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  • 1
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    Heat flux and plasma flow in the far scrape-off layer of the inboard poloidal field null configuration in QUEST (2015)
    American Institute of Physics (AIP)
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    Publication Date: 2015-08-28
    Description: Heat flux and plasma flow in the scrape-off layer (SOL) are examined for the inboard poloidal field null (IPN) configuration of the spherical tokamak QUEST. In the plasma current ( I p ) ramp-up phase, high heat flux (〉1 MW/m 2 ) and supersonic flow (Mach number M  〉 1) are found to be present simultaneously in the far-SOL. The heat flux is generated by energetic electrons excursed from the last closed flux surface. Supersonic flows in the poloidal and toroidal directions are correlated with each other. In the quasi-steady state, sawtooth-like oscillation of I p at 20 Hz is observed. Heat flux and subsonic plasma flow in the far-SOL are modified corresponding to the I p -oscillation. The heat flow caused by motion of energetic electrons and the bulk-particle transport to the far-SOL is enhanced during the low- I p phase. Modification of plasma flow in the far SOL occurs earlier than the I p crash. The M–I p curve has a limit-cycle characteristic with sawtooth-like oscillation. Such a core–SOL relationship indicates that the far-SOL flow plays an important role in sustaining the oscillation of I p in the IPN configuration.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Electrical properties of pseudo-single-crystalline germanium thin-film-transistors fabricated on glass substrates (2015)
    American Institute of Physics (AIP)
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    Publication Date: 2015-10-06
    Description: By developing a low-temperature (≤300 °C) fabrication process for the gate-stack structure on Ge(111), we study electrical properties of thin film transistors (TFTs) consisting of (111)-oriented pseudo-single-crystalline-germanium (PSC-Ge) channels on glass. Although the Hall mobility ( μ Hall ) of p -type PSC-Ge layers reaches 210 cm 2 /V s and the gate-stack/Ge interface has low trap density, we observe field-effect-mobility ( μ FE ) fluctuation in the p -channel TFTs from 8.2 to 71 cm 2 /V s, depending on the thickness of the PSC-Ge layer. Considering the μ FE fluctuation and low I on / I off ratio in the p -TFTs, we infer the presence of defective Ge layers near the surface of the glass substrate. This study reveals that it is quite important for the high-performance p -Ge TFTs to improve the quality of the Ge layer near the surface of the glass substrate or to choose other materials with better Ge/substrate interface qualities.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 3
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    Plasma particle simulations on stray photoelectron current flows around a spacecraft (2012)
    Wiley
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    Publication Date: 2012-09-13
    Description: In tenuous space plasmas, photoelectron flows produce complex current paths among multiple conducting elements of spacecraft, which may influence the current–voltage characteristics of double-probe electric field sensors. We performed full-particle simulations on this effect by assuming a sensor configuration that is typical of recent designs like those on Cluster, THEMIS, and BepiColombo/MMO; the spherical probe is separated from a conducting boom by biased electrodes known as the ‘stub’ and the ‘guard’. The assumed bias potential scheme corresponds to that planned for BepiColombo/MMO and is different from those used in the other satellites. The analysis focuses on stray photoelectron currents flowing from these electrodes and a spacecraft body. Photoelectrons approaching the probe are commonly repelled by the guard, the potential of which is strongly biased negatively, and are subsequently affected by the probe potential. Consequently, the photoelectron current magnitude increases with increasing probe potential regardless of their origins, when the probe operates between the plasma and floating spacecraft potentials. The result indicates that both photoelectron currents from the spacecraft body and biased electrodes can be minimized by selecting the probe working potential as close as possible to the plasma potential. We also examine the photoelectron current dependence on the presence or absence of the guard electrode operation and confirm a positive effect of reducing the photoelectron current from the spacecraft. However, negative side effects of the guard operation enhance the photoelectron currents from the stub and guard, when the probe operates nearly at the plasma potential.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    Quantitative microscopic measurement of void distribution in shear bands in Zr_{66.7}Cu_{33.3} metallic glass (2011)
