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  • 1
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    Odin observations of Antarctic nighttime NO densities in the mesosphere – lower thermosphere and observations of a lower NO layer (2013)
    Wiley
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    Publication Date: 2013-06-11
    Description: [1]  The Optical Spectrograph and Infrared Imaging System (OSIRIS) on the Odin satellite currently has an eight-year dataset of nighttime Antarctic nitric oxide densities, [NO], in the mesosphere-lower thermosphere (MLT) region. In this work, the OSIRIS data are compared with a similar dataset from the Sub-Millimetre Radiometer (SMR), also on the Odin satellite. Both of the Odin datasets are compared with twilight [NO] from the Atmospheric Chemistry Experiment – Fourier Transform Spectrometer (ACE-FTS) on the SciSat-I satellite. Direct comparisons of OSIRIS and SMR profiles show large differences, indicating that the individual [NO] profiles of one or both datasets may not be valid. However, when comparing averaged [NO], variations on timescales of weeks-years in all three datasets are in good agreement and correspond to the 27-day and 11-year solar cycles. The averaged OSIRIS values are typically 10% greater than SMR and 30% greater than ACE-FTS, which are within the estimated OSIRIS systematic uncertainties. These results suggest that the satellite-derived datasets can be used for determining polar-mean NO climatology and variations on timescales of weeks-years. The OSIRIS and SMR nighttime datasets show that the [NO] peak height in the MLT decreases throughout the autumn, from an altitude near or above 100 km to a minimum altitude ranging from 90-95 km around winter solstice. A similar decrease in [NO] peak height is observed in modelled NO climatology from the Specified Dynamics – Whole Atmosphere Community Climate Model (SD-WACCM), although the SD-WACCM climatology exhibits a decrease throughout autumn from 107 km down to 102 km. The results suggest that global climate models require more sophisticated auroral forcing simulations in order to reproduce observed NO variations in this region.
    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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    Comparison of rotational temperature derived from ground-based OH airglow observations with TIMED/SABER to evaluate the Einstein Coefficients (2015)
    Wiley
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    Publication Date: 2015-10-29
    Description: Ground-based observations of the OH(9-4, 8-3, 6-2, 5-1, 3-0) band airglow over Xinglong, China (40°24’N, 117°35’E) from December 2011 to 2014 are used to calculate rotational temperatures. The temperatures are calculated using five commonly used Einstein coefficient datasets. The kinetic temperature from TIMED/SABER is completely independent of the OH rotational temperature. SABER temperatures are weighted vertically by weighting functions calculated for each emitting vibrational state from two SABER OH volume emission rate profiles. By comparing the ground-based OH rotational temperature with SABER's, five Einstein coefficient datasets are evaluated. The results show that temporal variations of the rotational temperatures are well correlated with SABER's; the linear correlation coefficients are higher than 0.72 but the slopes of the fit between the SABER and rotational temperatures are not equal to 1. The rotational temperatures calculated using each set of Einstein coefficients produce a different bias with respect to SABER; these are evaluated over each of the vibrational levels to assess the best match. It is concluded that rotational temperatures determined using any of the available Einstein coefficient datasets have systematic errors. However, of the five sets of coefficients, the rotational temperature derived with the Langhoff et al. [1986] set is most consistent with SABER. In order to get a set of optimal Einstein coefficients for rotational temperature derivation, we derive their ratios from ground-based OH spectra and SABER temperatures statistically using three years of data. The use of a standard set of Einstein coefficients will be beneficial for comparing rotational temperatures observed at different sites.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 3
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    Structures of RNA 3'-phosphate cyclase bound to ATP reveal the mechanism of nucleotidyl transfer and metal-assisted catalysis [Biochemistry] (2011)
    National Academy of Sciences
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    Publication Date: 2011-12-28
    Description: RNA 3′-phosphate cyclase (RtcA) synthesizes RNA 2′,3′ cyclic phosphate ends via three steps: reaction with ATP to form a covalent RtcA-(histidinyl-Nϵ)-AMP intermediate; transfer of adenylate to an RNA 3′-phosphate to form RNA(3′)pp(5′)A; and attack of the vicinal O2′ on the 3′-phosphorus to form a 2′,3′ cyclic phosphate and release AMP. Here we report the crystal structures of RtcA•ATP, RtcA•ATP•Mn2+, and RtcA•ATP•Co2+ substrate complexes and an RtcA•AMP product complex. Together with the structures of RtcA apoenzyme and the covalent RtcA–AMP intermediate, they illuminate the mechanism of nucleotidyl transfer, especially the stereochemical transitions at the AMP phosphate, the critical role of the metal in orienting the PPi leaving group of ATP during step 1, and the protein conformational switches that accompany substrate binding and product release. The octahedral metal complex of RtcA•ATP•Mn2+ includes nonbridging oxygens from each of the ATP phosphates, two waters, and Glu14 as the sole RtcA component. Whereas the RtcA adenylylation step is metal-catalyzed, the subsequent steps in the cyclization pathway are metal-independent.
