On the origin and evolution of the asteroid Ryugu: A comprehensive geochemical perspective.

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), <2.6 Myr after CAI formation. Subsequently, the Ryugu progenitor planetesimal was fragmented and evolved into the current asteroid Ryugu through sublimation.

Hypervelocity collision and water-rock interaction in space preserved in the Chelyabinsk ordinary chondrite.

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 ∼30 Ma 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.

Phase-field model for growth and dissolution of a stoichiometric compound in a binary liquid.

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.

Two mechanisms forming a comblike step pattern induced by a moving linear adatom source.

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.

Correction of the equilibrium temperature caused by slight evaporation of water in protein crystal growth cells during long-term space experiments at International Space Station.

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.

Period of a comblike pattern controlled by atom supply and noise.

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(p), is studied with the use of a phase field model. From a straight step, fluctuations of the most unstable wavelength λ(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, Λ, is determined when the exponential growth ends. The period depends on the strength F(u) of a current noise in diffusion as Λ∼λ(max)|lnF(u)|: such a logarithmic dependence is confirmed for the first time. A nonmonotonic V(p) dependence of Λ indicates that the comblike pattern with a small V(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.

Inhibition of gustatory plasticity due to acute nicotine exposure in the nematode Caenorhabditis elegans.

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 100mM NaCl with 3.0mM 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 3.0mM 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.

Magnetite 3D colloidal crystals formed in the early solar system 4.6 billion years ago.

Three-dimensional colloidal crystals made of ferromagnetic particles, such as magnetite (Fe(3)O(4)), cannot be synthesized in principle because of the strong attractive magnetic interaction. However, we discovered colloidal crystals composed of polyhedral magnetite nanocrystallites of uniform size in the range of a few hundred nanometers in the Tagish Lake meteorite. Those colloidal crystals were formed 4.6 billion years ago and thus are much older than natural colloidal crystals on earth, such as opals, which formed about 100 million years ago. We found that the size of each individual magnetite particle determines its morphology, which in turn plays an important role in deciding the packing structure of the colloidal crystals. We also hypothesize that each particle has a flux-closed magnetic domain structure, which reduces the interparticle magnetic force significantly.

Thyroglobulin may affect telomerase activity in thyroid follicular cells.

Telomerase (TA) activity is known to be present in malignant tumor cells, but not in most somatic differentiated cells. TA shows relatively high activity in thyroid cancer cells, but reports vary. This fact prompted us to elucidate whether cell component inhibitors of TA in the thyroid follicles can modulate its activity. The activity of TA extracted from Hela cells was inhibited by mixing with the supernatant fraction of human thyroid tissue extract. To examine the effect of iodine, thyroid hormones (l-T3 and l-T4) and human thyroglobulin (hTg) contained in the thyroid follicles, l-T3, l-T4 and hTg were added to the TRAP assay system in vitro, using TA from Hela cells. Iodine, l-T3 and l-T4 did not affect TA activity, but hTg inhibited the TA activity in a dose-dependent manner (IC(50) of hTg: ca 0.45 microM: inhibiting concentration of hTg was from 0.15 microM to 3.0 microM). The hTg inhibition was not evident in the RT-PCR system, suggesting no effect of hTg on Taq DNA polymerase activity. The hTg inhibition of TA activity was attenuated by dNTP but not significantly by TS primer. These data suggest that hTg contained in thyroid follicular cells of various thyroid diseases may affect the TA activity measured in biopsied thyroid specimens, and that the reduction of the TA activity by hTg may induce slow progression and growth, and low grade malignancy of thyroid cancer, particularly differentiated carcinoma.

Usefulness of galvanic skin reflex monitor in CT-guided thoracic sympathetic blockade for palmar hyperhidrosis.

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.

Scaphoid fractures in children: problems and treatment.

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.

Complications of vascularized fibula graft for reconstruction of long bones.

The clinical results and complications of the vascularized fibular graft for the reconstruction of various long bone defects were reviewed in 60 cases. Bony reconstruction was achieved in 57 of the 60 cases; however, various postoperative complications occurred in 54 percent of the cases. One case of arterial thrombosis of an anastomosed vessel and nine cases of venous congestion of the monitoring flap occurred in the early postoperative periods. The authors managed the nine cases of venous congestion of the flap conservatively, and all flaps survived. Partial necrosis of the flap was noted in eight of these nine cases, but additional surgical intervention was required in only four cases. Treatment included a gastrocnemius musculocutaneous flap in one case and a full-thickness skin graft in three cases. The vascularized fibula survived and bony fusion was achieved in all of these cases. The one case of arterial thrombosis resulted in graft failure due to a delay in the decision to perform a thrombectomy. Graft fracture occurred in 13 cases as the mechanical stress to the graft increased. In two cases of femoral reconstruction, graft fracture occurred during dynamization of the graft, despite the use of an Ilizarov external fixator. Correct alignment between the recipient bone and the external fixator is a prerequisite to preventing graft fracture. Vascularized fibular grafting offers the patient a great deal of benefit; however, this graft has a concomitant high risk of complications. Great attention to detail must be paid to prevent postoperative complications.

Scheduled conversion of replication complex architecture at replication origins of Saccharomyces cerevisiae during the cell cycle.

Replication of DNA within Saccharomyces cerevisiae chromosomes is initiated from multiple origins, whose activation follow their own inherent time schedules during the S phase of the cell cycle. It has been demonstrated that a characteristic replicative complex (RC) that includes an origin recognition complex is formed at each origin and shifts between post- and pre-replicative states during the cell cycle. We wanted to determine whether there was an association between this shift in the state of the RC and firing events at replication origins. Time course analyses of RC architecture using UV-footprinting with synchronously growing cells revealed that pre-replicative states at both early and late firing origins appeared simultaneously during late M phase, remained in this state during G(1) phase, and converted to the post-replicative state at various times during S phase. Because the conversion of the origin footprinting profiles and origin firing, as assessed by two-dimensional gel electrophoresis, occurred concomitantly at each origin, then these two events must be closely related. However, conversion of the late firing origin occurred without actual firing. This was observed when the late origin was suppressed in clb5-deficient cells and a replication fork originating from an outside origin replicated the late origin passively. This mechanism ensures that replication at each chromosomal locus occurs only once per cell cycle by shifting existing pre-RCs to the post-RC state, when it is replicated without firing.