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We investigated the effect of paramagnetic salts (NiCl2, CoCl2, and MnCl2) on the magnetic orientation of hen-egg white lysozyme (HEWL) crystals at different pHs. Multiple orientation responses of the crystals to magnetic fields were discovered when NiCl2 and CoCl2 were used as the crystallization agents (the c-axis and the ⟨110⟩ orientations for NiCl2 solution, and the c-axis, the a-axis and the ⟨110⟩ orientations for CoCl2 solution). Only the normal c-axis orientation was found when MnCl2 was used as the crystallization agent. The multiple orientation responses were sensitive to the variations in the pH. These phenomena are discussed in the context of the incorporation of paramagnetic cations into lysozyme. Although anions affect the crystallization of lysozyme, the effect of cations on the crystallization of lysozyme has been considered marginal. This study reveals that cations can also exhibit profound effects on the crystallization of lysozyme.

According to the experiments by Vekilov et al., the crystal growth rate, G c of tetragonal lysozyme crystal initially increases up to 200 μm/s with increasing flow velocity, u m and then decreases monotonically. While in the lower supersaturated solution, G c decreases monotonically with increasing u m , and the growth cessation occurs at u m =1450 μm/s. In this paper, we propose a new theory to explain these complicated experimental results. We consider one protein molecule near the crystal surface and define a dimensionless number r , the ratio of the velocity of convective flow to the diffusion velocity of a protein molecule. When convection occurs along the crystal surface and a molecule diffuses toward the crystal surface, r indicates the moving direction of the molecule and is closely related with crystal growth rate. We derive the equation to calculate r from experimental parameters. Analyzing the experimental results in the literatures, we find that the dependence of G c on u m is related with r and there exist three critical r -values, r 1 ≈4–8, r 2 ≈0.01–0.02, r 3 ≈0.004. When r > r 1, crystal growth cession occurs; when r 1 > r > r 2 , G c decreases with u m ; when r 2 > r > r 3 , G c increases with u m ; when r r 3 , G c is independent of u m . Though our model is very simple, the dimensionless number r can explain the effects of convection on crystal growth rate consistently.

Magnetic field has been found to be able to improve the quality of some protein crystals; containerless condition is considered to be beneficial for growing good-quality crystals. Nevertheless, there has been no report on combination of these two conditions for protein crystallization. In this paper, crystallization and dissolution of protein crystals in a levitated containerless droplet in a strong magnetic field has been successfully achieved. New phenomena were observed for both crystallization and dissolution processes.

About 30% of the protein crystals grown in space yield better X-ray diffraction data than the best crystals grown on the earth. The microgravity environments provided by the application of an upward magnetic force constitute excellent candidates for simulating the microgravity conditions in space. Here, we describe a method to control effective gravity and formation of protein crystals in various levels of effective gravity. Since 2002, the stable and long-time durable microgravity generated by a convenient type of superconducting magnet has been available for protein crystal growth. For the first time, protein crystals, orthorhombic lysozyme, were grown at microgravity on the earth, and it was proved that this microgravity improved the crystal quality effectively and reproducibly. The present method always accompanies a strong magnetic field, and the magnetic field itself seems to improve crystal quality. Microgravity is not always effective for improving crystal quality. When we applied this microgravity to the formation of cubic porcine insulin and tetragonal lysozyme crystals, we observed no dependence of effective gravity on crystal quality. Thus, this kind of test will be useful for selecting promising proteins prior to the space experiments. Finally, the microgravity generated by the magnet is compared with that in space, considering the cost, the quality of microgravity, experimental convenience, etc., and the future use of this microgravity for macromolecular crystal growth is discussed.

Recent experimental results show that performance of a proton exchange membrane (PEM) fuel cell is improved when small particles of permanent magnet are deposited in the catalyst layer on the cathode side. In this study, the mechanism of this phenomenon was clarified by using numerical simulation. Permanent magnet particles induce a Kelvin (magnetic) repulsive force against liquid water and an attractive force towards oxygen gas. To precisely study the behavior of oxygen and liquid water flows near the interface between the catalyst layer and gas diffuser, the simulation domain included the catalyst layer and gas diffuser. The simulation results revealed the following. The Kelvin repulsive force against liquid water mainly “manages” the liquid water flow and improves the performance of the fuel cell, especially in the current-limited region. In the presence of Kelvin forces, the liquid water saturation near the interface between the catalyst layer and gas diffuser decreases, thus making more pore space available for transport of oxygen gas. Furthermore, the water velocity moving from the interface increases in the upstream region. The gas velocity near the interface also increases, and thus more oxygen is supplied to the reaction sites. In summary, the Kelvin force promotes removal of liquid water from the catalyst layer, thus providing more oxygen to the catalyst and improving the performance of the fuel cell.