    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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  • 4
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    A Climatology of Planetary Wave-Driven Mesospheric Inversion Layers in the Extratropical Winter (2014)
    Wiley
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    Publication Date: 2014-12-12
    Description: Mesospheric inversion layers (MILs) are a useful diagnostic to simultaneously investigate middle atmosphere radiation, chemistry, and dynamics in high-top general circulation models. Climatologies of long-lived extratropical winter MILs observed by the Microwave Limb Sounder (MLS) and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) are compared to MILs in the Whole Atmosphere Community Climate Model (WACCM). In general, MIL location, amplitude, and thickness statistics in WACCM are in good agreement with the observations, though WACCM middle and high latitude winter MILs occur 30%-50% more often than in MLS and SABER. This work suggests that planetary wave driven MILs may form as high as 90 km. In the winter, MILs display a wave-1 pattern in both hemispheres, forming most often over the region where the climatological winter stratospheric anticyclones occur. These MILs are driven by the decay of vertically propagating planetary waves in the mesospheric surf zone in both observations and in the model. At the base of polar inversions there is climatological local ascent and cooling situated atop the stratospheric anticyclones, which enhances the cold base of the MILs near 60 km and 120° E longitude.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 5
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    Global occurrence and chemical impact of stratospheric Blue Jets modeled with WACCM4 (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract In this work we present the first parameterizations of the global occurrence rate and chemical influence of Blue Jets, a type of Transient Luminous Event (TLE) taking place in the stratospheric region above thunderclouds. These parameterizations are directly coupled with five different lightning parameterizations implemented in the Whole Atmosphere Community Climate Model (WACCM4). We have obtained a maximum Blue Jet global occurrence rate of about 0.9 BJ per minute. The geographical occurrence of Blue Jets is closely related to the chosen lightning parameterization. Some previously developed local chemical models of Blue Jets predicted an important influence onto the stratospheric concentration of N2O, NOx and O3. We have used these results together with our global implementations of Blue Jets in WACCM4 to estimate their global chemical influence in the atmosphere. According to our results, Blue Jets can inject about 3.8 Tg N2O‐N yr−1 and 0.07 Tg NO‐N yr−1 near the stratosphere, where N2O‐N and NO‐N stand for the mass of nitrogen atoms in N2O and NO molecules, respectively. These production rates of N2O and NOx could have a direct impact on, for example, the acidity of rainwater or the greenhouse effect. We have found that Blue Jets could also slightly contribute to the depletion of stratospheric ozone. In particular, we have estimated that the maximum difference in the concentration of O3 at 30 km of altitude between simulations with and without Blue Jets can be about ‐5 % in Equatorial and Polar regions.
