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Abstract
CONTEXT Collisions between cometary neutrals in the inner coma of a comet and cometary ions that have been picked up into the solar wind flow and return to the coma lead to the formation of a broad inner boundary known as a collisionopause. This boundary is produced by a combination of charge transfer and chemical reactions, both of which are important at the location of the collisionopause boundary. Four spacecraft measured ion densities and velocities in the inner region of comets, exploring the part of the coma where an ion-neutral collisionopause boundary is expected to form. AIMS The aims are to determine the dominant physics behind the formation of the ion-neutral collisionopause and to evaluate where this boundary has been observed by spacecraft. METHODS We evaluated observations from three spacecraft at four different comets to determine if a collisionopause boundary was observed based on the reported ion velocities. We compared the measured location of the ion-neutral collisionopause with measurements of the collision cross sections to evaluate whether chemistry or charge exchange are more important at the location where the collisionopause is observed. RESULTS Based on measurements of the cross sections for charge transfer and for chemical reactions, the boundary observed by Rosetta appears to be the location where chemistry becomes the more probable result of a collision between H2O and H2O+ than charge exchange. Comparisons with ion observations made by Deep Space 1 at 19P/Borrelly and Giotto at 1P/Halley and 26P/Grigg-Skjellerup show that similar boundaries were observed at 19P/Borrelly and 1P/Halley. The ion composition measurements made by Giotto at Halley confirm that chemistry becomes more important inside of this boundary and that electron-ion dissociative recombination is a driver for the reported ion pileup boundary.
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Affiliation(s)
- K E Mandt
- Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723
| | - A Eriksson
- Swedish Institute of Space Physics, POB 537, SE-751 21, Uppsala, Sweden
| | - A Beth
- Department of Physics, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom
| | - M Galand
- Department of Physics, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom
| | - E Vigren
- Swedish Institute of Space Physics, POB 537, SE-751 21, Uppsala, Sweden
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Luspay-Kuti A, Altwegg K, Berthelier JJ, Beth A, Dhooghe F, Fiethe B, Fuselier SA, Gombosi TI, Hansen KC, Hässig M, Livadiotis G, Mall U, Mandt KE, Mousis O, Petrinec SM, Rubin M, Trattner KJ, Tzou CY, Wurz P. Comparison of neutral outgassing of comet 67P/Churyumov-Gerasimenko inbound and outbound beyond 3 AU from ROSINA/DFMS. Astron Astrophys 2019; 630:A30. [PMID: 32699429 PMCID: PMC7375265 DOI: 10.1051/0004-6361/201833536] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
CONTEXT Pre-equinox measurements of comet 67P/Churyumov-Gerasimenko with the mass spectrometer ROSINA/DFMS on board the Rosetta spacecraft revealed a strongly heterogeneous coma. The abundances of major and various minor volatile species were found to depend on the latitude and longitude of the nadir point of the spacecraft. The observed time variability of coma species remained consistent for about three months up to equinox. The chemical variability could be generally interpreted in terms of surface temperature and seasonal effects superposed on some kind of chemical heterogeneity of the nucleus. AIMS We compare here pre-equinox (inbound) ROSINA/DFMS measurements from 2014 to measurements taken after the outbound equinox in 2016, both at heliocentric distances larger than 3 AU. For a direct comparison we limit our observations to the southern hemisphere. METHODS We report the similarities and differences in the concentrations and time variability of neutral species under similar insolation conditions (heliocentric distance and season) pre- and post-equinox, and interpret them in light of the previously published observations. In addition, we extend both the pre- and post-equinox analysis by comparing species concentrations with a mixture of CO2 and H2O. RESULTS Our results show significant changes in the abundances of neutral species in the coma from pre- to post-equinox that are indicative of seasonally driven nucleus heterogeneity. CONCLUSIONS The observed pre- and post-equinox patterns can generally be explained by the strong erosion in the southern hemisphere that moves volatile-rich layers near the surface.
