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Showing results for: magnetic field

Exact solutions for a Dirac electron in an exponentially decaying magnetic field.

Research RF Safe Research Library Jan 1, 2009

This theoretical paper analyzes a Dirac electron in an exponentially decaying magnetic field. It reports exact energy eigenvalues including a zero-energy state and provides corresponding eigenfunctions. The authors also calculate probability density and current distributions.

Nonuniqueness of magnetic fields and energy derivatives in spin-polarized density functional theory.

Research RF Safe Research Library Jan 1, 2009

This theoretical paper analyzes consequences of nonuniqueness of the external magnetic field B(r) in spin-polarized density functional theory. It reports that for ground states the energy functional is not differentiable with respect to spin density, but one-sided derivatives can exist. The work links these one-sided…

Spatial and Temporal Variations of a Screening Current Induced Magnetic Field in a Double-Pancake HTS Insert of an LTS/HTS NMR Magnet.

Research RF Safe Research Library Jan 1, 2009

This engineering study measures and simulates screening current induced magnetic fields (SCF) in a Bi2223-tape HTS insert used in an LTS/HTS NMR magnet at 77 K. SCF was induced by the insert self-field, an external 5-T background magnet, and their combination, and axial field distributions and temporal variations…

Ising spin-glass transition in a magnetic field outside the limit of validity of mean-field theory.

Research RF Safe Research Library Jan 1, 2009

This paper studies the spin-glass transition in a magnetic field using a diluted one-dimensional long-range Ising model with distance-dependent bond probability. The authors report evidence for a spin-glass transition in a magnetic field both within and beyond the mean-field regime. They also report such evidence for…

Extraordinary magnetic field enhancement with metallic nanowire: role of surface impedance in Babinet's principle for sub-skin-depth regime.

Research RF Safe Research Library Jan 1, 2009

This paper proposes metallic nanowires as complementary structures to metallic nanogaps for enhancing magnetic fields. It reports magnetic field enhancement up to a factor of 300 and presents a surface-impedance-based analytic theory that is numerically confirmed. The authors also report that, in the sub-skin-depth…

Magnetic field delocalization and flux inversion in fractional vortices in two-component superconductors.

Research RF Safe Research Library Jan 1, 2009

This theoretical paper analyzes vortex solutions in two-component superconductors within a U(1) x U(1) Ginzburg-Landau framework. It reports that exponentially screened magnetic fields are only found in special cases, while most parameter choices yield delocalized magnetic fields with slowly decaying tails. It also…

Quasiparticles of spatially anisotropic triangular antiferromagnets in a magnetic field.

Research RF Safe Research Library Jan 1, 2009

This theoretical/physics study investigates spectral properties of a spin-1/2 Heisenberg antiferromagnet on an anisotropic triangular lattice in a magnetic field. It reports that interchain interactions in a magnetic field generate dominant modes that behave as quasiparticles, featuring anomalous incommensurate…

Focused-ion-beam-assisted magnet fabrication and manipulation for magnetic field detection applications.

Research RF Safe Research Library Jan 1, 2009

This engineering study describes a focused-ion-beam-assisted technique for fabricating reduced-size NdFeB nanomagnets and integrating them onto a thin-film bulk acoustic resonator (FBAR). After bonding the magnet, the FBAR showed a downshift in resonance frequency and a reduced quality factor. The magnetic behavior…

Theory for nanoparticle retention time in the helical channel of quadrupole magnetic field-flow fractionation.

Research RF Safe Research Library Jan 1, 2009

This paper presents a theoretical treatment of nanoparticle retention in quadrupole magnetic field-flow fractionation (QMgFFF) using a helical separation channel. It defines the retention ratio as the ratio of transit times for non-retained versus retained material. Equations are derived for angular and longitudinal…

Sham Transcranial Magnetic Stimulation Using Electrical Stimulation of the Scalp.

Research RF Safe Research Library Jan 1, 2009

This study describes development and validation of a sham rTMS approach that combines a matched sham coil (for look/sound) with scalp electrical stimulation (for sensation). In back-to-back comparisons, TMS-naïve participants reportedly could not tell active from sham, whereas experienced participants could. The…

Evaluation of the efficacy of pulsed electromagnetic field in the management of patients with diabetic polyneuropathy.

Research RF Safe Research Library Jan 1, 2009

This randomized controlled trial evaluated low-power, low-frequency pulsed electromagnetic field (PEMF) therapy at 600 Hz and 800 Hz as an adjunct treatment for diabetic polyneuropathy. Thirty participants were randomized to 600 Hz PEMF, 800 Hz PEMF, or usual medical treatment for 12 days. The abstract reports…

The influence of low-frequency magnetic field on plasma antioxidant capacity and heart rate.

Research RF Safe Research Library Jan 1, 2009

This animal study exposed Sprague-Dawley rats to a 40 Hz, 7 mT time-variable magnetic field and measured ECG heart rate and plasma antioxidant capacity before and after exposure, including after 14 days. The authors report a significant decrease in heart rate after 14 days. Antioxidant defence findings were mixed,…

[Effects of 50 Hz sinusoidal magnetic field on Ca2+ release channel ryanodine receptor of sarcoplasmic reticulum vesicles].

