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  • 1
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    An effective-medium model for P-wave velocities of saturated, unconsolidated saline permafrost (2017)
    Society of Exploration Geophysicists (SEG)
    Details
    Publication Date: 2017-05-03
    Description: To better understand the relationship between P-wave velocities and ice content in saturated, unconsolidated saline permafrost, we constructed an effective-medium model based upon ultrasonic P-wave data that were obtained from earlier laboratory studies. The model uses a two-end-member mixing approach in which an ice-filled, fully frozen end member and a water-filled, fully unfrozen end member are mixed together to form the effective medium of partially frozen sediments. This mixing approach has two key advantages: (1) It does not require parameter tuning of the mixing ratios, and (2) it inherently assumes mixed pore-scale distributions of ice that consist of frame-strengthening (i.e., cementing and/or load-bearing) ice and pore-filling ice. The model-predicted P-wave velocities agree well with our laboratory data, demonstrating the effectiveness of the model for quantitatively inferring ice content from P-wave velocities. The modeling workflow is simple and is largely free of calibration parameters — attributes that ease its application in interpreting field data sets.
    Print ISSN: 0016-8033
    Electronic ISSN: 1942-2156
    Topics: Geosciences , Physics
    Published by Society of Exploration Geophysicists (SEG)
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  • 2
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    Seismic wavefield imaging based on the replica exchange Monte Carlo method (2016)
    Oxford University Press
    Details
    Publication Date: 2016-12-04
    Description: Earthquakes sometimes cause serious disasters not only directly by ground motion itself but also secondarily by infrastructure damage, particularly in densely populated urban areas that have capital functions. To reduce the number and severity of secondary disasters, it is important to evaluate seismic hazards rapidly by analysing the seismic responses of individual structures to input ground motions. We propose a method that integrates physics-based and data-driven approaches in order to obtain a seismic wavefield for use as input to a seismic response analysis. The new contribution of this study is the use of the replica exchange Monte Carlo (REMC) method, which is one of the Markov chain Monte Carlo (MCMC) methods, for estimation of a seismic wavefield, together with a 1-D local subsurface structure and source information. Numerical tests were conducted to verify the proposed method, using synthetic observation data obtained from analytical solutions for two horizontally layered subsurface structure models. The geometries of the observation sites were determined from the dense seismic observation array called the Metropolitan Seismic Observation network, which has been in operation in the Tokyo metropolitan area in Japan since 2007. The results of the numerical tests show that the proposed method is able to search the parameters related to the source and the local subsurface structure in a broader parameter space than the Metropolis method, which is an ordinary MCMC method. The proposed method successfully reproduces a seismic wavefield consistent with a true wavefield. In contrast, ordinary kriging, which is a classical data-driven interpolation method for spatial data, is hardly able to reproduce a true wavefield, even in the low frequency bands. This suggests that it is essential to employ both physics-based and data-driven approaches in seismic wavefield imaging, utilizing seismograms from a dense seismic array. The REMC method, which provides not only optimum estimates of model parameters but also their uncertainties without become trapped in local maxima, is a powerful method for the stochastic estimation of seismic wavefields.
