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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 2-Tesla transmission line magnet  

SciTech Connect

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 probe, a program of magnetic field quality measurements was successfully performed. Results of the measurements are presented and discussed.

Velev, G.V.; Foster, W.; Kashikhin, V.; Mazur, P.; Oleck, A.; Piekarz, H.; Schlabach, P.; Sylvester, C.; /Fermilab; Wake, M.; /KEK, Tsukuba

2005-09-01

3

Measuring and shimming the magnetic field of a 4 Tesla MRI magnet  

E-print Network

The Biomedical Magnetic Resonance Laboratory (BMRL) of the University of Illinois at Urbana-Champaign (UIUC) has ordered from the Texas Accelerator Center (TAC) a superconducting, self-shielded, solenoidal magnet with a maximum field of 4 Tesla...

Kyriazis, Georgios

2012-06-07

4

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

5

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

6

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

7

Tuning magnetic disorder in diluted magnetic semiconductors using high fields to 89 Tesla  

SciTech Connect

We describe recent and ongoing studies at the National High Magnetic Field Laboratory at Los Alamos using the new '100 Tesla Multi-Shot Magnet', which is presently delivering fields up to {approx}89 T during its commissioning. We discuss the first experiments performed in this magnet system, wherein the linewidth of low-temperature photoluminescence spectra was used to directly reveal the degree of magnetic alloy disorder 'seen' by excitons in single Zn{sub 0.80}Cd{sub 0.22}Mn{sub 0.08}Se quantum wells. The magnetic potential landscape in II-VI diluted magnetic semiconductors (DMS) is typically smoothed when the embedded Mn{sup 2+} spins align in an applied field. However, an important (but heretofore untested) prediction of current models of compositional disorder is that magnetic alloy fluctuations in many DMS compounds should increase again in very large magnetic fields approaching 100 T. We observed precisely this increase above {approx}70 T, in agreement with a simple model of magnetic alloy disorder.

Crooker, Scott A [Los Alamos National Laboratory; Samarth, Nitin [PENN STATE U

2008-01-01

8

Detection of pico-Tesla magnetic fields using magneto-electric sensors at room temperature  

SciTech Connect

The measurement of low-frequency (10{sup -2}-10{sup 3} Hz) minute magnetic field variations (10{sup -12} Tesla) at room temperature in a passive mode of operation would be critically enabling for deployable neurological signal interfacing and magnetic anomaly detection applications. However, there is presently no magnetic field sensor capable of meeting all of these requirements. Here, we present new bimorph and push-pull magneto-electric laminate composites, which incorporate a charge compensation mechanism (or bridge) that dramatically enhances noise rejection, enabling achievement of such requirements.

Zhai Junyi; Xing Zengping; Dong Shuxiang; Li Jiefang; Viehland, D. [Department of Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)

2006-02-06

9

Micromechanical ``Trampoline'' Magnetometers for Use in Pulsed Magnetic Fields Exceeding 60 Tesla  

NASA Astrophysics Data System (ADS)

We present the design, construction, and operation of a novel magnetometer for use in intense pulsed magnetic fields. The magnetometer consists of a silicon micromachined "trampoline" to which the sample is attached. The small size of the device (typically 400 microns on a side) gives a fast mechanical response (10,000 to 50,000 Hz) and extremely high sensitivity (10-11 Am^2, corresponding to 10-13 Am^2/Hz^(1/2)). The device is robust against electrical and mechanical noise and requires no special vibration isolation from the pulsed magnet. As a demonstration, we present data taken in a 60 tesla pulsed magnetic field which show clear de Haas-van Alphen oscillations in a one microgram sample of the organic superconductor K-(BEDT-TTF)_2Cu(NCS)_2.

Balakirev, F. F.; Boebinger, G. S.; Aksyuk, V.; Gammel, P. L.; Haddon, R. C.; Bishop, D. J.

1998-03-01

10

Low-noise nano superconducting quantum interference device operating in Tesla magnetic fields.  

PubMed

Superconductivity in the cuprate YBa(2)Cu(3)O(7) (YBCO) persists up to huge magnetic fields (B) up to several tens of Teslas, and sensitive direct current (dc) superconducting quantum interference devices (SQUIDs) can be realized in epitaxially grown YBCO films by using grain boundary Josephson junctions (GBJs). Here we present the realization of high-quality YBCO nanoSQUIDs, patterned by focused ion beam milling. We demonstrate low-noise performance of such a SQUID up to B = 1 T applied parallel to the plane of the SQUID loop at the temperature T = 4.2 K. The GBJs are shunted by a thin Au layer to provide nonhysteretic current voltage characteristics, and the SQUID incorporates a 90 nm wide constriction which is used for on-chip modulation of the magnetic flux through the SQUID loop. The white flux noise of the device increases only slightly from 1.3 ??(0)/(Hz)(1/2) at B = 0 to 2.3 ??(0)/(Hz))(1/2) at 1 T. Assuming that a point-like magnetic particle with magnetization in the plane of the SQUID loop is placed directly on top of the constriction and taking into account the geometry of the SQUID, we calculate a spin sensitivity S(?)(1/2) = 62 ?(B)/(Hz))(1/2) at B = 0 and 110 ?(B)/(Hz))(1/2) at 1 T. The demonstration of low noise of such a SQUID in Tesla fields is a decisive step toward utilizing the full potential of ultrasensitive nanoSQUIDs for direct measurements of magnetic hysteresis curves of magnetic nanoparticles and molecular magnets. PMID:23252846

Schwarz, Tobias; Nagel, Joachim; Wölbing, Roman; Kemmler, Matthias; Kleiner, Reinhold; Koelle, Dieter

2013-01-22

11

Scripta Materialia 52 (2004) 461-466 Effect of 30 Tesla Magnetic Field on Transformations in a  

E-print Network

the magnitude of the free energy change accompanying the decomposition of austenite, with the addition of cobalt; this is because the ferrite is ferromagnetic below about 760°C whereas the austenite in low-alloy steels transforms to ferrite. Thus, a 30 Tesla magnetic field can raise transformation temperatures by ~90°C during

Cambridge, University of

12

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. PMID:16831232

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

2006-01-01

13

Thirteen Tesla magnet constructed with MJR wire  

SciTech Connect

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 was operated at 8.5 Tesla. The total field achieved was 13.0 Tesla with no training quench observed; although training was initially observed when the magnet was first tested alone up to 4.6 Tesla at American Magnets, Inc. (AMI). The magnet winding techniques utilize Airco's fiberglass type wire insulation, an AMI proprietary cement, argon atmosphere 700/sup 0/C for 100 hour reaction, followed by a postreaction potting impregnation. The MJR wire lot used (M22) was short sample tested and the Ln (J /SUB c/ ) -vs-H line intersected the insert magnet operating curve at 13.5 Tesla. The wire lot used has a 34 volume % copper external sheath for quench protection. The wire was fabricated with 15.4 volume % niobium and bronze/niobium ratio of 3.0 with 13.% Sn bronze.

Siddall, M.; Efferson, K.; Mcdonald, W.

1983-05-01

14

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

15

Strongest non-destructive magnetic field: world record set at 100-tesla level  

E-print Network

the NHMFL. Record magnetic field attracts new scientific questions The ability to create pulses of extremely a range of scientific questions: from how materials behave under the influence of very high magnetic Chuck Mielke, director of the Pulsed Field Facility at Los Alamos. It was a scientific quest that has

16

The NHMFL 60 tesla, 100 millisecond pulsed magnet  

Microsoft Academic Search

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

H. J. Boenig; L. J. Campbell; D. G. Rickel; J. D. Rogers; J. B. Schillig; J. R. Sims; P. Pernambuco-Wise; H. J. Schneider-Muntau

1992-01-01

17

Thermopower measurements in magnetic fields up to 17 tesla using the toggled heating method  

NASA Astrophysics Data System (ADS)

A dc method for thermopower (TP) measurements in magnetic fields up to 17 T in the temperature range from 3 K to 300 K is introduced. A special heating technique named ``seesaw heating,'' a method similar to ac methods, was developed and resulted in good thermal stability, better accuracy and a faster procedure. Chromel-constantan thermocouples were utilized for measuring probes because of small and simple temperature dependence of magnetic field effect. Finding an empirical formula for all the calibration curves of TP of Chromel enable us to measure TP at any field and at any temperature. Finally, the experimental results on ErCo2 and LaRu2 are presented as test examples to demonstrate the possibilities and accuracy of our setup.

Resel, R.; Gratz, E.; Burkov, A. T.; Nakama, T.; Higa, M.; Yagasaki, K.

1996-05-01

18

Thermopower measurements in magnetic fields up to 17 tesla using the toggled heating method  

SciTech Connect

A dc method for thermopower (TP) measurements in magnetic fields up to 17 T in the temperature range from 3 K to 300 K is introduced. A special heating technique named {open_quote}{open_quote}seesaw heating,{close_quote}{close_quote} a method similar to ac methods, was developed and resulted in good thermal stability, better accuracy and a faster procedure. Chromel{endash}constantan thermocouples were utilized for measuring probes because of small and simple temperature dependence of magnetic field effect. Finding an empirical formula for all the calibration curves of TP of Chromel enable us to measure TP at any field and at any temperature. Finally, the experimental results on ErCo{sub 2} and LaRu{sub 2} are presented as test examples to demonstrate the possibilities and accuracy of our setup. {copyright} {ital 1996 American Institute of Physics.}

Resel, R.; Gratz, E. [Institute for Experimental Physics, Technical University Vienna, Vienna (Austria)] [Institute for Experimental Physics, Technical University Vienna, Vienna (Austria); Burkov, A.T. [A. F. Ioffe Physico--Technical Institute, Russian Academy of Science, St. Petersburg 184021 (Russia)] [A. F. Ioffe Physico--Technical Institute, Russian Academy of Science, St. Petersburg 184021 (Russia); Nakama, T.; Higa, M.; Yagasaki, K. [Department of Physics, University of the Ryukyus, Okinawa 903-01 (Japan)] [Department of Physics, University of the Ryukyus, Okinawa 903-01 (Japan)

1996-05-01

19

Conceptual approach to the design of 50-tesla hyper-field superconducting magnetic coils  

NASA Astrophysics Data System (ADS)

Perhaps one of the principle advantages of the open-ended geometry afforded by the mirror fusion reactor designs, in contrast to that of the tokamak proposals, is the potential future upgradability of these systems to also encompass advanced fusion fuel cycles. This is the combined result of both the ability to convert the energy of the escaping charged particles directly into electricity and from a magnet design viewpoint; the much higher required containment field strengths (between 40 to 50 T in the mirror choke coils and approximately 12 T in the central cell magnets) dictate that the tokamak geometry lacks adequate real estate for structural support against the resulting electromagnetic stresses. The latter consideration is highlighted by F. Moon's report on the Virial Theorem, which states that the minimal amount of structural mass needed for a magnet scales as both the magnetic stored energy and a multiplicative factor that increases with the geometric complexity of the proposed magnet system. Solenoids are, of course, the simplest source of fields, which implies that if strengths of 40 to 50 T are indeed possible, we should first seek their production in this geometry.

Hoard, R. W.

1985-08-01

20

Normal-state transport in electron-doped La2-xCexCuO4 thin films in magnetic fields up to 40 Tesla  

E-print Network

Normal-state transport in electron-doped La2-xCexCuO4 thin films in magnetic fields up to 40 Tesla-3001 Leuven, Belgium Received 21 February 2008; published 12 May 2008 The in-plane normal field. DOI: 10.1103/PhysRevB.77.172503 PACS number s : 74.25.Fy, 74.40. k, 74.72. h Studying the normal

Moshchalkov, Victor V.

21

Magnetically programmable shunt valve: MRI at 3-Tesla.  

PubMed

A magnetically programmable cerebrospinal fluid (CSF) shunt valve (Codman Hakim Programmable Valve, Codman, a Johnson & Johnson Company, Raynham, MA) was assessed for magnetic field interactions, heating, artifacts and functional changes at 3-Tesla. The programmable valve showed minor magnetic field interactions and heating (+0.4 degrees C). Artifacts were relatively large in relation to the size and shape of this implant and, as such, may create a problem if the area of interest is in proximity to this implant. While multiple exposures and various magnetic resonance imaging (MRI) conditions at 3-Tesla changed the settings of some valves (i.e., reprogramming was needed), the function of the programmable valve was not permanently affected. Therefore, this magnetically programmable CSF shunt valve is acceptable for a patient undergoing MRI at 3-Tesla or less when specific safety guidelines are followed, including resetting the valve, as needed. PMID:17707175

Shellock, Frank G; Wilson, Stephen F; Mauge, Christophe P

2007-09-01

22

Design and prototype fabrication of a 30 tesla cryogenic magnet  

Microsoft Academic Search

A liquid-neon-cooled magnet has been designed to produce 30 teslas in steady operation. Its feasibility was established by a previously reported parametric study. To ensure the correctness of the heat transfer relationships used, supercritical neon heat transfer tests were made. Other tests made before the final design included tests on the effect of the magnetic field on pump motors; tensile-shear

G. M. Prok; M. C. Swanson; G. V. Brown

1977-01-01

23

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

E-print Network

An important technological step towards the realization of an ultra-granular hadronic calorimeter to be used in the future International Linear Collider (ILC) experiments has been made. A 33X50 cm2 GRPC detector equipped with a power-pulsed electronics board offering a 1cm2 lateral segmentation was successfully tested in a 3-Tesla magnet operating at the H2 beam line of the CERN SPS. An important reduction of power consumption with no deterioration of the detector performance is obtained when the power-pulsing mode is applied. This important result shows that ultra-granular calorimeters for ILC experiments are not only an attractive but also a realistic option.

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

2011-11-23

24

Status of the NHMFL 60 tesla quasi-continuous magnet  

SciTech Connect

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. [Los Alamos National Lab., NM (United States); Schneider-Muntau, H.J. [National High Magnetic Field Laboratory (NHMFL), Tallahassee, FL (United States)

1995-07-01

25

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

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

Prosthetic heart valves and annuloplasty rings: assessment of magnetic field interactions, heating, and artifacts at 1.5 Tesla.  

PubMed

The purpose of this study was to determine the magnetic resonance (MR) safety aspects and artifacts for three different heart valve prostheses and two different annuloplasty rings that have not been evaluated previously in association with the 1.5-T MR environment. Ex vivo testing was performed using previously described techniques for the evaluation of magnetic field interactions (deflection angle and torque), heating (gel-filled phantom and fluoroptic thermometry; 15 min of MR imaging at a whole body-averaged specific absorption rate of 1.2 W/kg), and artifacts (using T1-weighted, spin echo, and gradient echo pulse sequences). One heart valve prosthesis and one annuloplasty ring showed no magnetic field interactions. Two heart valve prostheses and one annuloplasty ring displayed relatively minor magnetic field interactions (i.e., deflection angle < or = 6 degrees, torque, +1). Heating was < or = 0.7 degrees C for the five different implants. Artifacts varied depending on the amount and type of metal used to make the implants. For the three heart valve prostheses and two annuloplasty rings, the lack of substantial magnetic field interactions and relatively minor hearing indicated that MR procedures may be conducted safetly in patients with these implants using MR systems operating with static magneticfields of 1.5 T or less. Notably, these findings essentially apply to 54 different heart valve prostheses and 37 different annuloplasty rings (i.e., based on the various models and sizes available for these implants). PMID:11777223

Shellock, F G

2001-01-01

28

Design and prototype fabrication of a 30 tesla cryogenic magnet  

NASA Technical Reports Server (NTRS)

A liquid neon cooled magnet was designed to produce 30 teslas in steady operation. To ensure the correctness of the heat transfer relationships used, supercritical neon heat transfer tests were made. Other tests made before the final design included tests on the effect of the magnetic field on pump motors, tensile shear tests on the cryogenic adhesives, and simulated flow studies for the coolant. The magnet will consist of two pairs of coils, cooled by forced convection of supercritical neon. Heat from the supercritical neon will be rejected through heat exchangers which are made of roll bonded copper panels and are submerged in a pool of saturated liquid neon. A partial mock up coil was wound to identify the tooling required to wind the magnet. This was followed by winding a prototype pair of coils. The prototype winding established procedures for fabricating the final magnet and revealed slight changes needed in the final design.

Prok, G. M.; Swanson, M. C.; Brown, G. V.

1977-01-01

29

Poly-coil design for a 60 tesla quasi-stationary magnet  

Microsoft Academic Search

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

H. J. Boenig; L. J. Campbell; M. L. Hodgdon; E. A. Lopez; D. G. Rickel; J. D. Rogers; J. B. Schillig; J. R. Sims; P. Pernambuco-Wise; H. J. Schneider-Muntau; L. Van Bockstal

1993-01-01

30

Detection of Sub-Nano-Tesla Magnetic Field by Integrated Magnetic Tunnel Junctions with Bottom Synthetic Antiferro-Coupled Free Layer  

NASA Astrophysics Data System (ADS)

Arrays of 100×100 magnetic tunnel junctions (MTJs) connected in parallel and series were fabricated. A synthetic antiferro-coupled bottom free layer with a NiFe/Ru/CoFeB structure and MgO tunneling barrier were used to realize a high sensitivity, which is defined as TMR/2Hk, where, TMR is the tunneling magnetoresistance ratio and Hk is the magnetic anisotropy field of the free layer. To obtain a linear response of tunneling resistance against an applied external magnetic field, a double annealing process was carried out. From R-H curve measurements, the sensitivity of the 100×100 integrated MTJs was lower (8%/Oe) than that of a single MTJ (25%/Oe). However, a 1/30 decrease in noise power density was realized in the integrated MTJs. Consequently, a very small magnetic field of 0.29 nT was detected with the integrated MTJs.

Fujiwara, Kosuke; Oogane, Mikihiko; Nishikawa, Takuo; Naganuma, Hiroshi; Ando, Yasuo

2013-04-01

31

Design and prototype fabrication of a 30 tesla cryogenic magnet  

NASA Technical Reports Server (NTRS)

A liquid-neon-cooled magnet has been designed to produce 30 teslas in steady operation. Its feasibility was established by a previously reported parametric study. To ensure the correctness of the heat transfer relationships used, supercritical neon heat transfer tests were made. Other tests made before the final design included tests on the effect of the magnetic field on pump motors; tensile-shear tests on the cryogenic adhesives; and simulated flow studies for the coolant. The magnet will be made of two pairs of coils, cooled by forced convection of supercritical neon. Heat from the supercritical neon will be rejected through heat exchangers which are made of roll-bonded copper panels and are submerged in a pool of saturated liquid neon. A partial mock-up coil was wound to identify the tooling required to wind the magnet. This was followed by winding a prototype pair of coils. The prototype winding established procedures for fabricating the final magnet and revealed slight changes needed in the final design.

Prok, G. M.; Swanson, M. C.; Brown, G. V.

1977-01-01

32

Poly-coil design for a 60 tesla quasi-stationary magnet  

NASA Astrophysics Data System (ADS)

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.

Boenig, H. J.; Campbell, L. J.; Hodgdon, M. L.; Lopez, E. A.; Rickel, D. G.; Rogers, J. D.; Schillig, J. B.; Sims, J. R.; Pernambuco-Wise, P.; Schneider-Muntau, H. J.

1993-02-01

33

Poly-coil design for a 60 tesla quasi-stationary 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 1 00 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.

Boenig, H.J.; Campbell, L.J.; Hodgdon, M.L.; Lopez, E.A.; 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.; Van Bockstal, L. (Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab.)

1993-01-01

34

Poly-coil design for a 60 tesla quasi-stationary 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 1 00 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.

Boenig, H.J.; Campbell, L.J.; Hodgdon, M.L.; Lopez, E.A.; 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.; Van Bockstal, L. [Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab.

1993-02-01

35

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

36

Matching field effects at tesla-level magnetic fields in critical current density in high-Tc superconductors containing self-assembled columnar defects  

NASA Astrophysics Data System (ADS)

We have investigated the superconductive transport properties of Y Ba2Cu3O7 films containing self-assembled columnar arrays of second phase SrZrO3 or BaSnO3 precipitates. A matching condition between columnar pinning sites (aligned at or near the c axis) and external magnetic flux, tilted with respect to them, is identified in the critical current JC(H) data. The results for the material containing SrZrO3-based pins are analyzed within a simple intuitive model. At matching, the critical current is enhanced above the model prediction. In complementary contact-free investigations of BaSnO3-doped material, matching effects are observed over a wide range of temperatures in the field dependence of JC(H). The deduced matching fields agree reasonably well with the densities of columnar pins directly observed by scanning electron microscopy.

Sinclair, J. W.; Zuev, Y. L.; Cantoni, C.; Wee, S. H.; Varanasi, C.; Thompson, J. R.; Christen, D. K.

2012-11-01

37

Matching field effects at tesla-level magnetic fields in critical current density in high-Tc superconductors containing self-assembled columnar defects  

SciTech Connect

We have investigated the superconductive transport properties of YBa2Cu3O7 films containing self-assembled columnar arrays of second phase SrZrO3 or BaSnO3 precipitates. A matching condition between columnar pinning sites (aligned at or near the c axis) and external magnetic flux, tilted with respect to them, is identified in the critical current JC.H/ data. The results for the material containing SrZrO3-based pins are analyzed within a simple intuitive model. At matching, the critical current is enhanced above the model prediction. In complementary contact-free investigations of BaSnO3-doped material, matching effects are observed over a wide range of temperatures in the field dependence of JC.H/. The deduced matching fields agree reasonably well with the densities of columnar pins directly observed by scanning electron microscopy.

Sinclair, J. [University of Tennessee, Knoxville (UTK); Zuev, Yuri L [ORNL; Cantoni, Claudia [ORNL; Wee, Sung Hun [ORNL; Varanasi, C. V. [University of Dayton Research Institute; Thompson, James R [ORNL; Christen, David K [ORNL

2012-01-01

38

Bohr - Planck quantum theory, (Tesla) magnetic monopoles and fine structure constant  

E-print Network

In this work we apply Bohr-Planck (Old quantum atomic and radiation) theory, i.e. and quasi-classical methods for analysis of the magnetic monopoles and other problems. We reproduce exactly some basic elements of the Dirac magnetic monopoles theory, especially Dirac electric/magnetic charge quantization condition. Also, we suggest a new, effective, simply called Tesla model (for analogy with positions of the solenoids by Tesla inductive motor) of the magnetic monopole instead of usual effective Dirac model (half-infinite, very tinny solenoid) of the magnetic monopole. In our, i.e. Tesla model we use three equivalent tiny solenoids connected in series with a voltage source. One end of any solenoid is placed at the circumference of a circle and solenoids are directed radial toward circle center. Length of any solenoid is a bit smaller than finite circle radius so that other end of any solenoid is very close to the circle center. Angles between neighboring solenoids equal $120^{\\circ}$. All this implies that, practically, there is no magnetic field, or, magnetic pole, e.g. $S$, in the circle center, and that whole system holds only other, $N$ magnetic pole, at the ends of the solenoids at circle circumference. Finally, we reproduce relatively satisfactory value of the fine structure constant using Planck, i.e. Bose-Einstein statistics and Wien displacement law.

Vladan Pankovic; Darko V. Kapor; Stevica Djurovic; Miodrag Krmar

2014-10-17

39

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

40

A TX-4 tesla meter for measuring constant, alternating, and pulsed fields over a wide range of magnitudes  

Microsoft Academic Search

A new instrument—a magnetic-field meter (tesla meter)—having universal capabilities for measuring constant, alternating, and\\u000a pulsed magnetic fields over a wide range of magnitudes is presented. The instrument is intended for solving flaw-detection\\u000a problems and determining magnetic fields in gaps of welded steel articles as well as where the precise determination of magnetic\\u000a fields is required.

B. A. Khudyakov; M. B. Rigmant; V. B. Khudyakov; A. P. Nichipuruk

2007-01-01

41

Magnetic Field Problem: Measuring Current  

NSDL National Science Digital Library

A cross section of two circular wire loops carrying the exact same current is shown above (position given in centimeters and magnetic field given in milli-Tesla). You can click-drag to read the magnitude of the magnetic field.

Christian, Wolfgang; Belloni, Mario

2007-03-03

42

Design study of steady-state 30-tesla liquid-neon-cooled magnet  

NASA Technical Reports Server (NTRS)

A design for a 30-tesla, liquid-neon-cooled magnet was reported which is capable of continuous operation. Cooled by nonboiling, forced-convection heat transfer to liquid neon flowing at 2.8 cu m/min in a closed, pressurized heat-transfer loop and structurally supported by a tapered structural ribbon, the tape-wound coils with a high-purity-aluminum conductor will produce over 30 teslas for 1 minute at 850 kilowatts. The magnet will have an inside diameter of 7.5 centimeters and an outside diameter of 54 centimeters. The minimum current density at design field will be 15.7 kA/sq cm.

Prok, G. M.; Brown, G. V.

1976-01-01

43

The ORNL/General Dynamics/Airco design for the DOE 12-Tesla magnet program  

NASA Astrophysics Data System (ADS)

The design of the fusion engineering test facility (ETF) toroidal field magnet was accomplished by the application of structural, thermodynamic, and electrical principles. The Nb3Sn pool 12-Tesla ETF conductor is a Cu bar with a slot for the superconductor compacted monolith; design problems involved the triaxial loading on conductors, quench protection, and a.c. losses associated with pulsed fields and plasma disruption. An estimated 250% increase in the conductor stresses for ETF compared with the large coil program magnet was compensated for by the use of a higher strength copper and a greater structural efficiency.

Hackley, D. S.; Kruse, G. S.; Ring, D. S.

1981-01-01

44

Vacuum properties of high quality value tuning fork in high magnetic field up to 8 Tesla and at mK temperatures  

NASA Astrophysics Data System (ADS)

Tuning forks are very popular experimental tools widely applied in low and ultra low temperature physics as mechanical resonators and cantilevers in the study of quantum liquids, STM and AFM techniques, etc. As an added benefit, these forks being cooled, have very high Q-value, typically 106 and their properties seems to be magnetic field independent. We present preliminary vacuum measurements of a commercial tuning fork oscillating at frequency 32 kHz conducted in magnetic fields up to 8 T and at temperature ~ 10 mK. We found an additional weak damping of the tuning fork motion depending on magnetic field magnitude and we discuss physical nature of the observed phenomena.

?love?ko, M.; Kupka, M.; Skyba, P.; Vavrek, F.

2014-12-01

45

LBL program of 1 meter long, 50 mm diameter bore, dipoles with fields greater than 8 tesla  

NASA Astrophysics Data System (ADS)

Model dipole superconducting magnets with central fields above 8 tesla are being developed for future multi-TeV colliding beam accelerators. The first three models are 1 meter long, have nominal 50 mm diameter cold bores, and utilize Nb-Ti superconductor operating in He 2 at 1.8 K. None of the three models had an iron flux-return yoke. The maximum central fields achieved are 8.0, 8.6, and 9.1 tesla -- all short-sample performance at 1.8 K for the conductors used. At 4.3 K the maximum central fields are from 1.5 to 2.0 tesla lower. In one design, the superconductor is arranged in four concentric cylindrical layers, sometimes called a four-shell geometry. With higher current density, this design is expected to reach 10 tesla central field and a two layer design to reach 8 tesla. The other design uses 8 flat pancakes with upturned ends. Improved Nb-Ti should also allow this design to reach 10 tesla central field. This geometry is being used for a Nb3Sn wind-and-react dipole to be operated in He 1 at 4.3 K.

Hassenzahl, W. V.; Gilbert, W.; Taylor, C.; Meuser, R. B.

1983-08-01

46

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. PMID:23613896

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

2013-01-01

47

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

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)mm(3) 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. PMID:23613896

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

2013-01-01

48

A 10 Kelvin 3 Tesla Magnet for Space Flight ADR Systems  

NASA Technical Reports Server (NTRS)

Many future space flight missions are expected to use adiabatic demagnetization refrigerators (ADRs) to reach detector operating temperatures well below one Kelvin. The goal is to operate each ADR with a mechanical cooler as its heat sink, thus avoiding the use of liquid cryogens. Although mechanical coolers are being developed to operate at temperatures of 6 Kelvin and below, there is a large efficiency cost associated with operating them at the bottom of their temperature range. For the multi-stage ADR system being developed at Goddard Space Flight Center, the goal is to operate with a 10 Kelvin mechanical cooler heat sink. With currently available paramagnetic materials, the highest temperature ADR stage in such a system will require a magnetic field of approximately three Tesla. Thus the goal is to develop a small, lightweight three Tesla superconducting magnet for operation at 10 Kelvin. It is important that this magnet have a low current/field ratio. Because traditional NbTi magnets do not operate safely above about six Kelvin, a magnet with a higher Tc is required. The primary focus has been on Nb3Sn magnets. Since standard Nb3Sn wire must be coated with thick insulation, wound on a magnet mandrel and then reacted, standard Nb,Sn magnets are quite heavy and require high currents Superconducting Systems developed a Nb3Sn wire which can be drawn down to small diameter, reacted, coated with thin insulation and then wound on a small diameter coil form. By using this smaller wire and operating closer to the wire s critical current, it should be possible to reduce the mass and operating current of 10 Kelvin magnets. Using this "react-then-wind" technology, Superconducting Systems has produced prototype 10 Kelvin magnets. This paper describes the development and testing of these magnets and discusses the outlook for including 10 Kelvin magnets on space-flight missions.

Tuttle, Jim; Shirron, Peter; Canavan, Edgar; DiPirro, Michael; Riall, Sara; Pourrahimi, Shahin

2003-01-01

49

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

Microsoft Academic Search

High-resolution magnetic resonance imaging (MRI) of trabecular bone combined with quantitative image analysis represents a\\u000a powerful technique to gain insight into trabecular bone micro-architectural derangements in osteoporosis and osteoarthritis.\\u000a The increased signal-to-noise ratio of ultra high-field MR (?7 Tesla) permits images to be obtained with higher resolution\\u000a and\\/or decreased scan time compared to scanning at 1.5\\/3T. In this small feasibility

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

2011-01-01

50

Magnet Design and Analysis of a 40 Tesla Long Pulse System Energized by a Battery Bank  

NASA Astrophysics Data System (ADS)

A 40 tesla long pulse magnet and a battery bank as the power supply have been designed. This is now under construction at the Wuhan National High Magnetic Field Center. The 22 mm bore magnet will generate smooth pulses with duration 1 s and rise time 0.5 s. The battery bank consists of 945 12V/200 Ah lead-acid battery cells. The magnet and battery bank were optimized by codes developed in-house and by ANSYS. The coil was made from soft copper with internal reinforcement by fiber-epoxy composite; it is divided into two sections connected in series. The inner section consists of helix coils with each layer reinforced by Zylon composite. The outer section will be wound from copper sheet and externally reinforced by carbon fiber composite.

Lv, Y. L.; Peng, T.; Wang, G. B.; Ding, T. H.; Han, X. T.; Pan, Y.; Li, L.

2013-03-01

51

Magnetic Fields  

E-print Network

In this chapter, we give a brief introduction into the use of the Zeeman effect in astronomy and the general detection of magnetic fields in stars, concentrating on the use of FORS2 for longitudinal magnetic field measurements.

Schöller, Markus

2015-01-01

52

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

53

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

PubMed

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. PMID:21221706

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

2011-06-01

54

Femtotesla Magnetic Field Measurement with Magnetoresistive Sensors  

Microsoft Academic Search

The measurement of magnetic fields in the femtotesla (fT, 10-15 tesla) range is important for applications such as magnetometry, quantum computing, solid-state nuclear magnetic resonance, and magnetoencephalography. The only sensors capable of detecting these very small fields have been based on low-temperature superconducting quantum interference devices operating at 4.2 kelvin. We present a magnetic field sensor that combines a superconducting

Myriam Pannetier; Claude Fermon; Gerald Le Goff; Juha Simola; Emma Kerr

2004-01-01

55

The measurement and analysis of the magnetic field of a synchrotron light source magnet  

E-print Network

In this thesis a unique system is used to measure the magnetic field of a superconducting synchrotron light source magnet. The magnet measured is a superferric dipole C-magnet designed to produce a magnetic field up to 3 Tesla in magnitude. Its...

Graf, Udo Werner

2012-06-07

56

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

57

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

58

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

SciTech Connect

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 second with the field transverse to the beam direction a horizontal plane and finally the field can be applied vertically with respect to the beam. The magnet has a warm bore and an open geometry of 180 deg. , allowing large access to reciprocal space. A variable temperature insert has been developed, which is capable of working down to a temperature of 1.7 K and operating over a wide range of angles whilst maintaining a temperature stability of a few mK. Initial ferromagnetic diffraction measurements have been carried out on single crystal Tb and Dy samples.

Thompson, P. B. J.; Brown, S. D.; Bouchenoire, L.; Mannix, D. [XMaS, UK-CRG, ESRF, BP 220, F-38043 Grenoble CEDEX (France); Dept of Physics, University of Liverpool, Liverpool (United Kingdom); Paul, D. F. [XMaS, UK-CRG, ESRF, BP 220, F-38043 Grenoble CEDEX (France); Dept of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL (United Kingdom); Lucas, C. A.; Kervin, J. [Dept of Physics, University of Liverpool, Liverpool (United Kingdom); Cooper, M. J. [Dept of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL (United Kingdom); Arakawa, P.; Laughon, G. [American Magnetics Inc, P.O. Box2509, 112 Flint Road, Oak Ridge, TN 37831-2509 (United States)

2007-01-19

59

Rapid Parametric Mapping of the Longitudinal Relaxation Time T1 Using Two-Dimensional Variable Flip Angle Magnetic Resonance Imaging at 1.5 Tesla, 3 Tesla, and 7 Tesla  

PubMed Central

Introduction Visual but subjective reading of longitudinal relaxation time (T1) weighted magnetic resonance images is commonly used for the detection of brain pathologies. For this non-quantitative measure, diagnostic quality depends on hardware configuration, imaging parameters, radio frequency transmission field (B1+) uniformity, as well as observer experience. Parametric quantification of the tissue T1 relaxation parameter offsets the propensity for these effects, but is typically time consuming. For this reason, this study examines the feasibility of rapid 2D T1 quantification using a variable flip angles (VFA) approach at magnetic field strengths of 1.5 Tesla, 3 Tesla, and 7 Tesla. These efforts include validation in phantom experiments and application for brain T1 mapping. Methods T1 quantification included simulations of the Bloch equations to correct for slice profile imperfections, and a correction for B1+. Fast gradient echo acquisitions were conducted using three adjusted flip angles for the proposed T1 quantification approach that was benchmarked against slice profile uncorrected 2D VFA and an inversion-recovery spin-echo based reference method. Brain T1 mapping was performed in six healthy subjects, one multiple sclerosis patient, and one stroke patient. Results Phantom experiments showed a mean T1 estimation error of (-63±1.5)% for slice profile uncorrected 2D VFA and (0.2±1.4)% for the proposed approach compared to the reference method. Scan time for single slice T1 mapping including B1+ mapping could be reduced to 5 seconds using an in-plane resolution of (2×2) mm2, which equals a scan time reduction of more than 99% compared to the reference method. Conclusion Our results demonstrate that rapid 2D T1 quantification using a variable flip angle approach is feasible at 1.5T/3T/7T. It represents a valuable alternative for rapid T1 mapping due to the gain in speed versus conventional approaches. This progress may serve to enhance the capabilities of parametric MR based lesion detection and brain tissue characterization. PMID:24621588

Dieringer, Matthias A.; Deimling, Michael; Santoro, Davide; Wuerfel, Jens; Madai, Vince I.; Sobesky, Jan; von Knobelsdorff-Brenkenhoff, Florian; Schulz-Menger, Jeanette; Niendorf, Thoralf

2014-01-01

60

Travelling Wave Magnetic Resonance Imaging at 3 Tesla  

E-print Network

Waveguides have been successfully used to generate magnetic resonance images at 7 T with whole-body systems. The bore limits the magnetic resonance signal transmitted because its specific cut-off frequency is greater than the majority of resonant frequencies. This restriction can be overcome by using a parallel-plate waveguide whose cut-off frequency is zero for the transversal electric modes and it can propagate any frequency. To investigate the potential benefits for whole-body imaging at 3 T, we compare numerical simulations at 1.5 T, 3 T, 7 T, and 9 T via the propagation of the parallel-plate waveguide principal mode filled with a cylindrical phantom and two surface coils. B1 mapping was computed to investigate the feasibility of this approach at 3T. The point spread function method was used to measure the imager performance for the traveling-wave magnetic resonance imaging experiment. Human leg images were acquired to experimentally validate this approach. The principal mode shows very little field magni...