    American Physical Society (APS)
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    Publication Date: 2011-09-13
    Description: Author(s): A. C. Y. Liu, D. M. Paganin, L. Bourgeois, P. N. H. Nakashima, R. T. Ott, and M. J. Kramer We employ an electron phase retrieval technique in the transmission electron microscope to reconstruct the projected thickness maps of metallic glass specimens and measure the void distribution at a microscopic level. We examine an as-spun melt-spun Zr 66.7 Cu 33.3 glass and the shear bands formed in t... [Phys. Rev. B 84, 094201] Published Mon Sep 12, 2011
    Keywords: Inhomogeneous, disordered, and partially ordered systems
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
    Published by American Physical Society (APS)
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  • 5
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    PGC7 binds histone H3K9me2 to protect against conversion of 5mC to 5hmC in early embryos (2012)
    Nature Publishing Group (NPG)
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    Publication Date: 2012-06-23
    Description: The modification of DNA by 5-methylcytosine (5mC) has essential roles in cell differentiation and development through epigenetic gene regulation. 5mC can be converted to another modified base, 5-hydroxymethylcytosine (5hmC), by the tet methylcytosine dioxygenase (Tet) family of enzymes. Notably, the balance between 5hmC and 5mC in the genome is linked with cell-differentiation processes such as pluripotency and lineage commitment. We have previously reported that the maternal factor PGC7 (also known as Dppa3, Stella) is required for the maintenance of DNA methylation in early embryogenesis, and protects 5mC from conversion to 5hmC in the maternal genome. Here we show that PGC7 protects 5mC from Tet3-mediated conversion to 5hmC by binding to maternal chromatin containing dimethylated histone H3 lysine 9 (H3K9me2) in mice. In addition, imprinted loci that are marked with H3K9me2 in mature sperm are protected by PGC7 binding in early embryogenesis. This type of regulatory mechanism could be involved in DNA modifications in somatic cells as well as in early embryos.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nakamura, Toshinobu -- Liu, Yu-Jung -- Nakashima, Hiroyuki -- Umehara, Hiroki -- Inoue, Kimiko -- Matoba, Shogo -- Tachibana, Makoto -- Ogura, Atsuo -- Shinkai, Yoichi -- Nakano, Toru -- England -- Nature. 2012 Jun 3;486(7403):415-9. doi: 10.1038/nature11093.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Pathology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan. tnakamura@nagahama-i-bio.ac.jp〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22722204" target="_blank"〉PubMed〈/a〉
    Keywords: 5-Methylcytosine/*metabolism ; Animals ; Chromatin/chemistry/metabolism ; Cytosine/*analogs & derivatives/metabolism ; DNA Methylation ; DNA-Binding Proteins/metabolism ; Embryo, Mammalian/embryology/*metabolism ; Embryonic Development ; Female ; Genomic Imprinting/genetics ; Histones/*chemistry/*metabolism ; Lysine/chemistry/metabolism ; Male ; Methylation ; Mice ; Protein Binding/drug effects ; Proto-Oncogene Proteins/metabolism ; RNA, Long Noncoding ; RNA, Untranslated/genetics ; Repressor Proteins/*metabolism ; Spermatozoa/metabolism ; ras-GRF1/genetics
    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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  • 6
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    Change in the microstructure and mechanical properties of drawn pearlitic steel with low-temperature aging (2017)
    Institute of Physics (IOP)
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    Publication Date: 2017-08-01
    Description: Hydrogen embrittlement is a serious problem in high-strength steels. Drawn pearlitic steel shows excellent resistance to hydrogen embrittlement despite its high strength, and aging treatment at a low temperature can simultaneously improve its strength and hydrogen-embrittlement resistance. To clarify the mechanism for this we have used thermal desorption analysis (TDA) and the newly developed precession electron diffraction analysis method in the transmission electron microscope. After aging at 100 °C for 10 min, the amount of hydrogen seen amount on the TDA curve reduced at around 100 °C. In contrast, when aging was performed at 300 °C, the hydrogen amount further reduced at around 100 °C and the unevenly deformed lamellar ferrite zone was locally recovered. For the samples that were aged at the low temperature, we confirmed that their yield strength and relaxation stress ratios increased simultaneously with improvement in the hydrogen-embrittlement property. We infer that segr...
