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  • Chemistry  (16,750)
  • GEOPHYSICS  (1,730)
  • 2020-2023
  • 2015-2019
  • 1990-1994  (10,258)
  • 1985-1989  (8,222)
  • 1980-1984
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  • 1990  (10,258)
  • 1985  (8,222)
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  • 2020-2023
  • 2015-2019
  • 1990-1994  (10,258)
  • 1985-1989  (8,222)
  • 1980-1984
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  • 1
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    A base dispute (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-08-03
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Waldrop, M M -- New York, N.Y. -- Science. 1990 Aug 3;249(4968):472-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2382127" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Information Systems ; Jurisprudence ; Societies, Scientific ; United States
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
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    Direct measurement of forces between linear polysaccharides xanthan and schizophyllan (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-09-14
    Description: Direct osmotic stress measurements have been made of forces between helices of xanthan, an industrially important charged polysaccharide. Exponentially decaying hydration forces, much like those already measured between lipid bilayer membranes or DNA double helices, dominate the interactions at close separation. Interactions between uncharged schizophyllans also show the same kind of hydration force seen between xanthans. In addition to the practical possibilities for modifying solution and suspension properties through recognition and control of molecular forces, there is now finally the opportunity for theorists to relate macroscopic properties of a polymer solution to the microscopic properties that underlie them.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rau, D C -- Parsegian, V A -- New York, N.Y. -- Science. 1990 Sep 14;249(4974):1278-81.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Biochemistry and Metabolism, National Institute of Diabetes and Digestive and Kidney Diseases, National Institues of Health, Bethesda, MD 20892.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2144663" target="_blank"〉PubMed〈/a〉
    Keywords: Carbohydrate Sequence ; Chemical Phenomena ; Chemistry ; Gels ; *Glycosaminoglycans ; Macromolecular Substances ; Molecular Sequence Data ; Osmosis ; *Polysaccharides, Bacterial ; *Sizofiran ; Solutions ; Viscosity
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
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    Common features of protein unfolding and dissolution of hydrophobic compounds (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-02-02
    Description: Protein unfolding and the dissolution of hydrophobic compounds (including solids, liquids, and gases) in water are characterized by a linear relation between entropy change and heat capacity change. The same slope is found for various classes of compounds, whereas the intercept depends on the particular class. The feature common to these processes is exposure of hydrophobic groups to water. These observations make possible the assignment of the heat capacity change to hydrophobic solvation and lead to the description of protein stability in terms of a hydrophobic and a nonhydrophobic contribution. A general representation of protein stability is given by the heat capacity change and the temperature.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Murphy, K P -- Privalov, P L -- Gill, S J -- New York, N.Y. -- Science. 1990 Feb 2;247(4942):559-61.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2300815" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Protein Denaturation ; *Proteins ; Thermodynamics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
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    Interparticle collisions driven by ultrasound (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-03-02
    Description: Ultrasound has become an important synthetic tool in liquid-solid chemical reactions, but the origins of the observed enhancements remained unknown. The effects of high-intensity ultrasound on solid-liquid slurries were examined. Turbulent flow and shock waves produced by acoustic cavitation were found to drive metal particles together at sufficiently high velocities to induce melting upon collision. A series of transition-metal powders were used to probe the maximum temperatures and speeds reached during such interparticle collisions. Metal particles that were irradiated in hydrocarbon liquids with ultrasound underwent collisions at roughly half the speed of sound and generated localized effective temperatures between 2600 degrees C and 3400 degrees C at the point of impact for particles with an average diameter of approximately 10 microns.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Doktycz, S J -- Suslick, K S -- New York, N.Y. -- Science. 1990 Mar 2;247(4946):1067-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉School of Chemical Sciences, University of Illinois, Urbana 61801.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2309118" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Metals ; Microscopy, Electron, Scanning ; Microspheres ; *Ultrasonics