Vazquez, F; Marrufo, O; Rodriguez, A O

2013-01-01

61

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

Microsoft Academic Search

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

Toshiharu Nakai; Kayako Matsuo; Chikako Kato; Masako Matsuzawa; Tomohisa Okada; Gary H Glover; Tetsuo Moriya; Toshio Inui

1999-01-01

62

Superconducting Nb3Ge for high-field magnets  

NASA Technical Reports Server (NTRS)

Superconducting Nb3Ge tape conductors 5 to 10 m long were fabricated by chemical vapor deposition. Such tapes could be used in high-field magnet applications. Average tape properties set the upper performance limit of a magnet at 17 teslas (4.2 K). Highest critical-current densities obtained in thin and layered films set the upper performance limit at 20 teslas (4.2 K).

Braginski, A. I.; Daniel, M. R.; Roland, C. W.; Woollam, J. A.

1978-01-01

63

Heat Capacity Measurements in Pulsed Magnetic Fields  

SciTech Connect

The new NHMFL 60T quasi-continuous magnet produces a flat-top field for a period of 100 ms at 60 Tesla, and for longer time at lower fields, e.g. 0.5 s at 45 Tesla. We have developed for the first time the capability to measure heat capacity at very high magnetic fields in the NHMFL 60T quasi-continuous magnet at LANL, using a probe built out of various plastic materials. The field plateau allows us to utilize a heat-pulse method to obtain heat capacity data. Proof-of-principle heat capacity experiments were performed on a variety of correlated electron systems. Both magnet performance characteristics and physical properties of various materials studied hold out a promise of wide application of this new tool.

Jaime, M.; Movshovich, R.; Sarrao, J.L.; Kim, J.; Stewart, G.; Beyermann, W.P.; Canfield, P.C.

1998-10-23

64

Low Temperature Thermometry in High Magnetic Fields  

Microsoft Academic Search

The calibration and reproducibilty of various commercial and homemade thermometers have been investigated over a temperature range from 20 mK to 4.2 K and magnetic field strength from 0 to 16 Tesla. The performance of resistance thermometers made of different materials varies widely as a function of magnetic field. One type (Scientific Instruments RO600) is found to have a relatively

Gary G. Ihas; L. Frederick; J. P. McFarland

1998-01-01

65

Magnetic Field Safety Magnetic Field Safety  

E-print Network

Magnetic Field Safety Training #12;Magnetic Field Safety Strong Magnetic Fields exist around energized magnets. High magnetic fields alone are a recognized hazard only for personnel with certain medical conditions such as pacemakers, magnetic implants, or embedded shrapnel. In addition, high magnetic

McQuade, D. Tyler

66

Human cardiac 31P magnetic resonance spectroscopy at 7 tesla  

PubMed Central

Purpose Phosphorus magnetic resonance spectroscopy (31P-MRS) affords unique insight into cardiac energetics but has a low intrinsic signal-to-noise ratio (SNR) in humans. Theory predicts an increased 31P-MRS SNR at 7T, offering exciting possibilities to better investigate cardiac metabolism. We therefore compare the performance of human cardiac 31P-MRS at 7T to 3T, and measure T1s for 31P metabolites at 7T. Methods Matched 31P-MRS data were acquired at 3T and 7T, on nine normal volunteers. A novel Look-Locker CSI acquisition and fitting approach was used to measure T1s on six normal volunteers. Results T1s in the heart at 7T were: phosphocreatine (PCr) 3.05 ± 0.41s, ?-ATP 1.82 ± 0.09s, ?-ATP 1.39 ± 0.09s, ?-ATP 1.02 ± 0.17s and 2,3-DPG (2,3-diphosphoglycerate) 3.05 ± 0.41s (N = 6). In the field comparison (N = 9), PCr SNR increased 2.8× at 7T relative to 3T, the Cramer-Ráo uncertainty (CRLB) in PCr concentration decreased 2.4×, the mean CRLB in PCr/ATP decreased 2.7× and the PCr/ATP SD decreased 2×. Conclusion Cardiac 31P-MRS at 7T has higher SNR and the spectra can be quantified more precisely than at 3T. Cardiac 31P T1s are shorter at 7T than at 3T. We predict that 7T will become the field strength of choice for cardiac 31P-MRS. Magn Reson Med 72:304–315, 2014. © 2013 The Authors. Magnetic Resonance in Medicine Published by Wiley Periodicals, Inc. on behalf of International Society of Medicine in Resonance. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited. PMID:24006267

Rodgers, Christopher T; Clarke, William T; Snyder, Carl; Vaughan, J Thomas; Neubauer, Stefan; Robson, Matthew D

2014-01-01

67

7 Tesla magnetic resonance imaging: a closer look at substantia nigra anatomy in Parkinson's disease.  

PubMed

A hallmark of Parkinson's disease (PD) is the progressive neurodegeneration of dopaminergic neurons in the substantia nigra pars compacta (SNc). Dopaminergic denervation is commonly imaged using radiotracer imaging in target structures such as the striatum. Until recently, imaging made only a modest contribution to detecting neurodegenerative changes in the substantia nigra (SN) directly. Histologically, the SN is subdivided into the ventral pars reticulata and the dorsal pars compacta, which is composed of dopaminergic neurons. In humans, dopaminergic neurons, which are known to accumulate neuromelanin, form clusters of cells (nigrosomes) that penetrate deep into the SN pars reticulata (SNr). The SNr contains higher levels of iron than the SNc in normal subjects. Neuromelanin and T2*-weighted imaging therefore better detect the SNc and the SNr, respectively. The development of ultra-high field 7 Tesla (7T) magnetic resonance imaging (MRI) provided the increase in spatial resolution and in contrast that was needed to detect changes in SN morphology. 7T MRI allows visualization of nigrosome-1 as a hyperintense signal area on T2*-weighted images in the SNc of healthy subjects and its absence in PD patients, probably because of the loss of melanized neurons and the increase of iron deposition. This review is designed to provide a better understanding of the correspondence between the outlines and subdivisions of the SN detected using different MRI contrasts and the histological organization of the SN. The recent findings obtained at 7T will then be presented in relation to histological knowledge. PMID:25308960

Lehéricy, Stéphane; Bardinet, Eric; Poupon, Cyril; Vidailhet, Marie; François, Chantal

2014-11-01

68

Functional magnetic resonance imaging at 0.2 Tesla  

Microsoft Academic Search

Functional magnetic resonance imaging of healthy human volunteers was carried out at 0.2 T, using proton-density weighted (TE = 24 ms) spin-echo imaging, in order to eliminate any contribution from the blood oxygenation-level dependent (BOLD) effect. The purpose of the study was to verify the existence of a proton-density change contribution to spin-echo functional magnetic resonance imaging (fMRI) data. Results

P. W Stroman; K. L Malisza; M Onu

2003-01-01

69

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

70

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

71

[Effects of the magnetic field in magnetic resonance imaging on 15 tested cardiac valve prostheses].  

PubMed

The effects of static magnetic fields used in MR imaging at 0.5 Tesla have been studied on 15 different types of cardiac valves. The displacement of the valves was insignificant at 0.5 Tesla. No significant heating effects was observed with the standard sequences used in cardiac imaging. The image artefacts remain confined to the area immediately surrounding these different valves. It seems possible to perform MRI examinations on patient with the prosthetic heart valves without any risk. PMID:3795175

Hassler, M; Le Bas, J F; Wolf, J E; Contamin, C; Waksmann, B; Coulomb, M

1986-10-01

72

Magnetic field decay in model SSC dipoles  

SciTech Connect

We have observed that some of our model SSC dipoles have long time constant decays of the magnetic field harmonics with amplitudes large enough to result in significant beam loss, if they are not corrected. The magnets were run at constant current at the SSC injection field level of 0.3 tesla for one to three hours and changes in the magnetic field were observed. One explanation for the observed field decay is time dependent superconductor magnetization. Another explanation involves flux creep or flux flow. Data are presented on how the decay changes with previous flux history. Similar magnets with different Nb-Ti filament spacings and matrix materials have different long time field decay. A theoretical model using proximity coupling and flux creep for the observed field decay is discussed. 10 refs., 5 figs., 2 tabs.

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

1988-08-01

73

Value of 3 Tesla diffusion-weighted magnetic resonance imaging for assessing liver fibrosis  

PubMed Central

Background Limited data are available regarding the role of magnetic resonance imaging (MRI), particularly the new generation 3 Tesla technology, and especially diffusion-weighted imaging (DWI) in predicting liver fibrosis. The aim of our pilot study was to assess the clinical performance of the apparent diffusion coefficient (ADC) of liver parenchyma for the assessment of liver fibrosis in patients with non-alcoholic fatty liver disease (NAFLD). Methods 18 patients with biopsy-proven NAFLD underwent DWI with 3 Tesla MRI. DWI was performed with single-shot echo-planar technique at b values of 0-500 and 0-1000 s/mm2. ADC was measured in four locations in the liver and the mean ADC value was used for analysis. Staging of fibrosis was performed according to the METAVIR system. Results The median age of patients was 52 years (range 23-73). The distribution of patients in different fibrosis stages was: 0 (n=1), 1 (n=7), 2 (n=1), 3 (n=5), 4 (n=4). Fibrosis stage was poorly associated with ADC at b value of 0-500 s/mm2 (r= -0.30, P=0.27). However it was significantly associated with ADC at b value of 0-1000 s/mm2 (r= -0.57, P=0.01). For this b value (0-1000 s/mm2) the area under receiver-operating characteristic curve was 0.93 for fibrosis stage ?3 and the optimal ADC cut-off value was 1.16 ×10-3 mm2/s. Conclusion 3 Tesla DWI can possibly predict the presence of advanced fibrosis in patients with NAFLD. PMID:25608776

Papalavrentios, Lavrentios; Sinakos, Emmanouil; Chourmouzi, Danai; Hytiroglou, Prodromos; Drevelegas, Konstantinos; Constantinides, Manos; Drevelegas, Antonios; Talwalkar, Jayant; Akriviadis, Evangelos

2015-01-01

74

Correlating Hemodynamic Magnetic Resonance Imaging with high-field Intracranial Vessel Wall Imaging in Stroke  

PubMed Central

Vessel wall magnetic resonance imaging at ultra-high field (7 Tesla) can be used to visualize vascular lesions noninvasively and holds potential for improving stroke-risk assessment in patients with ischemic cerebrovascular disease. We present the first multi-modal comparison of such high-field vessel wall imaging with more conventional (i) 3 Tesla hemodynamic magnetic resonance imaging and (ii) digital subtraction angiography in a 69-year-old male with a left temporal ischemic infarct. PMID:25426229

Langdon, Weston; Donahue, Manus J.; van der Kolk, Anja G.; Rane, Swati; Strother, Megan K.

2014-01-01

75

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

76

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

Microsoft Academic Search

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

Kayako Matsuo; Chikako Kato; Shigeki Tanaka; Takeshi Sugio; Masako Matsuzawa; Toshio Inui; Tetsuo Moriya; Gary H Glover; Toshiharu Nakai

2001-01-01

77

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

78

Investigation of Reinforced, Magnet-Coil Support Shells for the NHMFL 100 Tesla Non-Destructive Magnet  

Microsoft Academic Search

The National High Magnetic Field Laboratory (NHMFL) at Los Alamos, New Mexico, and Tallahassee, Florida has undertaken an effort to design and build a 100 T non-destructive magnet. The magnet will be located in Los Alamos and will be used for studying properties of materials at high magnetic fields. The goal for the 100 T magnet is a duration of

J. R. Sims; J. B. Schillig; H. Coe; C. N. Ammerman

2006-01-01

79

Efficacy in Microbial Sterilization of Pulsed Magnetic Field Treatment  

Technology Transfer Automated Retrieval System (TEKTRAN)

Sterilization effects of the pulsed magnetic field with a maximum intensity of 11.37 Tesla were investigated on Escherichia coli AS 1.129, Staphylococcus aureus AS 1.89, Saccharomyces cerevisiae ATTC 7552 and Bacillus subtilis AS 1.921. The well-regulated fluctuations of sterilization effects with m...

80

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

81

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

82

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.

83

NATIONAL HIGH MAGNETIC FIELD LABORATORY REPORTSSUMMER EDITION VOLUME 13 N0. 3 2006  

E-print Network

UPPort scientists neWs FroM tHe dc FieLd FaciLitY: QUantUM HaLL eFFect in graPHene at HigH Magnetic FieLds ed NEARING COMPLETION 14 NEWS FROM THE DC FIELD FACILITY QuantuM Hall effect In grapHene at HIgH MagnetIc f of magnets (DC, superconductors, 45 Tesla hybrid, 100 Tesla short pulse...etc.), and for a combination

Weston, Ken

84

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,

85

What are 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 Magnetic Math booklet; this booklet can be found on the Space Math@NASA website.

86

Magnetic field line Hamiltonian  

SciTech Connect

The basic properties of the Hamiltonian representation of magnetic fields in canonical form are reviewed. The theory of canonical magnetic perturbation theory is then developed and applied to the time evolution of a magnetic field embedded in a toroidal plasma. Finally, the extension of the energy principle to tearing modes, utilizing the magnetic field line Hamiltonian, is outlined.

Boozer, A.H.

1985-02-01

87

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

88

Firefly flashing under strong static magnetic field.  

PubMed

Firefly flashing has been the subject of numerous scientific investigations. Here we present in vivo flashes from male specimens of three species of fireflies-two Japanese species Luciola cruciata, Luciola lateralis and one Indian species Luciola praeusta-positioned under a superconducting magnet. When the OFF state of the firefly becomes long after flashing in an immobile state under the strong static magnetic field of strength 10 Tesla for a long time, which varies widely from species to species as well as from specimen to specimen, the effect of the field becomes noticeable. The flashes in general are more rapid, and occasionally overlap to produce broad compound flashes. We present the broadest flashes recorded to date, and propose that the strong static magnetic field affects the neural activities of fireflies, especially those in the spent up or 'exhausted' condition. PMID:22131061

Barua, Anurup Gohain; Iwasaka, Masakazu; Miyashita, Yuito; Kurita, Satoru; Owada, Norio

2012-02-01

89

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

90

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

SciTech Connect

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 Nb{sub 3}Sn superconductor, has been built and tested. A record dipole filed of 14.7 Tesla has been achieved. Relevant features of the final assembly and tested results are discussed.

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

2001-06-15

91

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.

2012-08-03

92

Quantitative analysis of 3-Tesla magnetic resonance imaging in the differential diagnosis of breast lesions  

PubMed Central

The aim of this study was to investigate the value of quantitative 3-Tesla (3T) magnetic resonance (MR) assessment in the diagnosis of breast lesions. A total of 44 patients with breast lesions were selected. All the patients underwent MR plain scanning and T1 dynamic contrast-enhanced imaging. The vascular function parameters of the lesions, namely volume transfer constant (Ktrans), rate constant (Kep), extravascular extracellular volume fraction (Ve) and integrated area under the curve (iAUC), were acquired. These parameters were compared between benign and malignant breast lesions, and also among differential grades of invasive ductal carcinoma. The values of Ktrans, Kep and iAUC were significantly different between the benign and malignant tumors; however, the values of Ve in the benign and malignant tumors were not significantly different. The values of Ktrans, Kep and iAUC in invasive ductal carcinoma were significantly different between grade I and grade II, and between grade I and grade III; however, there was no significant difference between grade II and grade III. The Ve values in invasive ductal carcinoma did not significantly differ among grades I, II and III. Among the vascular function parameters, Ktrans exhibited the highest sensitivity and specificity in the differentiation of benign and malignant lesions. Quantitative 3-T MR assessment is valuable in the diagnosis of benign and malignant breast lesions. It can also provide reference values for the differentiation of the histological grade of breast invasive ductal carcinoma.

MA, ZHEN-SHEN; WANG, DA-WEI; SUN, XIU-BIN; SHI, HAO; PANG, TAO; DONG, GUI-QING; ZHANG, CHENG-QI

2015-01-01

93

7 Tesla Magnetic Resonance Imaging to Detect Cortical Pathology in Multiple Sclerosis  

PubMed Central

Background Neocortical lesions (NLs) are an important pathological component of multiple sclerosis (MS), but their visualization by magnetic resonance imaging (MRI) remains challenging. Objectives We aimed at assessing the sensitivity of multi echo gradient echo (ME-GRE) T2*-weighted MRI at 7.0 Tesla in depicting NLs compared to myelin and iron staining. Methods Samples from two MS patients were imaged post mortem using a whole body 7T MRI scanner with a 24-channel receive-only array. Isotropic 200 micron resolution images with varying T2* weighting were reconstructed from the ME-GRE data and converted into R2* maps. Immunohistochemical staining for myelin (proteolipid protein, PLP) and diaminobenzidine-enhanced Turnbull blue staining for iron were performed. Results Prospective and retrospective sensitivities of MRI for the detection of NLs were 48% and 67% respectively. We observed MRI maps detecting only a small portion of 20 subpial NLs extending over large cortical areas on PLP stainings. No MRI signal changes suggestive of iron accumulation in NLs were observed. Conversely, R2* maps indicated iron loss in NLs, which was confirmed by histological quantification. Conclusions High-resolution post mortem imaging using R2* and magnitude maps permits detection of focal NLs. However, disclosing extensive subpial demyelination with MRI remains challenging. PMID:25303286

van Gelderen, Peter; Merkle, Hellmuth; Chen, Christina; Lassmann, Hans; Duyn, Jeff H.; Bagnato, Francesca

2014-01-01

94

Development of high magnetic fields for energy research  

SciTech Connect

This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The primary purpose of work has been to develop the scientific basis for DOE support of a program that would build a novel, nondestructive 100-tesla magnet that would be available as a user facility for cutting-edge, energy-related research and technology at very high magnetic fields.

Thompson, J.D.; Campbell, L.J.; Modler, R.; Movshovich, R. [Los Alamos National Lab., NM (United States); Lawrence, J.M. [Univ. of California, Irvine, CA (United States); Awschalom, D.D. [Univ. of California, Santa Barbara, CA (United States)

1998-11-01

95

Introduction to Magnetic Fields  

NSDL National Science Digital Library

This is an activity about magnetic fields. Learners will use various magnets, magnetic film, and a compass to see and illustrate what magnetic fields look like. This is the fourth activity as part of the iMAGiNETICspace: Where Imagination, Magnetism, and Space Collide educator's guide. Instructions for downloading the iBook educator's guide and the associated Transmedia book student guide are available at the resource link.

2013-05-06

96

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.

2014-09-18

97

Electricity and Magnetic Fields  

NSDL National Science Digital Library

The grand challenge for this legacy cycle unit is for students to design a way to help a recycler separate aluminum from steel scrap metal. In previous lessons, they have looked at how magnetism might be utilized. In this lesson, students think about how they might use magnets and how they might confront the problem of turning the magnetic field off. Through the accompanying activity students explore the nature of an electrically induced magnetic field and its applicability to the needed magnet.

VU Bioengineering RET Program,

98

Accelerator Quality HTS Dipole Magnet Demonstrator Designs for the EuCARD-2, 5 Tesla 40 mm Clear Aperture Magnet  

E-print Network

Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The EuCARD-2 work-package-10 is a collaborative push to take HTS materials into an accelerator quality demonstrator magnet. The demonstrator will produce 5 T standalone and between 17 T and 20 T, when inserted into the 100 mm aperture of Fresca-2 high field out-sert magnet. The HTS magnet will demonstrate the field strength and field quality that can be achieved. An effective quench detection and protection system will have to be developed to operate with the HTS superconducting materials. This paper presents a ReBCO magnet design using multi strand Roebel cable that develops a stand-alone field of 5 T in a 40 mm clear aperture and discusses the challenges associated with good field quality using this type of material. A selection of magnet designs is presented as result of a first phase of development.

Kirby, GA; Ballarino, A; Bottura, L; Chouika, N; Clement, S; Datskov, V; Fajardo, L; Fleiter, J; Gauthier, R; Gentini, L; Lambert, L; Lopes, M; Perez, JC; de Rijk, G; Rijllart, A; Rossi, L; ten Kate, H; Durante, M; Fazilleau, P; Lorin, C; Härö, E; Stenvall, A; Caspi, S; Marchevsky, M; Goldacker, W; Kario, A

2015-01-01

99

Circuits and Magnetic Fields  

NSDL National Science Digital Library

Students use the same method as in the activity from lesson 2 of this unit 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,

100

Magnetic fields at Neptune  

Microsoft Academic Search

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 = 10⁻⁵ gauss) was observed near closest approach, at a

N. F. Ness; M. H. Acuna; L. F. Burlaga; J. E. P. Connerney; R. P. Lepping; F. M. Neubauer

1989-01-01

101

The ESRF Miniature Pulsed Magnetic Field System  

SciTech Connect

We have developed a portable system to provide pulsed magnetic fields on the ESRF X-ray beamlines. The complete system consists of a power supply, liquid Helium and liquid Nitrogen dewars with a siphon each, control electronics and a double cryostat for separate coil and sample cooling. The liquid nitrogen cooled solenoids reach a maximum field of 30 Tesla for a total pulse duration of one milisecond. They are constructed for optimised cooling rate after the pulse to obtain a high duty cycle, the repetition rate is five pulses per minute at maximum field. The sample is cooled in an independent Helium flow cryostat which is inserted into the bore of the magnet. The flow cryostat has a temperature range from 5 to 250 Kelvin with a direct contact between the sample and Helium flow. This overview gives a general presentation of the system and we will show recent results.

Linden, Peter J. E. M. van der; Strohm, Cornelius; Roth, Thomas; Detlefs, Carsten; Mathon, Olivier [ESRF, 6 rue Jules Horowitz, F-38043 Grenoble (France)

2010-06-23

102

Magnetic Field Problem: Determining Current  

NSDL National Science Digital Library

A wire carrying an unknown current out of the page is shown above. You may also double-click in the animation to create a field line. Assume that the distance given is in cm and B is given in milli Tesla.

Christian, Wolfgang; Belloni, Mario

2007-03-03

103

Performance analysis of HD1: a 16 Tesla Nb3Sn dipole Magnet  

SciTech Connect

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 Nb{sub 3}Sn 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 current plateau appeared to be limited by 'stick slip' conductor motions. Diagnostics recorded quench origins and preload distributions. Cumulative deformation of the mechanical structure has been observed. Quench velocity in different field regions has been measured and compared with model predictions. The results obtained during the HD1 test are presented and discussed.

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

2005-06-01

104

The First Magnetic Fields  

E-print Network

We review current ideas on the origin of galactic and extragalactic magnetic fields. We begin by summarizing observations of magnetic fields at cosmological redshifts and on cosmological scales. These observations translate into constraints on the strength and scale magnetic fields must have during the early stages of galaxy formation in order to seed the galactic dynamo. We examine mechanisms for the generation of magnetic fields that operate prior during inflation and during subsequent phase transitions such as electroweak symmetry breaking and the quark-hadron phase transition. The implications of strong primordial magnetic fields for the reionization epoch as well as the first generation of stars is discussed in detail. The exotic, early-Universe mechanisms are contrasted with astrophysical processes that generate fields after recombination. For example, a Biermann-type battery can operate in a proto-galaxy during the early stages of structure formation. Moreover, magnetic fields in either an early genera...

Widrow, Lawrence M; Schleicher, Dominik; Subramanian, Kandaswamy; Tsagas, Christos G; Treumann, Rudolf A

2011-01-01

105

Solar magnetic fields - Extended.  

NASA Technical Reports Server (NTRS)

Spacecraft observations of the interplanetary magnetic field have revealed that almost always each solar rotation can be divided into sectors, within each of which the field has a predominant polarity toward the sun or away from the sun. Comparisons of this interplanetary magnetic sector pattern with observations of the photospheric magnetic field have revealed a similar solar magnetic pattern. The boundaries between solar magnetic sectors are approximately in the north-south direction over a wide range of latitudes on both sides of the equator. This solar magnetic sector structure can be described as a rotating dipole whose magnetic axis makes an angle of approximately 90 deg with the axis of rotation. Possible similarities between this solar-sector magnetism and the models derived from observations of stellar magnetism are discussed.

Wilcox, J. M.

1971-01-01

106

Mitigated-force carriage for high magnetic field environments  

DOEpatents

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

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

2014-05-20

107

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.

108

Cyclic Magnetic Field Reconnection  

NASA Astrophysics Data System (ADS)

Using a 2.5D electromagnetic particle-in-cell model, we study the magnetic field reconnection around the rotating plasma embedded in a magnetic field. Considering plasma rotation driven by an external electric field, it was found that during one rotational cycle, first the magnetic field energy increases and then decreases to its initial value. The magnetic reconnection occurring during this cycle plays two roles: first, it produces the closed magnetic islands and later on it reopens them to the initial form of magnetic field lines. Thus, the magnetic reconnection can be cyclically repeated in following plasma rotations. Simultaneously, the kinetic particle energy in the system increases due to dissipative processes in this externally driven plasma system. We think that this cyclic reconnection can operate around rapidly rotating stars and in the plasma vortices formed in unstable plasma flows.

Karlický, Marian

2009-02-01

109

ISOTHERMAL PHASE TRANSFORMATION CYCLING IN STEEL BY APPLICATION OF A HIGH MAGNETIC FIELD  

SciTech Connect

A phase transformation reversal via the application and removal of a large magnetic field was investigated. Because a large magnetic field can alter the phase equilibrium between paramagnetic austenite and ferromagnetic ferrite, volume fractions for each phase constituent can be modified at constant temperature by changing the magnetic field strength. In this research elevated temperature isothermal hold experiments were performed for 5160 steel. During the isothermal hold, the magnetic field was cycled between 0 and 30 Tesla. As companion experiments, temperature cycling and isothermal holds were performed without magnetic fields. The resulting microstructures were examined using optical and SEM metallography. These microstructures indicate that a portion of the microstructure experiences isothermal transformation cycling between austenite and ferrite due to the application and removal of the 30T (Tesla) magnetic field.

Ludtka, Gerard Michael [ORNL; Jaramillo, Roger A [ORNL; Ludtka, Gail Mackiewicz- [ORNL; Kisner, Roger A [ORNL; Wilgen, John B [ORNL

2007-01-01

110

Magnetic Field Problem: Determining Magnetic Fields  

NSDL National Science Digital Library

Two wires with current flowing through them perpendicular to the page are shown (position is given in meters and the integral is given in 10-10 Tesla-meters). Also shown is a choice of two detectors that displays the integral, . Choose a detector and observe readings. You may drag a detector from its original position if you wish.

Christian, Wolfgang; Belloni, Mario

2007-03-03

111

Relativistic and Nonrelativistic Descriptions of Electron Energy Levels in a Static Magnetic Field  

E-print Network

The physical consequences of the relativistic and nonrelativistic approaches to describe the energy levels of electrons which propagate in a static homogeneous magnetic field are considered. It is shown that for a given strength of the magnetic field, the quantized energy levels of the electrons calculated by nonrelativistic and relativistic equations differ substantially, up to few orders of magnitude for a magnetic field of about 1 Tesla. Experimental verification to resolve the discrepancy would be very welcome.

H. J. Schreiber; N. B. Skachkov

2008-03-28

112

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. PMID:23346987

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

2012-01-01

113

Numerical field simulation for parallel transmission in MRI at 7 tesla  

E-print Network

Parallel transmission (pTx) is a promising improvement to coil design that has been demonstrated to mitigate B1* inhomogeneity, manifest as center brightening, for high-field magnetic resonance imaging (MRI). Parallel ...

Bernier, Jessica A. (Jessica Ashley)

2011-01-01

114

Magnetic field generator  

DOEpatents

A magnetic field generating device provides a useful magnetic field within a specific retgion, while keeping nearby surrounding regions virtually field free. By placing an appropriate current density along a flux line of the source, the stray field effects of the generator may be contained. One current carrying structure may support a truncated cosine distribution, and it may be surrounded by a current structure which follows a flux line that would occur in a full coaxial double cosine distribution. Strong magnetic fields may be generated and contained using superconducting cables to approximate required current surfaces.

Krienin, Frank (Shoreham, NY)

1990-01-01

115

Magnetic tunnel junction sensors with pTesla sensitivity for biomedical imaging  

NASA Astrophysics Data System (ADS)

Ultrasensitive magnetic field sensors at low frequencies are necessary for several biomedical applications. Suitable devices can be achieved by using large area magnetic tunnel junction sensors combined with permanent magnets to stabilize the magnetic configuration of the free layer and improve linearity. However, further increase in sensitivity and consequently detectivity are achieved by incorporating also soft ferromagnetic flux guides. A detailed study of tunnel junction sensors with variable areas and aspect ratios is presented in this work. In addition, the effect in the sensors transfer curve, namely in their coercivity and sensitivity, as a consequence of the incorporation of permanent magnets and flux guides is also thoroughly discussed. Using sensors with a tunnel magnetoresistance of ~200 %, incorporating both permanent magnets and flux guides sensitivities of 220-260 %/mT were obtained for high aspect ratio sensors, increasing to values larger than ~2000%/mT for large areas and low aspect ratio sensors. Measured noise levels of the final device at 10 Hz yield 3.9×10-17 V2/Hz, leading to an improved lowest detectable field of ~ 94 pT/ Hz0.5.

Cardoso, S.; Gameiro, L.; Leitao, D. C.; Cardoso, F.; Ferreira, R.; Paz, E.; Freitas, P. P.

2013-05-01

116

MAGNET ENGINEERING AND TEST RESULTS OF THE HIGH FIELD MAGNET R AND D PROGRAM AT BNL.  

SciTech Connect

The Superconducting Magnet Division at Brookhaven National Laboratory (BNL) has been carrying out design, engineering, and technology development of high performance magnets for future accelerators. High Temperature Superconductors (HTS) play a major role in the BNL vision of a few high performance interaction region (IR) magnets that would be placed in a machine about ten years from now. This paper presents the engineering design of a ''react and wind'' Nb{sub 3}Sn magnet that will provide a 12 Tesla background field on HTS coils. In addition, the coil production tooling as well as the most recent 10-turn R&D coil test results will be discussed.

COZZOLINO,J.; ANERELLA,M.; ESCALLIER,J.; GANETIS,G.; GHOSH,A.; GUPTA,R.; HARRISON,M.; JAIN,A.; MARONE,A.; MURATORE,J.; PARKER,B.; SAMPSON,W.; SOIKA,R.; WANDERER,P.

2002-08-04

117

THE INTERPLANETARY MAGNETIC FIELD  

Microsoft Academic Search

A new analysis of magnetic and concurrent plasma data collected from the ; space probes Pionecr 5, Explorer 10, and Mariner 2 yields a new model of the ; interplanetary magnetic field. It is hypothesized that the observed ; interplanetary field F\\/sub i\\/ is due to motion of the magnetometer relative to a ; negatively charged rotating sun from which

V. A. BAILEY

1963-01-01

118

Cosmic Magnetic Fields  

Microsoft Academic Search

Most of the visible matter in the Universe is in a plasma state, or more specifically is composed of ionized or partially ionized gas permeated by magnetic fields. Thanks to recent advances on the theory and detection of cosmic magnetic fields there has been a worldwide growing interest in the study of their role on the formation of astrophysical sources

Elisabete M. de Gouveia Dal Pino; Dal Pino

2006-01-01

119

The solar magnetic field  

Microsoft Academic Search

The magnetic field of the Sun is the underlying cause of the many diverse phenomena combined under the heading of solar activity. Here we describe the magnetic field as it threads its way from the bottom of the convection zone, where it is built up by the solar dynamo, to the solar surface, where it manifests itself in the form

Sami K. Solanki; Bernd Inhester; Manfred Schüssler

2006-01-01

120

Sources of signal fluctuations in functional magnetic resonance imaging at 7 Tesla  

Microsoft Academic Search

High-field magnetic resonance imaging (MRI) systems allow for critical improvements in image signal-to-noise ratio (SNR), potentially leading to higher sensitivity and spatial resolution for functional MRI (fMRI). 3D segmented echo volumar imaging (EVI) has recently been proposed for high- resolution fMRI at ultra-high fields. It provides higher image SNR than standard 2D echo planar imaging (EPI), but is also thought

Joao P. F. Jorge; P. Figueiredo; W. van der Zwaag; J. P. Marques

2011-01-01

121

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

122

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

123

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

124

AC Heat capacity and magnetocaloric effect measurements for pulsed magnetic fields  

Microsoft Academic Search

A new calorimeter for measurements of the AC heat capacity and magnetocaloric effect of small samples in pulsed magnetic fields is discussed for the exploration of thermal and thermodynamic properties at temperatures down to 2 K. We tested the method up to \\\\mu 0H = 50 Tesla, but it could be extended to higher fields. For these measurements we used

Yoshimitsu Kohama; Christophe Marcenat; Thierry Klein; Marcelo Jaime

2010-01-01

125

Solar polar magnetic field  

NASA Astrophysics Data System (ADS)

The solar polar magnetic field has attracted the attention of researchers since the polar magnetic field reversal was revealed in the middle of the last century (Babcock and Livingston, 1958). The polar magnetic field has regularly reversed because the magnetic flux is transported from the sunspot formation zone owing to differential rotation, meridional circulation, and turbulent diffusion. However, modeling of these processes leads to ambiguous conclusions, as a result of which it is sometimes unclear whether a transport model is actual. Thus, according to the last Hinode data, the problem of a standard transport model (Shiota et al., 2012) consists in that a decrease in the polar magnetic flux in the Southern Hemisphere lags behind such a decrease in the flux in the Northern Hemisphere (from 2008 to June 2012). On the other hand, Svalgaard and Kamide (2012) consider that the asymmetry in the sign reversal simply results from the asymmetry in the emerging flux in the sunspot formation region. A detailed study of the polar magnetic flux evolution according to the Solar Dynamics Observatory (SDO) data for May 2010-December 2012 is illustrated in the present work. Helioseismic & Magnetic Imager (HMI) magnetic data in the form of a magnetic field component along the line of sight (the time resolution is 720 s) are used here. The magnetic fluxes in sunspot formation regions and at high latitudes have been compared.

Benevolenskaya, E. E.

2013-12-01

126

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. PMID:23870734

2013-01-01

127

ROLE FOR THE MAGNETIC FIELD IN THE RADIATION-INDUCED EFFLUX OF CALCIUM IONS FROM BRAIN TISSUE 'IN VITRO'  

EPA Science Inventory

Two independent laboratories have demonstrated that specific frequencies of electromagnetic radiation can cause a change in the efflux of calcium ions from brain tissue in vitro. Under a static magnetic field intensity of 38 microTesla (microT) due to the earth's magnetic field, ...