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
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  • 7
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    Genetic evidence that protein synthesis is required for the circadia clock of neurospora (1981)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1981-04-17
    Description: Small doses of cycloheximide given at intervals (pulses) cause phase shifts of the circadian clock of Neurospora. The effects of this drug on the clock are mediated through its inhibition of protein synthesis, since two cycloheximide-resistant mutants whose 80S ribosomes are resistant to cycloheximide showed no phase shift after exposure to the durg.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nakashima, H -- Perlman, J -- Feldman, J F -- New York, N.Y. -- Science. 1981 Apr 17;212(4492):361-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17792092" 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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  • 8
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    The structure of arthropod hemocyanins (1985)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1985-08-09
    Description: Hemocyanins are large multi-subunit copper proteins that transport oxygen in many arthropods and molluscs. Comparison of the amino acid sequence data for seven different subunits of arthropod hemocyanins from crustaceans and chelicerates shows many highly conserved residues and extensive regions of near identity. This correspondence can be matched closely with the three domain structure established by x-ray crystallography for spiny lobster hemocyanin. The degree of identity is particularly striking in the second domain of the subunit that contains the six histidines which ligate the two oxygen-binding copper atoms. The polypeptide architecture of spiny lobster hemocyanin appears to be the same in all arthropods. This structure must therefore be at least as old as the estimated time of divergence of crustaceans and chelicerates, about 540 to 600 million years ago.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Linzen, B -- Soeter, N M -- Riggs, A F -- Schneider, H J -- Schartau, W -- Moore, M D -- Yokota, E -- Behrens, P Q -- Nakashima, H -- Takagi, T -- GM 21314/GM/NIGMS NIH HHS/ -- GM 28410/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1985 Aug 9;229(4713):519-24.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/4023698" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Arachnida/genetics ; *Arthropods/genetics ; Binding Sites ; Biological Evolution ; Chemical Phenomena ; Chemistry ; Copper ; Crustacea/genetics ; *Hemocyanin/genetics ; Models, Molecular ; Protein Conformation ; Species Specificity
    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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    Plasma particle simulations of wake formation behind a spacecraft with thin wire booms (2013)
    Wiley
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    Publication Date: 2013-09-03
    Description: [1]  Double-probe electric field sensors installed on scientific spacecraft are often deployed using wire booms with radii much less than typical Debye lengths of magnetospheric plasmas (millimeters compared to tens of meters). However, in tenuous and coldstreaming plasmas seen in the polar cap and lobe regions, the wire booms, electrically grounded at the spacecraft, have a high positive potential due to photoelectron emission and can strongly scatter approaching ions. Consequently, an electrostatic wake formed behind the spacecraft is further enhanced by the presence of the wire booms. We reproduce this process for the case of the Cluster satellite by performing plasma particle-in-cell (PIC) simulations, which include the effects of both the spacecraft body and the wire booms in a simultaneous manner. The simulations reveal that the effective thickness of the booms for the Cluster Electric Field and Wave (EFW) instrument is magnified from its real diameter (2.2mm) to several meters, when the spacecraft potential is at tens of volts. Such booms enhance the wake electric field magnitude by a factor of 1.5 - 2 depending on the spacecraft potential, and play a principal role in explaining the in situ Cluster EFW datashowing sinusoidal spurious electric fields with about 10mV/m amplitude. The boom effects are quantified by comparing PIC simulations with and without wire booms and also by examining the wake formation for various spacecraft potentials.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
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    Dependence of generation of whistler-mode chorus emissions on the temperature anisotropy and density of energetic electrons in the Earth's inner magnetosphere (2018)
    Wiley
    Details
    Publication Date: 2018-01-24
    Description: We carry out a series of self-consistent electron hybrid code simulations for the dependence of chorus generation process on the temperature anisotropy and density of energetic electrons in the Earth's inner magnetosphere. We use the same magnetic field gradient in the simulation system and different temperature anisotropy A T for the initial distribution of energetic electrons at the magnetic equator. We conduct 6 sets of simulations for different A T from 4 to 9, changing the initial number density N h of energetic electrons at the equator in each set of simulations. By analyzing the spectra obtained in the simulation results, we identify chorus elements with rising tones in the results for higher N h but no distinct chorus in smaller N h . We compare the simulation results with estimations of the threshold and optimum amplitude proposed by the nonlinear wave growth theory. We find that the chorus generation processes reproduced in the simulation results are consistently explained by the theoretical estimates. We also compare the simulation results with linear growth rates for all simulation runs. We find clear disagreement between the spectral characteristics of reproduced chorus and the predictions by the linear theory. The present study clarifies that the spectra of chorus are essentially different from those predicted by the linear theory and are determined fully by nonlinear processes of wave-particle interactions in the chorus generation region.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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