稲富 裕光

Interferometry is a widely used technique for real-time monitoring of concentration variation during processes in a solution like crystal growth and dissolution. This paper reports a protein concentration measurement system using a conventional Mach-Zehnder interferometer that allows monitoring the time course evolution of the protein concentration distribution during the processes of crystallization or dissolution. The demonstrated method showed improved reliability and versatility in that it (1) enables measurements under versatile temperature conditions and (2) eliminates the unpredictable errors caused by the environmental disturbances. The measurement system described in this paper can also be applied in measurements in other solution systems. © 2008 IOP Publishing Ltd.

The reproducibility of biomacromolecular crystallization (tetragonal and orthorhombic lysozyme crystals) was studied by monitoring the evolution of protein concentration during the crystallization process using Mach-Zehnder interferometer. It was found that formation of both tetragonal and orthorhombic crystals exhibited poor reproducibility. When the crystallization occurred under isothermal conditions, the protein concentration in the solution varied differently in different experiments under identical conditions (for both types of crystals). Moreover, in the case of orthorhombic lysozyme crystallization (under either isothermal or thermal gradient conditions), it is clear that the crystals could not be always readily formed. When formation of tetragonal lysozyme crystals was conducted at a temperature gradient condition, however, the evolution of concentration was reproducible. The phenomena found in this study revealed that biomacromolecular crystallization can be uncertain, which is probably caused by the process of nucleation. Such uncertainties will be harmful for the efforts of screening crystallization conditions for biomacromolecules. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

ドラッグフリー技術に基づいた新しい自由落下カプセルを,2006年5月に高高度気球B200を用いて高度40km から投下し,微小重力実験が行われた。今回の最初の試験飛行により,三陸大気球観測所の制御室とカプセルとの間での無線通信,ドラッグフリー制御,そして飛行シーケンスを分析するための基本的データを得ることに成功した.

In situ observation experiments of faceted cellular growth will be carried out in transparent organic alloy, salolt-butyl alcohol in microgravity conditions using a sounding rocket and the International Space Station. The growth rate and the profiles of temperature and solute concentration in the vicinity of the solid-liquid interface will be simultaneously measured by microscopic interferometers in order to evaluate the morphological instability taking account of released latent heat in faceting material.

It has been shown by numerical simulations and by analysis of crystals that buoyancy convection in liquid might be suppressed at a particular rotation rate on a centrifuge. In the present study a damping effect that the Coriolis force has on buoyancy convection in low Prandtl number on a centrifuge was numerically analyzed under the condition of a free-swinging configuration. It is shown that the nondimensional angular velocity characterizes the minimum value of the flow velocity.

The density and thermal conductivity of a high-purity silicon melt were measured over a wide temperature range including the undercooled regime by non-contact techniques accompanied with electromagnetic levitation (EML) under a homogeneous and static magnetic field. The maximum undercooling of 320 K for silicon was controlled by the residual impurity in the specimen, not by the melt motion or by contamination of the material. The temperature dependence of the measured density showed a linear relation for temperature as: ρ(T) = 2.51 × 10 3-0.271(T-T m) kg • m -3 for 1367 K < T < 1767 K, where T m is the melting point of silicon. A periodic heating method with a CO 2 laser was adopted for the thermal conductivity measurement of the silicon melt. The measured thermal conductivity of the melt agreed roughly with values estimated by a Wiedemann-Franz law. © Springer Science+Business Media, LLC 2007.

This paper proposes a new micro gravity experimental system called BOV (Balloon-based Operation Vehicle). BOV uses a free-fall capsule with double-shell structure to prevent influence of aerodynamic disturbance. Additionally, BOV is raised to 40km by a high altitude balloon to extend micro gravity duration to 30(or possibly 60) seconds. Thus we realize a medium duration micro gravity system with good micro gravity environment. In this system, the most characteristic point is double-shell structure. The inner shell can fall freely since the outer shell measures the relative position with laser displacement sensors and is controlled by gas-jet thrusters not to collide the inner shell. Therefore the inner shell can be uninfluenced of the dynamic pressure and other aerodynamic disturbances ideally. The BOVs project has run since 2004. The first flight to check the whole system was accomplished in 2006. The aim of this flight was test of a high altitude balloon, communication and data handling system, control system, onboard electronics and operation. The second flight expected to achieve 30 seconds micro gravity was also accomplished on May in 2007. This paper presents the development of BOV's control system and shows the experimental results of micro gravity and consideration for effectiveness of the proposed system. Copyright 2007 by the IAF or the IAA. All rights reserved.

