.; Turrioni, D.; /Fermilab; Verweij, A.P.; /CERN; Wake, M.; Willering, G; /Tsukuba Magnet Lab.; Zlobin, A.V.; /Fermilab

2006-08-01

257

The polar heliospheric magnetic field  

NASA Technical Reports Server (NTRS)

It is suggested that the polar heliospheric magnetic field, at large heliocentric distances, may deviate considerably from the generally accepted Archimedean spiral. Instead, it is suggested that the large-scale field near the poles may be dominated by randomly-oriented transverse magnetic fields with magnitude much larger than the average spiral. The average vector field is still the spiral, but the average magnitude may be much larger. In addition, the field direction is transverse to the radial direction most of the time instead of being nearly radial. This magnetic-field structure has important consequences for the transport of cosmic rays. Preliminary model calculations suggest changes in the radial gradient of galactic cosmic rays which may improve agreement with observations.

Jokipii, J. R.; Kota, J.

1989-01-01

258

Theorem on magnet fringe field.  

National Technical Information Service (NTIS)

Transverse particle motion in particle accelerators is governed almost totally by non-solenoidal magnets for which the body magnetic field can be expressed as a series expansion of the normal (b(sub n)) and skew (a(sub n)) multipoles, B(sub y) + iB(sub x)...

J. Wei R. Talman

1995-01-01

259

Majorana Neutrinos and Magnetic Fields.  

National Technical Information Service (NTIS)

It is stressed that if neutrinos are massive they are probably of Majorana type. This implies that their magnetic moment form factor vanishes identically so that the previously discussed phenomenon of spin rotation in a magnetic field would not appear to ...

J. Schechter J. W. F. Valle

1981-01-01

260

Measuring Earth's Magnetic Field Simply.  

ERIC Educational Resources Information Center

Describes a method for measuring the earth's magnetic field using an empty toilet paper tube, copper wire, clear tape, a battery, a linear variable resistor, a small compass, cardboard, a protractor, and an ammeter. (WRM)

Stewart, Gay B.

2000-01-01

261

Neutron in Strong Magnetic Fields  

NASA Astrophysics Data System (ADS)

A relativistic world-line Hamiltonian for strongly interacting 3q systems in a magnetic field is derived from the path integral for the corresponding Green's function. The neutral baryon Hamiltonian in the magnetic field obeys the pseudomomentum conservation and allows a factorization of the c.m. and internal motion. The resulting expression for the baryon mass in the magnetic field is written explicitly with the account of hyperfine, one pion exchange, and one gluon exchange (color Coulomb) interaction. The neutron mass is fast decreasing with the magnetic field, losing 1/2 of its value at eB ˜0.25 GeV2 and is nearly zero at eB ˜0.5 GeV2. Possible physical consequences of the calculated mass trajectory of the neutron, Mn(B), are presented and discussed.

Andreichikov, M. A.; Kerbikov, B. O.; Orlovsky, V. D.; Simonov, Yu. A.

2014-04-01

262

Development of high temperature superconductors for magnetic field applications  

SciTech Connect

The key requirement for magnetic field applications of high temperature superconductor (HTS) materials is to have conductors with high transport critical current density available for magnet builders. After 3 or 4 years of being without any such object, conductor makers have had recent success in producing simple conductor prototypes. These have permitted the construction of simple HTS magnets having self fields exceeding 1 tesla at 4K. Thus the scientific feasibility of making powerful HTS magnets has been demonstrated. Attention to the technological aspects of making HTS conductors for magnets with strong flux pinning and reduced superconducting granularity is now sensible and attractive. However, extrinsic defects such as filament sausaging, cracking, misaligned grains and other perturbation to long range current flow must be controlled at a low level if the benefit of intrinsic improvements to the critical current density is to be maintained in the conductor form. Due to the great complexity of the HTS materials, there is sometimes confusion as to whether a given sample has an intrinsically or extrinsically limited critical current density. Systematic microstructure variation experiments and resistive transition analysis are shown to be particularly helpful in this phase of conductor development.

Larbalestier, D.C.

1991-12-31

263

Development of high temperature superconductors for magnetic field applications  

SciTech Connect

The key requirement for magnetic field applications of high temperature superconductor (HTS) materials is to have conductors with high transport critical current density available for magnet builders. After 3 or 4 years of being without any such object, conductor makers have had recent success in producing simple conductor prototypes. These have permitted the construction of simple HTS magnets having self fields exceeding 1 tesla at 4K. Thus the scientific feasibility of making powerful HTS magnets has been demonstrated. Attention to the technological aspects of making HTS conductors for magnets with strong flux pinning and reduced superconducting granularity is now sensible and attractive. However, extrinsic defects such as filament sausaging, cracking, misaligned grains and other perturbation to long range current flow must be controlled at a low level if the benefit of intrinsic improvements to the critical current density is to be maintained in the conductor form. Due to the great complexity of the HTS materials, there is sometimes confusion as to whether a given sample has an intrinsically or extrinsically limited critical current density. Systematic microstructure variation experiments and resistive transition analysis are shown to be particularly helpful in this phase of conductor development.

Larbalestier, D.C.

1991-01-01

264

Solar magnetic fields and convection  

Microsoft Academic Search

The flux-rope model of solar magnetic fields is developed further by the use of a variety of observational results.(i)It is confirmed that magnetic fields emerging to form active regions are already in the form of helically twisted flux ropes.(ii)A flux rope is not a homogeneous structure but is made up of hundreds or thousands of flux fibres. These are individually

J. H. Piddington

1976-01-01

265

Solar magnetic fields: an introduction  

Microsoft Academic Search

The magnetic field of the Sun is thought to be produced by a dynamo in the solar interior and exhibits its greatest influence\\u000a on the solar plasma in the tenuous outer layers of the solar atmosphere, where it lies at the heart of almost every major\\u000a phenomenon. Most direct observations of the magnetic field are restricted to the solar surface,

S. K. Solanki

266

Spontaneous thermal magnetic field fluctuation  

SciTech Connect

In recent days, the relativistic version of the classic Weibel instability received renewed attention for its potential role as a mechanism to generate cosmic magnetic fields. However, one of the key conceptual foundations in association with the Weibel instability has not been addressed in the literature. Namely, the spontaneous emission of magnetic field fluctuation, which is supposed to provide the seed perturbation for the Weibel instability, has not been adequately discussed. The present Brief Communication addresses this issue.

Yoon, Peter H. [Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States)

2007-06-15

267

Theorem on magnet fringe field  

SciTech Connect

Transverse particle motion in particle accelerators is governed almost totally by non-solenoidal magnets for which the body magnetic field can be expressed as a series expansion of the normal (b{sub n}) and skew (a{sub n}) multipoles, B{sub y} + iB{sub x} = {summation}(b{sub n} + ia{sub n})(x + iy){sup n}, where x, y, and z denote horizontal, vertical, and longitudinal (along the magnet) coordinates. Since the magnet length L is necessarily finite, deflections are actually proportional to ``field integrals`` such as {bar B}L {equivalent_to} {integral} B(x,y,z)dz where the integration range starts well before the magnet and ends well after it. For {bar a}{sub n}, {bar b}{sub n}, {bar B}{sub x}, and {bar B}{sub y} defined this way, the same expansion Eq. 1 is valid and the ``standard`` approximation is to neglect any deflections not described by this expansion, in spite of the fact that Maxwell`s equations demand the presence of longitudinal field components at the magnet ends. The purpose of this note is to provide a semi-quantitative estimate of the importance of {vert_bar}{Delta}p{sub {proportional_to}}{vert_bar}, the transverse deflection produced by the ion-gitudinal component of the fringe field at one magnet end relative to {vert_bar}{Delta}p{sub 0}{vert_bar}, the total deflection produced by passage through the whole magnet. To emphasize the generality and simplicity of the result it is given in the form of a theorem. The essence of the proof is an evaluation of the contribution of the longitudinal field B{sub x} from the vicinity of one magnet end since, along a path parallel to the magnet axis such as path BC.

Wei, Jie [Brookhaven National Lab., Upton, NY (United States); Talman, R. [Cornell Univ., Ithaca, NY (United States). Lab. of Nuclear Studies

1995-12-31

268

Optical sensor of magnetic fields  

DOEpatents

An optical magnetic field strength sensor for measuring the field strength of a magnetic field comprising a dilute magnetic semi-conductor probe having first and second ends, longitudinally positioned in the magnetic field for providing Faraday polarization rotation of light passing therethrough relative to the strength of the magnetic field. Light provided by a remote light source is propagated through an optical fiber coupler and a single optical fiber strand between the probe and the light source for providing a light path therebetween. A polarizer and an apparatus for rotating the polarization of the light is provided in the light path and a reflector is carried by the second end of the probe for reflecting the light back through the probe and thence through the polarizer to the optical coupler. A photo detector apparatus is operably connected to the optical coupler for detecting and measuring the intensity of the reflected light and comparing same to the light source intensity whereby the magnetic field strength may be calculated.

Butler, M.A.; Martin, S.J.

1986-03-25

269

Chiral transition with magnetic fields  

NASA Astrophysics Data System (ADS)

We study the nature of the chiral transition for an effective theory with spontaneous breaking of symmetry, where charged bosons and fermions are subject to the effects of a constant external magnetic field. The problem is studied in terms of the relative intensity of the magnetic field with respect to the mass and the temperature. When the former is the smallest of the scales, we present a suitable method to obtain magnetic and thermal corrections up to ring order at high temperature. By these means, we solve the problem of the instability in the boson sector for these theories, where the squared masses—taken as functions of the order parameter—can vanish and even become negative. The solution is found by considering the screening properties of the plasma, encoded in the resummation of the ring diagrams at high temperature. We also study the case where the magnetic field is the intermediate of the three scales and explore the nature of the chiral transition as we vary the field strength, the coupling constants, and the number of fermions. We show that the critical temperature for the restoration of chiral symmetry monotonically increases from small to intermediate values of the magnetic field and that this temperature is always above the critical temperature for the case when the magnetic field is absent.

Ayala, Alejandro; Hernández, Luis Alberto; Mizher, Ana Júlia; Rojas, Juan Cristóbal; Villavicencio, Cristián

2014-06-01

270

MAXIMUM EFFICIENCY RF SHIMMING: THEORY AND INITIAL APPLICATION FOR HIP IMAGING AT 7 TESLA  

PubMed Central

Radiofrequency shimming with multiple channel excitation has been proposed to increase the transverse magnetic field uniformity and reduce specific absorption rate at high magnetic field strengths (? 7 Tesla) where high-frequency effects can make traditional single channel volume coils unsuitable for transmission. In the case of deep anatomic regions and power-demanding pulse sequences, optimization of transmit efficiency may be a more critical requirement than homogeneity per se. This work introduces a novel method to maximize transmit efficiency using multiple channel excitation and radiofrequency shimming. Shimming weights are calculated in order to obtain the lowest possible net radiofrequency power deposition into the subject for a given transverse magnetic field strength. The method was demonstrated in imaging studies of articular cartilage of the hip joint at 7 Tesla. We show that the new radiofrequency shimming method can enable reduction in power deposition while maintaining an average flip angle or adiabatic condition in the hip cartilage. Building upon the improved shimming, we further show the signal-to-noise ratio in hip cartilage at 7 Tesla can be substantially greater than that at 3 Tesla, illustrating the potential benefits of high field hip imaging.

Deniz, Cem Murat; Brown, Ryan; Lattanzi, Riccardo; Alon, Leeor; Sodickson, Daniel K.; Zhu, Yudong

2012-01-01

271

Post-mortem magnetic resonance microscopy (MRM) of the murine brain at 7 Tesla results in a gain of resolution as compared to in vivo MRM  

PubMed Central

Small-animal MRI with high field strength allows imaging of the living animal. However, spatial resolution in in vivo brain imaging is limited by the scanning time. Measurements of fixated mouse brains allow longer measurement time, but fixation procedures are time consuming, since the process of fixation may take several weeks. We here present a quick and simple post-mortem approach without fixation that allows high-resolution MRI even at 7 Tesla (T2-weighted MRI). This method was compared to in vivo scans with optimized spatial resolution for the investigation of anesthetized mice (T1-weighted MRI) as well as to ex situ scans of fixed brains (T1- and T2-weighted scans) by using standard MRI-sequences, along with anatomic descriptions of areas observable in the MRI, analysis of tissue shrinkage and post-processing procedures (intensity inhomogeneity correction, PCNN3D brain extract, SPMMouse segmentation, and volumetric measurement). Post-mortem imaging quality was sufficient to determine small brain substructures on the morphological level, provided fast possibilities for volumetric acquisition and for automatized processing without manual correction. Moreover, since no fixation was used, tissue shrinkage due to fixation does not occur as it is, e.g., the case by using ex vivo brains that have been kept in fixatives for several days. Thus, the introduced method is well suited for comparative investigations, since it allows determining small structural alterations in the murine brain at a reasonable high resolution even by MRI performed at 7 Tesla.

von Bohlen und Halbach, Oliver; Lotze, Martin; Pfannmoller, Jorg P.

2014-01-01

272

Nonequilibrium nuclear polarization and induced hyperfine and dipolar magnetic fields in semiconductor nanostructures  

NASA Astrophysics Data System (ADS)

We investigate the dynamic nuclear polarization (DNP) caused by hyperfine coupling between nonequilibrium electronic spins and nuclear spins in semiconductor nanostructures. We derive the time and position dependence of the resulting hyperfine and dipolar magnetic fields. In GaAs quantum wells the induced nuclear spin polarization greatly exceeds the polarization of the electronic system that causes the DNP. The induced magnetic fields vary between tens of tesla for the electronic hyperfine field acting on nuclei, to hundreds of gauss for the nuclear hyperfine field acting on electrons, to a few gauss for the induced nuclear dipolar fields that act on both nuclei and electrons. The field strengths should be measurable via optically induced nuclear magnetic resonance or time-resolved Faraday rotation experiments. We discuss the implications of our calculations for low-dimensional semiconductor nanostructures.

?ifrea, Ionel; Flatté, Michael E.

2011-10-01

273

Safety Implications of High-Field MRI: Actuation of Endogenous Magnetic Iron Oxides in the Human Body  

Microsoft Academic Search

BackgroundMagnetic Resonance Imaging scanners have become ubiquitous in hospitals and high-field systems (greater than 3 Tesla) are becoming increasingly common. In light of recent European Union moves to limit high-field exposure for those working with MRI scanners, we have evaluated the potential for detrimental cellular effects via nanomagnetic actuation of endogenous iron oxides in the body.MethodologyTheoretical models and experimental data

Jon Dobson; Richard Bowtell; Ana Garcia-Prieto; Quentin Pankhurst; Igor Sokolov

2009-01-01

274

Magnetic field analysis and optimal design of magnetic bearing  

Microsoft Academic Search

Magnetic field distribution of a radial magnetic bearing with sixteen-pole was analyzed by using finite element method. It was verified by magnetic field measurement. Magnetic bearing structure was optimized based on finite element analysis (FEA) and magnetic circuit method. Optimization was done in object of maximum magnetic force. Two optimizations had similar results. Analysis showed that FEA-based optimization is more

Han Wu; Chunguang Xu; Dingguo Xiao; Juan Hao

2009-01-01

275

Neutron Scattering at Highest Magnetic Fields at the Helmholtz Centre Berlin  

NASA Astrophysics Data System (ADS)

The Helmholtz Centre Berlin (HZB), formerly Hahn-Meitner Institute is a user facility for the study of structure and dynamics with neutrons and synchrotron radiation with special emphasis on experiments under extreme conditions. Neutron scattering is uniquely suited to study magnetic properties on a microscopic length scale, because neutrons have comparable wavelengths and, due to their magnetic moment, they interact with the atomic magnetic moments. At HZB a dedicated instrument for neutron scattering at extreme fields is under construction, the Extreme Environment Diffractometer ExED. It is projected according to the “time-of-flight” principle for elastic and inelastic neutron scattering and for the special geometric constraints of analysing samples in a high field magnet. The new magnet will not only allow for novel experiments, it will be at the forefront of development in magnet technology itself. The design of the magnet will follow the Series Connected Hybrid System Technology (SCH) developed at the National High Magnetic Field Laboratory (NHMFL) in Tallahassee, Florida. To compromise between the needs of the magnet design for highest fields and the concept of the neutron instrument, the magnetic field will be generated by means of a coned solenoid with horizontal field orientation. By using resistive insert coils, which are mounted in the room temperature bore of a superconducting cable-in-conduit (CIC) magnet, fields above 30 Tesla can be obtained in a geometry optimised for the demands of neutron scattering.

Smeibidl, P.; Tennant, A.; Ehmler, H.; Bird, M.

2010-04-01

276

Magnetic fields in quiescent prominences  

SciTech Connect

The origin of the axial fields in high-latitude quiescent prominences is considered. The fact that almost all quiescent prominences obey the same hemisphere-dependent rule strongly suggests that the solar differential rotation plays an important role in producing the axial fields. However, the observations are inconsistent with the hypothesis that the axial fields are produced by differential rotation acting on an existing coronal magnetic field. Several possible explanations for this discrepancy are considered. The possibility that the sign of the axial field depends on the topology of the magnetic field in which the prominence is embedded is examined, as is the possibility that the neutral line is tilted with respect to the east-west direction, so that differential rotation causes the neutral line also to rotate with time. The possibility that the axial fields of quiescent prominences have their origin below the solar surface is also considered. 29 refs.

Van Ballegooijen, A.A.; Martens, P.C.H. (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (USA))

1990-09-01

277

Magnetic-field-induced dose effects in MR-guided radiotherapy systems: dependence on the magnetic field strength  

NASA Astrophysics Data System (ADS)

Several institutes are currently working on the development of a radiotherapy treatment system with online MR imaging (MRI) modality. The main difference between their designs is the magnetic field strength of the MRI system. While we have chosen a 1.5 Tesla (T) magnetic field strength, the Cross Cancer Institute in Edmonton will be using a 0.2 T MRI scanner and the company Viewray aims to use 0.3 T. The magnetic field strength will affect the severity of magnetic field dose effects, such as the electron return effect (ERE): considerable dose increase at tissue air boundaries due to returning electrons. This paper has investigated how the ERE dose increase depends on the magnetic field strength. Therefore, four situations where the ERE occurs have been simulated: ERE at the distal side of the beam, the lateral ERE, ERE in cylindrical air cavities and ERE in the lungs. The magnetic field comparison values were 0.2, 0.75, 1.5 and 3 T. Results show that, in general, magnetic field dose effects are reduced at lower magnetic field strengths. At the distal side, the ERE dose increase is largest for B = 0.75 T and depends on the irradiation field size for B = 0.2 T. The lateral ERE is strongest for B = 3 T but shows no effect for B = 0.2 T. Around cylindrical air cavities, dose inhomogeneities disappear if the radius of the cavity becomes small relative to the in-air radius of the secondary electron trajectories. At larger cavities (r > 1 cm), dose inhomogeneities exist for all magnetic field strengths. In water-lung-water phantoms, the ERE dose increase takes place at the water-lung transition and the dose decreases at the lung-water transition, but these effects are minimal for B = 0.2 T. These results will contribute to evaluating the trade-off between magnetic field dose effects and image quality of MR-guided radiotherapy systems.

Raaijmakers, A. J. E.; Raaymakers, B. W.; Lagendijk, J. J. W.

2008-02-01

278

Edison vs. Tesla  

SciTech Connect

As Edison vs. Tesla week heats up at the Energy Department, we are exploring the rivalry between Thomas Edison and Nikola Tesla and how their work is still impacting the way we use energy today. Whether you're on Team Tesla or Team Edison, both inventors were key players in creating things like batteries, power plants and wireless technologies -- all innovations we still use today. And as we move toward a clean energy future, energy efficient lighting, like LED bulbs, and more efficient electric motors not only help us save money on electricity costs but help combat climate change. For this, Tesla and Edison both deserve our recognition.