Recently, it was found that the performance of proton-exchange membrane (PEM) fuel cells was improved by the deposition of small magnet particles in the cathode-side catalyst layer. We developed a numerical simulation to clarify this effect, for a PEM fuel cell equipped with an interdigitated gas distributor. A two-dimensional, two-phase model was used. Cathode electrode consisted of gas diffusion layer and catalyst layer, and the latter was treated as a line. Darcy's law was used to describe the transport of the gas phase. The forces from the shear of the gas flow and of the capillary action move the liquid water through the porous cathode electrode. The magnetic field was modeled by using an equivalent magnetic field. Our numerical results show that the repulsive Kelvin forces acting on liquid water can control the liquid water flow through a porous gas diffusion layer. With increasing residual flux density of magnet particles, the velocity of liquid water near the interface of the catalyst/diffusion layers increases, the saturation of liquid water near the interface decreases, and increasing more pore space is freed for O2 transport and reactions. Therefore, the mechanism of the improvement of the cell performance by magnet particles is clarified using such a numerical model. The use of permanent magnets will be especially useful for portable fuel cell in which there is no power to supply air.

As one of the best candidates for simulating the microgravity conditions in space, low gravity environments provided by applying an upward magnetic force have been considered to grow protein crystals. Since 2002, the stable and long-time durable microgravity generated by a superconducting magnet has been available for protein crystal growth. In this paper, for the first time, we grew protein crystals (orthorhombic lysozyme crystals) at quasi-microgravity. The present study showed that quasi-microgravity improves the crystal quality effectively and reproducibly. The application of strong magnetic field also improves the crystal quality. Furthermore, it is possible to know if microgravity is effective for the improvement of crystal quality or not by growing crystals in microgravity and hypergravity inside the superconducting magnet and comparing the crystal quality with each other. Such test will be useful to select promising proteins prior to the space experiments.

The effect of an external magnetic field on convection in crystal growth is investigated numerically. The geometry considered is a cylindrical vessel filled with crystal solutions. The vessel partially heated from below is placed outside or inside a superconducting magnet. Numerical simulations show that the convection can be suppressed or promoted mainly due to the location of the vessel in the magnet. When the vessel is located above the center of the magnet, the convection is reduced more greatly than that at the center of the magnet. However, when the vessel is located below the center of the magnet, the convection is greater than that at the center of the magnet and that outside the magnet in absence of the field. The above results demonstrate that both magnetic effects on convection in solution will occur due to the magnetic field and its gradient. Generally, the magnetic field will induce the Lorentz force to damp the convection when the solution is electrically conducting. On the other hand, the m...

Magnetic fields (either horizontal or vertical) were found to drastically change the morphology of protein (orthorhombic lysozyme) crystals. A pair of {011} faces evident in crystal grown in the ab...

Chlorides with different paramagnetic cations such as Ni 2+ , Co 2+ and Mn 2+ were used as crystallizing agents instead of NaCl to crystallize hen egg-white lysozyme. NiCl 2 was found to give two types of crystals with different morphologies: one (roof-like) is a new type of orthorhombic P2 1 2 1 2 1 crystal with lattice constants a =79.0 A, b =80.8 A, and c =37.5 A; the second is an ordinary tetragonal crystal of its characteristic shape with a = b =80 A and c =38 A. The appearance of the roof-like shape became dominant in the presence of a magnetic field. In the case of using CoCl 2 and MnCl 2 , ordinary tetragonal crystals were formed. A striking fact was that the a -axis of the crystals oriented along the magnetic field when CoCl 2 was used, as opposed to the usual c -axis orientation. Large and optically perfect lysozyme crystals can be obtained in a magnetic field when NiCl 2 or MnCl 2 is used as a crystallizing agent. These profound effects of the paramagnetic cations may be caused by the coordination of Ni 2+ and Co 2+ ions to a lysozyme molecule, which was found by X-ray crystallography.