    Print ISSN: 2169-897X
    Electronic ISSN: 2169-8996
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    Post-traumatic stress disorder is associated with PACAP and the PAC1 receptor (2011)
    Nature Publishing Group (NPG)
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    Publication Date: 2011-02-26
    Description: Pituitary adenylate cyclase-activating polypeptide (PACAP) is known to broadly regulate the cellular stress response. In contrast, it is unclear if the PACAP-PAC1 receptor pathway has a role in human psychological stress responses, such as post-traumatic stress disorder (PTSD). Here we find, in heavily traumatized subjects, a sex-specific association of PACAP blood levels with fear physiology, PTSD diagnosis and symptoms in females. We examined 44 single nucleotide polymorphisms (SNPs) spanning the PACAP (encoded by ADCYAP1) and PAC1 (encoded by ADCYAP1R1) genes, demonstrating a sex-specific association with PTSD. A single SNP in a putative oestrogen response element within ADCYAP1R1, rs2267735, predicts PTSD diagnosis and symptoms in females only. This SNP also associates with fear discrimination and with ADCYAP1R1 messenger RNA expression in human brain. Methylation of ADCYAP1R1 in peripheral blood is also associated with PTSD. Complementing these human data, ADCYAP1R1 mRNA is induced with fear conditioning or oestrogen replacement in rodent models. These data suggest that perturbations in the PACAP-PAC1 pathway are involved in abnormal stress responses underlying PTSD. These sex-specific effects may occur via oestrogen regulation of ADCYAP1R1. PACAP levels and ADCYAP1R1 SNPs may serve as useful biomarkers to further our mechanistic understanding of PTSD.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3046811/" 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/PMC3046811/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ressler, Kerry J -- Mercer, Kristina B -- Bradley, Bekh -- Jovanovic, Tanja -- Mahan, Amy -- Kerley, Kimberly -- Norrholm, Seth D -- Kilaru, Varun -- Smith, Alicia K -- Myers, Amanda J -- Ramirez, Manuel -- Engel, Anzhelika -- Hammack, Sayamwong E -- Toufexis, Donna -- Braas, Karen M -- Binder, Elisabeth B -- May, Victor -- AG034504/AG/NIA NIH HHS/ -- DA019624/DA/NIDA NIH HHS/ -- HD27468/HD/NICHD NIH HHS/ -- M01RR00039/RR/NCRR NIH HHS/ -- MH071537/MH/NIMH NIH HHS/ -- P20RR16435/RR/NCRR NIH HHS/ -- R01 AG034504/AG/NIA NIH HHS/ -- R01 HD027468/HD/NICHD NIH HHS/ -- R01 HD027468-13/HD/NICHD NIH HHS/ -- UL1 TR000454/TR/NCATS NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2011 Feb 24;470(7335):492-7. doi: 10.1038/nature09856.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA. kressle@emory.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21350482" target="_blank"〉PubMed〈/a〉
    Keywords: Amygdala/metabolism ; Animals ; Conditioning, Classical/physiology ; CpG Islands/genetics ; DNA Methylation ; Estrogens/metabolism/pharmacology ; Fear/physiology ; Female ; Gene Expression Regulation/drug effects ; Genetic Association Studies ; Genetic Predisposition to Disease/*genetics ; Humans ; Male ; Mice ; Pituitary Adenylate Cyclase-Activating Polypeptide/*blood/chemistry ; Polymorphism, Single Nucleotide/genetics ; RNA, Messenger/analysis/biosynthesis/genetics ; Rats ; Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I/*genetics ; Response Elements/genetics ; Septal Nuclei/drug effects/metabolism ; Sex Characteristics ; Stress Disorders, Post-Traumatic/*blood/*genetics/physiopathology/psychology
    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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  • 7
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    Satellite observations of ozone in the upper mesosphere (2013)
    Wiley
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    Publication Date: 2013-05-02
    Description: [1]  Ozone profiles in the upper mesosphere (70-100 km) retrieved from nine instruments are compared. Ozone from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument is used as the basis of comparison. Other measurements arefrom the Halogen Occultation Experiment (HALOE), the High Resolution Doppler Imager (HRDI), the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), the Global Ozone Monitoring by Occultation of Stars (GOMOS), the Atmospheric Chemistry Experiment - Fourier Transform Spectrometer (ACE-FTS), the Solar Occultation For Ice Experiment (SOFIE), the Optical Spectrograph and InfraRed Imaging System (OSIRIS), and the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES). Comparisons of each dataset with SABER using coincident profiles indicate agreement in the basic vertical profile of ozone but also some systematic differences in daytime ozone. Ozone from the SABER 9.6  μ m channel is higher than the other measurements over the altitude range 60-80 km by 20-50%. Nighttime comparisons indicate better relative agreement (〈10% difference). Taking all the data, not limited to coincidences, shows the global and seasonal distributions of ozone in the upper mesosphere from each instrument. The average maximum in ozone mixing ratio is around 90-92 km during daytime and 95 km at night. There is a maximum in ozone density at night (~90 km) and during some hours of the day. The latitude structure of ozone has appreciable variations with season, particularly in the tropical upper mesosphere. The basic latitude-altitude structure of ozone depends on local time, even when the analysis is restricted to day-only observations.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