    Print ISSN: 0036-8075
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
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    Changes in mean concentration, phase shifts, and dissipation in a forced oscillatory reaction (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-01-12
    Description: Experiments are presented that confirm earlier predictions that the mode of supply of reactants to a nonlinear (bio)chemical reaction determines or controls concentrations at steady states far from equilibrium. The oxidation of nicotinamide adenine dinucleotide (NADH) catalyzed by the enzyme horseradish peroxidase with continuous input of oxygen was studied; NAD+ is continuously recycled to NADH through a glucose-6-phosphate dehydrogenase system. A comparison of steady-state concentrations is made with an oscillatory oxygen input and a constant input at the same average oxygen input for both modes. By varying the frequency and amplitude of the perturbation (O2 influx), the following may be changed: the average concentration of NADH; the Gibbs free energy difference delta G of the reactants and products at steady state; the average rate of the reaction; the phase relation between the oscillatory rate and delta G; and the dissipation. These results confirm the possibility of an "alternating current chemistry," of control and optimization of thermodynamic efficiency and dissipation by means of external variation of constraints in classes of nonlinear reactions and biological pumps, and of improvements of the yield in such reactions (heterogeneous catalysis, for example).〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lazar, J G -- Ross, J -- New York, N.Y. -- Science. 1990 Jan 12;247(4939):189-92.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Stanford University, CA 94305.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2294601" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphate/metabolism ; Chemical Phenomena ; Chemistry ; Glucosephosphate Dehydrogenase/*metabolism ; Horseradish Peroxidase/*metabolism ; Kinetics ; NAD/*metabolism ; Oxidation-Reduction ; Oxygen/metabolism ; Peroxidases/*metabolism ; Thermodynamics
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
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    An antibody binding site on cytochrome c defined by hydrogen exchange and two-dimensional NMR (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-08-17
    Description: The interaction of a protein antigen, horse cytochrome c (cyt c), with a monoclonal antibody has been studied by hydrogen-deuterium (H-D) exchange labeling and two-dimensional nuclear magnetic resonance (2D NMR) methods. The H-exchange rate of residues in three discontiguous regions of the cyt c polypeptide backbone was slowed by factors up to 340-fold in the antibody-antigen complex compared with free cyt c. The protected residues, 36 to 38, 59, 60, 64 to 67, 100, and 101, and their hydrogen-bond acceptors, are brought together in the three-dimensional structure to form a contiguous, largely exposed protein surface with an area of about 750 square angstroms. The interaction site determined in this way is consistent with prior epitope mapping studies and includes several residues that were not previously identified. The hydrogen exchange labeling approach can be used to map binding sites on small proteins in antibody-antigen complexes and may be applicable to protein-protein and protein-ligand interactions in general.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3432411/" 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/PMC3432411/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Paterson, Y -- Englander, S W -- Roder, H -- GM 31847/GM/NIGMS NIH HHS/ -- GM 35926/GM/NIGMS NIH HHS/ -- R01 GM031847/GM/NIGMS NIH HHS/ -- S07-RR-05415-28/RR/NCRR NIH HHS/ -- New York, N.Y. -- Science. 1990 Aug 17;249(4970):755-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology, University of Pennsylvania, Philadelphia 19104.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1697101" target="_blank"〉PubMed〈/a〉
    Keywords: Antibodies, Monoclonal/immunology/metabolism ; Antigen-Antibody Complex ; *Binding Sites, Antibody ; Chemical Phenomena ; Chemistry ; Cytochrome c Group/*immunology ; Deuterium ; Epitopes/immunology ; Hydrogen/*metabolism ; Hydrogen Bonding ; Kinetics ; *Magnetic Resonance Spectroscopy ; Molecular Structure ; Protein Conformation
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  • 7
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    Studies of unusual simple molecules by neutralization-reionization mass spectrometry (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-02-23
    Description: Reactive or unstable molecules are key intermediates in many important reactions, but can be difficult to prepare for experimental studies. Species with missing (:CH-OH) or extra (H3) substituents can often be formed conveniently in the gas phase by neutralizing a beam of a more stable ionic counterpart (CH = O+H, H3+). Reionization of the neutral after approximately 10(-6) seconds tests its stability, whereas its unimolecular chemistry can be probed by preparing it with different amounts of internal energy. The resulting neutral products are reionized and mass analyzed. Isomers are then characterized by ion dissociation and a third mass-analysis step. Many unusual molecules have been characterized with this technique, which can also be used to probe complex unimolecular chemistry, such as that of cyclobutadiene and ethylene oxide.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McLafferty, F W -- GM-16609/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1990 Feb 23;247(4945):925-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Cornell University, Baker Laboratory, Ithaca, NY 14853-1301.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2305261" target="_blank"〉PubMed〈/a〉