Recently, better quality protein crystals have been obtained by using a superconducting magnet. One of important factors that determine crystal quality is natural convection in the fluid where the crystals are grown. This paper presents a comprehensive, comparative numerical study of natural convection around a growing protein crystal when a vertical magnetization force caused by a gradient magnetic field acts on protein aqueous solution and the viscosity of the solution increases. The study shows that natural convection around a crystal can be damped most effectively and the crystal growth rate is reduced when an upward magnetization acts on a protein solution and the viscosity increases. The decrease of crystal growth is thought to contribute to the improvement of crystal quality. The technique of obtaining low gravity environments and damping natural convection in electric low- arid non-conducting fluid will be useful for the preparation of many materials.

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.

The effect of a strong magnetic field on protein crystal growth is a new research field. Here, we review research on protein crystallization in magnetic fields, including magnetic orientation of protein crystals, magnetic control of effective gravity on earth, formation of protein crystals in various effective gravity, magnetic improvement in crystal quality, magnetic increase in viscosity of protein aqueous solutions, damping of natural convection by Lorentz force, etc. Four mechanisms are currently known to be involved in the effects of magnetic fields on protein crystal growth and all of them may contribute to the improvement of crystal quality. High quality protein crystals are critical in determining the structure of protein molecules by using X-ray diffraction analysis. Strong magnetic fields will help to improve crystal quality.

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. Keywords: Water management, Kelvin force, Magnet particles, Numerical simulation, Proton exchange membrane fuel cell

Recently, a superconducting magnet was used to obtain better quality crystals and the application of a high magnetic field was found to improve the crystal quality and increase the viscosity of an aqueous solution of protein. In this paper, we numerically studied how the magnetically induced increase of viscosity affects natural convection in the vicinity of a growing protein crystal and showed that the increase of viscosity damps partially natural convection under 10 T. An important factor that determines crystal quality is natural convection in the fluid where the crystals are grown. This type of magnetic damping of convection is considered to contribute to the improvement of crystal quality caused by the application of not only a uniform but also a gradient high magnetic field.

Magnetic damping of natural convection in low-conducting aqueous solution was numerically studied for 0⩽Hartmann number ( Ha )⩽36.67, 1000⩽Grashof number ( Gr )⩽39810 and 0.1⩽the aspect ratio of a container ( AR )⩽1.0. The ratio of averaged Nusselt number ( Nu ave ) with and without magnetic field, Nu r =( Nu ave B −1)/( Nu ave0 −1), was used to quantify the damping efficiency of natural convection. The results reveal that the magnetic damping of natural convection is strongly dependent on the aspect ratio of the container and there exists an optimum AR for minimizing natural convection. The optimum value of AR is almost independent of Ha and shows the tendency to decrease with increasing Gr . Correlation equations for Nu r and the ratio of averaged velocity with and without magnetic field with AR , Gr and Ha were given.

Recently, a superconducting magnet has been used to obtain better quality crystals. The time dependence of the birefringence (Δ n ) of protein solutions caused by the application of a strong magnetic field was studied. For the solution from which crystals are easily formed, Δ n increased with time when a uniform magnetic field of 10 T was applied. Δ n showed the tendency to increase with increase in the concentrations of lysozyme and NaCl. Δ n continued to increase even after shutting down the field. If the protein solution was never exposed to the field, Δ n did not increase. The appearance of Δ n suggests the molecular ordering along the direction of a magnetic field in the solutions from which crystals are easily formed. These results can be explained by considering the formation of an interlinked network of protein molecules under a high magnetic field.

When an upward magnetization force F m is imposed on a liquid, the force acting on the liquid is the difference between the gravitational and magnetization forces. Thus, the magnitude of vertical acceleration acting on the liquid can be varied from 1 g to 0 g by changing the upward F m . To verify this vertical acceleration-control method, behavior of bubbles formed by injecting gas from a nozzle was examined. By decreasing the magnitude of vertical acceleration, the number of bubbles formed per unit time decreased and their size increased. These results confirm that vertical acceleration can be changed from normal gravity to near-zero gravity. The method to generate low-gravity conditions will find many applications over a wide range of research

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.

