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  • 1
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    Power-dependent spin amplification in (In, Ga)As/GaAs quantum well via Pauli blocking by tunnel-coupled quantum dot ensembles (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-04-12
    Description: Power-dependent time-resolved optical spin orientation measurements were performed on In 0.1 Ga 0.9 As quantum well (QW) and In 0.5 Ga 0.5 As quantum dot (QD) tunnel-coupled structures with an 8-nm-thick GaAs barrier. A fast transient increase of electron spin polarization was observed at the QW ground state after circular-polarized pulse excitation. The temporal maximum of polarization increased with increasing pumping fluence owing to enhanced spin blocking in the QDs, yielding a highest amplification of 174% with respect to the initial spin polarization. Further elevation of the laser power gradually quenched the polarization dynamics, which was induced by saturated spin filling of both the QDs and the QW phase spaces.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    CTRP6 is an endogenous complement regulator that can effectively treat induced arthritis (2015)
    Springer Nature
    Details
    Publication Date: 2015-09-27
    Description: Article The complement system contributes to chronic inflammatory diseases. Here the authors show that CRTP6 suppresses the alternative complement pathway and reverses rheumatoid arthritis in a mouse model of the disease. Nature Communications doi: 10.1038/ncomms9483 Authors: Masanori A. Murayama, Shigeru Kakuta, Asuka Inoue, Naoto Umeda, Tomo Yonezawa, Takumi Maruhashi, Koichiro Tateishi, Harumichi Ishigame, Rikio Yabe, Satoshi Ikeda, Akimasa Seno, Hsi-Hua Chi, Yuriko Hashiguchi, Riho Kurata, Takuya Tada, Sachiko Kubo, Nozomi Sato, Yang Liu, Masahira Hattori, Shinobu Saijo, Misao Matsushita, Teizo Fujita, Takayuki Sumida, Yoichiro Iwakura
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 3
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    Polycrystallinity of green rust minerals and their synthetic analogs: Implications for particle formation and reactivity in complex systems (2015)
    Mineralogical Society of America
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    Publication Date: 2015-10-02
    Description: We demonstrate in this study that natural green rust nanoparticles and their synthetic analogs can be complex polycrystalline phases composed of crystallites only a few nanometers in size, and they often include nanometer-sized regions of amorphous material. The natural green rusts are Zn-bearing pseudo-hexagonal platelets previously identified by us in the contaminated mine drainage of the former Ronneburg uranium mine in Germany ( Johnson et al. 2014 ). We also identified Ni- and Cu-bearing green rust platelets in the sediment underlying the drainage outflow 20 m downstream, and, using dark-field transmission electron microscopy (DF-TEM), found that these natural green rusts are not usually structurally coherent single crystals. Synthetic sulfate green rusts are also polycrystalline and composed of crystallites of only a few nanometers in size, though different synthesis conditions produced different patterns of polycrystallinity. While pseudo-hexagonal platelets are the typical morphology of green rust, we also synthesized green rust nanorods, which have not previously been reported. In addition to the known characteristics of green rusts (including a very large aspect ratio and surface area to volume ratio, and the redox properties allowed by the structural mixture of Fe 2+ and Fe 3+ ), these polycrystalline platelets exhibit a high abundance of defect sites and likely a rough surface topography. The combination of these characteristics has important implications for the reactivity of green rust with biogeochemical interfaces in natural and anthropogenic systems.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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  • 4
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    Altered CpG methylation in sporadic Alzheimer's disease is associated with APP and MAPT dysregulation (2014)
    Oxford University Press
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    Publication Date: 2014-01-11
    Description: The hallmark of Alzheimer's disease (AD) pathology is an accumulation of amyloid β (Aβ) and phosphorylated tau, which are encoded by the amyloid precursor protein (APP) and microtubule-associated protein tau ( MAPT ) genes, respectively. Less than 5% of all AD cases are familial in nature, i.e. caused by mutations in APP , PSEN1 or PSEN2 . Almost all mutations found in them are related to an overproduction of Aβ 1–42 , which is prone to aggregation. While these genes are mutation free, their function, or those of related genes, could be compromised in sporadic AD as well. In this study, pyrosequencing analysis of post-mortem brains revealed aberrant CpG methylation in APP , MAPT and GSK3B genes of the AD brain. These changes were further evaluated by a newly developed in vitro -specific DNA methylation system, which in turn highlighted an enhanced expression of APP and MAPT . Cell nucleus sorting of post-mortem brains revealed that the methylation changes of APP and MAPT occurred in both neuronal and non-neuronal cells, whereas GSK3B was abnormally methylated in non-neuronal cells. Further analysis revealed an association between abnormal APP CpG methylation and apolipoprotein E 4 allele ( APOE 4)-negative cases. The presence of a small number of highly methylated neurons among normal neurons contribute to the methylation difference in APP and MAPT CpGs, thus abnormally methylated cells could compromise the neural circuit and/or serve as ‘seed cells’ for abnormal protein propagation. Our results provide a link between familial AD genes and sporadic neuropathology, thus emphasizing an epigenetic pathomechanism for sporadic AD.