    Keywords: Butadienes ; Chemical Phenomena ; Chemistry ; Ethylene Oxide ; Free Radicals ; Hydrocarbons ; *Ions ; *Mass Spectrometry ; Methane/analogs & derivatives ; Molecular Structure ; Thermodynamics
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  • 8
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    Inhibition of FKBP rotamase activity by immunosuppressant FK506: twisted amide surrogate (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-05-18
    Description: The immunosuppressive agents cyclosporin A and FK506 inhibit the transcription of early T cell activation genes. The binding proteins for cyclosporin A and FK506, cyclophilin and FKBP, respectively, are peptidyl-prolyl-cis-trans isomerases, or rotamases. One proposed mechanism for rotamase catalysis by cyclophilin involves a tetrahedral adduct of an amide carbonyl and an enzyme-bound nucleophile. The potent FKBP rotamase inhibitor FK506 has a highly electrophilic carbonyl that is adjacent to an acyl-pipicolinyl (homoprolyl) amide bond. Such a functional group would be expected to form a stabilized, enzyme-bound tetrahedral adduct. Spectroscopic and chemical evidence reveals that the drug interacts noncovalently with its receptor, suggesting that the alpha-keto amid of FK506 serves as a surrogate for the twisted amide of a bound peptide substrate.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rosen, M K -- Standaert, R F -- Galat, A -- Nakatsuka, M -- Schreiber, S L -- GM-38627/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1990 May 18;248(4957):863-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Harvard University, Cambridge, MA 02138.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1693013" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Isomerases/*antagonists & inhibitors ; Anti-Bacterial Agents/metabolism/*pharmacology ; Binding Sites ; Carrier Proteins/antagonists & inhibitors/metabolism ; Chemical Phenomena ; Chemistry ; Cloning, Molecular ; Cyclosporins/metabolism/pharmacology ; Escherichia coli/genetics ; Gene Expression ; *Immunosuppressive Agents ; Lymphocyte Activation ; Magnetic Resonance Spectroscopy ; Molecular Structure ; Peptidylprolyl Isomerase ; Recombinant Proteins ; T-Lymphocytes/immunology ; Tacrolimus
    Print ISSN: 0036-8075
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  • 9
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    Bond order and charge localization in nucleoside phosphorothioates (1985)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1985-05-03
    Description: In the recent literature on nucleoside phosphorothioate anions the structural formulas show a double bond between phosphorus and sulfur and a single bond between phosphorus and oxygen with a negative charge localized on oxygen. However, a review of physical data on these compounds shows the reverse to be the case; that is, in phosphorothioate anions the P-S bond is a single bond with a negative charge localized on sulfur, while the P-O bond order for exocyclic and nonbridging oxygens is greater than 1, approaching 2 in O-alkyl phosphorothioate monoanions and O,O-dialkyl phosphorothioates. The P-O bond orders in phosphorothioate dianions and trianions approach 1 1/2 and 1 1/3, respectively, owing to delocalization of negative charge among two or three oxygens. These conclusions are based on bond lengths obtained from x-ray crystallographic data and electron diffraction, the magnitudes of the effects of 18O on the 31P-nuclear magnetic resonance chemical shifts of phosphorus in nucleoside [18O]phosphorothioates, the pH-dependence of 17O-NMR chemical shifts in [17O]phosphate and [17O]thiophosphate, the vibrational spectra of thiophosphate di- and trianions, and the pKa (dissociation constant) values for phosphoric and thiophosphoric acids.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Frey, P A -- Sammons, R D -- GM30480/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1985 May 3;228(4699):541-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2984773" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Chemistry, Physical ; Cyclic AMP/metabolism ; Magnetic Resonance Spectroscopy ; Phosphates/metabolism ; Phosphoric Acids/metabolism ; Physicochemical Phenomena ; *Thionucleotides/metabolism
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  • 10
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    Dissociation of antitumor potency from anthracycline cardiotoxicity in a doxorubicin analog (1985)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1985-06-28
