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Presented here are the observations and interpretations from a comprehensive analysis of 16 representative particles returned from the C-type asteroid Ryugu by the Hayabusa2 mission. On average Ryugu particles consist of 50% phyllosilicate matrix, 41% porosity and 9% minor phases, including organic matter. The abundances of 70 elements from the particles are in close agreement with those of CI chondrites. Bulk Ryugu particles show higher δ18O, Δ17O, and ε54Cr values than CI chondrites. As such, Ryugu sampled the most primitive and least-thermally processed protosolar nebula reservoirs. Such a finding is consistent with multi-scale H-C-N isotopic compositions that are compatible with an origin for Ryugu organic matter within both the protosolar nebula and the interstellar medium. The analytical data obtained here, suggests that complex soluble organic matter formed during aqueous alteration on the Ryugu progenitor planetesimal (several 10’s of km)

We demonstrated numerical simulations of impurity-induced crystal growth hysteresis in spiral growth. The numerical scheme combines two different methods: the phase-field method for step dynamics and the Monte Carlo method for random impurity adsorption. We manually changed the supersaturation (down and up) and repeated this cycle to monitor the time variation of the normal growth rate. We found that the growth rate suddenly drops to almost zero as the supersaturation decreases, and it swiftly recovers as the supersaturation subsequently increases. We confirmed that the critical supersaturation at which the growth rate recovered is distinguishably larger than that at which the crystal growth stopped. The critical supersaturations were found to be consistent with those predicted by the mean field theory for spiral growth if the period of the down-and-up cycle of supersaturation was chosen appropriately. We also applied the mean field theory to the observed hysteresis loops to evaluate some physical quantit...

A comprehensive geochemical study of the Chelyabinsk meteorite reveals further details regarding its history of impact-related fragmentation and melting, and later aqueous alteration, during its transit toward Earth. We support an 930Ma age obtained by Ar-Ar method (Beard et al., 2014) for the impact-related melting, based on Rb-Sr isotope analyses of a melt domain. An irregularly shaped olivine with a distinct O isotope composition in a melt domain appears to be a fragment of a silicate-rich impactor. Hydrogen and Li concentrations and isotopic compositions, textures of Fe oxyhydroxides, and the presence of organic materials located in fractures, are together consistent with aqueous alteration, and this alteration could have pre-dated interaction with the Earth's atmosphere. As one model, we suggest that hypervelocity capture of the impact-related debris by a comet nucleus could have led to shock-wave-induced supercritical aqueous fluids dissolving the silicate, metallic, and organic matter, with later ice sublimation yielding a rocky rubble pile sampled by the meteorite. © 2019 The Japan Academy.

The Japanese Hayabusa2 mission has revealed in detail the physical characteristics of the C-type asteroid 162173 Ryugu, in particular, its spinning top-shaped rubble pile structure [1] and the potentially extremely high organic content [2,3]. A widely-accepted formation scenario for Ryugu is catastrophic collision between larger asteroids and the subsequent slow gravitational accumulation of collisional debris [4,5]. However, the collisional re-accumulation scenario does not explain the origin of the abundant organic matter. An alternative scenario is that Ryugu is an extinct comet, which lost its icy components [2,6,3]. Here, the sublimation of water ice from a uniform porous cometary nucleus was numerically simulated until the refractory components, such as silicate rocks and organic matter were left behind as evaporative residues. Such a process represents the transformation from a comet to an asteroid. The spin-up related to the shrinking nucleus, associated with the water ice sublimation, was also calculated. The result of the calculation indicates that the cometary origin scenario can quantitatively account for all the features of Ryugu discussed above. We conclude that organic-rich spinning top-shaped rubble pile asteroids, such as Ryugu, are comet-asteroid transition objects or extinct comets.

This paper presents the outline of a practical course on computer simulation that will be given at the 16th International Summer School on Crystal Growth (ISSCG-16). The aim of this course is to understand crystal growth processes from the molecular level to the macroscopic level through computer simulations. We will mainly study molecular-scale crystal growth and nucleation processes by using molecular dynamics simulations and macroscopic growth processes at crystal surfaces by using phase field simulations.

Growth hysteresis is one of the remarkable phenomena of crystal growth induced by impurities; namely, the growth rates of crystal take different values between when supersaturation is decreased and is increased. The appearance of hysteresis has been explained on the basis of the mean field theory, in which the physical quantities such as step velocity, step interval, and density of impurities adsorbed on the crystal surface are averaged over space and time. Here, we propose a new method for the numerical simulation of step dynamics with impurity adsorption–desorption kinetics on a growing crystal surface. We numerically reproduce the growth hysteresis in a more realistic situation, in which the physical quantities fluctuate. The calculated hysteresis agrees with the prediction of the mean field theory. We have also found that the supersaturation should be changed within a period that is similar to the impurity adsorption time scale or slightly longer in order to observe obvious growth hysteresis. Measurem...