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    WACCM climate-chemistry sensitivity to sprite perturbations (2014)
    Wiley
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    Publication Date: 2014-05-24
    Description: Transient luminous events affect Earth's atmosphere between thunderstorm tops and the lower ionosphere through ion-neutral chemistry reactions. Particular emphasis has been given to sprites, with models and observations suggesting a capability of perturbing atmospheric nitrogen oxides at a local level, as it is known to occur for tropospheric lightning and laboratory air discharges. However, it is as yet unknown whether sprites can be a relevant source of nitrogen oxides for the upper atmosphere. In this paper, we study the sensitivity of the Whole Atmosphere Community Climate Model (WACCM) to sprite-like nitrogen oxide perturbations. We take a top-down approach to estimate what magnitude sprite-perturbations should have to become significant as compared to other relevant atmospheric processes and study the sensitivity of the model response within the given uncertainties. We show that, based on current predictions by sprite streamer chemistry models, sprites can perturb Tropical NOx at 70 km altitude between 0.015 ppbv (buried in the background variability) to 0.15 ppbv (about 20%), adopting a local NO x production per sprite of 1.5 ⋅ 10 23 and 1.5 ⋅ 10 24 molecules respectively at this altitude. Below the lowest of the adopted values, sprites are irrelevant at global scales. Sprite NO x may build up to significantly larger amounts locally above active thunderstorms, further aided by other transient luminous events and possibly terrestrial gamma-ray flashes. We also use model results to interpret the available observational studies and give recommendations for future campaigns.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 9
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    Nonmigrating tidal variability in the SABER/TIMED mesospheric ozone (2014)
    Wiley
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    Publication Date: 2014-05-17
    Description: This paper presents for the first time evidence showing nonmigrating tidal variations in the mesospheric ozone (O 3 ) derived from the SABER/TIMED for a full 11-year period, 2002-2012. The O 3 tidal fields are extracted from the data by the same method as the temperature tides have been derived. The spatial distribution and seasonal variability of the three strongest nonmigrating O 3 tidal variabilities, i.e. SW3, DW2 and DE3, are shown. They demonstrate repeatable presence each year. These O 3 tidal variations have large amplitudes at the seasons and latitudes for which the respective temperature (T) tides amplify, i.e. near the equator and during the equinoxes. The phases of the T and O 3 tidal signatures are out of phase above 95 km. This phase relationship no longer holds for tidal perturbations below about 90 km. The O 3 SW3 and DW2 tidal variations have similar interannual variabilities that appear to follow ENSO variability. The O 3 DE3 tidal field however has a clear biyearly interannual variability as the biyearly maxima correlate with the westerly phase of the QBO in tropical stratospheric winds but only up to 2008.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
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  • 10
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    The role of the solar irradiance variability in the evolution of the middle atmosphere during 2004-2009 (2013)
    Wiley
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    Publication Date: 2013-01-27
    Description: [1]  The recent measurements by the Spectral Irradiance Monitor (SIM) and the SOLar STellar Irradiance Comparison Experiment (SOLSTICE) on-board of the Solar Radiation and Climate Experiment (SORCE) satellite revealed the Spectral Solar Irradiance (SSI) changes in the ultraviolet (UV) between 2004 and 2009 to be several times higher than it was shown by all previous SSI measurements and reconstructions. In this paper we simulate the O 3 , OH, and temperature responses to solar irradiance variability, using four different SSI datasets trying to define which one gives the best agreement between the simulated and observed responses. Firstly, we apply the 1-D radiative-convective model with interactive photochemistry to determine the regions of the atmosphere where the O 3 , OH, and temperature are most sensitive to the spectrum discrepancies between the different SSI datasets. As the comparison with observations can only be made taking into account dynamics and all known forcings of the atmosphere, we then apply the 3-D Chemistry-Climate Model (CCM) model SOCOL to simulate the atmosphere evolution from May 2004 to February 2009. We compare the modeled OH, O 3 and temperature changes with atmospheric data measured by several space instruments. Overall the comparison shows that the atmospheric changes simulated with the 3-D SOCOL model driven by the SIM and SOLSTICE SSI are closest to the atmospheric measurements.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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