    Description: The search for new congeners of the leading anticancer drug doxorubicin has led to an analog that is approximately 1000 times more potent, noncardiotoxic at therapeutic dose levels, and non-cross-resistant with doxorubicin. The new anthracycline, 3'-deamino-3'-(3-cyano-4-morpholinyl)doxorubicin (MRA-CN), is produced by incorporation of the 3' amino group of doxorubicin in a new cyanomorpholinyl ring. The marked increase in potency was observed against human ovarian and breast carcinomas in vitro; it was not accompanied by an increase in cardiotoxicity in fetal mouse heart cultures. Doxorubicin and MRA-CN both produced typical cardiac ultrastructural and biochemical changes, but at equimolar concentrations. In addition, MRA-CN was not cross-resistant with doxorubicin in a variant of the human sarcoma cell line MES-SA selected for resistance to doxorubicin. Thus antitumor efficacy was dissociated from both cardiotoxicity and cross-resistance by this modification of anthracycline structure.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sikic, B I -- Ehsan, M N -- Harker, W G -- Friend, N F -- Brown, B W -- Newman, R A -- Hacker, M P -- Acton, E M -- CA 24543/CA/NCI NIH HHS/ -- CA 32250/CA/NCI NIH HHS/ -- CA 33303/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1985 Jun 28;228(4707):1544-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/4012308" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Antineoplastic Agents ; Breast Neoplasms/drug therapy ; Cell Line ; Chemical Phenomena ; Chemistry ; Dose-Response Relationship, Drug ; Doxorubicin/adverse effects/*analogs & derivatives/therapeutic use ; Female ; Heart/drug effects ; Humans ; Isoenzymes ; L-Lactate Dehydrogenase/analysis ; Mice ; Myocardium/enzymology ; Ovarian Neoplasms/drug therapy ; Pregnancy
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  • 11
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    A potent nonpeptide cholecystokinin antagonist selective for peripheral tissues isolated from Aspergillus alliaceus (1985)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1985-10-11
    Description: A new, competitive, nonpeptide cholecystokinin (CCK) antagonist, asperlicin, was isolated from the fungus Aspergillus alliaceus. The compound has 300 to 400 times the affinity for pancreatic, ileal, and gallbladder CCK receptors than proglumide, a standard agent of this class. Moreover, asperlicin is highly selective for peripheral CCK receptors relative to brain CCK and gastrin receptors. Since asperlicin also exhibits long-lasting CCK antagonist activity in vivo, it should provide a valuable tool for investigating the physiological and pharmacological actions of CCK.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chang, R S -- Lotti, V J -- Monaghan, R L -- Birnbaum, J -- Stapley, E O -- Goetz, M A -- Albers-Schonberg, G -- Patchett, A A -- Liesch, J M -- Hensens, O D -- New York, N.Y. -- Science. 1985 Oct 11;230(4722):177-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2994227" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Aspergillus/*metabolism ; Benzodiazepinones/*isolation & purification/pharmacology ; Chemical Phenomena ; Chemistry ; Cholecystokinin/*antagonists & inhibitors/pharmacology/physiology ; Dose-Response Relationship, Drug ; Gallbladder/drug effects ; Guinea Pigs ; Ileum/drug effects ; Pancreas/drug effects ; Rats ; Receptors, Cell Surface/drug effects ; Receptors, Cholecystokinin
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  • 12
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    Three-dimensional structure of poliovirus at 2.9 A resolution (1985)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1985-09-27
    Description: The three-dimensional structure of poliovirus has been determined at 2.9 A resolution by x-ray crystallographic methods. Each of the three major capsid proteins (VP1, VP2, and VP3) contains a "core" consisting of an eight-stranded antiparallel beta barrel with two flanking helices. The arrangement of beta strands and helices is structurally similar and topologically identical to the folding pattern of the capsid proteins of several icosahedral plant viruses. In each of the major capsid proteins, the "connecting loops" and NH2- and COOH-terminal extensions are structurally dissimilar. The packing of the subunit "cores" to form the virion shell is reminiscent of the packing in the T = 3 plant viruses, but is significantly different in detail. Differences in the orientations of the subunits cause dissimilar contacts at protein-protein interfaces, and are also responsible for two major surface features of the poliovirion: prominent peaks at the fivefold and threefold axes of the particle. The positions and interactions of the NH2- and COOH-terminal strands of the capsid proteins have important implications for virion assembly. Several of the "connecting loops" and COOH-terminal strands form prominent radial projections which are the antigenic sites of the virion.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hogle, J M -- Chow, M -- Filman, D J -- AI-20566/AI/NIAID NIH HHS/ -- AI-22346/AI/NIAID NIH HHS/ -- NS-07078/NS/NINDS NIH HHS/ -- R01 AI020566/AI/NIAID NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1985 Sep 27;229(4720):1358-65.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2994218" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Antigens, Viral/immunology ; Capsid/physiology ; Chemical Phenomena ; Chemistry ; HeLa Cells/microbiology ; Mutation ; Poliovirus/physiology/*ultrastructure ; Protein Conformation ; Virus Replication ; X-Ray Diffraction
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  • 13