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.

The effect of a uniform magnetic field of 10 T on the viscosity of aqueous protein solutions was studied, using two kinds of the solution. When the solution was prepared for crystals not to be easily formed therein and it contained unsolved small crystals, the viscosity increased when a magnetic field of 10 T was applied and it returned to its initial value after shutting off the magnetic field. This phenomenon was explained by the magnetic orientation of small crystals suspended in the solution. On the other hand, when the solution was prepared in which crystals are easily formed, the viscosity increased with time of applying a field of 10 T. When the field of 10 T was applied for 3 h on this solution, the viscosity did not return to its initial value after shutting off the magnetic field. This experimental result suggests that the application of 10 T for a long time might affect the structure of this type of solution. The improvement of crystal quality and the decrease of crystal growth rate under high magnetic fields can be explained by the damping of natural convection caused by these two kinds of magnetically induced increase of viscosity.

We numerically simulated sedimentation flow and buoyancy-driven convection during protein crystal growth in which the crystal size changes from 0.1 to 100 μm and clarified how gravitational fields affect the various stages of crystal growth. When the crystal size is below a few μm, most crystals are suspended in solution and solute transport near the crystal is mainly limited by diffusive transport. When the crystal size is above a few μm, sedimentation flow dominates near the crystal, but solute transport is still mainly limited to diffusive transport. When crystals grow to several μm, most of them settle to the bottom and continue to grow there. When the size is above several 10 μm, buoyancy-driven convection dominates solute transport near growing crystals at the bottom, and the contribution from buoyancy induced convection to crystal interfacial growth rate appears on Earth in comparison with that under zero-gravity condition and increases with increasing crystal size. During the whole crystal growth process, the crystal interface growth rate shows the tendency to decrease as the crystal grows under both normal and zero-gravity conditions. Moreover, our simulations of crystal sedimentation are consistent with experimental observations of lysozyme crystallization that most crystals settle to the bottom when their size reaches several μm.

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.

We present numerical simulations of the velocity and temperature distributions of a nonconducting fluid (water) heated from below in the presence of an imposed, nonuniform magnetic field, generated with a solenoid-type magnet. The vertically placed magnet induces horizontal and vertical magnetic forces due to the gradient of magnetic strength, and the horizontal force is found to play an important role to damp natural convection. When an imposed magnetic field of strength H 0 in the middle of the magnet, is less than a critical value, H 0c , the damping effect increases with increasing H 0 . For H 0 > H 0c , natural convection is completely replaced by convection induced by the magnetic field. Our results indicate a novel method to control convection of nonconducting fluids, especially in crystal formation processes.

We report in space experiments about the use of magnetic force, which is generally shown by the product of density (ϱ), weight magnetic susceptibility (χ), magnetic field strength (H) and its gradient (dH/dy). The magnetic force caused by strong permanent magnets was proved to induce buoyancy and convection in μ G as follows: (1) Transport of bubbles in fluid: In most fluids which are diamagnetic, the magnetic buoyancy force could transport bubbles toward a stronger magnetic field. Collision and fusion of two bubbles was also observed. (2) Magnetic Support of Chemical Reaction (2H2O2 → O2+2H2O on Pt Catalyst): In μ G, the decomposition reaction continued smoothly when O2 bubbles were removed from the surface of catalyst by magnetic buoyancy force. In the absence of the field, the reaction was observed to stop. (3) Magnetic Support of Combustion in Diffusion Flames: Magnetic convective air flow could support combustion in μ G.

Numerical computations are made of axisymmetric laminar hydrogen jet diffusion flames, focusing on the unsteady behavior under microgravity and the effects of magnetic field. In the computations, multicomponent diffusion and detailed chemical kinetics are considered. In the condition under microgravity without magnetic field, it is revealed that combustion products remain around the diffusion flame because of the lack of natural convection, and that the amount of O2 diffusing to the flame region becomes retarded. That is the reason why the heat release rate in the diffusion flame decreases with the lapse of time. When a gradient magnetic field is added, convection is induced around the diffusion flame by the magnetic field which induces magnetic buoyancy force due to the inhomogeneity of magnetic susceptibility. The flow configuration formed by the magnetic force under microgravity is similar to that under the normal gravity without the magnetic force. The positive gradient of the magnetic field induces the reverse convection which forms the depressed and flattened flame in the normal gravity field. The negative gradient of the magnetic field accelerates the flow together with the normal gravity.

