Nobuko I. Wakayama

Effect of a magnetic field gradient on the crystallization of hen lysozyme

The effect of microgravity on protein crystal growth is an interesting, but highly controversial, issue. We superimposed the magnetic force on gravity and studied its effect on the crystal growth of hen egg-white lysozyme. The magnetic force was used similarly to the centrifugal force in a space shuttle to virtually change the level of gravity. We observed that the number of crystals increased or decreased, respectively, when 5% of the additional force was applied in the same or in the opposite direction to normal gravity. Our result indicates that the magnitude of gravity can in fact affect the studied protein crystal growth, and that a magnetic force has the potential ability of controlling gravity.

Magnetic orientation as a tool to study the initial stage of crystallization of lysozyme

Abstract The tetragonal crystals of hen egg-white lysozyme align their c -axis in the direction of a magnetic field. By applying the magnetic field of 1.6 T only over some period during the whole crystallization process, it was possible to know when the crystals sedimented. It was found that crystals grew in solution, and started to sediment on reaching a critical size. We evaluated the critical size to be 1–2 μm by changing the magnetic field strength (0.1–1.2 T) and analyzing the relation between the field strength and the proportion of magnetic orientation.

Quantitative Analysis of Air Convection Caused by Magnetic -Fluid Coupling

Magnetic attractive forces acting on paramagnetic oxygen have recently been found to induce gas e ow and promote combustion. The study of the interaction between electrically nonconducting gases and magnetic e elds is a new interdisciplinary research area called “ magnetoaerodynamics.” The authors present the magnetic body force acting on the gas and the governing equations for magnetoaerodynamics. The authors used these equations to evaluate the N 2‐air jet numerically to understand the mechanism and physics of this phenomenon. The key results are as follows: 1 ) The magnetic body force becomes nonconservative under gradients of both the O 2 gas concentration and themagneticstrength. 2 )Thenumerical analysesclarifythemechanism of thecoupling between magnetic forces and the convective motion and indicate the existence of air convection and the N 2 jet due to the nonconservative magnetic body force. 3 ) The maximum velocity of the N 2 jet, umax, increases with the magnetic strength at the center of the magnet, B0. For B0 =1:5 T and entrance velocity of the N 2 gas of 7.4 cm/s, umax =44 cm/s. 4) Measured velocities were in good agreement with our simulation. This study suggests the potential use of magnetic e elds to control gas e ows and combustion.

Magnetic suppression of convection in protein crystal growth processes

Magnetization force caused by a magnetic field gradient (F m ) is a body force and can cause buoyancy. We numerically simulate the natural convection arising from the depletion of protein concentration around a growing protein crystal when an upward magnetization force acts on the solution. The numerical predictions reveal that an upward magnetization force can damp convection. When a magnetic field gradient μ 2 0 H(dH/dz) = -685 T 2 /m is applied, the maximum flow velocity is reduced by about 50% and the velocity in the vicinity of the crystal is reduced by about 24%. Due to the low electric conductivity of the solution, the contribution of the Lorentz force is negligible. When μ 2 0 H(dH/dz) = -1370 T 2 /m, the upward magnetization force (F m ρg) damps convection completely. Our study shows a new method of controlling convection in the process of protein crystal formation.

Magnetic Acceleration of Inhaled and Exhaled Flows in Breathing

Time dependence of the velocity of inhalation and exhalation in breathing was measured in the presence and absence of a magnetic field. When a U-shaped permanent magnet of central magnetic strength 0.7 T was set around the location of air intake, the average velocity of inhaled and exhaled flows increased by about 23%. When a permanent magnet was brought in contact with the nose and a magnetic field was applied inside a nostril, the average velocity increased by about 18%. Magnetic acceleration was efficient when air flowed into a narrower space in the direction of increasing magnetic field strength. The present study suggests a novel method which assists breathing.