128

Detecting Exoplanetary Magnetic Fields  

NASA Astrophysics Data System (ADS)

Asymmetries in exoplanet transits are proving to be a useful tool for furthering our understanding of magnetic activity on both stars and planets outside our Solar System.Near-UV observations of the WASP-12 system have revealed asymmetries in the timing of the transit when compared with the optical light curve. A number of possible explanations have been suggested for this variation, including the presence of a magnetospheric bow shock arising from the interaction of the planet's magnetic field with the stellar wind from it's host star. Such observations provide the first method for directly detecting the presence of a magnetic field on exoplanets.The shape and size of such asymmetries is highly dependent on the structure of the host stars magnetic field at the time of observation. This implies we may observe highly varying near-UV transit light curves for the same system. These variations can then be used to learn about the geometry of the host star's magnetic field.In this presentation I will show modelling a bow shock around an exoplanet can help us to not only detect, but also also place constraints on the magnetic field strength of hot Jupiters. For some systems, such as HD 189733, we have maps of the surface magnetic field of the star at various epochs. I will also show how incorporating these maps into a stellar wind model, I can model the formation of a bow shock around the planet and hence demonstrate the variability of the near-UV transits.

Llama, Joe

2015-01-01

129

Eruptive solar magnetic fields  

Microsoft Academic Search

This paper considers the quasi-steady evolution of solar magnetic fields in response to gradual photospheric changes. Special interest is taken in the threshold of a sudden eruption in the solar atmosphere. The formal model of an evolving, force-free field dependent on two Cartesian coordinates has been treated previously, and we extend it to a field which is not force free

B. C. Low

1981-01-01

130

Brain of rats intoxicated with acrylamide: observation with 4.7 tesla magnetic resonance  

Microsoft Academic Search

When rats were injected intraperitoneally with acrylamide (50 mg\\/kg per day) for 8 days, all animals developed ataxia and weakness in the hindlimbs. On examining their brain with an ultrahigh-field (4.7 T) magnetic resonance (MR) spectrometer, the lateral ventricles on both sides and the third ventricle were dilated. The aqueduct and cisterns were also enlarged. The size of the cerebral

Yoshimasa Kinoshita; Hirohiko Matsumura; Hideki Igisu; Akira Yokota

2000-01-01

131

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.

132

Magnetic field dosimeter development  

SciTech Connect

In recent years there has been increased concern over potential health hazards related to exposure of personnel to magnetic fields. If exposure standards are to be established, then a means for measuring magnetic field dose must be available. To meet this need, the Department of Energy has funded development of prototype dosimeters at the Battelle Pacific Northwest Laboratory. This manual reviews the principle of operation of the dosimeter and also contains step-by-step instructions for its operation.

Lemon, D.K.; Skorpik, J.R.; Eick, J.L.

1980-09-01

133

Solar magnetic fields  

Microsoft Academic Search

Since the structuring and variability of the Sun and other stars are governed by magnetic fields, much of present-day stellar\\u000a physics centers around the measurement and understanding of the magnetic fields and their interactions. The Sun, being a prototypical\\u000a star, plays a unique role in astrophysics, since its proximity allows the fundamental processes to be explored in detail.\\u000a The PRL

J. O. Stenflo

2008-01-01

134

Solar magnetic fields  

Microsoft Academic Search

This paper is a review of our observational knowledge on solar magnetic fields. In Section 1 we make an attempt to summarize all observations of the general magnetic field (m.f.) of the Sun. Section 2 deals with the local m.f. at low latitudes and their connection with some features on the disk. The m.f. of sunspots and their peculiar character

A. Severny

1964-01-01

135

TESLA Report 1998-28 TESLA Report 1998-28  

E-print Network

TESLA Report 1998-28 #12;TESLA Report 1998-28 #12;TESLA Report 1998-28TESLA Report 1998-28TESLA Report 1998-28 Page 3 TESLA Report 1998-28 Page 1 #12;TESLA Report 1998-28TESLA Report 1998-28TESLA Report 1998-28 Page 4 TESLA Report 1998-28 Page 2 #12;TESLA Report 1998-28TESLA Report 1998-28TESLA

136

An active antenna for ELF magnetic fields  

NASA Technical Reports Server (NTRS)

The work of Nikola Tesla, especially that directed toward world-wide electrical energy distribution via excitation of the earth-ionosphere cavity resonances, has stimulated interest in the study of these resonances. Not only are they important for their potential use in the transmission of intelligence and electrical power, they are important because they are an integral part of our natural environment. This paper describes the design of a sensitive, untuned, low noise active antenna which is uniquely suited to modern earth-ionosphere cavity resonance measurements employing fast-Fourier transform techniques for near-real-time data analysis. It capitalizes on a little known field-antenna interaction mechanism. Recently, the authors made preliminary measurements of the magnetic fields in the earth-ionosphere cavity. During the course of this study, the problem of designing an optimized ELF magnetic field sensor presented itself. The sensor would have to be small, light weight (for portable use), and capable of detecting the 5-50 Hz picoTesla-level signals generated by the natural excitations of the earth-ionosphere cavity resonances. A review of the literature revealed that past researchers had employed very large search coils, both tuned and untuned. Hill and Bostick, for example, used coils of 30,000 turns wound on high permeability cores of 1.83 m length, weighing 40 kg. Tuned coils are unsuitable for modern fast-Fourier transform data analysis techniques which require a broad spectrum input. 'Untuned' coils connected to high input impedance voltage amplifiers exhibit resonant responses at the resonant frequency determined by the coil inductance and the coil distributed winding capacitance. Also, considered as antennas, they have effective areas equal only to their geometrical areas.

Sutton, John F.; Spaniol, Craig

1994-01-01

137

TESLA'S VISION OF THE WIRELESS GLOBAL COMMUNICATIONS  

E-print Network

to align with the electric field. The Inventions, Researches and Writings of Nikola Tesla #12;March 12TESLA'S VISION OF THE WIRELESS GLOBAL COMMUNICATIONS Ljiljana Trajkovi Communication Networks;March 12, 2004 Kwantlen College Ljiljana Trajkovic, Simon Fraser University 2 Road map Tesla in 1890's

Trajkovic, Ljiljana

138

Transport Studies in HSX at 1 Tesla  

NASA Astrophysics Data System (ADS)

To further investigate the effect of quasi-symmetry on neoclassical and anomalous transport, the HSX stellarator has recently begun regular operations at a magnetic field strength of 1 Tesla. Transport studies at 0.5 Tesla demonstrate that the electron thermal diffusivity is a factor of two smaller in the core for the Quasi-Helically Symmetric (QHS) configuration as compared to the configuration with the symmetry intentionally degraded (Mirror) due to a reduction in neoclassical transport [1]. Thermal transport analysis was complicated at 0.5 Tesla by the presence of an ECH driven suprathermal electron population, which is reduced in the higher density plasmas possible at 1 Tesla. It has also been observed that, for an identical injected power, the central temperature is double that of Mirror, with the same line averaged density in each case. A transport analysis will be presented showing the effect of higher field strength, density and injected power on electron thermal diffusivity in QHS and Mirror. This work is supported by DOE Grant DE-FG02-93ER54222. [1] J.M. Canik et al., Phys. Rev. Letters 98, 085002 (2007)

Lore, J.; Anderson, D. T.; Canik, J. M.; Likin, K. M.; Talmadge, J. N.; Zhai, K.

2007-11-01

139

Detection of Lung Tumors in Mice Using a 1-Tesla Compact Magnetic Resonance Imaging System  

PubMed Central

Due to their small size, lung tumors in rodents are typically investigated using high-field magnetic resonance (MR) systems (4.7 T or higher) to achieve higher signal-to-noise ratios, although low-field MR systems are less sensitive to susceptibility artifacts caused by air in the lung. We investigated the feasibility of detecting lung tumors in living, freely breathing mice with a 1-T compact permanent magnet MR system. In total, 4 mice were used, and MR images of mouse lungs were acquired using a T1-weighted three-dimensional fast low-angle shot sequence without cardiac or respiratory gating. The delineation and size of lung tumors were assessed and compared with histopathological findings. Submillimeter lesions were demonstrated as hyperintense, relative to the surrounding lung parenchyma, and were delineated clearly. Among the 13 lesions validated in histopathological sections, 11 were detected in MR images; the MR detection rate was thus 84.6%. A strong correlation was obtained in size measurements between MR images and histological sections. Thus, a dedicated low-field MR system can be used to detect lung tumors in living mice noninvasively without gating. PMID:24743153

Wang, Fang; Akashi, Ken; Murakami, Yoshinori; Inoue, Yusuke; Furuta, Toshihiro; Yamada, Haruyasu; Ohtomo, Kuni; Kiryu, Shigeru

2014-01-01

140

Magnetic Field Problem: Current  

NSDL National Science Digital Library

A cross section of a circular wire loop carrying an unknown current is shown above. The arrows represent the direction of the magnetic field. The color of the arrows represents the magnitude of the field with magnitude increasing as the color changes from blue to green to red to black. You can double-click in the animation to add magnetic field lines, click-drag the center of the loop to reposition it, and click-drag the top or bottom of the loop to change its size.

Wolfgang Christian

141

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

142

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

143

Magnetic field-induced superconductivity in the ferromagnet URhGe.  

PubMed

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. PMID:16123293

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

2005-08-26

144

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

145

Spatial distortion due to field inhomogeneity in 3.0 tesla intraoperative MRI.  

PubMed

We describe a 14-year-old boy with a pilocytic astrocytoma of the left caudate head. Preoperative localization MR imaging (MRI) was performed in the operating room, and spatial distortion was noted felt to be related to head positioning relative to the isocenter of the magnetic field. The distortion artifact was subtle enough to be difficult to detect, but large enough to change the location of the lesion potentially leading to a non-diagnostic stereotactic biopsy. Repeat imaging after changing the head position to allow scanning closer to the isocenter of the magnetic field showed decreased distortion, an improvement greater than that using the manufacturer's distortion correction algorithm on the initial images. Intraoperative MRI, and its requisite limitations in positioning, requires vigilance to detect possible distortion that could alter surgical outcomes if not identified and corrected prospectively. PMID:25196608

Choudhri, Asim F; Chin, Eric M; Klimo, Paul; Boop, Frederick A

2014-09-01

146

TESLA Report 1997-22 TESLA Report 1997-22  

E-print Network

TESLA Report 1997-22 #12;TESLA Report 1997-22 #12;TESLA Report 1997-22 #12;TESLA Report 1997-22 #12;TESLA Report 1997-22 #12;TESLA Report 1997-22 #12;TESLA Report 1997-22 #12;TESLA Report 1997-22 #12;TESLA Report 1997-22 #12;TESLA Report 1997-22 #12;TESLA Report 1997-22 #12;TESLA Report 1997-22 #12

147

Electrically silent magnetic fields.  

PubMed Central

There has been a significant controversy over the past decade regarding the relative information content of bioelectric and biomagnetic signals. In this paper we present a new, theoretical example of an electrically-silent magnetic field, based on a bidomain model of a cylindrical strand of tissue generalized to include off-diagonal components in the conductivity tensors. The physical interpretation of the off-diagonal components is explained, and analytic expressions for the electrical potential and the magnetic field are found. These expressions show that information not obtainable from electrical potential measurements can be obtained from measurements of the magnetic field in systems with conductivity tensors more complicated than those previously examined. PMID:3779008

Roth, B J; Wikswo, J P

1986-01-01

148

Magnetic Fields in Galaxies  

NASA Astrophysics Data System (ADS)

The origin and evolution of cosmic magnetic fields, their strength and structure in intergalactic space, their first occurrence in young galaxies, and their dynamical importance for galaxy evolution remain widely unknown. Radio synchrotron emission, its polarization and its Faraday rotation are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized radio synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 ?G) and in central starburst regions (50-100 ?G). Such fields are dynamically important; they can affect gas flows and drive gas inflows in central regions. Polarized radio emission traces ordered fields which can be regular or anisotropic turbulent, generated from isotropic turbulent fields by compression or shear. The strongest ordered fields of 10-15 ?G strength are generally found in interarm regions and follow the orientation of adjacent gas spiral arms. In galaxies with strong density waves, ordered (anisotropic turbulent) fields are also observed at the inner edges of the spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies, and in central regions of starburst galaxies. Ordered fields in interacting galaxies have asymmetric distributions and are an excellent tracer of past interactions between galaxies or with the intergalactic medium. Irregular galaxies host isotropic turbulent fields often of similar strength as in spiral galaxies, but only weak ordered fields. Faraday rotation measures (RM) of the diffuse polarized radio emission from the disks of several galaxies reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by a mean-field ? -? dynamo. So far no indications were found in external galaxies of large-scale field reversals, like the one in the Milky Way. Ordered magnetic fields are also observed in radio halos around edge-on galaxies out to large distances from the plane, with X-shaped patterns. In the outflow cone above a starburst region of NGC 253, RM data indicate a helical magnetic field.

Beck, Rainer

149

Solar magnetic fields and convection. IX - A primordial magnetic field  

Microsoft Academic Search

Observational evidence is reviewed in an attempt to decide between a reversing (dynamo) and a nonreversing primordial solar poloidal magnetic field. The data examined include Zeeman-effect measurements, measurements of gross magnetic fluxes in individual magnetic elements, determinations of average field strength, observations of polar-cap magnetic fields, eclipse observations of coronal structure, and observations of interplanetary-magnetic-field polarity reversals. It is suggested

J. H. Piddington

1977-01-01

150

Three-Tesla magnetic resonance elastography for hepatic fibrosis: Comparison with diffusion-weighted imaging and gadoxetic acid-enhanced magnetic resonance imaging  

PubMed Central

AIM: To evaluate the feasibility of 3-Tesla magnetic resonance elastography (MRE) for hepatic fibrosis and to compare that with diffusion-weighted imaging (DWI) and gadoxetic acid-enhanced magnetic resonance (MR) imaging. METHODS: Forty-two patients were included in the study. On MRE, mean stiffness values were measured on the elastograms in kilopascals. The apparent diffusion coefficient (ADC) of the liver was measured using DWI. On gadoxetic acid enhanced MR, the contrast enhancement index (CEI) was calculated as signal intensity (SI)post/SIpre, where SIpost is liver-to-muscle SI ratio on hepatobiliary phase images and SIpre is that on nonenhanced images. Correlation between aspartate aminotransferase to the platelet ratio index (APRI) and three MR parameters was assessed. Each MR parameter was compared between a hepatic fibrosis (HF) group and non-hepatic fibrosis (nHF) group. RESULTS: Liver stiffness showed strong positive correlation with APRI [Spearman correlation coeffiecient (r) = 0.773, P < 0.0001], while ADC and CEI showed weak or prominent negative correlation (r = -0.28 and -0.321, respectively). In the HF group, only liver stiffness showed strong correlation with APRI (r = 0.731, P < 0.0001). Liver stiffness, ADC, and APRI were significantly different between the HF group and nHF group. CONCLUSION: MRE at 3-Tesla could be a feasible method for the assessment of hepatic fibrosis. PMID:25516671

Park, Hee Sun; Kim, Young Jun; Yu, Mi Hye; Choe, Won Hyeok; Jung, Sung Il; Jeon, Hae Jeong

2014-01-01

151

Designing magnets with prescribed magnetic fields  

NASA Astrophysics Data System (ADS)

We present a novel design method capable of finding the magnetization densities that generate prescribed magnetic fields. The method is based on the solution to a simple variational inequality and the resulting designs have simple piecewise-constant magnetization densities. By this method, we obtain new designs of magnets that generate commonly used magnetic fields: uniform magnetic fields, self-shielding fields, quadrupole fields and sextupole fields. Further, it is worth noting that this method is not limited to the presented examples, and in particular, three-dimensional designs can be constructed in a similar manner. In conclusion, this novel design method is anticipated to have broad applications where specific magnetic fields are important for the performance of the devices.

Liu, Liping

2011-03-01

152

PBS: Tesla - Master of Lightning  

NSDL National Science Digital Library

This web site explores the life and legacy of Nikola Tesla, an important contributor to the field of electromagnetism. Although the significance of his work is often minimized, Tesla's work formed the basis of modern alternating current power systems and wireless transmission of energy. He was the first to receive a patent for the invention of the radio, though Marconi is more often given credit for the discovery. The web site includes interactive explorations of Tesla's key inventions and lesson plans for grades 6-12 on electric potential and conversion of electrical energy into mechanical energy. Users will also find selected articles on Tesla, timelines of electricity and radio, and a link to view selected Tesla patents.

2010-06-24

153

Detailing Radio Frequency Heating Induced by Coronary Stents: A 7.0 Tesla Magnetic Resonance Study  

PubMed Central

The sensitivity gain of ultrahigh field Magnetic Resonance (UHF-MR) holds the promise to enhance spatial and temporal resolution. Such improvements could be beneficial for cardiovascular MR. However, intracoronary stents used for treatment of coronary artery disease are currently considered to be contra-indications for UHF-MR. The antenna effect induced by a stent together with RF wavelength shortening could increase local radiofrequency (RF) power deposition at 7.0 T and bears the potential to induce local heating, which might cause tissue damage. Realizing these constraints, this work examines RF heating effects of stents using electro-magnetic field (EMF) simulations and phantoms with properties that mimic myocardium. For this purpose, RF power deposition that exceeds the clinical limits was induced by a dedicated birdcage coil. Fiber optic probes and MR thermometry were applied for temperature monitoring using agarose phantoms containing copper tubes or coronary stents. The results demonstrate an agreement between RF heating induced temperature changes derived from EMF simulations versus MR thermometry. The birdcage coil tailored for RF heating was capable of irradiating power exceeding the specific-absorption rate (SAR) limits defined by the IEC guidelines by a factor of three. This setup afforded RF induced temperature changes up to +27 K in a reference phantom. The maximum extra temperature increase, induced by a copper tube or a coronary stent was less than 3 K. The coronary stents examined showed an RF heating behavior similar to a copper tube. Our results suggest that, if IEC guidelines for local/global SAR are followed, the extra RF heating induced in myocardial tissue by stents may not be significant versus the baseline heating induced by the energy deposited by a tailored cardiac transmit RF coil at 7.0 T, and may be smaller if not insignificant than the extra RF heating observed under the circumstances used in this study. PMID:23185498

Santoro, Davide; Winter, Lukas; Müller, Alexander; Vogt, Julia; Renz, Wolfgang; Özerdem, Celal; Grässl, Andreas; Tkachenko, Valeriy; Schulz-Menger, Jeanette; Niendorf, Thoralf

2012-01-01

154

Monopole passband excitation by field emitters in 9-cell TESLA-type cavities  

NASA Astrophysics Data System (ADS)

We present an extension of the calculation of dipole-mode driven beam break-up instabilities, as calculated in [V. Volkov, Phys. Rev. ST Accel. Beams 12, 011301 (2009); PRABFM1098-440210.1103/PhysRevSTAB.12.011301V. Volkov, J. Knobloch, and A. Matveenko, Phys. Rev. ST Accel. Beams (to be published)PRABFM1098-4402], to the monopole fundamental mode passband. The excitation of these modes has been observed in 9-cell TESLA cavities on test stands without beam [G. Kreps , Proceedings of SRF2009 (HZB, Berlin, Germany, 2009), pp. 289-291] and the same effect has been observed in klystrons with high DC currents.

Volkov, V.; Knobloch, J.; Matveenko, A.

2010-08-01

155

On the Subjective Acceptance during Cardiovascular Magnetic Resonance Imaging at 7.0 Tesla  

PubMed Central

Purpose This study examines the subjective acceptance during UHF-CMR in a cohort of healthy volunteers who underwent a cardiac MR examination at 7.0T. Methods Within a period of two-and-a-half years (January 2012 to June 2014) a total of 165 healthy volunteers (41 female, 124 male) without any known history of cardiac disease underwent UHF-CMR. For the assessment of the subjective acceptance a questionnaire was used to examine the participants experience prior, during and after the UHF-CMR examination. For this purpose, subjects were asked to respond to the questionnaire in an exit interview held immediately after the completion of the UHF-CMR examination under supervision of a study nurse to ensure accurate understanding of the questions. All questions were answered with “yes” or “no” including space for additional comments. Results Transient muscular contraction was documented in 12.7% of the questionnaires. Muscular contraction was reported to occur only during periods of scanning with the magnetic field gradients being rapidly switched. Dizziness during the study was reported by 12.7% of the subjects. Taste of metal was reported by 10.1% of the study population. Light flashes were reported by 3.6% of the entire cohort. 13% of the subjects reported side effects/observations which were not explicitly listed in the questionnaire but covered by the question about other side effects. No severe side effects as vomiting or syncope after scanning occurred. No increase in heart rate was observed during the UHF-CMR exam versus the baseline clinical examination. Conclusions This study adds to the literature by detailing the subjective acceptance of cardiovascular magnetic resonance imaging examinations at a magnetic field strength of 7.0T. Cardiac MR examinations at 7.0T are well tolerated by healthy subjects. Broader observational and multi-center studies including patient cohorts with cardiac diseases are required to gain further insights into the subjective acceptance of UHF-CMR examinations. PMID:25621491

Klix, Sabrina; Els, Antje; Paul, Katharina; Graessl, Andreas; Oezerdem, Celal; Weinberger, Oliver; Winter, Lukas; Thalhammer, Christof; Huelnhagen, Till; Rieger, Jan; Mehling, Heidrun; Schulz-Menger, Jeanette; Niendorf, Thoralf

2015-01-01

156

Nuclear Magnetic Resonance and Magnetic Field Measurements  

NSDL National Science Digital Library

This laboratory is designed for students to become familiar with the principles and detection techniques of Nuclear Magnetic Resonance (NMR), examine the relationship between current and magnetic field in an electromagnet, and gain experience in the use of magnetic field measurement techniques.

2012-01-04

157

New developments in pulsed fields at the US National High Magnetic Field Laboratory  

SciTech Connect

Los Alamos National Laboratory is a member of a consortium (with Florida State University and the University of Florida) to operate the National High Magnetic Field Laboratory (NHMFL), with funding from the National Science Foundation and the State of Florida. Los Alamos provides unique resources for its component of NHMFL in the form of a 1.4 GW inertial storage motor-generator for high field pulsed magnets and infrastructure for fields generated by flux compression. The NHMFL provides a user facility open to all qualified users, develops magnet technology in association with the private sector, and advances science and technology opportunities. The magnets in service at Los Alamos are of three types. Starting with the pre-existing explosive flux compression capability in 1991, NHMFL added capacitor-driven magnets in December, 1992, and a 20 tesla superconducting magnet in January, 1993. The capacitor-driven magnets continue to grow in diversity and accessibility, with four magnet stations now available for several different magnet types. Two magnets of unprecedented size and strength are nearing completion of assembly and design, respectively. Under final assembly is a quasi-continuous magnet that contains 90 MJ of magnetic energy at full field, and being designed is a non-destructive 100 T magnet containing 140 MJ.

Campbell, L.J.; Parkin, D.M.; Rickel, D.G. [Los Alamos National Lab., NM (United States); Pernambuco-Wise, P. [Florida State Univ., Tallahassee, FL (United States)

1996-12-01

158

Semiconductor Crystal Growth in Static and Rotating Magnetic fields  

NASA Technical Reports Server (NTRS)

Magnetic fields have been applied during the growth of bulk semiconductor crystals to control the convective flow behavior of the melt. A static magnetic field established Lorentz forces which tend to reduce the convective intensity in the melt. At sufficiently high magnetic field strengths, a boundary layer is established ahead of the solid-liquid interface where mass transport is dominated by diffusion. This can have a significant effect on segregation behavior and can eliminate striations in grown crystals resulting from convective instabilities. Experiments on dilute (Ge:Ga) and solid solution (Ge-Si) semiconductor systems show a transition from a completely mixed convective state to a diffusion-controlled state between 0 and 5 Tesla. In HgCdTe, radial segregation approached the diffusion limited regime and the curvature of the solid-liquid interface was reduced by a factor of 3 during growth in magnetic fields in excess of 0.5 Tesla. Convection can also be controlled during growth at reduced gravitational levels. However, the direction of the residual steady-state acceleration vector can compromise this effect if it cannot be controlled. A magnetic field in reduced gravity can suppress disturbances caused by residual transverse accelerations and by random non-steady accelerations. Indeed, a joint program between NASA and the NHMFL resulted in the construction of a prototype spaceflight magnet for crystal growth applications. An alternative to the suppression of convection by static magnetic fields and reduced gravity is the imposition of controlled steady flow generated by rotating magnetic fields (RMF)'s. The potential benefits of an RMF include homogenization of the melt temperature and concentration distribution, and control of the solid-liquid interface shape. Adjusting the strength and frequency of the applied magnetic field allows tailoring of the resultant flow field. A limitation of RMF's is that they introduce deleterious instabilities above a critical magnetic field value. Growth conditions in which static magnetic fields rotational magnetic fields, and reduced gravitational levels can have a beneficial role will be described.

Volz, Martin

2004-01-01

159

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

160

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

161

Intra-operative MRI at 3.0 Tesla: A Moveable Magnet  

Microsoft Academic Search

\\u000a This paper presents the development and implementation of an intra-operative magnetic resonance imaging (ioMRI) program using\\u000a a moveable 3.0T magnet with a large working aperture.\\u000a \\u000a \\u000a Methods: A previously established prototype 1.5T ioMRI program based on a ceiling-mounted moveable magnet was upgraded to\\u000a 3.0T. The upgrade included a short, 1.73m, magnet with a large 70cm working aperture (IMRIS, Winnipeg, Canada), whole-room

Michael J. Lang; Alexander D. Greer; Garnette R. Sutherland

162

Mars Observer magnetic fields investigation  

Microsoft Academic Search

The magnetic fields experiment designed for the Mars Observer mission will provide definitive measurements of the Martian magnetic field from the transition and mapping orbits planned for the Mars Observer. The paper describes the instruments (which include a classical magnetometer and an electron reflection magnetometer) and techniques designed to investigate the nature of the Martian magnetic field and the Mars-solar

J. E. P. Connerney; P. Wasilewski; R. P. Lin; K. A. Anderson; C. W. Carlson; J. McFadden; D. W. Curtis; H. Reme; A. Cros; J. L. Médale; J. A. Sauvaud; C. d'Uston; S. J. Bauer; P. Cloutier; Michael Mayhew; N. F. Ness

1992-01-01

163

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

164

Magnetic field switchable dry adhesives.  

PubMed

A magnetic field controllable dry adhesive device is manufactured. The normal adhesion force can be increased or decreased depending on the presence of an applied magnetic field. If the magnetic field is present during the entire normal adhesion test cycle which includes both applying a preloading force and measuring the pulloff pressure, a decrease in adhesion is observed when compared to when there is no applied magnetic field. Similarly, if the magnetic field is present only during the preload portion of the normal adhesion test cycle, a decrease in adhesion is observed because of an increased stiffness of the magnetically controlled dry adhesive device. When the applied magnetic field is present during only the pulloff portion of the normal adhesion test cycle, either an increase or a decrease in normal adhesion is observed depending on the direction of the applied magnetic field. PMID:25588470

Krahn, Jeffrey; Bovero, Enrico; Menon, Carlo

2015-02-01

165

A new phantom and empirical formula for apparent diffusion coefficient measurement by a 3 Tesla magnetic resonance imaging scanner  

PubMed Central

The aim of this study was to create a new phantom for a 3 Tesla (3T) magnetic resonance imaging (MRI) device for the calculation of the apparent diffusion coefficient (ADC) using diffusion-weighted imaging (DWI), and to mimic the ADC values of normal and tumor tissues at various temperatures, including the physiological body temperature of 37°C. The phantom was produced using several concentrations of sucrose from 0 to 1.2 M, and the DWI was performed using various phantom temperatures. The accurate ADC values were calculated using the DWIs of the phantoms, and an empirical formula was developed to calculate the ADC values of the phantoms from an arbitrary sucrose concentration and arbitrary phantom temperature. The empirical formula was able to produce ADC values ranging between 0.33 and 3.02×10?3 mm2/sec, which covered the range of ADC values of the human body that have been measured clinically by 3T MRI in previous studies. The phantom and empirical formula developed in this study may be available to mimic the ADC values of the clinical human lesion by 3T MRI. PMID:25013504

HARA, MARINA; KURODA, MASAHIRO; OHMURA, YUICHI; MATSUZAKI, HIDENOBU; KOBAYASHI, TOMOKI; MURAKAMI, JUN; KATASHIMA, KAZUNORI; ASHIDA, MASAKAZU; OHNO, SEIICHIRO; ASAUMI, JUN-ICHI

2014-01-01

166

Apparatus and method for magnetically processing a specimen  

SciTech Connect

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

167

[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

168

Proton Density-Weighted Functional Magnetic Resonance Imaging at 0.35 Tesla  

Microsoft Academic Search

Functional magnetic resonance imaging of healthy human volunteers was carried out at 0.35T MRI system, using proton-density weighted turbo spin-echo imaging. It aims at verifying the proton-density change contribution to spin-echo functional magnetic resonance imaging. And try to get better effect of fMRI studies at 0.35T MRI system. Results demonstrated that signal intensity changes in motor area of the brain

Ping. Yang; Jinxing. Wang; Yuesheng Chao; Guang Lu; Jinquan Shi

2008-01-01

169

Influence of strong static magnetic field on human cancer HT 1080 cells  

NASA Astrophysics Data System (ADS)

The aim of this study was to investigate strong uniform magnetic field influence on the human cancer cells HT 1080. The cells were treated with magnetic field of intensity 1,16 Tesla and with anticancer agent - cis-platinum 0.025 mg/ml or vincristinum 2-3 ng/ml. The intact and the treated cell samples were incubated in a medium with acridine orange (AO). The magnetic field after 15 minutes of influence significantly increased cytoplasmic red fluorescence. Increased AO accumulation in lysosomes suggested to cancer cell metabolic activity stimulation.

Rodins, Juris; Korhovs, Vadims; Freivalds, Talivaldis; Buikis, Indulis; Ivanova, Tatjana

2001-10-01

170

Magnetic-field-induced Heisenberg to XY crossover in a quasi-2D quantum antiferromagnet  

NASA Astrophysics Data System (ADS)

The magnetic-field-dependent ordering temperature of the quasi-2D quantum Heisenberg antiferromagnet (QHAF) Cu(pz)2(ClO4)2 was determined by calorimetric measurement in applied dc fields up to 33 tesla. The magnetic phase diagram shows a round maximum at 5.95 K and 17.5 T (at ? 1/3 of its saturation field), a 40 percent enhancement of the ordering temperature above the zero field value of 4.25 K. The enhancement and reentrance are consistent with predictions of a field-induced Heisenberg to XY crossover behavior for an ideal 2D QHAF system.

Fortune, N. A.; Hannahs, S. T.; Landee, C. P.; Turnbull, M. M.; Xiao, F.

2014-12-01

171

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

172

[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

173

Functional Magnetic Resonance Imaging in a Low-Field Intraoperative Scanner  

Microsoft Academic Search

Background: Functional magnetic resonance imaging (fMRI) has been used for preoperative planning and intraoperative surgical navigation. However, most experience to date has been with preoperative images acquired on high-field echoplanar MRI units. We explored the feasibility of acquiring fMRI of the motor cortex with a dedicated low-field intraoperative MRI (iMRI). Methods: Five healthy volunteers were scanned with the 0.12-tesla PoleStar

Michael Schulder; Hooman Azmi; Bharat Biswal

2003-01-01

174

BTA Magnet Field Map Archive and MAD Model  

SciTech Connect

This note publishes some and information that has resided in private files. The attached tables were provided by Joseph Skelly from his archives. They show magnetic field measurements versus excitation current for the Booster to AGS transfer line quadrupoles and dipoles based on field measurements [we believe] were done by the Magnet Division. Also given are Ed Blesser's fifth order fits of field versus current. The results are given in 'Tesla' or T-M/M. These tables are attached to provide an archive of this data. The MAD model of the BTA line does have the same values as shown in the attached fits so the transfer was correct. MAD uses as its 'gradient' for quads Tesla per meter normalized to rigidity [B-rho]. The model of the BTA line in use uses the T-M/M given in the tables divided by the length to give T M which is then normalized by Brho. Thus, the input to the model appears to be correct. The original model is also attached as part of a memo by Skelly describing it.

Glenn,J.W.

2008-04-01

175

Magnetostriction and magnetic texture to 100.75 Tesla in frustrated SrCu2(BO3)2  

PubMed Central

Strong geometrical frustration in magnets leads to exotic states such as spin liquids, spin supersolids, and complex magnetic textures. SrCu2(BO3)2, a spin-1/2 Heisenberg antiferromagnet in the archetypical Shastry–Sutherland lattice, exhibits a rich spectrum of magnetization plateaus and stripe-like magnetic textures in applied fields. The structure of these plateaus is still highly controversial due to the intrinsic complexity associated with frustration and competing length scales. We discover magnetic textures in SrCu2(BO3)2 via magnetostriction and magnetocaloric measurements in fields up to 100.75 T. In addition to observing low-field fine structure with unprecedented resolution, the data also reveal lattice responses at 73.6 T and at 82 T that we attribute, using a controlled density matrix renormalization group approach, to a unanticipated 2/5 plateau and to the long-predicted 1/2 plateau.

Jaime, Marcelo; Daou, Ramzy; Crooker, Scott A.; Weickert, Franziska; Uchida, Atsuko; Feiguin, Adrian E.; Batista, Cristian D.; Dabkowska, Hanna A.; Gaulin, Bruce D.

2012-01-01

176

A 2 Tesla Full Scale High Performance Periodic Permanent Magnet Model for Attractive (228 KN) and repulsive Maglev  

NASA Technical Reports Server (NTRS)

Two 214.5 cm. long high performance periodic (26 cm period) permanent magnet half-assemblies were designed and constructed for use as a wiggler using Nd-B-Fe and vanadium permendur as hard and soft magnetic materials by Field Effects, a division of Intermagnetics General Corporation. Placing these assemblies in a supporting structure with a 2.1 cm pole to pole separation resulted in a periodic field with a maximum value of 2.04 T. This is believed to be the highest field ever achieved by this type of device. The attractive force between the two 602 kg magnet assemblies is 228 kN, providing enough force for suspension of a 45,500 kg vehicle. If used in an attractive maglev system with an appropriate flat iron rail, one assembly will generate the same force with a gap of 1.05 cm leading to a lift to weight ratio of 38.6, not including the vehicle attachment structure. This permanent magnet compares well with superconducting systems which have lift to weight ratios in the range of 5 to 10. This paper describes the magnet assemblies and their measured magnetic performance. The measured magnetic field and resulting attractive magnetic force have a negative spring characteristic. Appropriate control coils are necessary to provide stable operation. The estimated performance of the assemblies in a stable repulsive mode, with eddy currents in a conducting guideway, is also discussed.

Stekly, Z. J. J.; Gardner, C.; Domigan, P.; Baker, J.; Hass, M.; McDonald, C.; Wu, C.; Farrell, R. A.

1996-01-01

177

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

178

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

179

Magnetic Propeller for Uniform Magnetic Field Levitation  

E-print Network

Three new approaches to generating thrust in uniform magnetic fields are proposed. The first direction is based on employing Lorentz force acting on partial magnetically shielded 8-shaped loop with current in external magnetic field, whereby a net force rather than a torque origins. Another approach, called a Virtual Wire System, is based on creating a magnetic field having an energetic symmetry (a virtual wire), with further superposition of external field. The external field breaks the symmetry causing origination of a net force. Unlike a wire with current, having radial energetic symmetry, the symmetry of the Virtual Wire System is closer to an axial wire. The third approach refers to the first two. It is based on creation of developed surface system, comprising the elements of the first two types. The developed surface approach is a way to drastically increase a thrust-to-weight ratio. The conducted experiments have confirmed feasibility of the proposed approaches.

Mark Krinker; Alexander Bolonkin

2008-07-12

180

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

181

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

182

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

183

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

184

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

185

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

186

[Magnetic fields and fish behavior].  