This paper presents an extension of a classical model of the crystal growth, the Burton–Cabrera–Frank (BCF) model, to a system that includes impurity molecules and discusses the formulation of the amount of the impurity uptake into the crystal as a partition coefficient. The BCF model considers the following surface processes of host molecules: adsorption from a solution to a terrace, desorption from the terrace to the solution, surface diffusion on the terrace, incorporation at a step edge, and release from the step edge to the terrace. The above-mentioned processes have been formulated not only for the host molecules but also for the impurity molecules (Miura, 2020). In this paper, the author analytically solves the previous model and derives an analytic formula for the partition coefficient as a ratio of the uptake of the impurity molecule to that of the host molecule into the crystal. The dependence of the partition coefficient on supersaturation is systematically investigated. The analytic formula is applied to the data obtained in the experiments of protein crystal growth to discuss the behavior of impurity molecules on the growing crystal surface. This model provides a theoretical framework for eliciting quantitative data from the crystal growth experiments on impurity partitioning.

We examined the excitations of planetesimals caused by the resonances of a giant planet in a protoplanetary gas disk. The highly excited planetesimals generate bow shocks, the mechanism of which results in chondrule formation, crystallization of silicate dust, and evaporation of icy planetesimals. The planetesimals beyond 2:1 resonance migrate owing to the gas drag and obtain the maximum eccentricity around 3:1 resonance, which is located at approximately half the planetary distance. The eccentricity depends on the parameters of the planetesimals and the Jovian planet, such as size and location, and the gas density of the disk. The maximum relative velocity of a 100 km sized planetesimal with respect to the gas disk reaches up to ~12 km s−1 in the case of Jupiter owing to secular resonance, which occurs because of the disk's gravity. We find that if a Jovian-mass planet is located within 10 au, the planetesimals larger than 100 km gain sufficient velocity to cause the melting of chondrule precursors and crystallization of the silicate. The maximum velocity is higher for large planetesimals and eccentric planets. Planetesimals are trapped temporarily in the resonances and continue to have high speed over 1 Myr after the formation of a Jovian planet. This duration fits into the timescale of chondrule formation suggested by the isotopic data. The evaporation of icy planetesimals occurs when a Jovian planet is located within 15 au. This mechanism can be a new indicator of planet formation in exosystems if some molecules ejected from icy planetesimals are detected.

We propose a simple formulation of the phase-field model for a stoichiometric compound growing in a binary liquid. In previous models, chemical free energies of stoichiometric compounds have been approximated by parabolic functions of composition; however, the curvature has been determined arbitrarily in spite of the fact that the stoichiometric composition was undesirably modified depending on the curvature. To avoid this uncertainty, we supposed that the chemical free energy of the stoichiometric compound is represented by a single value at a given temperature and derived the phase-field equations without the parabolic free-energy approximation. The phase mobility was derived both for diffusion- and interface-controlled solidification based on a thin interface limit analysis. We carried out numerical simulations of one-dimensional calculations both in diffusion-controlled and interface-controlled cases and found that the growth velocities agreed with the analytic predictions. We also examined two-dimensional solidification of a circular crystal and confirmed that the equilibrium state was shifted, as suggested by the Gibbs-Thomson effect. This study is an important step for phase-field modeling that includes stoichiometric compounds with their accurate thermodynamic properties.

The normal growth rates R and apparent step velocities (lateral growth rates of a spiral hillock) V of tetragonal hen egg-white lysozyme (HEWL) crystals were for the first time measured by Michelson interferometry in the international space station (as part of the NanoStep project) using commercialized HEWL samples containing 1.5% impurities. A significant increase in V under microgravity was confirmed compared to step velocities Vstep on the ground, while a decrease in R was also confirmed compared to that in the purified solution under microgravity as expected. Because of exact measurement of growth rates, kinetic analyses of R were conducted as a function of supersaturation, σ (σ ≡ ln(C/Ce), where C is the concentration; Ce is the solubility), using a spiral growth model and a two-dimensional (2D) nucleation growth model. For both models over a wide range of σ, R in the impure solution was significantly lower than that in the purified solution. The degree of the suppression of impurity effects was also...