Hogan, Kathleen; Wallace, Hal; Ivestor, Rob

2013-11-20

279

Edison vs. Tesla  

ScienceCinema

As Edison vs. Tesla week heats up at the Energy Department, we are exploring the rivalry between Thomas Edison and Nikola Tesla and how their work is still impacting the way we use energy today. Whether you're on Team Tesla or Team Edison, both inventors were key players in creating things like batteries, power plants and wireless technologies -- all innovations we still use today. And as we move toward a clean energy future, energy efficient lighting, like LED bulbs, and more efficient electric motors not only help us save money on electricity costs but help combat climate change. For this, Tesla and Edison both deserve our recognition.

Hogan, Kathleen; Wallace, Hal; Ivestor, Rob

2014-01-07

280

MAGNETIC FIELD MEASUREMENTS FOR FAST-CHANGING MAGNETIC FIELDS.  

SciTech Connect

Several recent applications for fast ramped magnets have been found that require rapid measurement of the field quality during the ramp. (In one instance, accelerator dipoles will be ramped at 1 T/sec, with measurements needed to the accuracy typically required for accelerators.) We have built and tested a new type of magnetic field measuring system to meet this need. The system consists of 16 stationary pickup windings mounted on a cylinder. The signals induced in the windings in a changing magnetic field are sampled and analyzed to obtain the field harmonics. To minimize costs, printed circuit boards were used for the pickup windings and a combination of amplifiers and ADPs used for the voltage readout system. New software was developed for the analysis. Magnetic field measurements of a model dipole developed for the SIS200 accelerator at GSI are presented. The measurements are needed to insure that eddy currents induced by the fast ramps do not impact the field quality needed for successful accelerator operation.

JAIN, A.; ESCALLIER, J.; GANETIS, G.; LOUIE, W.; MARONE, A.; THOMAS. R.; WANDERER, P.

2004-10-03

281

Investigation of Spin Polarized Atomic Hydrogen in Very High Magnetic Fields.  

NASA Astrophysics Data System (ADS)

This thesis details my research on three-body recombination in spin-polarized atomic hydrogen (H downarrow) in very high magnetic fields. One goal of this research was to see if recombination could be suppressed enough to allow observation of Bose-Einstein condensation (BEC). This work has extended Hdownarrow research into a new regime of magnetic field strength by making use of the facilities at the Francis Bitter National Magnet Laboratory. Presented here are the first observations of Hdownarrow in fields up to 20 tesla. Recombination is still not sufficiently suppressed to allow observation of BEC. Analysis of the data for B = 10-20 T reveals interesting qualitative features in the three-body scattering processes never before observed. In contrast to the picture which was emerging from previous studies up to about 10 tesla, this new data suggests that the existing theories are indeed capable of describing the decay of the system in the very high field limit. Based on the newly emerging picture, the possibility of achieving BEC at even higher magnetic fields is discussed.

Gillaspy, John Dale

282

Investigation of spin-polarized atomic hydrogen in very high magnetic fields  

SciTech Connect

This thesis details my research on three-body recombination in spin-polarized atomic hydrogen (H{down arrow}) in very high magnetic fields. One goal of this research as to see if recombination could be suppressed enough to allow observation of Bose-Einstein condensation (BEC). This work has extended H{down arrow} research into a new regime of magnetic field strength by making use of the facilities at the Francis Bitter National Magnet Laboratory. Presented here are the first observations of H{down arrow} in fields up to 20 tesla. Recombination is still no sufficiently suppressed to allow observation of BEC. Analysis of the data for B = 10-20 T reveals interesting qualitative features in the three-body scattering processes never before observed. In contrast to the picture which was emerging from previous studies up to about 10 tesla, the new data suggests that the existing theories are indeed capable of describing the decay of the system in the very high field limit. Based on the newly emerging picture, the possibility of achieving BEC at even higher magnetic fields is discussed.

Gillaspy, J.D.

1988-01-01

283

Magnetic fields in neutron stars  

NASA Astrophysics Data System (ADS)

This work aims at studying how magnetic fields affect the observational properties and the long-term evolution of isolated neutron stars, which are the strongest magnets in the universe. The extreme physical conditions met inside these astronomical sources complicate their theoretical study, but, thanks to the increasing wealth of radio and X-ray data, great advances have been made over the last years. A neutron star is surrounded by magnetized plasma, the so-called magnetosphere. Modeling its global configuration is important to understand the observational properties of the most magnetized neutron stars, magnetars. On the other hand, magnetic fields in the interior are thought to evolve on long time-scales, from thousands to millions of years. The magnetic evolution is coupled to the thermal one, which has been the subject of study in the last decades. An important part of this thesis presents the state-of-the-art of the magneto-thermal evolution models of neutron stars during the first million of years, studied by means of detailed simulations. The numerical code here described is the first one to consistently consider the coupling of magnetic field and temperature, with the inclusion of both the Ohmic dissipation and the Hall drift in the crust.

Viganò, Daniele

2013-09-01

284

Circular swimming in mice after exposure to a high magnetic field  

PubMed Central

There is increasing evidence that exposure to high magnetic fields of 4 tesla and above perturbs the vestibular system of rodents and humans. Performance in a swim test is a sensitive test of vestibular function. In order to determine the effect of magnet field exposure on swimming in mice, mice were exposed for 30-min within a 14.1 tesla superconducting magnet and then tested at different times after exposure in a 2-min swim test. As previously observed in open field tests, mice swam in tight counter-clockwise circles when tested immediately after magnet exposure. The counter-clockwise orientation persisted throughout the 2-min swim test. The tendency to circle was transient, because no significant circling was observed when mice were tested at 3 min or later after magnet exposure. However, mice did show a decrease in total distance swum when tested between 3 and 40 min after magnet exposure. The decrease in swimming distance was accompanied by a pronounced postural change involving a counter-clockwise twist of the pelvis and hindlimbs that was particularly severe in the first 15 s of the swim test. Finally, no persistent difference from sham-exposed mice was seen in the swimming of magnet-exposed mice when tested 60 min, 24 h, or 96 h after magnet exposure. This suggests that there is no long-lasting effect of magnet exposure on the ability of mice to orient or swim. The transient deficits in swimming and posture seen shortly after magnet exposure are consistent with an acute perturbation of the vestibular system by the high magnetic field.

Houpt, Thomas A.; Houpt, Charles E.

2010-01-01

285

Alternating magnetic field assisted magnetization reversal in ferromagnetic antidot  

NASA Astrophysics Data System (ADS)

Although the effects of high-frequency electromagnetic waves on magnetization reversal have been extensively studied, the influence of a low-frequency ac field on magnetization reversal has seldom been examined. In this study, we measured the magnetoresistance and examined the magnetic switching process of Permalloy antidot thin films under an alternating magnetic field with a frequency of 25 kHz. When no alternating magnetic field was present, the transitional field of the antidot thin films decreased as the angle of the direct magnetic field increased. When an alternating magnetic field was present, the transitional field exhibited the same trend. We compared the magnetization process of the antidot thin films with and without the alternating magnetic field and determined that the alternating field can facilitate the transition of magnetization, specifically, by lowering the transitional field with the highest variation rate (33.73%).

Huang, Hao-Ting; Ger, Tzong-Rong; Huang, Chen-Yu; Liao, Kuei-Tien; Wang, Pei-Jen; Lai, Jun-Yang; Chen, Jiann-Yeu; Lai, Mei-Feng

2014-05-01

286

Sensor and method for indicating the presence of a low magnetic field using high critical temperature superconductor ceramic material to absorb electromagnetic energy  

Microsoft Academic Search

This patent describes a sensor for use with a source of electromagnetic energy for indicating the presence of a low magnetic field with a sensitivity of at least 10{sup - 10} tesla. It comprises: a sensing element consisting essentially of a high critical temperature superconductor ceramic oxide material without the need for further processing, said critical temperature being above 77°;

Tyagi

1990-01-01

287

Acoustic cardiac triggering: a practical solution for synchronization and gating of cardiovascular magnetic resonance at 7 Tesla  

PubMed Central

Background To demonstrate the applicability of acoustic cardiac triggering (ACT) for imaging of the heart at ultrahigh magnetic fields (7.0 T) by comparing phonocardiogram, conventional vector electrocardiogram (ECG) and traditional pulse oximetry (POX) triggered 2D CINE acquisitions together with (i) a qualitative image quality analysis, (ii) an assessment of the left ventricular function parameter and (iii) an examination of trigger reliability and trigger detection variance derived from the signal waveforms. Results ECG was susceptible to severe distortions at 7.0 T. POX and ACT provided waveforms free of interferences from electromagnetic fields or from magneto-hydrodynamic effects. Frequent R-wave mis-registration occurred in ECG-triggered acquisitions with a failure rate of up to 30% resulting in cardiac motion induced artifacts. ACT and POX triggering produced images free of cardiac motion artefacts. ECG showed a severe jitter in the R-wave detection. POX also showed a trigger jitter of approximately ?t = 72 ms which is equivalent to two cardiac phases. ACT showed a jitter of approximately ?t = 5 ms only. ECG waveforms revealed a standard deviation for the cardiac trigger offset larger than that observed for ACT or POX waveforms. Image quality assessment showed that ACT substantially improved image quality as compared to ECG (image quality score at end-diastole: ECG = 1.7 ± 0.5, ACT = 2.4 ± 0.5, p = 0.04) while the comparison between ECG vs. POX gated acquisitions showed no significant differences in image quality (image quality score: ECG = 1.7 ± 0.5, POX = 2.0 ± 0.5, p = 0.34). Conclusions The applicability of acoustic triggering for cardiac CINE imaging at 7.0 T was demonstrated. ACT's trigger reliability and fidelity are superior to that of ECG and POX. ACT promises to be beneficial for cardiovascular magnetic resonance at ultra-high field strengths including 7.0 T.

2010-01-01

288

High-magnetic-field-tuned insulating state in single-crystal BaIrO3  

NASA Astrophysics Data System (ADS)

BaIrO3 is a novel magnetic insulator associated with the spin-orbit interaction. It magnetically orders at TC=182 K, with an extremely small saturation moment MS< 0.03 ?B/Ir. Application of high magnetic field up to 35 Tesla results in an exotic behavior characterized by: (1) a drastic rise in electrical resistivity by 250% at low temperatures and (2) highly anisotropic magnetoresistivity with unusually strong hysteretic behavior. Our first principle calculations suggest a band structure near Fermi surface extremely sensitive to slight changes in lattice parameters, which captures underlying physical properties observed experimentally. The giant positive magnetoresistivity along with the extremely small saturation moment signals a delicate interplay between the structural and the electronic degrees of freedom in this compound. The electrical transport and magnetic properties in high magnetic field will be presented and discussed.

Korneta, O. B.; Qi, T. F.; Li, L.; Butrouna, K.; Cao, G.; Choi, E. S.; Wan, Xiangang

2013-03-01

289

High-field magnets and high-field superconductors  

Microsoft Academic Search

This paper gives a brief historical review of the development of high magnetic fields and high field superconductors including brief summaries of the early developments of high magnetic fields and the Francis Bitter National Magnet Laboratory (FBNML). The start of the first revolution (when large critical currents in Nb3Sn were observed in high magnetic fields) and the development of practical

Simon Foner; Francis Bitter

1995-01-01

290

Magnetic Fields in Irregular Galaxies: NGC 4214  

Microsoft Academic Search

Magnetic fields are an important component of the interstellar medium of galaxies. They provide support, transfer energy from supernovae, provide a possible heating mechanism, and channel gas flows (Beck 2004). Despite the importance of magnetic fields in the ISM, it is not well known what generates and sustains galactic magnetic fields or how magnetic fields, gas, and stars interact in

Amanda A. Kepley; E. M. Wilcots; T. Robishaw; C. Heiles; E. Zweibel

2006-01-01

291

Solar magnetic fields - The Italian contribution  

Microsoft Academic Search

A short account is given of the methods of observation, the characteristics of solar magnetic fields, the relationships between velocity and magnetic fields, the theoretical approaches, and the possibilities opened by studies of stellar activity of the solar type. In discussing the classification and characteristics of solar magnetic fields, attention is given to normal bipolar regions, large-scale unipolar magnetic fields,

D. Fabbri; G. Godoli; F. Mazzucconi

1982-01-01

292

Progress in Solar Magnetic Field Extrapolation  

Microsoft Academic Search

Solar magnetic field is the predominant factor of the solar activities. Precise measurements of solar magnetic fields so far are still confined to the thin layer of the solar photosphere. In order to understand the nature of the coronal magnetic fields, it becomes necessary to extrapolate the coronal magnetic fields based on theoretical models using observed photospheric magnetograms as boundary

Juan Hao; Mei Zhang

2007-01-01

293

Satellite to study earth's magnetic field  

NASA Technical Reports Server (NTRS)

The Magnetic Field Satellite (Magsat) designed to measure the near earth magnetic field and crustal anomalies is briefly described. A scalar magnetometer to measure the magnitude of the earth's crustal magnetic field and a vector magnetometer to measure magnetic field direction as well as magnitude are included. The mission and its objectives are summarized along with the data collection and processing system.

1979-01-01

294

Observations of Mercury's magnetic field  

NASA Technical Reports Server (NTRS)

Magnetic field data obtained by Mariner 10 during the third and final encounter with the planet Mercury on 16 March 1975 were studied. A well developed bow shock and modest magnetosphere, previously observed at first encounter on 29 March 1974, were again observed. In addition, a much stronger magnetic field near closest approach, 400 gamma versus 98 gamma, was observed at an altitude of 327 km and approximately 70 deg north Mercurian latitude. Spherical harmonic analysis of the data provide an estimate of the centered planetary magnetic dipole of 4.7 x 10 to the 22nd power Gauss/cu cm with the axis tilted 12 deg to the rotation axis and in the same sense as Earth's. The interplanetary field was sufficiently different between first and third encounters that in addition to the very large field magnitude observed, it argues strongly against a complex induction process generating the observed planetary field. While a possibility exists that Mercury possesses a remanent field due to magnetization early in its formation, a present day active dynamo seems to be a more likely candidate for its origin.

Ness, N. F.; Behannon, K. W.; Lepping, R. P.; Whang, Y. C.

1975-01-01

295

Deflections in magnet fringe fields.  

PubMed

A transverse multipole expansion is derived, including the longitudinal components necessarily present in regions of varying magnetic field profile. It can be used for exact numerical orbit following through the fringe-field regions of magnets whose end designs introduce no extraneous components, i.e., fields not required to be present by Maxwell's equations. Analytic evaluations of the deflections are obtained in various approximations. Mainly emphasized is a "straight-line approximation," in which particle orbits are treated as straight lines through the fringe-field regions. This approximation leads to a readily-evaluated figure of merit, the ratio of rms end deflection to nominal body deflection, that can be used to determine whether or not a fringe field can be neglected. Deflections in "critical" cases (e.g., near intersection regions) are analyzed in the same approximation. PMID:12786502

Papaphilippou, Y; Wei, J; Talman, R

2003-04-01

296

SOLID STATE TESLA COIL  

Microsoft Academic Search

Some years ago I developed an interest in Tesla coils. I was teaching a senior elective course at Kansas State University where we talked about power MOSFETs and topics related to high voltages and currents. I decided to use a Tesla coil as a class project. We would talk about design aspects, then design, build, and test a coil. The

Gary L. Johnson

2001-01-01

297

Tesla and AND gates  

Microsoft Academic Search

This column takes a closer look at the work of Nikola Tesla, a brilliant engineer and scientist who made incredible contributions in many diverse areas, such as radar and radio. Tesla was the first person to be awarded a patent on an AND gate.

Mel Breuer

2007-01-01

298

Non-Enhanced MR Imaging of Cerebral Aneurysms: 7 Tesla versus 1.5 Tesla  

PubMed Central

Purpose To prospectively evaluate 7 Tesla time-of-flight (TOF) magnetic resonance angiography (MRA) in comparison to 1.5 Tesla TOF MRA and 7 Tesla non-contrast enhanced magnetization-prepared rapid acquisition gradient-echo (MPRAGE) for delineation of unruptured intracranial aneurysms (UIA). Material and Methods Sixteen neurosurgical patients (male n?=?5, female n?=?11) with single or multiple UIA were enrolled in this trial. All patients were accordingly examined at 7 Tesla and 1.5 Tesla MRI utilizing dedicated head coils. The following sequences were obtained: 7 Tesla TOF MRA, 1.5 Tesla TOF MRA and 7 Tesla non-contrast enhanced MPRAGE. Image analysis was performed by two radiologists with regard to delineation of aneurysm features (dome, neck, parent vessel), presence of artifacts, vessel-tissue-contrast and overall image quality. Interobserver accordance and intermethod comparisons were calculated by kappa coefficient and Lin's concordance correlation coefficient. Results A total of 20 intracranial aneurysms were detected in 16 patients, with two patients showing multiple aneurysms (n?=?2, n?=?4). Out of 20 intracranial aneurysms, 14 aneurysms were located in the anterior circulation and 6 aneurysms in the posterior circulation. 7 Tesla MPRAGE imaging was superior over 1.5 and 7 Tesla TOF MRA in the assessment of all considered aneurysm and image quality features (e.g. image quality: mean MPRAGE7T: 5.0; mean TOF7T: 4.3; mean TOF1.5T: 4.3). Ratings for 7 Tesla TOF MRA were equal or higher over 1.5 Tesla TOF MRA for all assessed features except for artifact delineation (mean TOF7T: 4.3; mean TOF1.5T 4.4). Interobserver accordance was good to excellent for most ratings. Conclusion 7 Tesla MPRAGE imaging demonstrated its superiority in the detection and assessment of UIA as well as overall imaging features, offering excellent interobserver accordance and highest scores for all ratings. Hence, it may bear the potential to serve as a high-quality diagnostic tool for pretherapeutic assessment and follow-up of untreated UIA.

Wrede, Karsten H.; Dammann, Philipp; Monninghoff, Christoph; Johst, Soren; Maderwald, Stefan; Sandalcioglu, I. Erol; Muller, Oliver; Ozkan, Neriman; Ladd, Mark E.; Forsting, Michael; Schlamann, Marc U.; Sure, Ulrich; Umutlu, Lale

2014-01-01

299

Progress toward 10 tesla accelerator dipoles  

SciTech Connect

A 9.1 T central field has been achieved in a Nb-Ti dipole operating in pressurized helium II at 1.8 K. Three different Nb-Ti dipoles, without iron yokes, have achieved central fields of 8.0, 8.6, and 9.1 T - all short sample performance for the conductors at 1.8 K. In helium I, at 4.3 K, the maximum central fields are from 1.5 to 2.0 T lower. Ten-tesla magnets have been designed for both Nb-Ti operating at 1.8 K and Nb/sub 3/Sn operating at 4.2 K. They are based on a very small beam aperture, (40 to 45 mm), very high current density in the superconductors (over 1000 A/mm/sup 2/), and a very low ratio of stabilizing copper to superconductor (about 1). Both layer and block designs have been developed that utilize Rutherford Cable. Magnet cycling from 0 to 6 T has been carried out for field change rate up to 1 T/s; the cyclic heating at 1 T/s is 36 W per meter. At a more representative rate of 0.2 T/s the heating rate is only 2 W/m. Progress in the program to use Nb/sub 3/Sn and NbTi superconductor, in 10 T accelerator magnets is also discussed.

Hassenzahl, W.; Gilbert, G.; Taylor, C.; Meuser, R.

1983-08-01

300

Magnetic field tomography, helical magnetic fields and Faraday depolarization  

NASA Astrophysics Data System (ADS)

Wide-band radio polarization observations offer the possibility to recover information about the magnetic fields in synchrotron sources, such as details of their three-dimensional configuration, that has previously been inaccessible. The key physical process involved is the Faraday rotation of the polarized emission in the source (and elsewhere along the wave's propagation path to the observer). In order to proceed, reliable methods are required for inverting the signals observed in wavelength space into useful data in Faraday space, with robust estimates of their uncertainty. In this paper, we examine how variations of the intrinsic angle of polarized emission ?0 with the Faraday depth ? within a source affect the observable quantities. Using simple models for the Faraday dispersion F(?) and ?0(?), along with the current and planned properties of the main radio interferometers, we demonstrate how degeneracies among the parameters describing the magneto-ionic medium can be minimized by combining observations in different wavebands. We also discuss how depolarization by Faraday dispersion due to a random component of the magnetic field attenuates the variations in the spectral energy distribution of the polarization and shifts its peak towards shorter wavelengths. This additional effect reduces the prospect of recovering the characteristics of the magnetic field helicity in magneto-ionic media dominated by the turbulent component of the magnetic field.