PubMed

In the review, contemporary data on the influence of natural and artificial magnetic fields on fish behavior are considered. In this regard, elasmobranchs and teleosts appear to be studied most exhaustively. Elasmobranchs and some teleosts are able to perceive magnetic fields via electroreceptors. A number of teleosts can sense magnetic fields via sensory cells containing crystals of biogenic magnetite. Laboratory experiments and field observations indicate the influence of magnetic fields on fish locomotor activity and spatial distribution. The geomagnetic field can be used by fish for navigation. Besides, artificial magnetic fields and natural fluctuations of the geomagnetic field can affect fish embryos leading to alterations in their development. It is suggested that, afterwards, these alterations can have an effect on fish behavior. PMID:25508098

2013-01-01

187

[Magnetic fields and fish behavior].  

PubMed

In the review, contemporary data on the influence of natural and artificial magnetic fields on fish behavior are considered. In this regard, elasmobranchs and teleosts appear to be studied most exhaustively. Elasmobranchs and some teleosts are able to perceive magnetic fields via electroreceptors. A number of teleosts can sense magnetic fields via sensory cells containing crystals of biogenic magnetite. Laboratory experiments and field observations indicate the influence of magnetic fields on fish locomotor activity and spatial distribution. The geomagnetic field can be used by fish for navigation. Besides, artificial magnetic fields and natural fluctuations of the geomagnetic field can affect fish embryos leading to alterations in their development. It is suggested that, afterwards, these alterations can have an effect on fish behavior. PMID:25438567

Krylov, V V; Iziumov, Iu G; Izvekov, E I; Nepomniashchikh, V A

2013-01-01

188

Exposure guidelines for magnetic fields  

SciTech Connect

The powerful magnetic fields produced by a controlled fusion experiment at Lawrence Livermore National Laboratory (LLNL) necessitated the development of personnel-exposure guidelines for steady magnetic fields. A literature search and conversations with active researchers showed that it is currently possible to develop preliminary exposure guidelines for steady magnetic fields. An overview of the results of past research into the bioeffects of magnetic fields was compiled, along with a discussion of hazards that may be encountered by people with sickle-cell anemia or medical electronic and prosthetic implants. The LLNL steady magnetic-field exposure guidelines along with a review of developments concerning the safety of time-varying fields were also presented in this compilation. Guidelines developed elsewhere for time varying fields were also given. Further research is needed to develop exposure standards for both steady or time-varying fields.

Miller, G.

1987-12-01

189

Magnetic-field-dosimetry system  

DOEpatents

A device is provided for measuring the magnetic field dose and peak field exposure. The device includes three Hall-effect sensors all perpendicular to each other, sensing the three dimensional magnetic field and associated electronics for data storage, calculating, retrieving and display.

Lemon, D.K.; Skorpik, J.R.; Eick, J.L.

1981-01-21

190

Magnetic fields in massive stars  

E-print Network

Although indirect evidence for the presence of magnetic fields in high-mass stars is regularly reported in the literature, the detection of these fields remains an extremely challenging observational problem. We review the recent discoveries of magnetic fields in different types of massive stars and briefly discuss strategies for spectropolarimetric observations to be carried out in the future.

S. Hubrig

2007-03-09

191

Study the effect of magnetic field on gaseous flames using digital speckle pattern interferometry  

NASA Astrophysics Data System (ADS)

An experimental investigation on the behavior of gaseous flames in the presence of magnetic field by using digital speckle pattern interferometry is presented. Premixed, partially premixed and diffusion flames generated by butane torch burner were exposed to the magnetic field of 0.35 Tesla. Phase has been extracted from a single DSPI fringe pattern by the application of Riesz transform and the monogenic signal and from which refractive index and the temperature were calculated. Experimental results show that the temperature and the width of the flames are increased under the influence of magnetic gradient.

Kumar, Manoj; Agarwal, Shilpi; Kumar, Varun; Khan, Gufran S.; Shakher, Chandra

2014-10-01

192

On-chip SQUID measurements in the presence of high magnetic fields  

E-print Network

We report a low temperature measurement technique and magnetization data of a quantum molecular spin, by implementing an on-chip SQUID technique. This technique enables the SQUID magnetometery in high magnetic fields, up to 7 Tesla. The main challenges and the calibration process are detailed. The measurement protocol is used to observe quantum tunneling jumps of the S=10 molecular magnet, Mn12-tBuAc. The effect of transverse field on the tunneling splitting for this molecular system is addressed as well.

L. Chen; W. Wernsdorfer; C. Lampropoulos; G. Christou; I. Chiorescu

2010-07-21

193

On-chip SQUID measurements in the presence of high magnetic fields  

E-print Network

We report a low temperature measurement technique and magnetization data of a quantum molecular spin, by implementing an on-chip SQUID technique. This technique enables the SQUID magnetometery in high magnetic fields, up to 7 Tesla. The main challenges and the calibration process are detailed. The measurement protocol is used to observe quantum tunneling jumps of the S=10 molecular magnet, Mn12-tBuAc. The effect of transverse field on the tunneling splitting for this molecular system is addressed as well.

Chen, L; Lampropoulos, C; Christou, G; Chiorescu, I

2010-01-01

194

Ferrofilm in a magnetic field  

NASA Astrophysics Data System (ADS)

A vertically draining thin ferrofilm under the influence of gravity and a nonuniform magnetic field is considered. It is observed experimentally that the presence of the magnetic field greatly alters the drainage of the film. A mathematical model is developed to describe the behavior. Experiments are conducted for multiple magnetic field configurations. The model is solved for two different sets of boundary conditions and results are compared to experiments. It is shown that the magnetic field structure, the concentration of magnetite in the solution, and the boundary conditions all have noticeable affects on the evolution of the thinning film. Good qualitative agreement between the model and the experiments is observed.

Back, Randy; Beckham, J. Regan

2012-10-01

195

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. PMID:22110653

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

2011-01-01

196

Physiological effects of cigarette smoking in the limbic system revealed by 3 tesla magnetic resonance spectroscopy.  

PubMed

Several studies and recent models of effects of nicotine, the main addictive and psychoactive component in tobacco, point to action of the drug on the limbic system during maintenance of addiction, either direct or indirect via projections from the ventral tegmental area. The objective of this study was to demonstrate physiological effects of cigarette smoking on the hippocampus and the grey matter of the dorsal anterior cingulate cortex in the human brain with regard to addiction and withdrawal. This aim was achieved by group comparisons of results of magnetic resonance spectroscopy between non-smokers, smokers and smokers during withdrawal. 12 smokers and 12 non-smokers were measured with single voxel proton magnetic resonance spectroscopy for total N-acetyl aspartate, glutamate and glutamine, choline-containing compounds, myo-inositol and total creatine in the right and the left hippocampus and in the right and the left dorsal anterior cingulate cortex. Smokers were examined twice, first during regular cigarette smoking and second on the third day of nicotine withdrawal. The ratios to total creatine were used for better reliability. In our study, Glx/tCr was significantly increased and tCho/tCr was significantly decreased in the left cingulate cortex in smokers compared to non-smokers (p = 0.01, both). Six out of seven smokers showed normalization of the Glx/tCr in the left cingulate cortex during withdrawal. Although these results are preliminary due to the small sample size, our results confirm the assumption that cigarette smoking interferes directly or indirectly with the glutamate circuit in the dorsal anterior cingulate cortex. PMID:24643301

Mennecke, Angelika; Gossler, Andrea; Hammen, Thilo; Dörfler, Arnd; Stadlbauer, Andreas; Rösch, Julie; Kornhuber, Johannes; Bleich, Stefan; Dölken, Marc; Thürauf, Norbert

2014-10-01

197

Variation of Phase Transformation Temperature in Fe-C Alloys in a High Magnetic Field  

NASA Astrophysics Data System (ADS)

A magnetic field can affect the transformation temperature and microstructure if a transformed phase has a different susceptibility from the parent phase. Fe-C alloy is an ideal system to show the magnetic field effect since, in this system, austenite (FCC structure) is a paramagnetic phase and ferrite (bcc structure) is a ferromagnetic phase below 770 °C. In this paper, phase transformation temperature in Fe-C alloys in a magnetic field was measured from a cooling curve. It was found that the transformation temperature for pure Fe from austenite to ferrite has a linear relationship with magnetic field strength, increasing about 0.8 °C per tesla. For eutectoid transformation in Fe-0.8C alloy, similar relationship exists; the transformation temperature increases about 1.5 °C per tesla. The measured interaction energy between magnetic field and ferrite is larger than that calculated from molecular field theory. An elongated and aligned microstructure by ferrite transformation in a high magnetic field was found in a Fe-0.4C alloy, but was not found in pure Fe and Fe-0.8C alloy.

Hao, X. J.; Ohtsuka, H.; Wada, H.

2005-07-01

198

Theory of fossil magnetic field  

NASA Astrophysics Data System (ADS)

Theory of fossil magnetic field is based on the observations, analytical estimations and numerical simulations of magnetic flux evolution during star formation in the magnetized cores of molecular clouds. Basic goals, main features of the theory and manifestations of MHD effects in young stellar objects are discussed.

Dudorov, Alexander E.; Khaibrakhmanov, Sergey A.

2015-02-01

199

Cosmic Magnetic Fields - An Overview  

NASA Astrophysics Data System (ADS)

Magnetic fields have been known in antiquity. Aristotle attributes the first of what could be called a scientific discussion on magnetism to Thales, who lived from about 625 BC. In China “magnetic carts” were in use to help the Emperor in his journeys of inspection. Plinius comments that in the Asia Minor province of Magnesia shepherds' staffs get at times “glued” to a stone, a alodestone. In Europe the magnetic compass came through the Arab sailors who met the Portuguese explorers. The first scientific treatise on magnetism, “De Magnete”, was published by William Gilbert who in 1600 described his experiments and suggested that the Earth was a huge magnet. Johannes Kepler was a correspondent of Gilbert and at times suggested that planetary motion was due to magnetic forces. Alas, this concept was demolished by Isaac Newton,who seeing the falling apple decided that gravity was enough. This concept of dealing with gravitational forces only remains en vogue even today. The explanations why magnetic effects must be neglected go from “magnetic energy is only 1% of gravitation” to “magnetic fields only complicate the beautiful computer solutions”. What is disregarded is the fact that magnetic effects are very directional(not omni-directional as gravity) and also the fact that magnetic fields are seen every where in our cosmic universe.

Wielebinski, Richard; Beck, Rainer

200

Measurements of magnetic field alignment  

SciTech Connect

The procedure for installing Superconducting Super Collider (SSC) dipoles in their respective cryostats involves aligning the average direction of their field with the vertical to an accuracy of 0.5 mrad. The equipment developed for carrying on these measurements is described and the measurements performed on the first few prototypes SSC magnets are presented. The field angle as a function of position in these 16.6 m long magnets is a characteristic of the individual magnet with possible feedback information to its manufacturing procedure. A comparison of this vertical alignment characteristic with a magnetic field intensity (by NMR) characteristic for one of the prototypes is also presented. 5 refs., 7 figs.

Kuchnir, M.; Schmidt, E.E.

1987-11-06

201

CHAPTER 3. STRUCTURE OF MAGNETIC FIELDS 1 Structure of Magnetic  

E-print Network

CHAPTER 3. STRUCTURE OF MAGNETIC FIELDS 1 Chapter 3 Structure of Magnetic Fields Many of the most interesting plasmas are permeated by or imbedded in magnetic fields.1 As shown in Fig. 3.1, the magnetic field properties of magnetic fields in plasmas can be discussed without specifying a model for the plasma

Callen, James D.

202

Studies of solar magnetic fields  

Microsoft Academic Search

An estimate of the average magnetic field strength at the poles of the Sun from Mount Wilson measurements is made by comparing low latitude magnetic measurements in the same regions made near the center of the disk and near the limb. There is still some uncertainty because the orientation angle of the field lines in the meridional plane is unknown,

Robert Howard

1977-01-01

203

Top-loading small-sample calorimeters for measurements as a function of magnetic field angle  

NASA Astrophysics Data System (ADS)

In quasi-low-dimensional systems, the existence of a particular physical state and the temperature and magnetic-field-dependence of its phase boundary often strongly depends on magnetic field orientation. To investigate magnetic field orientation dependent phase transitions in these materials, we have developed rotatable miniature and sub-miniature sample-in-vacuum calorimeters that operate in dc magnetic fields up to 18 and 45 tesla. The calorimeters cover the temperature range from below 0.1 K to above 10 K; they are able rotate a full 360 degrees relative to the applied magnetic field while remaining at base temperature. Samples are typically on the order of 1 mg in mass and up to 2 mm2 × 0.5 mm in volume.

Fortune, N. A.; Hannahs, S. T.

2014-12-01

204

Liquid neon heat transfer as applied to a 30 tesla cryomagnet  

NASA Technical Reports Server (NTRS)

Since superconducting magnets cooled by liquid helium are limited to magnetic fields of about 18 teslas, the design of a 30 tesla cryomagnet necessitates forced convection liquid neon heat transfer in small coolant channels. As these channels are too small to handle the vapor flow if the coolant were to boil, the design philosophy calls for suppressing boiling by subjecting the fluid to high pressures. Forced convection heat transfer data are obtained by using a blowdown technique to force the fluid vertically through a resistance-heated instrumented tube. The data are obtained at inlet temperatures between 28 and 34 K and system pressures between 28 to 29 bars. Data correlation is limited to a very narrow range of test conditions, since the tests were designed to simulate the heat transfer characteristics in the coolant channels of the 30 tesla cryomagnet concerned. The results can therefore be applied directly to the design of the magnet system.-

Papell, S. S.; Hendricks, R. C.

1975-01-01

205

Bridgman Growth of GeSi Alloys in a Static Magnetic Field  

NASA Technical Reports Server (NTRS)

Ge(0.95)Si(0.050 alloy crystals have been grown by the vertical Bridgman technique, both with and without an axial 5 Tesla magnetic field. The crystals were processed in a constant axial thermal gradient and the effects of graphite, hot pressed boron nitride, and pyrolitic boron nitride ampoule materials on interface shapes and macrosegregation profiles were investigated. The sample grown in a graphite ampoule at 5 Tesla exhibited a macroscopic axial concentration profile close to that of complete mixing and strong striation patterns. In samples grown in boron nitride ampoules, both with and without a 5 Tesla magnetic field applied, measured macroscopic axial concentration profiles were intermediate between those expected for a completely mixed melt and diffusion-controlled growth, and striation patterns were also observed. Possible explanations for the apparent inability of the magnetic field to reduce the flow velocities to below the growth velocities are discussed, and results of growth experiments in pyrolitic boron nitride ampoules are also described.

Volz, M. P.; Szofran, F. R.; Vujisic, L.; Motakef, S.

1998-01-01

206

[New possibilities and aspects of low-field magnetic resonance tomography].  

PubMed

Worldwide, MRI is going up to higher field-strength. For imaging, magnets with field-strength between 0.2 and about 2.5 Tesla are installed. Below 0.2 Tesla, Low-Field-systems have been used in research-projects to optimize image quality. New developments of 0.064 Tesla Permanent-Magnet-MRI are hopeful for clinical work. Future possibilities of Low-Field-MRI are shown. The advantages of this system are good image quality by low initial start-up and operating costs as well as ease of sitting and lack of need for cryogens. The open design has excellent patient acceptance and allows to examine patients with claustrophobia feelings. It allows easier monitoring during the examination-especially children and patients with cancer or polytraumatic diseases. The introduction of more affordable MRI-systems of low-field-strength may decrease the cost of MRI to the point where it is competitive with computer tomography. PMID:2798840

Grönemeyer, D H; Kaufman, L; Rothschild, P; Seibel, R M

1989-01-01

207

Solar magnetic fields and convection  

Microsoft Academic Search

The solar magnetic fields observed in active regions and their residues are thought to be parts of toroidal field systems renewed every 11-yr cycle from a poloidal field. The latter may be either a reversing (dynamo) field or a non-reversing, primordial field. The latter view was held for some 70 yr, but the apparent reversals of the polar-cap fields in

J. H. Piddington

1977-01-01

208

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

209

Dummy Coil Development for the Cable-In-Conduit Conductors Superconducting Outsert Coils of a 40 Tesla Hybrid Magnet  

Microsoft Academic Search

A dummy coil is being wound at the High Magnetic Field Laboratory, Chinese Academy of Sciences (CHMFL). Building the dummy coil will develop the manufacturing technology for the CICC, especially the cabling, forming and winding techniques of the rectangular conductor. This paper will present the manufacturing process of the dummy coil. It will include the cabling of the wire, the

Y. F. Tan; G. L. Kuang; Y. N. Pan; J. W. Zhu; W. G. Chen; F. T. Wang; Z. M. Chen; Z. Y. Chen; Y. Ren; P. He

2010-01-01

210

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

211

Magnetically induced electric fields and currents in the circulatory system.  

PubMed

Blood flow in an applied magnetic field gives rise to induced voltages in the aorta and other major arteries of the central circulatory system that can be observed as superimposed electrical signals in the electrocardiogram (ECG). The largest magnetically induced voltage occurs during pulsatile blood flow into the aorta, and results in an increased signal at the location of the T-wave in the ECG. Studies involving the measurement of blood pressure, blood flow rate, heart sounds, and cardiac valve displacements have been conducted with monkeys and dogs exposed to static fields up to 1.5 tesla (T) under conditions producing maximum induced voltages in the aorta. Results of these studies gave no indication of alterations in cardiac functions or hemodynamic parameters. Cardiac activity monitored by ECG biotelemetry during continuous exposure of rats to a 1.5-T field for 10 days gave no evidence for any significant changes relative to the 10 days prior to and following exposure. Theoretical modeling of magnetic field interactions with blood flow has included a complete solution of the equation describing the flow of an electrically conductive fluid in the presence of a magnetic field (the Navier-Stokes equation) using the finite element technique. Magnetically induced voltages and current densities as a function of the applied magnetic field strength have been calculated for the aorta and surrounding tissues structures, including the sinoatrial node. Induced current densities in the region of the sinoatrial node are predicted to be >100 mA/m2 at field levels >5 T in an adult human under conditions of maximum electrodynamic coupling with aortic blood flow. Magnetohydrodynamic interactions are predicted to reduce the volume flow rate of blood in the human aorta by a maximum of 1.3%, 4.9%, and 10.4% at field levels of 5, 10, and 15 T, respectively. PMID:15556666

Tenforde, Thomas S

2005-01-01

212

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

213

Electromagnetic superconductivity of vacuum induced by strong magnetic field  

E-print Network

The quantum vacuum may become an electromagnetic superconductor in the presence of a strong external magnetic field of the order of 10^{16} Tesla. The magnetic field of the required strength (and even stronger) is expected to be generated for a short time in ultraperipheral collisions of heavy ions at the Large Hadron Collider. The superconducting properties of the new phase appear as a result of a magnetic-field-assisted condensation of quark-antiquark pairs with quantum numbers of electrically charged rho mesons. We discuss similarities and differences between the suggested superconducting state of the quantum vacuum, a conventional superconductivity and the Schwinger pair creation. We argue qualitatively and quantitatively why the superconducting state should be a natural ground state of the vacuum at the sufficiently strong magnetic field. We demonstrate the existence of the superconducting phase using both the Nambu-Jona-Lasinio model and an effective bosonic model based on the vector meson dominance (the rho-meson electrodynamics). We discuss various properties of the new phase such as absence of the Meissner effect, anisotropy of superconductivity, spatial inhomogeneity of ground state, emergence of a neutral superfluid component in the ground state and presence of new topological vortices in the quark-antiquark condensates.

M. N. Chernodub

2012-08-24

214

Thermometers in Low Magnetic Fields  

NASA Astrophysics Data System (ADS)

In this article the effect of low amplitude DC magnetic fields on different types of thermometers is discussed. By means of a precision water-cooled electromagnet, the effect of a magnetic field on platinum resistance thermometers, thermistors, and type T, J, and K thermocouples was investigated, while thermometers were thermally stabilized in thermostatic baths. Four different baths were used for temperatures from 77 K (-196 °C) to 353 K (80 °C): liquid nitrogen bath (nitrogen boiling point at atmospheric pressure), ice-point bath, room-temperature air bath, and hot-water bath. The generated DC magnetic field of high relative precision (2 × 10-4 at 1 T, 4 × 10-5 short-term stability) and high relative uniformity (2 × 10-5 over 1 cm2, 10 mm gap) had a magnetic flux density of 1 T in the center of the gap between the magnet pole caps. The results indicate a magnetic effect of up to 100 mK due to a 1 T magnetic field for the types of thermocouples composed of ferromagnetic materials (Fe, Cr, Ni). For platinum resistance thermometers, thermistors, and non-magnetic type T thermocouples, the detected magnetic effect was weaker, i.e., under 10 mK.

Geršak, G.; Beguš, S.

2010-09-01

215

Low-Magnetic-Field Magnetars  

NASA Astrophysics Data System (ADS)

It is now widely accepted that soft gamma repeaters and anomalous X-ray pulsars are the observational manifestations of magnetars, i.e. sources powered by their own magnetic energy. This view was supported by the fact that these "magnetar candidates" exhibited, without exception, a surface dipole magnetic field (as inferred from the spin-down rate) in excess of the electron critical field (? 4.4×1013 G). The recent discovery of fully qualified magnetars, SGR 0418+5729 and Swift J1822.3-1606, with dipole magnetic field well in the range of ordinary radio pulsars posed a challenge to the standard picture, showing that a very strong field is not necessary for the onset of magnetar activity (chiefly bursts and outbursts). Here we summarize the observational status of the low-magnetic-field magnetars and discuss their properties in the context of the mainstream magnetar model and its main alternatives.

Turolla, Roberto; Esposito, Paolo

2013-11-01

216

Resonant magnetic fields from inflation  

SciTech Connect

We propose a novel scenario to generate primordial magnetic fields during inflation induced by an oscillating coupling of the electromagnetic field to the inflaton. This resonant mechanism has two key advantages over previous proposals. First of all, it generates a narrow band of magnetic fields at any required wavelength, thereby allaying the usual problem of a strongly blue spectrum and its associated backreaction. Secondly, it avoids the need for a strong coupling as the coupling is oscillating rather than growing or decaying exponentially. Despite these major advantages, we find that the backreaction is still far too large during inflation if the generated magnetic fields are required to have a strength of O(10{sup ?15} Gauss) today on observationally interesting scales. We provide a more general no-go argument, proving that this problem will apply to any model in which the magnetic fields are generated on subhorizon scales and freeze after horizon crossing.

Byrnes, Christian T. [CERN, PH-TH Division, CH-1211, Genève 23 (Switzerland); Hollenstein, Lukas; Jain, Rajeev Kumar [Département de Physique Théorique and Center for Astroparticle Physics, Université de Genève, 24, Quai Ernest Ansermet, CH-1211 Genève 4 (Switzerland); Urban, Federico R., E-mail: cbyrnes@cern.ch, E-mail: lukas.hollenstein@unige.ch, E-mail: rajeev.jain@unige.ch, E-mail: urban@phas.ubc.ca [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, B.C. V6T 1Z1 (Canada)

2012-03-01

217

Zoomed Functional Imaging in the Human Brain at 7 Tesla with Simultaneous High Spatial and High Temporal Resolution  

Microsoft Academic Search

Functional neuroimaging in the human brain using noninvasive magnetic resonance methods has the potential of providing highly resolved maps of neuronal activation. Decreasing the voxel size and obtaining simultaneously high temporal resolution is a major challenge and is mainly limited by sensitivity. Here, signal-to-noise gains at high magnetic fields (7 Tesla) and an optimized surface coil setup are combined with

Josef Pfeuffer; Pierre-Francois van de Moortele; Essa Yacoub; Amir Shmuel; Gregor Adriany; Peter Andersen; Hellmut Merkle; Michael Garwood; Kamil Ugurbil; Xiaoping Hu

2002-01-01

218

Improved Cerebral Time-of-Flight Magnetic Resonance Angiography at 7 Tesla – Feasibility Study and Preliminary Results Using Optimized Venous Saturation Pulses  

PubMed Central

Purpose Conventional saturation pulses cannot be used for 7 Tesla ultra-high-resolution time-of-flight magnetic resonance angiography (TOF MRA) due to specific absorption rate (SAR) limitations. We overcome these limitations by utilizing low flip angle, variable rate selective excitation (VERSE) algorithm saturation pulses. Material and Methods Twenty-five neurosurgical patients (male n?=?8, female n?=?17; average age 49.64 years; range 26–70 years) with different intracranial vascular pathologies were enrolled in this trial. All patients were examined with a 7 Tesla (Magnetom 7 T, Siemens) whole body scanner system utilizing a dedicated 32-channel head coil. For venous saturation pulses a 35° flip angle was applied. Two neuroradiologists evaluated the delineation of arterial vessels in the Circle of Willis, delineation of vascular pathologies, presence of artifacts, vessel-tissue contrast and overall image quality of TOF MRA scans in consensus on a five-point scale. Normalized signal intensities in the confluence of venous sinuses, M1 segment of left middle cerebral artery and adjacent gray matter were measured and vessel-tissue contrasts were calculated. Results Ratings for the majority of patients ranged between good and excellent for most of the evaluated features. Venous saturation was sufficient for all cases with minor artifacts in arteriovenous malformations and arteriovenous fistulas. Quantitative signal intensity measurements showed high vessel-tissue contrast for confluence of venous sinuses, M1 segment of left middle cerebral artery and adjacent gray matter. Conclusion The use of novel low flip angle VERSE algorithm pulses for saturation of venous vessels can overcome SAR limitations in 7 Tesla ultra-high-resolution TOF MRA. Our protocol is suitable for clinical application with excellent image quality for delineation of various intracranial vascular pathologies. PMID:25232868

Wrede, Karsten H.; Johst, Sören; Dammann, Philipp; Özkan, Neriman; Mönninghoff, Christoph; Kraemer, Markus; Maderwald, Stefan; Ladd, Mark E.; Sure, Ulrich; Umutlu, Lale; Schlamann, Marc

2014-01-01

219

condensate in constant magnetic fields  

Microsoft Academic Search

We solve the Dirac equation in the presence of a constant magnetic field in (3+1) and (2+1) dimensions. Quantizing the fermion field, we calculate the condensate from first principles for parity conserving and violating Lagrangians for arbitrary field strength. We make a comparison with the results already known in the literature for some particular cases and point out the relevance

M. de J Anguiano-Galicia; A. Bashir; A. Raya

2007-01-01

220

Investigating Magnetic Force Fields  

NSDL National Science Digital Library

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

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

2012-03-18

221

Preface: Cosmic magnetic fields  

NASA Astrophysics Data System (ADS)

Recent advances in observations and modeling have opened new perspectives for the understanding of fundamental dynamical processes of cosmic magnetism, and associated magnetic activity on the Sun, stars and galaxies. The goal of the Special Issue is to discuss the progress in solar physics and astrophysics, similarities and differences in phenomenology and physics of magnetic phenomena on the Sun and other stars. Space observatories, ground-based telescopes, and new observational methods have provided tremendous amount of data that need to be analyzed and understood. The solar observations discovered multi-scale organization of solar activity, dramatically changing current paradigms of solar variability. On the other side, stellar observations discovered new regimes of dynamics and magnetism that are different from the corresponding solar phenomena, but described by the same physics. Stars represent an astrophysical laboratory for studying the dynamical, magnetic and radiation processes across a broad range of stellar masses and ages. These studies allow us to look at the origin and evolution of our Sun, whereas detailed investigations of the solar magnetism give us a fundamental basis for interpretation and understanding of unresolved stellar data.

Kosovichev, Alexander

2015-02-01

222

Unambiguous identification of superparamagnetic iron oxide (SPIO) particles through quantitative susceptibility mapping of the nonlinear response to magnetic fields  

PubMed Central

Superparamagnetic iron oxide (SPIO) particles generate signal void regions on gradient echo images due to their strong magnetization. In practice, the signal void region might be indistinguishable from that generated by air. However, the response of SPIO to an externally applied magnetic field is non-linear. Magnetization of SPIO saturates at around 1 Tesla while magnetization of water and air increase linearly with field strength. Phantom experiment and mice experiments demonstrated the feasibility of a non-ambiguous identification of superparamagnetic contrast agents. PMID:20688448

Liu, Tian; Spincemaille, Pascal; de Rochefort, Ludovic; Wong, Richard; Prince, Martin; Wang, Yi

2010-01-01

223

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

224

The magnetic field of Canopus  

Microsoft Academic Search

Zeeman spectrograms taken at the ESO in 1978 for Canopus (F0 Ib-II) confirm the presence of the weak magnetic field detected by Schermann (1977) and Rakosch et al. (1977), and a new period of 6.90 days for the Canopus magnetic field variation is proposed. It is noted that with the MSHIFT-technique (Weiss et al., 1978) the plate-mean Zeeman shifts can

W. W. Weiss

1986-01-01

225

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

226

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

227

The first excited states of platinum phthalocyanine in magnetic fields  

NASA Astrophysics Data System (ADS)

A Zeeman study of platinum phthalocyanine in Shpol'skii matrices was performed in the temperature range of 25-77 K with magnetic fields up to ˜6·3 Tesla (T). The general phosphorescence region (950-945 nm) exhibited only one principal peak whose position is not affected by the field. An extremely weak structure that is energetically about 26 cm-1 lower than the principal peak and which originally was attributed to a different crystal site turned out to be a genuine field dependent collective response of weakly radiating spin-levels. The weakness of the radiation from these levels and the size of the subsequently confirmed zero field splitting D parameter are a unique case among all porphyrins and phthalocyanines studied to date in magnetic fields. For the first time the coefficients of the 5d (zx and yz) AO of PtPc in the egx LCAO MO were experimentally determined to be about 0·18. The Zeeman effect of the first ?-?* absorption, in terms of phosphorescence excitation, was also investigated in approximately the same temperature and field range. An apparent angular momentum of ?' ? 3.6? was deduced from the Zeeman energy in the components of the 1Eu state lifted by the crystal field. ?', in turn, gives rise to an orbital reduction factor q ? 0·9 which implies a fairly weak Jahn-Teller coupling, similar to but weaker than that found earlier in PdPc.

Chen, Wen-Hsiung; Rieckhoff, Klaus E.; Voigt, Eva-Maria

228

Study on technology of high-frequency pulsed magnetic field strength measurement.  

PubMed

High-frequency transient weak magnetic field is always involved in researches about biomedical engineering field while common magnetic-field sensors cannot work properly at frequencies as high as MHz. To measure the value of MHz-level weak pulsed magnetic-field strength accurately, this paper designs a measurement and calibration method for pulsed magnetic-field. In this paper, a device made of Nonferromagnetic material was independently designed and applied to pulsed magnetic field measurement. It held an accurately relative position between the magnetic field generating coil and the detecting coil. By applying a sinusoidal pulse to the generator, collecting the induced electromotive force of the detector, the final magnetic field strength was worked out through algorithms written in Matlab according to Faraday's Law. Experiments were carried out for measurement and calibration. Experiments showed that, under good stability and consistency, accurate measurement of magnetic-field strength of a sinepulse magnetic-field can be achieved, with frequency at 0.5, 1, 1.5 MHz and strength level at micro-Tesla. Calibration results carried out a measuring relative error about 2.5%. PMID:23366106

Chen, Yi-Mei; Liu, Zhi-Peng; Yin, Tao

2012-01-01

229

Magnetostriction and magnetic texture to 100.75 Tesla in frustrated SrCu2(BO3)2  

NASA Astrophysics Data System (ADS)

SrCu2(BO3)2, a spin-1/2 Heisenberg antiferromagnet in the archetypical Shastry-Sutherland lattice, exhibits a rich spectrum of magnetization plateaus and stripe-like magnetic textures in applied fields. The structure of these plateaus is still highly controversial due to the intrinsic complexity associated with frustration and competing length scales. We discover magnetic textures in SrCu2(BO3)2 via FBG-optical fiber based magnetostriction and magnetocaloric measurements in fields up to 100.75 T. In addition to observing low-field fine structure with unprecedented resolution, the data also reveal lattice responses at 73.6 T and at 82 T that we attribute, using a controlled density matrix renormalization group approach, to a unanticipated 2/5 plateau and to the long-predicted 1/2 plateau. Research supported by NSF, State of Florida and the US DOE Basic Energy Science project ``Science at 100T.'' ref: M. Jaime et al., PNAS 109, 120404 (2012).

Jaime, M.; Daou, R.; Crooker, S. A.; Weickert, F.; Uchida, A.; Feiguin, A. E.; Batista, C. D.; Dabkowska, H. A.; Gaulin, B. D.

2013-03-01

230

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

231

Magnetic field induced dynamical chaos  

SciTech Connect

In this article, we have studied the dynamics of a particle having charge in the presence of a magnetic field. The motion of the particle is confined in the x–y plane under a two dimensional nonlinear potential. We have shown that constant magnetic field induced dynamical chaos is possible even for a force which is derived from a simple potential. For a given strength of the magnetic field, initial position, and velocity of the particle, the dynamics may be regular, but it may become chaotic when the field is time dependent. Chaotic dynamics is very often if the field is time dependent. Origin of chaos has been explored using the Hamiltonian function of the dynamics in terms of action and angle variables. Applicability of the present study has been discussed with a few examples.

Ray, Somrita; Baura, Alendu; Bag, Bidhan Chandra, E-mail: bidhanchandra.bag@visva-bharati.ac.in [Department of Chemistry, Visva-Bharati, Santiniketan 731 235 (India)

2013-12-15

232

A Calculation of Required Magnetic Field Strength in a Magnetohydrodynamic Supersonic Generator and Accelerator  

NASA Astrophysics Data System (ADS)

A one-dimensional supersonic CFD code was utilized to solve for the required magnetic field strength, as a function of conductivity, for fixed length and constant static enthalpy magnetohydrodynamic generator and accelerator. The inlet velocity and pressure to the generator were varied, while requiring the exit Mach number of the generator to remain at 2.0. The flow after the generator proceeded through a simple supersonic combustion process, and the bypassed energy was then used in the accelerator to increase the flow velocity. Results show that varying the conductivity between 7 and 70 mho/m and inlet velocity between 5000 and 14000 ft/s, require magnetic fields in the generator between 1 and 12 Tesla with greater magnetic field strength required at lower conductivities. It was also calculated that for the same energy and conductivity used in the accelerator, a lower magnetic field was needed.

Lang, Amy W.; Czysz, Paul

2001-11-01

233

Strain-induced pseudo-magnetic fields and charging effects on CVD-grown graphene  

NASA Astrophysics Data System (ADS)

Atomically resolved imaging and spectroscopic characteristics of chemical vapor deposition (CVD) grown graphene on Cu are studied using scanning tunneling microscopy and spectroscopy. CVD-grown graphene remaining on Cu exhibits large ripples and appears strongly strained. Different regions show different lattice structures and electronic density of states (DOS). Ridges appear along the boundaries of different lattice structures, which reveal excess charging effects. The large, non-uniform strain induces pseudo-magnetic fields up to ˜50 Tesla, yielding integer and fractional quantum Hall effects (IQHE and FQHE) as quantized conductance peaks in the DOS. For CVD-grown graphene transferred from Cu to SiO2, the average strain and the resulting charging effects and pseudo-magnetic fields are much reduced. Fourier transformation of the local DOS of strained samples as well as data on the effects of real magnetic fields versus pseudo-magnetic fields will be presented. This work was jointly supported by NSF and NRI.

Wu, R. T.-P.; Teague, M.-L.; Yeh, N.-C.; Yeom, S.; Standley, B. L.; Boyd, D. A.; Bockrath, M. W.