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Affiliation(s)
- A Luspay-Kuti
- Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723, USA
| | - K Altwegg
- Physikalisches Institut, University of Bern, Sidlerstr. 5, 3012 Bern, Switzerland
- Center for Space and Habitability (CSH), Universität Bern, Sidlerstr. 5, 3012 Bern, Switzerland
| | - J J Berthelier
- Laboratoire Atmosphères, Milieux, Observations Spatiales, Institut Pierre Simon Laplace, CNRS, Université Pierre et Marie Curie, 4 avenue de Neptune, 94100 Saint-Maur, France
| | - A Beth
- Department of Physics/SPAT, Imperial College London, London SW7 2AZ, UK
| | - F Dhooghe
- Belgian Institute for Space Aeronomy, BIRA-IASB, Ringlaan 3, 1180 Brussels, Belgium
- Center for Plasma Astrophysics, K.U. Leuven, Celestijnenlaan 200D, 3001 Heverlee, Belgium
| | - B Fiethe
- Institute of Computer and Network Engineering (IDA), TU Braunschweig, Hans-Sommer-Strasse 66, 38106 Braunschweig, Germany
| | - S A Fuselier
- Space Science Directorate, Southwest Research Institute, 6220 Culebra Rd., San Antonio, TX 78228, USA
| | - T I Gombosi
- Department of Climate and Space Sciences and Engineering, University of Michigan, 2455 Hayward, Ann Arbor, MI 48109, USA
| | - K C Hansen
- Department of Climate and Space Sciences and Engineering, University of Michigan, 2455 Hayward, Ann Arbor, MI 48109, USA
| | - M Hässig
- Space Science Directorate, Southwest Research Institute, 6220 Culebra Rd., San Antonio, TX 78228, USA
| | - G Livadiotis
- Space Science Directorate, Southwest Research Institute, 6220 Culebra Rd., San Antonio, TX 78228, USA
| | - U Mall
- Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
| | - K E Mandt
- Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723, USA
| | - O Mousis
- Laboratoire d'Astrophysique de Marseille, CNRS, Aix Marseille Université, 13388 Marseille, France
| | - S M Petrinec
- Lockheed Martin Space Systems Advanced Technology Center, 3251 Hanover St., Palo Alto, CA 94304, USA
| | - M Rubin
- Physikalisches Institut, University of Bern, Sidlerstr. 5, 3012 Bern, Switzerland
| | - K J Trattner
- Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, 3665 Discovery Dr., Boulder, CO 80309, USA
| | - C-Y Tzou
- Physikalisches Institut, University of Bern, Sidlerstr. 5, 3012 Bern, Switzerland
| | - P Wurz
- Physikalisches Institut, University of Bern, Sidlerstr. 5, 3012 Bern, Switzerland
- Center for Space and Habitability (CSH), Universität Bern, Sidlerstr. 5, 3012 Bern, Switzerland
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Heritier KL, Altwegg K, Berthelier JJ, Beth A, Carr CM, De Keyser J, Eriksson AI, Fuselier SA, Galand M, Gombosi TI, Henri P, Johansson FL, Nilsson H, Rubin M, Simon Wedlund C, Taylor MGGT, Vigren E. On the origin of molecular oxygen in cometary comae. Nat Commun 2018; 9:2580. [PMID: 29968720 PMCID: PMC6030164 DOI: 10.1038/s41467-018-04972-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 06/05/2018] [Indexed: 11/09/2022] Open
Affiliation(s)
- K L Heritier
- Department of Physics, Imperial College London, Prince Consort Road, London, SW7 2AZ, UK.