One of the advantages of crystal growth under microgravity conditions is the damping of solute convection that deteriorates crystal quality. However, there have been few methods to damp solute convection on the earth. When crystals grow floating at the air-solution interface, solute convection is damped considerably. It is proved to be possible to float some protein crystals by applying a magnetic field gradient even when all of crystals, solvent and crystallization agents are diamagnetic. For albumin and DNA, the magnetic field gradients, B(dB/dy) necessary for floating crystals are estimated to be 972 and 808 T2/m, respectively. Floating a crystal by applying a magnetic field gradient is the effective method of damping solute convection during crystal growth on the earth.

The magnetic buoyancy force acting on a bubble in a one-dimensional magnetic field can be represented as F=(χ G −χ L )∫H(dH/dx)d Vol B , where χ G and χ L are the volume magnetic susceptibilities of the gas and liquid, respectively, and H is the magnetic field strength. Since |χ L |≫|χ G | and most liquids are diamagnetic, this expression indicates that the magnetic buoyancy forces act in the direction of increasing magnetic field strength. Because the magnetic buoyancy force in a diamagneticfluid is small, the motion of bubbles under normal gravity is difficult to study, but microgravity offers the possibility of detailed observations. Using a compact permanent magnet under microgravity conditions, N 2 bubbles in pure water (0.01 dyne s/cm 2 ) and in a 69:31 glycerol/water mixture (0.21 dyne s/cm 2 ) were found to move in the direction of increasing H, and to be held stationary at the point of maximum H. The motion of the bubbles was also simulated with a theoretical model and was found to agree with measurements made under microgravity conditions. These results indicate that magnetic buoyancy can be used to control bubble motion. Since most fluids are diamagnetic, magnetic buoyancy can be used to control bubbles in many fluidic devices used in space applications.

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.

Recently, magnetic field gradients have been found to induce gas flow and promote combustion in diffusion flames. For example, when N2 gas stream was injected into air toward a weaker magnetic field, it was accelerated and behaved like a jet stream. This phenomenon was explained qualitatively by a magnetic attractive force acting on paramagnetic oxygen gas. In this study, such a magnetically induced jet stream of N2 gas was quantitatively analyzed. First, the magnetic body force acting on the gas flow and the governing equation of magnetic gas dynamics are presented. Using them, a numerical simulation was carried out for N2-Air convective flow under a magnetic field gradient. Calculated results show that the jet flow is accelerated to 80 cm/sec when the initial N2 gas velocity is 3.9 cm/sec and maximum magnetic induction is 1.5 T. Furthermore, calculation shows the existence of a convective air flow around the N2 jet flow. The results of the present study show good agreement with the experimental results.

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.

Inhomogeneous magnetic fields have been found to promote combustion reactions in diffusion flames. When a fuel gas flowed in the direction of a decreasing field strength, the burning velocity was found to increase. No magnetic effect was observed when it flowed into a homogeneous field. Furthermore, when a large diffusion flame was situated around the center of the magnetic field the intensity of which increased centripetally, the combustion reaction was also found to be promoted. The behavior of gas flows under gradient fields was studied. The magnetic promotion of combustion can be explained by the magnetically induced flow of air. The supply of air to the flame front increased by applying inhomogeneous field. Furthermore, the convection of air was also magnetically promoted. The present results suggest the possibility of controlling combustion in diffusion flames by applying inhomogeneous magnetic fields.

When a fuel gas flowed in the direction of a decreasing field strength, inhomogeneous magnetic fields were found to promote combustion in diffusion flames. On the application of a magnetic field gradient (H(dH/dy) = 35 T2/m), the flame temperature increased by about 120° and the flame became shorter and more brilliant. Magnetic promotion of combustion was explained by the following two kinds of air flow caused by the magnetic force acting on paramagnetic O2. The supply of air to the flame front increased because of the magnetic attractive force. Furthermore, magnetic convection occurred along the steepest gradient of the field because χ is linear to p O 2 / T 2 . The present results suggest the possibility of magnetic control of combustion and air flows (magnetoaerodynamics).