The step pinning hypothesis is widely accepted as an explanation for the inhabitation of crystal growth by impurity molecules. This hypothesis enables us to evaluate the average step velocity and the critical impurity density above which no step can move on the crystal surface polluted by impurities. The average step velocity and the critical impurity density were obtained analytically in some literature; however, they have not been verified with other approaches. Here, we propose a new method for the numerical simulation of the step pinning by impurities in the framework of a phase-field technique and report a quantitative study on the average step velocity and critical impurity density for the first time. Our results clarify the limitations of the physical assumptions of the analytical formulas and their applications. Our phase-field method provides a good numerical tool for the quantitative investigation of the effect of impurities on step dynamics if step pinning works as described in the Cabrera–Verm...

We propose a new formulation for numerically simulating step dynamics on growing crystal surfaces in the framework of a phase-field technique. The step advancement rate is proportional to a supersaturation at the crystal surface when the growth units in the ambient phase are integrated to the step front directly (direct integration hypothesis). We conduct numerical simulations of some standard step dynamics problems: the advancement of a straight step, the growth or dissolution of a two-dimensional island, and the vertical growth of the crystal surface due to single or multiple screw dislocations. During evaluations, our phase-field model accurately calculated the rate of advancement of a straight step for various supersaturations. The calculated time variation of the radius of the two-dimensional island showed good agreement with the exact solution. The vertical growth rate due to screw dislocations qualitatively agreed with the predictions of the classical theory of Burton, Cabrera, and Frank. Our simpl...

Chiral symmetry breaking during the chiral crystallization from a sodium chlorate (NaClO3) aqueous solution is an intriguing phenomenon because it provides insights into the prebiotic process of biohomochirality. However, a mechanism of the emergence and amplification of chirality remains controversial, especially for crystallization from highly supersaturated solution, and one of the hypotheses proposed before is a transition toward the homochiral state during the early stages of crystallization. In this contribution, we directly examined the early stage of crystallization by in situ polarized-light microscopy. The observation revealed that achiral crystals, which appear prior to the formation of chiral crystals, transform to the chiral crystal through two kinds of polymorphic transformations: (1) martensitic transformation (MT) and (2) solution-mediated phase transition (SMPT). The SMPT is remarkably facilitated by contact with a chiral crystal. Notably, the resulting enantiomorph through contact-facili...

The solubility of the metastable achiral monoclinic phase in NaClO 3 crystallization from an aqueous solution, which appears prior to the nucleation of chiral crystals, was successfully measured in the range from 10 °C to 23 °C. Antisolvent crystallization method was used to obtain metastable crystals for the measurement. The solubility was determined to be about 1.6 times higher than that of the chiral stable cubic phase by observing growth or dissolution of the crystal in aqueous solution at the temperature and concentration of which is predetermined.

The two-dimensional (2D) distributions of surface supersaturation of sodium chlorate crystals with and without solutal convection have been measured by means of a multidirectional interferometry (MDI) technique coupled with the principles of three-dimensional (3D) computer tomography. When solutal convection was present over a top face, the supersaturation at the center of the face was depleted by a factor of >0.9 with reference to the value at the edges of the crystal. When the convection was suppressed using an upside-down geometry, the depletion of supersaturation at the center of the face was much smaller

It is thought that protoplanets formed in protoplanetary disks excite the orbital motion of the surrounding planetesimals, and the bow shocks caused by the highly excited planetesimals heat their icy component evaporating into gas. We have performed model calculations to study the evolution of molecular abundances of the evaporated icy component, which suggests sulfur-bearing molecules can be good tracers of icy planetesimal evaporation. Here we report the result of our ALMA observations of sulfur-bearing molecules towards protoplanetary disks. The lines were undetected but the obtained upper limits of the line fluxes and our model calculations give upper limits of the fractional abundances of x(H2S) < 10−11 and x(SO) < 10−10 in the outer disk. These results are consistent with the molecular abundances in comets in our Solar system.

Highly forsteritic olivine (Fo: 99.2–99.7) in the Kaba meteorite emits bright cathodoluminescence (CL). CL spectra of red luminescent forsterite grains have two broad emission bands at approximately 630 nm (impurity center of divalent Mn ions) in the red region and above 700 nm (trivalent Cr ions) in the red–IR region. The cores of the grains show CL blue luminescence giving a characteristic broad band emission at 400 nm, also associated with minor red emissions related to Mn and Cr ions. CL color variation of Kaba forsterite is attributed to structural defects. Electron probe microanalyzer (EPMA) analysis shows concentrations of Ca, Al, and Ti in the center of the forsterite grain. The migration of diffusible ions of Mn, Cr, and Fe to the rim of the Kaba meteoritic forsterite was controlled by the hydrothermal alteration at relatively low temperature (estimated at about 250 °C), while Ca and Al ions might still lie in the core. A very unusual phase of FeO (wustite) was also observed, which may be a terrestrial alteration product of FeNi-metal.