Research RF Safe Research Library Jan 1, 2009

This in vitro study examined whether a 50 Hz sinusoidal magnetic field affects the sarcoplasmic reticulum calcium release channel RyR1. A 0.4 mT exposure for 30 minutes increased SR Ca2+ release rate and [(3)H]-ryanodine binding under NADH/NAD+ conditions. The authors also report increased NADH oxidation and…

[Female genital toxicities of high-frequency electromagnetic field on rats].

Research RF Safe Research Library Jan 1, 2009

This rat study examined sub-chronic exposure to a 30 MHz electromagnetic field at 0–1600 V/m for 8 hours/day, 5 days/week, over 56 days. The authors report no change in ovarian wet weight, but dose-related changes in estrous cycle timing, reproductive hormones (higher LH and lower E2 at higher exposures), and ovarian…

[A preliminary study on role of acid sphingomyelinase in receptor clustering induced by 50-Hz magnetic fields].

Research RF Safe Research Library Jan 1, 2009

This in vitro study exposed human amnion (FL) cells to a 50-Hz sinusoidal magnetic field (0.4 mT) for 15 minutes and assessed epidermal growth factor receptor (EGFR) clustering. The authors report that magnetic field exposure induced EGFR clustering, and that this effect was blocked by imipramine, an acid…

[Conclusion: probable and possible futures. MRI with ultra high magnetic field].

Research RF Safe Research Library Jan 1, 2009

This narrative piece states that MR neuroimaging does not interfere with brain function and is safe for use in patients and healthy volunteers. It argues that ultra-high-field MRI could substantially improve spatiotemporal resolution, potentially enabling study of brain function at finer scales. It also describes the…

Static magnetic field therapy: a critical review of treatment parameters.

Research RF Safe Research Library Jan 1, 2009

This critical review summarizes human research on static magnetic field (SMF) therapy delivered by permanent magnets attached to the skin and evaluates how well studies report SMF dosage and treatment parameters. Across 56 included studies, many did not report essential SMF characteristics (e.g., magnet dimensions,…

Biological effects from electromagnetic field exposure and public exposure standards

Research RF Safe Research Library Jan 1, 2008

This review describes public concerns and scientific reports of non-thermal biological effects from low-intensity ELF and RF exposures. It lists multiple health endpoints reported to be associated with ELF and/or RF and highlights the BioInitiative Report’s conclusion that a reasonable suspicion of risk exists at…

Apparent violation of the Wiedemann-Franz law near a magnetic field tuned metal-antiferromagnetic quantum critical point.

Research RF Safe Research Library Jan 1, 2008

This paper reports calculations of interlayer electrical and thermal resistivity in a layered metal assuming Fermi-liquid quasiparticles inelastically scattered by two-dimensional antiferromagnetic spin fluctuations. The model yields linear-in-temperature behavior over a broad range and suggests that extrapolations…

[Effect of 1.8 GHz radiofrequency electromagnetic fields on gene expression of rat neurons].

Research RF Safe Research Library Jan 1, 2008

This in vitro study exposed primary cultured rat neurons to 1.8 GHz RF-EMF at an average SAR of 2 W/kg and assessed gene expression changes. The authors report multiple differentially expressed genes after 24 h intermittent exposure and confirm exposure-dependent changes in Egr-1, Mbp, and Plp by semi-quantitative…

Numerical methods for computing the ground state of spin-1 Bose-Einstein condensates in a uniform magnetic field.

Research RF Safe Research Library Jan 1, 2008

This paper presents numerical methods to compute ground-state solutions of spin-1 Bose-Einstein condensates in a uniform magnetic field. The approach uses normalized gradient flow with an additional normalization condition and enforces conservation of total mass and magnetization. The authors compare numerical…

Aggregation of magnetic holes in a rotating magnetic field.

Research RF Safe Research Library Jan 1, 2008

This laboratory study experimentally examined aggregation of nonmagnetic particles in a magnetic fluid layer under a rotating magnetic field. Particles formed two-dimensional clusters that repeatedly aggregated into larger clusters, producing a broad distribution of cluster sizes. The dynamics were described as…

Electronic response properties of carbon nanotubes in magnetic fields.

Research RF Safe Research Library Jan 1, 2008

This computational study investigates magnetic linear response properties of achiral and chiral carbon nanotubes using first-principles electronic structure methods. It computes magnetic shielding inside and outside nanotubes due to electronic currents induced by external magnetic fields applied parallel or…

Improvement in magnetic field immunity of externally-coupled transcutaneous energy transmission system for a totally implantable artificial heart.

Research RF Safe Research Library Jan 1, 2008

This engineering study addresses interference between induction-heating cookers and an externally coupled transcutaneous energy transmission system for a totally implantable artificial heart. The authors report that magnetic flux from an IH cooker can couple into the TET transformer and affect system performance. A…

In vivo quantification of contrast agent concentration using the induced magnetic field for time-resolved arterial input function measurement with MRI.

Research RF Safe Research Library Jan 1, 2008

This Medical Physics article presents a phase-based MRI method to quantify paramagnetic contrast agent concentration by inverting susceptibility-induced magnetic field shifts, aiming to improve arterial input function (AIF) measurement in DCE-MRI. After in vitro validation, the approach was applied in vivo in 14…

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