| | - K Altwegg
- Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
| | | | - A Beth
- Department of Physics, Imperial College London, Prince Consort Road, London, SW7 2AZ, UK
| | - C M Carr
- Department of Physics, Imperial College London, Prince Consort Road, London, SW7 2AZ, UK
| | - J De Keyser
- BIRA-IASB, Royal Belgian Institute for Space Aeronomy, Ringlaan 3, Brussels, Belgium
| | - A I Eriksson
- Swedish Institute of Space Physics, Ångström Laboratory, Lägerhyddsvägen 1, 752 37, Uppsala, Sweden
| | - S A Fuselier
- Southwest Research Institute, P.O. Drawer 28510, San Antonio, TX, 78228-0510, USA.,University of Texas at San Antonio, San Antonio, TX, 78249, USA
| | - M Galand
- Department of Physics, Imperial College London, Prince Consort Road, London, SW7 2AZ, UK
| | - T I Gombosi
- Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI, 48109, USA
| | - P Henri
- LPC2E, CNRS, 3 Avenue de la recherche scientifique, 45071, Orléans, France
| | - F L Johansson
- Swedish Institute of Space Physics, Ångström Laboratory, Lägerhyddsvägen 1, 752 37, Uppsala, Sweden
| | - H Nilsson
- Swedish Institute of Space Physics, P.O. Box 812, 981 28, Kiruna, Sweden
| | - M Rubin
- Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
| | - C Simon Wedlund
- Department of Physics, University of Oslo, Sem Sælands vei 24, postbox 1048, 0317, Oslo, Norway
| | - M G G T Taylor
- European Space Agency, ESTEC, Keplerlaan 1, Noordwijk, 2200 AG, The Netherlands
| | - E Vigren
- LATMOS/IPSL-CNRS-UPMC-UVSQ, 94100, Saint-Maur, France
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Pilkis SJ, Walderhaug M, Murray K, Beth A, Venkataramu SD, Pilkis J, El-Maghrabi MR. 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase from rat liver. J Biol Chem 1983; 258:6135-41. [PMID: 6304027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Rat liver 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase was phosphorylated by [gamma-32P]ATP plus fructose-6-P or [2-32P]fructose-2,6-P2. The radioactivity co-migrated with homogeneous 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase during sodium dodecyl sulfate-disc gel electrophoresis and the phosphoenzyme was acid-labile and base-stable. Hydrolysis of the phosphate group from phosphoenzyme prepared with either donor and the hydrolysis of their tryptic phosphopeptides depended on pH similarly. The pH dependence suggested that phosphate was linked to the N3 of a histidine residue. Co-electrophoresis and co-chromatography of alkaline hydrolysates of the labeled phosphoenzyme prepared from either substrate allowed the definitive identification of 3-phosphohistidine in the degradation products. Modification of the enzyme with diethylpyrocarbonate inactivated both the phosphotransferase and phosphohydrolase activities and suppressed the phosphorylation of the enzyme by ATP and fructose-6-P or by fructose-2,6-P2. Trypsin digestion of the phosphoenzyme formed upon incubation with ATP or fructose-2,6-P2 yielded an identical phosphopeptide after high pressure liquid chromatography. All the above data are consistent with this enzyme catalyzing both phosphohydrolase and phosphotransferase reactions with the mediation of phosphohistidine in the reaction scheme(s).
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Glöggler KG, Balasubramanian K, Beth A, Fritzsche TM, Park JH, Pearson DE, Trommer WE, Venkastaramu SD. The synthesis of deuterium-substituted, spin-labeled analogues of AMP and NAD+ and their use in ESR studies of lactate dehydrogenase. Biochim Biophys Acta 1982; 701:224-8. [PMID: 6280769 DOI: 10.1016/0167-4838(82)90117-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Two spin-labeled analogues of AMP and NAD+ were synthesized, in which a perdeuterated nitroxide radical (4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl, TEMPAMINE) was attached to C-6 or C-8 position of the adenine ring. The ESR spectra of these derivatives exhibit a 4-fold increase in sensitivity and a concomitant decrease in line-width as compared to the corresponding protonated analogues. The improved resolution of composite spectra consisting of freely tumbling and immobilized components is demonstrated in ternary complexes of the spin-labeled NAD+ derivatives with lactate dehydrogenase (L-lactate:NAD+ oxidoreductase, EC 1.1.1.27) and oxalate.
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