    Keywords: Seismology
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 3
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    Proto-Japan and tectonic erosion: Evidence from zircon geochronology of blueschist and serpentinite (2016)
    Geological Society of America (GSA)
    Details
    Publication Date: 2016-07-26
    Description: Blueschist facies rocks in the Shikoku island of southwest Japan were extruded from depth as blocks in the Kurosegawa serpentinite mélange, where they occur in association with other tectonic blocks of tonalite-trondhjemite-granodiorite (TTG) rocks and calc-alkaline volcanics. Here we report magmatic zircons in the blueschist that yield 206 Pb/ 238 U mean ages in the range 505 ± 3 to 503 ± 3 Ma. These zircons crystallized at a mid-ocean ridge within basaltic rocks, and migrated to the continental margin of paleo-Asia. Subduction of the oceanic lithosphere into the mantle at a depth of ~40 km resulted in metamorphism under jadeite-glaucophane facies conditions at 250 Ma. The blueschist facies rocks were then exhumed to the surface along a splay fault connected with the forearc region through tectonic extrusion. Zircons separated from serpentinite yielded a 206 Pb/ 238 U mean age of 152 ± 3 Ma, marking the timing of serpentine protrusion to the surface, consistent with geologic constraints. The serpentinites also contain minor ca. 500 Ma zircons, similar to those in the blueschist. The predominance of detrital ca. 150 Ma zircons in the serpentinite suggests extensive tectonic mixing of Jurassic trench turbidites with the mantle wedge. The Kurosegawa serpentinite mélange belt extends along the strike of the orogenic belt for more than 800 km, parallel to the active trench. We propose that this belt marks the location of extensive tectonic erosion and provides an excellent case study for the destruction of continental crust along a convergent plate boundary.
    Print ISSN: 1941-8264
    Electronic ISSN: 1947-4253
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 4
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    Prostagladin D2 is a mast cell-derived antiangiogenic factor in lung carcinoma [Pharmacology] (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-12-07
    Description: It is well established that prostaglandins (PGs) are involved in tumor angiogenesis and growth, yet the role of prostaglandin D2 (PGD2) remains virtually unknown. Here, we show that host hematopoietic PGD2 synthase (H-PGDS) deficiency enhances Lewis lung carcinoma (LLC) progression, accompanied by increased vascular leakage, angiogenesis, and monocyte/mast cell infiltration. This deficiency can be rescued by hematopoietic reconstitution with bone marrow from H-PGDS–naive (WT) mice. In tumors on WT mice, c-kit+ mast cells highly express H-PGDS. Host H-PGDS deficiency markedly up-regulated the expression of proangiogenic factors, including TNF-α in the tumor. In mast cell-null KitW-sh/W-sh mice, adoptive transfer of H-PGDS–deficient mast cells causes stronger acceleration in tumor angiogenesis and growth than in WT mast cells. In response to LLC growth, H-PGDS–deficient mast cells produce TNF-α excessively. This response is suppressed by the administration of a synthetic PGD2 receptor agonist or a degradation product of PGD2, 15-deoxy-Δ12,14-PGJ2. Additional TNF-α deficiency partially counteracts the tumorigenic properties seen in H-PGDS–deficient mast cells. These observations identify PGD2 as a mast cell-derived antiangiogenic factor in expanding solid tumors. Mast cell-derived PGD2 governs the tumor microenvironment by restricting excessive responses to vascular permeability and TNF-α production.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 5
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    Tmem100 for vascular development [Developmental Biology] (2012)
    National Academy of Sciences
    Details
    Publication Date: 2012-07-25
    Description: Members of the transforming growth factor-β superfamily play essential roles in various aspects of embryonic development and physiological organ function. Among them, bone morphogenetic protein (BMP) 9 and BMP10 regulate embryonic vascular development by activating their endothelial receptor ALK1 (activin receptor-like kinase 1, also called Acvrl1). ALK1-mediated intracellular signaling is implicated in the etiologies of human diseases, but their downstream functional proteins are largely unknown. In this study, we identified Tmem100, a gene encoding a previously uncharacterized intracellular transmembrane protein, to be an embryonic endothelium-enriched gene activated by BMP9 and BMP10 through the ALK1 receptor. Tmem100 null mice showed embryonic lethality due to impaired differentiation of arterial endothelium and defects of vascular morphogenesis, which phenocopied most of the vascular abnormalities observed with the Acvrl1/Alk1 deficiency. The activity of Notch- and Akt-mediated signaling, which is essential for vascular development, was down-regulated in Tmem100 null mice. Cre-mediated deletion of Tmem100 in endothelial cells was sufficient to recapitulate the null phenotypes. These data indicated that TMEM100 may play indispensable roles downstream of BMP9/BMP10-ALK1 signaling during endothelial differentiation and vascular morphogenesis.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 6