The analysis of isotope ratio in a material consisting of a single element was developed as a fundamental technique to determine a self-diffusion coefficient in a melt based on time-of-flight secondary mass spectrometry (TOF-SIMS). The self-diffusion coefficient for a pure Ge melt was measured using the stable isotope 73 Ge as a tracer under a homogeneous static magnetic field in order to evaluate the influence of thermal convection upon isotope distribution. The results obtained showed that the magnetohydrodynamic effect in the melt obviously damped the convection, but it was not strong enough for the self-diffusion measurement.

Application of a uniform magnetic field is expected to be a promising substitute for utilization of the microgravity environment from the view point of damping of convection in electrically conductive fluid. Measurements of interdiffusion coefficients in In80Sn20, Sn 95Pb5, and Ge97.5Si2.5 melts were performed in a wide temperature range up to 1473 K under a uniform and horizontal static magnetic field of 1 T by utilizing the magnetohydrodynamics effect in these melts. © Z-Tec Publishing.

The growth interface of CdZnTe crystals grown from Te solution with the THM technique under static magnetic field was investigated by a quenching technique during crystal growth. The results indicated that the growth interface obtained with a growth rate of 4 mm/day under magnetic induction of 3 T was improved greatly during solidification, as was the micro-structure of CdZnTe crystals. © 2005 Published by Elsevier B.V.

We carried out several analytical studies in order to determine the butanol distribution on a salol-butanol crystal. This work is required for a research using microgravity condition focused upon the in-situ observation with an interferometer of the temperature and concentration field for the organic transparent crystal (salol-butanol). In order to evaluate the concentration field for the liquid phase with an interferometer in case of crystal growth from solution in space, it is significant to determine the distribution of solute (butanol) on starting crystal before sample launching using a non-destructive analytical method. The Micro Raman Spectroscopy (MRS) was choice as the most appropriate analytical method among several analytical methods. We prepared a salol-butanol crystal enclosed into the 1mm thick quartz glass ampoule in order to verify the propriety for MRS. Obtained Raman spectrums for salol, butanol and salol-butanol crystal show that the butanol 2D-distribution on salol-butanol crystal can be determined by MRS. These results also demonstrate that there are no influences of thick glass cell upon measurements and that 3D-measurement is possible. In conclusion, we argue that MRS is the most appropriate method for determination of the 2D- and/or 3D-distribution of solute on the crystal among several non-destructive analytical methods.

本報告では,半導体結晶の溶液成長過程における以下の研究成果を述べる.(1)半導体結晶の溶液成長過程における固液界面の形態変化に及ぼす基板結晶の面方位の影響を調べるために近赤外顕微鏡を使ったその場観察実験が実施された.その結果,対流を抑制することでGaP/GaP成長界面のステップカイネティクス係数の面方位依存性が得られ,結晶成長時におけるマクロステップの挙動が評価された.また,GaAs_xP_<1-x>/GaPヘテロLPE 成長初期の固液界面の表面形態変化が基板表面の面方位依存性の視点から議論された.(2)静磁場THM 法によりTe 溶液から育成したCdZnTe 結晶の成長界面が急冷法によって調べられた.その結果,浮力対流を抑制することで速い引き下げ速度でも良質なCdZnTe 成長結晶を得られることを示した.

In situ observation experiments of semiconductor solution growth using a near-infrared microscope have been performed to investigate an influence of surface orientation of a substrate crystal upon the morphological change of the S/L interface. The orientation dependence of step kinetic coefficient at the interface in GaP/GaP growth was obtained under a reduced convection condition in order to evaluate a behavior of macrosteps during the growth. A morphological change of S/L interface at the early stage of GaAsxP 1-x/GaP hetero-LPE growth was also discussed from the view point of the surface orientation dependence. © 2004 Elsevier B.V. All rights reserved.