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    Qinghaosu (artemisinin): an antimalarial drug from China (1985)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1985-05-31
    Description: The herb Artemisia annua has been used for many centuries in Chinese traditional medicine as a treatment for fever and malaria. In 1971, Chinese chemists isolated from the leafy portions of the plant the substance responsible for its reputed medicinal action. This compound, called qinghaosu (QHS, artemisinin), is a sesquiterpene lactone that bears a peroxide grouping and, unlike most other antimalarials, lacks a nitrogen-containing heterocyclic ring system. The compound has been used successfully in several thousand malaria patients in China, including those with both chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum. Derivatives of QHS, such as dihydroqinghaosu, artemether, and the water-soluble sodium artesunate, appear to be more potent than QHS itself. Sodium artesunate acts rapidly in restoring to consciousness comatose patients with cerebral malaria. Thus QHS and its derivatives offer promise as a totally new class of antimalarials.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Klayman, D L -- New York, N.Y. -- Science. 1985 May 31;228(4703):1049-55.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3887571" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Antimalarials ; *Artemisinins ; Brain Diseases/therapy ; Chemical Phenomena ; Chemistry ; Humans ; Liver/metabolism ; Malaria/*drug therapy ; Medicine, Chinese Traditional ; Metabolic Clearance Rate ; Plants, Medicinal/analysis ; Plasmodium berghei ; Plasmodium falciparum ; *Sesquiterpenes/isolation & purification/metabolism/therapeutic use/toxicity
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  • 14
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    Sculpting horizons in organic chemistry (1985)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1985-02-22
    Description: Organic chemistry as a discipline derives from and impacts on the biological and abiological world in which we live. Its challenges lie in the areas of structure, reactivity, techniques, and concepts. Powerful structural tools reveal structures from biology that range from control of insect development and behavior to whole new metabolic pathways in humans. Unnatural products create beautiful new molecular shapes whose properties cannot be predicted as well as catalysts that function with enzyme-like control. From structure flows reactivity. Exploration of known reactions points to new directions, and development of new reactions offers the opportunity of streamlined synthetic design. Emerging new techniques offer new dimensions for performing and studying reactions as well as the hope for developing new ones. Merging disparate facts into unified concepts increases predictive capabilities. The extraordinary difficulty of finding the resultant of many small effects may obscure the presence of general theories, creates the art in the practice of the science, and challenges the practitioner. From these general themes derives the quest for selectivity--chemo-, regio-, diastereo-, and enantio-. An examination of the fundamental underpinnings of the applications of organic chemistry reveals that, while impressive strides have been made, the science is best described as being between infancy and childhood. The cross-fertilization between organic chemistry and molecular biology vividly illustrates a merging of chemistry and biology.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Trost, B M -- New York, N.Y. -- Science. 1985 Feb 22;227(4689):908-16.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3969569" target="_blank"〉PubMed〈/a〉
    Keywords: Alkylation ; Animals ; Chemical Phenomena ; Chemistry ; *Chemistry, Organic ; Enzymes ; Humans ; Insects ; Mammals ; Organic Chemistry Phenomena ; Research ; Stereoisomerism
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    Hernandulcin: an intensely sweet compound discovered by review of ancient literature (1985)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1985-01-25
    Description: Ancient Mexican botanical literature was systematically searched for new plant sources of intensely sweet substances. Lippia dulcis Trev., a sweet plant, emerged as a candidate for fractionation studies, and hernandulcin, a sesquiterpene, was isolated and judged by a human taste panel as more than 1000 times sweeter than sucrose. The structure of the sesquiterpene was determined spectroscopically and confirmed by chemical synthesis. Hernandulcin was nontoxic when administered orally to mice, and it did not induce bacterial mutation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Compadre, C M -- Pezzuto, J M -- Kinghorn, A D -- Kamath, S K -- N01-DE-02425/DE/NIDCR NIH HHS/ -- New York, N.Y. -- Science. 1985 Jan 25;227(4685):417-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3880922" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Bibliography as Topic ; Botany/history ; Chemistry ; History, 16th Century ; Humans ; Magnetic Resonance Spectroscopy ; Mexico ; Mice ; Molecular Conformation ; Mutagenicity Tests ; *Plants/analysis ; *Sesquiterpenes/chemical synthesis/isolation & purification/toxicity ; *Sweetening Agents/chemical synthesis/history/isolation & purification/toxicity
    Print ISSN: 0036-8075
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 16