2011-03-01

234

Increase in the mitotic recombination frequency in Drosophila melanogaster by magnetic field exposure and its suppression by vitamin E supplement  

Microsoft Academic Search

In order to estimate possible mutagenic and\\/or carcinogenic activity of electromagnetic fields, wing spot tests were performed in Drosophila melanogaster. A DNA repair defective mutation mei-41D5 was introduced into the conventional mwh\\/flr test system to enhance mutant spot frequency. Third instar larvae were exposed to a 5-Tesla static magnetic field for 24 h, and after molting, wings were examined under

Takao Koana; Mikie O Okada; Masateru Ikehata; Masayoshi Nakagawa

1997-01-01

235

Damping of cosmic magnetic fields  

SciTech Connect

We examine the evolution of magnetic fields in an expanding fluid composed of matter and radiation with particular interest in the evolution of cosmic magnetic fields. We derive the propagation velocities and damping rates for relativistic and non-relativistic fast and slow magnetosonic and Alfv{acute e}n waves in the presence of viscous and heat conducting processes. The analysis covers all magnetohydrodynamics modes in the radiation diffusion and the free-streaming regimes. When our results are applied to the evolution of magnetic fields in the early universe, we find that cosmic magnetic fields are damped from prior to the epoch of neutrino decoupling up to recombination. Similar to the case of sound waves propagating in a demagnetized plasma, fast magnetosonic waves are damped by radiation diffusion on all scales smaller than the radiation diffusion length. The characteristic damping scales are the horizon scale at neutrino decoupling (M{sub {nu}}{approx}10{sup {minus}4}M{sub {circle_dot}} in baryons) and the Silk mass at recombination (M{sub {gamma}}{approx}10{sup 13}M{sub {circle_dot}} in baryons). In contrast, the oscillations of slow magnetosonic and Alfv{acute e}n waves get overdamped in the radiation diffusion regime, resulting in frozen-in magnetic field perturbations. Further damping of these perturbations is possible only if before recombination the wave enters a regime in which radiation free-streams on the scale of the perturbation. The maximum damping scale of slow magnetosonic and Alfv{acute e}n modes is always smaller than or equal to the damping scale of fast magnetosonic waves, and depends on the magnetic field strength and its direction relative to the wave vector. Our findings have multifold implications for cosmology. The dissipation of magnetic field energy into heat during the epoch of neutrino decoupling ensures that most magnetic field configurations generated in the very early universe satisfy big bang nucleosynthesis constraints. Further dissipation before recombination constrains models in which primordial magnetic fields give rise to galactic magnetic fields or density perturbations. Finally, the survival of Alfv{acute e}n and slow magnetosonic modes on scales well below the Silk mass may be of significance for the formation of structure on small scales. {copyright} {ital 1998} {ital The American Physical Society}

Jedamzik, K. [Max-Planck-Institut fuer Astrophysik, 85748 Garching bei Muenchen (Germany)] [Max-Planck-Institut fuer Astrophysik, 85748 Garching bei Muenchen (Germany); Katalinic, V.; Olinto, A.V. [Department of Astronomy and Astrophysics and Enrico Fermi Institute, University of Chicago, 5640 S. Ellis Ave., Chicago, Illinois 60637 (United States)] [Department of Astronomy and Astrophysics and Enrico Fermi Institute, University of Chicago, 5640 S. Ellis Ave., Chicago, Illinois 60637 (United States)

1998-03-01

236

Damping of cosmic magnetic fields  

NASA Astrophysics Data System (ADS)

We examine the evolution of magnetic fields in an expanding fluid composed of matter and radiation with particular interest in the evolution of cosmic magnetic fields. We derive the propagation velocities and damping rates for relativistic and non-relativistic fast and slow magnetosonic and Alfvén waves in the presence of viscous and heat conducting processes. The analysis covers all magnetohydrodynamics modes in the radiation diffusion and the free-streaming regimes. When our results are applied to the evolution of magnetic fields in the early universe, we find that cosmic magnetic fields are damped from prior to the epoch of neutrino decoupling up to recombination. Similar to the case of sound waves propagating in a demagnetized plasma, fast magnetosonic waves are damped by radiation diffusion on all scales smaller than the radiation diffusion length. The characteristic damping scales are the horizon scale at neutrino decoupling (M?~10-4Msolar in baryons) and the Silk mass at recombination (M?~1013Msolar in baryons). In contrast, the oscillations of slow magnetosonic and Alfvén waves get overdamped in the radiation diffusion regime, resulting in frozen-in magnetic field perturbations. Further damping of these perturbations is possible only if before recombination the wave enters a regime in which radiation free-streams on the scale of the perturbation. The maximum damping scale of slow magnetosonic and Alfvén modes is always smaller than or equal to the damping scale of fast magnetosonic waves, and depends on the magnetic field strength and its direction relative to the wave vector. Our findings have multifold implications for cosmology. The dissipation of magnetic field energy into heat during the epoch of neutrino decoupling ensures that most magnetic field configurations generated in the very early universe satisfy big bang nucleosynthesis constraints. Further dissipation before recombination constrains models in which primordial magnetic fields give rise to galactic magnetic fields or density perturbations. Finally, the survival of Alfvén and slow magnetosonic modes on scales well below the Silk mass may be of significance for the formation of structure on small scales.

Jedamzik, Karsten; Katalini?, Višnja; Olinto, Angela V.

1998-03-01

237

Magnetic fields in protoplanetary disks  

E-print Network

Magnetic fields likely play a key role in the dynamics and evolution of protoplanetary discs. They have the potential to efficiently transport angular momentum by MHD turbulence or via the magnetocentrifugal acceleration of outflows from the disk surface, and magnetically-driven mixing has implications for disk chemistry and evolution of the grain population. However, the weak ionisation of protoplanetary discs means that magnetic fields may not be able to effectively couple to the matter. I present calculations of the ionisation equilibrium and magnetic diffusivity as a function of height from the disk midplane at radii of 1 and 5 AU. Dust grains tend to suppress magnetic coupling by soaking up electrons and ions from the gas phase and reducing the conductivity of the gas by many orders of magnitude. However, once grains have grown to a few microns in size their effect starts to wane and magnetic fields can begin to couple to the gas even at the disk midplane. Because ions are generally decoupled from the magnetic field by neutral collisions while electrons are not, the Hall effect tends to dominate the diffusion of the magnetic field when it is able to partially couple to the gas. For a standard population of 0.1 micron grains the active surface layers have a combined column of about 2 g/cm^2 at 1 AU; by the time grains have aggregated to 3 microns the active surface density is 80 g/cm^2. In the absence of grains, x-rays maintain magnetic coupling to 10% of the disk material at 1 AU (150 g/cm^2). At 5 AU the entire disk thickness becomes active once grains have aggregated to 1 micron in size.

Mark Wardle

2007-04-07

238

Smallscale Solar Magnetic Fields - an Overview  

Microsoft Academic Search

An overview is given of the observational and the theoretical methods used to investigate solar magnetic fields. It includes an introduction to the Stokes parameters, their radiative transfer in the presence of a magnetic field, and empirical techniques used to measure various properties of solar magnetic features, such as the strength and direction of the magnetic field, magnetic flux, temperature,

Sami K. Solanki

1993-01-01

239

Cryogenic properties of dispersion strengthened copper for high magnetic fields  

NASA Astrophysics Data System (ADS)

Cold deformed copper matrix composite conductors, developed for use in the 100 tesla multi-shot pulsed magnet at the National High Magnetic Field Laboratory (NHMFL), have been characterized. The conductors are alumina strengthened copper which is fabricated by cold drawing that introduces high dislocation densities and high internal stresses. Both alumina particles and high density of dislocations provide us with high tensile strength and fatigue endurance. The conductors also have high electrical conductivities because alumina has limited solubility in Cu and dislocations have little scattering effect on conduction electrons. Such a combination of high strength and high conductivity makes it an excellent candidate over other resistive magnet materials. Thus, characterization is carried out by tensile testing and fully reversible fatigue testing. In tensile tests, the material exceeds the design criteria parameters. In the fatigue tests, both the load and displacement were measured and used to control the amplitude of the tests to simulate the various loading conditions in the pulsed magnet which is operated at 77 K in a non-destructive mode. In order to properly simulate the pulsed magnet operation, strain-controlled tests were more suitable than load controlled tests. For the dispersion strengthened coppers, the strengthening mechanism of the aluminum oxide provided better tensile and fatigue properties over convention copper.

Toplosky, V. J.; Han, K.; Walsh, R. P.; Swenson, C. A.

2014-01-01

240

Cryogenic properties of dispersion strengthened copper for high magnetic fields  

SciTech Connect

Cold deformed copper matrix composite conductors, developed for use in the 100 tesla multi-shot pulsed magnet at the National High Magnetic Field Laboratory (NHMFL), have been characterized. The conductors are alumina strengthened copper which is fabricated by cold drawing that introduces high dislocation densities and high internal stresses. Both alumina particles and high density of dislocations provide us with high tensile strength and fatigue endurance. The conductors also have high electrical conductivities because alumina has limited solubility in Cu and dislocations have little scattering effect on conduction electrons. Such a combination of high strength and high conductivity makes it an excellent candidate over other resistive magnet materials. Thus, characterization is carried out by tensile testing and fully reversible fatigue testing. In tensile tests, the material exceeds the design criteria parameters. In the fatigue tests, both the load and displacement were measured and used to control the amplitude of the tests to simulate the various loading conditions in the pulsed magnet which is operated at 77 K in a non-destructive mode. In order to properly simulate the pulsed magnet operation, strain-controlled tests were more suitable than load controlled tests. For the dispersion strengthened coppers, the strengthening mechanism of the aluminum oxide provided better tensile and fatigue properties over convention copper.

Toplosky, V. J.; Han, K.; Walsh, R. P. [National High Magnetic Field Laboratory, Tallahassee, FL 32310 (United States); Swenson, C. A. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

2014-01-27

241

Simulation of RF Cavity Dark Current in Presence of Helical Magnetic Field  

E-print Network

In order to produce muon beam of high enough quality to be used for a Muon Collider, its large phase space must be cooled several orders of magnitude. This task can be accomplished by ionization cooling. Ionization cooling consists of passing a high-emittance muon beam alternately through regions of low Z material, such as liquid hydrogen, and very high accelerating RF cavities within a multi-Tesla solenoidal focusing channel. But first high power tests of RF cavity with beryllium windows in solenoidal magnetic field showed a dramatic drop in accelerating gradient due to RF breakdowns. It has been concluded that external magnetic fields parallel to RF electric field significantly modifies the performance of RF cavities. However, magnetic field in Helical Cooling Channel has a strong dipole component in addition to solenoidal one. The dipole component essentially changes electron motion in a cavity compare to pure solenoidal case, making dark current less focused at field emission sites. The simulation of dark...

Romanov, Gennady

2010-01-01

242

A magnetically shielded room with ultra low residual field and gradient  

NASA Astrophysics Data System (ADS)

A versatile and portable magnetically shielded room with a field of (700 ± 200) pT within a central volume of 1 m × 1 m × 1 m and a field gradient less than 300 pT/m, achieved without any external field stabilization or compensation, is described. This performance represents more than a hundredfold improvement of the state of the art for a two-layer magnetic shield and provides an environment suitable for a next generation of precision experiments in fundamental physics at low energies; in particular, searches for electric dipole moments of fundamental systems and tests of Lorentz-invariance based on spin-precession experiments. Studies of the residual fields and their sources enable improved design of future ultra-low gradient environments and experimental apparatus. This has implications for developments of magnetometry beyond the femto-Tesla scale in, for example, biomagnetism, geosciences, and security applications and in general low-field nuclear magnetic resonance (NMR) measurements.

Altarev, I.; Babcock, E.; Beck, D.; Burghoff, M.; Chesnevskaya, S.; Chupp, T.; Degenkolb, S.; Fan, I.; Fierlinger, P.; Frei, A.; Gutsmiedl, E.; Knappe-Grüneberg, S.; Kuchler, F.; Lauer, T.; Link, P.; Lins, T.; Marino, M.; McAndrew, J.; Niessen, B.; Paul, S.; Petzoldt, G.; Schläpfer, U.; Schnabel, A.; Sharma, S.; Singh, J.; Stoepler, R.; Stuiber, S.; Sturm, M.; Taubenheim, B.; Trahms, L.; Voigt, J.; Zechlau, T.

2014-07-01

243

Magnetic field mapping of the Belle solenoid N. Tan a M. Akatsu b A. Bozek c;2 K. Fujimoto b J. Haba c;1  

E-print Network

a novel moving mechanism for the field probes that uses an ultrasonic motor located in the strong magnetic at the solenoid center is 1.5 Tesla at 1 E­mail: junji.haba@kek.jp 2 Present address: Krakow Inst. of Nuclear

244

Theoretical analysis of magnetic field interactions with aortic blood flow  

SciTech Connect

The flow of blood in the presence of a magnetic field gives rise to induced voltages in the major arteries of the central circulatory system. Under certain simplifying conditions, such as the assumption that the length of major arteries (e.g., the aorta) is infinite and that the vessel walls are not electrically conductive, the distribution of induced voltages and currents within these blood vessels can be calculated with reasonable precision. However, the propagation of magnetically induced voltages and currents from the aorta into neighboring tissue structures such as the sinuatrial node of the heart has not been previously determined by any experimental or theoretical technique. In the analysis presented in this paper, a solution of the complete Navier-Stokes equation was obtained by the finite element technique for blood flow through the ascending and descending aortic vessels in the presence of a uniform static magnetic field. Spatial distributions of the magnetically induced voltage and current were obtained for the aortic vessel and surrounding tissues under the assumption that the wall of the aorta is electrically conductive. Results are presented for the calculated values of magnetically induced voltages and current densities in the aorta and surrounding tissue structures, including the sinuatrial node, and for their field-strength dependence. In addition, an analysis is presented of magnetohydrodynamic interactions that lead to a small reduction of blood volume flow at high field levels above approximately 10 tesla (T). Quantitative results are presented on the offsetting effects of oppositely directed blood flows in the ascending and descending aortic segments, and a quantitative estimate is made of the effects of assuming an infinite vs. a finite length of the aortic vessel in calculating the magnetically induced voltage and current density distribution in tissue.

Kinouchi, Y.; Yamaguchi, H. [Univ. of Tokushima (Japan)] [Univ. of Tokushima (Japan); Tenforde, T.S. [Pacific Northwest Lab., Richland, WA (United States). Health Div.] [Pacific Northwest Lab., Richland, WA (United States). Health Div.

1996-04-01

245

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

246

Magnetic Field Problem: Ampere's Law  

NSDL National Science Digital Library

A wire with current flowing through it perpendicular to the page is shown (position is given in meters and the integral is given in 10-10 Tesla-meters). Also shown is a choice of two detectors that displays the integral,

Christian, Wolfgang; Belloni, Mario

2007-03-03

247

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.

248

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

249

Avascular necrosis of the capitate demonstrated on a 0.064 T magnet.  

PubMed

We report the first case of avascular necrosis of a carpal bone to be imaged on a 0.064 Tesla magnet, one of the lowest field strength magnetic resonance imaging systems currently available. PMID:2607908

Haygood, T M; Eisenberg, B; Hays, M B; García, J F; Williamson, M R

1989-01-01

250

Use of a radio frequency shield during 1.5 and 3.0 Tesla magnetic resonance imaging: experimental evaluation  

PubMed Central

Radiofrequency (RF) shields have been recently developed for the purpose of shielding portions of the patient’s body during magnetic resonance imaging (MRI) examinations. We present an experimental evaluation of a commercially available RF shield in the MRI environment. All tests were performed on 1.5 T and 3.0 T clinical MRI scanners. The tests were repeated with and without the RF shield present in the bore, for comparison. Effects of the shield, placed within the scanner bore, on the RF fields generated by the scanner were measured directly using tuned pick-up coils. Attenuation, by as much as 35 dB, of RF field power was found inside the RF shield. These results were supported by temperature measurements of metallic leads placed inside the shield, in which no measurable RF heating was found. In addition, there was a small, simultaneous detectable increase (?1 dB) of RF power just outside the edges of the shield. For these particular scanners, the autocalibrated RF power levels were reduced for scan locations prescribed just outside the edges of the shield, which corresponded with estimations based on the pick-up coil measurements. Additionally, no significant heating during MRI scanning was observed on the shield surface. The impact of the RF shield on the RF fields inside the magnet bore is likely to be dependent on the particular model of the RF shield or the MRI scanner. These results suggest that the RF shield could be a valuable tool for clinical MRI practices. PMID:25378957

Favazza, Christopher P; King, Deirdre M; Edmonson, Heidi A; Felmlee, Joel P; Rossman, Phillip J; Hangiandreou, Nicholas J; Watson, Robert E; Gorny, Krzysztof R

2014-01-01

251

EXPLORER 10 MAGNETIC FIELD MEASUREMENTS  

Microsoft Academic Search

Magnetic field measurements made by means of Explorer 10 over geocentric ; distances of 1.8 to 42.6R\\/sub e\\/ on March 25experiment on the same satellite are ; referenced in interpretations. The close-in data are consistent with the ; existence of a very weak ring current below 3R\\/sub e\\/ along the trajectory, but ; alternative explanations for the field deviations are

J. P. Heppner; N. F. Ness; C. S. Scearce; T. L. Skillman

1963-01-01

252

Some features of bulk melt-textured high-temperature superconductors subjected to alternating magnetic fields  

NASA Astrophysics Data System (ADS)

Monolithic, large grain, (RE)Ba2Cu3O7 high-temperature superconductors (where RE denotes a rare-earth ion) are known to be able to trap fields in excess of several teslas and represent thus an extremely promising competing technology for permanent magnet in several applications, e.g. in motors and generators. In any rotating machine, however, the superconducting permanent magnet is subjected to variable (transient, or alternating) parasitic magnetic fields. These magnetic fields interact with the superconductor, which yields a reduction of the remnant magnetization. In the present work we quantify these effects by analysing selected experimental data on bulk melt-textured superconductors subjected to AC fields. Our results indicate that the non-uniformity of superconducting properties in rather large samples might lead to unusual features and need to be taken into account to analyse the experimental data. We also investigate the evolution of the DC remnant magnetization of the bulk sample when it is subjected to a large number of AC magnetic field cycles, and investigate the experimental errors that result from a misorientation of the sample or a mispositioning of the Hall probe. The time-dependence of the remnant magnetization over 100000 cycles of the AC field is shown to display distinct regimes which all differ strongly from the usual decay due to magnetic relaxation.

Vanderbemden, P.; Molenberg, I.; Simeonova, P.; Lovchinov, V.

2014-12-01

253

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

254

Magnetic Field - Stellar Winds Interaction  

NASA Astrophysics Data System (ADS)

As per the recent study by the MiMeS collaboration, only about 10% of massive stars possess organized global magnetic fields, typically dipolar in nature. The competition between such magnetic fields and highly non-linear radiative forces that drive the stellar winds leads to a highly complex interaction. Such an interplay can lead to a number of observable phenomena, e.g. X-ray, wind confinement, rapid stellar spindown. However, due to its complexity, such an interaction cannot usually be modeled analytically, instead numerical modeling becomes a necessary tool. In this talk, I will discuss how numerical magnetohydrodynamic (MHD) simulations are employed to understand the nature of such magnetized massive star winds.

ud-Doula, Asif

2015-01-01

255

How to Draw Magnetic Fields - I  

NSDL National Science Digital Library

This is an activity about depicting magnetic fields. Learners will observe two provided drawings of magnetic field line patterns for bar magnets in simple orientations of like and unlike polarities and carefully draw the field lines for both orientations. This is the third activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website.

256

Studies of solar magnetic fields  

Microsoft Academic Search

The telescope, spectrograph, and magnetograph at the 150-ft Tower Telescope are described, and a chronology of changes in the instrumentation is given. The average magnetic field strengths over the last seven years are discussed. The changes in polarity at the poles of the Sun are described. The characteristics of these polarity reversals at both poles are similar. A reversal is

Robert Howard

1974-01-01

257

TESLA-Report 1995-11 TESLA-Report 1995-11  

E-print Network

#12;TESLA-Report 1995-11 #12;TESLA-Report 1995-11 #12;TESLA-Report 1995-11 #12;TESLA-Report 1995-11 #12;TESLA-Report 1995-11 #12;TESLA-Report 1995-11 #12;TESLA-Report 1995-11 #12;TESLA-Report 1995-11 #12;TESLA-Report 1995-11 #12;TESLA-Report 1995-11 #12;TESLA-Report 1995-11 #12;TESLA-Report 1995

258

TESLA-Report 1993-33 TESLA-Report 1993-33  

E-print Network

#12;TESLA-Report 1993-33 #12;TESLA-Report 1993-33 #12;TESLA-Report 1993-33 #12;TESLA-Report 1993-33 #12;TESLA-Report 1993-33 #12;TESLA-Report 1993-33 #12;TESLA-Report 1993-33 #12;TESLA-Report 1993-33 #12;TESLA-Report 1993-33 #12;TESLA-Report 1993-33 #12;TESLA-Report 1993-33 #12;TESLA-Report 1993

259

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

260

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. PMID:24400100

Wrede, Karsten H.; Dammann, Philipp; Mönninghoff, Christoph; Johst, Sören; Maderwald, Stefan; Sandalcioglu, I. Erol; Müller, Oliver; Özkan, Neriman; Ladd, Mark E.; Forsting, Michael; Schlamann, Marc U.; Sure, Ulrich; Umutlu, Lale

2014-01-01

261

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

262

Effects of resistive magnetic field on fast electron divergence measured in experiments  

NASA Astrophysics Data System (ADS)

Transport of fast electrons driven by an ultraintense laser through a tracer layer buried in solid targets is studied by particle-in-cell simulations. It is found that intense resistive magnetic fields, having a magnitude of several thousand Tesla, are generated at the interfaces of the materials due to the steep resistivity gradient between the target and tracer layer. Such magnetic fields can significantly inhibit the fast electron propagation. The electrons that can penetrate the first interface are mostly confined in the buried layer by the magnetic fields and cause heating of the tracer layer. The lateral extent of the heated region can be significantly larger than that of the relativistic electron beam. This finding suggests that the relativistic electron divergence inferred from K? x-ray emission in experiments might be overestimated.

Yang, X. H.; Zhuo, H. B.; Ma, Y. Y.; Xu, H.; Yu, T. P.; Zou, D. B.; Ge, Z. Y.; Xu, B. B.; Zhu, Q. J.; Shao, F. Q.; Borghesi, M.

2015-02-01

263

Electromagnetically superconducting phase of QCD vacuum induced by strong magnetic field  

SciTech Connect

In this talk we discuss our recent suggestion that the QCD vacuum in a sufficiently strong magnetic field (stronger than 10{sup 16} Tesla) may undergo a spontaneous transition to an electromagnetically superconducting state. The possible superconducting state is anisotropic (the vacuum exhibits superconductivity only along the axis of the uniform magnetic field) and inhomogeneous (in the transverse directions the vacuum structure shares similarity with the Abrikosov lattice of an ordinary type-II superconductor). The electromagnetic superconductivity of the QCD vacuum is suggested to occur due to emergence of specific quark-antiquark condensates which carry quantum numbers of electrically charged rho mesons. A Lorentz-covariant generalization of the London transport equations for the magnetic-field-induced superconductivity is given.

Chernodub, M. N. [CNRS, Laboratoire de Mathematiques et Physique Theorique, Universite Francois-Rabelais Tours, Federation Denis Poisson, Parc de Grandmont, 37200 Tours (France); Department of Physics and Astronomy, University of Gent, Krijgslaan 281, S9, B-9000 Gent (Belgium)

2011-05-23

264

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. PMID:23564996

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

265

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. PMID:22706029

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

2012-01-01

266

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

267

Field errors in superconducting magnets  

SciTech Connect

The mission of this workshop is a discussion of the techniques for tracking particles through arbitrary accelerator field configurations to look for dynamical effects that are suggested by various theoretical models but are not amenable to detailed analysis. A major motivation for this type of study is that many of our accelerator projects are based on the use of superconducting magnets which have field imperfections that are larger and of a more complex nature than those of conventional magnets. Questions such as resonances, uncorrectable closed orbit effects, coupling between planes, and diffusion mechanisms all assume new importance. Since, simultaneously, we are trying to do sophisticated beam manipulations such as stacking, high current accelerator, long life storage, and low loss extraction, we clearly need efficient and accurate tracking programs to proceed with confidence.

Barton, M.Q.

1982-01-01

268

Development Trends in High Field Magnet Technology  

Microsoft Academic Search

The production of high magnetic fields using low temperature superconductors (LTS) has become common place. However, large magnet sizes and associated high cooling costs have often precluded the full utilization of these research capabilities. Recent advances in internal Sn superconductors and cryogen free technology have opened up a new era in superconducting magnet development. Ultra-compact, laboratory sized magnets producing fields

R. Harrison; R. Bateman; J. Brown; F. Domptail; C. M. Friend; P. Ghoshal; C. King; A. Van der Linden; Z. Melhem; P. Noonan; A. Twin; M. Field; S. Hong; J. Parrell; Y. Zhang

2008-01-01

269

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

270

Variability in Martian Magnetic Field Topology  

NASA Astrophysics Data System (ADS)

We have determined the locations of open and closed magnetic field lines at Mars as a function of four different controlling influences: solar wind magnetic field direction, solar wind pressure, martian season, and solar EUV flux.

Brain, D. A.; Halekas, J. S.; Eastwood, J. P.; Ulusen, D.; Lillis, R. J.

2014-07-01

271

Plasma stability in a dipole magnetic field  

E-print Network

The MHD and kinetic stability of an axially symmetric plasma, confined by a poloidal magnetic field with closed lines, is considered. In such a system the stabilizing effects of plasma compression and magnetic field ...

Simakov, Andrei N., 1974-

2001-01-01

272

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

273

Topological constraints in magnetic field relaxation  

NASA Astrophysics Data System (ADS)

Stability and reconnection of magnetic fields play a fundamental role in natural and manmade plasma. In these applications the field's topology determines the stability of the magnetic field. Here I will describe the importance of one topology quantifier, the magnetic helicity, which impedes any free decay of the magnetic energy. Further constraints come from the fixed point index which hinders the field to relax into the Taylor state.

Candelaresi, S.

2014-10-01

274

In Vivo 7.0-Tesla Magnetic Resonance Imaging of the Wrist and Hand: Technical Aspects and Applications  

PubMed Central

Magnetic resonance imaging (MRI) at 7.0 T has the potential for higher signal-to-noise ratio (SNR), improved spectral resolution, and faster imaging compared with 1.5-T and 3.0-T MR systems. This is especially interesting for challenging imaging regions like the wrist and the hand because of the small size of the visualized anatomical structures; the increase in SNR could then be directly converted into higher spatial resolution of the images. Practically, imaging at 7.0 T poses a variety of technical challenges such as static (B0) and radiofrequency (B1) homogeneities, shimming, chemical shift artifacts, susceptibility artifacts, alterations in tissue contrast, specific absorption rate limitations, coil construction, and pulse sequence tuning. Despite these limitations, this first experience in anatomical imaging of the wrist and the hand at 7.0 T is very promising. Functional imaging techniques will gain importance at ultra-high-field MRI and need to be assessed in detail in the future. PMID:19235674

Friedrich, Klaus M.; Chang, Gregory; Vieira, Renata L. R.; Wang, Ligong; Wiggins, Graham C.; Schweitzer, Mark E.; Regatte, Ravinder R.

2013-01-01

275

Anomalous global strings and primordial magnetic fields  

SciTech Connect

We propose a new mechanism for the generation of primordial magnetic fields, making use of the magnetic fields which are induced by anomalous global strings, such as pion and axion strings, which couple to electromagnetism via Wess-Zumino type interactions. We calculate the magnitude and coherence length of these fields. They are seen to depend on the string dynamics. With optimistic assumptions, both the magnitude and coherence scale of the induced magnetic fields can be large enough to explain the seed magnetic fields of greater than 10{sup {minus}23} G necessary to produce the observed galactic magnetic fields via the galactic dynamo mechanism. {copyright} {ital 1999} {ital The American Physical Society}

Brandenberger, R.H. [Department of Physics, Brown University, Providence, Rhode Island 02912 (United States)] [Department of Physics, Brown University, Providence, Rhode Island 02912 (United States); Zhang, X. [CCAST (World Laboratory), P.O. Box 8730, Beijing 100080, Peoples Republic of (China)] [CCAST (World Laboratory), P.O. Box 8730, Beijing 100080, Peoples Republic of (China); [Institute of High Energy Physics, Academia Sinica, Beijing 100039, Peoples Republic of (China)

1999-04-01

276

TESLA FEL Report 1996-07 TESLA FEL Report 1996-07  

E-print Network

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277

TESLA FEL Report 1996-06 TESLA FEL Report 1996-06  

E-print Network

TESLA FEL Report 1996-06 #12;TESLA FEL Report 1996-06 #12;TESLA FEL Report 1996-06 #12;TESLA FEL Report 1996-06 #12;TESLA FEL Report 1996-06 #12;TESLA FEL Report 1996-06 #12;TESLA FEL Report 1996-06 #12;TESLA FEL Report 1996-06 #12;TESLA FEL Report 1996-06 #12;TESLA FEL Report 1996-06 #12;TESLA FEL Report

278

High field, thin section nuclear magnetic resonance imaging of the cervical spine  

Microsoft Academic Search

The recent development of contiguous thin section (2 mm) imaging utilizing a high field (1.5 tesla magnetic resonance imaging)\\u000a (MR) system has remarkably improved the precision of spinal cord diagnosis. Imaging was performed using three-dimensional\\u000a data acquisition which generated twelve contiguous T1-weighted sections. Each section is reconstructed from a true 512×512\\u000a data matrix.\\u000a \\u000a Sixty patients with cervical cord lesions were

Gary J. Dee; Jaqueline A. Bello; Sadek K. Hilal

1986-01-01

279

Applied Magnetic Field Enhances Arc Vapor Deposition  

NASA Technical Reports Server (NTRS)

Applied magnetic field enhances performance of vaporization part of arc vapor deposition apparatus. When no magnetic field applied by external means, arc wonders semirandomly over cathode, with net motion toward electrical feedthrough. When magnetic field applied arc moves circumferentially around cathode, and downward motion suppressed.

Miller, T. A.; Loutfy, R. O.; Withers, J. C.

1993-01-01

280

Mars: a magnetic field due to thermoremanence?  

Microsoft Academic Search

Presently available magnetic field data suggest a dipole moment of Mars of less than 10?4 times the Earth's dipole moment. Presumably, Mars does not have an active dynamo at present which could give rise to a significant magnetic field. Nevertheless, the presently available data do not rule out a minor intrinsic field which may originate from a magnetized lithosphere. The

Martin Leweling; Tilman Spohn

1997-01-01

281

MAXWELLIAN FIELD EXPANSION OF HELICAL MAGNET  

Microsoft Academic Search

Three dimensional (3D) magnetic field calculated by the computer code TOSCA was analyzed including the fring- ing field region. The magnetic field in the median plane was well simulated by a simple function. Off median plane, contributions from the coils should be taken into account. Superconducting helical dipole magnets will be used in RHIC as Siberian snakes and rotators(1). Extensive

K. Hatanaka; T. Katayama; T. Tominaka

1998-01-01

282

Prediction of the interplanetary magnetic field strength  

Microsoft Academic Search

A new model of the coronal and interplanetary magnetic field can predict both the interplanetary magnetic field strength and its polarity from measurements of the photospheric magnetic field. The model includes the effects of the large-scale horizontal electric currents flowing in the inner corona, of the warped heliospheric current sheet in the upper corona, and of volume currents flowing in

Xuepu Zhao; J. Todd Hoeksema

1995-01-01

283

CORONAL MAGNETIC FIELD MEASUREMENTS THROUGH GYRORESONANCE EMISSION  

E-print Network

observations have provided a direct measurement of magnetic field strengths in the solar corona. It is a happy probes of the magnetic field strength above active regions, and this unique capability is one to a different magnetic field strength, the coronal structure can be "peeled away" by using different frequencies

White, Stephen

284

Design and analysis of high-field quasi-continuous magnets  

SciTech Connect

Pulsed magnets of 60 tesla or more with a flat-top of 100 ms (quasi-continuous) are among the user facilities to be provided by the NHMFL. The design of such magnets is constrained by available materials and thermal recycle time. The design path discussed here tailors materials and current densities or independent concentric coils. The progressive design steps are Illustrated by a specific example of an eight-coil, 60T magnet. In the preliminary design stage closed form calculations of magnetic, structural, thermal, and electrical circuit behavior are used to achieve a practical design that meets Initial requirements. Design refinement incorporates finite element analyses and test results on materials, fabrication and prototypes. Higher fields are possible without large changes.

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.; Van Bockstal, L. [National High Magnetic Field Lab., Tallahassee, FL (United States)

1993-10-01

285

Magnetic-field-induced superconductivity and superfluidity of W and Z bosons: in tandem transport and kaleidoscopic vortex states  

E-print Network

We show that in a background of a sufficiently strong magnetic field the electroweak sector of the quantum vacuum exhibits superconducting and, simultaneously, superfluid properties due to magnetic-field-induced condensation of, respectively, W and Z bosons. The phase transition to the "tandem" superconductor--superfluid phase - which is weakly sensitive to the Higgs sector of the standard model - occurs at the critical magnetic field of 10^{20} Tesla. The superconductor-superfluid phase has anisotropic transport properties as both charged and neutral superflows may propagate only along the magnetic field axis. The ground state possesses an unusual "kaleidoscopic" structure made of a hexagonal lattice of superfluid vortices superimposed on a triangular lattice of superconductor vortices. A weak electric field will induce both superconducting and, unexpectedly, superfluid flows.

Chernodub, M N; Verschelde, Henri

2013-01-01

286

Magnetic monopole and the nature of the static magnetic field  

E-print Network

We investigate the factuality of the hypothetical magnetic monopole and the nature of the static magnetic field. It is shown from many aspects that the concept of the massive magnetic monopoles clearly is physically untrue. We argue that the static magnetic field of a bar magnet, in fact, is the static electric field of the periodically quasi-one-dimensional electric-dipole superlattice, which can be well established in some transition metals with the localized d-electron. This research may shed light on the perfect unification of magnetic and electrical phenomena.

Xiuqing Huang

2008-12-10

287

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

288

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

289

Harmonic undulator radiations with constant magnetic field  

NASA Astrophysics Data System (ADS)

Harmonic undulators has been analysed in the presence of constant magnetic field along the direction of main undulator field. The spectrum modifications in harmonic undulator radiations and intensity degradation as a function of constant magnetic field magnitude at fundamental and third harmonics have been evaluated with a numerical integration method and generalised Bessel function. The role of harmonic field to overcome the intensity reduction due to constant magnetic field and energy spread in electron beam has also been demonstrated.

Jeevakhan, Hussain; Mishra, G.

2015-01-01

290

Features of the Martian Magnetic Field Structure  

Microsoft Academic Search

Based on the single-fluid MHD model of Mars space simulation, this paper has studied the magnetic field structure in the near-Mars space and investigated the influence of Martian crustal magnetic anomalies on the magnetic field structure. In the process of the solar wind interaction with Mars, the bow shock and magnetic pile-up region are produced. The interplanetary magnetic lines are

Yi-Teng Zhang; Lei Li

2009-01-01

291

How to Draw Magnetic Fields - II  

NSDL National Science Digital Library

This is an activity about depicting magnetic polarity. Learners will observe several provided drawings of magnetic field line patterns for bar magnets in simple orientations of like and unlike polarities and carefully draw the field lines and depict the polarities for several orientations, including an arrangement of six magnetic poles. This is the fourth activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website.

292

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. PMID:18957714

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

2009-01-01

293

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

294

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. PMID:24701187

Periyasamy, M.; Dhanasekaran, R.