CdZnTe single crystal has been grown on CdTe substrate from Te solution with a traveling heater method under uniform static magnetic induction of 3 T. The growth experiments were carried out with growth rate of 4-10 mm/day and with temperature of 700-800 degrees C: The experimental results indicated that applying 3 T obviously improved the morphology of the growth interface in the crystal because of damping effect of the Lorentz force in Te solution, and that improvement of growth interface was beneficial to improve crystal micro-structure of CdZnTe. (C) 2004 Elsevier B. V. All rights reserved.

The growth of high quality large 40mm diameter HgCdTe (x = 0.210) crystals using a new two-stage Pressurized-Bridgman (P-B) method with a starting charge of x = 0.06 has been reported recently (J. Crystal Growth 263 (2003) 273). New information on the equipment which used N2 -pressurized chambers as safety features for the synthesis and crystal growth stages in order to avoid the explosion of the quartz ampoules due to the high mercury pressure is reported. Detailed characterization studies on crystals grown using this technique are discussed. The investigation showed that the large HgCdTe crystals grown at a low synthesis temperature of 720°C and a low growth temperature of 710°C had good compositional uniformity, crystallinity and electrical properties. Double-crystal rocking curve investigations showed that the best full-width at half-maximum was 14.4 arc sec. Both n type and p type wafers could be obtained after a low temperature heat treatment in a Hg atmosphere for about three weeks. Typical n type HgCdTe wafers had a carrier concentrations n 77<2 × 1014cm-3, mobility μ77 > 1.2 × 105cm2/Vs and minority carrier life-time τ > 2.0 μs (the best was 7.4 μs). For p type HgCdTe wafers, the carrier concentration was p77 < 1.2 × 1016 cm-3, mobility μ77>500cm 2/Vs. High performance HgCdTe IR devices have been prepared with these materials demonstrating the state-of-the-art quality of the large HgCdTe crystals. © 2004 Elsevier B.V. All rights reserved.

A two-stage technique has been used to grow large diameter Hg 1-xCdxTe crystals (x=0.214) using a pressurized Bridgman (P-Bridgman) method, with a starting charge of x=0.06. The two-stage technique has enabled the growth of large crystalline ingots of HgCdTe 40mm in diameter at the very low growth temperature of 680-720°C. It was shown that the HgCdTe crystal had a homogeneous composition of x=0.214 along the growth direction. © 2003 Elsevier B.V. All rights reserved.

Morphological stability of solid/liquid interface in semiconductor crystal growth from solution has been investigated using a near-infrared microscopic interferometer under a reduced convection condition by authors and Prof. Benz's group. In the result, step kinetic coefficient of the interface of GaP/GaP(111)B in liquid phase epitaxy growth was obtained and the estimated value of macrostep wavelength agreed well with the measured one.

This paper reports the measurement of temperature and concentration dependences of the refractive index of hen-egg-white lysozyme (HEWL) solution, and the temperature dependence of refractive index of the quartz container, which are indispensable for the efforts to measure HEWL concentration of the solution during the processes like crystal growth and dissolution using interferometer. As all of these dependences might be different under different observation wavelengths, temperatures and solution compositions, it is necessary to measure them for specific conditions. In this paper, the desired dependences were measured without knowing the actual value of the refractive index. The measurement method was introduced and the measurement experiments were undertaken at wavelength 780nm. The dependences obtained will be also useful for those studies employing the same wavelength and solution conditions.

