| 1. |
- Sugita, S., et al.
(author)
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The geomorphology, color, and thermal properties of Ryugu: Implications for parent-body processes
- 2019
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In: Science. - : AAAS. - 0036-8075 .- 1095-9203. ; 364:6437
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Journal article (peer-reviewed)abstract
- Asteroids fall to Earth in the form of meteorites, but these provide little information about their origins. The Japanese mission Hayabusa2 is designed to collect samples directly from the surface of an asteroid and return them to Earth for laboratory analysis. Three papers in this issue describe the Hayabusa2 team's study of the near-Earth carbonaceous asteroid 162173 Ryugu, at which the spacecraft arrived in June 2018 (see the Perspective by Wurm). Watanabeet al.measured the asteroid's mass, shape, and density, showing that it is a “rubble pile” of loose rocks, formed into a spinning-top shape during a prior period of rapid spin. They also identified suitable landing sites for sample collection. Kitazatoet al.used near-infrared spectroscopy to find ubiquitous hydrated minerals on the surface and compared Ryugu with known types of carbonaceous meteorite. Sugitaet al.describe Ryugu's geological features and surface colors and combined results from all three papers to constrain the asteroid's formation process. Ryugu probably formed by reaccumulation of rubble ejected by impact from a larger asteroid. These results provide necessary context to understand the samples collected by Hayabusa2, which are expected to arrive on Earth in December 2020.Science, this issue p.268, p.272, p.eaaw0422; see also p.230
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| 2. |
- Sakatani, N., et al.
(author)
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Anomalously porous boulders on (162173) Ryugu as primordial materials from its parent body
- 2021
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In: Nature Astronomy. - : Springer Nature. - 2397-3366. ; 5:8, s. 766-774
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Journal article (peer-reviewed)abstract
- Planetesimals—the initial stage of the planetary formation process—are considered to be initially very porous aggregates of dusts1,2, and subsequent thermal and compaction processes reduce their porosity3. The Hayabusa2 spacecraft found that boulders on the surface of asteroid (162173) Ryugu have an average porosity of 30–50% (refs. 4,5,6), higher than meteorites but lower than cometary nuclei7, which are considered to be remnants of the original planetesimals8. Here, using high-resolution thermal and optical imaging of Ryugu’s surface, we discovered, on the floor of fresh small craters (<20 m in diameter), boulders with reflectance (~0.015) lower than the Ryugu average6 and porosity >70%, which is as high as in cometary bodies. The artificial crater formed by Hayabusa2’s impact experiment9 is similar to these craters in size but does not have such high-porosity boulders. Thus, we argue that the observed high porosity is intrinsic and not created by subsequent impact comminution and/or cracking. We propose that these boulders are the least processed material on Ryugu and represent remnants of porous planetesimals that did not undergo a high degree of heating and compaction3. Our multi-instrumental analysis suggests that fragments of the highly porous boulders are mixed within the surface regolith globally, implying that they might be captured within collected samples by touch-down operations10,11.
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| 3. |
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| 4. |
- Pastorello, A., et al.
(author)
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A giant outburst two years before the core-collapse of a massive star
- 2007
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 447:7146, s. 829-832
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Journal article (peer-reviewed)abstract
- The death of massive stars produces a variety of supernovae, which are linked to the structure of the exploding stars(1,2). The detection of several precursor stars of type II supernovae has been reported ( see, for example, ref. 3), but we do not yet have direct information on the progenitors of the hydrogen-deficient type Ib and Ic supernovae. Here we report that the peculiar type Ib supernova SN 2006jc is spatially coincident with a bright optical transient(4) that occurred in 2004. Spectroscopic and photometric monitoring of the supernova leads us to suggest that the progenitor was a carbon-oxygen Wolf - Rayet star embedded within a helium-rich circumstellar medium. There are different possible explanations for this pre-explosion transient. It appears similar to the giant outbursts of luminous blue variable stars (LBVs) of 60 - 100 solar masses(5), but the progenitor of SN 2006jc was helium- and hydrogen-deficient ( unlike LBVs). An LBV-like outburst of a Wolf - Rayet star could be invoked, but this would be the first observational evidence of such a phenomenon. Alternatively, a massive binary system composed of an LBV that erupted in 2004, and a Wolf - Rayet star exploding as SN 2006jc, could explain the observations.
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| 5. |
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| 6. |
- Dall'Ora, M., et al.