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    Computer-assisted analysis in organic synthesis (1985)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1985-04-26
    Description: The planning of alternative routes for the synthesis of complex organic molecules has been facilitated by the formulation of guiding strategies that can be applied to a broad range of problems. Analysis of organic synthesis can be carried out in the retrosynthetic direction, opposite to the actual process of chemical synthesis, or bidirectionally, that is, as a combined retrosynthetic and synthetic search. An interactive computer program is described which utilizes the general strategies of retrosynthetic analysis and an appropriate database to generate pathways of chemical intermediates for chemical synthesis of a particular target structure. Computer graphics and standard chemical structures are used for man-machine communication.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Corey, E J -- Long, A K -- Rubenstein, S D -- New York, N.Y. -- Science. 1985 Apr 26;228(4698):408-18.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3838594" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Chemistry, Organic/*methods ; *Computers ; Forecasting ; Software
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 17
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    Dynamics and conformational energetics of a peptide hormone: vasopressin (1985)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1985-03-15
    Description: A theoretical methodology for use in conjunction with experiment was applied to the neurohypophyseal hormone lysine vasopressin for elucidation of its accessible molecular conformations and associated flexibility, conformational transitions, and dynamics. Molecular dynamics and energy minimization techniques make possible a description of the conformational properties of a peptide in terms of the precise positions of atoms, their fluctuations in time, and the interatomic forces acting on them. Analysis of the dynamic trajectory of lysine vasopressin shows the ability of a flexible peptide hormone to undergo spontaneous conformational transitions. The excursions of an individual phenylalanine residue exemplify the dynamic flexibility and multiple conformational states available to small peptide hormones and their component residues, even within constraints imposed by a cyclic hexapeptide ring.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hagler, A T -- Osguthorpe, D J -- Dauber-Osguthorpe, P -- Hempel, J C -- New York, N.Y. -- Science. 1985 Mar 15;227(4692):1309-15.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3975616" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Chemistry, Physical ; Energy Metabolism ; Hydrogen Bonding ; Lypressin/*metabolism ; Phenylalanine/metabolism ; Physicochemical Phenomena ; Protein Conformation
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 18
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    Single-carbon chemistry of acetogenic and methanogenic bacteria (1985)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1985-03-08
    Description: Methanogenic and acetogenic bacteria metabolize carbon monoxide, methanol, formate, hydrogen and carbon dioxide gases and, in the case of certain methanogens, acetate, by single-carbon (C1) biochemical mechanisms. Many of these reactions occur while the C1 compounds are linked to pteridine derivatives and tetrapyrrole coenzymes, including corrinoids, which are used to generate, reduce, or carbonylate methyl groups. Several metalloenzymes, including a nickel-containing carbon monoxide dehydrogenase, are used in both catabolic and anabolic oxidoreductase reactions. We propose biochemical models for coupling carbon and electron flow to energy conservation during growth on C1 compounds based on the carbon flow pathways inherent to acetogenic and methanogenic metabolism. Biological catalysts are therefore available which are comparable to those currently in use in the Monsanto process. The potentials and limitations of developing biotechnology based on these organisms or their enzymes and coenzymes are discussed.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zeikus, J G -- Kerby, R -- Krzycki, J A -- 144-T263/PHS HHS/ -- New York, N.Y. -- Science. 1985 Mar 8;227(4691):1167-73.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3919443" target="_blank"〉PubMed〈/a〉
    Keywords: Acetates/*metabolism ; Acetobacter/metabolism ; Bacteria/*metabolism ; Carbon Dioxide/metabolism ; Carbon Monoxide/metabolism ; Chemical Phenomena ; Chemistry ; Clostridium/metabolism ; Eubacterium/metabolism ; Euryarchaeota/*metabolism ; Formates/metabolism ; Methane/metabolism ; Methanol/metabolism
    Print ISSN: 0036-8075
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 19
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    Trypanothione: a novel bis(glutathionyl)spermidine cofactor for glutathione reductase in trypanosomatids (1985)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1985-03-22