Chiral symmetry breaking in NaClO3 crystallization from an aqueous solution with perturbations has been of great interest. To understand the mechanism, several models focusing on the early stage of the crystallization have been proposed. However, they are ambiguous because the early stage has been barely explored directly. Here, we investigate the early stages of the crystallization process driven by droplet evaporation using a combination of direct in situ microscopic observations and cryogenic single-crystal XRD experiments. We demonstrate that an achiral crystal having P21/a symmetry, which is newly discovered for a solution growth, first appears in the droplet and then transforms into the chiral crystals. Additionally, determination of the lattice constants by XRD experiments (a = 8.42 A, b = 5.26 A, c = 6.70 A, β = 109.71°) revealed that the achiral phase should be identical to Phase III (a = 8.78 A, b = 5.17 A, c = 6.83 A, β = 110°), which is a high-temperature phase from a melt growth of NaClO3. We...

The present study investigated the effect of nicotine exposure on gustatory plasticity in the nematode Caenorhabditis elegans . The chemotactic response of wild-type N2 nematodes pre-exposed to 100 mM NaCl with 3.0 mM nicotine was almost the same as that of mock-conditioned nematodes unexposed to NaCl; however, the response of N2 nematodes pre-exposed to NaCl without nicotine was significantly lower than that of mock-conditioned nematodes. These results indicate that gustatory plasticity is inhibited by acute nicotine exposure. Inhibition of gustatory plasticity was observed when cat-2 mutants with a defect in dopamine biosynthesis were pre-exposed to NaCl with 3.0 mM nicotine. Acute nicotine exposure did not cause inhibition of gustatory plasticity in bas-1 mutants, which had defects in both serotonin and dopamine secretion, and tph-1 mutants, which had a defect in serotonin secretion only. However, inhibition of gustatory plasticity was observed when bas-1 and tph-1 mutants were maintained on a growth plate that included serotonin. These results suggest that serotonin signaling plays an essential role in the modulation of the acute effects of nicotine.

We proposed a simple physical model of growth hysteresis and oscillatory growth in a crystallization system with impurities. The model is based on two fundamental mechanisms: (i) removal of impurities adsorbed on the growing crystal surface by step advancement and (ii) retardation of step advancement by the adsorbed impurities (the pinning mechanism). We found that the coupling of these two mechanisms causes a cyclic feedback on the kinetics of impurity adsorption and step advancement. We revealed a growth hysteresis on the step velocity, namely, the history of the step velocity when the supersaturation is decreased is different from that when the supersaturation is increased. The critical supersaturation at which the growth hysteresis appears is given by definite physical parameters such as step free energy, number density of the adsorbed impurities, and time scale of impurity adsorption. The feedback loop also results in the oscillatory growth of crystals when the transportation of constituent molecules...

We proposed a new anisotropy function of kinetic coefficient for the phase-field simulations in two-dimension. The anisotropy function has minima at arbitrary polar angles. We carried out phase-field simulations of solidification of binary alloy with the new anisotropy function and found that the calculated growth form agreed with the kinetic Wulff shape, which is the exact solution determined by the anisotropy function. With the new anisotropy function, the kinetic Wulff shape is not necessary to be regular polygons but can be an arbitrary shape with any face angles. In addition, we introduced a curvature parameter with the aim of optimizing the anisotropy function. We found that the kinetic Wulff shape with flat facets was reproduced when the curvature parameter was at a standard value of about 20. The optimization based on the curvature parameter is applicable to other anisotropy functions. We concluded that our anisotropy function and the concept of the curvature parameter give us a great opportunity to simulate more general shapes of crystals.

We carry out phase field simulations to study properties of the comblike step patterns induced by an adatom source. When an adatom source advances right in front of a step, step wandering is caused by the asymmetry of the surface diffusion field and small protrusions are formed. If the velocity of the source V_{p} is smaller than a critical value V_{p}^{c}, the protrusions follow the adatom source with coarsening of the step pattern, and a regular comblike pattern with finger-like protrusions is formed. With a sufficiently small V_{p}, the gap of the supersaturation is large at the adatom source. Since the period of protrusions, Λ, decreases with increasing V_{p}, the coarsening of step pattern is irrelevant for the protrusions to catch up with the adatom source. Near V_{p}^{c}, the gap of the supersaturation at the adatom source is small. Taking account of the increase in Λ with increasing V_{p}, the coarsening of the step pattern is essential for the protrusions to follow the adatom source.