Either a homogeneous or inhomogeneous magnetic field has been known to dampen the protein crystal growth. To date the mechanism is not clear. However, it was generally proposed that the magnetic field may dampen the convection in the solution, resulting in a reduced crystal growth rate and possibly a good crystal quality, similar to the case of protein crystal growth in space. To understand the mechanism of the magnetic field effect on protein crystal growth, further explorations on the magnetic field effect on protein solution, on the processes of crystal growth and dissolution, and on different crystallization (solution) systems, should be valuable. In this paper we present our recent efforts to study magnetic field effects on the dissolution processes of tetragonal lysozyme crystals under a strong magnetic field. A layer of oriented tetragonal lysozyme crystals was prepared under a temperature gradient and magnetic field, after that the crystals were dissolved by increasing the temperature of the solution. The lysozyme molecules will diffuse upwards due to the steep concentration gradient at the lower side of the cell caused by the dissolution. The evolution of the concentration in the solution was measured in-situ using a Mach-Zehnder interferometer. The results confirmed that the dissolution process of the crystals was slowed by the magnetic field. Judging from the concentration evolution versus time at different positions in the solution, we concluded that the apparent diffusion coefficient of lysozyme molecules was decreased by the magnetic field. The results were discussed using a suspended crystal model in the initial dissolution stage. © 2003 COSPAR. Published by Elsevier Ltd. All rights reserved.

The diffusivity of lysozyme molecules was deduced to decrease under a magnetic field, based on the discovery of magnetic damping of the dissolution process using a Mach-Zehnder interferometer. In the same experiment, a redistribution of the concentration before crystal growth was also found.

Temperature dependence of interdiffusion coefficient of In-Sn was measured by a capillary method under a static magnetic field. The obtained diffusion coefficient data agreed well with data measured in microgravity environment at a lower temperature range. The application of static magnetic field could be a good substitute method for accurate measurement of diffusion coefficients in substitution for utilization of the microgravity environment.

The step kinetic coefficient of the GaP/GaP(1 1 1)B surface in liquid-phase epitaxial growth was estimated by means of an in situ observation technique using a near-infrared microscopic interferometer under a static magnetic field of 4T. Morphological stability of the solid/liquid interface during the growth was evaluated based on a linear perturbational approach taking into account the step kinetic coefficient. The estimated value of the macrostep wavelength agreed well with the measured one. © 2002 Elsevier Science B.V. All rights reserved.

Kinetic coefficient on a solid/liquid interface in liquid-phase epitaxial growth of GaP/GaP(1 1 1)B was measured by an in situ observation technique using a near-infrared microscopic interferometer under a static magnetic field of 4 T. The morphological stability of the interface during the growth was quantitatively evaluated based on a linear perturbational approach taking account of the kinetic coefficient. The calculated value of the macrostep wavelength agreed well with the measured one. © 2002 Elsevier Science B.V. All rights reserved.

This paper reports concentration measurement of protein solution under a strong magnetic field. The effect of the magnetic field on the time evolution of the concentration during the growth process of tetragonal crystal of lysozyme was investigated by interferometry. A Mach-Zehnder interferometer was applied to a superconducting magnet for the first time to in situ study the concentration profile beyond the solid/liquid interface during the crystal growth. Results showed that during the growth process, decrease in the lysozyme concentration under homogeneous magnetic field was slowed down as compared with those without magnetic field. It was postulated that solutal convection during the crystal growth might have been influenced by the magnetic field. However, study of the convection under different magnetic fields indicated little effect of the magnetic field on the convection. Furthermore, after checking the solubility under magnetic field, we found that there was little effect of magnetic field on the solubility. Further investigation with respect to the growth and dissolution processes and mechanisms under magnetic field are in progress. © 2001 Elsevier Science B.V.

A formulation of the relation between static magnetic induction and Reynolds number in liquid, for vertical Bridgman and LPE growth processes of semiconductors in axial static magnetic field was derived based on a scaling analysis, and the validity of the estimation was experimentally investigated. The calculated values of the effective segregation coefficients for Ga-doped Ge and Pb1-xSnx Te crystals grown by the Bridgman method agreed well with the experimentally measured ones from 0 to 6 T of the magnetic induction. In the case of LPE growth on GaP(111)B, nearly diffusion-controlled condition in the liquid was achieved at 6 T. It was shown by in situ observation using a near-infrared (NIR) microscopic interferometer that the static magnetic reduced the LPE growth rate, and as a result, suppressed appearance of macro-steps and hillocks.