Horellou, C.; Fletcher, A.

2014-07-01

301

Formation of Magnetic Particle Chains in Ultra High Magnetic Field  

Microsoft Academic Search

Magnetic particles form chain-like clusters in the magnetic field. This phenomenon is of interest in two separate fields, one is a development system of the laser printer and another is an electromagnetic manipulation of biological cells. Experiments on the chain formation in air and oil have been performed in the ultra high magnetic field created by a superconducting magnet. It

Hiroyuki Kawamoto; Masatomo Teshima; Hiroyuki Takahashi; Nobuyuki Nakayama; Noriyuki Hirota

2007-01-01

302

Photospheric and coronal magnetic fields  

SciTech Connect

Research on small-scale and large-scale photospheric and coronal magnetic fields during 1987-1990 is reviewed, focusing on observational studies. Particular attention is given to the new techniques, which include the correlation tracking of granules, the use of highly Zeeman-sensitive infrared spectral lines and multiple lines to deduce small-scale field strength, the application of long integration times coupled with good seeing conditions to study weak fields, and the use of high-resolution CCD detectors together with computer image-processing techniques to obtain images with unsurpassed spatial resolution. Synoptic observations of large-scale fields during the sunspot cycle are also discussed. 101 refs.

Sheeley, N.R., Jr. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

1991-01-01

303

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.

304

Magnetic Fields of the Earth and Sun  

NSDL National Science Digital Library

This is an activity that compares the magnetic field of the Earth to the complex magnetic field of the Sun. Using images of the Earth and Sun that have magnets attached in appropriate orientations, learners will use a handheld magnetic field detector to observe the magnetic field of the Earth and compare it to that of the Sun, especially in sunspot areas. For each group of students, this activity requires use of a handheld magnetic field detector, such as a Magnaprobe or a similar device, a bar magnet, and ten small disc magnets.

305

BEC manipulation with fictitious magnetic fields  

Microsoft Academic Search

The interaction of Bose-Einstein condensate (BEC) atoms with counterpropagating laser beams can often be represented by fictitious magnetic fields [1]. These fictitious fields can be combined with ordinary magnetic fields to produce total fields whose amplitudes vary in space on the scale of the laser wavelength. When the strengths of such magnetic fields are positioned in the neighborhood of a

Jeffrey Heward; Mark Edwards; Charles W. Clark

2010-01-01

306

Flares and changing magnetic fields  

Microsoft Academic Search

An observational study of maps of the longitudinal component of the photospheric fields in flaring active regions leads to the following conclusions:(1)The broad-wing Ha kernels characteristic of the impulsive phase of flares occur within 10? of neutral lines encircling features of isolated magnetic polarity (‘satellite sunspots’).(2)Photospheric field changes intimately associated with several importance 1 flares and one importance 2B flare

David M. Rust

1972-01-01

307

A Large Volume Double Channel 1H-X RF Probe for Hyperpolarized Magnetic Resonance at 0.0475 Tesla  

PubMed Central

In this work we describe a large volume 340 mL 1H-X magnetic resonance (MR) probe for studies of hyperpolarized compounds at 0.0475 T. 1H/13C and 1H/15N probe configurations are demonstrated with the potential for extension to 1H/129Xe. The primary applications of this probe are preparation and quality assurance of 13C and 15N hyperpolarized contrast agents using PASADENA (parahydrogen and synthesis allow dramatically enhanced nuclear alignment) and other parahydrogen-based methods of hyperpolarization. The probe is efficient and permits 62 ?s 13C excitation pulses at 5.3 Watts, making it suitable for portable operation. The sensitivity and detection limits of this probe, tuned to 13C, are compared with a commercial radio frequency (RF) coil operating at 4.7 T. We demonstrate that low field MR of hyperpolarized contrast agents could be as sensitive as conventional high field detection and outline potential improvements and optimization of the probe design for preclinical in vivo MRI. PASADENA application of this low-power probe is exemplified with 13C hyperpolarized 2-hydroxyethyl propionate-1-13C,2,3,3-d3.

Coffey, Aaron M.; Shchepin, Roman V.; Wilkens, Ken; Waddell, Kevin W.; Chekmenev, Eduard Y.

2012-01-01

308

Ohm's Law for Mean Magnetic Fields.  

National Technical Information Service (NTIS)

The magnetic fields associated with plasmas frequently exhibit small amplitude MHD fluctuations. It is useful to have equations for the magnetic field averaged over these fluctuations, the so-called mean field equations. Under very general assumptions it ...

A. H. Boozer

1986-01-01

309

Energetic and Cell Membrane Metabolic Products in Patients with Primary Insomnia: A 31-Phosphorus Magnetic Resonance Spectroscopy Study at 4 Tesla  

PubMed Central

Study Objectives: Primary insomnia (PI) is a sleep disorder characterized by difficulty with sleep initiation, maintenance, and/or the experience of nonrestorative sleep combined with a subsequent impairment of daytime functioning. The hyperarousal hypothesis has emerged as the leading candidate to explain insomnia symptoms in the absence of specific mental, physical, or substance-related causes. We hypothesized that the cellular energetic metabolites, including beta nucleoside triphosphate, which in magnetic resonance spectroscopy approximates adenosine triphosphate (ATP), and phosphocreatine (PCr), would show changes in PI reflecting increased energy demand. Design and Setting: Matched-groups, cross-sectional study performed at two university-based hospitals. Patients: Sixteen medication-free individuals (eight males, eight females; mean ± standard deviation (SD) age = 37.2 ± 8.4 y) with PI and 16 good sleepers (nine males, seven females; mean ± SD age = 37.6 ± 4.7 y). Measurements: Diagnosis was established for all individuals by unstructured clinical interview, Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (SCID), sleep diary, and actigraphy. Polysomnography was collected in individuals with PI. Phosphorous magnetic resonance spectroscopy (31P MRS) data were collected on all individuals at 4 Tesla. We assessed cell membrane (anabolic precursors and catabolic metabolites) and bioenergetic (ATP, phosphocreatine) metabolites in gray matter and white matter to determine their relationship to the presence and severity of PI. Results: Individuals with PI showed lower phosphocreatine in gray matter and an unexpected decrease of phosphocholine, a precursor of the cell membrane compound phosphatidylcholine, in white matter. In addition, there was a trend toward a negative association between polysomnographically determined wake after sleep onset and gray matter beta-nucleoside triphosphate and white matter phosphocholine in the primary insomnia group. Conclusions: These results support the hyperarousal hypothesis in PI based on lower phosphocreatine in gray matter in the PI group. Citation: Harper DG; Plante DT; Jensen JE; Ravichandran C; Buxton OM; Benson KL; O'Connor SP; Renshaw PF; Winkelman JW. Energetic and cell membrane metabolic products in patients with primary insomnia: a 31-phosphorus magnetic resonance spectroscopy study at 4 tesla. SLEEP 2013;36(4):493-500.

Harper, David G.; Plante, David T.; Jensen, J. Eric; Ravichandran, Caitlin; Buxton, Orfeu M.; Benson, Kathleen L.; O'Connor, Shawn P.; Renshaw, Perry F.; Winkelman, John W.

2013-01-01

310

Swarm: ESA's Magnetic Field Mission  

Microsoft Academic Search

Swarm is the fifth Earth Explorer mission in ESA's Living Planet Programme. The objective of the Swarm mission is to provide the best ever survey of the geomagnetic field and its temporal evolution. The Mission shall deliver data that allow access to new insights into the Earth system by improving our understanding of the Earth's interior and near-Earth electro-magnetic environment.

R. Haagmans; Y. Menard; R. Floberghagen; G. Plank; M. R. Drinkwater

2010-01-01

311

Transverse Magnetic Field Propellant Isolator  

NASA Technical Reports Server (NTRS)

An alternative high voltage isolator for electric propulsion and ground-based ion source applications has been designed and tested. This design employs a transverse magnetic field that increases the breakdown voltage. The design can greatly enhance the operating range of laboratory isolators used for high voltage applications.

Foster, John E.

2000-01-01

312

Large-scale solar magnetic fields  

Microsoft Academic Search

Topics discussed in this review of large-scale solar magnetic fields include large-scale magnetic surface features, the solar activity cycle and the large-scale patterns, and magnetic fields in the corona. Features considered include the decay of active regions, the background field pattern, the polar fields, giant regular structures, expansion of the field in surface harmonics, and the average inclination of magnetic-field

R. Howard

1977-01-01

313

Neonatal Brain Metabolite Concentrations: An In Vivo Magnetic Resonance Spectroscopy Study with a Clinical MR System at 3 Tesla  

PubMed Central

Brain metabolite concentrations change dynamically throughout development, especially during early childhood. The purpose of this study was to investigate the brain metabolite concentrations of neonates (postconceptional age (PCA): 30 to 43 weeks) using single-voxel magnetic resonance spectroscopy (MRS) and to discuss the relationships between the changes in the concentrations of such metabolites and brain development during the neonatal period. A total of 83 neonatal subjects were included using the following criteria: the neonates had to be free of radiological abnormalities, organic illness, and neurological symptoms; the MR spectra had to have signal-to-noise ratios ? 4; and the estimated metabolite concentrations had to display Cramér-Rao lower bounds of ? 30%. MRS data (echo time/repetition time, 30/5000 ms; 3T) were acquired from the basal ganglia (BG), centrum semiovale (CS), and the cerebellum. The concentrations of five metabolites were measured: creatine, choline, N-acetylaspartate, myo-inositol, and glutamate/glutamine complex (Glx). One hundred and eighty-four MR spectra were obtained (83 BG, 77 CS, and 24 cerebellum spectra). Creatine, N-acetylaspartate, and Glx displayed increases in their concentrations with PCA. Choline was not correlated with PCA in any region. As for myo-inositol, its concentration decreased with PCA in the BG, whereas it increased with PCA in the cerebellum. Quantitative brain metabolite concentrations and their changes during the neonatal period were assessed. Although the observed changes were partly similar to those detected in previous reports, our results are with more subjects (n = 83), and higher magnetic field (3T). The metabolite concentrations examined in this study and their changes are clinically useful indices of neonatal brain development.

Tomiyasu, Moyoko; Aida, Noriko; Endo, Mamiko; Shibasaki, Jun; Nozawa, Kumiko; Shimizu, Eiji; Tsuji, Hiroshi; Obata, Takayuki

2013-01-01

314

Spontaneous electromagnetic superconductivity of vacuum in strong magnetic field: an evidence from the Nambu--Jona-Lasinio model  

Microsoft Academic Search

Using an extended Nambu--Jona-Lasinio model as a low energy effective model\\u000aof QCD, we support our earlier proposal that the QCD vacuum in a strong\\u000aexternal magnetic field (stronger than 10^{16} Tesla) experiences a spontaneous\\u000aphase transition to an electromagnetically superconducting state. The\\u000aunexpected superconductivity of, basically, empty space is induced by emergence\\u000aof quark-antiquark vector condensates with quantum numbers

M. N. Chernodub

2010-01-01

315

Magnetic fields in the sun  

NASA Technical Reports Server (NTRS)

The observed properties of solar magnetic fields are reviewed, with particular reference to the complexities imposed on the field by motions of the highly conducting gas. Turbulent interactions between gas and field lead to heating or cooling of the gas according to whether the field energy density is less or greater than the maximum kinetic energy density in the convection zone. The field strength above which cooling sets in is 700 gauss. A weak solar dipole field may be primeval, but dynamo action is also important in generating new flux. The dynamo is probably not confined to the convection zone, but extends throughout most of the volume of the sun. Planetary tides appear to play a role in driving the dynamo.

Mullan, D. J.

1974-01-01

316

Applications of high dielectric materials in high field magnetic resonance  

NASA Astrophysics Data System (ADS)

At high magnetic fields, radiation losses, wavelength effects, self-resonance, and the high resistance of components all contribute to losses in conventional RF MRI coil designs. The hypothesis tested here is that these problems can be combated by the use of high permittivity ceramic materials at high fields. High permittivity ceramic dielectric resonators create strong uniform magnetic fields in compact structures at high frequencies and can potentially solve some of the challenges of high field coil design. In this study NMR probes were constructed for operation at 600 MHz (14.1 Tesla) and 900 MHz (21.1 Tesla) using inductively fed CaTiO3 (relative permittivity of 156-166) cylindrical hollow bore dielectric resonators. The designs showed the electric field is largely confined to the dielectric itself, with near zero values in the hollow bore, which accommodates the sample. The 600 MHz probe has an unmatched Q value greater than 2000. Experimental and simulation mapping of the RF field show good agreement, with the ceramic resonator giving a pulse width approximately 25% less than a loop gap resonator of similar inner dimensions. High resolution images, with voxel dimensions less than 50 microm3, have been acquired from fixed zebrafish samples, showing excellent delineation of several fine structures. The 900 MHz probe has an unmatched Q value of 940 and shows Q performance five times better than Alderman-Grant and loop-gap resonators of similar dimensions. High resolution images were acquired of an excised mouse spinal cord (25 microm 3) and an excised rat soleus muscle (20 microm3). The spatial distribution of electromagnetic fields within the human body can be tailored using external dielectric materials. Here, a new material is introduced with high dielectric constant and low background MRI signal. The material is based upon metal titanates, which can be made into geometrically formable suspensions in de-ionized water. The suspension's material properties are characterized from 100 to 400 MHz. Results obtained at 7 T show a significant increase in image intensity in areas such as the temporal lobe and base of the brain with the new material placed around the head, and improved performance compared to purely water-based gels.

Haines, Kristina Noel

317

Magnetic field of the Earth  

NASA Astrophysics Data System (ADS)

The magnetic field of the Earth has global meaning for a life on the Earth. The world geophysical science explains: - occurrence of a magnetic field of the Earth it is transformation of kinetic energy of movements of the fused iron in the liquid core of Earth - into the magnetic energy; - the warming up of a kernel of the Earth occurs due to radioactive disintegration of elements, with excretion of thermal energy. The world science does not define the reasons: - drift of a magnetic dipole on 0,2 a year to the West; - drift of lithospheric slabs and continents. The author offers: an alternative variant existing in a world science the theories "Geodynamo" - it is the theory « the Magnetic field of the Earth », created on the basis of physical laws. Education of a magnetic field of the Earth occurs at moving the electric charge located in a liquid kernel, at rotation of the Earth. At calculation of a magnetic field is used law the Bio Savara for a ring electric current: dB = . Magnetic induction in a kernel of the Earth: B = 2,58 Gs. According to the law of electromagnetic induction the Faradey, rotation of a iron kernel of the Earth in magnetic field causes occurrence of an electric field Emf which moves electrons from the center of a kernel towards the mantle. So of arise the radial electric currents. The magnetic field amplifies the iron of mantle and a kernel of the Earth. As a result of action of a radial electric field the electrons will flow from the center of a kernel in a layer of an electric charge. The central part of a kernel represents the field with a positive electric charge, which creates inverse magnetic field Binv and Emfinv When ?mfinv = ?mf ; ?inv = B, there will be an inversion a magnetic field of the Earth. It is a fact: drift of a magnetic dipole of the Earth in the western direction approximately 0,2 longitude, into a year. Radial electric currents a actions with the basic magnetic field of a Earth - it turn a kernel. It coincides with laws of electromagnetism. According to a rule of the left hand: if the magnetic field in a kernel is directed to drawing, electric current are directed to an axis of rotation of the Earth, - a action of force clockwise (to West). Definition of the force causing drift a kernel according to the law of Ampere F = IBlsin. Powerful force 3,5 × 1012 Nyton, what makes drift of the central part of a kernel of the Earth on 0,2 the longitude in year to West, and also it is engine of the mechanism of movement of slabs together with continents. Movement of a core of the Earth carry out around of a terrestrial axis one circulation in the western direction in 2000 of years. Linear speed of rotation of a kernel concerning a mantle on border the mantle a kernel: V = × 3,471 × 10 = 3,818 × 10 m/s = 33 m/day = 12 km/years. Considering greater viscosity of a mantle, the powerful energy at rotation of a kernel seize a mantle and lithospheric slabs and makes their collisions as a result of which there are earthquakes and volcano. Continents Northern and Southern America every year separate from the Europe and Africa on several centimeters. Atlantic ocean as a result of movement of these slabs with such speed was formed for 200 million years, that in comparison with the age of the Earth - several billions years, not so long time. Drift of a kernel in the western direction is a principal cause of delay of speed of rotation of the Earth. Flow of radial electric currents allot according to the law of Joule - Lenz, the quantity of warmth : Q = I2Rt = IUt, of thermal energy 6,92 × 1017 calories/year. This defines heating of a kernel and the Earth as a whole. In the valley of the median-Atlantic ridge having numerous volcanos, the lava flow constantly thus warm up waters of Atlantic ocean. It is a fact the warm current Gulf Stream. Thawing of a permafrost and ices of Arctic ocean, of glaciers of Greenland and Antarctica is acknowledgement: the warmth of earth defines character of thawing of glaciers and a permafrost. This is a global warming. The version of the author: the period

Popov, Aleksey

2013-04-01

318

Electron dynamics in inhomogeneous magnetic fields.  

PubMed

This review explores the dynamics of two-dimensional electrons in magnetic potentials that vary on scales smaller than the mean free path. The physics of microscopically inhomogeneous magnetic fields relates to important fundamental problems in the fractional quantum Hall effect, superconductivity, spintronics and graphene physics and spins out promising applications which will be described here. After introducing the initial work done on electron localization in random magnetic fields, the experimental methods for fabricating magnetic potentials are presented. Drift-diffusion phenomena are then described, which include commensurability oscillations, magnetic channelling, resistance resonance effects and magnetic dots. We then review quantum phenomena in magnetic potentials including magnetic quantum wires, magnetic minibands in superlattices, rectification by snake states, quantum tunnelling and Klein tunnelling. The third part is devoted to spintronics in inhomogeneous magnetic fields. This covers spin filtering by magnetic field gradients and circular magnetic fields, electrically induced spin resonance, spin resonance fluorescence and coherent spin manipulation. PMID:21393794

Nogaret, Alain

2010-06-30

319

Oxide superconductors under magnetic field  

NASA Technical Reports Server (NTRS)

One of the current most serious problems for the oxide superconductors from the standpoint of practical application is the various novel features derived mainly from their extremely short coherence. In particular, the coherence length so far observed in the cuprate superconductors is in the range of 0.1 nm perpendicular to the CuO2 plane. This seems to be creating most of the difficulties in the device fabrication and in the performance under the magnetic field. Some of the superconducting properties under the magnetic field will be discussed in terms of the short coherence length. A model will be presented based on the gradual strengthening of the pinning force with decrease in temperature and the weak coupling at the grain boundaries. Secondly, the broadening of the superconducting transition under the magnetic field is discussed. This is observed significantly only when the field is applied perpendicular to the basal plane and the relative orientation of the current to the field is insignificant in determining the extent of the broadening. Besides, the change in the strength of the pinning force does not affect the width of the broadening. From these observations discussions will be made on a model based on the giant fluctuation. Based on this model, it is predicted that the coherence length along the c-axis will be the single most important material parameter to determine the performance of the superconductor under a strong magnetic field. It seems that BYCO is superior in this regard to Bi- or Tl-systems as far as the performance at 77 K is considered, although another material with the coherence length slightly longer along the c-axis is still highly desired.

Kitazawa, K.

1990-01-01

320

Oxide superconductors under magnetic field  

NASA Technical Reports Server (NTRS)

One of the current most serious problems for the oxide superconductors from the standpoint of practical application is the various novel features derived mainly from their extremely short coherence. In particular, the coherence length so far observed in the cuprate superconductors is in the range of 0.1 nm perpendicular to the CuO2 plane. This seems to be creating most of the difficulties in the device fabrication and in the performance under the magnetic field. Some of the superconducting properties under the magnetic field will be discussed in terms of the short coherence length. A model will be presented based on the gradual strengthening of the pinning force with decrease in temperature and the weak coupling at the grain boundaries. Secondly, the broadening of the superconducting transition under the magnetic field is discussed. This is observed significantly only when the field is applied perpendicular to the basal plane and the relative orientation of the current to the field is insignificant in determining the extent of broadening. Besides, the change in the strength of the pinning force does not affect the width of the broadening. From these observations discussions will be made on a model based on the giant fluctuation. Based on this model, it is predicted that the coherence length along the c-axis will be the single most important material parameter to determine the performance of the superconductor under a strong magnetic field. It seems that BYCO is superior in this regard to Bi- or Tl-systems as far as the performance at 77 K is considered, although another material with the coherence length slightly longer along the c-axis is still highly desired.

