Evaporation of Fe and FeS dust in the active stage of the primordial solar nebula, and Fe/S fractionation

The evaporation kinetics of troilite and metallic iron was applied to evaporation of dust particles moving toward the protosun in the turbulent solar nebula. In the calculations, it was assumed that dust particles do not grow by collision, evaporated gas and residual dust are not separated, and dust particles move only radially along the midplane or the surface of the nebula. It was found that evaporation of metallic iron would occur almost in equilibrium both along the midplane and the surface. Troilite could survive to higher temperature than the equilibrium evaporation temperature due to its evaporation kinetics. However, the kinetic effects are not so large, and the incongruent evaporation of troilite is also regarded to occur roughly in equilibrium. The timescales for evaporation of metallic iron and troilite were compared with the timescales for drifts along r-and z-directions and that for coagulation to understand general aspects of the effect of evaporation kinetics. Since the temperature of the surface is lower than that of the midplane, dust particle at the surface can get closer to the sun than those at the midplane. This can cause Fe/S fractionation in a wide range of the nebula if effective solid-gas separation occurred

Chondrule age distribution and rate of heating events for chondrule formation

Chondrules are considered to be formed by flash heating events in the protoplanetary disk. In order to evaluate some basic factors in the heating mechanism, we examined the rate of heating events that explains the abundance and the observed age distribution of chondrules in unequilibrated ordinary chondrites. First, we compiled the literature data of ^(26)Al ages of chondrules from the least equilibrated ordinary chondrites (LL3.0-3.1), ranging from 1Myr to 3Myr with a peak at about 1.8Myr relative to the formation time of Ca, Al-rich inclusions (CAIs) in carbonaceous chondrites, the oldest solid materials formed in the solar system. Next, we made a simple phenomenological chondrule formation model assuming that each event heated only a small fraction of existing dust at one time and numerous heating events produced chondrules. Results indicate that (1) an average number of heating events experienced by a dust particle should be 1.2 or higher, (2) more than a half of the present chondrules were reheated, (3) chondrule formation started sometime between 0.4-1.5Myr and ended at 2.2-2.3Myr after the CAI formation, and (4) the rate of heating events has a peak at 0.1-0.8Myr earlier than the peak of the observed chondrule age distribution and should decrease monotonically with time after the peak

Postoperative complications of Okabayashi's operation for carcinoma of the cervix in recent 5 years

Okabayashi's radical extensive hysterectomy is one of the excellent operations for carcinoma of the cervix. In this study on the postoperative complications during the recent 5 years, we obtained the following results. 1. In the total of 861 cases studied, the primary mortality amounts to 1.2 per cent, the incidence of the uretero-vaginal fistula 2.7 per cent, the pelvic abscess 16.8 per cent, and the lymphocyst 23.3 per cent. 2. On comparing the results with our previous ones as well as those of other investigators, it is found that satisfactory results have been obtained due to the advent of various antibiotics in recent years and also due to a marked advance made in the technics of blood and fluid administration as well as anesthesia. 3. Since the various complications have not completely been overcome and they still pose an important problem, an effort should be made toward a better postoperative care in order to prevent the complications.</p

Experiments quantifying elemental and isotopic fractionations during evaporation of CAI-like melts in low-pressure hydrogen and in vacuum : Constraints on thermal processing of CAI in the protoplanetary disk