To clarify the growth mechanism of a protein crystal, it is essential to measure its growth rate with respect to the supersaturation. We developed a compartment (growth cell) for measuring the growth rate (

We examined the homogeneous condensation of thermally evaporated manganese vapor in an atmosphere of argon gas and determined the temperature and concentration during homogeneous nucleation in the vapor phase by using a Mach–Zehnder type interferometer. Condensation occurred at 660–785 K below the equilibrium temperature and the degree of supersaturation was as high as ∼5 × 104. Using the condensation temperature and size of the condensed particles, which were measured by transmission electron microscopy, we determined the surface free energy and sticking coefficient of Mn at 1106 ± 50 K to be 1.55 ± 0.10 J/m2 and 0.39–0.20+0.39, respectively, by classical nucleation theory (CNT) and 1.57 ± 0.35 J/m2 and 0.42–0.21+0.42, respectively, by a semiphenomenological theory (SP). The nucleation theories predict that the critical nucleus contains only three and six atoms for CNT and SP, respectively, which are fewer than the number of atoms in a unit cell of Mn. This suggests that the polymorphic form of manganese...

Cathodoluminescence (CL) of laboratory forsterite chondrules has been characterized to clarify the formation process of chondrules and related mechanism of the crystal growth in a supercooled melt. Color CL image of the experimentally grown forsterite exhibits significant blue luminescence in the main branches of the interior structure of lab-chondrule, which reflects to the anisotropy of crystallization. A new CL band centered at 450–525 nm (2.76–2.36 eV) in blue to green region might be assigned to a microdefect-related center, which is a diagnostic peak for the forsterite that was formed due to the rapid growth as high as ∼10 mm/s or higher from a supercooled melt.

Nucleation of amorphous calcium phosphate (ACP) and its phase transformation with a decrease in solution pH were investigated at a constant temperature of 32 °C. A solution containing a mixture of CaCl 2 and KH 2 PO 4 was prepared (initial pH=7.7), and a drop was sampled at a constant interval to observe the morphological evolution of the precipitates that formed in the solution. A gel-like solution structure formed immediately after mixing and contained a small amount of sea-urchin-like ACP spherulites (3–20 μm in size). These spherulites consisted of 1.5–10-μm-long flexible needles that formed simultaneously with numerous ACP spherical particles. They first transformed into β-tri calcium phosphate-like material (called “pseudo β-TCP”) and then into single crystals of octacalcium phosphate (OCP) without dissolution. The flexible needles in the spherulites changed into blade springs, then into flexible plates, and finally into rigid plates during the transformation. The OCP structure appeared in the pseudo β-TCP plates and gradually substituted for the β-TCP structure over time. The macroscopic spherulite morphology of the initial ACP remained unchanged during the phase transformation, suggesting that OCP is a pseudomorph of ACP. This feature was observed only when the ACP spherulites formed in the initial solution. Fiber-like aggregates consisting of β-TCP single crystals nucleated around the ACP spherical particles and grew over time. They survived until the final stage of the reaction, and OCP polycrystals formed in the mixture of β-TCP and ACP spheres. The OCP polycrystals gradually substituted for the ACP spheres without phase transformation of β-TCP into OCP.

To investigate the homogeneous nucleation and growth process of nanoparticles in vapor phase, interferometric observation was attempted for the first time to the gas evaporation method, which has been a commonly accepted physical production method of nanoparticles. Tungsten oxide was evaporated by electrical heating of a tungsten wire in a mixture gas of Ar and O-2. WO3 nanoparticles were formed via homogeneous nucleation and growth during a gas cools following a thermal convection produced by the evaporation source. The degree of supersaturation for nucleation was extremely high, 6.6 x 10(6), which was determined from the interferogram. Surface free energy of WO3 at 1100 K was calculated based on the classical nucleation theory and was 1.38 x 10(3) erg cm(-2), which is within the reported values. A part of the difference between actual formation rate of produced nanoparticles, which were determined based on a transmission electron microscope, and calculated values based on the classical nucleation theory were well explained if we adopt the idea of coalescence growth. (C) 2011 Elsevier B.V. All rights reserved.

In the present study, we found that the ice nucleation-active bacteria Xanthomonas campestris significantly altered anisotropic ice growth rate. Results of ice growth experiments in the presence of X. campestris showed that this bacterium decreased the ice crystal growth rate in the c-axis, whereas it increased growth rates in directions normal to the c-axis. These results indicate that these alterations in anisotropic growth rate are the result of selective binding of bacterial ice-nucleating proteins along the {0 0 0 1} basal plane.

