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  • 1
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    Observations of global ionospheric responses to the 2009 stratospheric sudden warming event by FORMOSAT-3/COSMIC (2012)
    Wiley
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    Publication Date: 2012-06-29
    Description: The global ionospheric response to a stratospheric sudden warming (SSW) is studied using three-dimensional electron density maps derived from radio occultation observations of FORMOSAT-3/COSMIC during the 2009 SSW periods. Results show that the ionospheric electron density at EIA crests exhibit a morning/early afternoon increase followed by an afternoon decrease and an evening increase, indicative of a semidiurnal component during the SSW period, which is consistent with recent studies. The latitude-altitude electron density slice maps show that the SSW related modifications of the equatorial plasma fountain interact with the existing summer-to-winter neutral winds and resulting in a north–south asymmetry. The global ionospheric response shows a clear longitudinal dependence in the equatorial plasma fountain enhancement during morning/early afternoon, inferred from the duration of the equatorial ionization anomaly (EIA) enhancement. Following the enhancement, prominent global EIA reductions resulting from the equatorial plasma fountain weakening in the afternoon sector are seen. The ionospheric response to the 2009 SSW event is also compared with the usual seasonal variation during January–February 2007. Instead of showing the electron density increase in the northern hemisphere and decrease in the southern hemisphere as the usual seasonal variation does, the SSW period ionosphere shows prominent global electron density reductions in the afternoon period during the 2009 SSW event.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Revisiting the Modulations of Ionospheric Solar and Lunar Migrating Tides During the 2009 Stratospheric Sudden Warming by Using Global Ionosphere Specification (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract In this study, Global Ionosphere Specification (GIS) based on Gauss‐Markov Kalman filter assimilation of slant total electron content observed from ground‐based global positioning system receivers and space‐based radio occultation instrumentations is applied to investigate the ionospheric day‐to‐day tidal variability during the 2009 stratospheric sudden warming (SSW) period. Including the improved daily three‐dimensional global electron density distribution from GIS enables us to retrieve the daily solar tidal solution by using least squares tidal analysis. We find prominent reductions followed by enhancements in the amplitude of the solar semidiurnal migrating tide (SW2) after the peak warming, with recurrent phase variations occurring at low magnetic latitudes over a period of about 15 days. This is close to the beating period (15.13 day) between SW2 and lunar semidiurnal (M2), thus suggesting the existence of strong M2, and our results demonstrate that the intensification of M2 exists only during the SSW period. Additionally, M2 acts as the key contributor to make the semidiurnal ionospheric perturbations shift toward later local times. Our tidal analyses of daily GIS thus provide evidence for the combined impact of amplitudes and phases of the SW2 and M2 in producing semidiurnal variations in ionosphere during the 2009 SSW.
    Print ISSN: 1539-4964
    Electronic ISSN: 1542-7390
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Observational evidence of ionospheric migrating tide modification during the 2009 stratospheric sudden warming (2012)
    Wiley
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    Publication Date: 2012-01-19
    Description: In this paper, modifications of the ionospheric tidal signatures during the 2009 stratospheric sudden warming (SSW) event are studied by applying atmospheric tidal analysis to ionospheric electron densities observed using radio occultation soundings of FORMOSAT-3/COSMIC. The tidal analysis indicates that the zonal mean and major migrating tidal components (DW1, SW2 and TW3) decrease around the time of the SSW, with 1.5–4 hour time shifts in the daily time of maximum around EIA and middle latitudes. The typical ionospheric SSW signature: a semi-diurnal variation of the ionospheric electron density, featuring an earlier commencement and subsidence of EIA, can be reproduced by differencing the migrating tides before and during the SSW period. Our results also indicate that the migrating tides represent ∼80% of the ionospheric tidal components at specific longitudes, suggesting that modifications of the migrating tides may be the major driver for producing ionospheric changes observed during SSW events, accounting for greater variability than the nonmigrating tides that have been the focus of previous studies.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    Ionospheric response to 2009 Sudden Stratospheric Warming in the northern hemisphere (2014)
    Wiley
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    Publication Date: 2014-11-10
    Description: We study the behavior of the F region ionosphere in the northern hemisphere during the Sudden Stratospheric Warming period of 19-30 January 2009, by using FORMOSAT-3/COSMIC (F3/C) ionosphere data (NmF 2 , hmF 2 , and height profile). We concentrated our study in the longitude bands 30° E - 30° W, as well as 150° E - 150° W, where no detailed study has been reported so far. At low magnetic latitude, the NmF 2 decreases except during 09-12 LT : in the latitude zone of 20-40 ° NmF 2 shows an increase of 30 % during 09-12 LT. At higher magnetic latitude the NmF 2 shows an increase during daytime, and a reduction in the evening (21- 03 LT). There is a latitude zone where NmF 2 does not change. The latitude seems to correspond to the latitude where atmospheric temperature does not change. The behavior of the NmF 2 seems to suggest a reduction of neutral density in low latitude, and increase of neutral density in higher latitude. During the period of DOY 25-31, the NmF 2 shows a drastic reduction only during 06-09 LT in low latitudes, which is slightly away from geomagnetic equator. This special feature which occurred during declining phase of the SSW might be explained as due to enhanced dynamo electric field. The study suggests global change of the thermosphere including dynamo region, in spite of the fact that SSW is a high latitude phenomenon which occurred much below the height region of thermosphere.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Monoglycosylated HA is a cross-strain flu vaccine [Applied Biological Sciences] (2014)
    National Academy of Sciences
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    Publication Date: 2014-02-19
    Description: The 2009 H1N1 pandemic and recent human cases of H5N1, H7N9, and H6N1 in Asia highlight the need for a universal influenza vaccine that can provide cross-strain or even cross-subtype protection. Here, we show that recombinant monoglycosylated hemagglutinin (HAmg) with an intact protein structure from either seasonal or pandemic H1N1...