Effects of a magnetic field and magnetization force on protein crystal growth. Why does a magnet improve the quality of some crystals

Probable reasons why some protein crystals grown in a magnet exhibited better quality than control are discussed as follows. (1). Sedimenting three-dimensional nuclei are able to have the same orientation as the underlying, mother crystal into which the nuclei merge. (2). Protein solution may become more viscous, leading to reduction of convection. (3). If an upward force is generated by use of an inhomogeneous magnetic field, the effects of the density differences can be made less significant, causing the reduction of natural convection and the retardation of crystal sedimentation.

The effect of magnetic field on the oxygen reduction reaction and its application in polymer electrolyte fuel cells

Abstract The effect of magnetic field gradients on the electrochemical oxygen reduction was studied with relevance to the cathode gas reactions in polymer electrolyte fuel cells. When a permanent magnet was set behind a cathode, i.e. platinum foil or Pt-dispersed carbon paper for both electrochemical and rotating electrode experiments and oxygen was supplied to the uphill direction of the magnetic field, electrochemical flux was enhanced and the current increased with increasing the absolute value of magnetic field. This magnetic effect can be explained by the magnetic attractive force toward O2 gas. When magnet particles were included in the catalyst layer of the cathode and the cathode was magnetized, the current of oxygen reduction was higher than that of nonmagnetized cathode. A new design of the cathode catalyst layer incorporating the magnet particles was tested, demonstrating a new method to improve the fuel cell performance.

Control of natural convection in non- and low-conducting diamagnetic fluids in a cubical enclosure using inhomogeneous magnetic fields with different directions

A magnetization force caused by an inhomogeneous magnetic field is a body force and acts on both paramagnetic and diamagnetic fluids. Most practically important fluids are diamagnetic. In this paper, the magnetic effect on natural convection in non- and low-conducting diamagnetic fluids is numerically investigated, focusing on the effects of the direction of magnetization force and the dependence of Ra. The studied fluid is confined in an electrically insulating rectangular cavity and the convection is driven by a horizontal temperature gradient (x-direction). Computations are carried out for non-conducting (Pr=7.0) and low-conducting fluids. When a magnetic field is applied on a non-conducting fluid vertically along the z-direction or horizontally along the x-direction, whether the natural convection is promoted or damped is found to depend on the direction of the magnetization force. As the field is applied horizontally along the y-direction, the natural convection is only weakly promoted. For low-conducting fluids on which both Lorentz and magnetization forces act, the efficiency of damping convection increases, compared with non-conducting fluids, while that of promotion is reduced. For both fluids, the dependence of the promotion or damping efficiency on Ra is also discussed.

Magnetic control of thermal convection in electrically non-conducting or low-conducting paramagnetic fluids

Abstract An inhomogeneous magnetic field exerts a magnetization force on all materials, including electrically conducting and non-conducting fluids. A recent experiment demonstrated that this force can enhance or suppress convection in a paramagnetic aqueous solution heated from either below or above. In this paper, to clarify the mechanism of the observed phenomena, we numerically simulated the effect of a vertical magnetic field gradient on thermal convection in paramagnetic fluids. These simulated results agree with experimental observations. Our study shows that the magnetic buoyancy force has potential applications for controlling convection and enhancing the heat transfer efficiency in either electrically non-conducting or low-conducting fluids.

Numerical simulation of a new water management for PEM fuel cell using magnet particles deposited in the cathode side catalyst layer

Cathode flooding caused by excessive liquid water is generally recognized as the primary reason for poor cell performance. Recently, when some magnet particles are deposited in the catalyst layer of a cathode and magnetized, the cell performance has been improved compared with that of non-magnetized case. Numerical simulation to explain this phenomenon shows (1) the repulsive Kelvin force caused by the magnet particles manages the liquid water flow in the porous electrode layer; (2) the saturation level of liquid water (s) near the catalyst interface decreases with increasing the residual magnetic flux density of the magnet particle (Br); (3) the magnet particles improves the fuel cell performance by decreasing the value of s and making more pore space for oxygen gas, and the cell performance of a proton-exchange-membrane (PEM) fuel is improved in the current limited region.