(author)
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THE TYPE IIP SUPERNOVA 2012aw IN M95 : HYDRODYNAMICAL MODELING OF THE PHOTOSPHERIC PHASE FROM ACCURATE SPECTROPHOTOMETRIC MONITORING
- 2014
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In: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 787:2, s. 139-
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Journal article (peer-reviewed)abstract
- We present an extensive optical and near-infrared photometric and spectroscopic campaign of the Type IIP supernova SN 2012aw. The data set densely covers the evolution of SN 2012aw shortly after the explosion through the end of the photospheric phase, with two additional photometric observations collected during the nebular phase, to fit the radioactive tail and estimate the Ni-56 mass. Also included in our analysis is the previously published Swift UV data, therefore providing a complete view of the ultraviolet-optical-infrared evolution of the photospheric phase. On the basis of our data set, we estimate all the relevant physical parameters of SN 2012aw with our radiation-hydrodynamics code: envelope mass M-env similar to 20 M-circle dot, progenitor radius R similar to 3 x 10(13) cm (similar to 430 R-circle dot), explosion energy E similar to 1.5 foe, and initial Ni-56 mass similar to 0.06 M-circle dot. These mass and radius values are reasonably well supported by independent evolutionary models of the progenitor, and may suggest a progenitor mass higher than the observational limit of 16.5 +/- 1.5 M-circle dot of the Type IIP events.
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| 7. |
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| 8. |
- Ohtani, S, et al.
(author)
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Simultaneous prenoon and postnoon observations of 3 field-aligned current systems from Viking and DMSP F7
- 1995
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In: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 100:A1, s. 119-136
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Journal article (peer-reviewed)abstract
- The spatial structure of dayside large-scale field-aligned current (FAG) systems is examined by using Viking and DMSP-F7 data. We focus on four events in which the satellites simultaneously observed postnoon and prenoon three FAC systems: the region 2, the region 1, and the mantle (referred to as midday region 0) systems, from equatorward to poleward. These events provide the most solid evidence to date that the midday region 0 system is a separate and unique FAC system, and is not an extension of the region 1 system from other local times. The events are examined comprehensively by making use of a multi-instrument data set, which includes magnetic field, particle flux, electric field, auroral UV image data from the satellites, and the Sondrestrom convection data. The results are summarized as follows: (1) Region 2 currents flow mostly in the CPS precipitation region, often overlapping with the BPS at their poleward edge. (2) The region 1 system is located in the core part of the auroral oval and is confined in a relatively narrow range in latitude which includes the convection reversal. The low-latitude boundary layer, possibly including the outer part of the plasma sheet, and the external cusp are the major source regions of dayside region 1 currents. (3) Midday region 0 currents flow on open field lines and are collocated with the shear of antisunward convection flows with velocities decreasing poleward. On the basis of these results we support the view that both prenoon and postnoon current systems consist of the three-sheet structure when the distortion of the convection pattern associated with interplanetary magnetic field (IMF) B-y is small and both morningside and eveningside convection cells are crescent-shaped. We also propose that the midday region 0 and a part of the region 1 systems are closely coupled to the same source.
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| 9. |
- Quintero Noda, C., et al.
(author)
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Chromospheric polarimetry through multiline observations of the 850nm spectral region III : Chromospheric jets driven by twisted magnetic fields
- 2019
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 486:3, s. 4203-4215
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Journal article (peer-reviewed)abstract
- We investigate the diagnostic potential of the spectral lines at 850 nm for understanding the magnetism of the lower atmosphere. For that purpose, we use a newly developed 3D simulation of a chromospheric jet to check the sensitivity of the spectral lines to this phenomenon as well as our ability to infer the atmospheric information through spectropolarimetric inversions of noisy synthetic data. We start comparing the benefits of inverting the entire spectrum at 850 nm versus only the Ca II 8542 angstrom spectral line. We found a better match of the input atmosphere for the former case, mainly at lower heights. However, the results at higher layers were not accurate. After several tests, we determined that we need to weight more the chromospheric lines than the photospheric ones in the computation of the goodness of the fit. The new inversion configuration allows us to obtain better fits and consequently more accurate physical parameters. Therefore, to extract the most from multiline inversions, a proper set of weights needs to be estimated. Besides that, we conclude again that the lines at 850 nm, or a similar arrangement with Ca II 8542 angstrom plus Zeeman-sensitive photospheric lines, pose the best-observing configuration for examining the thermal and magnetic properties of the lower solar atmosphere.
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| 10. |
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| 11. |
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| 12. |
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| 13. |
- Hasegawa, Y., et al.