2014-01-01

295

Inter-study reproducibility of arterial spin labelling magnetic resonance imaging for measurement of renal perfusion in healthy volunteers at 3 Tesla  

PubMed Central

Background Measurement of renal perfusion is a crucial part of measuring kidney function. Arterial spin labelling magnetic resonance imaging (ASL MRI) is a non-invasive method of measuring renal perfusion using magnetised blood as endogenous contrast. We studied the reproducibility of ASL MRI in normal volunteers. Methods ASL MRI was performed in healthy volunteers on 2 occasions using a 3.0 Tesla MRI scanner with flow-sensitive alternating inversion recovery (FAIR) perfusion preparation with a steady state free precession (True-FISP) pulse sequence. Kidney volume was measured from the scanned images. Routine serum and urine biochemistry were measured prior to MRI scanning. Results 12 volunteers were recruited yielding 24 kidneys, with a mean participant age of 44.1 ± 14.6 years, blood pressure of 136/82 mmHg and chronic kidney disease epidemiology formula estimated glomerular filtration rate (CKD EPI eGFR) of 98.3 ± 15.1 ml/min/1.73 m2. Mean kidney volumes measured using the ellipsoid formula and voxel count method were 123.5 ± 25.5 cm3, and 156.7 ± 28.9 cm3 respectively. Mean kidney perfusion was 229 ± 41 ml/min/100 g and mean cortical perfusion was 327 ± 63 ml/min/100 g, with no significant differences between ASL MRIs. Mean absolute kidney perfusion calculated from kidney volume measured during the scan was 373 ± 71 ml/min. Bland Altman plots were constructed of the cortical and whole kidney perfusion measurements made at ASL MRIs 1 and 2. These showed good agreement between measurements, with a random distribution of means plotted against differences observed. The intra class correlation for cortical perfusion was 0.85, whilst the within subject coefficient of variance was 9.2%. The intra class correlation for whole kidney perfusion was 0.86, whilst the within subject coefficient of variance was 7.1%. Conclusions ASL MRI at 3.0 Tesla provides a repeatable method of measuring renal perfusion in healthy subjects without the need for administration of exogenous compounds. We have established normal values for renal perfusion using ASL MRI in a cohort of healthy volunteers. PMID:24484613

2014-01-01

296

Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization  

DOEpatents

In a plasma-producing device, an optimized magnet field for electron cyclotron resonance plasma generation is provided by a shaped pole piece. The shaped pole piece adjusts spacing between the magnet and the resonance zone, creates a convex or concave resonance zone, and decreases stray fields between the resonance zone and the workpiece. For a cylindrical permanent magnet, the pole piece includes a disk adjacent the magnet together with an annular cylindrical sidewall structure axially aligned with the magnet and extending from the base around the permanent magnet. The pole piece directs magnetic field lines into the resonance zone, moving the resonance zone further from the face of the magnet. Additional permanent magnets or magnet arrays may be utilized to control field contours on a local scale. Rather than a permeable material, the sidewall structure may be composed of an annular cylindrical magnetic material having a polarity opposite that of the permanent magnet, creating convex regions in the resonance zone. An annular disk-shaped recurve section at the end of the sidewall structure forms magnetic mirrors keeping the plasma off the pole piece. A recurve section composed of magnetic material having a radial polarity forms convex regions and/or magnetic mirrors within the resonance zone.

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

2000-12-19

297

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

298

Vlasov Equation In Magnetic Field  

E-print Network

The linearized Vlasov equation for a plasma system in a uniform magnetic field and the corresponding linear Vlasov operator are studied. The spectrum and the corresponding eigenfunctions of the Vlasov operator are found. The spectrum of this operator consists of two parts: one is continuous and real; the other is discrete and complex. Interestingly, the real eigenvalues are infinitely degenerate, which causes difficulty solving this initial value problem by using the conventional eigenfunction expansion method. Finally, the Vlasov equation is solved by the resolvent method.

Biao Wu

1999-09-07

299

An analytic solar magnetic field model  

Microsoft Academic Search

We describe a simple analytic model for the magnetic field in the solar corona and interplanetary space which is appropriate to solar minimum conditions. The model combines an azimuthal current sheet in the equatorial plane with an axisymmetric multipole field representing the internal magnetic field of the Sun. The radial component of the field filling interplanetary space is approximately monopolar

M. Banaszkiewicz; W. I. Axford; J. F. McKenzie

1998-01-01

300

On the origin of solar magnetic fields  

Microsoft Academic Search

A fresh approach to the theoretical problems raised by observations of solar magnetic fields is outlined. Tentative conclusions are made that the large-scale magnetic field from which Cowling's (1953) hypothetical toroidal field is generated by differential rotation is not itself regenerated by diffusive processes in the sun's outer layers and that this field enters the differentially rotating layer from below

D. Layzer; R. Rosner; H. T. Doyle

1979-01-01

301

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

302

Full 180° magnetization reversal with electric fields.  

PubMed

Achieving 180° magnetization reversal with an electric field rather than a current or magnetic field is a fundamental challenge and represents a technological breakthrough towards new memory cell designs. Here we propose a mesoscale morphological engineering approach to accomplishing full 180° magnetization reversals with electric fields by utilizing both the in-plane piezostrains and magnetic shape anisotropy of a multiferroic heterostructure. Using phase-field simulations, we examined a patterned single-domain nanomagnet with four-fold magnetic axis on a ferroelectric layer with electric-field-induced uniaxial strains. We demonstrated that the uniaxial piezostrains, if non-collinear to the magnetic easy axis of the nanomagnet at certain angles, induce two successive, deterministic 90° magnetization rotations, thereby leading to full 180° magnetization reversals. PMID:25512070

Wang, J J; Hu, J M; Ma, J; Zhang, J X; Chen, L Q; Nan, C W

2014-01-01

303

Full 180° Magnetization Reversal with Electric Fields  

NASA Astrophysics Data System (ADS)

Achieving 180° magnetization reversal with an electric field rather than a current or magnetic field is a fundamental challenge and represents a technological breakthrough towards new memory cell designs. Here we propose a mesoscale morphological engineering approach to accomplishing full 180° magnetization reversals with electric fields by utilizing both the in-plane piezostrains and magnetic shape anisotropy of a multiferroic heterostructure. Using phase-field simulations, we examined a patterned single-domain nanomagnet with four-fold magnetic axis on a ferroelectric layer with electric-field-induced uniaxial strains. We demonstrated that the uniaxial piezostrains, if non-collinear to the magnetic easy axis of the nanomagnet at certain angles, induce two successive, deterministic 90° magnetization rotations, thereby leading to full 180° magnetization reversals.

Wang, J. J.; Hu, J. M.; Ma, J.; Zhang, J. X.; Chen, L. Q.; Nan, C. W.

2014-12-01

304

Full 180° Magnetization Reversal with Electric Fields  

PubMed Central

Achieving 180° magnetization reversal with an electric field rather than a current or magnetic field is a fundamental challenge and represents a technological breakthrough towards new memory cell designs. Here we propose a mesoscale morphological engineering approach to accomplishing full 180° magnetization reversals with electric fields by utilizing both the in-plane piezostrains and magnetic shape anisotropy of a multiferroic heterostructure. Using phase-field simulations, we examined a patterned single-domain nanomagnet with four-fold magnetic axis on a ferroelectric layer with electric-field-induced uniaxial strains. We demonstrated that the uniaxial piezostrains, if non-collinear to the magnetic easy axis of the nanomagnet at certain angles, induce two successive, deterministic 90° magnetization rotations, thereby leading to full 180° magnetization reversals. PMID:25512070

Wang, J. J.; Hu, J. M.; Ma, J.; Zhang, J. X.; Chen, L. Q.; Nan, C. W.

2014-01-01

305

Superconducting TESLA cavities  

Microsoft Academic Search

The conceptional design of the proposed linear electron-positron collider TESLA is based on 9-cell 1.3 GHz superconducting niobium cavities with an accelerating gradient of Eacc>=25 MV\\/m at a quality factor Q0>=5×109. The design goal for the cavities of the TESLA Test Facility (TTF) linac was set to the more moderate value of Eacc>=15 MV\\/m. In a first series of 27

B. Aune; R. Bandelmann; D. Bloess; B. Bonin; A. Bosotti; M. Champion; C. Crawford; G. Deppe; B. Dwersteg; D. A. Edwards; H. T. Edwards; M. Ferrario; M. Fouaidy; P.-D. Gall; A. Gamp; A. Gössel; J. Graber; D. Hubert; M. Hüning; M. Juillard; T. Junquera; H. Kaiser; G. Kreps; M. Kuchnir; R. Lange; M. Leenen; M. Liepe; L. Lilje; A. Matheisen; W.-D. Möller; A. Mosnier; H. Padamsee; C. Pagani; M. Pekeler; H.-B. Peters; O. Peters; D. Proch; K. Rehlich; D. Reschke; H. Safa; T. Schilcher; P. Schmüser; J. Sekutowicz; S. Simrock; W. Singer; M. Tigner; D. Trines; K. Twarowski; G. Weichert; J. Weisend; J. Wojtkiewicz; S. Wolff; K. Zapfe

2000-01-01

306

Scanning localized magnetic fields in a microfluidic device with a single nitrogen vacancy center  

E-print Network

Nitrogen vacancy (NV) color centers in diamond have emerged as highly versatile optical emitters that exhibit room temperature spin properties. These characteristics make NV centers ideal for magnetometry, which plays an important role in chemical and biological sensing applications. The integration of NV magnetometers with microfluidic systems could enable the study of isolated chemical and biological samples in a fluid environment with high spatial resolution. Here we demonstrate a method to perform localized magnetometry with nanometer spatial precision using a single NV center in a microfluidic device. We manipulate a magnetic particle within a liquid environment using a combination of planar microfluidic flow control and vertical magnetic actuation to achieve 3-dimensional manipulation. A diamond nanocrystal containing a single NV center is deposited in the microfluidic channels and acts as a local magnetic field probe. We map out the magnetic field distribution of the magnetic particle by varying its position relative to the diamond nanocrystal and performing optically resolved electron spin resonance (ESR) measurements. We control the magnetic particle position with a 48 nm precision and attain a magnetic field sensitivity of 17.5 microTesla/Hz^1/2. These results open up the possibility for studying local magnetic properties of biological and chemical systems with high sensitivity in an integrated microfluidic platform.

Kangmook Lim; Chad Ropp; Benjamin Shapiro; Jacob M. Taylor; Edo Waks

2014-08-01

307

Sub arcsec evolution of solar magnetic fields  

Microsoft Academic Search

Context: .The evolution of the concentrated magnetic field in flux tubes is one challenge of the nowadays Solar physics which requires time sequence with high spatial resolution. Aims: .Our objective is to follow the properties of the magnetic concentrations during their life, in intensity (continuum and line core), magnetic field and Doppler velocity. Methods: .We have observed solar region NOAA

Th. Roudier; J. M. Malherbe; J. Moity; S. Rondi; P. Mein; Ch. Coutard

2006-01-01

308

Exploring Magnetic Fields with a Compass  

ERIC Educational Resources Information Center

A compass is an excellent classroom tool for the exploration of magnetic fields. Any student can tell you that a compass is used to determine which direction is north, but when paired with some basic trigonometry, the compass can be used to actually measure the strength of the magnetic field due to a nearby magnet or current-carrying wire. In this…

Lunk, Brandon; Beichner, Robert

2011-01-01

309

Discovery of Magnetic Fields in CPNs  

NASA Astrophysics Data System (ADS)

For the first time we have directly detected magnetic fields in central stars of planetary nebulae by means of spectro-polarimetry with FORS1 at the VLT. In all four objects of our sample we found kilogauss magnetic fields, in NGC 1360 and LSS 1362 with very high significance, while in Abell 36 and EGB 5 the existence of a magnetic field is probable but with less certainty. This discovery supports the hypothesis that the non-spherical symmetry of most planetary nebulae is caused by magnetic fields in AGB stars. Our high discovery rate demands mechanisms to prevent full conservation of magnetic flux during the transition to white dwarfs.

Jordan, S.; Werner, K.; O'Toole, S. J.

2005-07-01

310

Neutrino Conversions in Solar Random Magnetic Fields  

E-print Network

We consider the effect of a random magnetic field in the convective zone of the Sun superimposed to a regular magnetic field on resonant neutrino spin-flavour oscillations. We argue for the existence of a field of strongly chaotic nature at the bottom of the convective zone. In contrast to previous attempts we employ in addition a model motivated regular twisting magnetic field profile. In this scenario electron antineutrinos are produced through cascades like $\

V. B Semikoz; E. Torrente-Lujan

1998-09-16

311

Differential rotation of solar magnetic fields  

Microsoft Academic Search

The connection of the differential rotation of solar magnetic fields with the field sign and strength is studied. The synoptic\\u000a maps of magnetic fields over the last three solar cycles taken at the Kitt Peak Observatory served as input data for the study.\\u000a The algorithm of magnetic field filtering over 14 chosen strengt intervals and successive 5-degree latitude zones was

O. A. Andreyeva; Ya. I. Zyelyk; N. N. Stepanian

2008-01-01

312

Magnetic field waves at Uranus  

NASA Technical Reports Server (NTRS)

The research efforts funded by the Uranus Data Analysis Program (UDAP) grant to the Bartol Research Institute (BRI) involved the study of magnetic field waves associated with the Uranian bow shock. Upstream wave studies are motivated as a study of the physics of collisionless shocks. Collisionless shocks in plasmas are capable of 'reflecting' a fraction of the incoming thermal particle distribution and directing the resulting energetic particle motion back into the upstream region. Once within the upstream region, the backward streaming energetic particles convey information of the approaching shock to the supersonic flow. This particle population is responsible for the generation of upstream magnetic and electrostatic fluctuations known as 'upstream waves', for slowing the incoming wind prior to the formation of the shock ramp, and for heating of the upstream plasma. The waves produced at Uranus not only differed in several regards from the observations at other planetary bow shocks, but also gave new information regarding the nature of the reflected particle populations which were largely unmeasurable by the particle instruments. Four distinct magnetic field wave types were observed upstream of the Uranian bow shock: low-frequency Alfven or fast magnetosonic waves excited by energetic protons originating at or behind the bow shock; whistler wave bursts driven by gyrating ion distributions within the shock ramp; and two whistler wave types simultaneously observed upstream of the flanks of the shock and argued to arise from resonance with energetic electrons. In addition, observations of energetic particle distributions by the LECP experiment, thermal particle populations observed by the PLS experiment, and electron plasma oscillations recorded by the PWS experiment proved instrumental to this study and are included to some degree in the papers and presentations supported by this grant.

Smith, Charles W.; Goldstein, Melvyn L.; Lepping, Ronald P.; Mish, William H.; Wong, Hung K.

1994-01-01

313

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

314

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

315

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.

Lubell, Martin S. (Oak Ridge, TN)

1994-01-01

316

Polar magnetic field reversals on the Sun  

NASA Astrophysics Data System (ADS)

The polar magnetic fields on the Sun have been an attractive subject for solar researches since Babcock measured them in solar cycle 19. One of the remarkable features of the polar magnetic fields is their reversal during the maxima of 11-year sunspot cycles. I have present results of the investigations of the polar magnetic field using SOHO-mdi data. It is found, that the polar magnetic field reversal is detected with mdi data for polar region within 78° 88°. The North Pole has changed polarity in CR1975 (April 2001). The South reversed later in CR1980 (September 2001). The total unsigned magnetic flux does not show the dramatic decreasing during the polar reversals due to omnipresent bi-polar small-scale magnetic elements. The observational and theoretical aspects of the polar magnetic field reversals are discussed.

Benevolenskaya, Elena E.

2007-08-01

317

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.

318

Cosmological Magnetic Fields and CMBR Polarization  

E-print Network

A simple introduction to physics of CMBR polarization and the Faraday rotation of the latter in cosmic magnetic field is presented. The content of the lecture is the following: 1. Description of polarization of photons. 2. Polarization field of CMBR. 3. Faraday effect. 4. Cosmic magnetic fields. 5. Faraday rotation of CMBR polarization.

A. D. Dolgov

2005-03-21

319

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

320

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

321

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

322

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

323

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

324

Magnetic field waves at Uranus  

NASA Technical Reports Server (NTRS)

The proposed research efforts funded by the UDAP grant to the BRI involve the study of magnetic field waves associated with the Uranian bow shock. This is a collaborative venture bringing together investigators at the BRI, Southwest Research Institute (SwRI), and Goddard Space Flight Center (GSFC). In addition, other collaborations have been formed with investigators granted UDAP funds for similar studies and with investigators affiliated with other Voyager experiments. These investigations and the corresponding collaborations are included in the report. The proposed effort as originally conceived included an examination of waves downstream from the shock within the magnetosheath. However, the observations of unexpected complexity and diversity within the upstream region have necessitated that we confine our efforts to those observations recorded upstream of the bow shock on the inbound and outbound legs of the encounter by the Voyager 2 spacecraft.

Smith, Charles W.; Goldstein, Melvyn L.; Lepping, Ronald P.; Mish, William H.; Wong, Hung K.

1991-01-01

325

Lattice distortions in magnetic fields  

NASA Astrophysics Data System (ADS)

A study is made of the stability of the possible lattice structures which result from the magnetic-field-induced lattice deformation introduced by Araujo and Khmelnitskii. The deformed lattice may either be the result of a single distortion occurring along a particular direction or of a superposition of distortions in different directions. In a noninteracting electron model the energy variation of the electron system will determine which final lattice structure is the most stable. When electron interactions are considered in the Hartree approximation we find that the energy variation of the electron system alone will not determine which final structure is the most stable. The latter is then imposed by the lattice itself. If the distortion turns out to be unidirectional then the corresponding charge-density wave should be weakly pinned even in the absence of impurities.

Araujo, Miguel A. N.

1996-09-01

326

Extraterrestrial Magnetic Fields: Achievements and Opportunities  

Microsoft Academic Search

The major scientific achievements associated with the measurement of magnetic fields in space over the past decade and a half are reviewed. Aspects of space technology relevant to magnetic-field observations are discussed, including the different types of magnetometers used and how they operate, problems arising from spacecraft-generated magnetic fields and the appropriate countermeasures that have been developed and on-board processing

EDWARD J. SMITHAND; Charles Sonett

1976-01-01

327

Dynamics of solar magnetic fields. VI  

Microsoft Academic Search

A mathematical model is developed to consider the evolution of force-free magnetic fields in relation to the displacements of their foot-points. For a magnetic field depending on only two Cartesian coordinates and time, the problem reduces to solving a nonlinear elliptic partial differential equation. As illustration of the physical process, two specific examples of evolving force-free magnetic fields are examined

B. C. Low; Y. Nakagawa

1975-01-01

328

Modeling solar force-free magnetic fields  

Microsoft Academic Search

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

B. C. Low; Y. Q. Lou

1990-01-01

329

Fractal properties of solar magnetic fields  

Microsoft Academic Search

We study the spatial properties of solar magnetic fields using data from the Solar Vector Magnetograph of the Marshall Space\\u000a Flight Center (MSFC) (FeI 5250.2 Å) and SOHO\\/MDI longitudinal magnetic field measurements (Ni 6767.8 Å) (96-min full-disk\\u000a maps). Our study is focused on two objects: the fractal properties of sunspots and the fractal properties of the spatial magnetic\\u000a field distribution

B. A. Ioshpa; V. N. Obridko; E. A. Rudenchik

2008-01-01

330

Fractal properties of solar magnetic fields  

Microsoft Academic Search

We study the spatial properties of solar magnetic fields using data from the Solar Vector Magnetograph of the Marshall Space Flight Center (MSFC) (FeI 5250.2 Å) and SOHO\\/MDI longitudinal magnetic field measurements (Ni 6767.8 Å) (96-min full-disk maps). Our study is focused on two objects: the fractal properties of sunspots and the fractal properties of the spatial magnetic field distribution

B. A. Ioshpa; V. N. Obridko; E. A. Rudenchik

2008-01-01

331

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

332

Magnetic field measurements in tokamak plasmas  

SciTech Connect

The measurement of the poloidal magnetic field in a tokamak plasma from the Zeeman splitting and polarization of the magnetic dipole radiation from heavy ions is discussed. When viewed from a direction perpendicular to the toroidal field, the effect of the poloidal field on the circularly polarized radiation is detectable using a photoelectric polarimeter. The Zeeman splittings for a number of magnetic dipole transitions with wavelengths in the range 2300--9300 A are presented. An imaging polarimeter is proposed that can measure the poloidal magnetic field with space and time resolution.

Feldman, U.; Seely, J.F.; Sheeley,Jr., N.R.; Suckewer, S.; Title, A.M.

1984-11-01

333

Magnetic fields in anisotropic relativistic stars  

E-print Network

Relativistic, spherically symmetric configurations consisting of a gravitating magnetized anisotropic fluid are studied. For such configurations, we obtain static equilibrium solutions with an axisymmetric, poloidal magnetic field produced by toroidal electric currents. The presence of such a field results in small deviations of the shape of the configuration from spherical symmetry. This in turn leads to the modification of an equation for the current and correspondingly to changes in the structure of the internal magnetic field for the systems supported by the anisotropic fluid, in contrast to the case of an isotropic fluid, where such deviations do not affect the magnetic field.

Vladimir Folomeev; Vladimir Dzhunushaliev

2015-01-26

334

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

335

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

NASA Astrophysics Data System (ADS)

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

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

2004-06-01

336

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

337

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

338

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

339

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

340

Double echo steady state magnetic resonance imaging of knee articular cartilage at 3 Tesla: a pilot study for the Osteoarthritis Initiative  

PubMed Central

Background Quantitative magnetic resonance imaging (qMRI) may provide valuable measures of cartilage morphology in osteoarthritis (OA) but has been confined to sequences with relatively long acquisition times at 1.5 Tesla (T). Objective To test the accuracy and precision of knee cartilage qMRI with a fast double echo, steady state (DESS) sequence with water excitation (we) at 3?T. Methods As a pilot study for the Osteoarthritis Initiative, test?retest MR images were acquired in the knees of 19 participants with no OA to moderate degrees of clinical OA. Two double oblique coronal fast low angle shot (FLASHwe) sequences (1.5?mm slice thickness) were acquired at 3?T, and two sagittal DESSwe sequences (0.7?mm slice thickness). Double oblique coronal multiplanar reformats (MPR) were performed (1.5?mm slice thickness) from the sagittal DESSwe. Knee joint cartilage plates were quantified unpaired in random order with blinding to subject identification. Results In the femorotibial joint, precision errors (root mean square coefficient of variation in % for unpaired analysis) for cartilage volume and thickness were 3.0–6.4% with coronal FLASHwe, 2.4–6.2% with coronal MPR DESSwe, and 2.3–8.2% with sagittal DESSwe. Correlation coefficients between DESSwe and FLASHwe ranged from r?=?0.88 to 1.0. In the femoropatellar joint, precision errors (sagittal DESSwe) were 3.4–8.5%. Conclusions DESSwe permits accurate and precise analysis of cartilage morphology in the femorotibial joint at 3?T. Further studies are needed to examine the accuracy of DESSwe in the femoropatellar joint and its ability to characterise sensitivity to longitudinal changes in cartilage morphology. PMID:16126797

Eckstein, F; Hudelmaier, M; Wirth, W; Kiefer, B; Jackson, R; Yu, J; Eaton, C B; Schneider, E

2006-01-01

341

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. PMID:23448526

2013-01-01

342

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. PMID:25045371

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

2014-01-01

343

TESLA Report 2001-38 THE TESLA CRYO-PLANTS  

E-print Network

TESLA Report 2001-38 THE TESLA CRYO-PLANTS H. Quack, M. Kauschke, C. Haberstroh, TU Dresden, 01062 The Tera-eV Energy Superconducting Linear Accelerator (TESLA) is a 32 km long superconducting linear to higher complexity 4 Single component failure not leading to total plant shutdown Motor burnout, compr

344

Measurements of Heme Relaxation and Ligand Recombination in Strong Magnetic Fields  

PubMed Central

Heme cooling signals and diatomic ligand recombination kinetics are measured in strong magnetic fields (up to 10 Tesla). We examined diatomic ligand recombination to heme model compounds (NO and CO), myoglobin (NO and O2), and horseradish peroxidase (NO). No magnetic field induced rate changes in any of the samples were observed within the experimental detection limit. However, in the case of CO binding to heme in glycerol and O2 binding to myoglobin, we observe a small magnetic field dependent change in the early time amplitude of the optical response that is assigned to heme cooling. One possibility, consistent with this observation, is that there is a weak magnetic field dependence of the non-radiative branching ratio into the vibrationally hot electronic ground state during CO photolysis. Ancillary studies of the “spin-forbidden” CO binding reaction in a variety of heme compounds in the absence of magnetic field demonstrate a surprisingly wide range for the Arrhenius prefactor. We conclude that CO binding to heme is not always retarded by unfavorable spin selection rules involving a double spin-flip superexchange mechanism. In fact, it appears that the small prefactor (~109s?1) found for CO rebinding to Mb may be anomalous, rather than the general rule for heme-CO rebinding. These results point to unresolved fundamental issues that underlie the theory of heme-ligand photolysis and rebinding. PMID:19588986

Zhang, Zhenyu; Benabbas, Abdelkrim; Ye, Xiong; Yu, Anchi; Champion, Paul M.

2009-01-01

345

Magnetic field optimization of permanent magnet undulators for arbitrary polarization  

NASA Astrophysics Data System (ADS)

Techniques for improving the magnetic field quality of APPLE II undulators are discussed. Individual block characterization including the inhomogeneities of the magnetization permits a precise prediction of field integrals as required for sorting. Specific shimming procedures adapted to the magnetic design of APPLE II undulators have to be employed in order to meet the stringent requirements of insertion devices in third generation synchrotron radiation sources as demonstrated for BESSY.

Bahrdt, J.; Frentrup, W.; Gaupp, A.; Scheer, M.; Englisch, U.

2004-01-01

346

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

347

SIMULATING MAGNETIC FIELDS IN THE ANTENNAE GALAXIES  

SciTech Connect

We present self-consistent high-resolution simulations of NGC 4038/4039 (the 'Antennae galaxies') including star formation, supernova feedback, and magnetic fields performed with the N-body/smoothed particle hydrodynamic (SPH) code GADGET, in which magnetohydrodynamics are followed with the SPH method. We vary the initial magnetic field in the progenitor disks from 10{sup -9} to 10{sup -4} G. At the time of the best match with the central region of the Antennae system, the magnetic field has been amplified by compression and shear flows to an equilibrium field value of {approx}10 {mu}G, independent of the initial seed field. These simulations are a proof of the principle that galaxy mergers are efficient drivers for the cosmic evolution of magnetic fields. We present a detailed analysis of the magnetic field structure in the central overlap region. Simulated radio and polarization maps are in good morphological and quantitative agreement with the observations. In particular, the two cores with the highest synchrotron intensity and ridges of regular magnetic fields between the cores and at the root of the southern tidal arm develop naturally in our simulations. This indicates that the simulations are capable of realistically following the evolution of the magnetic fields in a highly nonlinear environment. We also discuss the relevance of the amplification effect for present-day magnetic fields in the context of hierarchical structure formation.

Kotarba, H.; Karl, S. J.; Naab, T.; Johansson, P. H.; Lesch, H. [University Observatory Munich, Scheinerstr. 1, D-81679 Munich (Germany); Dolag, K.; Stasyszyn, F. A., E-mail: kotarba@usm.lmu.d [Max Planck Institute for Astrophysics, Karl-Schwarzschild-Str. 1, D-85741 Garching (Germany)

2010-06-20

348

Fine structure of solar magnetic fields  

Microsoft Academic Search

The deduction of magnetic fields from chromospheric structure is extended to active regions and transverse fields. Fields independently predicted by these rules from a high resolution Ha filtergram are compared with a high resolution magnetogram. The Ha method has the advantage over conventional magnetograms that it shows transverse fields and relates the fields to the real Sun. It has the

Harold Zirin

1972-01-01

349

Magnetic-field effects in non-magnetic glasses  

NASA Astrophysics Data System (ADS)

Recently, it was found that the multi-component glass a-BaO-Al2O3-SiO2 exhibits unusual magnetic properties at very low temperatures. Thus the question arises whether this is a specialty of that particular glass or a more general phenomenon. We report here on our studies of the magnetic-field dependence of the dielectric properties of the borosilicate glass BK7 which contains only a negligible amount of magnetic impurities. Since this glass also responds sensitively to magnetic fields, our investigations demonstrate that the reaction of glasses to magnetic fields is not caused by magnetic impurities but reflects a more general phenomenon. In addition, we have observed that the variation of the dielectric constant and the loss angle with magnetic field depend on the amplitude of the electric field that is used to measure the glass capacitance. We present the data and discuss possible origins of the magnetic-field phenomena in non-magnetic glasses.

Wohlfahrt, M.; Strehlow, P.; Enss, C.; Hunklinger, S.

2001-12-01

350

Thinned fiber Bragg grating magnetic field sensor with magnetic fluid  

NASA Astrophysics Data System (ADS)

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 thinned fiber Bragg grating to refractive index, series of experiments, such as the fabrication of thinned FBG, tuning magnetic field and obtaining spectral characterizations, are carried out. After the FBG is etched for 193 minutes by HF solution at 22%, the FBG starts to be sensitive to the surrounding refractive index and the Bragg wavelength decreases sharply with the etching process. The thinned FBG has been packaged to a container filled with MF. Using a tunable magnetic field the refractive index of magnetic fluid could be changed and the Bragg wavelength of FBG shifts correspondingly. Both the wavelength and the light power are sensitive to magnetic field and the sensitivity of wavelength is 2.3 pm/mT at least in the condition of proposed experiment. The obtained results show that the thinned FBG sensor with magnetic fluid could be applicable for magnetic field and current sensing.

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

2011-05-01

351

Videomagnetograph studies of solar magnetic fields  

Microsoft Academic Search

Observations of magnetic field diffusion in weak plage regions have been made using the analog videomagnetograph at the California Institute of Technology. Points of magnetic flux, usually described as ‘vertex points’ of the magnetic network, were found to have a mean lifetime of three to four days, and to disperse primarily by means of two mechanisms: a random walk with

Robert C. Smithson

1973-01-01

352

The Moessbauer effect in homogeneous magnetic field  

E-print Network

We derive the probability of the Moessbauer effect realized by the charged particle moving in the homogeneous magnetic field, or, in accelerating field. The submitted approach represents new deal of the Moessbauer physics. Key

Miroslav Pardy

2014-03-20

353

Magnetic Field Seeding through Supernova Feedback  

NASA Astrophysics Data System (ADS)

Stellar feedback occurring at small-scales can significantly impact the evolution of galaxies at much larger scales. For example, an appropriate feedback mechanism, including thermal and radiative components, can help regulate star formation, particularly in low-mass galaxies. While feedback models are generally prevalent in numerical simulations, the magnetic component is often neglected. However, measurements of galaxies indicate the presence of fields with a strength on the order of µG. Previous studies have demonstrated the formation of these fields through the amplification of a primordial magnetic field. Here, we describe a self-consistent prescription where magnetic fields are injected in supernova injections, calibrated by observations of magnetic fields in supernova remnants. These fields will then become seeds that evolve by way of mixing and turbulence to result in galactic-scale magnetic fields. As a proof of concept, we apply this method to model the supernova of a single Population III star and trace the evolution of the injected magnetic field. Future studies will apply this prescription to study not only the effects of magnetic fields on galaxy formation and evolution, but also the growth of the magnetized bubbles that form in the IGM.

Koh, Daegene; Wise, John

2015-01-01

354

Graphene Nanoribbon in Sharply Localized Magnetic Fields  

E-print Network

We study the effect of a sharply localized magnetic field on the electron transport in a strip (ribbon) of graphene sheet, which allows to give results for the transmission and reflection probability through magnetic barriers. The magnetic field is taken as a single and double delta type localized functions, which are treated later as the zero width limit of gaussian fields. For both field configurations, we evaluate analytically and numerically their transmission and reflection coefficients. The possibility of spacial confinement due to the inhomogeneous field configuration is also investigated.

Abdulaziz D. Alhaidari; Hocine Bahlouli; Abderrahim El Mouhafid; Ahmed Jellal

2011-03-21

355

SQUID-Detected Magnetic Resonance Imaging in MicroteslaFields  

SciTech Connect

Magnetic resonance imaging (MRI) has developed into a powerful clinical tool for imaging the human body (1). This technique is based on nuclear magnetic resonance (NMR) of protons (2, 3) in a static magnetic field B{sub 0}. An applied radiofrequency pulse causes the protons to precess about B{sub 0} at their Larmor frequency {nu}{sub 0} = ({gamma}/2{pi})B{sub 0}, where {gamma} is the gyromagnetic ratio; {gamma}/2{pi} = 42.58 MHz/tesla. The precessing protons generate an oscillating magnetic field and hence a voltage in a nearby coil that is amplified and recorded. The application of three-dimensional magnetic field gradients specifies a unique magnetic field and thus an NMR frequency in each voxel of the subject, so that with appropriate encoding of the signals one can acquire a complete image (4). Most clinical MRI systems involve magnetic fields generated by superconducting magnets, and the current trend is to higher magnetic fields than the widely used 1.5-T systems (5). Nonetheless, there is ongoing interest in the development of less expensive imagers operating at lower fields. Commercially available 0.2-T systems based on permanent magnets offer both lower cost and a more open access than their higher-field counterparts, at the expense of signal-to-noise-ratio (SNR) and spatial resolution. At the still lower field of 0.03 mT maintained by a conventional, room-temperature solenoid, Connolly and co-workers (6, 7) obtain good spatial resolution and signal-to-noise ratio (SNR) by prepolarizing the protons in a field B{sub p} of 0.3 T. Prepolarization (8) enhances the magnetic moment of an ensemble of protons over that produced by the lower precession field; after the polarizing field is removed, the higher magnetic moment produces a correspondingly larger signal during its precession in B{sub 0}. Using the same method, Stepisnik et al. (9) obtained MR images in the Earth's magnetic field ({approx} 50 {micro}T). Alternatively, one can enhance the signal amplitude in MRI using laser polarized noble gases such as {sup 3}He or {sup 129}Xe (10-12). Hyperpolarized gases were used successfully to image the human lung in fields on the order of several mT (13-15). To overcome the sensitivity loss of Faraday detection at low frequencies, ultrasensitive magnetometers based on the Superconducting QUantum Interference Device (SQUID) (16) are used to detect NMR and MRI signals (17-24). Recently, SQUID-based MRI systems capable of acquiring in vivo images have appeared. For example, in the 10-mT system of Seton et al. (18) signals are coupled to a SQUID via a superconducting tuned circuit, while Clarke and coworkers (22, 25, 26) developed a system at 132 {micro}T with an untuned input circuit coupled to a SQUID. In a quite different approach, atomic magnetometers have been used recently to detect the magnetization (27) and NMR signal (28) of hyperpolarized gases. This technique could potentially be used for low-field MRI in the future. The goal of this review is to summarize the current state-of-the-art of MRI in microtesla fields detected with SQUIDs. The principles of SQUIDs and NMR are briefly reviewed. We show that very narrow NMR linewidths can be achieved in low magnetic fields that are quite inhomogeneous, with illustrative examples from spectroscopy. After describing our ultralow-field MRI system, we present a variety of images. We demonstrate that in microtesla fields the longitudinal relaxation T{sub 1} is much more material dependent than is the case in high fields; this results in a substantial improvement in 'T{sub 1}-weighted contrast imaging'. After outlining the first attempts to combine microtesla NMR with magnetoencephalography (MEG) (29), we conclude with a discussion of future directions.

Moessle, Michael; Hatridge, Michael; Clarke, John

2006-08-14

356

Parker's magnetic field and relativistic jets  

NASA Astrophysics Data System (ADS)

We consider the motion of high-energy charged particles (cosmic rays) in Parker's spiral magnetic field. We show that under radial particle ejection from a sphere outside which there is Parker's magnetic field, all of the particles escaping from the sphere are focused either along the field symmetry axis or in the equatorial plane, depending on the field polarity. Based on the results obtained, we propose a possible model that explains the origin of relativistic jets.

Kichigin, G. N.