Kitazawa, K.

1991-01-01

321

Head tilt in rats during exposure to a high magnetic field  

PubMed Central

During exposure to high strength static magnetic fields, humans report vestibular symptoms such as vertigo, apparent motion, and nausea. Rodents also show signs of vestibular perturbation after magnetic field exposure at 7 tesla (T) and above, such as locomotor circling, activation of vestibular nuclei, and acquisition of conditioned taste aversions. We hypothesized that the acute effects of the magnetic field might be seen as changes in head position during exposure within the magnet. Using a yoked restraint tube that allowed movement of the head and neck, we found that rats showed an immediate and persistent deviation of the head during exposure to a static 14.1 T magnetic field. The direction of the head tilt was dependent on the orientation of the rat in the magnetic field (B), such that rats oriented head-up (snout towards B+) showed a rightward tilt of the head, while rats oriented head–down (snout towards B?) showed a leftward tilt of the head. The tilt of the head during magnet exposure was opposite to the direction of locomotor circling immediately after exposure observed previously. Rats exposed in the yoked restraint tube showed significantly more locomotor circling compared to rats exposed with the head restrained. There was little difference in CTA magnitude or extinction rate, however. The deviation of the head was seen when the rats were motionless within the homogenous static field; movement through the field or exposure to the steep gradients of the field was not necessary to elicit the apparent vestibulo-collic reflex.

Houpt, Thomas A.; Cassell, Jennifer; Carella, Lee; Neth, Bryan; Smith, James C.

2011-01-01

322

Dynamics of Magnetic Bubbles in Acoustic and Magnetic Fields  

Microsoft Academic Search

We report on shelled bubbles that can be manipulated with magnetic fields. The magnetic shell consists of self-assembled magnetic nanoparticles. The magnetic susceptibility of the bubbles is proportional to the surface area, chib=(9±3×10-6m)r2 where r is the radius. Magnetic bubbles are compressible in moderate acoustic fields. A bubble with a radius of 121mum oscillates in resonance in a sound field

Xue Zhao; Pedro A. Quinto-Su; Claus-Dieter Ohl

2009-01-01

323

Design and optimization of force-reduced high field magnets  

NASA Astrophysics Data System (ADS)

High field magnets have many important applications in different areas of research, in the power industry and also for military purposes. For example, high field magnets are particularly useful in: material sciences, high energy physics, plasma physics (as fusion magnets), high power applications (as energy storage devices), and space applications (in propulsion systems). One of the main issues with high-field magnets is the presence of very large electromagnetic stresses that must be counteracted and therefore require heavy support structures. In superconducting magnets, the problems caused by Lorentz forces are further complicated by the fact that superconductors for high field applications are pressure sensitive. The current carrying capacity is greatly reduced under stress and strain (especially in the case of Nb 3Sn and the new high temperature superconductors) so the reduction of the acting forces is of even greater importance. Different force-reduced magnet concepts have been studied in the past, both numerical and analytical methods have been used to solve this problem. The developed concepts are based on such complex winding geometries that the realization and manufacturing of such coils is extremely difficult and these concepts are mainly of theoretical interest. In the presented research, a novel concept for force-reduced magnets has been developed and analyzed which is easy to realize and therefore is of practical interest. The analysis has been performed with a new methodology, which does not require the time consuming finite element calculations. The developed computer models describe the 3-dimensional winding configuration by sets of filaments (filamentary approximation). This approach is much faster than finite element analysis and therefore allows rapid optimization of concepts. The method has been extensively tested on geometries of force-reduced solenoids where even analytical solutions exist. As a further cross check, the developed computer codes have been tested against qualified finite element codes and found to be in excellent agreement. The developed concept of force-reduced coils is directly applicable to pulsed magnets and a conceptual design of a 25 Tesla magnet has been developed. Although no experimental proof was possible within the scope of this research, there is strong evidence to believe that the developed concept is also applicable to superconducting magnets operating in a constant current mode.

Rembeczki, Szabolcs

324

High-resolution phased-array MRI of the human brain at 7 tesla: initial experience in multiple sclerosis patients  

Microsoft Academic Search

Recent advancement for magnetic resonance imaging (MRI) involves the incorporation of higher-field strengths. Although imagers with higher magnetic field strengths were developed and tested in research labs, the direct application to patient MR studies have been extremely limited. Imaging at 7 Tesla (7T) affords advantages in signal-to-noise ratio and image contrast and resolution; however, these benefits can only be realized

Meredith Metcalf; Duan Xu; Darin T Okuda; Lucas Carvajal; Radhika Srinivasan; Douglas A C Kelley; Pratik Mukherjee; Sarah J Nelson; Daniel B Vigneron; Daniel Pelletier

2010-01-01

325

Diagnostics of vector magnetic fields  

NASA Technical Reports Server (NTRS)

It is shown that the vector magnetic fields derived from observations with a filter magnetograph will be severely distorted if the spatially unresolved magnetic structure is not properly accounted for. Thus the apparent vector field will appear much more horizontal than it really is, but this distortion is strongly dependent on the area factor and the temperature line weakenings. As the available fluxtube models are not sufficiently well determined, it is not possible to correct the filter magnetograph observations for these effects in a reliable way, although a crude correction is of course much better than no correction at all. The solution to this diagnostic problem is to observe simultaneously in suitable combinations of spectral lines, and/or use Stokes line profiles recorded with very high spectral resolution. The diagnostic power of using a Fourier transform spectrometer for polarimetry is shown and some results from I and V spectra are illustrated. The line asymmetries caused by mass motions inside the fluxtubes adds an extra complication to the diagnostic problem, in particular as there are indications that the motions are nonstationary in nature. The temperature structure appears to be a function of fluxtube diameter, as a clear difference between plage and network fluxtubes was revealed. The divergence of the magnetic field with height plays an essential role in the explanation of the Stokes V asymmetries (in combination with the mass motions). A self consistent treatment of the subarcsec field geometry may be required to allow an accurate derivation of the spatially averaged vector magnetic field from spectrally resolved data.

Stenflo, J. O.

1985-01-01

326

Proposed applications with implementation techniques of the upcoming renewable energy resource, The Tesla Turbine  

NASA Astrophysics Data System (ADS)

Recent research has shown that tesla turbine can be one of the future efficient sources of renewable energy. Modern techniques used for designing of tesla turbine have given optimum results regarding efficiency and applications. In this paper we have suggested fully coordinated applications of tesla turbine in different fields particularly in power generation at both low level and high level generation. In Energy deficient countries the tesla turbine has wide range of applications and it can play an important role in energy management system. Our proposed applications includes, the use of tesla turbine as renewable energy resource using tesla turbine in distributed generation system use of tesla turbine at home for power generation use of tesla turbine in irrigation channels using tesla turbine in hybrid electric vehicles All applications are explained with the help of flow charts and block diagrams and their implementation techniques are also explained in details. The results of physical experiments and simulations are also included for some applications.

Usman Saeed Khan, M.; Maqsood, M. Irfan; Ali, Ehsan; Jamal, Shah; Javed, M.

2013-06-01

327

Dependence of oxygen delivery on blood flow in rat brain: a 7 tesla nuclear magnetic resonance study.  

PubMed

Magnetic resonance imaging (MRI) and spectroscopy (MRS) were used at a magnetic field strength of 7 T to measure CBF and CMRO2 in the sensorimotor cortex of mature rats at different levels of cortical activity. In rats maintained on morphine anesthesia, transitions to lower activity and higher activity states were produced by administration of pentobarbital and nicotine, respectively. Under basal conditions of morphine sulfate anesthesia, CBF was 0.75 +/- 0.09 mL x g(-1) x min(-1) and CMRO2 was 3.15 +/- 0.18 micromol x g(-1) x min(-1). Administration of sodium pentobarbital reduced CBF and CMRO2 by 66% +/- 16% and 61% +/- 6%, respectively (i.e., "deactivation"). In contrast, administration of nicotine hydrogen tartrate increased CBF and CMRO2 by 41% +/- 5% and 30% +/- 3%, respectively (i.e., "activation"). The resting values of CBF and CMRO2 for alpha-chloralose anesthetized rats were 0.40 +/- 0.09 mL x g(-1) x min(-1) and 1.51 +/- 0.06 micromol x g(-1) x min(-1), respectively. Upon forepaw stimulation, CBF and CMRO2 were focally increased by 34% +/- 10% and 26% +/- 12%, respectively, above the resting nonanesthetized values (i.e., "activation"). Incremental changes in CBF and CMRO2, when expressed as a percentage change for "deactivation" and "activation" from the respective control conditions, were linear (R2 = 0.997) over the entire range examined with the global and local perturbations. This tight correlation for cerebral oxygen delivery in vivo is supported by a recent model where the consequence of a changing effective diffusivity of the capillary bed for oxygen, D, has been hypothetically shown to be linked to alterations in CMRO2 and CBF. This assumed functional characteristic of the capillary bed can be theoretically assessed by the ratio of fractional changes in D with respect to changes in CBF, signified by omega. A value 0.81 +/- 0.23 was calculated for omega with the in vivo data presented here, which in turn corresponds to a supposition that the effective oxygen diffusivity of the capillary bed is not constant but presumably varies to meet local requirements in oxygen demand in a similar manner with both "deactivation" and "activation." PMID:10724113

Hyder, F; Kennan, R P; Kida, I; Mason, G F; Behar, K L; Rothman, D

2000-03-01

328

Explaining Mercury's peculiar magnetic field  

NASA Astrophysics Data System (ADS)

MESSENGER magnetometer data revealed that Mercury's magnetic field is not only particularly weak but also has a peculiar geometry. The MESSENGER team finds that the location of the magnetic equator always lies significantly north of the geographic equator, is largely independent of the distance to the planet, and also varies only weakly with longitude. The field is best described by an axial dipole that is offset to the north by about 20% of the planetary radius. In terms of classical Gauss coefficients, this translates into a low axial dipole component of g10= -190 nT but a relatively large axial quadrupole contribution that amounts to roughly 40% of this value. The axial octupole is also sizable while higher harmonic contributions are much weaker. Very remarkable is also the fact that the equatorial dipole contribution is very small, consistent with a dipole tilt below 0.8 degree, and this is also true for the other non-axisymmetic field contributions. We analyze several numerical dynamos concerning their capability of explaining Mercury's magnetic field. Classical schemes geared to model the geomagnetic field typically show a much weaker quadrupole component and thus a smaller offset. The onset only becomes larger when the dynamo operates in the multipolar regime at higher Rayleigh numbers. However, since the more complex dynamics generally promotes all higher multipole contributions the location of the magnetic equator varies strongly with longitude and distance to the planet. The situation improves when introducing a stably stratified outer layer in the dynamo region, representing either a rigid FeS layer or a sub-adiabatic core-mantle boundary heat flux. This layer filters out the higher harmonic contributions and the field not only becomes sufficiently weak but also assumes a Mercury like offset geometry during a few percent of the simulation time. To increase the likelihood for the offset configuration, the north-south symmetry must be permanently broken and we explore two scenarios. Increasing the heat flux through the northern hemisphere of the core-mantle boundary is an obvious choice but is not supported by current models for Mercury's mantle. We find that a combination of internal rather than bottom driving and an increased heat flux through the equatorial region of the core-mantle boundary also promotes the required symmetry breaking and results in very Mercury like fields. The reason is that the imposed heat flux pattern, though being equatorially symmetric, lowers the critical Rayleigh number for the onset of equatorially anti-symmetric convection modes. In both scenarios, a stably stratified layer or a feedback coupling to the magnetospheric field is required for lowering the field strength to Mercury-like values.

Wicht, Johannes; Cao, Hao; Heyner, Daniel; Dietrich, Wieland; Christensen, Ulrich R.

2014-05-01

329

Magnetic domain structure in thin film under alternate magnetic field  

Microsoft Academic Search

Magnetic domain structures in a garnet thin film under alternate magnetic fields have been investigated. In alternate magnetic fields, a labyrinth structure approaches a parallel-stripe structure. The competition among the segment clusters, in which stripes have different directions, causes stable dynamical domain structures. With the increase of the amplitude of alternate fields, the segment clusters become small.

M. Mino; H. Yamazaki

2004-01-01

330

Magnetic domain structure in thin film under alternate magnetic field  

NASA Astrophysics Data System (ADS)

Magnetic domain structures in a garnet thin film under alternate magnetic fields have been investigated. In alternate magnetic fields, a labyrinth structure approaches a parallel-stripe structure. The competition among the segment clusters, in which stripes have different directions, causes stable dynamical domain structures. With the increase of the amplitude of alternate fields, the segment clusters become small.

Mino, M.; Yamazaki, H.

331

Magnetic domain structure in thin film under alternate magnetic field  

NASA Astrophysics Data System (ADS)

Magnetic domain structures in a garnet thin film under alternate magnetic fields have been investigated. In alternate magnetic fields, a labyrinth structure approaches a parallel-stripe structure. The competition among the segment clusters, in which stripes have different directions, causes stable dynamical domain structures. With the increase of the amplitude of alternate fields, the segment clusters become small.

Mino, M.; Yamazaki, H.

2004-05-01

332

Comparing Magnetic Fields on Earth and Mars  

NASA Video Gallery

This animation compares the magnetic fields on Earth and Mars. The Earth has a large-scale planetary magnetic field that can protect it from space weather and other hazards. Mars, on the other hand...

333

Measurements of Solar Vector Magnetic Fields  

NASA Technical Reports Server (NTRS)

Various aspects of the measurement of solar magnetic fields are presented. The four major subdivisions of the study are: (1) theoretical understanding of solar vector magnetic fields; (3) techniques for interpretation of observational data; and (4) techniques for data display.

Hagyard, M. J. (editor)

1985-01-01

334

Anisotropic Magnetism in Field-Structured Composites  

SciTech Connect

Magnetic field-structured-composites (FSCs) are made by structuring magnetic particle suspensions in uniaxial or biaxial (e.g. rotating) magnetic fields, while polymerizing the suspending resin. A uniaxial field produces chain-like particle structures, and a biaxial field produces sheet-like particle structures. In either case, these anisotropic structures affect the measured magnetic hysteresis loops, with the magnetic remanence and susceptibility increased significantly along the axis of the structuring field, and decreased slightly orthogonal to the structuring field, relative to the unstructured particle composite. The coercivity is essentially unaffected by structuring. We present data for FSCs of magnetically soft particles, and demonstrate that the altered magnetism can be accounted for by considering the large local fields that occur in FSCs. FSCS of magnetically hard particles show unexpectedly large anisotropies in the remanence, and this is due to the local field effects in combination with the large crystalline anisotropy of this material.

Anderson, Robert A.; Martin, James E.; Odinek, Judy; Venturini, Eugene

1999-06-24

335

Brain Activation in Response to Visually Evoked Sexual Arousal in Male-to-Female Transsexuals: 3.0 Tesla Functional Magnetic Resonance Imaging  

PubMed Central

Objective This study used functional magnetic resonance imaging (fMRI) to contrast the differential brain activation patterns in response to visual stimulation with both male and female erotic nude pictures in male-to-female (MTF) transsexuals who underwent a sex reassignment surgery. Materials and Methods A total of nine healthy MTF transsexuals after a sex reassignment surgery underwent fMRI on a 3.0 Tesla MR Scanner. The brain activation patterns were induced by visual stimulation with both male and female erotic nude pictures. Results The sex hormone levels of the postoperative MTF transsexuals were in the normal range of healthy heterosexual females. The brain areas, which were activated by viewing male nude pictures when compared with viewing female nude pictures, included predominantly the cerebellum, hippocampus, putamen, anterior cingulate gyrus, head of caudate nucleus, amygdala, midbrain, thalamus, insula, and body of caudate nucleus. On the other hand, brain activation induced by viewing female nude pictures was predominantly observed in the hypothalamus and the septal area. Conclusion Our findings suggest that distinct brain activation patterns associated with visual sexual arousal in postoperative MTF transsexuals reflect their sexual orientation to males.

Oh, Seok-Kyun; Kim, Gwang-Won; Yang, Jong-Chul; Kim, Seok-Kwun; Kang, Heoung-Keun

2012-01-01

336

Preliminary evidence for white matter metabolite differences in marijuana dependent young men using 2D J-resolved magnetic resonance spectroscopic imaging at 4 Tesla  

PubMed Central

Chronic marijuana (MRJ) use is associated with altered cognition and mood state, altered brain metabolites, functional and structural brain changes. The objective of this study was to apply proton magnetic resonance spectroscopic imaging (MRSI) to compare proton metabolite levels in 15 young men with MRJ-dependence and 11 healthy non-using (NU) young men. Spectra were acquired at 4.0 Tesla using 2D J-resolved MRSI to resolve coupled resonances in J-space and to quantify the entire J-coupled spectral surface of metabolites from voxels containing basal ganglia and thalamus, temporal and parietal lobe, and occipital white and gray matter. This method permitted investigation of high-quality spectra for regression analyses to examine metabolites relative to tissue type. Distribution of myo-inositol (mI)/creatine (Cr) was altered in the MRJ group whereas the NU group exhibited higher mI/Cr in WM than GM, this pattern was not observed in MRJ subjects. Significant relationships observed between global mI/Cr and distribution in WM, and self-reported impulsivity and mood symptoms were also unique between MRJ and NU groups. These preliminary findings suggest that mI, and distribution of this glial metabolite in WM, is altered by MRJ use and is associated with behavioral and affective features reported by young MRJ-dependent men.

Silveri, Marisa M.; Jensen, J. Eric; Rosso, Isabelle M.; Sneider, Jennifer T.; Yurgelun-Todd, Deborah A.

2010-01-01

337

Assessment of safety and interference issues of radio frequency identification devices in 0.3 Tesla magnetic resonance imaging and computed tomography.  

PubMed

The objective of this study was to evaluate two issues regarding magnetic resonance imaging (MRI) including device functionality and image artifacts for the presence of radio frequency identification devices (RFID) in association with 0.3 Tesla at 12.7 MHz MRI and computed tomography (CT) scanning. Fifteen samples of RFID tags with two different sizes (wristband and ID card types) were tested. The tags were exposed to several MR-imaging conditions during MRI examination and X-rays of CT scan. Throughout the test, the tags were oriented in three different directions (axial, coronal, and sagittal) relative to MRI system in order to cover all possible situations with respect to the patient undergoing MRI and CT scanning, wearing a RFID tag on wrist. We observed that the tags did not sustain physical damage with their functionality remaining unaffected even after MRI and CT scanning, and there was no alternation in previously stored data as well. In addition, no evidence of either signal loss or artifact was seen in the acquired MR and CT images. Therefore, we can conclude that the use of this passive RFID tag is safe for a patient undergoing MRI at 0.3 T/12.7 MHz and CT Scanning. PMID:24701187

Periyasamy, M; Dhanasekaran, R

2014-01-01

338

Assessment of Safety and Interference Issues of Radio Frequency Identification Devices in 0.3 Tesla Magnetic Resonance Imaging and Computed Tomography  

PubMed Central

The objective of this study was to evaluate two issues regarding magnetic resonance imaging (MRI) including device functionality and image artifacts for the presence of radio frequency identification devices (RFID) in association with 0.3?Tesla at 12.7?MHz MRI and computed tomography (CT) scanning. Fifteen samples of RFID tags with two different sizes (wristband and ID card types) were tested. The tags were exposed to several MR-imaging conditions during MRI examination and X-rays of CT scan. Throughout the test, the tags were oriented in three different directions (axial, coronal, and sagittal) relative to MRI system in order to cover all possible situations with respect to the patient undergoing MRI and CT scanning, wearing a RFID tag on wrist. We observed that the tags did not sustain physical damage with their functionality remaining unaffected even after MRI and CT scanning, and there was no alternation in previously stored data as well. In addition, no evidence of either signal loss or artifact was seen in the acquired MR and CT images. Therefore, we can conclude that the use of this passive RFID tag is safe for a patient undergoing MRI at 0.3 T/12.7?MHz and CT Scanning.