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    The crystal structure of an intermediate dimer of aspergilloglutamic peptidase that mimics the enzyme-activation product complex produced upon autoproteolysis (2012)
    Oxford University Press
    Details
    Publication Date: 2012-07-05
    Description: Aspergilloglutamic peptidase from Aspergillus niger var. macrosporus (AGP) is one of the so-called pepstatin-insensitive acid endopeptidases, which are distinct from the well-studied aspartic peptidases. Among the known homologues of the glutamic peptidases, AGP is a unique two-chain enzyme with a light chain and a heavy chain bound non-covalently with each other, and thus is an interesting target for protein structure–function relationship studies. In this article, we report the crystal structure of a dimeric form of the enzyme at a resolution of 1.6 Å. This form has a unique structure in which the C-terminal region of the light chain of one of the molecules binds to the active site cleft of the other molecule like a part of a substrate. This form mimics the enzyme-activation product complex produced upon autoproteolysis, and provides a structural clue that could help to clarify the activation mechanism. This type of dimeric structure of a peptidase is here reported for the first time.
    Print ISSN: 0021-924X
    Electronic ISSN: 1756-2651
    Topics: Biology , Chemistry and Pharmacology
    Published by Oxford University Press on behalf of The Japanese Biochemical Society (JBS).
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  • 7
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    Structure of the connexin 26 gap junction channel at 3.5 A resolution (2009)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2009-04-03
    Description: Gap junctions consist of arrays of intercellular channels between adjacent cells that permit the exchange of ions and small molecules. Here we report the crystal structure of the gap junction channel formed by human connexin 26 (Cx26, also known as GJB2) at 3.5 A resolution, and discuss structural determinants of solute transport through the channel. The density map showed the two membrane-spanning hemichannels and the arrangement of the four transmembrane helices of the six protomers forming each hemichannel. The hemichannels feature a positively charged cytoplasmic entrance, a funnel, a negatively charged transmembrane pathway, and an extracellular cavity. The pore is narrowed at the funnel, which is formed by the six amino-terminal helices lining the wall of the channel, which thus determines the molecular size restriction at the channel entrance. The structure of the Cx26 gap junction channel also has implications for the gating of the channel by the transjunctional voltage.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Maeda, Shoji -- Nakagawa, So -- Suga, Michihiro -- Yamashita, Eiki -- Oshima, Atsunori -- Fujiyoshi, Yoshinori -- Tsukihara, Tomitake -- England -- Nature. 2009 Apr 2;458(7238):597-602. doi: 10.1038/nature07869.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Protein Research, Osaka University, OLABB, 6-2-3, Furuedai, Suita, Osaka 565-0874, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19340074" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Line ; Connexins/*chemistry/genetics ; Crystallography, X-Ray ; Gap Junctions/*chemistry ; Humans ; Ion Channel Gating ; Models, Molecular ; Protein Multimerization ; Protein Structure, Quaternary ; Spodoptera/virology
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 8
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    Propagation of slow slip leading up to the 2011 M(w) 9.0 Tohoku-Oki earthquake (2012)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2012-01-24