Hot H 2 O jet evolved by the exothermic reaction of H 2 with O 2 on a Pt-dispersed ZrO 2 catalyst was employed for gas-phase hydrolysis of dimethyl zinc to fabricate thin ZnO films. The X-ray diffraction pattern and photoluminescence spectra showed that the ZnO epilayers directly grown on a-sapphire substrate at 873 K had a defect free crystal structure close to a single crystal. The as-grown ZnO epilayers exhibited average transparency higher than 90% in the visible and infrared regions (400–2000 nm). The epilayers had high electron mobilities of 140–170 cm 2 V −1 s −1 and low residual electron concentrations of 1.7–6×10 17 cm −3 that are significantly better than those for ZnO films so far reported by conventional chemical vapor deposition and any other energy-consuming physical method such as pulse laser deposition and molecular beam epitaxy. The present method uses the chemical energy from only H 2 and O 2 , which is energy-saving and ecologically friendly, while it is superior in high-quality ZnO fabrication. It is also pointed out that the method raises unlimited possibilities for a wide range of the fabrication of high-quality metal oxide epilayers, because of the availability for various volatile alkyl metals.

We carried out three-dimensional hydrodynamics simulations of the disruption of a partially-molten dust particle exposed to high-speed gas flow to examine the compound chondrule formation due to mutual collisions between the fragments (fragment-collision model; [Miura, H., Yasuda, S., Nakamoto, T., 2008a. Icarus194, 811–821]). In the shock-wave heating model, which is one of the most plausible models for chondrule formation, the gas friction heats and melts the surface of the cm-sized dust particle (parent particle) and then the strong gas ram pressure causes the disruption of the molten surface layer. The hydrodynamics simulation shows details of the disruptive motion of the molten surface, production of many fragments and their trajectories parting from the parent particle, and mutual collisions among them. In our simulation, we identified 32 isolated fragments extracted from the parent particle. The size distribution of the fragments was similar to that obtained from the aerodynamic experiment in which a liquid layer was attached to a solid core and it was exposed to a gas flow. We detected 12 collisions between the fragments, which may result in the compound chondrule formation. We also analyzed the paths of all the fragments in detail and found the importance of the shadow effect in which a fragment extracted later blocks the gas flow toward a fragment extracted earlier. We examined the collision velocity and impact parameter of each collision and found that 11 collisions should result in coalescence. It means that the ratio of coalescent bodies to single bodies formed in this disruption of a parent particle is R coa = 11 / ( 32 - 11 ) = 0.52 . We concluded that compound chondrule formation can occur just after the disruption of a cm-sized molten dust particle in shock-wave heating.

Aims: The objective of the present study was to investigate the differences in frontal lobe function between violent and nonviolent male adolescents with conduct disorder. Methods: A total of 309 male adolescents who had been admitted to the Nagoya Juvenile Classification Home participated. The participants were divided into two groups, a violent group composed of individuals who had committed violence against others, and a nonviolent group. The subjects were given the Wisconsin card sorting test (Keio version: KWCST) and the Iowa Gambling task. The presence of violent cases was analyzed in terms of age, family history (crime, drug abuse/dependence, alcohol-related disorder, and psychiatric treatment), experience of being abused by their parents or by the persons who were responsible for raising them, as well as categories achieved (CA) of KWCST (≤4, >4) and total selection of disadvantage cards of Iowa Gambling task (≥50

The origin of three-dimensional shapes of chondrules is an important information to identify their formation mechanism in the early solar nebula. The measurement of their shapes by using X-ray computed topography suggested that they are usually close to perfect spheres, however, some of them have rugby-ball-like (prolate) shapes [Tsuchiyama, A., Shigeyoshi, R., Kawabata, T., Nakano, T., Uesugi, K., Shirono, S., 2003. Lunar Planet. Sci. 34, 1271–1272]. We considered that the prolate shapes reflect the deformations of chondrule precursor dust particles when they are heated and melted in the high velocity gas flow. In order to reveal the origin of chondrule shapes, we carried out the three-dimensional hydrodynamics simulations of a rotating molten chondrule exposed to the gas flow in the framework of the shock-wave heating model for chondrule formation. We adopted the gas ram pressure acting on the chondrule surface of p fm = 10 4 dyn cm −2 in a typical shock wave. Considering that the chondrule precursor dust particle has an irregular shape before melting, the ram pressure causes a net torque to rotate the particle. The estimated angular velocity is ω f = 140 rad s −1 for the precursor radius of r 0 = 1 mm , though it has a different value depending on the irregularity of the shape. In addition, the rotation axis is likely to be perpendicular to the direction of the gas flow. Our calculations showed that the rotating molten chondrule elongates along the rotation axis, in contrast, shrinks perpendicularly to it. It is a prolate shape. The reason why the molten chondrule is deformed to a prolate shape was clearly discussed. Our study gives a complementary constraint for chondrule formation mechanisms, comparing with conventional chemical analyses and dynamic crystallization experiments that have mainly constrained the thermal evolutions of chondrules.