Periyasamy, M.; Dhanasekaran, R.

2014-01-01

339

Visualization of the Foramen Intervertebral Nerve Root of Cervical Spine with 3.0 Tesla Magnetic Resonance Imaging: A Comparison of Three-dimensional Acquisition Techniques.  

PubMed

Identification of the compression factor in cervical disc herniation and cervical spondylotic radioculopathy is often problematic when using two-dimensional magnetic resonance imaging (MRI). This prompted us to compare and examined three-dimensional sequences, coherent oscillatory state acquisition for the manipulation of image contrast (COSMIC), fast imaging employing steady state acquisition (FIESTA) and T2 star weighted MR angiography (SWAN) with 3.0-Tesla (T) MRI to visualize the foramen intervertebral nerve root for the cervical spine. Fat-suppressed COSMIC (FS-COSMIC) sequence gave the highest signal intensity ratio (1.85±0.06) of the nerve root and vertebral arch. A significant difference in signal intensity ratio of the nerve root was found between FS-COSMIC and FIESTA sequences. No significant difference was found between the FS-COSMIC and FIESTA sequences in the cerebrospinal fluid and the spinal cord. The FS-COSMIC sequence proved to be the most suitable sequence for intra and extra dura matter. PMID:25055947

Shishido, Hiroki; Takashima, Hiroyuki; Takebayashi, Tsuneo; Akatsuka, Yoshihiro; Imamura, Rui; Nagahama, Hiroshi; Shirase, Ryuzi

2014-07-01

340

The Role of Magnetic Resonance Imaging (MRI) in Prostate Cancer Imaging and Staging at 1.5 and 3 Tesla : The Beth Israel Deaconess Medical Center (BIDMC) Approach  

PubMed Central

Management decisions for patients with prostate cancer present a dilemma for both patients and their clinicians because prostate cancers demonstrate a wide range in biologic activity, with the majority of cases not leading to a prostate cancer related death. Furthermore, the current treatment options have significant side effects, such as incontinence, rectal injury and impotence. Key elements for guiding appropriate treatment include: distinction of organ-confined disease from extracapsular extension (ECE); and determination of tumor volume and tumor grade, none of which have been satisfactorily accomplished in today’s pre-treatment paradigm. Magnetic resonance imaging (MRI) has the capability to assess prostate tissue, both functionally and morphologically. MRI as a staging tool has not shown enough consistency or sufficient accuracy for widespread adoption in clinical practice; yet, recent technical developments in MRI have yielded improved results. At our institution we have combined the use of new endorectal 3 Tesla MRI technology, T2-weighted, and high spatial resolution dynamic-contrast enhanced (DCE) MRI to non-invasively assess the prostate with higher signal-to-noise ratio and spatial resolution than previously achieved. This approach allows assessment of prostate-tissue morphology and kinetics, thus providing a non-invasive tool for tumor detection and staging and, consequently, directing biopsy and treatment specifically to diseased areas for a pre-treatment evaluation that can assist in the rational selection of patients for appropriate prostate cancer therapy.

Bloch, B. Nicolas; Lenkinski, Robert. E.; Rofsky, Neil M.

2009-01-01

341

Magnetic order of UPt3 in high magnetic fields  

NASA Astrophysics Data System (ADS)

The weak magnetic order of the heavy-fermion superconductor UPt3 has been investigated by elastic neutron-scattering measurements in magnetic fields up to 12 T along the a and c axes of the hexagonal crystal structure. The small antiferromagnetically ordered moment of 0.02?B/(U atom) shows only a weak dependence on the applied magnetic field and no sign of a domain repopulation for B?a. In high magnetic fields an increase in the magnetic correlation length is observed for magnetic fields along the c axis.

van Dijk, N. H.; Fåk, B.; Regnault, L. P.; Huxley, A.; Fernández-Díaz, M.-T.

1998-08-01

342

Early microvascular dysfunction in cerebral small vessel disease is not detectable on 3.0 Tesla magnetic resonance imaging: a longitudinal study in spontaneously hypertensive stroke-prone rats  

PubMed Central

Background Human cerebral small vessel disease (CSVD) has distinct histopathologic and imaging findings in its advanced stages. In spontaneously hypertensive stroke-prone rats (SHRSP), a well-established animal model of CSVD, we recently demonstrated that cerebral microangiopathy is initiated by early microvascular dysfunction leading to the breakdown of the blood–brain barrier and an activated coagulatory state resulting in capillary and arteriolar erythrocyte accumulations (stases). In the present study, we investigated whether initial microvascular dysfunction and other stages of the pathologic CSVD cascade can be detected by serial magnetic resonance imaging (MRI). Findings Fourteen SHRSP and three control (Wistar) rats (aged 26–44 weeks) were investigated biweekly by 3.0 Tesla (3 T) MRI. After perfusion, brains were stained with hematoxylin–eosin and histology was correlated with MRI data. Three SHRSP developed terminal CSVD stages including cortical, hippocampal, and striatal infarcts and macrohemorrhages, which could be detected consistently by MRI. Corresponding histology showed small vessel thromboses and increased numbers of small perivascular bleeds in the infarcted areas. However, 3 T MRI failed to visualize intravascular erythrocyte accumulations, even in those brain regions with the highest densities of affected vessels and the largest vessels affected by stases, as well as failing to detect small perivascular bleeds. Conclusion Serial MRI at a field strength of 3 T failed to detect the initial microvascular dysfunction and subsequent small perivascular bleeds in SHRSP; only terminal stages of cerebral microangiopathy were reliably detected. Further investigations at higher magnetic field strengths (7 T) using blood- and flow-sensitive sequences are currently underway.

2013-01-01

343

Prospective screening study of 0.5 Tesla dedicated magnetic resonance imaging for the detection of breast cancer in young, high-risk women  

PubMed Central

Background Evidence-based screening guidelines are needed for women under 40 with a family history of breast cancer, a BRCA1 or BRCA2 mutation, or other risk factors. An accurate assessment of breast cancer risk is required to balance the benefits and risks of surveillance, yet published studies have used narrow risk assessment schemata for enrollment. Breast density limits the sensitivity of film-screen mammography but is not thought to pose a limitation to MRI, however the utility of MRI surveillance has not been specifically examined before in women with dense breasts. Also, all MRI surveillance studies yet reported have used high strength magnets that may not be practical for dedicated imaging in many breast centers. Medium strength 0.5 Tesla MRI may provide an alternative economic option for surveillance. Methods We conducted a prospective, nonrandomized pilot study of 30 women age 25–49 years with dense breasts evaluating the addition of 0.5 Tesla MRI to conventional screening. All participants had a high quantitative breast cancer risk, defined as ? 3.5% over the next 5 years per the Gail or BRCAPRO models, and/or a known BRCA1 or BRCA2 germline mutation. Results The average age at enrollment was 41.4 years and the average 5-year risk was 4.8%. Twenty-two subjects had BIRADS category 1 or 2 breast MRIs (negative or probably benign), whereas no category 4 or 5 MRIs (possibly or probably malignant) were observed. Eight subjects had BIRADS 3 results, identifying lesions that were "probably benign", yet prompting further evaluation. One of these subjects was diagnosed with a stage T1aN0M0 invasive ductal carcinoma, and later determined to be a BRCA1 mutation carrier. Conclusion Using medium-strength MRI we were able to detect 1 early breast tumor that was mammographically undetectable among 30 young high-risk women with dense breasts. These results support the concept that breast MRI can enhance surveillance for young high-risk women with dense breasts, and further suggest that a medium-strength instrument is sufficient for this application. For the first time, we demonstrate the use of quantitative breast cancer risk assessment via a combination of the Gail and BRCAPRO models for enrollment in a screening trial.

Rubinstein, Wendy S; Latimer, Jean J; Sumkin, Jules H; Huerbin, Michelle; Grant, Stephen G; Vogel, Victor G

2006-01-01

344

4 Tesla MRI for Neurodegenerative Diseases.  

National Technical Information Service (NTIS)

During the past year, nine research projects have used the 4Tesla magnet (for a total of 398 scans), and 55 developmental scans had been completed. Since the last progress report, we upgraded the shim currents which substantially improved the quality of i...

M. W. Weiner

2005-01-01

345

Crustal Magnetic Fields of Terrestrial Planets  

Microsoft Academic Search

Magnetic field measurements are very valuable, as they provide constraints on the interior of the telluric planets and Moon.\\u000a The Earth possesses a planetary scale magnetic field, generated in the conductive and convective outer core. This global magnetic\\u000a field is superimposed on the magnetic field generated by the rocks of the crust, of induced (i.e. aligned on the current main

Benoit Langlais; Vincent Lesur; Michael E. Purucker; Jack E. P. Connerney; Mioara Mandea

2010-01-01

346

Magnetic holes in the solar wind. [(interplanetary magnetic fields)  

NASA Technical Reports Server (NTRS)

An analysis is presented of high resolution interplanetary magnetic field measurements from the magnetometer on Explorer 43 which showed that low magnetic field intensities in the solar wind at 1 AU occur as distinct depressions or 'holes'. These magnetic holes are new kinetic-scale phenomena, having a characteristic dimension on the order of 20,000 km. They occurred at a rate of 1.5/day in the 18-day time span (March 18 to April 6, 1971) that was analyzed. Most of the magnetic holes are characterized by both a depression in the absolute value of the magnetic field, and a change in the magnetic field direction; some of these are possibly the result of magnetic merging. However, in other cases the magnetic field direction does not change; such holes are not due to magnetic merging, but might be a diamagnetic effect due to localized plasma inhomogeneities.

Turner, J. M.; Burlaga, L. F.; Ness, N. F.; Lemaire, J. F.

1976-01-01

347

Magnetization, Low Field Instability and Quench of RHQT Strands  

Microsoft Academic Search

Since 2005, we made and tested three RHQT Nb3Al strands, one with Nb matrix and two with Ta matrix, which are fully stabilized with Cu electroplating. We observed anomalously large magnetization curves extending beyond 1 to 1.5 Tesla with the F1 Nb matrix strand at 4.2 K, when we measured its magnetization with a balanced coil magnetometer. This problem was

Ryuji Yamada; Masayoshi Wake; Akihiro Kikuchi; Vesselin Velev

2009-01-01

348

Swarm: ESA's Magnetic Field Mission  

NASA Astrophysics Data System (ADS)

Swarm is the fifth Earth Explorer mission in ESA’s Living Planet Programme. The objective of the Swarm mission is to provide the best ever survey of the geomagnetic field and its temporal evolution. The Mission shall deliver data that allow access to new insights into the Earth system by improving our understanding of the Earth’s interior and near-Earth electro-magnetic environment. After release from a single launcher, a side-by-side flying slowly decaying lower pair of satellites will be released at an initial altitude of about 490 km together with a third satellite that will be lifted to 530 km to complete the Swarm constellation. High-precision and high-resolution measurements of the strength, direction and variation of the magnetic field, complemented by precise navigation, accelerometer and electric field measurements, will provide the observations that are required to separate and model various sources of the geomagnetic field and near-Earth current systems. The mission aims to provide a unique view into Earth core dynamics, mantle conductivity, crustal magnetisation, ionospheric and magnetospheric current systems and upper atmosphere dynamics - ranging from understanding the geodynamo to contributing to space weather. The scientific objectives and results from recent scientific studies will be presented. In addition the current status of the project, which is presently in the development phase, will be addressed. The mission is scheduled for launch in 2012.

Haagmans, R.; Menard, Y.; Floberghagen, R.; Plank, G.; Drinkwater, M. R.

2010-12-01

349

Magnetic field sensors using GMR multilayer  

Microsoft Academic Search

Wheatstone bridge magnetic field sensors using giant magnetoresistive ratio (GMR) multilayers were designed, fabricated, and evaluated. The GMR ranged from 10% to 20% with saturation fields of 60 Oe to 300 Oe. The multilater resistances decreased linearly with magnetic field and showed little hysteresis. In one sensor configuration, a permanent magnet bias was placed between two pairs of magnetoresistors, each

J. Daughton; J. Brown; E. Chen; R. Beech; A. Pohm; W. Kude

1994-01-01

350

The measurement of solar magnetic fields  

Microsoft Academic Search

Methods for studying solar magnetic fields are examined, taking into account Zeeman and Hanle effects, radio observations, the influence of magnetic fields in solar structures, theoretical extrapolations of photospheric measurements, in situ measurements in the solar-wind region, and meteorite records of the primordial solar magnetic field. Instrumental techniques for optical polarization measurements are considered and an interpretation of optical polarization

J. O. Stenflo

1978-01-01

351

Magnetic field navigation in an indoor environment  

Microsoft Academic Search

This paper describes a method that has been developed to aid an inertial navigation system when GNSS signals are not available, by taking advantage of the uniqueness of magnetic field variations. Most indoor environments have many different features (ferrous structural materials or contents, electrical currents, etc.) which perturb the Earths natural magnetic field. The variations in the magnetic field in

William Storms; Jeremiah Shockley; John Raquet

2010-01-01

352

PLASMA CONFINEMENT USING ROTATING MAGNETIC FIELDS  

Microsoft Academic Search

An investigation was made of the current distribution set up by a ; magnetic field rotating about the axis of a cylindrical plasma. If the plasma ; resistivity was sufficiently small electrons rotated with the magnetic field ; producing a steady azimuthal current. In conjunction with an externally applied ; axial magnetic field such a system can be used to

H. Blevin; P. C. Thonemann

1961-01-01

353

Magnetic field quality analysis using ANSYS.  

National Technical Information Service (NTIS)

The design of superconducting magnets for particles accelerators requires a high quality of the magnetic field. This paper presents an ANSYS 4.4A Post 1 macro that computes the field quality performing a Fourier analysis of the magnetic field. The results...

D. Dell'Orco Y. Chen

1991-01-01

354

Magnetic field effect for cellulose nanofiber alignment  

Microsoft Academic Search

Regenerated cellulose formed into cellulose nanofibers under strong magnetic field and aligned perpendicularly to the magnetic field. Well-aligned microfibrils were found as the exposure time of the magnetic field increased. Better alignment and more crystalline structure of the cellulose resulted in the increased decomposition temperature of the material. X-ray crystallograms showed that crystallinity index of the cellulose increased as the

Jaehwan Kim; Yi Chen; Kwang-Sun Kang; Young-Bin Park; Mark Schwartz

2008-01-01

355

An ancient lunar magnetic dipole field  

Microsoft Academic Search

Theories giving the source of the previously hypothesized ancient strong lunar magnetic field and reasons for its disappearance are presented. It is suggested that since it was demonstrated that the moon possessed a small iron core, a dynamo process within this core may have accounted for the field. The disappearance of this magnetizing field can be explained; either the magnetic

S. K. Runcorn

1975-01-01

356

Magnetic Field Homogenization of the Human Prefrontal Cortex with a Set of Localized Electrical Coils  

PubMed Central

The prefrontal cortex is a common target brain structure in psychiatry and neuroscience due to its role in working memory and cognitive control. Large differences in magnetic susceptibility between the air-filled sinuses and the tissue/bone in the frontal part of the human head cause a strong and highly localized magnetic field focus in the prefrontal cortex. As a result, image distortion and signal dropout are observed in MR imaging. A set of external, electrical coils is presented that provides localized and high amplitude shim fields in the prefrontal cortex with minimum impact on the rest of the brain when combined with regular zero-to-second order spherical harmonics shimming. The experimental realization of the new shim method strongly minimized or even eliminated signal dropout in gradient-echo images acquired at settings typically used in functional magnetic resonance at 4 Tesla.

Juchem, Christoph; Nixon, Terence W.; McIntyre, Scott; Rothman, Douglas L.; de Graaf, Robin A.

2011-01-01

357

Magnetic field gradient measurement on magnetic cards using magnetic force microscopy  

NASA Astrophysics Data System (ADS)

The magnetic field gradients of magnetic stripe cards, which are developed for classifying magnetic particles used in magnetic particle inspections, have been measured using a magnetic force microscope (MFM). The magnetic force exerted on a MFM probe by the stray field emanating from the card was measured to determine the field gradients. The results are in good agreement with the field gradients estimated from the magnetizing field strengths used in the encoding process. .

Lo, C. C. H.; Leib, J.; Jiles, D. C.; Chedister, W. C.

2002-05-01

358

Magnetic field gradient measurement on magnetic cards using magnetic force microscopy  

Microsoft Academic Search

The magnetic field gradients of magnetic stripe cards, which are developed for classifying magnetic particles used in magnetic particle inspections, have been measured using a magnetic force microscope (MFM). The magnetic force exerted on a MFM probe by the stray field emanating from the card was measured to determine the field gradients. The results are in good agreement with the

C. C. H. Lo; J. Leib; D. C. Jiles; W. C. Chedister

2002-01-01

359

Magnetic Fields in Molecular Clouds  

NASA Astrophysics Data System (ADS)

Maps of far-infrared and submillimeter polarization vectors have typically been examined one-at-a-time for magnetic field structure related to processes such as gravitational collapse, differential rotation, expanding H II regions, or tidal stripping. The same maps can be used to determine angular dispersion due to turbulence in molecular clouds, where the turbulent dispersion is distinguished from dispersion due to curvature of the large-scale structure or the apparent dispersion due to measurement error. Taking into account the differences between the dispersion due to magneto-hydrodynamic waves in the arms of the Galaxy and dispersion due to turbulence in molecular clouds, one can infer field strengths in dense clouds using a method analogous to that used by Chandresekhar & Fermi to determine field strengths in the Galactic plane. With an accurate archive of flux and polarization maps one can also determine three-dimensional cloud shapes and field orientations, or look for correlations between fields in molecular clouds and fields in the surrounding medium.

Hildebrand, R. H.

2009-12-01

360

Interplanetary magnetic field data book  

NASA Technical Reports Server (NTRS)

An interplanetary magnetic field (IMF) data set is presented that is uniform with respect to inclusion of cislunar IMF data only, and which has as complete time coverage as presently possible over a full solar cycle. Macroscale phenomena in the interplanetary medium (sector structure, heliolatitude variations, solar cycle variations, etc.) and other phenomena (e.g., ground level cosmic-ray events) for which knowledge of the IMF with hourly resolution is necessary, are discussed. Listings and plots of cislunar hourly averaged IMP parameters over the period November 27, 1963, to May 17, 1974, are presented along with discussion of the mutual consistency of the IMF data used herein. The magnetic tape from which the plots and listings were generated, which is available from the National Space Science Data Center (NSSDC), is also discussed.

King, J. H.

1975-01-01

361

The Giotto magnetic field investigation  

NASA Technical Reports Server (NTRS)

The Giotto spacecraft will carry sensors for investigating the interplanetary magnetic field while en route and the interaction between the solar wind magnetoplasma and Halley's Comet neutral gas outflow during close approach. Giotto will carry an outboard biaxial fluxgate system and inboard electronics. The instrumentation draws 1.2 kW and weighs 1.31 kg. Sampling rates will be 28/sec during close encounter, covering selectable ranges from 16 nT to 65,535 nT. In-flight calibration techniques are under development to ensure magnetic cleanliness will be obtained. Measurements are also planned of the inbound bow shock, the magnetosheath and the cometary ionopause. The data will be collected as close as 1000 km from the comet surface.

Neubauer, F. M.; Musmann, G.; Acuna, M. H.; Burlaga, L. F.; Ness, N. F.; Mariani, F.; Wallis, M.; Ungstrup, E.; Schmidt, H.