    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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    Theoretical study of the ionospheric plasma cave in the equatorial ionization anomaly region (2014)
    Wiley
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    Publication Date: 2014-11-18
    Description: This paper investigates the physical mechanism of an unusual equatorial electron density structure, plasma cave, located underneath the equatorial ionization anomaly by using theoretical simulations. The simulation results provide important new understanding of the dynamics of the equatorial ionosphere. It has been suggested previously that unusual drifts might be responsible for the observed plasma cave structure, but model simulations in this paper suggest that the more likely cause is latitudinal meridional neutral wind variations. The neutral winds are featured by two divergent wind regions at off-equator latitudes and a convergent wind region around the magnetic equator, resulting in plasma divergences and convergence, respectively, to form the plasma caves structure. The tidal-decomposition analysis further suggests that the cave related meridional neutral winds and the intensity of plasma cave are highly associated with the migrating terdiurnal tidal component of the neutral winds.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Exploiting a natural conformational switch to engineer an interleukin-2 'superkine' (2012)
    Nature Publishing Group (NPG)
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    Publication Date: 2012-03-27
    Description: The immunostimulatory cytokine interleukin-2 (IL-2) is a growth factor for a wide range of leukocytes, including T cells and natural killer (NK) cells. Considerable effort has been invested in using IL-2 as a therapeutic agent for a variety of immune disorders ranging from AIDS to cancer. However, adverse effects have limited its use in the clinic. On activated T cells, IL-2 signals through a quaternary 'high affinity' receptor complex consisting of IL-2, IL-2Ralpha (termed CD25), IL-2Rbeta and IL-2Rgamma. Naive T cells express only a low density of IL-2Rbeta and IL-2Rgamma, and are therefore relatively insensitive to IL-2, but acquire sensitivity after CD25 expression, which captures the cytokine and presents it to IL-2Rbeta and IL-2Rgamma. Here, using in vitro evolution, we eliminated the functional requirement of IL-2 for CD25 expression by engineering an IL-2 'superkine' (also called super-2) with increased binding affinity for IL-2Rbeta. Crystal structures of the IL-2 superkine in free and receptor-bound forms showed that the evolved mutations are principally in the core of the cytokine, and molecular dynamics simulations indicated that the evolved mutations stabilized IL-2, reducing the flexibility of a helix in the IL-2Rbeta binding site, into an optimized receptor-binding conformation resembling that when bound to CD25. The evolved mutations in the IL-2 superkine recapitulated the functional role of CD25 by eliciting potent phosphorylation of STAT5 and vigorous proliferation of T cells irrespective of CD25 expression. Compared to IL-2, the IL-2 superkine induced superior expansion of cytotoxic T cells, leading to improved antitumour responses in vivo, and elicited proportionally less expansion of T regulatory cells and reduced pulmonary oedema. Collectively, we show that in vitro evolution has mimicked the functional role of CD25 in enhancing IL-2 potency and regulating target cell specificity, which has implications for immunotherapy.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3338870/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3338870/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Levin, Aron M -- Bates, Darren L -- Ring, Aaron M -- Krieg, Carsten -- Lin, Jack T -- Su, Leon -- Moraga, Ignacio -- Raeber, Miro E -- Bowman, Gregory R -- Novick, Paul -- Pande, Vijay S -- Fathman, C Garrison -- Boyman, Onur -- Garcia, K Christopher -- AR050942/AR/NIAMS NIH HHS/ -- GM07365/GM/NIGMS NIH HHS/ -- R01 AI051321/AI/NIAID NIH HHS/ -- R01 AI051321-05/AI/NIAID NIH HHS/ -- R01 CA065237/CA/NCI NIH HHS/ -- R01-GM062868/GM/NIGMS NIH HHS/ -- R01AI51321/AI/NIAID NIH HHS/ -- R37 AI051321/AI/NIAID NIH HHS/ -- T32 AI007290/AI/NIAID NIH HHS/ -- U01 DK078123/DK/NIDDK NIH HHS/ -- U19 AI 082719/AI/NIAID NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2012 Mar 25;484(7395):529-33. doi: 10.1038/nature10975.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, California 94305, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22446627" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Binding Sites ; Cell Line ; Cell Proliferation ; Crystallography, X-Ray ; *Directed Molecular Evolution ; Humans ; Immunotherapy ; Interleukin-2/*chemistry/genetics/*immunology/pharmacology ; Interleukin-2 Receptor alpha Subunit/chemistry/deficiency/immunology/metabolism ; Interleukin-2 Receptor beta Subunit/chemistry/metabolism ; Killer Cells, Natural/immunology ; Mice ; Mice, Inbred C57BL ; Models, Molecular ; Molecular Dynamics Simulation ; Mutant Proteins/*chemistry/genetics/*immunology/pharmacology ; Mutation ; Neoplasm Transplantation ; Neoplasms/drug therapy/immunology ; Phosphorylation ; Protein Conformation ; *Protein Engineering ; STAT5 Transcription Factor/metabolism ; Surface Plasmon Resonance ; T-Lymphocytes/cytology/immunology