We propose a new scenario for compound chondrule formation named as "fragment-collision model," in the framework of the shock-wave heating model. A molten cm-sized dust particle (parent) is disrupted in the high-velocity gas flow. The extracted fragments (ejectors) are scattered behind the parent and the mutual collisions between them will occur. We modeled the disruption event by analytic considerations in order to estimate the probability of the mutual collisions assuming that all ejectors have the same radius. We found that the estimated collision probability, which is the probability of collisions experienced by an ejector in one disruption event, can account for the observed fraction of compound chondrules. In addition, the model predictions are qualitatively consistent with other observational data (oxygen isotopic composition, textural types, and size ratios of constituents). Based on these results, we concluded that this new model can be one of the strongest candidates for the compound chondrule formation. It should be noted that all collisions do not necessarily lead to the compound chondrule formation. The formation efficiency and the future works which should be investigated in the forthcoming paper are also discussed., Comment: Accepted for publication in Icarus, 34 pages, including 8 figures

Epitaxial growth of SiC on SOI substrates using a hot-mesh chemical vapor deposition (CVD) technique was investigated. This technique utilizes a catalytic reaction involving hot tungsten wires arranged in a mesh structure. Using this hot-mesh CVD method, SiC epitaxial growth on SOI substrates with a thin top Si layer was realized without formation of voids, which form readily in the thin Si top layer at temperatures above 800 °C. The SiC film grown on an SOI structure exhibited a large gage factor (GF) of − 27, which is approximately the same as that (GF = − 31.8) of a SiC epitaxial film on Si(100) grown at 1360 °C using atmospheric pressure CVD.

Computed tomography (CT)-guided thoracic sympathetic blockade with ethanol was performed while monitoring sympathetic nerve activity, with an alternating current (AC) galvanic skin reflex (GSR) monitor, in a patient with palmar hyperhidrosis in whom endoscopic thoracic sympathectomy was impossible because of pleural adhesion. Sweating was suppressed after the thoracic sympathetic blockade, and the monitor showed a significant increase in skin resistance. The effect of sympathetic blockade could be evaluated directly and in real time using a GSR monitor.

The normal growth rates of the {110} faces of tetragonal hen egg-white lysozyme crystals, R, were measured as a function of the supersaturation σ parameter using a reflection type interferometer under μG at the International Space Station (NanoStep Project). Since water slightly evaporated from in situ observation cells during a long-term space station experiment for several months, equilibrium temperature T(e) changed, and the actual σ, however, significantly increased mainly due to the increase in salt concentration C(s). To correct σ, the actual C(s) and protein concentration C(p), which correctly represent the measured T(e) value in space, were first calculated. Second, a new solubility curve with the corrected C(s) was plotted. Finally, the revised σ was obtained from the new solubility curve. This correction method successfully revealed that the 2.8% water was evaporated from the solution, leading to 2.8% increase in the C(s) and C(p) of the solution.

Pattern formation of a step on a growing crystal surface induced by a straight line source of atoms, which is escaping from the step at a velocity ${V}_{\mathrm{p}}$, is studied with the use of a phase field model. From a straight step, fluctuations of the most unstable wavelength ${\ensuremath{\lambda}}_{\mathrm{max}}$ grow. Competition of intrusions leads to coarsening of the pattern, and survived intrusions grow exponentially. With sufficient strength of the crystal anisotropy, a regular comblike pattern appears. This peculiar step pattern is similar to that observed on a Ga-deposited Si(111) surface. The final period of the intrusions, $\ensuremath{\Lambda}$, is determined when the exponential growth ends. The period depends on the strength ${F}_{u}$ of a current noise in diffusion as $\ensuremath{\Lambda}\ensuremath{\sim}{\ensuremath{\lambda}}_{\mathrm{max}}|ln{F}_{u}|$: such a logarithmic dependence is confirmed for the first time. A nonmonotonic ${V}_{\mathrm{p}}$ dependence of $\ensuremath{\Lambda}$ indicates that the comblike pattern with a small ${V}_{\mathrm{p}}$ is related to an unstable growth mode of the free needle growth in a channel. The pattern is stabilized by the guiding linear source.