1983-01-01

362

Graphene in high magnetic fields  

NASA Astrophysics Data System (ADS)

Carbon-based nano-materials, such as graphene and carbon nanotubes, represent a fascinating research area aiming at exploring their remarkable physical and electronic properties. These materials not only constitute a playground for physicists, they are also very promising for practical applications and are envisioned as elementary bricks of the future of the nano-electronics. As for graphene, its potential already lies in the domain of opto-electronics where its unique electronic and optical properties can be fully exploited. Indeed, recent technological advances have demonstrated its effectiveness in the fabrication of solar cells and ultra-fast lasers, as well as touch-screens and sensitive photo-detectors. Although the photo-voltaic technology is now dominated by silicon-based devices, the use of graphene could very well provide higher efficiency. However, before the applied research to take place, one must first demonstrates the operativeness of carbon-based nano-materials, and this is where the fundamental research comes into play. In this context, the use of magnetic field has been proven extremely useful for addressing their fundamental properties as it provides an external and adjustable parameter which drastically modifies their electronic band structure. In order to induce some significant changes, very high magnetic fields are required and can be provided using both DC and pulsed technology, depending of the experimental constraints. In this article, we review some of the challenging experiments on single nano-objects performed in high magnetic and low temperature. We shall mainly focus on the high-field magneto-optical and magneto-transport experiments which provided comprehensive understanding of the peculiar Landau level quantization of the Dirac-type charge carriers in graphene and thin graphite.

Orlita, Milan; Escoffier, Walter; Plochocka, Paulina; Raquet, Bertrand; Zeitler, Uli

2013-01-01

363

Suppression of magnetic relaxation by a transverse alternating magnetic field  

SciTech Connect

The evolution of the spatial distribution of the magnetic induction in a superconductor after the action of the alternating magnetic field perpendicular to the trapped magnetic flux has been analyzed. The observed stabilization of the magnetic induction profile is attributed to the increase in the pinning force, so that the screening current density becomes subcritical. The last statement is corroborated by direct measurements.

Voloshin, I. F.; Kalinov, A. V.; Fisher, L. M. [All-Russia Electrical Engineering Institute (Russian Federation)], E-mail: fisher@vei.ru; Yampol'skii, V. A. [National Academy of Sciences of Ukraine, Institute of Radiophysics and Electronics (Ukraine)], E-mail: yam@vk.kharkov.ua

2007-07-15

364

Magnetic field sources and their threat to magnetic media  

NASA Technical Reports Server (NTRS)

Magnetic storage media (tapes, disks, cards, etc.) may be damaged by external magnetic fields. The potential for such damage has been researched, but no objective standard exists for the protection of such media. This paper summarizes a magnetic storage facility standard, Publication 933, that ensures magnetic protection of data storage media.

Jewell, Steve

1993-01-01

365

Magnetic nanostructures as amplifiers of transverse fields in magnetic resonance.  

PubMed

We introduce the concept of amplifying the transverse magnetic fields produced and/or detected with inductive coils in magnetic resonance settings by using the reversible transverse susceptibility properties of magnetic nanostructures. First, we describe the theoretical formalism of magnetic flux amplification through the coil in the presence of a large perpendicular DC magnetic field (typical of magnetic resonance systems) achieved through the singularity in the reversible transverse susceptibility in anisotropic single domain magnetic nanoparticles. We experimentally demonstrate the concept of transverse magnetic flux amplification in an inductive coil system using oriented nanoparticles with uni-axial magnetic anisotropy. We also propose a composite ferromagnetic/anti-ferromagnetic core/shell nanostructure system with uni-directional magnetic anisotropy that, in principle, provides maximal transverse magnetic flux amplification. PMID:16039099

Barbic, Mladen; Scherer, Axel

2005-09-01

366

Thinned fiber Bragg grating magnetic field sensor with magnetic fluid  

Microsoft Academic Search

The refractive index of magnetic fluid may be changed by external magnetic field. Therefore, through measuring its refractive index, the intensity of the magnetic field can be obtained. Fiber Bragg grating (FBG) is sensitive to the refractive index surrounding its cladding when the diameter of cladding is reduced to a certain degree. In order to prove the sensitivity of the

Ciming Zhou; Li Ding; Dongli Wang; Yaqi Kuang; Desheng Jiang

2011-01-01

367

3 Tesla magnetic resonance imaging of the prostate with combined pelvic phased-array and endorectal coils  

Microsoft Academic Search

Rationale and objectivesHigh-resolution magnetic resonance imaging of the prostate at 1.5T has gained acceptance for pretherapeutic staging of prostate cancer. The aim of this study was to evaluate the potential clinical utility of combined pelvic phased-array and endorectal coils at 3T.

B. Nicolas Bloch; Neil M Rofsky; Ronaldo H Baroni; Robert P Marquis; Ivan Pedrosa; Robert E Lenkinski

2004-01-01

368

Magnetic field in a turbulent galactic disk  

Microsoft Academic Search

A simple kinematic model has been applied to simulate the evolution of the interstellar magnetic field permanently twisted by turbulent gas motions accompanied by effects of the field diffusion. The magnetic field was found to develop well-ordered twisted structures over the whole gas parcel analyzed. This field configuration has a preferred sense of twisting dependent on the helicity of the

Katarzyna Otmianowska-Mazur; Marek Urbanik; Artur Terech

1992-01-01

369

Quantitative model of the magnetospheric magnetic field  

Microsoft Academic Search

Quantitative representations of the magnetic fields associated with the magnetopause currents and the distributed currents (tail and quiet time ring currents) have been developed. These fields are used together with a dipole representation of the main field of the earth to model the total vector magnetospheric magnetic field. The model is based on quiet time data averaged over all 'tilt

W. P. Olson; K. A. Pfitzer

1974-01-01

370

Spin dephasing in a magnetic dipole field.  

PubMed

Transverse relaxation by dephasing in an inhomogeneous field is a general mechanism in physics, for example, in semiconductor physics, muon spectroscopy, or nuclear magnetic resonance. In magnetic resonance imaging the transverse relaxation provides information on the properties of several biological tissues. Since the dipole field is the most important part of the multipole expansion of the local inhomogeneous field, dephasing in a dipole field is highly important in relaxation theory. However, there have been no analytical solutions which describe the dephasing in a magnetic dipole field. In this work we give a complete analytical solution for the dephasing in a magnetic dipole field which is valid over the whole dynamic range. PMID:23004789

Ziener, C H; Kampf, T; Reents, G; Schlemmer, H-P; Bauer, W R

2012-05-01

371

Tesla's contribution to radiowave propagation  

Microsoft Academic Search

We review Nikola Tesla's contribution to radiowave propagation and wireless power transmission. Tesla's patents, published and unpublished notes about radiowave propagation and wireless power transmission are less known, and if known to some extent, they are usually wrongly interpreted

Aleksandar Marincic; Djuradj Budimir

2001-01-01

372

Magnetic field effects on microwave absorbing materials  

NASA Technical Reports Server (NTRS)

The objective of this program was to gather information to formulate a microwave absorber that can work in the presence of strong constant direct current (DC) magnetic fields. The program was conducted in four steps. The first step was to investigate the electrical and magnetic properties of magnetic and ferrite microwave absorbers in the presence of strong magnetic fields. This included both experimental measurements and a literature survey of properties that may be applicable to finding an appropriate absorbing material. The second step was to identify those material properties that will produce desirable absorptive properties in the presence of intense magnetic fields and determine the range of magnetic field in which the absorbers remain effective. The third step was to establish ferrite absorber designs that will produce low reflection and adequate absorption in the presence of intense inhomogeneous static magnetic fields. The fourth and final step was to prepare and test samples of such magnetic microwave absorbers if such designs seem practical.

Goldberg, Ira; Hollingsworth, Charles S.; Mckinney, Ted M.

1991-01-01

373

The Wind Magnetic Field Investigation  

NASA Astrophysics Data System (ADS)

The magnetic field experiment on WIND will provide data for studies of a broad range of scales of structures and fluctuation characteristics of the interplanetary magnetic field throughout the mission, and, where appropriate, relate them to the statics and dynamics of the magnetosphere. The basic instrument of the Magnetic Field Investigation (MFI) is a boom-mounted dual triaxial fluxgate magnetometer and associated electronics. The dual configuration provides redundancy and also permits accurate removal of the dipolar portion of the spacecraft magnetic field. The instrument provides (1) near real-time data at nominally one vector per 92 s as key parameter data for broad dissemination, (2) rapid data at 10.9 vectors s-1 for standard analysis, and (3) occasionally, snapshot (SS) memory data and Fast Fourier Transform data (FFT), both based on 44 vectors s-1. These measurements will be precise (0.025%), accurate, ultra-sensitive (0.008 nT/step quantization), and where the sensor noise level is <0.006 nT r.m.s. for 0 10 Hz. The digital processing unit utilizes a 12-bit microprocessor controlled analogue-to-digital converter. The instrument features a very wide dynamic range of measurement capability, from ±4 nT up to ±65 536 nT per axis in eight discrete ranges. (The upper range permits complete testing in the Earth's field.) In the FTT mode power spectral density elements are transmitted to the ground as fast as once every 23 s (high rate), and 2.7 min of SS memory time series data, triggered automatically by pre-set command, requires typically about 5.1 hours for transmission. Standard data products are expected to be the following vector field averages: 0.0227-s (detail data from SS), 0.092 s (‘detail’ in standard mode), 3 s, 1 min, and 1 hour, in both GSE and GSM coordinates, as well as the FFT spectral elements. As has been our team's tradition, high instrument reliability is obtained by the use of fully redundant systems and extremely conservative designs. We plan studies of the solar wind: (1) as a collisionless plasma laboratory, at all time scales, macro, meso and micro, but concentrating on the kinetic scale, the highest time resolution of the instrument (=0.022 s), (2) as a consequence of solar energy and mass output, (3) as an external source of plasma that can couple mass, momentum, and energy to the Earth's magnetosphere, and (4) as it is modified as a consequence of its imbedded field interacting with the moon. Since the GEOTAIL Inboard Magnetometer (GIM), which is similar to the MFI instrument, was developed by members of our team, we provide a brief discussion of GIM related science objectives, along with MFI related science goals.

Lepping, R. P.; Ac?na, M. H.; Burlaga, L. F.; Farrell, W. M.; Slavin, J. A.; Schatten, K. H.; Mariani, F.; Ness, N. F.; Neubauer, F. M.; Whang, Y. C.; Byrnes, J. B.; Kennon, R. S.; Panetta, P. V.; Scheifele, J.; Worley, E. M.

1995-02-01

374

Topological Description of Coronal Magnetic Fields.  

National Technical Information Service (NTIS)

Determining the structure and behavior of solar coronal magnetic fields is a central problem in solar physics. At the photosphere, the field is believed to be strongly localized into discrete flux tubes. After providing a rigorous definition of field topo...

M. A. Berger

1986-01-01

375

Structured electrodeposition in magnetic gradient fields  

NASA Astrophysics Data System (ADS)

Electrodeposition in superimposed magnetic gradient fields is a new and promising method of structuring metal deposits while avoiding masking techniques. The magnetic properties of the ions involved, their concentrations, the electrochemical deposition parameters, and the amplitude of the applied magnetic gradient field determine the structure generated. This structure can be thicker in regions of high magnetic field gradients. It can also be free-standing or inversely structured. The complex mechanism of structured electrodeposition of metallic layers in superimposed magnetic gradient fields was studied by different experimental methods, by analytical methods and by numerical simulation and will be discussed comprehensively.

Uhlemann, Margitta; Tschulik, Kristina; Gebert, Annett; Mutschke, Gerd; Fröhlich, Jochen; Bund, Andreas; Yang, Xuegeng; Eckert, Kerstin

2013-03-01

376

Deformation of Water by a Magnetic Field  

ERIC Educational Resources Information Center

After the discovery that superconducting magnets could levitate diamagnetic objects, researchers became interested in measuring the repulsion of diamagnetic fluids in strong magnetic fields, which was given the name "The Moses Effect." Both for the levitation experiments and the quantitative studies on liquids, the large magnetic fields necessary…

Chen, Zijun; Dahlberg, E. Dan

2011-01-01

377

Anhysteretic Remanent Magnetization in Small Steady Fields  

Microsoft Academic Search

The phenomenon called anhysteretic remanent magnetization, ARM, has been known for a long time, but it has received relatively little attention. A knowledge of this type of magnetization is required in proper application of alternating field demagnetization tech- niques to rock magnetism problems. Over a wide range of low values of the steady field Ho, the ARM intensity is a

Bob J. Patton; John L. Fitch

1962-01-01

378

On Magnetic Field Generation Mechanisms in Astrophysics  

Microsoft Academic Search

Magnetic chemically peculiar stars (CP stars) are characterized by a strong magnetic field, peculiar chemical composition and slow rotation. Since the origin and evolution of CP stars may be responsible for such unusual features, understanding the mechanisms of generation of the magnetic field is one of the ways to learn more about the CP star characteristics. At present there are

O. G. Cherny

2011-01-01

379

Orienting Paramecium with intense static magnetic fields  

Microsoft Academic Search

Recent experiments on cell division suggest the application of intense static magnetic fields as a novel tool for the manipulation of biological systems [1]. The magnetic field appears to couple to the intrinsic anisotropies in the diamagnetic components of the cells. Here, we present measurements of the intrinsic average diamagnetic anisotropy of the whole single celled ciliate, Paramecium Caudatum. Magnetic

James M. Valles Jr.; Karine Guevorkian; Carl Quindel

2004-01-01

380

Baking a magnetic-field display  

NASA Astrophysics Data System (ADS)

Copy machine developer powder is an alternative for creating permanent displays of magnetic fields. A thin layer of developer powder on a sheet of paper placed over a magnet can be baked in the oven, producing a lasting image of a magnetic field.

Cavanaugh, Terence; Cavanaugh, Catherine

1998-02-01

381

The structure of helical interplanetary magnetic fields  

NASA Technical Reports Server (NTRS)

The interplanetary magnetic field is known to be highly helical. Although the detailed spatial structure of the fields has yet to be elucidated, the helicity spectrum has been conjectured to result from a random walk in the direction of a constant magnitude magnetic field vector. A model using three-dimensional fluctuations with variations in B is demonstrated giving a good fit to the helicity spectrum as well as to other properties of the interplanetary magnetic field.

Goldstein, M. L.; Roberts, D. A.; Fitch, C. A.

1991-01-01

382

Analysis of magnetic field levels at KSC  

NASA Technical Reports Server (NTRS)

The scope of this work is to evaluate the magnetic field levels of distribution systems and other equipment at Kennedy Space Center (KSC). Magnetic fields levels in several operational areas and various facilities are investigated. Three dimensional mappings and contour are provided along with the measured data. Furthermore, the portion of magnetic fields generated by the 60 Hz fundamental frequency and the portion generated by harmonics are examined. Finally, possible mitigation techniques for attenuating fields from electric panels are discussed.

Christodoulou, Christos G.

1994-01-01

383

Progress in HTS Trapped Field Magnets: J(sub c), Area, and Applications  

NASA Technical Reports Server (NTRS)

Progress in trapped field magnets is reported. Single YBCO grains with diameters of 2 cm are made in production quantities, while 3 cm, 4 1/2 cm and 6 cm diameters are being explored. For single grain tiles: J(sub c) - 10,000 A/sq cm for melt textured grains; J(sub c) - 40,000 A/sq cm for light ion irradiation; and J(sub c) - 85,000 A/J(sub c) for heavy ion irradiation. Using 2 cm diameter tiles bombarded by light ions, we have fabricated a mini-magnet which trapped 2.25 Tesla at 77K, and 5.3 Tesla at 65K. A previous generation of tiles, 1 cm x 1 cm, was used to trap 7.0 Tesla at 55K. Unirradiated 2.0 cm tiles were used to provide 8 magnets for an axial gap generator, in a collaborative experiment with Emerson Electric Co. This generator delivered 100 Watts to a resistive load, at 2265 rpm. In this experiment, activation of the TFMs was accomplished by a current pulse of 15 ms duration. Tiles have also been studied for application as a bumper-tether system for the soft docking of spacecraft. A method for optimizing tether forces, and mechanisms of energy dissipation are discussed. A bus bar was constructed by welding three crystals while melt-texturing, such that their a,b planes were parallel and interleaved. The bus bar, of area approx. 2 sq cm, carried a transport current of 1000 amps, the limit of the testing equipment available.

Weinstein, Roy; Ren, Yanru; Liu, Jian-Xiong; Sawh, Ravi; Parks, Drew; Foster, Charles; Obot, Victor; Arndt, G. Dickey; Crapo, Alan

1995-01-01

384

Progress in HTS trapped field magnets: J(sub c), area, and applications  

NASA Technical Reports Server (NTRS)

Progress in trapped field magnets is reported. Single YBCO grains with diameters of 2 cm are made in production quantities, while 3 cm, 4 1/2 cm and 6 cm diameters are being explored. For single grain tiles: J(sub c) is approximately 10,000 A/cm(exp 2) for melt textured grains; J(sub c) is approximately 40,000 A/cm2 for light ion irradiation; and J(sub c) is approximately 85,000 A/cm(exp 2) for heavy ion irradiation. Using 2 cm diameter tiles bombarded by light ions, we have fabricated a mini-magnet which trapped 2.25 Tesla at 77K, and 5.3 Tesla at 65K. A previous generation of tiles, 1 cm x 1 cm, was used to trap 7.0 Tesla at 55K. Unirradiated 2.0 cm tiles were used to provide 8 magnets for an axial gap generator, in a collaborative experiment with Emerson Electric Co. This generator delivered 100 Watts to a resistive load, at 2265 rpm. In this experiment activation of the TFMs was accomplished by a current pulse of 15 ms duration. Tiles have also been studied for application as a bumper-tether system for the soft docking of spacecraft. A method for optimizing tether forces, and mechanisms of energy dissipation are discussed. A bus bar was constructed by welding three crystals while melt-texturing, such that their a,b planes were parallel and interleaved. The bus bar, an area of approximately 2 cm(exp 2), carried a transport current of 1000 amps, the limit of the testing equipment available.

Weinstein, Roy; Ren, Yanru; Liu, Jianxiong; Sawh, Ravi; Parks, Drew; Foster, Charles; Obot, Victor; Arndt, G. Dickey; Crapo, Alan

1995-01-01

385

Rotating magnetic beacons magnetic field strength size in SAGD  

Microsoft Academic Search

Rotation magnetic beacons magnetic field strength is very important to drill parallel horizontal twin wells in steam assisted\\u000a gravity drainage (SAGD). This paper analyzes a small magnet with a diameter of 25.4 mm. At each end, there is a length of\\u000a 12.6 mm with permanent magnet, and in the middle, there is a length of 78mm with magnetic materials. The

Bing Tu; Desheng Li; Enhuai Lin; Bin Luo; Jian He; Lezhi Ye; Jiliang Liu; Yuezhong Wang

2010-01-01

386

T2 Relaxometry Using 3.0-Tesla Magnetic Resonance Imaging of the Brain in Early- and Late-Onset Restless Legs Syndrome  

PubMed Central

Background and Purpose Previous T2 relaxometry studies have provided evidence for regional brain iron deficiency in patients with restless legs syndrome (RLS). Measurement of the iron content in several brain regions, and in particular the substantia nigra (SN), in early- and late-onset RLS patients using T2 relaxometry have yielded inconsistent results. In this study the regional iron content was assessed in patients with early- and late-onset RLS using magnetic resonance imaging (MRI), and compared the results with those in controls. Methods Thirty-seven patients with idiopathic RLS (20 with early onset and 17 with late onset) and 40 control subjects were studied using a 3.0-tesla MRI with a gradient-echo sampling of free induction decay and echo pulse sequence. The regions of interest in the brain were measured independently by two trained analysts using software known as medical image processing, analysis, and visualization. The results were compared and a correlation analysis was conducted to investigate which brain areas were related to RLS clinical variables. Results The iron index in the SN was significantly lower in patients with late-onset RLS than in controls (p=0.034), while in patients with early-onset RLS there was no significant difference. There was no significant correlation between the SN iron index of the late-onset RLS group and clinical variables such as disease severity. Conclusions Late-onset RLS is associated with decreased iron content in the SN. This finding supports the hypothesis that regional brain iron deficiency plays a role in the pathophysiology of late-onset RLS.