When a fuel gas flows in the direction of a magnetic field of decreasing strength, a combustion reaction is found to be activated. The relationship between the direction of a fuel-gas flow and the steepest gradient of the magnetic field was observed to determine how the reaction was promoted. This magnetic effect has been explained by the movement of the reactants and reaction products caused by gradient magnetic fields. The results suggest that a chemical reaction involving a change in the magnetic susceptibilities of component species can be controlled by application of a gradient magnetic field.

The accuracy of the structures of biological macromolecules determined by X-ray crystallography is of fundamental importance, both for the understanding of life processes and for medical applications. The resolution of the structure is thus critical, and is largely determined by the quality of single crystals. Here we report the results of applying a magnetic field and a magnetization force during growth of the snake muscle fructose-1,6-bisphosphatase and human estrogenic 17β-hydroxysteroid dehydrogenase crystals. For both enzyme proteins, the quality of the crystals improved with repeated assay, and their data sets were collected at significantly higher resolutions. These results coincide with a mechanism involving the reduction of convection, due to both the hydrodynamics within a magnet and the partially reduced gravity induced by a magnetization force. The density difference between the crystal and solution becomes less significant, and the sedimentation speed of the crystals is also reduced in the presence of the magnetization force.

A flow of nitrogen gas in air is found to be accelerated when it travels in the direction of a decreasing magnetic field ( 1.3 T, −0.3 T/cm) available from an ordinary electromagnet. This observation is explained as being due to the inhomogeneity of the magnetic field affecting the interface of the gas groups having different magnetic susceptibilities.

The behavior of gas flow in air has been demonstrated visually under gradient magnetic fields in the range 0–40 T/m under 0–1.5 T. The magnetic behavior depended on the concentration of oxygen. Pure oxygen or nitrogen mixed oxygen (≳30%) was observed to be attracted by a magnetic field and act like a magnetic fluid where the magnetic effect on the gas was comparable to that of normal diffusion. In contrast, nitrogen gas escaped from magnetic fields of high intensities, and no magnetic fieldeffect was observed for the flow of air. These phenomena were explained by the difference between the force acting on the gas and that acting on the air surrounding it under gradient magnetic fields. The magnetic force increased with increasing concentration of oxygen. This explanation can be also applicable to the escape of flames from magnetic fields of relatively high intensity or the magnetic quenching of flames inside a pair of columnar poles.

Magnetic force, i.e., magnetization force is body force and the function of density, and it is possible to induce buoyancy and convection similarly to the gravitational one. Magnetization force under 1D magnetic field gradient is generally shown by the product of density (p), mass magnetic susceptibility (x g ), magnetic field strength (H) and its gradient (dH/dy). Several experiments to control bubbles by using magnetic buoyancy forces were conducted under microgravity as follows: (1) Magnetic transport of bubbles: In pure water and glycerol/water mixture which are diamagnetic, the magnetic buoyancy force caused by a strong permanent magnet could transport bubbles toward a stronger magnetic field and to fix bubbles at the maximum point of magnetic strength. The transporting velocity was found to decrease with decreasing the radius of bubbles and increasing the viscosity. (2) Collision and fusion of two bubbles: It is almost impossible to observe the collision of bubbles clearly on the earth. the technique of magnetic control of bubbles nd microgravity condition made this observation possible. (3) Magnetic support of chemical reaction to produce bubbles (2H 2 O 2 →O 2 +2H 2 O on Pt catalyst). When small O 2 bubbles were removed from the surface of catalyst by magnetic buoyancy force, the decomposition reaction was observe to continue smoothly even under microgravity. On the other hand, in the absence of the magnet, the reaction was observed to stop under microgravity. Thus, the present study suggest the potential of using magnetic buoyancy forces to control bubbles in space experiments.

Because magnetization force is body force, it is possible to induce convection and buoyancy driven flows. A vertical magnetization force can modify the vertical acceleration and quench natural convection. The effect of horizontal and vertical magnetization forces on natural convection is studied. We present numerical simulations of the velocity and temperature distributions of a nonconducting fluid heated from below in the presence of an imposed, nonuniform magnetic field, generated with a solenoid-type magnet. The vertically placed magnet induces horizontal and vertical magnetic forces due to the gradient of magnetic strength, and the horizontal force is found to play an important to damp natural convection. When an imposed magnetic field of strength H0 in the middle of the magnet, is less than a critical value, H0c, the damping effect increases with increasing H0. For H0 > H0c, natural convection is completely replaced by convection induced by the magnetic field. These results were discussed, comparing either the effect of vertical forces. Our results indicate a novel method to control convection of nonconducting fluids, especially in crystal formation processes.

