Masao Fujiwara

Magnetic Levitation of Plastic Chips: Applications for Magnetic Susceptibility Measurement and Magnetic Separation

Magnetic levitation of polyethylene, polycarbonate, polypropylene, polystyrene, poly(methyl methacrylate) and polyamide was carried out using a compact superconducting magnet (vertical bore, 1500 T2 m-1). First, their diamagnetic susceptibilities were calculated from the product of the magnetic field and the field gradient necessary for levitation. Second, polypropylene, polyamide, and poly(ethylene terephthalate) chips were separated by magnetic levitation. Magnetic levitation is shown to be a convenient and useful technique for both diamagnetic susceptibility measurements and magnetic separations of diamagnetic substances.

In situ Observation of Laser-Induced Convection of Benzene Solution of Photochromic Compound in High Magnetic Fields

In situ observation of thermal convection of a benzene solution of a photochromic compound, 1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene (CMTE), was carried out in vertical high magnetic fields. When a CMTE solution is irradiated using a UV laser from the bottom of a vessel, CMTE undergoes photoisomerization to its photoisomer (PI) and the color of the PI solution changes from pale yellow to red. At zero field, the PI solution formed on the bottom surface of the vessel is removed at a 5 s delay after laser excitation and then moves upward. At -1300 T2m-1, it is removed at a 9 s delay and moves upward, whereas at +1000 T2m-1, it does at a 3 s delay, moves upward and then finally moves downward. All these results are discussed in terms of the magnetic force in the CMTE/PI solution.

Magnetic orientation of carbon nanotubes at temperatures of 231 K and 314 K

Carbon nanotubes were placed in magnetic fields of ⩽ 80.0 kOe at temperatures of 231 K and 314 K. Scanning electron microscopy showed that nanotubes were oriented with the tube axis parallel to the fields. It was also observed that the probability of the orientation became higher, when the temperature was raised from 231 K to 314 K. The anisotropy in the susceptibilities parallel X∥ and perpendicular X ⊥ to the tube axis is suggested to increase with rise in temperature: X∥ − X⊥ = (4 ± 2) × 10−6 emu mol−1 (per mol of carbon atoms) at 231 K and X∥ − X⊥ = (45 ± 27) × 10−6 emu mol−1 at 314 K.

Macromolecular Crystallization in Microgravity Generated by a Superconducting Magnet

Abstract:  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.

Effect of horizontal strong static magnetic field on swimming behaviour of Paramecium caudatum

Effect of horizontal strong static magnetic field on swimming behaviour of Paramecium caudatum was studied by using a superconducting magnet. Around a centre of a round vessel, random swimming at 0 T and aligned swimming parallel to the magnetic field (MF) of 8 T were observed. Near a wall of the vessel, however, swimming round and round along the wall at 0 T and aligned swimming of turning at right angles upon collision with the wall, which was remarkable around 1–4 T, were detected. It was experimentally revealed that the former MF-induced parallel swimming at the vessel centre was caused physicochemically by the parallel magnetic orientation of the cell itself. From magnetic field dependence of the extent of the orientation, the magnetic susceptibility anisotropy (χ ∥-χ ⊥) was first obtained to be 3.4× 10-23 emu cell−1 at 298 K for Paramecium caudatum. The orientation of the cell was considered to result from the magnetic orientation of the cell membrane. On the other hand, although mechanisms of the latter swimming near the vessel wall regardless of the absence and presence of the magnetic field are unclear at present, these experimental results indicate that whether the cell exists near the wall alters the magnetic field effect on the swimming in the horizontal magnetic field.

Interactions of torsion with other vibrations in a molecule containing a symmetric top

Abstract The interactions between vibrations and torsion are re-examined theoretically for a molecule containing a symmetric top. Practically useful energy expressions are presented, which are applicable to an interpretation of the vibration—torsion spectrum. The atoms are assumed to make small vibrational displacements about a torsional reference configuration, which is characterized by a particular value of a torsional angle. The symmetry coordinates are introduced in the frame-fixed axis system. The F matrix is separated into a constant part and a variable part. The latter is a function of the torsional angle. The use of the constant part of the F matrix makes vibrational frequencies independent of the torsional angle. This leads to a simple calculation of the energy denominators occurring in the second-order pertubation sums for the effective hamiltonian for torsion. The perturbation energy denominators are left to contain torsional energy differences. The formulation is valid, when the magnitude of the torsional energy spacings are comparable with vibrational frequencies. Such a case is often encountered for a high barrier (1000 cm −1 ) to torsion. Various terms given by the perturbation technique include vibrational quantum numbers explicitly. The torsional energy levels for a certain vibrational state are evaluated by using a proper set of values for vibrational quantum numbers.

Raman and infrared studies on the effects of axial coordination to chlorophyll a.

溶液中のクロロフィルaと軸配位子(溶媒分子)の相互作用を振動スペクトルを用いて調べた。その結果,クロロフィルaのMg原子が五配位(軸配位子1個)から六配位(軸配位子2個)に変化するのにともなって,C=C伸縮に基づく赤外バンド(2本)およびラマンバンド(4本)が約10cm-1低波数シフトし,Mg-N伸縮に基づく遠赤外バンド(1本)が約20cm-1高波数シフトすることが明らかとなった。これらのシフトは,軸配位子数が1個から2個に変化するときに,Mg原子がクロリン環の平面外から中央に引き込まれるため,環のC=C結合が延びMg-N結合が縮むことに起因すると解釈された。生体中のクロロフィルaの配位状態を知るうえで,これらのバンドは鍵を握りうるものである。