scholarly journals Radiatively induced magnetic moment in four-dimensional anisotropic quantum electrodynamics in an external magnetic field

2002 ◽  
Vol 65 (21) ◽  
Author(s):  
Jean Alexandre ◽  
Nick E. Mavromatos
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetic Moment ◽  
Quantum Electrodynamics

scholarly journals Stokesian dynamics simulations of a magnetotactic bacterium

2021 ◽  
Vol 44 (3) ◽  
Author(s):  
Sarah Mohammadinejad ◽  
Damien Faivre ◽  
Stefan Klumpp
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Cell Body ◽  
Magnetic Moment ◽  
Magnetotactic Bacteria ◽  
Swimming Velocity ◽  
Stokesian Dynamics ◽  
Inclination Angles ◽  
Dynamics Simulations ◽  
The Magnetic Field

AbstractThe swimming of bacteria provides insight into propulsion and steering under the conditions of low-Reynolds number hydrodynamics. Here we address the magnetically steered swimming of magnetotactic bacteria. We use Stokesian dynamics simulations to study the swimming of single-flagellated magnetotactic bacteria (MTB) in an external magnetic field. Our model MTB consists of a spherical cell body equipped with a magnetic dipole moment and a helical flagellum rotated by a rotary motor. The elasticity of the flagellum as well as magnetic and hydrodynamic interactions is taken into account in this model. We characterized how the swimming velocity is dependent on parameters of the model. We then studied the U-turn motion after a field reversal and found two regimes for weak and strong fields and, correspondingly, two characteristic time scales. In the two regimes, the U-turn time is dominated by the turning of the cell body and its magnetic moment or the turning of the flagellum, respectively. In the regime for weak fields, where turning is dominated by the magnetic relaxation, the U-turn time is approximately in agreement with a theoretical model based on torque balance. In the strong-field regime, strong deformations of the flagellum are observed. We further simulated the swimming of a bacterium with a magnetic moment that is inclined relative to the flagellar axis. This scenario leads to intriguing double helical trajectories that we characterize as functions of the magnetic moment inclination and the magnetic field. For small inclination angles ($$\lesssim {20^{\circ }}$$≲20∘) and typical field strengths, the inclination of the magnetic moment has only a minor effect on the swimming of MTB in an external magnetic field. Large inclination angles result in a strong reduction in the velocity in direction of the magnetic field, consistent with recent observations that bacteria with large inclination angles use a different propulsion mechanism.Graphic abstract

scholarly journals The Electrodynamics of Neutrinos in Dispersive Media

1990 ◽  
Vol 142 ◽  
pp. 35-38
Author(s):  
V.N. Oraevsky ◽  
V.B. Semikoz
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Charge Distribution ◽  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
Dispersive Media ◽  
Mean Square ◽  
Vector Bosons ◽  
Electromagnetic Characteristics ◽  
The Mean

Neutrinos interacting with the vacuum of vector bosons and leptons possess important vacuum electromagnetic characteristics: viz., the anomalous magnetic moment Δμvacν and the mean-square radius of charge distribution <r2>1/2. As a result, neutrinos, just like neutrons, may interact with an external magnetic field.

Fractal Aggregation of Magnetic Particles

1990 ◽  
Vol 206 ◽  
Author(s):  
J. P. Bucher ◽  
N. D. Rizzo ◽  
J. G. Louderback ◽  
L. A. Bloomfield
Keyword(s):  
Magnetic Field ◽  
Fractal Dimension ◽  
External Magnetic Field ◽  
Experimental Model ◽  
Magnetic Moment ◽  
Magnetic Particles ◽  
Magnetic Moments ◽  
Ferromagnetic Particles

ABSTRACTWe present an experimental model where magnetic balls in a box are used to simulate aggregation of small ferromagnetic particles a few nm in diameter. The aggregation can be characterized by a fractal dimension that increases as the magnetic moment of the particles decreases. The magnetization of the system of balls has been measured in an external magnetic field and compared for different values of the magnetic moments.

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