This work was supported by NASA grant NNX17AE84G (to R.M.). Magnesium isotopic measurements were supported by NSF grant EAR-17407706 (to F.-Z. T.). P.S. and the Si isotope measurements made at the St Andrews Isotope Group (STAiG) at the University of St Andrews were supported by NERC grant NE/R002134/1 a Carnegie Trust Research Incentive Grant. Evaporation experiments at Hokkaido University were supported by the Ministry of Education, Sports, Science, and Technology KAKENHI Grant (to S.T.).It is widely believed that the precursors of coarse-grained CAIs in chondrites are solar nebula condensates that were later reheated and melted to a high degree. Such melting under low-pressure conditions is expected to result in evaporation of moderately volatile magnesium and silicon and their mass-dependent isotopic fractionation. The evaporation of silicate melts has been extensively studied in vacuum laboratory experiments and a large experimental database on chemical and isotopic fractionations now exists. Nevertheless, it remains unclear if vacuum evaporation of CAI-like melts adequately describes the evaporation in the hydrogen-rich gas of the solar nebula. Here we report the results of a detailed experimental study on evaporation of a such melt at 1600°C in both vacuum and low-pressure hydrogen gas, using 1.5- and 2.5-mm diameter samples. The experiments show that although at 2×10−4 bar H2 magnesium and silicon evaporate ∼2.8 times faster than at 2×10−5 bar H2 and ∼45 times faster than in vacuum, their relative evaporation rates and isotopic fractionation factors remain the same. This means that the chemical and isotopic evolutions of all evaporation residues plot along a single evaporation trajectory regardless of experimental conditions (vacuum or low-PH2) and sample size. The independence of chemical and isotopic evaporation trajectories on PH2 of the surrounding gas imply that the existing extensive experimental database on vacuum evaporation of CAI-like materials can be safely used to model the evaporation under solar nebula conditions, taking into account the dependence of evaporation kinetics on PH2. The experimental data suggest that it would take less than 25 minutes at 1600°C to evaporate 15–50% of magnesium and 5–20% of silicon from a 2.5-mm diameter sample in a solar nebula with PH2∼2×10−4 bar and to enrich the residual melt in heavy magnesium and silicon isotopes up to δ25Mg ∼ 5–10‰ and δ29Si ∼ 2–4‰. The expected chemical and isotopic features are compatible to those typically observed in coarse-grained Type A and B CAIs. Evaporation for ∼1 hour will produce δ25Mg ∼30–35‰ and δ29Si ∼10–15‰, close to the values in highly fractionated Type F and FUN CAIs. These very short timescales suggest melting and evaporation of CAI precursors in very short dynamic heating events. The experimental results reported here provide a stringent test of proposed astrophysical models for the origin and evolution of CAIs.PostprintPeer reviewe

Topkapı Sarayı Müzesinde Türk saatleri

Taha Toros Arşivi, Dosya No: 114-Müzelerİstanbul Kalkınma Ajansı (TR10/14/YEN/0033) İstanbul Development Agency (TR10/14/YEN/0033

Spatial Distribution of AlO in a High-mass Protostar Candidate Orion Source I

UTokyo FOCUS Press releases "Our history in the stars : Matter around a young star helps astronomers explore our stellar history" https://www.u-tokyo.ac.jp/focus/en/press/z0508_00043.htm

Construction and Characterization of a PGN_0297 Mutant of Porphyromonas gingivalis: Evidence of the Contribution of PGN_0297 to Gingipain Activity

The periodontal pathogen Porphyromonas gingivalis shows colonial pigmentation on blood agar and produces gingipains (Kgp, RgpA, and RgpB), cysteine proteases involved in an organism’s virulence and pigmentation. We showed previously that deletion of the PGN_0300 gene abolished the pigmentation activity and reduced the proteolytic activity of gingipains. The role of the PGN_0297 gene, which consists of an operon with the PGN_0300 gene, is unclear. Herein we examined the effect of PGN_0297 gene deletion on the pigmentation and proteolytic activities and transcriptional levels of gingipains. A PGN_0297 gene deletion mutant (ΔPGN_0297) did not exhibit the pigmentation. The proteolytic activity of the gingipains was decreased in the culture supernatant and on the cell surface of ΔPGN_0297. The mutant ΔPGN_0297 failed to attenuate Akt phosphorylation at Thr308 and Ser473, but both phosphorylations were attenuated in the wild-type and its complementation strain. The deletion of PGN_0297 gene did not substantially affect the transcriptional levels of the gingipain genes kgp, rgpA, and rgpB. Taken together, these results indicate that PGN_0297 is closely involved in the secretion and maturation of gingipains

Organic chemical variation between hydrous and anhydrous Antarctic micrometeorites

第6回極域科学シンポジウム[OA] 南極隕石11月17日（火）　国立国語研究所 2階 講

One-pot synthesis of amino acid precursors with insoluble organic matter in planetesimals with aqueous activity

We report that the water-soluble amino acid precursors are synthesized from formaldehyde, glycolaldehyde, and ammonia with the presence of liquid water, simultaneously with macromolecular organic solids similar to the chondritic IOM. Amino acid products from hydrothermal experiments after acid hydrolysis include α-, β-, and γ-amino acids up to five carbons, for which relative abundances are similar to those extracted from carbonaceous chondrites. One-pot aqueous processing from simple ubiquitous molecules can thus produce a wide variety of meteoritic organic matter from amino acid precursors to macromolecular IOM in chondrite parent bodies.Yoko Kebukawa, Queenie H. S. Chan, Shogo Tachibana, Kensei Kobayashi and Michael E. Zolensk