(author)
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Role of Mfa5 in Expression of Mfa1 Fimbriae in Porphyromonas gingivalis
- 2016
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In: Journal of Dental Research. - : International & American Associations for Dental Research. - 0022-0345 .- 1544-0591. ; 95:11, s. 1291-1297
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Journal article (peer-reviewed)abstract
- Fimbriae are protein-based filamentous appendages that protrude from the bacterial cell surface and facilitate host adhesion. Two types of fimbriae, FimA and Mfa1, of the periodontal pathogen Porphyromonas gingivalis are responsible for adherence to other bacteria and to host cells in the oral cavity. Both fimbrial forms are composed of 5 proteins, but there is limited information about their polymerization mechanisms. Here, the authors evaluated the function of Mfa5, one of the Mfa1 fimbrial accessory proteins. Using mfa5 gene disruption and complementation studies, the authors revealed that Mfa5 affects the incorporation of other accessory proteins, Mfa3 and Mfa4, into fibers and the expression of fimbriae on the cell surface. Mfa5 is predicted to have a C-terminal domain (CTD) that uses the type IX secretion system (T9SS), which is limited to this organism and related Bacteroidetes species, for translocation across the outer membrane. To determine the relationship between the putative Mfa5 CTD and the T9SS, mutants were constructed with in-frame deletion of the CTD and deletion of porU, a C-terminal signal peptidase linked to T9SS-mediated secretion. The ∆CTD-expressing strain presented a similar phenotype to the mfa5 disruption mutant with reduced expression of fimbriae lacking all accessory proteins. The ∆porU mutants and the ∆CTD-expressing strain showed intracellular accumulation of Mfa5. These results indicate that Mfa5 function requires T9SS-mediated translocation across the outer membrane, which is dependent on the CTD, and subsequent incorporation into fibers. These findings suggest the presence of a novel polymerization mechanism of the P. gingivalis fimbriae.
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| 14. |
- Hidaka, R., et al.
(author)
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Impact of the Comprehensive Awareness Modification of Mouth, Chewing and Meal (CAMCAM) Program on the Attitude and Behavior Towards Oral Health and Eating Habits as Well as the Condition of Oral Frailty : A Pilot Study
- 2023
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In: The Journal of Nutrition, Health & Aging. - : Springer-Verlag Italia s.r.l.. - 1279-7707 .- 1760-4788. ; 27:5, s. 340-
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Journal article (peer-reviewed)abstract
- Objectives: Preserving sufficient oral function and maintaining adequate nutrition are essential for preventing physical frailty and the following long-term care. We recently developed the 6-month Comprehensive Awareness Modification of Mouth, Chewing And Meal (CAMCAM) program, in which participants gather monthly to learn about oral health and nutrition while eating a textured lunch together. This study examined whether the CAMCAM program could improve attitude and behavior towards oral health, mastication, and diet as well as ameliorate oral frailty in community-dwelling older adults. Design: Single-arm pre-post comparison study. Setting and Participants: A total of 271 community-dwelling adults (72.3 ± 5.7 years of age; 159 women [58.7%]) in 4 Japanese municipalities were recruited, of which 249 participants (92%) were assessed at the final evaluation. Intervention: Participants gathered once a month at community centers to learn about oral health and nutrition while eating a “munchy” textured lunch containing proper nutrition. Measurements: Oral frailty, frailty, and eating behavior were evaluated with the Oral Frailty Index-8 (OFI-8), Kihon checklist (KCL), and CAMCAM checklist, respectively. Participants were divided into Oral frailty (OF) and Robust groups according to OFI-8 scores. The differences in KCL and CAMCAM checklist results between the OF and Robust groups were statistically tested along with changes in scores after the program. Results: KCL and CAMCAM checklist scores were significantly lower in the OF group at the initial assessment. OFI-8 and KCL findings were significantly improved in the OF group after completing the program (all P <0.05). Regarding the CAMCAM checklist, awareness of chewing improved significantly in the Robust group (P=0.009), with a similar tendency in the OF group (P=0.080). Conclusion: The findings of this pilot study suggest that the CAMCAM program may improve both oral and systemic frailty in addition to attitudes towards chewing, oral health, and meals, especially in individuals with oral frailty. The CAMCAM program merits expansion as a community-based frailty prevention program.
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| 15. |
- Ohtani, S, et al.