    Description: Many large earthquakes are preceded by one or more foreshocks, but it is unclear how these foreshocks relate to the nucleation process of the mainshock. On the basis of an earthquake catalog created using a waveform correlation technique, we identified two distinct sequences of foreshocks migrating at rates of 2 to 10 kilometers per day along the trench axis toward the epicenter of the 2011 moment magnitude (M(w)) 9.0 Tohoku-Oki earthquake in Japan. The time history of quasi-static slip along the plate interface, based on small repeating earthquakes that were part of the migrating seismicity, suggests that two sequences involved slow-slip transients propagating toward the initial rupture point. The second sequence, which involved large slip rates, may have caused substantial stress loading, prompting the unstable dynamic rupture of the mainshock.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kato, Aitaro -- Obara, Kazushige -- Igarashi, Toshihiro -- Tsuruoka, Hiroshi -- Nakagawa, Shigeki -- Hirata, Naoshi -- New York, N.Y. -- Science. 2012 Feb 10;335(6069):705-8. doi: 10.1126/science.1215141. Epub 2012 Jan 19.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Earthquake Research Institute, The University of Tokyo, Tokyo, Japan. akato@eri.u-tokyo.ac.jp〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22267578" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    Seismic Wavefield Imaging of Long-Period Ground Motion in the Tokyo Metropolitan Area, Japan (2017)
    Wiley
    Details
    Publication Date: 2017-07-08
    Description: Long-period ground motions due to large earthquakes can cause devastating disasters, especially in urbanized areas located on sedimentary basins. To assess and mitigate such damage, it is essential to rapidly evaluate seismic hazards for infrastructures, which can be simulated by seismic response analyses that use waveforms at the base of each infrastructure as an input ground motion. The present study reconstructs the seismic wavefield in the Tokyo metropolitan area located on the Kanto sedimentary basin, Japan, from seismograms of the Metropolitan Seismic Observation network (MeSO-net). The obtained wavefield fully explains the observed waveforms in the frequency band of 0.10–0.20 Hz. This is attributed to the seismic wavefield imaging technique proposed by Kano et al . [2017], which implements the replica exchange Monte Carlo method to simultaneously estimate model parameters related to the subsurface structure and source information. Further investigation shows that the reconstructed seismic wavefield lower than 0.30 Hz is of high quality in terms of variance reduction, which quantifies a misfit in waveforms, but that the variance reduction rapidly worsens in higher frequencies. Meanwhile, the velocity response spectra show good agreement with observations up to 0.90 Hz in terms of the combined goodness-of-fit, which is a measure of misfit in the velocity response spectra. Inputting the reconstructed wavefield into seismic response analyses, we can rapidly assess the overall damage to infrastructures immediately after a large earthquake.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
    Electronic Resource
    Electronic Resource
    The control of magnetic characteristics of BaM ferrite thin films by bias sputtering (abstract) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6696-6696 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thin films of a magnetoplumbite type of barium (BaM) ferrite have been deposited on SiO2/Si substrates at a rate of 100 A(ring)/min in a gas mixture of 10% O2–90% Ar at a pressure of 2 mTorr by using the facing targets sputtering (FTS) apparatus. They possessed excellent chemical stability and high corrosion resistivity as well as perpendicular anisotropy as large as applicable for perpendicular magnetic recording media. They also seem to be applicable for millimeter wave isolator and circulator. In this study, the saturation magnetization Ms, the coercive force Hc, and the anisotropy field Hk of BaM ferrite films have been controlled by adjusting the rf-bias voltages to substrate Vb during sputtering, where Vb was always negative. The dependencies of Ms and Hc on Vb were shown in Fig. 1. Ms took the maximum value as large as 345 emu/cc at Vb of −30 V and decreased as Vb decreased in the range below −50 V. On the other hand, the perpendicular Hc decreased as Vb increased in the range above −100 V and took the minimum value as low as 910 Oe at Vb of −95 V. Hk and the magnetic anisotropy constant Ku also greatly depended on Vb. Such an apparent Vb dependence of these magnetic characteristics of BaM ferrite films seem to be attributed to the definite change in c-axis orientation of hexagonal crystallite and the different distribution of Fe3+ ions among several occupation sites. These results indicated that the c-axis orientation of BaM ferrite crystallites were promoted by applying proper Vb. Consequently, the bias sputtering technique with FTS method may be useful for preparing the BaM ferrite films composed of the multilayers with different magnetic characteristics, even if only one pair of targets are used without adjusting the other sputtering conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352506
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