    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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    Thermospheric tidal effects on the ionospheric Mid-latitude Summer Nighttime Anomaly using SAMI3 and TIEGCM (2013)
    Wiley
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    Publication Date: 2013-05-18
    Description: [1]  This paper is the first study to employ a three-dimensional physics based ionosphere model, SAMI3, coupled with the NCAR TIEGCM and GSWM to simulate the mesospheric and lower thermospheric tidal effects on the development of mid-latitude summer nighttime anomaly (MSNA). Using this coupled model, the diurnal variation of MSNA electron densities at 300 km altitude are simulated on both June solstice (DOY 167) and December solstice (DOY 350) in 2007. Results show successful reproduction of the southern hemisphere MSNA structure including the eastward drift feature of the southern MSNA, which is not reproduced by the default SAMI3 runs using the neutral winds provided by the empirical HWM93 neutral wind model. A linear least-squares algorithm for extracting tidal components is utilized to examine the major tidal component affecting the variation of southern MSNA. Results show that the standing diurnal oscillation (D0) component dominates the vertical neutral wind manifesting as a diurnal eastward wave-1 drift of the southern MSNA in the local time frame. We also find that the stationary planetary wave-1 (SPW1) component of vertical neutral wind can cause diurnal variation of the summer nighttime electron density enhancement around the mid-latitude ionosphere.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    Near-Surface Electronic Contribution to Semiconductor Elasticity (2017)
    American Physical Society (APS)
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    Publication Date: 2017-09-19
    Description: Author(s): J. T. Lin, P. D. Shuvra, S. McNamara, H. Gong, W. Liao, J. L. Davidson, K. M. Walsh, M. L. Alles, and B. W. Alphenaar Micro- and nanoelectromechanical systems (MEMS and NEMS) have clear advantages for space-based sensing and timing applications, but their operation in the face of strong radiation is not well understood. This work describes a mechanism whereby space radiation can impact a semiconductor’s elasticity, and hence an electromechanical device’s operation. It is shown that radiation-induced changes in carrier concentration at the surface result in long-term modification of the material’s mechanical constants—an important source of error for MEMS or NEMS resonators operating in high-radiation environments. [Phys. Rev. Applied 8, 034013] Published Mon Sep 18, 2017
    Electronic ISSN: 2331-7019
    Topics: Physics
    Published by American Physical Society (APS)
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  • 10
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    Equatorial plasma bubble generation / inhibition during 2015 St. Patrick's Day storm (2017)
    Wiley
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    Publication Date: 2017-08-01
    Description: All sky camera observations carried out over Taiwan showed intense equatorial plasma bubbles (EPB) in 630.0 nm airglow images on consecutive nights of 13-16 March, 2015, but was absent in the following night of 17 March when St. Patrick's Day magnetic storm occurred. Rate of total electron content (TEC) index by using Global Positioning System (GPS) network data also confirmed the absence of irregularities on the night 17 March. The results however revealed strong irregularities over Indian sector on the same night. Flux tube integrated Rayleigh-Taylor instability growth rates computed using the prior (forecast) state of Thermosphere-Ionosphere Electrodynamics General Circulation Model output after assimilating the GPS-TEC measurements also agree with the observations, showing smaller values over Taiwan and larger values over India on the night of 17 March. The ionospheric response to the storm over Taiwan that resulted in the apparent inhibition of EPB is investigated in this study by using the data assimilation output. Results indicate that on the night of the magnetic storm, pre-reversal enhancement of zonal electric field over Taiwan was weaker when compared to that over India. Further analysis suggests that the absence of enhancement in the zonal electric field could be due to westward penetration electric field in response to rapid northward turning of interplanetary magnetic field that occurred during the dusk period over Taiwan.
    Print ISSN: 1539-4964
    Electronic ISSN: 1542-7390
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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