Moon, Hye-Jin; Chang, Yongmin; Lee, Yeong Seon; Song, Hee Jin; Chang, Hyuk Won; Ku, Jeonghun

2014-01-01

387

Diagnostic accuracy of a short-duration 3 Tesla magnetic resonance protocol for diagnosing stifle joint lesions in dogs with non-traumatic cranial cruciate ligament rupture  

PubMed Central

Background Magnetic resonance (MR) imaging is the preferred diagnostic tool to evaluate internal disorders of many joints in humans; however, the usefulness of MR imaging in the context of osteoarthritis, and joint disease in general, has yet to be characterized in veterinary medicine. The objective of this study was to assess the diagnostic accuracy of short-duration 3 Tesla MR imaging for the evaluation of cranial and caudal cruciate ligament, meniscal and cartilage damage, as well as the degree of osteoarthritis, in dogs affected by non-traumatic, naturally-occurring cranial cruciate ligament rupture (CCLR). Diagnoses made from MR images were compared to those made during surgical exploration. Twenty-one client-owned dogs were included in this study, and one experienced evaluator assessed all images. Results All cranial cruciate ligaments were correctly identified as ruptured. With one exception, all caudal cruciate ligaments were correctly identified as intact. High sensitivities and specificities were obtained when diagnosing meniscal rupture. MR images revealed additional subclinical lesions in both the cranial and caudal cruciate ligaments and in the menisci. There was a “clear” statistical (kappa) agreement between the MR and the surgical findings for both cartilage damage and degree of osteoarthritis. However, the large 95% confidence intervals indicated that evaluation of cartilage damage and of degree of osteoarthritis is not clinically satisfactory. Conclusions The presence of cruciate ligament damage and meniscal tears could be accurately assessed using the MR images obtained with our protocol. However, in the case of meniscal evaluation, occasional misdiagnosis did occur. The presence of cartilage damage and the degree of osteoarthritis could not be properly evaluated.

2013-01-01

388

The Effects of Voxel Localization and Time of Echo on the Diagnostic Accuracy of Cystic Brain Tumors in 3 Tesla Magnetic Resonance Spectroscopy  

PubMed Central

Background Although magnetic resonance spectroscopy (MRS) has been shown as an effective diagnostic tool in distinguishing inflammation from neoplasm in cystic brain lesions, the optimum approach in selecting the portions of lesions in MRS and the possible effects of different times of echoes (TEs) remains unknown. Objectives To determine the most effective TE in diagnosing neoplastic lesions based on detecting choline (Cho), N acetyl aspartate (NAA) and creatinine (Cr). Moreover, the role of voxel localization on the diagnosis of the neoplastic nature of the lesions is assessed through comparing the abovementioned metabolite ratios in the rim and center of each lesion with the same TE. Patients and Methods In 16 patients with brain cystic tumors, MRS was performed at TEs of 30, 135 and 270 ms for detection of Cho, NAA and Cr metabolites using a 3 tesla MRI unit. The percentage of analyzed ratios greater than a cut-off point of 1.3 for Cho/Cr and 1.6 for Cho/NAA were calculated. Results Cho/Cr and Cho/NAA ratio means at all TEs were more at the central area in comparison with the periphery, although none of the differences were statistically significant. There was no statistically significant difference among the compared TEs. The percentages of ratios above the cut-off point at all TEs were more in the rim compared to the center and in the union of both compared to the rim or center. All the patients had at least one voxel with a Cho/Cr ratio of more than 1.3 when the voxel was chosen according to the hotspots shown in the chemical shift imaging map, regardless of their location at all examined TEs. Conclusions Selection of voxels with the guide of chemical shift imaging map yields to 100% diagnostic sensitivity. If not accessible, the use of the union of peripheral and central voxels enhances the sensitivity when compared to usage of peripheral or central voxels solely.

Rezvanizadeh, Alireza; Firouznia, Kavous; Salehi-Sadaghiani, Mohammad; Mohseni, Meisam; Gharaei, Dona; Ghanaati, Hossein; Saligheh Rad, Hamidreza; Masoudnia, Majid

2012-01-01

389

Magnetizing technique for permanent magnets by intense static fields generated by HTS bulk magnets: Numerical Analysis  

NASA Astrophysics Data System (ADS)

A demagnetized Nd-Fe-B permanent magnet was scanned in the strong magnetic field space just above the magnetic pole containing a HTS bulk magnet which generates the magnetic field 3.4 T. The magnet sample was subsequently found to be fully magnetized in the open space of the static magnetic fields. The finite element method was carried out for the static field magnetization of a permanent magnet using a HTS bulk magnet. Previously, our research group experimentally demonstrated the possibility of full magnetization of rare earth permanent magnets with high-performance magnetic properties with use of the static field of HTS bulk magnets. In the present study, however, we succeeded for the first time in visualizing the behavior of the magnetizing field of the bulk magnet during the magnetization process and the shape of the magnetic field inside the body being magnetized. By applying this kind of numerical analysis to the magnetization for planned motor rotors which incorporate rare-earth permanent magnets, we hope to study the fully magnetized regions for the new magnetizing method using bulk magnets and to give motor designing a high degree of freedom.

N. Kawasaki; Oka, T.; Fukui, S.; Ogawa, J.; Sato, T.; Terasawa, T.; Itoh, Y.

390

Effects of magnetic fields on mosquitoes.  

PubMed

Phylogenetically diverse organisms, including some insects, are able to detect and respond to magnetic fields comparable to the Earth's magnetic field. Because of their tremendous importance to public health, mosquitoes were tested for the presence of remanent ferromagnetic material indicative of a biological compass and also tested for behavioral responses to magnetic fields. Using a superconducting quantum interferometry device, we found that significant remnant was probably due to attraction of ferromagnetic dust onto the surface of live or dead mosquitoes. Most mosquitoes placed in a 1.0-gauss, uniform magnetic field moved until they were oriented parallel to the field. Two of 3 species of mosquitoes tested took fewer blood meals in a rotating magnetic field than in the Earth's normal magnetic field. PMID:10901636

Strickman, D; Timberlake, B; Estrada-Franco, J; Weissman, M; Fenimore, P W; Novak, R J

2000-06-01

391

Boston University Physics Applets: Magnetic Field Demonstration  

NSDL National Science Digital Library

This web page is an interactive physics simulation that explores magnetic fields. The user can add currents coming into or out of a simulated grid, and see the fields created. There is also a selection of pre-created fields, including bar magnets, loops, opposing magnets, and coils in uniform fields. Double-clicking on any point displays the full loop created by the magnetic field. This item is part of a larger collection of introductory physics simulations developed by the author. This is part of a collection of similar simulation-based student activities.

Duffy, Andrew

2008-08-23

392

Magnetic fields in the early Universe  

NASA Astrophysics Data System (ADS)

We give a pedagogical introduction to two aspects of magnetic fields in the early Universe. We first focus on how to formulate electrodynamics in curved space time, defining appropriate magnetic and electric fields and writing Maxwell equations in terms of these fields. We then specialize to the case of magnetohydrodynamics in the expanding Universe. We emphasize the usefulness of tetrads in this context. We then review the generation of magnetic fields during the inflationary era, deriving in detail the predicted magnetic and electric spectra for some models. We discuss potential problems arising from back reaction effects and from the large variation of the coupling constants required for such field generation.

Subramanian, K.

2010-01-01

393

Near-Field Magnetic Dipole Moment Analysis.  

National Technical Information Service (NTIS)

This paper describes the data analysis technique used for magnetic testing at the NASA Goddard Space Flight Center (GSFC). Excellent results have been obtained using this technique to convert a spacecraft s measured magnetic field data into its respective...

P. K. Harris

2003-01-01

394

Bipolar pulse field for magnetic refrigeration  

DOEpatents

A magnetic refrigeration apparatus includes first and second steady state magnets, each having a field of substantially equal strength and opposite polarity, first and second bodies made of magnetocaloric material disposed respectively in the influence of the fields of the first and second steady state magnets, and a pulsed magnet, concentric with the first and second steady state magnets, and having a field which cycles between the fields of the first and second steady state magnets, thereby cyclically magnetizing and demagnetizing and thus heating and cooling the first and second bodies. Heat exchange apparatus of suitable design can be used to expose a working fluid to the first and second bodies of magnetocaloric material. A controller is provided to synchronize the flow of working fluid with the changing states of magnetization of the first and second bodies. 2 figs.

Lubell, M.S.

1994-10-25

395

MAGNETIC BRAIDING AND PARALLEL ELECTRIC FIELDS  

SciTech Connect

The braiding of the solar coronal magnetic field via photospheric motions-with subsequent relaxation and magnetic reconnection-is one of the most widely debated ideas of solar physics. We readdress the theory in light of developments in three-dimensional magnetic reconnection theory. It is known that the integrated parallel electric field along field lines is the key quantity determining the rate of reconnection, in contrast with the two-dimensional case where the electric field itself is the important quantity. We demonstrate that this difference becomes crucial for sufficiently complex magnetic field structures. A numerical method is used to relax a braided magnetic field toward an ideal force-free equilibrium; the field is found to remain smooth throughout the relaxation, with only large-scale current structures. However, a highly filamentary integrated parallel current structure with extremely short length-scales is found in the field, with the associated gradients intensifying during the relaxation process. An analytical model is developed to show that, in a coronal situation, the length scales associated with the integrated parallel current structures will rapidly decrease with increasing complexity, or degree of braiding, of the magnetic field. Analysis shows the decrease in these length scales will, for any finite resistivity, eventually become inconsistent with the stability of the coronal field. Thus the inevitable consequence of the magnetic braiding process is a loss of equilibrium of the magnetic field, probably via magnetic reconnection events.

Wilmot-Smith, A. L.; Hornig, G.; Pontin, D. I. [Division of Mathematics, University of Dundee, Dundee DD1 4HN (United Kingdom)], E-mail: antonia@maths.dundee.ac.uk

2009-05-10

396

Exploring Magnetic Fields in Your Environment  

NSDL National Science Digital Library

This is a lesson about measuring magnetic field directions of Earth and in the environment. First, learners go outside, far away from buildings, power lines, or anything electrical or metal, and use compasses to identify magnetic North. Next, they use the compasses to probe whether there are any sources of magnetic fields in the local environment, including around electronic equipment such as a CD player and speakers. This is the first lesson in the second session of the Exploring Magnetism teacher guide.

397

Horizontal magnetic fields in the solar photosphere  

Microsoft Academic Search

Two-dimensional simulations of time-dependent solar magnetogranulation are used to analyze the horizontal magnetic fields and the response of the synthesized Stokes profiles of the IR FeI lambda1564.85 nm line to the magnetic fields. The 1.5-h series of MHD models used for the analyses reproduces a region of the magnetic network in the photosphere with an unsigned magnetic flux density of

V. A. Sheminova

2009-01-01

398

Horizontal magnetic fields in the solar photosphere  

Microsoft Academic Search

Two-dimensional simulations of time-dependent solar magnetogranulation are used to analyze the horizontal magnetic fields\\u000a and the response of the synthesized Stokes profiles of the IR FeI ?1564.85 nm line to the magnetic fields. The 1.5-h series of MHD models used for the analyses reproduces a region of the magnetic\\u000a network in the photosphere with an unsigned magnetic flux density of

V. A. Sheminova

2009-01-01

399

Fiber Bragg Grating Magnetic Field Sensor  

Microsoft Academic Search

In this paper we demonstrate experimentally a magnetic field sensor using a fiber Bragg grating. The shift in the Bragg condition as a result of strain applied on the fiber mounted on a nickel base by the magnetic field gives an indirect measure of the field. The proposed method overcomes the need for long fiber lengths required in methods such

K. V. Madhav; K. Ravi Kumar; T. Srinivas; S. Asokan

2006-01-01

400

The National High Magnetic Field Laboratory  

Microsoft Academic Search

The National High Magnetic Field Laboratory (NHMFL) was established in 1990, on the basis of a collaboration between Florida State University (FSU), the University of Florida (UF) and Los Alamos National Laboratory (LANL). The main campus for the NHMFL is located in Tallahassee, Florida, and its general purpose DC magnetic field facility is described in this paper. The pulsed field

B. L. Brandt; S. Hannahs; H. J. Schneider-Muntau; G. Boebinger; N. S. Sullivan

2001-01-01

401

Representation of magnetic fields in space  

NASA Technical Reports Server (NTRS)

Several methods by which a magnetic field in space can be represented are reviewed with particular attention to problems of the observed geomagnetic field. Time dependence is assumed to be negligible, and five main classes of representation are described by vector potential, scalar potential, orthogonal vectors, Euler potentials, and expanded magnetic field.

Stern, D. P.

1975-01-01

402

Primordial magnetic fields from superconducting cosmic strings  

Microsoft Academic Search

This paper explores the possibility of generation of a primordial magnetic field by a network of charged-current carrying cosmic strings. The field is created by vorticity, generated in the primordial plasma due to the strings' motion and gravitational pull. In the case of superconducting strings formed at the breaking of grand unification, it is found that strong magnetic fields of

Konstantinos Dimopoulos

1998-01-01

403

DC-based magnetic field controller  

DOEpatents

A magnetic field controller for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage.

Kotter, Dale K. (Shelley, ID); Rankin, Richard A. (Ammon, ID); Morgan, John P,. (Idaho Falls, ID)

1994-01-01

404

Manipulating Cells with Static Magnetic Fields  

Microsoft Academic Search

We review our investigations of the use of static magnetic fields, B, for manipulating cells and cellular processes. We describe how B fields modify the cell division pattern of frog embryos and consequently can be used to probe the pattern determinants. We also observe that magnetic fields modify the swimming behavior of Paramecium Caudatum. We describe these modifications and their

J. M. Valles; K. Guevorkian

2005-01-01

405

Radiation-Induced Microbleeds after Cranial Irradiation: Evaluation by Phase-Sensitive Magnetic Resonance Imaging with 3.0 Tesla  

PubMed Central

Background Although there are many reports regarding radiation-induced microbleeds, its frequency, relation to dose and latency after radiation are not fully elucidated. The purpose of this study was to evaluate the frequency, latency, patient factors and dose relation of radiation-induced microbleeds after cranial irradiation using phase-sensitive magnetic resonance imaging (PSI) at 3.0 T. Methods Retrospective evaluation of 34 patients (age range, 13–78 years; mean, 49 years; follow-up period, 3–169 months; mean 29 months) who had undergone cranial irradiation using magnetic resonance (MR) imaging including PSI was performed. Twenty-three patients received high-dose irradiation (44–60 Gy), and 11 patients received 24–30 Gy whole brain irradiation. When microbleeds were detected on MR imaging in these high-dose irradiation patients, dose distribution maps were reproduced by reviewing the clinical records. Then the irradiated areas were divided into 6 radiation-dose classes: regions > 55 Gy, 45–55 Gy, 35–45 Gy, 25–35 Gy, 15–25 Gy and 5–15 Gy. The frequency of microbleeds in each radiation-dose class was analyzed. Results Microbleeds were detected in 7 (21%) of 34 patients on T2-weighted imaging, whereas they were detected in 16 (47%) of the 34 patients on PSIs. The frequency of microbleeds was higher than previously reported. The latency of radiation-induced microbleeds after radiation was 3 months to 9 years (mean, 33 months). In high-dose irradiation patients, the frequency of microbleeds significantly was associated with radiation dose. There were no foci that were observed in regions that had received < 25 Gy. Conclusion Radiation-induced microbleeds occurred more frequently in the present study than has been previously reported. PSI can be used to detect these vascular changes earlier than other conventional MR imaging techniques.

Tanino, Tomohiko; Kanasaki, Yoshiko; Tahara, Takatoshi; Michimoto, Koichi; Kodani, Kazuhiko; Kakite, Suguru; Kaminou, Toshio; Watanabe, Takashi; Ogawa, Toshihide

2013-01-01

406

Possible Generation of Self-Magnetic Fields  

SciTech Connect

The earth generates its own magnetic field via a dynamo effect in a conducting fluid. The sun and some other stars also generate self-magnetic fields on large spatial scales and long timescales. Laser-produced plasmas generate intense self-magnetic fields on very short spatial and time scales. Could similar phenomena occur on intermediate spatial scales and timescales, such as in a laboratory plasma? Two questions are posed for consideration: (a) At high electromagnetic wave power input into a low-pressure gas could a significant self-magnetic field be generated? (b) If a self-magnetic field were generated, would it evolve toward a minimum-energy state? If the answers turned out to be affirmative, then the use of self-magnetic fields could have interesting applications.

Dolan, Thomas J. [International Atomic Energy Agency, Vienna (Austria)

2001-09-15

407

Static uniform magnetic fields and amoebae  

SciTech Connect

Three species of potentially pathogenic amoebae were exposed to 71 and 106.5 mT from constant homogeneous magnetic fields and examined for inhibition of population growth. The number of amoebae for three species was significantly less than controls after a 72 h exposure to the magnetic fields when the temperature was 20 C or above. Axenic cultures, i.e., cultures grown without bacteria, were significantly affected after only 24 h. In 20 of 21 tests using the three species, the magnetic field significantly inhibited the growth of amoebae. In one test in which the temperature was 20 C for 48 h, exposure to the magnetic field was not inhibitory. Final numbers of magnetic field-exposed amoebae ranged from 9 to 72% lower than the final numbers of unexposed controls, depending on the species. This research may lead to disinfection strategies utilizing magnetic fields for surfaces on which pathogenic amoebae may proliferate.

Berk, S.G.; Srikanth, S.; Mahajan, S.M.; Ventrice, C.A. [Tennessee Technological Univ., Cookeville, TN (United States)] [Tennessee Technological Univ., Cookeville, TN (United States)

1997-03-01

408

Probing interstellar magnetic fields with Supernova remnants  

NASA Astrophysics Data System (ADS)

As Supernova remnants expand, their shock waves are freezing in and compressing the magnetic field lines they encounter; consequently we can use Supernova remnants as magnifying glasses for their ambient magnetic fields. We will describe a simple model to determine emission, polarization, and rotation measure characteristics of adiabatically expanding Supernova remnants and how we can exploit this model to gain information about the large scale magnetic field in our Galaxy. We will give two examples: The SNR DA530, which is located high above the Galactic plane, reveals information about the magnetic field in the halo of our Galaxy. The SNR G182.4+4.3 is located close to the anti-centre of our Galaxy and reveals the most probable direction where the large-scale magnetic field is perpendicular to the line of sight. This may help to decide on the large-scale magnetic field configuration of our Galaxy. But more observations of SNRs are needed.

Kothes, Roland; Brown, Jo-Anne

2009-04-01

409

Magnetic field sensor for isotropically sensing an incident magnetic field in a sensor plane  

NASA Technical Reports Server (NTRS)

A magnetic field sensor that isotropically senses an incident magnetic field. This is preferably accomplished by providing a magnetic field sensor device that has one or more circular shaped magnetoresistive sensor elements for sensing the incident magnetic field. The magnetoresistive material used is preferably isotropic, and may be a CMR material or some form of a GMR material. Because the sensor elements are circular in shape, shape anisotropy is eliminated. Thus, the resulting magnetic field sensor device provides an output that is relatively independent of the direction of the incident magnetic field in the sensor plane.

Pant, Bharat B. (Inventor); Wan, Hong (Inventor)

2001-01-01

410

Trapped magnetic field measurements on HTS bulk by peak controlled pulsed field magnetization  

NASA Astrophysics Data System (ADS)

For the past several years, we have studied the high-temperature superconducting (HTS) synchronous motor assembled with melt-textured Gd-Ba-Cu-O bulk magnets. If the single pulse field magnetizes a bulk effectively, size of electrical motor will become small for the strong magnetic field of the HTS magnets without reducing output power of motor. In the previous study, we showed that the HTS bulk was magnetized to excellent cone-shape magnetic field distribution by using the waveform control pulse magnetization (WCPM) method. The WCPM technique made possible the active control of the waveform on which magnetic flux motion depended. We generated the pulse waveform with controlled risetime for HTS bulk magnetization to suppress the magnetic flux motion which decreases magnetization efficiency. The pulsed maximum magnetic flux density with slow risetime is not beyond the maximum magnetic flux density which is trapped by the static field magnetization. But, as for applying the pulse which has fast risetime, the magnetic flux which exceed greatly the threshold penetrates the bulk and causes the disorder of the trapped magnetic distribution. This fact suggests the possibility that the threshold at pulsed magnetization influences the dynamic magnetic flux motion. In this study, Gd-Ba-Cu-O bulk is magnetized by the controlled arbitrary trapezoidal shape pulse, of which the maximum magnetic flux density is controlled not to exceed the threshold. We will present the trapped magnetic characteristics and the technique to generate the controlled pulsed field.