2014-10-01

357

Magnetic isotope and magnetic field effects on the DNA synthesis  

PubMed Central

Magnetic isotope and magnetic field effects on the rate of DNA synthesis catalysed by polymerases ? with isotopic ions 24Mg2+, 25Mg2+ and 26Mg2+ in the catalytic sites were detected. No difference in enzymatic activity was found between polymerases ? carrying 24Mg2+ and 26Mg2+ ions with spinless, non-magnetic nuclei 24Mg and 26Mg. However, 25Mg2+ ions with magnetic nucleus 25Mg were shown to suppress enzymatic activity by two to three times with respect to the enzymatic activity of polymerases ? with 24Mg2+ and 26Mg2+ ions. Such an isotopic dependence directly indicates that in the DNA synthesis magnetic mass-independent isotope effect functions. Similar effect is exhibited by polymerases ? with Zn2+ ions carrying magnetic 67Zn and non-magnetic 64Zn nuclei, respectively. A new, ion–radical mechanism of the DNA synthesis is suggested to explain these effects. Magnetic field dependence of the magnesium-catalysed DNA synthesis is in a perfect agreement with the proposed ion–radical mechanism. It is pointed out that the magnetic isotope and magnetic field effects may be used for medicinal purposes (trans-cranial magnetic treatment of cognitive deceases, cell proliferation, control of the cancer cells, etc). PMID:23851636

Buchachenko, Anatoly L.; Orlov, Alexei P.; Kuznetsov, Dmitry A.; Breslavskaya, Natalia N.

2013-01-01

358

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

E-print Network

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

Fornberg, Bengt

359

The magnetic field of ? Ori A  

NASA Astrophysics Data System (ADS)

Magnetic fields play a significant role in the evolution of massive stars. About 7% of massive stars are found to be magnetic at a level detectable with current instrumentation (Wade et al. 2013) and only a few magnetic O stars are known. Detecting magnetic field in O stars is particularly challenging because they only have few, often broad, lines to measure the field, which leads to a deficit in the knowledge of the basic magnetic properties of O stars. We present new spectropolarimetric Narval observations of ? Ori A. We also provide a new analysis of both the new and older data taking binarity into account. The aim of this study was to confirm the presence of a magnetic field in ? Ori A. We identify that it belongs to ? Ori Aa and characterize it.

Blazère, A.; Neiner, C.; Bouret, J.-C.; Tkachenko, A.

2015-01-01

360

High concentration ferronematics in low magnetic fields  

E-print Network

We investigated experimentally the magneto-optical and dielectric properties of magnetic-nanoparticle-doped nematic liquid crystals (ferronematics). Our studies focus on the effect of the very small orienting bias magnetic field $B_{bias}$, and that of the nematic director pretilt at the boundary surfaces in our systems sensitive to low magnetic fields. Based on the results we assert that $B_{bias}$ is not necessarily required for a detectable response to low magnetic fields, and that the initial pretilt, as well as the aggregation of the nanoparticles play an important (though not yet explored enough) role.

T. Tóth-Katona; P. Salamon; N. Éber; N. Tomašovi?ová; Z. Mitróová; P. Kop?anský

2014-09-05

361

Interplanetary stream magnetism: Kinematic effects. [solar magnetic fields and wind  

NASA Technical Reports Server (NTRS)

The particle density, and the magnetic field intensity and direction are calculated in corotating streams of the solar wind, assuming that the solar wind velocity is constant and radial and that its azimuthal variations are not two rapid. The effects of the radial velocity profile in corotating streams on the magnetic fields were examined using kinematic approximation and a variety of field configurations on the inner boundary. Kinematic and dynamic effects are discussed.

Burlaga, L. F.; Barouch, E.

1974-01-01

362

Fluctuating magnetic field induced resonant activation.  

PubMed

In this paper, we have studied the properties of a Brownian particle at stationary state in the presence of a fluctuating magnetic field. Time dependence of the field makes the system thermodynamically open. As a signature of that the steady state distribution function becomes function of damping strength, intensity of fluctuations and constant parts of the applied magnetic field. It also depends on the correlation time of the fluctuating magnetic field. Our another observation is that the random magnetic field can induce the resonant activation phenomenon. Here correlation time is increased under the fixed variance of the fluctuating field. But if the correlation time (?) increases under the fixed field strength then the mean first passage time rapidly grows at low ? and it almost converges at other limit. This is sharp contrast to the usual colored noise driven open system case where the mean first passage time diverges exponentially. We have also observed that a giant enhancement of barrier crossing rate occurs particularly at large strength of constant parts of the applied magnetic field even for very weak fluctuating magnetic field. Finally, break down of the Arrhenius result and disappearance of the Kramers' turn over phenomenon may occur in the presence of a fluctuating magnetic field. PMID:25494726

Mondal, Shrabani; Das, Sudip; Baura, Alendu; Bag, Bidhan Chandra

2014-12-14

363

Fluctuating magnetic field induced resonant activation  

NASA Astrophysics Data System (ADS)

In this paper, we have studied the properties of a Brownian particle at stationary state in the presence of a fluctuating magnetic field. Time dependence of the field makes the system thermodynamically open. As a signature of that the steady state distribution function becomes function of damping strength, intensity of fluctuations and constant parts of the applied magnetic field. It also depends on the correlation time of the fluctuating magnetic field. Our another observation is that the random magnetic field can induce the resonant activation phenomenon. Here correlation time is increased under the fixed variance of the fluctuating field. But if the correlation time (?) increases under the fixed field strength then the mean first passage time rapidly grows at low ? and it almost converges at other limit. This is sharp contrast to the usual colored noise driven open system case where the mean first passage time diverges exponentially. We have also observed that a giant enhancement of barrier crossing rate occurs particularly at large strength of constant parts of the applied magnetic field even for very weak fluctuating magnetic field. Finally, break down of the Arrhenius result and disappearance of the Kramers' turn over phenomenon may occur in the presence of a fluctuating magnetic field.

Mondal, Shrabani; Das, Sudip; Baura, Alendu; Bag, Bidhan Chandra

2014-12-01

364

Seeding magnetic fields for laser-driven flux compression in high-energy-density plasmas  

SciTech Connect

A compact, self-contained magnetic-seed-field generator (5 to 16 T) is the enabling technology for a novel laser-driven flux-compression scheme in laser-driven targets. A magnetized target is directly irradiated by a kilojoule or megajoule laser to compress the preseeded magnetic field to thousands of teslas. A fast (300 ns), 80 kA current pulse delivered by a portable pulsed-power system is discharged into a low-mass coil that surrounds the laser target. A >15 T target field has been demonstrated using a <100 J capacitor bank, a laser-triggered switch, and a low-impedance (<1 {Omega}) strip line. The device has been integrated into a series of magnetic-flux-compression experiments on the 60 beam, 30 kJ OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. The initial application is a novel magneto-inertial fusion approach [O. V. Gotchev et al., J. Fusion Energy 27, 25 (2008)] to inertial confinement fusion (ICF), where the amplified magnetic field can inhibit thermal conduction losses from the hot spot of a compressed target. This can lead to the ignition of massive shells imploded with low velocity--a way of reaching higher gains than is possible with conventional ICF.

Gotchev, O. V. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Fusion Science Center for Extreme States of Matter and Fast Ignition Physics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627 (United States); Knauer, J. P.; Shoup, M. J. III [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Chang, P. Y. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States); Jang, N. W. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627 (United States); Meyerhofer, D. D.; Betti, R. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Fusion Science Center for Extreme States of Matter and Fast Ignition Physics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627 (United States); Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States)

2009-04-15

365

Seeding magnetic fields for laser-driven flux compression in high-energy-density plasmas.  

PubMed

A compact, self-contained magnetic-seed-field generator (5 to 16 T) is the enabling technology for a novel laser-driven flux-compression scheme in laser-driven targets. A magnetized target is directly irradiated by a kilojoule or megajoule laser to compress the preseeded magnetic field to thousands of teslas. A fast (300 ns), 80 kA current pulse delivered by a portable pulsed-power system is discharged into a low-mass coil that surrounds the laser target. A >15 T target field has been demonstrated using a <100 J capacitor bank, a laser-triggered switch, and a low-impedance (<1 Omega) strip line. The device has been integrated into a series of magnetic-flux-compression experiments on the 60 beam, 30 kJ OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. The initial application is a novel magneto-inertial fusion approach [O. V. Gotchev et al., J. Fusion Energy 27, 25 (2008)] to inertial confinement fusion (ICF), where the amplified magnetic field can inhibit thermal conduction losses from the hot spot of a compressed target. This can lead to the ignition of massive shells imploded with low velocity-a way of reaching higher gains than is possible with conventional ICF. PMID:19405657

Gotchev, O V; Knauer, J P; Chang, P Y; Jang, N W; Shoup, M J; Meyerhofer, D D; Betti, R

2009-04-01

366

Design of a Pellet Injector Diagnostic for Magnetic Field Tilt Measurements in PEGASUS*  

NASA Astrophysics Data System (ADS)

Determination of the current density J(r) and safety factor q(r) profiles in spherical tokamaks will be necessary to understand and optimize the equilibrium and stability properties of the plasma. Motional Stark Effect techniques are problematic in P EGASUS due to the low toroidal magnetic field BT ? 0.1 Tesla. Since ions are constrained to stream along magnetic field lines, the line emission from an injected pellet (e.g. Li^+ at ? = 5485 Åforms a field aligned elongated cigar shape(E.S. Marmar and J.L. Terry, Review Sci. Instrum.normalfont , 61normalfont , 3081 (1990)). This magnetic field tilt information will constrain our magnetic reconstructions that use flux loops, magnetic coils, and soft X-ray emission data. Photo diode position sensitive detectors can determine the angle and position of the cigar shaped emission region with good time resolution (5-10 ? sec). * *Supported by U.S. DoE grant No. DE-FG02-96ER54375

Intrator, T.; Fonck, R.; Lewicki, B.; Nonn, P.; Probert, P.; Sontag, A.; Thorson, T.; Tritz, K.; Wilson, C.; Winz, G.

1998-11-01

367

Consistency evaluation between EGSnrc and Geant4 charged particle transport in an equilibrium magnetic field  

NASA Astrophysics Data System (ADS)

Following the proposal by several groups to integrate magnetic resonance imaging (MRI) with radiation therapy, much attention has been afforded to examining the impact of strong (on the order of a Tesla) transverse magnetic fields on photon dose distributions. The effect of the magnetic field on dose distributions must be considered in order to take full advantage of the benefits of real-time intra-fraction imaging. In this investigation, we compared the handling of particle transport in magnetic fields between two Monte Carlo codes, EGSnrc and Geant4, to analyze various aspects of their electromagnetic transport algorithms; both codes are well-benchmarked for medical physics applications in the absence of magnetic fields. A water-air-water slab phantom and a water-lung-water slab phantom were used to highlight dose perturbations near high- and low-density interfaces. We have implemented a method of calculating the Lorentz force in EGSnrc based on theoretical models in literature, and show very good consistency between the two Monte Carlo codes. This investigation further demonstrates the importance of accurate dosimetry for MRI-guided radiation therapy (MRIgRT), and facilitates the integration of a ViewRay MRIgRT system in the University of Wisconsin-Madison's Radiation Oncology Department.

Yang, Y. M.; Bednarz, B.

2013-02-01

368

Homogenization of nanostructured media in magnetic field  

NASA Astrophysics Data System (ADS)

Problem of homogenization of nanostructured media in magnetic field has been considered. Possibility of introduction of effective material parameters dielectric permittivity and magnetic permeability for three classes of media such as magnetic metal nanostructures, film metal-dielectric composite media and 3D-nanocomposites on the base of opal matrices has been investigated. It has been stated that the introduction of effective parameters far from magnetic resonance conditions is possible at millimeter waveband frequencies. Strict introduction of effective magnetic permeability of nanostructured media near magnetic resonance is not possible.

Rinkevich, A. B.; Perov, D. V.

2014-11-01

369

Two-axis magnetic field sensor  

NASA Technical Reports Server (NTRS)

A ferromagnetic thin-film based magnetic field sensor with first and second sensitive direction sensing structures each having a nonmagnetic intermediate layer with two major surfaces on opposite sides thereof having a magnetization reference layer on one and an anisotropic ferromagnetic material sensing layer on the other having a length in a selected length direction and a smaller width perpendicular thereto and parallel to the relatively fixed magnetization direction. The relatively fixed magnetization direction of said magnetization reference layer in each is oriented in substantially parallel to the substrate but substantially perpendicular to that of the other. An annealing process is used to form the desired magnetization directions.

Jander, Albrecht (Inventor); Nordman, Catherine A. (Inventor); Qian, Zhenghong (Inventor); Smith, Carl H. (Inventor)

2006-01-01

370

Wide-range nuclear magnetic resonance detector  

NASA Technical Reports Server (NTRS)

Compact and easy to use solid state nuclear magnetic resonance detector is designed for measuring field strength to 20 teslas in cryogenically cooled magnets. Extremely low noise and high sensitivity make detector applicable to nearly all types of analytical nuclear magnetic resonance measurements and can be used in high temperature and radiation environments.

Sturman, J. C.; Jirberg, R. J.

1972-01-01

371

Orientation effects in pulsed magnetic field treatment  

Microsoft Academic Search

This paper presents the orientation effects on residual stress release by pulsed magnetic field treatment. Specimens are produced by tungsten inert gas (TIG) welding and the initial residual stresses in them are measured by the hole-drilling method. With different orientations these specimens are treated in the same magnetic field and the residual stresses are measured for the second time. By

Cai Zhipeng; Lin Jian; Zhao Haiyan; Lu Anli

2005-01-01

372

A search for weak stellar magnetic fields  

Microsoft Academic Search

The magnetic fields of normal main sequence stars, supergiants, and mercury-manganese stars were measured in metal lines with the magnetometer of the main stellar spectrograph and in hydrogen lines with the spectropolarimeter at the 6-meter telescope. These data were analyzed statistically with data obtained by other authors. It is concluded that the dipole magnetic fields of the stars studied hardly

Yu. V. Glagolevskij; I. I. Romanyuk; I. D. Najdenov; V. G. Shtol

1991-01-01

373

Magnetic Fields at the Center of Coils  

ERIC Educational Resources Information Center

In this note we synthesize and extend expressions for the magnetic field at the center of very short and very long current-carrying coils. Elementary physics textbooks present the following equation for the magnetic field inside a very long current-carrying coil (solenoid): B[subscript sol] = µ[subscript 0] (N/L) I, (1) where I is the current, N…

Binder, Philippe; Hui, Kaleonui; Goldman, Jesse

2014-01-01

374

Space Quantization in a Gyrating Magnetic Field  

Microsoft Academic Search

The nonadiabatic transitions which a system with angular momentum J makes in a magnetic field which is rotating about an axis inclined with respect to the field are calculated. It is shown that the effects depend on the sign of the magnetic moment of the system. We therefore have an absolute method for measuring the sign and magnitude of the

I. I. Rabi

1937-01-01

375

The magnetic field of an infinite solenoid  

NASA Astrophysics Data System (ADS)

We use the Biot-Savart law for filamentary currents to show that the magnetic field produced by an infinitely long straight strip of infinitesimal width carrying a uniform transverse surface current can be written in simple geometrical terms. We use this result to calculate the magnetic field of an infinite solenoid of arbitrary but uniform cross-sectional shape.

Espinosa, Olivier; Slusarenko, Viktor

2003-09-01

376

Coulomb crystals in the magnetic field.  

PubMed

The body-centered-cubic Coulomb crystal of ions in the presence of a uniform magnetic field is studied using the rigid electron background approximation. The phonon mode spectra are calculated for a wide range of magnetic-field strengths and for several orientations of the field in the crystal. The phonon spectra are used to calculate the phonon contribution to the crystal energy, entropy, specific heat, Debye-Waller factor of ions, and the rms ion displacements from the lattice nodes for a broad range of densities, temperatures, chemical compositions, and magnetic fields. Strong magnetic field dramatically alters the properties of quantum crystals. The phonon specific heat increases by many orders of magnitude. The ion displacements from their equilibrium positions become strongly anisotropic. The results can be relevant for dusty plasmas, ion plasmas in Penning traps, and especially for the crust of magnetars (neutron stars with superstrong magnetic fields B > or approximately equal 10(14) G ). The effect of the magnetic field on ion displacements in a strongly magnetized neutron star crust can suppress the nuclear reaction rates and make them extremely sensitive to the magnetic-field direction. PMID:19905459

Baiko, D A

2009-10-01

377

Does the solar magnetic field increase?  

Microsoft Academic Search

We consider measurements of the general magnetic field (GMF) of the Sun as a star at four world observatories from 1968 until\\u000a 1999. We show that, within the error limits, the mean strength of the photospheric magnetic field H (of its longitudinal component, in magnitude) has not changed over the last 32 years. This is in conflict with the recent

V. A. Kotov; I. V. Kotova

2001-01-01

378

TESLA-Report 2002-07 TESLA-Report 2002-07  

E-print Network

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TESLA-Report 1999-18 TESLA-Report 1999-18  

E-print Network

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TESLA-Report 1993-39 TESLA-Report 1993-39  

E-print Network

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TESLA FEL-Report 1999-04 TESLA FEL-Report 1999-07  

E-print Network

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TESLA-Report 1994-24 TESLA-Report 1994-24  

E-print Network

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TESLA-Report 1996-12 TESLA-Report 1996-12  

E-print Network

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TESLA-Report 1994-11 TESLA-Report 1994-11  

E-print Network

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TESLA-Report 1994-17 TESLA-Report 1994-17  

E-print Network

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TESLA-Report 1994-31 TESLA-Report 1994-31  

E-print Network

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Permanent magnet edge-field quadrupole  

DOEpatents

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

Tatchyn, R.O.

1997-01-21

388

Permanent magnet edge-field quadrupole  

DOEpatents

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

Tatchyn, Roman O. (Mountain View, CA)

1997-01-01

389

Solar magnetic fields and the dynamo theory  

Microsoft Academic Search

Unlike Earth’s dipolar magnetic fields, solar magnetic fields consist of wide ranges of length-scales and strengths, and interestingly, they evolve in a cyclic fashion with a 22-year periodicity. A magnetohydrodynamic dynamo operating in the Sun is most likely responsible for producing the solar magnetic activity cycle. While the first solar dynamo models were built half a century ago, recent views

M. Dikpati

2005-01-01

390

Fields from a relativistic magnetic explosion  

NASA Astrophysics Data System (ADS)

Following Prendergast, we study the relativistically expanding electromagnetic fields generated by an axisymmetric explosion of magnetic energy in a small volume. The magnetic field expands uniformly either within a cone or in all directions and it is therefore accompanied by an electric field. In the highly conducting plasma, the charges move to annul the electric field in the frame of the moving plasma. The solutions presented are analytical and semi-analytical. We find that the time-scale for the winding up of the initial magnetic field is crucial, as short time-scales lead to strong radiant fields. Assuming a magnetic field of 1013G emerging from a magnetosphere of 109cm, we end with a jet when confined by a pressure environment that falls more slowly than r-4. The jet carries energy of 1051erg, which is mostly due to differential rotation at the base.

Gourgouliatos, K. N.; Lynden-Bell, D.

2008-11-01

391

Coaxial Coupling Scheme for TESLA/ILC-type Cavities  

SciTech Connect

This paper reports about our efforts to develop a flangeable coaxial coupler for both HOM and fundamental coupling for 9-cell TESLA/ILC-type cavities. The cavities were designed in early 90‘s for pulsed operation with a low duty factor, less than 1 %. The proposed design of the coupler has been done in a way, that the magnetic flux B at the flange connection is minimized and only a field of <5 mT would be present at the accelerating field Eacc of ~ 36 MV/m (B =150 mT in the cavity). Even though we achieved reasonably high Q-values at low field, the cavity/coupler combination was limited in the cw mode to only ~ 7 MV/m, where a thermally initiated degradation occurred. We have improved the cooling conditions by initially drilling radial channels every 30 degrees, then every 15 degrees into the shorting plate. The modified prototype performed well up to 9 MV/m in cw mode. This paper reports about our experiences with the further modified coaxial coupler and about test results in cw and low duty cycle pulsed mode, similar to the TESLA/ILC operation conditions.

J.K. Sekutowicz, P. Kneisel

2010-05-01

392

Magnetic field amplification in supernova shock precursor  

NASA Astrophysics Data System (ADS)

Galactic cosmic rays are believed to be mostly accelerated at supernova shocks. However, the interstellar magnetic field is too weak to efficiently accelerate galactic cosmic rays up to the highest energies. A stronger magnetic field in the preshock region could provide the efficiency required. Cosmic ray streaming instability has been claimed to be responsible for the amplification of precursor magnetic fields. An alternative mechanism has been proposed in which the cosmic ray pressure gradient forms the shock precursor and drives turbulence, amplifying the magnetic field via the small-scale dynamo. We explore this last scenario through 3-D MHD numerical simulations. We show under which conditions an efficient amplification of the magnetic field is achieved.

Del Valle, Maria Victoria; Lazarian, Alex

393

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. PMID:23712980

Silver, HJ; Niswender, KD; Kullberg, J; Berglund, J; Johansson, L; Bruvold, M; Avison, MJ; Welch, EB.

2012-01-01

394

Chaotic magnetic fields: Particle motion and energization  

SciTech Connect

Magnetic field line equations correspond to a Hamiltonian dynamical system, so the features of a Hamiltonian systems can easily be adopted for discussing some essential features of magnetic field lines. The integrability of the magnetic field line equations are discussed by various authors and it can be shown that these equations are, in general, not integrable. We demonstrate several examples of realistic chaotic magnetic fields, produced by asymmetric current configurations. Particular examples of chaotic force-free field and non force-free fields are shown. We have studied, for the first time, the motion of a charged particle in chaotic magnetic fields. It is found that the motion of a charged particle in a chaotic magnetic field is not necessarily chaotic. We also showed that charged particles moving in a time-dependent chaotic magnetic field are energized. Such energization processes could play a dominant role in particle energization in several astrophysical environments including solar corona, solar flares and cosmic ray propagation in space.

Dasgupta, Brahmananda [CSPAR, University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Ram, Abhay K. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Li, Gang [Department of Physics, University of Alabama in Huntsville, Huntsville, AL 35899 and CSPAR, University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Li, Xiaocan [Department of Physics, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)

2014-02-11

395

Subnanosecond magnetization dynamics induced by a pulsed magnetic field in diluted magnetic semiconductor quantum wells  

NASA Astrophysics Data System (ADS)

The magnetization dynamics induced by a pulsed magnetic field is investigated by time- and polarization-resolved photoluminescene measurements in (Cd,Mn)Te/(Cd,Mg)Te quantum wells. The magnetization dynamics of Mn2+ ions is found to be strongly dependent on the external static magnetic field. A dynamical response of the magnetization on a subnanosecond time scale is observed at zero static magnetic field, while it drastically slows down and approaches the spin-lattice relaxation time constant for a nonzero static field. Theoretical calculations emphasize the importance of local spin interactions that interplay with the Zeeman interaction for the observed magnetization dynamics.

Chen, Y. S.; Wiater, M.; Karczewski, G.; Wojtowicz, T.; Bacher, G.

2013-04-01

396

MRI at 7 tesla and above: Demonstrated and potential capabilities.  

PubMed

With more than 40 installed MR systems worldwide operating at 7 Tesla or higher, ultra-high-field (UHF) imaging has been established as a platform for clinically oriented research in recent years. Along with technical developments that, in part, have also been successfully transferred to lower field strengths, MR imaging and spectroscopy at UHF have demonstrated capabilities and potentials for clinical diagnostics in a variety of studies. In terms of applications, this overview article focuses on already achieved advantages for in vivo imaging, i.e., in imaging the brain and joints of the musculoskeletal system, but also considers developments in body imaging, which is particularly challenging. Furthermore, new applications for clinical diagnostics such as X-nuclei imaging and spectroscopy, which only really become feasible at ultra-high magnetic fields, will be presented. J. Magn. Reson. Imaging 2015;41:13-33. © 2014 Wiley Periodicals, Inc. PMID:24478137

Kraff, Oliver; Fischer, Anja; Nagel, Armin M; Mönninghoff, Christoph; Ladd, Mark E

2015-01-01

397

Magnetization, Low Field Instability and Quench of RHQT Nb(3)Al Strands  

SciTech Connect

Since 2005, we made and tested three RHQT Nb{sub 3}Al 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 eliminated with the Ta matrix strands operating at 4.2 K. But with these strands a similar but smaller anomalous magnetization was observed at 1.9 K. We studied these phenomena with FEM. With the F1 Nb matrix strand, it is explained that at low external field, inter-filamentary coupling currents in the outer layers of sub-elements create a shielding effect. It reduces the inside field, keeps the inside Nb matrix superconductive, and stands against a higher outside field beyond the Hc of Nb. At an even higher external field, the superconductivity of the whole Nb matrix collapses and releases a large amount of energy, which may cause a big quench. Depending on the size of the energy in the strand or the cable, a magnet could quench, causing the low field instability. Some attempt to analyze the anomaly with FEM is presented.

Yamada, R.; Wake, M.; Kikuchi, A.; Velev, V.; /Fermilab

2009-01-01

398

Warm inflation in presence of magnetic fields  

SciTech Connect

We present preliminary results on the possible effects that primordial magnetic fields can have for a warm inflation scenario, based on global supersymmetry, with a new-inflation-type potential. This work is motivated by two considerations: first, magnetic fields seem to be present in the universe on all scales which rises de possibility that they could also permeate the early universe; second, the recent emergence of inflationary models where the inflaton is not assumed to be isolated but instead it is taken as an interacting field, even during the inflationary expansion. The effects of magnetic fields are included resorting to Schwinger's proper time method.

Piccinelli, Gabriella [Centro Tecnológico, FES Aragón, Universidad Nacional Autónoma de México, Avenida Rancho Seco S/N, Bosques de Aragón, Nezahualcóyotl, Estado de México 57130 (Mexico)] [Centro Tecnológico, FES Aragón, Universidad Nacional Autónoma de México, Avenida Rancho Seco S/N, Bosques de Aragón, Nezahualcóyotl, Estado de México 57130 (Mexico); Sánchez, Ángel [Department of Physics, University of Texas at El Paso, El Paso, Texas 79968 (United States)] [Department of Physics, University of Texas at El Paso, El Paso, Texas 79968 (United States); Ayala, Alejandro; Mizher, Ana Julia [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70-543, México Distrito Federal 04510 (Mexico)] [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70-543, México Distrito Federal 04510 (Mexico)

2013-07-23

399

In Vivo T1? Quantitative Assessment of Knee Cartilage After Anterior Cruciate Ligament Injury Using 3 Tesla Magnetic Resonance Imaging  

PubMed Central

Objective The aims of this study were to evaluate the spatial distribution of cartilage structure in controls and patients, and to quantitatively assess the cartilage overlying bone marrow edema-like lesion (BMEL) and within defined cartilage compartments in knees with anterior cruciate ligament (ACL) tears using T1? mapping technique at 3 T magnetic resonance imaging. Materials and Methods The knee joints of 15 healthy controls (4 women, 11 men, mean age = 30.1 year) and 16 patients with ACL tear (5 women, 11 men, mean age = 32.5 years) who showed BMEL was studied using a 3 T GEMR scanner and a quadrature knee coil. The imaging protocol included sequences for cartilage morphology and 3D quantitative T1? mapping. Lateral femoral condyle and medial femoral condyles compartments were partitioned into anterior and posterior nonweight-bearing (ant-nwb and postnwb) portions and weight-bearing (wb) portions in all subjects. In patients only, cartilage overlying BMEL and surrounding cartilage portions were also defined. T1? values were quantified in cartilage overlying BMEL and surrounding compartments and in each defined compartment of the ACL-injured knees, and compared with controls. Results Significantly elevated T1? values were found in the femoral nonweight-bearing (nwb) portions when compared with weight-bearing (wb) portions both in patients and controls. Significantly increased T1? values were found in cartilage overlying BMEL when compared with surrounding cartilage at the lateral tibia (LT), but no difference was found in the lateral femoral condyle. Conclusion T1? mapping technique provides tools to quantitatively evaluate the cartilage matrix overlying BMEL in patients with ACL injuries. Cartilage abnormalities are already present following initial ACL injuries over the lateral tibia. Quantitative MRI can allow critical evaluation of medical and surgical treatments for ligament and degenerative conditions of the knee. PMID:18923257

Bolbos, Radu I.; Ma, C. Benjamin; Link, Thomas M.; Majumdar, Sharmila; Li, Xiaojuan

2010-01-01

400

The role of 3-tesla diffusion-weighted magnetic resonance imaging in selecting prostate cancer patients for active surveillance  

PubMed Central

Purpose Differentiating significant cancer from insignificant cancer is a major challenge in active surveillance (AS) for prostate cancer. We evaluated whether the apparent diffusion coefficient (ADC) grade from 3-T diffusion-weighted magnetic resonance imaging (DW-MRI) is useful to exclude men with unfavorable pathological features from men meeting current AS eligibility criteria. Methods Among patients who underwent radical prostatectomy, 117 potential AS candidates defined according to 2013 European Association of Urology guidelines who had undergone preoperative 3-T DW-MRI were included. A blinded uro-radiologist graded the level of suspicion from the ADC map using the Likert scale from 1 to 5. The rate of unfavorable pathological features was evaluated according to ADC grade. Unfavorable pathological features were defined as non–organ-confined disease or pathological Gleason score?7 (4+3). The associations between unfavorable pathological features and clinical variables including ADC grade (>3 vs. ?3) were evaluated using logistic regression analysis. Results The rates of unfavorable pathological features were 0.0% (0/14), 2.9% (1/34), 5.4% (2/37), 25.0% (6/24), and 37.5% (3/8) from grades 1 to 5 (P=0.002). The predictive accuracy was as high as 0.804. The rates were significantly different between low (?3, 3.5%) and high (>3, 28.1%, P<0.001) grades. The sensitivity, specificity, and positive and negative predictive values were 75.0%, 78.1%, 28.1%, and 96.5%. ADC grade (odds ratio [OR], 10.696; 95% confidence interval [CI], 2.675–42.773) was significantly associated with unfavorable pathological features, even after adjusting for other variables (OR, 11.274; 95% CI, 2.622–48.471). Conclusions ADC grade from 3-T DW-MRI is useful to predict men with unfavorable pathologic features from AS candidates. PMID:25599072

Jeong, Chang Wook; Park, Yong Hyun; Hwang, Sung II; Lee, Sangchul; Jeong, Seong Jin; Hong, Sung Kyu; Byun, Seok-Soo; Lee, Hak Jong; Lee, Sang Eun

2014-01-01

401

Magnetization and magnetic susceptibility of DyH3  

NASA Technical Reports Server (NTRS)

The magnetization and differential magnetic susceptibility of powdered samples of DyH3 have been measured at 4.2 K in applied magnetic fields ranging to 9 Teslas. The differential magnetic susceptibility has also been studied in zero applied field as a function of temperature. The magnetization data are described by an equation of the form M = aB/(1 + bB + cB. The ratio a/b is a measure of the saturation magnetization and gives an effective moment of 5.12 Bohr magnetons per ion. The zero field susceptibility exhibits a maximum at T = 3.45 K, and an inflection point near 2.85 K. The susceptibility at 4.2 K has a 1/B squared dependence on the applied magnetic field for B approximately greater than 0.3 Teslas.

Flood, D. J.

1974-01-01

402

Photon collider at TESLA  

E-print Network

High energy photon colliders (gamma-gamma, gamma-electron) based on backward Compton scattering of laser light is a very natural addition to e+e- linear colliders. In this report we consider this option for the TESLA project. Recent study has shown that the horizontal emittance in the TESLA damping ring can be further decreased by a factor of four. In this case the gamma-gamma luminosity luminosity in the high energy part of spectrum can reach (1/3)L_{e+e-}. Typical cross sections of interesting processes in gamma-gamma collisions are higher than those in e+e- collisions by about one order of magnitude, so the number of events in gamma-gamma collisions will be more than that in e+e- collisions. Photon colliders can, certainly, give additional information and they are the best for the study of many phenomena. The main question is now the technical feasibility. The key new element in photon colliders is a very powerful laser system. An external optical cavity is a promising approach for the TESLA project. A free electron laser is another option. However, a more straightforward solution is ``an optical storage ring (optical trap)'' with diode pumped solid state laser injector which is today technically feasible. This paper briefly reviews the status of a photon collider based at TESLA, its possible parameters and existing problems.

Valery Telnov

2001-03-06

403

Magnetic field-induced phase transformation in NiMnCoIn magnetic shape memory alloys - a new actuation mechanism with large work output.  

SciTech Connect

Magnetic shape memory alloys (MSMAs) have recently been developed into a new class of functional materials that are capable of magnetic-field-induced actuation, mechanical sensing, magnetic refrigeration, and energy harvesting. In the present work, the magnetic field-induced martensitic phase transformation (FIPT) in Ni{sub 45}Mn{sub 36.5}Co{sub 5}In{sub 13.5} MSMA single crystals is characterized as a new actuation mechanism with potential to result in ultra-high actuation work outputs. The effects of the applied magnetic field on the transformation temperatures, magnetization, and superelastic response are investigated. The magnetic work output of NiMnCoIn alloys is determined to be more than 1 MJ m{sup -3} per Tesla, which is one order of magnitude higher than that of the most well-known MSMAs, i.e., NiMnGa alloys. In addition, the work output of NiMnCoIn alloys is orientation independent, potentially surpassing the need for single crystals, and not limited by a saturation magnetic field, as opposed to NiMnGa MSMAs. Experimental and theoretical transformation strains and magnetostress levels are determined as a function of crystal orientation. It is found that [111]-oriented crystals can demonstrate a magnetostress level of 140 MPa T{sup -1} with 1.2% axial strain under compression. These field-induced stress and strain levels are significantly higher than those from existing piezoelectric and magnetostrictive actuators. A thermodynamical framework is introduced to comprehend the magnetic energy contributions during FIPT. The present work reveals that the magnetic FIPT mechanism is promising for magnetic actuation applications and provides new opportunities for applications requiring high actuation work-outputs with relatively large actuation frequencies. One potential issue is the requirement for relatively high critical magnetic fields and field intervals (1.5-3 T) for the onset of FIPT and for reversible FIPT, respectively.

Karaca, H. E.; Karaman, I.; Basaran, B.; Ren, Y.; Chumlyakov, Y. I.; Maier, H. J.; X-Ray Science Division; Texsas A& M Univ.; Univ. of Kentucky; Siberian Physical-Technical Inst.; Univ. of Paderborn

2009-04-09

404

Evolution of Magnetic Fields in Supernova Remnants  

E-print Network

Supernova remnants (SNR) are now widely believed to be a source of cosmic rays (CRs) up to an energy of 1 PeV. The magnetic fields required to accelerate CRs to sufficiently high energies need to be much higher than can result from compression of the circumstellar medium (CSM) by a factor 4, as is the case in strong shocks. Non-thermal synchrotron maps of these regions indicate that indeed the magnetic field is much stronger, and for young SNRs has a dominant radial component while for old SNRs it is mainly toroidal. How these magnetic fields get enhanced, or why the field orientation is mainly radial for young remnants, is not yet fully understood. We use an adaptive mesh refinement MHD code, AMRVAC, to simulate the evolution of supernova remnants and to see if we can reproduce a mainly radial magnetic field in early stages of evolution. We follow the evolution of the SNR with three different configurations of the initial magnetic field in the CSM: an initially mainly toroidal field, a turbulent magnetic field, and a field parallel to the symmetry axis. Although for the latter two topologies a significant radial field component arises at the contact discontinuity due to the Rayleigh-Taylor instability, no radial component can be seen out to the forward shock. Ideal MHD appears not sufficient to explain observations. Possibly a higher compression ratio and additional turbulence due to dominant presence of CRs can help us to better reproduce the observations in future studies.