(author)
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4 Large-scale field-aligned current systems in the dayside high-latitude region
- 1995
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In: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 100, s. 137-153
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Journal article (peer-reviewed)abstract
- A system of four current sheets of large-scale field-aligned currents (FACs) was discovered in the data set of simultaneous Viking and DMSP-F7 crossings of the dayside high-latitude region. This paper reports four examples of this system that were observed in the prenoon sector. The flow polarities of FACs are upward, downward, upward, and downward, from equatorward to poleward. The lowest-latitude upward current is flowing mostly in the CPS precipitation region, often overlapping with the BPS at its poleward edge, and is interpreted as a region 2 current. The pair of downward and upward FACs in the middle of the structure are collocated with structured electron precipitation. The precipitation of high-energy (>1 keV) electrons is more intense in the lower-latitude downward current sheet. The highest-latitude downward flowing current sheet is located in a weak, low-energy particle precipitation region, suggesting that this current is flowing on open field lines. Simultaneous observations in the postnoon local time sector reveal the standard three-sheet structure of FACs, sometimes described as region 2, region 1, and mantle (referred to the midday region 0) currents. A high correlation was found between the occurrence of the four FAC sheet structure and negative interplanetary magnetic field (IMF) B-Y, We discuss the FAC structure in terms of three types of convection cells: the merging, viscous, and lobe cells. During strongly negative IMF B-Y two convection reversals exist in the prenoon sector; one is inside the viscous cell, and the other is between the viscous cell and the lobe cell. This structure of convection flow is supported by the Viking electric field and auroral UV image data. Based on the convection pattern, the four FAC sheet structure is interpreted as the latitudinal overlap of midday and morning FAC systems. We suggest that the four-current sheet structure is common in a certain prenoon local time sector during strongly negative IMF B-Y.
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| 16. |
- Pälike, Heiko, et al.
(author)
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A Cenozoic record of the equatorial Pacific carbonate compensation depth
- 2012
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 488:7413, s. 609-614
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Journal article (peer-reviewed)abstract
- Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0-3.5 kilometres during the early Cenozoic (approximately 55 million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.
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| 17. |
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| 18. |
- Tomasella, L., et al.
(author)
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Comparison of progenitor mass estimates for the Type IIP SN 2012A
- 2013
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 434:2, s. 1636-1657
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Journal article (peer-reviewed)abstract
- We present the one-year long observing campaign of SN 2012A which exploded in the nearby (9.8 Mpc) irregular galaxy NGC 3239. The photometric evolution is that of a normal Type IIP supernova, but the plateau is shorter and the luminosity not as constant as in other supernovae of this type. The absolute maximum magnitude, with M-B = -16.23 +/- 0.16 mag, is close to the average for SN IIP. Thanks also to the strong UV flux in the early phase, SN 2012A reached a peak luminosity of about 2 x 10(42) erg s(-1), which is brighter than those of other SNe with a similar Ni-56 mass. The latter was estimated from the luminosity in the exponential tail of the light curve and found to be M(Ni-56) = 0.011 +/- 0.004 M-circle dot, which is intermediate between standard and faint SN IIP. The spectral evolution of SN 2012A is also typical of SN IIP, from the early spectra dominated by a blue continuum and very broad (similar to 10(4) km s(-1)) Balmer lines, to the late-photospheric spectra characterized by prominent P-Cygni features of metal lines (Fe ii, Sc ii, Ba ii, Ti ii, Ca ii, Na i D). The photospheric velocity is moderately low, similar to 3 x 10(3) km s(-1) at 50 d, for the low optical depth metal lines. The nebular spectrum obtained 394 d after the shock breakout shows the typical features of SNe IIP and the strength of the [O i] doublet suggests a progenitor of intermediate mass, similar to SN 2004et (similar to 15 M-circle dot). A candidate progenitor for SN 2012A has been identified in deep, pre-explosion K-'-band Gemini North Near-InfraRed Imager and Spectrometer images, and found to be consistent with a star with a bolometric magnitude -7.08 +/- 0.36 (log L/L-circle dot = 4.73 +/- 0.14 dex). The magnitude of the recovered progenitor in archival images points towards a moderate-mass 10.5(-2)(+4.5) M-circle dot star as the precursor of SN 2012A. The explosion parameters and progenitor mass were also estimated by means of a hydrodynamical model, fitting the bolometric light curve, the velocity and the temperature evolution. We found a best fit for a kinetic energy of 0.48 foe, an initial radius of 1.8 x 10(13) cm and ejecta mass of 12.5 M-circle dot. Even including the mass for the compact remnant, this appears fully consistent with the direct measurements given above.
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| 19. |
- Zhang, Shi-Li, et al.
(author)
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Abnormal anti-Stokes Raman scattering of carbon nanotubes
- 2002
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 66:3
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Journal article (peer-reviewed)abstract
- Abnormal anti-Stokes Raman scattering (AASR) was unambiguously observed in carbon nanotubes (CNT's). In contrast to traditional Raman scattering theory, the absolute value of the Raman frequency of the anti-Stokes peak is not the same as that of the corresponding Stokes peak. It was demonstrated that AASR scattering originates from the unique nanoscale cylindrical structure of CNT's that can be considered naturally as a graphite structure with an intrinsic defect from its rolling. The double-resonance Raman scattering theory was applied to interpret the scattering mechanism of the AASR phenomenon successfully and quantitatively.
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