We examined partially molten dust particles that have a solid core and a surrounding liquid mantle, and estimated the maximal size of chondrules in a framework of the shock wave heating model for chondrule formation. First, we examined the dynamics of the liquid mantle by analytically solving the hydrodynamics equations for a core-mantle structure via a linear approximation. We obtained the deformation, internal flow, pressure distribution in the liquid mantle, and the force acting on the solid core. Using these results, we estimated conditions in which liquid mantle is stripped off from the solid core. We found that when the particle radius is larger than about 1-2 mm, the stripping is expected to take place before the entire dust particle melts. So chondrules larger than about 1-2 mm are not likely to be formed by the shock wave heating mechanism. Also, we found that the stripping of the liquid mantle is more likely to occur than the fission of totally molten particles. Therefore, the maximal size of chondrules may be determined by the stripping of the liquid mantle from the partially molten dust particles in the shock waves. This maximal size is consistent with the sizes of natural chondrules.

Chondrule formation due to the shock wave heating of dust particles with a wide variety of shock properties are examined. We numerically simulate the steady postshock region in a framework of one-dimensional hydrodynamics, taking into account many of the physical and chemical processes that determine the properties of the region, especially nonequilibrium chemical reactions of gas species. We mainly focus on the dust particle shrinkage due to the evaporation in the postshock hot gas and the precursor size conditions for chondrule formation. We find that the small precursors whose radii are smaller than a critical value, a pre min , cannot form chondrules because they evaporate away completely in the postshock region. The minimum value of a pre min is about 10 μm, though it depends on the shock speed and the preshock gas density. Furthermore, we demonstrate the chondrule size distributions which are formed through the shock-wave heating. These results indicate that the shock-wave heating model can be regarded as a strong candidate for the mechanism of chondrule formation.

Gasoline has high inflammability and combustibility. Therefore, when gasoline is spilled on a floor, it may form a great flame and cause a big fire. In this case, it is thought that the spill area influences the flame height. In this study, the authors carried out combustion tests of gasoline and kerosene spilt on a wooden floor coated with a galvanized iron sheet. Liquid fuel was spilled in a circle surrounded by a clay fence. The spill area was determined by changing the radius of the fence. We placed heat flux meters in and around the flame and measured heat flux and radiation heat from the flame. We measured the temperature of the flame by using K-type thermocouples. The flame behavior was recorded on video and mean flame height was measured. Furthermore, we measured the weight loss rate of gasoline and obtained the heat release rate. Conclusions are as follows: (1) When the radius of the spill area was 0.8 m, the mean flame tip height reached 4.7 m. The flame height was higher as the spill area increased in size, but the quantity of the gasoline spill was not a factor. (2) The mean flame tip height was calculated using the heat release rate measured in the combustion tests. The calculated value agreed approximately with the experimental value. (3) When the radius of the spill area was 0.8 m, a high temperature region more than 400°C spread to a 3 m height from the floor and the average heat flux at 3.5 m height had the highest value of 74.7 kW/m2. (4) The radiant heat at a distance of 50 cm from the apparent flame surface was so high, 20-30 kW/m2, it was found that there was ignitability to combustibles within this distance.

From 1984 to 1999, the authors treated 64 cases of fracture of the scaphoid in children. Causes of injury were sports (n = 27), punching game machines or fighting (n = 22), and traffic accident or other trauma (n = 15). Most (46 cases) were nonunion cases. Eighteen cases were acute. Cast immobilization was performed in 10 acute cases and two nonunion cases. Screw fixation was performed in 52 cases, including 35 cases of bone graft. In 10 of these operated cases, freehand screw insertion was used. Ultimately, good bony fusion was achieved in all cases, but in two nonunion cases a secondary bone graft was necessary. Functional results in all cases were acceptable. A major problem is that children are not brought to clinics immediately after injury, so the percentage of nonunion is high.

A shock-wave heating model is one of the possible models for chondrule formation. We examine, within the framework of a shock-wave heating model, the effects of evaporation on the heating of chondrule precursor particles and the stability of their molten state in the postshock flow. We numerically simulate the heating process in the flow taking into account evaporation. We find that the melting criterion and the minimum radius criterion do not change significantly. However, if the latent heat cooling due to the evaporation dominates the radiative cooling from the precursor particle, the peak temperature of the precursor particle is suppressed by a few hundred Kelvins. We also find that the total gas pressure (ram plus static) acting on the precursor particle exceeds the vapor pressure of the molten precursor particle. Therefore, it is possible to form chondrules in the shock-wave heating model if the precursor temperature increases up to the melting point.