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
    Published by Oxford University Press
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  • 5
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    Anomalous spectral dependence of optical polarization and its impact on spin detection in InGaAs/GaAs quantum dots (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-10-02
    Description: We show that circularly polarized emission light from InGaAs/GaAs quantum dot (QD) ensembles under optical spin injection from an adjacent GaAs layer can switch its helicity depending on emission wavelengths and optical excitation density. We attribute this anomalous behavior to simultaneous contributions from both positive and negative trions and a lower number of photo-excited holes than electrons being injected into the QDs due to trapping of holes at ionized acceptors and a lower hole mobility. Our results call for caution in reading out electron spin polarization by optical polarization of the QD ensembles and also provide a guideline in improving efficiency of spin light emitting devices that utilize QDs.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 6
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    Temperature-dependent spin injection dynamics in InGaAs/GaAs quantum well-dot tunnel-coupled nanostructures (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-03-16
    Description: Time-resolved optical spin orientation spectroscopy was employed to investigate the temperature-dependent electron spin injection in In 0.1 Ga 0.9 As quantum well (QW) and In 0.5 Ga 0.5 As quantum dots (QDs) tunnel-coupled nanostructures with 4, 6, and 8 nm-thick GaAs barriers. The fast picosecond-ranged spin injection from QW to QD excited states (ES) was observed to speed up with temperature, as induced by pronounced longitudinal-optical (LO)-phonon-involved multiple scattering process, which contributes to a thermally stable and almost fully spin-conserving injection within 5–180 K. The LO-phonon coupling was also found to cause accelerated electron spin relaxation of QD ES at elevated temperature, mainly via hyperfine interaction with random nuclear field.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 7
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    Effect of a Phonon Bottleneck on Exciton and Spin Generation in Self-Assembled ${\mathrm{In}}_{1−x}{\mathrm{Ga}}_{x}\mathrm{As}$ Quantum Dots (2018)
    American Physical Society (APS)
    Details
    Publication Date: 2018-04-27
    Description: Author(s): Y. Q. Huang, I. A. Buyanova, X. J. Yang, A. Murayama, and W. M. Chen Semiconductor quantum dots (QDs) hold great potential for solid-state light-emitting devices and optical and spin-based quantum information processing, but the efficiency of QD-based spin LEDs remains limited, and their physics not fully understood. Using tunable laser spectroscopy, the authors discover that here an intrinsic obstacle to spin generation is p h o n o n b o t t l e n e c k , a lack of phonon-mediated relaxation pathways that can arise in a zero-dimensional system. This insight provides design rules for energy-level engineering in spin-optoelectronic applications of QDs, yielding about a threefold increase in spin generation efficiency, even at elevated temperatures. [Phys. Rev. Applied 9, 044037] Published Thu Apr 26, 2018
    Electronic ISSN: 2331-7019
    Topics: Physics
    Published by American Physical Society (APS)
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  • 8
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    NEURONAL DEVELOPMENT. Glycerophospholipid regulation of modality-specific sensory axon guidance in the spinal cord (2015)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2015-09-01