Ida, Tetsuya; Watasaki, Masahiro; Kimura, Yosuke; Miki, Motohiro; Izumi, Mitsuru

2010-06-01

411

Swarm: ESA's Magnetic Field Mission  

NASA Astrophysics Data System (ADS)

Swarm is the fifth Earth Explorer mission in ESA's Living Planet Programme, and is scheduled for launch in 2012. The objective of the Swarm mission is to provide the best-ever survey of the geomagnetic field and its temporal evolution using a constellation of 3 identical satellites. The Mission shall deliver data that allow access to new insights into the Earth system by improved scientific understanding of the Earth's interior and near-Earth electromagnetic environment. After launch and triple satellite release at an initial altitude of about 490 km, a pair of the satellites will fly side-by-side with slowly decaying altitude, while the third satellite will be lifted to 530 km to complete the Swarm constellation. High-precision and high-resolution measurements of the strength, direction and variation of the magnetic field, complemented by precise navigation, accelerometer and electric field measurements, will provide the observations required to separate and model various sources of the geomagnetic field and near-Earth current systems. The mission science goals are to provide a unique view into Earth core dynamics, mantle conductivity, crustal magnetisation, ionospheric and magnetospheric current systems and upper atmosphere dynamics - ranging from understanding the geodynamo to contributing to space weather. The scientific objectives and results from recent scientific studies will be presented. In addition the current status of the project, which is presently approaching the final stage of the development phase, will be addressed. A consortium of European scientific institutes is developing a distributed processing system to produce geophysical (Level 2) data products to the Swarm user community. The setup of Swarm ground segment and the contents of the data products will be addressed. More information on the Swarm mission can be found at the mission web site (see URL below).

Drinkwater, M. R.; Haagmans, R.; Floberghagen, R.; Plank, G.; Menard, Y.

2011-12-01

412

Swarm: ESA's Magnetic Field Mission  

NASA Astrophysics Data System (ADS)

Swarm is the fifth Earth Explorer mission in ESA's Living Planet Programme, and is scheduled for launch in fall 2012. The objective of the Swarm mission is to provide the best-ever survey of the geomagnetic field and its temporal evolution using a constellation of three identical satellites. The mission shall deliver data that allow access to new insights into the Earth system by improved scientific understanding of the Earth's interior and near-Earth electromagnetic environment. After launch and triple satellite release at an initial altitude of about 490 km, a pair of the satellites will fly side-by-side with slowly decaying altitude, while the third satellite will be lifted to 530 km to complete the Swarm constellation. High-precision and high-resolution measurements of the strength, direction and variation of the magnetic field, complemented by precise navigation, accelerometer and electric field measurements, will provide the observations required to separate and model various sources of the geomagnetic field and near-Earth current systems. The mission science goals are to provide a unique view into Earth's core dynamics, mantle conductivity, crustal magnetisation, ionospheric and magnetospheric current systems and upper atmosphere dynamics - ranging from understanding the geodynamo to contributing to space weather. The scientific objectives and results from recent scientific studies will be presented. In addition the current status of the project, which is presently in the final stage of the development phase, will be addressed. A consortium of European scientific institutes is developing a distributed processing system to produce geophysical (Level 2) data products for the Swarm user community. The setup of the Swarm ground segment and the contents of the data products will be addressed. In case the Swarm satellites are already in orbit, a summary of the on-going mission operations activities will be given.

Plank, G.; Floberghagen, R.; Menard, Y.; Haagmans, R.

2012-12-01

413

Swarm: ESA's Magnetic Field Mission  

NASA Astrophysics Data System (ADS)

Swarm is the fifth Earth Explorer mission in ESA's Living Planet Programme, and is scheduled for launch in fall 2013. The objective of the Swarm mission is to provide the best-ever survey of the geomagnetic field and its temporal evolution using a constellation of three identical satellites. The mission shall deliver data that allow access to new insights into the Earth system by improved scientific understanding of the Earth's interior and near-Earth electromagnetic environment. After launch and triple satellite release at an initial altitude of about 490 km, a pair of the satellites will fly side-by-side with slowly decaying altitude, while the third satellite will be lifted to 530 km to complete the Swarm constellation. High-precision and high-resolution measurements of the strength, direction and variation of the magnetic field, complemented by precise navigation, accelerometer and electric field measurements, will provide the observations required to separate and model various sources of the geomagnetic field and near-Earth current systems. The mission science goals are to provide a unique view into Earth's core dynamics, mantle conductivity, crustal magnetisation, ionospheric and magnetospheric current systems and upper atmosphere dynamics - ranging from understanding the geodynamo to contributing to space weather. The scientific objectives and results from recent scientific studies will be presented. In addition the current status of the project, which is presently in the final stage of the development phase, will be addressed. A consortium of European scientific institutes is developing a distributed processing system to produce geophysical (Level 2) data products for the Swarm user community. The setup of the Swarm ground segment and the contents of the data products will be addressed. In case the Swarm satellites are already in orbit, a summary of the on-going mission operations activities will be given. More information on Swarm can be found at www.esa.int/esaLP/LPswarm.html.

Plank, G.; Floberghagen, R.; Menard, Y.; Haagmans, R.

2013-12-01

414

Swarm: ESA's Magnetic Field Mission  

NASA Astrophysics Data System (ADS)

Swarm is the fifth Earth Explorer mission in ESA's Living Planet Programme, and is scheduled for launch in 2013. The objective of the Swarm mission is to provide the best-ever survey of the geomagnetic field and its temporal evolution using a constellation of 3 identical satellites. The Mission shall deliver data that allow access to new insights into the Earth system by improved scientific understanding of the Earth's interior and near-Earth electromagnetic environment. After launch and triple satellite release at an initial altitude of about 490 km, a pair of the satellites will fly side-by-side with slowly decaying altitude, while the third satellite will be lifted to 530 km to complete the Swarm constellation. High-precision and high-resolution measurements of the strength, direction and variation of the magnetic field, complemented by precise navigation, accelerometer and electric field measurements, will provide the observations required to separate and model various sources of the geomagnetic field and near-Earth current systems. The mission science goals are to provide a unique view into Earth's core dynamics, mantle conductivity, crustal magnetisation, ionospheric and magnetospheric current systems and upper atmosphere dynamics - ranging from understanding the geodynamo to contributing to space weather. The scientific objectives and results from recent scientific studies will be presented. In addition the current status of the project, which is presently in the final stage of the development phase, will be addressed. A consortium of European scientific institutes is developing a distributed processing system to produce geophysical (Level 2) data products for the Swarm user community. The setup of the Swarm ground segment and the contents of the data products will be addressed. More information on Swarm can be found at www.esa.int/esaLP/LPswarm.html.

Plank, Gernot; Haagmans, Roger; Floberghagen, Rune; Menard, Yvon

2013-04-01

415

Plasma behaviour in a rotating magnetic field  

Microsoft Academic Search

A system was constructed and used to study the behavior of a plasma in a rotating magnetic field in a toroidal system. The plasma density is first formed by RF pre-ionization at low pressure in the presence of a quasi-steady toroidal magnetic field of 0.4 T. The 1.85 MHz rotating magnetic field is generated by two perpendicular four-turn coils driven

M. R. Shubaly

1974-01-01

416

Magnet calculations at the Grenoble High Magnetic Field Laboratory  

Microsoft Academic Search

An axisymmetrical constrained semi-analytic optimization process is our basic tool for designing magnets. Developments of 3-D numerical models are undertaken to complement this approach. Such models are needed to investigate the overall behavior of our magnets. They are likely to provide suitable insights to solve the design problems arising from the demand for high magnetic field with both great spatial

Christophe Trophime; Konstantin Egorov; François Debray; W. Joss; G. Aubert

2002-01-01

417

Magnetization curve of spin ice in a [111] magnetic field  

Microsoft Academic Search

Spin ice in a magnetic field in the [111] direction displays two magnetization plateaus: one at saturation and an intermediate one with finite entropy. We study the crossovers between the different regimes from a point of view of (entropically) interacting defects. We develop an analytical theory for the nearest-neighbor spin ice model, which covers most of the magnetization curve. We

S. V. Isakov; K. S. Raman; R. Moessner; S. L. Sondhi

2004-01-01

418

Flow Transitions in a Rotating Magnetic Field  

NASA Technical Reports Server (NTRS)

Critical Rayleigh numbers have been measured in a liquid metal cylinder of finite height in the presence of a rotating magnetic field. Several different stability regimes were observed, which were determined by the values of the Rayleigh and Hartmann numbers. For weak rotating magnetic fields and small Rayleigh numbers, the experimental observations can be explained by the existence of a single non-axisymmetric meridional roll rotating around the cylinder, driven by the azimuthal component of the magnetic field. The measured dependence of rotational velocity on magnetic field strength is consistent with the existence of laminar flow in this regime.

Volz, M. P.; Mazuruk, K.

1996-01-01

419

Horizontal magnetic fields in the solar photosphere  

NASA Astrophysics Data System (ADS)

Two-dimensional simulations of time-dependent solar magnetogranulation are used to analyze the horizontal magnetic fields and the response of the synthesized Stokes profiles of the IR FeI ?1564.85 nm line to the magnetic fields. The 1.5-h series of MHD models used for the analyses reproduces a region of the magnetic network in the photosphere with an unsigned magnetic flux density of 192 G at the solar surface. According to the magnetic-field distribution obtained, the most probable absolute strength of the horizontal magnetic field at an optical depth of ? 5 = 1( ? 5 denotes ? at ? = 500 nm) is 50 G, while the mean value is 244 G. On average, the horizontal magnetic fields are stronger than the vertical fields to heights of about 400 km in the photosphere due to their higher density and the larger area they occupy. The maximum factor by which the horizontal fields are greater is 1.5. Strong horizontal magnetic flux tubes emerge at the surface as spots with field strengths of more than 500 G. These are smaller than granules in size, and have lifetimes of 3-6 min. They form in the photosphere due to the expulsion of magnetic fields by convective flows coming from deep subphotospheric layers. The data obtained qualitatively agree with observations with the Hinode space observatory.

Sheminova, V. A.

2009-05-01

420

Ferroelectric Cathodes in Transverse Magnetic Fields  

SciTech Connect

Experimental investigations of a planar ferroelectric cathode in a transverse magnetic field up to 3 kGs are presented. It is shown that the transverse magnetic field affects differently the operation of ferroelectric plasma cathodes in ''bright'' and ''dark'' modes in vacuum. In the ''bright'' mode, when the surface plasma is formed, the application of the transverse magnetic field leads to an increase of the surface plasma density. In the ''dark'' mode, the magnetic field inhibits the development of electron avalanches along the surface, as it does similarly in other kinds of surface discharges in the pre-breakdown mode.

Alexander Dunaevsky; Yevgeny Raitses; Nathaniel J. Fisch

2002-07-29

421

Five years of magnetic field management  

SciTech Connect

The extensive publicity of epidemiological studies inferring correlation between 60 Hz magnetic fields and childhood leukemia prompted world wide research programs that have as a goal to determine if low frequency magnetic fields represent any risk for the general population, children or utility workers. While supporting this research effort through EPRI, Con Edison embarked on a technical research program aimed to: characterize magnetic fields as to intensity and variation in time; and investigate practical means to manage these magnetic fields through currently known methods. The final goal of these research projects is to establish viable methods to reduce magnetic field intensity to desired values at reasonable distances from the sources. This goal was pursued step by step, starting with an inventory of the main sources of magnetic fields in substations, distribution and transmission facilities and generating plants. The characterization of the sources helped to identify typical cases and select specific cases, far practical applications. The next step was to analyze the specific cases and develop design criteria for managing the magnetic fields in new installations. These criteria included physical arrangement of equipment based oil calculation of magnetic fields, cancellation effect, desired maximum field intensity at specific points and shielding with high magnetic permeability metals (mu-metal and steel). This paper summarizes the authors` experiences and shows the results of the specific projects completed in recent years.

Durkin, C.J.; Fogarty, R.P.; Halleran, T.M.; Mark, Dr. D.A.; Mukhopadhyay, A.

1995-01-01

422

Comparison of Gross Body Fat-Water Magnetic Resonance Imaging at 3 Tesla to Dual Energy X-Ray Absorptiometry in Obese Women  

PubMed Central

Improved understanding of how depot-specific adipose tissue mass predisposes to obesity-related comorbidities could yield new insights into the pathogenesis and treatment of obesity as well as metabolic benefits of weight loss. We hypothesized that three-dimensional contiguous “fat-water” MR imaging (FWMRI) covering the majority of a whole-body field of view (FOV) acquired at 3 Tesla (3T) and coupled with automated segmentation and quantification of amount, type and distribution of adipose and lean soft tissue would show great promise in body composition methodology. Precision of adipose and lean soft tissue measurements in body and trunk regions were assessed for 3T FWMRI and compared to DEXA. Anthropometric, FWMRI and DEXA measurements were obtained in twelve women with BMI 30–39.9 kg/m2. Test-retest results found coefficients of variation for FWMRI that were all under 3%: gross body adipose tissue (GBAT) 0.80%, total trunk adipose tissue (TTAT) 2.08%, visceral adipose tissue (VAT) 2.62%, subcutaneous adipose tissue (SAT) 2.11%, gross body lean soft tissue (GBLST) 0.60%, and total trunk lean soft tissue (TTLST) 2.43%. Concordance correlation coefficients between FWMRI and DEXA were 0.978, 0.802, 0.629, and 0.400 for GBAT, TTAT, GBLST and TTLST, respectively. While Bland Altman plots demonstrated agreement between FWMRI and DEXA for GBAT and TTAT, a negative bias existed for GBLST and TTLST measurements. Differences may be explained by the FWMRI FOV length and potential for DEXA to overestimate lean soft tissue. While more development is necessary, the described 3T FWMRI method combined with fully-automated segmentation is fast (<30 minutes total scan and post-processing time), noninvasive, repeatable and cost effective.

Silver, HJ; Niswender, KD; Kullberg, J; Berglund, J; Johansson, L; Bruvold, M; Avison, MJ; Welch, EB.

2012-01-01

423

Magnetic monopole field exposed by electrons  

NASA Astrophysics Data System (ADS)

The experimental search for magnetic monopole particles has, so far, been in vain. Nevertheless, these elusive particles of magnetic charge have fuelled a rich field of theoretical study. Here, we created an approximation of a magnetic monopole in free space at the end of a long, nanoscopically thin magnetic needle. We experimentally demonstrate that the interaction of this approximate magnetic monopole field with a beam of electrons produces an electron vortex state, as theoretically predicted for a true magnetic monopole. This fundamental quantum mechanical scattering experiment is independent of the speed of the electrons and has consequences for all situations where electrons meet such monopole magnetic fields, as, for example, in solids. The set-up not only shows an attractive way to produce electron vortex states but also provides a unique insight into monopole fields and shows that electron vortices might well occur in unexplored solid-state physics situations.

Béché, Armand; van Boxem, Ruben; van Tendeloo, Gustaaf; Verbeeck, Jo

2014-01-01

424

The Magnetic Fields of the Quiet Sun  

NASA Astrophysics Data System (ADS)

This work reviews our understanding of the magnetic fields observed in the quiet Sun. The subject has undergone a major change during the last decade (quiet revolution), and it will remain changing since the techniques of diagnostic employed so far are known to be severely biased. Keeping these caveats in mind, our work covers the main observational properties of the quiet Sun magnetic fields: magnetic field strengths, unsigned magnetic flux densities, magnetic field inclinations, as well as the temporal evolution on short time-scales (loop emergence), and long time-scales (solar cycle). We also summarize the main theoretical ideas put forward to explain the origin of the quiet Sun magnetism. A final prospective section points out various areas of solar physics where the quiet Sun magnetism may have an important physical role to play (chromospheric and coronal structure, solar wind acceleration, and solar elemental abundances).

Sánchez Almeida, J.; Martínez González, M.

2011-04-01

425

Concentrator of magnetic field of light  

NASA Astrophysics Data System (ADS)

In the recent decade metamaterials with magnetic permeability different than unity and unusual response to the magnetic field of incident light have been intensively explored. Existence of magnetic artificial materials created an interest in a scanning near-field magnetic microscope for studies of magnetic responses of subwavelength elementary cells of those metamaterials. We present a method of measuring magnetic responses of such elementary cells within a wide range of optical frequencies with single probes of two types. The first type probe is made of a tapered silica fiber with radial metal stripes separated by equidistant slits of constant angular width. The second type probe is similar to metal coated, corrugated, tapered fiber apertured SNOM probe, but in this case corrugations are radially oriented. Both types of probes have internal illumination with azimuthally polarized light. In the near-field they concentrate into a subwavelength spot the longitudinal magnetic field component which is much stronger than the perpendicular electric one.

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

2012-05-01

426

Magnetization and magnetic susceptibility of DyH3  

NASA Technical Reports Server (NTRS)

The magnetization and differential magnetic susceptibility of powdered DyH3 samples are measured at a temperature of 4.2 K in applied magnetic fields ranging up to 9 Teslas. The differential magnetic susceptibility is also investigated in the zero applied field. Magnetization is plotted as a function of field strength, and differential susceptibility is described as a function of both field strength and temperature. A saturation magnetic moment of 5.12 Bohr magnetons per ion is derived from the magnetization data, and the zero-field susceptibility measurements are found to indicate antiferromagnetic ordering below 3.45 K. The susceptibility at 4.2 K is shown to have an inverse-square dependence on field strength for values of not less than 0.3 Tesla.

Flood, D. J.

1975-01-01

427

Ohm's Law for Mean Magnetic Fields.  

National Technical Information Service (NTIS)

Spatially complicated magnetic fields are frequently treated as the sum of a large, slowly varying, mean field and a small, rapidly varying, field. The primary effect of the small field is to modify the Ohm's law of the mean field. A set of plausible assu...

A. H. Boozer

1984-01-01

428

Magnetic field evolution in interacting galaxies  

NASA Astrophysics Data System (ADS)

Aims: Violent gravitational interactions can change the morphologies of galaxies and, by means of merging, transform them into elliptical galaxies. We aim to investigate how they affect the evolution of galactic magnetic fields. Methods: We selected 16 systems of interacting galaxies with available VLA archive radio data at 4.86 and 1.4 GHz and compared their radio emission and estimated magnetic field strengths with their star-forming activity, far-infrared emission, and the stage of tidal interaction. Results: The estimated mean of total magnetic field strength for our sample of interacting galaxies is 14 ± 5 ?G, which is larger than for the non-interacting objects. The field regularity (of 0.27 ± 0.09) is lower than in typical spirals and indicates enhanced production of random magnetic fields in the interacting objects. We find a general evolution of magnetic fields: for weak interactions the strength of magnetic field is almost constant (10-15 ?G) as interaction advances, then it increases up to 2× , peaks at the nuclear coalescence (25 ?G), and decreases again, down to 5-6 ?G, for the post-merger remnants. The main production of magnetic fields in colliding galaxies thus terminates somewhere close to the nuclear coalescence, after which magnetic field diffuses. The magnetic field strength for whole galaxies is weakly affected by the star formation rate (SFR), while the dependence is higher for galactic centres. We show that the morphological distortions visible in the radio total and polarized emission do not depend statistically on the global or local SFRs, while they do increase (especially in the polarization) with the advance of interaction. The constructed radio-far-infrared relations for interacting and non-interacting galaxies display a similar balance between the generation of cosmic rays, magnetic fields, and the production of the thermal energy and dust radiation. Conclusions: The regular magnetic fields are much more sensitive to morphological distortions induced by tidal interactions than are the random fields. As a result the polarized emission could be yet another indicator of an ongoing merging process. The found evolution of magnetic field with advancing interaction would definitely imply a stronger effect of magnetic fields on the galaxy surroundings in the earlier cosmological epochs. The process of strong gravitational interactions can efficiently magnetize the merger's surroundings, having a similar magnetizing effect on intergalactic medium as supernova explosions or galactic winds. If interacting galaxies generate some ultra-high energy cosmic rays (UHECRs), the disk or magnetized outflows can deflect them (up to 23°), and make an association of the observed UHECRs with t