K. M. Schure; J. Vink; A. Achterberg; R. Keppens

2008-10-28

405

Field Mapping System for Solenoid Magnet  

NASA Astrophysics Data System (ADS)

A three-dimensional Hall probe mapping system for measuring the solenoid magnet of PLS photo-cathode RF e-gun has been developed. It can map the solenoid field either in Cartesian or in cylindrical coordinate system with a measurement reproducibility better than 5 × 10-5 T. The system has three axis motors: one for the azimuthal direction and the other two for the x and z direction. This architecture makes the measuring system simple in fabrication. The magnetic center was calculated using the measured axial component of magnetic field Bz in Cartesian coordinate system because the accuracy of magnetic axis measurement could be improved significantly by using Bz, instead of the radial component of magnetic field Br. This paper describes the measurement system and summarizes the measurement results for the solenoid magnetic of PLS photo-cathode RF e-gun.

Park, K. H.; Jung, Y. K.; Kim, D. E.; Lee, H. G.; Park, S. J.; Chung, C. W.; Kang, B. K.

2007-01-01

406

Magnetic fields in noninvasive brain stimulation.  

PubMed

The idea that magnetic fields could be used therapeutically arose 2000 years ago. These therapeutic possibilities were expanded after the discovery of electromagnetic induction by the Englishman Michael Faraday and the American Joseph Henry. In 1896, Arsène d'Arsonval reported his experience with noninvasive brain magnetic stimulation to the scientific French community. In the second half of the 20th century, changing magnetic fields emerged as a noninvasive tool to study the nervous system and to modulate neural function. In 1985, Barker, Jalinous, and Freeston presented transcranial magnetic stimulation, a relatively focal and painless technique. Transcranial magnetic stimulation has been proposed as a clinical neurophysiology tool and as a potential adjuvant treatment for psychiatric and neurologic conditions. This article aims to contextualize the progress of use of magnetic fields in the history of neuroscience and medical sciences, until 1985. PMID:23787954

Vidal-Dourado, Marcos; Conforto, Adriana Bastos; Caboclo, Luis Otávio Sales Ferreira; Scaff, Milberto; Guilhoto, Laura Maria de Figueiredo Ferreira; Yacubian, Elza Márcia Targas

2014-04-01

407

Origin of magnetic fields in galaxies  

SciTech Connect

Microgauss magnetic fields are observed in all galaxies at low and high redshifts. The origin of these intense magnetic fields is a challenging question in astrophysics. We show here that the natural plasma fluctuations in the primordial Universe (assumed to be random), predicted by the fluctuation -dissipation theorem, predicts {approx}0.034 {mu}G fields over {approx}0.3 kpc regions in galaxies. If the dipole magnetic fields predicted by the fluctuation-dissipation theorem are not completely random, microgauss fields over regions > or approx. 0.34 kpc are easily obtained. The model is thus a strong candidate for resolving the problem of the origin of magnetic fields in < or approx. 10{sup 9} years in high redshift galaxies.

Souza, Rafael S. de; Opher, Reuven [IAG, Universidade de Sao Paulo, Rua do Matao 1226, Cidade Universitaria, CEP 05508-900, Sao Paulo, SP (Brazil)

2010-03-15

408

Probing Primordial Magnetic Fields Using Ly? Clouds  

NASA Astrophysics Data System (ADS)

From previous studies of the effect of primordial magnetic fields on early structure formation, we know that the presence of primordial magnetic fields during early structure formation could induce more perturbations at small scales (at present 1-10 h -1 Mpc) as compared to the usual ?CDM theory. Matter power spectra over these scales are effectively probed by cosmological observables such as shear correlation and Ly? clouds. In this paper we discuss the implications of primordial magnetic fields on the distribution of Ly? clouds. We simulate the line-of-sight density fluctuation including the contribution coming from the primordial magnetic fields. We compute the evolution of Ly? opacity for this case and compare our theoretical estimates of Ly? opacity with the existing data to constrain the parameters of the primordial magnetic fields. We also discuss the case when the two density fields are correlated. Our analysis yields an upper bound of roughly 0.3-0.6 nG on the magnetic field strength for a range of nearly scale-invariant models, corresponding to a magnetic field power spectrum index n ~= -3.

Pandey, Kanhaiya L.; Sethi, Shiv K.

2013-01-01

409

Magnetic-field-controlled reconfigurable semiconductor logic.  

PubMed

Logic devices based on magnetism show promise for increasing computational efficiency while decreasing consumed power. They offer zero quiescent power and yet combine novel functions such as programmable logic operation and non-volatile built-in memory. However, practical efforts to adapt a magnetic device to logic suffer from a low signal-to-noise ratio and other performance attributes that are not adequate for logic gates. Rather than exploiting magnetoresistive effects that result from spin-dependent transport of carriers, we have approached the development of a magnetic logic device in a different way: we use the phenomenon of large magnetoresistance found in non-magnetic semiconductors in high electric fields. Here we report a device showing a strong diode characteristic that is highly sensitive to both the sign and the magnitude of an external magnetic field, offering a reversible change between two different characteristic states by the application of a magnetic field. This feature results from magnetic control of carrier generation and recombination in an InSb p-n bilayer channel. Simple circuits combining such elementary devices are fabricated and tested, and Boolean logic functions including AND, OR, NAND and NOR are performed. They are programmed dynamically by external electric or magnetic signals, demonstrating magnetic-field-controlled semiconductor reconfigurable logic at room temperature. This magnetic technology permits a new kind of spintronic device, characterized as a current switch rather than a voltage switch, and provides a simple and compact platform for non-volatile reconfigurable logic devices. PMID:23364687

Joo, Sungjung; Kim, Taeyueb; Shin, Sang Hoon; Lim, Ju Young; Hong, Jinki; Song, Jin Dong; Chang, Joonyeon; Lee, Hyun-Woo; Rhie, Kungwon; Han, Suk Hee; Shin, Kyung-Ho; Johnson, Mark

2013-02-01

410

Assessment of global myocardial perfusion reserve using cardiovascular magnetic resonance of coronary sinus flow at 3 Tesla  

PubMed Central

Background Despite increasing clinical use, there is limited data regarding regadenoson in stress perfusion cardiovascular magnetic resonance (CMR). In particular, given its long half-life the optimal stress protocol remains unclear. Although Myocardial Perfusion Reserve (MPR) may provide additive prognostic information, current techniques for its measurement are cumbersome and challenging for routine clinical practice. The aims of this study were: 1) To determine the feasibility of MPR quantification during regadenoson stress CMR by measurement of Coronary Sinus (CS) flow; and 2) to investigate the role of aminophylline reversal during regadenoson stress-CMR. Methods 117 consecutive patients with possible myocardial ischemia were prospectively enrolled. Perfusion imaging was performed at 1 minute and 15 minutes after administration of 0.4 mg regadenoson. A subgroup of 41 patients was given aminophylline (100 mg) after stress images were acquired. CS flow was measured using phase-contrast imaging at baseline (pre CS flow), and immediately after the stress (peak CS flow) and rest (post CS flow) perfusion images. Results CS flow measurements were obtained in 92% of patients with no adverse events. MPR was significantly underestimated when calculated as peak CS flow/post CS flow as compared to peak CS flow/pre CS flow (2.43?±?0.20 vs. 3.28?±?0.32, p?=?0.03). This difference was abolished when aminophylline was administered (3.35?±?0.44 vs. 3.30?±?0.52, p?=?0.95). Impaired MPR (peak CS flow/pre CS flow <2) was associated with advanced age, diabetes, current smoking and higher Framingham risk score. Conclusions Regadenoson stress CMR with MPR measurement from CS flow can be successfully performed in most patients. This measurement of MPR appears practical to perform in the clinical setting. Residual hyperemia is still present even 15 minutes after regadenoson administration, at the time of resting-perfusion acquisition, and is completely reversed by aminophylline. Our findings suggest routine aminophylline administration may be required when performing stress CMR with regadenoson. PMID:24674383

2014-01-01

411

External-field-free magnetic biosensor  

SciTech Connect

In this paper, we report a magnetic nanoparticle (MNP) detection scheme without the presence of any external magnetic field. The proposed magnetic sensor uses a patterned groove structure within the sensor so that no external magnetic field is needed to magnetize the MNPs. An example is given based on a giant magnetoresistance (GMR) sensing device with a spin valve structure. For this structure, the detection of MNPs located inside the groove and near the free layer is demonstrated under no external magnetic field. Micromagnetic simulations are performed to calculate the signal to noise level of this detection scheme. A maximum signal to noise ratio (SNR) of 18.6?dB from one iron oxide magnetic nanoparticle with 8?nm radius is achieved. As proof of concept, this external-field-free GMR sensor with groove structure of 200?nm?×?200?nm is fabricated using a photo and an electron beam integrated lithography process. Using this sensor, the feasibility demonstration of the detection SNR of 9.3?dB is achieved for 30??l magnetic nanoparticles suspension (30?nm iron oxide particles, 1?mg/ml). This proposed external-field-free sensor structure is not limited to GMR devices and could be applicable to other magnetic biosensing devices.

Li, Yuanpeng; Wang, Yi; Klein, Todd; Wang, Jian-Ping, E-mail: jpwang@umn.edu [Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

2014-03-24

412

External-field-free magnetic biosensor  

NASA Astrophysics Data System (ADS)

In this paper, we report a magnetic nanoparticle (MNP) detection scheme without the presence of any external magnetic field. The proposed magnetic sensor uses a patterned groove structure within the sensor so that no external magnetic field is needed to magnetize the MNPs. An example is given based on a giant magnetoresistance (GMR) sensing device with a spin valve structure. For this structure, the detection of MNPs located inside the groove and near the free layer is demonstrated under no external magnetic field. Micromagnetic simulations are performed to calculate the signal to noise level of this detection scheme. A maximum signal to noise ratio (SNR) of 18.6 dB from one iron oxide magnetic nanoparticle with 8 nm radius is achieved. As proof of concept, this external-field-free GMR sensor with groove structure of 200 nm × 200 nm is fabricated using a photo and an electron beam integrated lithography process. Using this sensor, the feasibility demonstration of the detection SNR of 9.3 dB is achieved for 30 ?l magnetic nanoparticles suspension (30 nm iron oxide particles, 1 mg/ml). This proposed external-field-free sensor structure is not limited to GMR devices and could be applicable to other magnetic biosensing devices.

Li, Yuanpeng; Wang, Yi; Klein, Todd; Wang, Jian-Ping

2014-03-01

413

"Non-Contact Ultrasonic Treatment of Metals in a Magnetic Field"  

SciTech Connect

A concept has been originated for non-contact ultrasonic treatment of metals based on the use of an induction coil located in a high-field superconducting magnet. An advantage of using a high magnetic field environment (> 9 T) is that this allows the induced surface current in the sample to be decreased proportionately. As a result, the incidental induction heating associated with the use of the EMAT (Electromagnetic Acoustical Transducer) is greatly reduced, which improves the energy efficiency of the EMAT approach. The method can be coupled with high-field magnetic processing, but can also be used where only ultrasonic treatment is beneficial. In the proof-of-principle experiments, a high-field EMAT was used for non-contact ultrasonic processing of aluminum samples during solidification. The magnetic field for the EMAT was supplied by a high-field (20 Tesla) resistive magnet, and the current was provided by an induction coil. This resulted in a highly efficient EMAT that delivered 0.5 MPa (~5 atmospheres) of acoustic drive to the surface of the sample while coupling less than 100 watts of incidental induction heating. The exceptionally high energy efficiency of the electromagnetic transducer is due to the use of the high magnetic field, which reduces the current needed to achieve the same acoustic pressure. In these initial experiments, aluminum samples of A356 alloy were heated to the liquid state and allowed to solidify at a controlled cooling rate while subjected to the non-contact ultrasonic stimulation (0.5 MPa @ 165 kHz) provided by an induction coil located within the 200 mm (~8-inch) bore of a 20-T Bitter resistive magnet.

Ludtka, Gerard Michael [ORNL; Wilgen, John B [ORNL; Kisner, Roger A [ORNL; Jaramillo, Roger A [ORNL; Ludtka, Gail Mackiewicz- [ORNL

2007-01-01

414

Compact low field magnetic resonance imaging magnet: Design and optimization  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) is performed with a very large instrument that allows the patient to be inserted into a region of uniform magnetic field. The field is generated either by an electromagnet (resistive or superconductive) or by a permanent magnet. Electromagnets are designed as air cored solenoids of cylindrical symmetry, with an inner bore of 80-100 cm in diameter. In clinical analysis of peripheral regions of the body (legs, arms, foot, knee, etc.) it would be better to adopt much less expensive magnets leaving the most expensive instruments to applications that require the insertion of the patient in the magnet (head, thorax, abdomen, etc.). These "dedicated" apparati could be smaller and based on resistive magnets that are manufactured and operated at very low cost, particularly if they utilize an iron yoke to reduce power requirements. In order to obtain good field uniformity without the use of a set of shimming coils, we propose both particular construction of a dedicated magnet, using four independently controlled pairs of coils, and an optimization-based strategy for computing, a posteriori, the optimal current values. The optimization phase could be viewed as a low-cost shimming procedure for obtaining the desired magnetic field configuration. Some experimental measurements, confirming the effectiveness of the proposed approach (construction and optimization), have also been reported. In particular, it has been shown that the adoption of the proposed optimization based strategy has allowed the achievement of good uniformity of the magnetic field in about one fourth of the magnet length and about one half of its bore. On the basis of the good experimental results, the dedicated magnet can be used for MRI of peripheral regions of the body and for animal experimentation at very low cost.

Sciandrone, M.; Placidi, G.; Testa, L.; Sotgiu, A.

2000-03-01

415

Magnetic field corrections to solar oscillation frequencies  

NASA Technical Reports Server (NTRS)

It is argued that the frequencies of both the solar p- and g-modes of oscillation are modified by a magnetic field. In particular, the decrease in p-mode frequencies is attributed to a magnetic field within the solar interior evolving over the solar cycle. Field strengths at the base of the convection zone of at least 500,000 G are required.

Roberts, B.; Campbell, W. R.

1986-01-01

416

Vector Magnetic Field in Emerging Flux Regions  

NASA Astrophysics Data System (ADS)

A crucial phase in magnetic flux emergence is the rise of magnetic flux tubes through the solar photosphere, which represents a severe transition between the very different environments of the solar interior and corona. Multi-wavelength observations with Flare Genesis, TRACE, SoHO, and more recently with the vector magnetographs at THEMIS and Hida (DST) led to the following conclusions. The fragmented magnetic field in the emergence region - with dipped field lines or bald patches - is directly related with Ellerman bombs, arch filament systems, and overlying coronal loops. Measurements of vector magnetic fields have given evidence that undulating "serpentine" fields are present while magnetic flux tubes cross the photosphere. See the sketch below, and for more detail see Pariat et al. (2004, 2007); Watanabe et al. (2008):

Schmieder, B.; Pariat, E.

417

Advanced magnetic calculations for high magnetic field compact ion source  

NASA Astrophysics Data System (ADS)

The design of the advanced electronic cyclotronic resonance ion source (ECRIS) requires relatively high axial and radial magnetic inductions to allow the ECR frequency increase and to take advantage of the subsequent density increase (scaling laws). The last improvements of the commercial rare-earth magnet characteristics open new opportunities for ECRIS and enable the design of very high hexapolar magnetic fields for next generation compact ECRIS. Moreover, the high temperature superconducting (HTS) wires allow designing reliable and compact axial field coils (30 K cooled) at a very effective cost. It is thus very relevant to study a compact hybrid ECRIS using high remanence magnet and HTS technologies. In such a design, the volume of the plasma chamber is a free parameter that can be adjusted to the user requirement. It can be dedicated to very high ionic current production or high charge state production, pulsed, or cw operations. This paper presents the three-dimensional overall simulation of a 3 T axial magnetic field compact ECRIS with a high radial field sextupole composed with several magnet types and reaching ˜1.9 T in front of the radially magnetized magnets. This design study will lead to the building of the 28-40 GHz A-PHOENIX source at the laboratory which will deliver its first beam by the end of 2004.

Thuillier, T.; Curdy, J.-C.; Lamy, T.; Sole, P.; Sortais, P.; Vieux-Rochaz, J.-L.; Voulot, D.

2004-05-01

418

Magnetic reconnection at the edge of Uranus's magnetic field  

NASA Astrophysics Data System (ADS)

A new modeling study sheds light on how the magnetosphere of Uranus compares to those of other planets. Magnetospheres around the inner planets Mercury and Earth are primarily driven by the solar wind—the charged particles spewed out from the Sun—through magnetic reconnection, in which the planet's magnetic field lines break and reconnect, releasing energy in the process.

Balcerak, Ernie

2014-09-01

419

Anisotropy of magnetic susceptibility measured in variable weak magnetic fields  

NASA Astrophysics Data System (ADS)

Theory of the low-field anisotropy of magnetic susceptibility (AMS) of rocks is based on the assumption of the linear relationship between magnetization and magnetizing field, resulting in field independent susceptibility. This relationship is by definition valid in diamagnetic and paramagnetic minerals, while in ferrimagnetic and antiferromagnetic minerals this relationship is in general non-linear (represented by hysteresis loop), being linear only in very weak fields in which the initial susceptibility is measured. Among these minerals, magnetite shows no field variation of susceptibility and its anisotropy in the low fields used in common AMS meters. In pyrrhotite, hematite and titanomagnetite bearing rocks, in which these minerals are very fine-grained, the field variation of susceptibility is insignificant. Using linear theory in calculating the AMS is fully legitimate in all these cases. In pyrrhotite, hematite, and titanomagnetite bearing rocks, in which these minerals are relatively coarse-grained (typically hundreds of micrometers), clear field variation of magnetic susceptibility may exist even in the low fields used in common AMS meters, often resulting in bad fit of the susceptibility tensor to the measured data. Strictly speaking, linear theory in calculating the AMS is in general incorrect in this case. The KLY-3S Kappabridge has been modified in such a way to enable AMS measurement also in the fields down to 3 A/m. Examples are shown of the effect of this field decrease on the measured data.

Pokorny, J.; Suza, P.; Hrouda, F.

2003-04-01

420

Particle Transport in Therapeutic Magnetic Fields  

NASA Astrophysics Data System (ADS)

Iron oxide magnetic nanoparticles, in ferrofluids or as magnetic microspheres, offer magnetic maneuverability, biochemical surface functionalization, and magnetic relaxation under the influence of an alternating field. The use of these properties for clinical applications requires an understanding of particles, forces, and scalar transport at various length scales. This review explains the behavior of magnetic nano- and microparticles during magnetic drug targeting and magnetic fluid hyperthermia, and the microfluidic transport of these particles in bioMEMS (biomedical microelectromechanical systems) devices for ex vivo therapeutic and diagnostic applications. Magnetic particle transport, the momentum interaction of these particles with a host fluid in a flow, and thermal transport in a particle-infused tissue are characterized through the governing electrodynamic, hydrodynamic, and scalar transport equations.

Puri, Ishwar K.; Ganguly, Ranjan

2014-01-01

421

The Measurement of Magnetic Fields  

ERIC Educational Resources Information Center

Discusses five experimental methods used by senior high school students to provide an accurate calibration curve of magnet current against the magnetic flux density produced by an electromagnet. Compares the relative merits of the five methods, both as measurements and from an educational viewpoint. (JR)

Berridge, H. J. J.

1973-01-01

422

Faraday's Magnetic Field Induction Experiment  

NSDL National Science Digital Library

This java simulation illustrates magnetic induction in a wire coil. The user can move a magnet in and out along the axis of a coil while a galvanometer shows the current induced in the coil. The deflection depends on the speed at which the coil moves.

Davidson, Michael

2010-12-29

423

The CMS Magnetic Field Map Performance  

E-print Network

The Compact Muon Solenoid (CMS) is a general-purpose detector designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive featuresinclude a 4 T superconducting solenoid with 6 m diameter by 12.5 m long free bore, enclosed inside a 10000-ton return yoke made of construction steel. Accurate characterization of the magnetic field everywhere in the CMS detector is required. During two major tests of the CMS magnet the magnetic flux density was measured inside the coil in a cylinder of 3.448 m diameter and 7 m length with a specially designed field-mapping pneumatic machine as well as in 140 discrete regions of the CMS yoke with NMR probes, 3-D Hall sensors and flux-loops. A TOSCA 3-D model of the CMS magnet has been developed to describe the magnetic field everywhere outside the tracking volume measured with the field-mapping machine. A volume based representation of the magnetic field is used to provide the CMS simulation and reconstruction software with the magnetic field values. The value of the field at a given point of a volume is obtained by interpolation from a regular grid of values resulting from a TOSCA calculation or, when available, from a parameterization. The results of the measurements and calculations are presented, compared and discussed.

V. I. Klyukhin; N. Amapane; V. Andreev; A. Ball; B. Curé; A. Hervé; A. Gaddi; H. Gerwig; V. Karimaki; R. Loveless; M. Mulders; S. Popescu; L. I. Sarycheva; T. Virdee

2011-10-04

424

Characterization of rf-SSET in both in-plane and perpendicular magnetic fields  

NASA Astrophysics Data System (ADS)

Previous success in coupling an aluminum radio-frequency superconducting single electron transistor (rf-SSET) to quantum dots (QDs) has demonstrated use of the rf-SSET as an ultra-sensitive and fast charge sensor [1]. Since a magnetic field is usually necessary for quantum dot qubit manipulation, it is important to understand the effect of magnetic fields, either in-plane or perpendicular, on the performance of any charge sensor near the QDs. Here we report characterization of rf-SSETs in both in-plane and perpendicular magnetic fields. The rf-SSET works well in an in-plane fields up to 1 Tesla at a temperature of 30 mK. At 0.3K, in a perpendicular field generated by a stripline located 700 nm away, the rf-SSET charge sensitivity even shows improvement for up to 2.1 mA current through the stripline (corresponding roughly to a field of 6 Gauss). [1]M. Yuan et al, Appl. Phys. Lett. 101, 142103 (2012)

Tang, Chunyang; Yang, Zhen; Yuan, Mingyun; Rimberg, A. J.; Savage, D. E.; Eriksson, M. A.

2013-03-01

425

Generation of high magnetic fields using superconducting magnets  

Microsoft Academic Search

High-field superconducting magnets have opened new frontiers for several kinds of applications, such as fusion reactors, particle accelerators, and nuclear magnetic resonance (NMR) spectrometers. The present record for the highest field in a fully superconducting state is 23.4T. It was achieved with a combination of NbTi, Nb3Sn, and Bi-2212 conductors in 1999. Since high Tc (critical temperature) superconductors (HTS) have

T. Kiyoshi; A. Otsuka; M. Kosuge; M. Yuyama; H. Nagai; F. Matsumoto

2006-01-01

426

Magnetic Field Measurement with Ground State Alignment  

NASA Astrophysics Data System (ADS)

Observational studies of magnetic fields are crucial. We introduce a process "ground state alignment" as a new way to determine the magnetic field direction in diffuse medium. The alignment is due to anisotropic radiation impinging on the atom/ion. The consequence of the process is the polarization of spectral lines resulting from scattering and absorption from aligned atomic/ionic species with fine or hyperfine structure. The magnetic field induces precession and realign the atom/ion and therefore the polarization of the emitted or absorbed radiation reflects the direction of the magnetic field. The atoms get aligned at their low levels and, as the life-time of the atoms/ions we deal with is long, the alignment induced by anisotropic radiation is susceptible to extremely weak magnetic fields (1 G ? B ? 10^{-15} G). In fact, the effects of atomic/ionic alignment were studied in the laboratory decades ago, mostly in relation to the maser research. Recently, the atomic effect has been already detected in observations from circumstellar medium and this is a harbinger of future extensive magnetic field studies. A unique feature of the atomic realignment is that they can reveal the 3D orientation of magnetic field. In this chapter, we shall review the basic physical processes involved in atomic realignment. We shall also discuss its applications to interplanetary, circumstellar and interstellar magnetic fields. In addition, our research reveals that the polarization of the radiation arising from the transitions between fine and hyperfine states of the ground level can provide a unique diagnostics of magnetic fields in the Epoch of Reionization.

Yan, Huirong; Lazarian, A.

427

NON-CONTACT ULTRASONIC TREATMENT OF METALS IN A MAGNETIC FIELD  

SciTech Connect

A high-field EMAT (Electromagnetic Acoustical Transducer) has been used for non-contact ultrasonic processing of aluminum samples during solidification. The magnetic field for the EMAT is supplied by a high-field (20 Tesla) resistive magnet, and the current is provided by an induction coil. This resulted in a highly efficient EMAT that delivered 0.5 MPa of acoustic drive to the surface of the sample while coupling less than 100 watts of incidental induction heating. The exceptionally high energy efficiency of the electromagnetic transducer is due to the use of high magnetic field, which reduces the current needed to achieve the same acoustic pressure. In the initial experiments, aluminum samples of A356 alloy were heated to the liquid state and allowed to solidify at a controlled cooling rate while subjected to the non-contact ultrasonic stimulation (0.5 MPa @ 165 kHz) provided by an induction coil located within the bore of a 20-T resistive magnet

Wilgen, John B [ORNL] [ORNL; Kisner, Roger A [ORNL] [ORNL; Jaramillo, Roger A [ORNL] [ORNL; Ludtka, Gerard Michael [ORNL] [ORNL; Ludtka, Gail Mackiewicz- [ORNL] [ORNL

2007-01-01

428

Strain-Induced Pseudo--Magnetic Fields in Graphene: MegaGauss in Nanobubbles  

NASA Astrophysics Data System (ADS)

Recent theoretical proposals suggest that strain can be used to modify 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). Scanning tunneling microscopy shows that graphene grown on a platinum (111) surface forms nanobubbles, which are highly strained due to thermal expansion mismatch between the film and the substrate. We find that scanning tunneling spectroscopy measurements of these nanobubbles exhibit Landau levels that form in the presence of strain-induced pseudo--magnetic fields greater than 300 Tesla. This demonstration of enormous pseudo--magnetic fields opens the door to both the study of charge carriers in previously inaccessible high magnetic field regimes and deliberate mechanical control over electronic structure in graphene or so-called "strain engineering". [4pt] In collaboration with S. A. Burke^,2, K. L. Meaker^2, M. Panlasigui^2, A. Zettl^2,3, F. Guinea^4, A. H. Castro Neto^5 and M. F. Crommie^2,3. . Present address: Department of Physics and Astronomy and Department of Chemistry, University of British Columbia, Vancouver, BC V6T 121, Canada. 2. Department of Physics, University of California, Berkeley, CA 94720, USA. 3. Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. 4. Instituto de Ciencia de Materiales de Madrid (CSIC), Madrid 28049, Spain. 5. Department of Physics, Boston University, Boston, MA 02215, USA.

Levy, Niv

2011-03-01

429

Magnetic Fields from Heterotic Cosmic Strings  

E-print Network

Large-scale magnetic fields are observed today to be coherent on galactic scales. While there exists an explanation for their amplification and their specific configuration in spiral galaxies -- the dynamo mechanism -- a satisfying explanation for the original seed fields required is still lacking. Cosmic strings are compelling candidates because of their scaling properties, which would guarantee the coherence on cosmological scales of any resultant magnetic fields at the time of galaxy formation. We present a mechanism for the production of primordial seed magnetic fields from heterotic cosmic strings arising from M theory. More specifically, we make use of heterotic cosmic strings stemming from M5--branes wrapped around four of the compact internal dimensions. These objects are stable on cosmological time scales and carry charged zero modes. Therefore a scaling solution of such defects will generate seed magnetic fields which are coherent on galactic scales today.

Gwyn, Rhiannon; Brandenberger, Robert H; Dasgupta, Keshav

2008-01-01

430

Magnetic fields from heterotic cosmic strings  

SciTech Connect

Large-scale magnetic fields are observed today to be coherent on galactic scales. While there exists an explanation for their amplification and their specific configuration in spiral galaxies--the dynamo mechanism--a satisfying explanation for the original seed fields required is still lacking. Cosmic strings are compelling candidates because of their scaling properties, which would guarantee the coherence on cosmological scales of any resultant magnetic fields at the time of galaxy formation. We present a mechanism for the production of primordial seed magnetic fields from heterotic cosmic strings arising from M theory. More specifically, we make use of heterotic cosmic strings stemming from M5-branes wrapped around four of the compact internal dimensions. These objects are stable on cosmological time scales and carry charged zero modes. Therefore a scaling solution of such defects will generate seed magnetic fields which are coherent on galactic scales today.

Gwyn, Rhiannon; Alexander, Stephon H.; Brandenberger, Robert H.; Dasgupta, Keshav [Department of Physics, McGill University, Montreal, Quebec, H3A 2T8 (Canada); Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802-6300 (United States); Department of Physics and Astronomy, Koshland Center for Integrated Sciences, Haverford College, Haverford, Pennsylvania 19041 (United States); Department of Physics, McGill University, Montreal, Quebec, H3A 2T8 (Canada)

2009-04-15

431

The magnetic field of Mercury, part 1  

NASA Technical Reports Server (NTRS)

An updated analysis and interpretation is presented of the magnetic field observations obtained during the Mariner 10 encounter with the planet Mercury. The combination of data relating to position of the detached bow shock wave and magnetopause, and the geometry and magnitude of the magnetic field within the magnetosphere-like region surrounding Mercury, lead to the conclusion that an internal planetary field exists with dipole moment approximately 5.1 x 10 the 22nd power Gauss sq cm. The dipole axis has a polarity sense similar to earth's and is tilted 7 deg from the normal to Mercury's orbital plane. The magnetic field observations reveal a significant distortion of the modest Hermean field (350 Gamma at the equator) by the solar wind flow and the formation of a magnetic tail and neutral sheet which begins close to the planet on the night side. The composite data is not consistent with a complex induction process driven by the solar wind flow.

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

1974-01-01

432

Magnetic field induced optical vortex beam rotation  

E-print Network

Light with orbital angular momentum (OAM) has drawn a great deal of attention for its important applications in the fields of precise optical measurements and high capacity optical communications. Here we adopt a method to study the rotation of a light beam, which is based on magnetic field induced circular birefringence in warm 87Rb atomic vapor. The dependence of the rotation angle to the intensity of the magnetic field makes it appropriate for weak magnetic field measurement. We derive a detail theoretical description that is in well agreement with the experimental observations. The experiment shows here provides a new method for precise measurement of magnetic field intensity and expands the application of OAM-carrying light.

Shi, Shuai; Zhou, Zhi-Yuan; Li, Yan; Zhang, Wei; Shi, Bao-Sen

2015-01-01

433

The Third Flight Magnet  

NASA Technical Reports Server (NTRS)

A self-shielded superconducting magnet was designed for the NASA Goddard Space Flight Center Adiabatic Demagnetization Refrigerator Program. This is the third magnet built from this design. The magnets utilize Cryomagnetics' patented ultra-low current technology. The magnetic system is capable of reaching a central field of two tesla at slightly under two amperes and has a total inductance of 1068 henries. This final report details the requirements of the magnet, the specifications of the resulting magnet, the test procedures and test result data for the third magnet (Serial # C-654-M), and recommended precautions for use of the magnet.

McGhee, R. Wayne

1998-01-01

434

QCD string breaking in strong magnetic field  

NASA Astrophysics Data System (ADS)

At sufficiently large separation between a quark and an antiquark the quantum chromodynamics (QCD) string breaks into parts due to creation of light quark-antiquark pairs. We show that a background magnetic field affects the breaking of the QCD string oriented in the transverse directions with respect to the axis of the magnetic field. Using semiclassical approach we argue that above certain, the background magnetic field eB ?0.3 GeV2 breaking of the transverse string should become energetically unfavorable.

Chernodub, M. N.

2014-09-01

435

Magnetic fields from second-order interactions  

E-print Network

It is well known that when two types of perturbations interact in cosmological perturbation theory, the interaction may lead to the generation of a third type. In this article we discuss the generation of magnetic fields from such interactions. We determine conditions under which the interaction of a first-order magnetic field with a first-order scalar-or vector-, or tensor-perturbations would lead to the generation of second order magnetic field. The analysis is done in a covariant-index-free approach, but could be done in the standard covariant indexed-approach.

Bob Osano

2014-03-21

436

Small-scale solar magnetic fields  

E-print Network

As we resolve ever smaller structures in the solar atmosphere, it has become clear that magnetism is an important component of those small structures. Small-scale magnetism holds the key to many poorly understood facets of solar magnetism on all scales, such as the existence of a local dynamo, chromospheric heating, and flux emergence, to name a few. Here, we review our knowledge of small-scale photospheric fields, with particular emphasis on quiet-sun field, and discuss the implications of several results obtained recently using new instruments, as well as future prospects in this field of research.

A. G. de Wijn; J. O. Stenflo; S. K. Solanki; S. Tsuneta

2008-12-24

437

The magnetic field of solar prominences  

E-print Network

In his famous monographs, Einar Tandberg-Hanssen writes that "the single, physically most important parameter to study in prominences may be the magnetic field. Shapes, motions, and in fact the very existence of prominences depend on the nature of the magnetic field threading the prominence plasma". Hereafter we sumarize recent contributions and advances in our knowledge about the magnetic field of solar prominences. It mostly relies on high resolution and high sensitivity spectropolarimetry made both in the visible and in the near infrared.

F. Paletou

2008-10-15

438

Environmental magnetic fields: Influences on early embryogenesis  

SciTech Connect

A 10-mG, 50 to 60-Hz magnetic field is in the intensity and frequency range that people worldwide are often exposed to in homes and in the workplace. Studies about the effects of 50- to 100-Hz electromagnetic fields on various species of animal embryos (fish, chick, fly, sea urchin, rat, and mouse) indicate that early stages of embryonic development are responsive to fluctuating magnetic fields. Chick, sea urchin, and mouse embryos are responsive to magnetic field intensities of 10-100 mG. Results from studies on sea urchin embryos indicate that exposure to conditions of rotating 60-Hz magnetic fields, e.g., similar to those in our environment, interferes with cell proliferation at the morula stage in a manner dependent on field intensity. The cleavage stages, prior to the 64-cell stage, were not delayed by this rotating 60-Hz magnetic field suggesting that the ionic surges, DNA replication, and translational events essential for early cleavage stages were not significantly altered. Studies of histone synthesis in early sea urchin embryos indicated that the rotating 60-Hz magnetic field decreased zygotic expression of early histone genes at the morula stage and suggests that this decrease in early histone production was limiting to cell proliferation. Whether these comparative observations from animal development studies will be paralleled by results from studies of human embryogenesis, as suggested by some epidemiology studies, has yet to be established. 38 refs.

Cameron, I.L.; Hardman, W.E.; Winters, W.D.; Zimmerman, S.; Zimmerman, A.M. (Univ. of Texas Health Science Center, San Antonio (United States))

1993-04-01

439

Magnetic fields of the terrestrial planets  

NASA Technical Reports Server (NTRS)

The four terrestrial planets, together with the Earth's Moon, provide a significant range of conditions under which dynamo action could occur. All five bodies have been visited by spacecraft, and from three of the five bodies (Earth, Moon and Mars) we have samples of planetary material upon which paleomagnetic studies have been undertaken. At the present time, only the Earth and Mercury appear to have a significant dipole magnetic field. However, the Moon, and possibly Mars, appear to have had ancient planetary dynamos. Venus does not now have a significant planetary magnetic field, and the high surface temperatures should have prevented the recording of evidence of any ancient magnetic field. Since the solidification of the solid inner core is thought to be the energy source for the terrestrial magnetic field, and since smaller bodies evolve thermally more rapidly than larger bodies, we conjecture that the terrestrial planets are today in three different phases of magnetic activity. Venus is in a predynamo phase, not having cooled to the point of core solidification. Mercury and the Earth are in the middle of their dynamo phase, with Mercury perhaps near the end of its activity. Mars and the Moon seem to be well past their dynamo phase. Much needs to be don