    Description: Glycerophospholipids, the structural components of cell membranes, have not been considered to be spatial cues for intercellular signaling because of their ubiquitous distribution. We identified lyso-phosphatidyl-beta-D-glucoside (LysoPtdGlc), a hydrophilic glycerophospholipid, and demonstrated its role in modality-specific repulsive guidance of spinal cord sensory axons. LysoPtdGlc is locally synthesized and released by radial glia in a patterned spatial distribution to regulate the targeting of nociceptive but not proprioceptive central axon projections. Library screening identified the G protein-coupled receptor GPR55 as a high-affinity receptor for LysoPtdGlc, and GPR55 deletion or LysoPtdGlc loss of function in vivo caused the misallocation of nociceptive axons into proprioceptive zones. These findings show that LysoPtdGlc/GPR55 is a lipid-based signaling system in glia-neuron communication for neural development.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Guy, Adam T -- Nagatsuka, Yasuko -- Ooashi, Noriko -- Inoue, Mariko -- Nakata, Asuka -- Greimel, Peter -- Inoue, Asuka -- Nabetani, Takuji -- Murayama, Akiho -- Ohta, Kunihiro -- Ito, Yukishige -- Aoki, Junken -- Hirabayashi, Yoshio -- Kamiguchi, Hiroyuki -- New York, N.Y. -- Science. 2015 Aug 28;349(6251):974-7. doi: 10.1126/science.aab3516.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. ; RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. Lipid Biology Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. ; Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Sendai, Miyagi 980-8578, Japan. Japan Science and Technology Agency, Precursory Research for Embryonic Science and Technology (PRESTO), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan. ; Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan. ; Synthetic Cellular Chemistry Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. ; Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Sendai, Miyagi 980-8578, Japan. Japan Agency for Medical Research and Development, Core Research for Evolutional Science and Technology (AMED-CREST), 1-7-1 Otemachi, Chiyoda, Tokyo 100-0004, Japan. ; RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. kamiguchi@brain.riken.jp hirabaya@riken.jp.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26315437" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Axons/*physiology ; Chick Embryo ; Coculture Techniques ; Ganglia, Spinal/*cytology/physiology ; Gene Knockout Techniques ; Glycerophospholipids/analysis/metabolism/*physiology ; Glycolipids/analysis/*physiology ; Mice ; Nerve Growth Factor/pharmacology ; Neuroglia/*physiology ; Nociceptors/*physiology ; Receptor, trkA/metabolism ; Receptor, trkC/metabolism ; Receptors, Cannabinoid/genetics/*physiology ; Spinal Cord/*cytology/*embryology ; Tissue Culture Techniques
    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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    Time-resolved measurements of Cooper-pair radiative recombination in InAs quantum dots (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-08-18
    Description: We studied InAs quantum dots (QDs) where electron Cooper pairs penetrate from an adjacent niobium (Nb) superconductor with the proximity effect. With time-resolved luminescence measurements at the wavelength around 1550 nm, we observed luminescence enhancement and reduction of luminescence decay time constants at temperature below the superconducting critical temperature ( T C ) of Nb. On the basis of these measurements, we propose a method to determine the contribution of Cooper-pair recombination in InAs QDs. We show that the luminescence enhancement measured below T C is well explained with our theory including Cooper-pair recombination.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 10
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    Optical observation of superconducting density of states in luminescence spectra of InAs quantum dots (2015)
    American Physical Society (APS)
    Details
    Publication Date: 2015-07-29
    Description: Author(s): S. S. Mou, H. Irie, Y. Asano, K. Akahane, H. Nakajima, H. Kumano, M. Sasaki, A. Murayama, and I. Suemune We study luminescence spectra observed from InAs quantum dots (QDs) embedded in an n -type InGaAs-based heterostructure, where electron Cooper pairs penetrate from an adjacent niobium (Nb) superconductor with the proximity effect. Below the superconducting (SC) critical temperature of Nb, we observe … [Phys. Rev. B 92, 035308] Published Mon Jul 27, 2015
    Keywords: Semiconductors II: surfaces, interfaces, microstructures, and related topics
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
    Published by American Physical Society (APS)
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