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Magnetic Dipole (magnetic + dipole)
Selected AbstractsElectromagnetic fields in a steel-cased boreholeGEOPHYSICAL PROSPECTING, Issue 1 2005Ki Ha Lee ABSTRACT The development of an electromagnetic numerical modelling scheme for a magnetic dipole in an arbitrary casing segment in an inhomogeneous conductivity background has been difficult, due to the very high electrical conductivity and magnetic permeability contrasts between the steel casing and the background medium. To investigate the effect of steel casing efficiently, we have developed an accurate but simple finite-element modelling scheme to simulate electromagnetic fields in a medium of cylindrically symmetric conductivity structures. In order to preserve the cylindrical symmetry in the resulting electromagnetic fields, a horizontal loop current source is used throughout. One of the main advantages of the approach is that the problem is scalar when formulated using the azimuthal electric field, even if the casing is both electrically conductive and magnetically permeable. Field calculations have been made inside the cased borehole as well as in another borehole which is not cased. Careful analyses of the numerical modelling results indicate that the anomaly observed in a cross-borehole configuration is sensitive enough to be used for tomographic imaging. [source] Chiral discrimination via nuclear magnetic shielding polarisabilities from NMR spectroscopy: Theoretical study of (Ra)-1,3-dimethylallene, (2R)-2-methyloxirane, and (2R)- N -methyloxaziridineJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2007R. Zanasi Abstract Three medium-size optically active molecules have been studied to make a guess at candidates suitable for chiral discrimination in an isotropic medium via nuclear magnetic resonance spectroscopy. The criterion for experimental detection is given by the magnitude of the isotropic part of nuclear magnetic shielding polarisability tensors, related to a pseudoscalar of opposite sign for the two enantiomers. The pseudoscalar shielding polarisability at the 17O nucleus in N -methyloxaziridine, calculated at the Hartree-Fock level, is ,7.8 ×10,17 mV,1. To obtain an experimentally observable magnetic field induced at the 17O nucleus in N -methyloxaziridine, electric fields as large as ,107,108 Vm,1 should be applied to the probe. The molecular electric dipole moment induced by precession of the magnetic dipole of the 17O nucleus in a magnetic field of 10 T is, in absolute value, ,8.8 × 10,42 Cm. The estimated rf-voltage at a resonance circuit is ,10 nV. Smaller values have been estimated for N, C, and H nuclei in 1,3-dimethylallene and 2-methyloxirane. © 2007 Wiley Periodicals, Inc. J Comput Chem 2007 [source] Effects of Parasite Attributes and Injected Current Parameters on Electromagnetic Detection of Parasites in Fish MuscleJOURNAL OF FOOD SCIENCE, Issue 9 2002G.S. Choudhury ABSTRACT: We examined the potential of an electromagnetic parasite detection technique to become the basis of an automated commercial system. The effects of parasite orientation and position, presence offish bone, and applied signal strength and frequency on resultant magnetic field strength were determined by scanning a conducting cell containing fish fillet and parasite below a SQUID magnetometer. The parasite orientation affected peak-to-peak voltage of the magnetic dipole. The parasite position with respect to myotome structure seemed to affect the orientation of the dipolar signal. A fish bone was readily detected. The magnetic field strength was independent of the frequency of the injected current and scaled with amplitude=. [source] Noninvasive Study of Ventricular Preexcitation Using Multichannel MagnetocardiographyPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1p2 2003RICCARDO FENICI FENICI, R., et al.: Noninvasive Study of Ventricular Preexcitation Using Multichannel Magnetocardiography. In clinical practice, noninvasive classification of ventricular preexcitation (VPX) is usually done with ECG algorithms, which provide only a qualitative localization of accessory pathways. Since 1984, single or multichannel magnetocardiograpy (MMCG) has been used for three-dimensional localization of VPX sites, but a systematic study comparing the results of ECG and MMCG methods was lacking. This study evaluated the reliability of MMCG in an unshielded electrophysiological catheterization laboratory, and compared VPX classification as achieved with the five most recent ECG algorithms with that obtained by MMCG mapping and imaging techniques. A nine-channel direct current superconducting quantum interference device (DC-SQUID) MMCG system (sensitivity is 20 fT/Hz0.5) was used for sequential MMCG from 36 points on the anterior chest wall, within an area20 × 20 cm. Twenty-eight patients with Wolff-Parkinson-White syndrome were examined at least twice, on the same day or after several months to test the reproducibility of the measurements. In eight patients, the reproducibility of MMCG was also evaluated using different MCG instrumentation during maximal VPX and/or atrioventricular reentrant tachycardia induced by transesophageal atrial pacing via a nonmagnetic catheter. The results of VPX localization with ECG algorithms and MMCG were compared. Equivalent current dipole, effective magnetic dipole, and distributed currents imaging models were used for the inverse solution. MMCG classification of VPX was found to be more accurate than ECG methods, and also provided additional information for the identification of paraseptal pathways. Furthermore, in patients with complex activation patterns during the delta wave, distributed currents imaging revealed two different activation patterns, suggesting the existence of multiple accessory pathways. (PACE 2003; 26[Pt. II]:431,435) [source] Scalar Aharonov-Bohm effect in the presence of a topological defectANNALEN DER PHYSIK, Issue 7 2010K. Bakke Abstract In this paper we study the scalar Aharonov-Bohm effect for a neutral particle possessing a magnetic dipole moment in the presence of a cosmic string. We study the phase shift acquired by the wave function of the neutral particle in the presence of this topological defect, investigate this phase shift within nonrelativistic and relativistic quantum descriptions considering two distinct magnetic field configurations and find that the scalar Aharonov-Bohm effect is composed by two contributions, with the first one arises due to the interaction of a magnetic dipole with an external field, and other one arises due to the presence of the cosmic string. The nondispersivity of this effect is also discussed. [source] Combination of electric and magnetic dipoles with single-element feeding for broadband applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2006Karlo Q. da Costa Abstract This work presents four types of broadband compound antennas. The antennas are a combination of an electric dipole and small square or circular loops. The feeding of the electric dipole only is realized. The input impedance, reflection coefficient, and gain of the antennas with different geometries are analyzed numerically using the method of moments (MoM). It is shown that for the level of the reflection coefficient |,| < ,10 dB, 80% to 90% bandwidth can theoretically be achieved for the proposed antennas. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 8,12, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21248 [source] | ||||||||||