Containerless processing of materials is considered beneficial for obtaining high quality products due to the elimination of the detrimental effects coming from the contact with container walls. Many containerless processing methods are realized by levitation techniques. This paper describes a containerless levitation setup that utilized the magnetization force generated in a gradient magnetic field. It comprises a levitation unit, a temperature control unit, and a real-time observation unit. Known volume of liquid diamagnetic samples can be levitated in the levitation chamber, the temperature of which is controlled using the temperature control unit. The evolution of the levitated sample is observed in real time using the observation unit. With this setup, containerless processing of liquid such as crystal growth from solution can be realized in a well-controlled manner. Since the levitation is achieved using a superconducting magnet, experiments requiring long duration time such as protein crystallization and simulation of space environment for living system can be easily succeeded.

In this paper, we numerically studied the magnetic damping of thermal convection in a low-conducting aqueous solution as a function of Grashof numbers (Gr), and Hartmann numbers (Ha), focusing on the effects of the aspect ratio of a rectangular container (0.1≤AR≤1AR). Two different magnetic field directions are considered. The ratio of averaged Nusselt number (Nuave) with and without magnetic field, Nur and the averaged velocity ratio, VaveB/Vave0 are used to quantify the degree of damping of natural convection. The results show that there exists an optimum AR for minimising natural convection, i.e., Nur when magnetic field is applied along Z-direction, but Nur increases with decreasing AR from 1 to 0.1 when magnetic field is applied along X-direction. The correlations of Nur and VaveB/Vave0 are given on parameters of AR, Ha and Gr. These results will be useful to determine the most efficient experimental conditions to damp natural convection during solidification of a material.

The particle image velocimetry (PIV) technique was used to investigate the N2-air convection caused by the application of magnetic field gradients. When the magnetic field was applied (1.5 T at the center of an electromagnet) and N2 gas was injected into air toward a weaker magnetic field, the surrounding air was found to be drawn toward a stronger magnetic field forming a vortex, while the N2 gas was pushed out. The maximum velocity of the N2 gas with the field was about five times larger than that without the field. These results agree well with the results of numerical simulations.

In cathode gas reactions of polymer electrolyte fuel cells, oxygen gas is reacted with H+ to produce water on platinum catalyst. The magnetic effect on this electrochemical oxygen reduction was studied. When a magnet field gradient was applied to the cathode by setting a permanent magnet behind it and oxygen gas was supplied toward a stronger magnetic field, electrochemical flux was enhanced. The current increased with increasing magnetic field strength. Magnetic promotion of the cathode reaction was explained by the magnetic attractive force toward paramagnetic O2 gas. The present study demonstrates how fuel cell performance can be improved.

A gradient magnetic field which was not homogeneous was found to have a significant effect on a surface oxidation performed with platinum catalyst. When a fuel gas flowed in the direction of decreasing magnetic strength, surface oxidation was found to be promoted. On the other hand, when a fuel gas flowed in the direction of increasing magnetic strength, the reaction was quenched. These magnetic effects were explained by the movement of the reactants and chemical products in and from the reaction zone caused by the magnetic forces under magnetic-field gradients. The present results suggest a novel method to efficiently control oxidation reactions on the surface of catalyst.

Air flows under a magnetic field at an intake are examined by means of numerical simulation. The air flow is caused by the pressure difference and the flow rate is measured to determine the effect of the magnetic field at the intake. The flow is assumed to be compressible and inviscid. Under the magnetic field, the air flow rate at the intake is more than double that without the magnetic field after having reached steady flow. Even in the inviscid flow, vortices are generated under the magnetic field and after their movement the air flow increased markedly.

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.

Whether the chemiluminescence of OH radicals in hydrogen–oxygen flames is magnetically enhanced or quenched is found to depend on the combustion conditions, as well as the rotational quantum number (K′) of the A2Σ+ state, and the F1, F2 components.