    Description: Glutathione reductase from trypanosomes and leishmanias, unlike glutathione reductase from other organisms, requires an unusual low molecular weight cofactor for activity. The cofactor was purified from the insect trypanosomatid Crithidia fasciculata and identified as a novel glutathione-spermidine conjugate, N1,N8-bis(L-gamma-glutamyl-L-hemicystinyl-glycyl)spermidine, for which the trivial name trypanothione is proposed. This discovery may open a new chemotherapeutic approach to trypanosomiasis and leishmaniasis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fairlamb, A H -- Blackburn, P -- Ulrich, P -- Chait, B T -- Cerami, A -- 1 R01 A127429/PHS HHS/ -- 1 R01 AI19428/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1985 Mar 22;227(4693):1485-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3883489" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Chemical Phenomena ; Chemistry ; Coenzymes/analysis/*isolation & purification/metabolism ; Crithidia/*enzymology ; Glutathione/*analogs & derivatives/analysis/isolation & purification/metabolism ; Glutathione Reductase/*metabolism ; Leishmania/*enzymology ; Oxidation-Reduction ; Spermidine/*analogs & derivatives/analysis/isolation & purification/metabolism ; Terminology as Topic ; Trypanosoma/*enzymology ; Trypanosoma brucei brucei/enzymology ; Trypanosoma cruzi/enzymology
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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    Mechanisms of coenzyme B12-dependent rearrangements (1985)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1985-02-22
    Description: Coenzyme B12 serves as a cofactor in various enzymatic reactions in which a hydrogen atom is interchanged with a substituent on an adjacent carbon atom. Measurement of the dissociation energy of the coenzyme's cobalt-carbon bond and studies of the rearrangement of model free radicals related to those derived from methylmalonyl-coenzyme A suggest that these enzymatic reactions occur through homolytic dissociation of the coenzyme's cobalt-carbon bond, abstraction of a hydrogen atom from the substrate by the coenzyme-derived 5'-deoxyadenosyl radical, and rearrangement of the resulting substrate radical. The only role thus far identified for coenzyme B12 in these reactions--namely, that of a free radical precursor--reflects the weakness, and facile dissociation, of the cobalt-carbon bond.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Halpern, J -- New York, N.Y. -- Science. 1985 Feb 22;227(4689):869-75.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2857503" target="_blank"〉PubMed〈/a〉
    Keywords: Carbon/metabolism ; Chemical Phenomena ; Chemistry ; Chemistry, Physical ; Cobalt/metabolism ; Cobamides/*metabolism ; Energy Metabolism ; Free Radicals ; Methylmalonyl-CoA Mutase/metabolism ; Physicochemical Phenomena
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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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
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 22
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    [2 + 2] photocycloadditions in the synthesis of chiral molecules (1985)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1985-02-22
    Description: A strategy for the synthesis of chiral molecules that receives growing popularity among organic chemists employs the photochemically mediated [2 + 2] cycloaddition reaction. These reactions can be performed on a multigram scale and often proceed with high yield and with stereocontrol. These features, in combination with the useful properties of the four-membered ring photoproducts in subsequent chemical transformations, make them attractive options in the early stage of a synthesis design. Various combinations of unsaturated functional groups can participate in this reaction process. Accordingly, these chemical reactions can be economical solutions to problems relating to the synthesis of a variety of target molecules.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schreiber, S L -- GM-32527/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1985 Feb 22;227(4689):857-63.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/4038558" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Anti-Bacterial Agents/chemical synthesis ; Antifungal Agents/chemical synthesis ; Chemical Phenomena ; Chemistry ; Cockroaches ; Female ; Furans/chemical synthesis ; Lactones/chemical synthesis ; Male ; Mycotoxins/chemical synthesis ; *Photochemistry ; Pyrones/chemical synthesis ; Sex Attractants/chemical synthesis/isolation & purification ; Stereoisomerism
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    Computerized pattern recognition: a new technique for the analysis of chemical communication (1985)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1985-04-12
    Description: Computerized pattern recognition techniques can be applied to the study of complex chemical communication systems. Analysis of high resolution gas chromatographic concentration patterns of the major volatile components of the scent marks of a South American primate, Saguinus fuscicollis, demonstrates that the concentration patterns can be used to predict the gender and subspecies of unknown donors.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Smith, A B 3rd -- Belcher, A M -- Epple, G -- Jurs, P C -- Lavine, B -- 5 T32 NSO7176-03/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1985 Apr 12;228(4696):175-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3975636" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Chemical Phenomena ; Chemistry ; Chromatography, Gas ; *Computers ; Female ; Male ; *Pattern Recognition, Automated ; Pheromones/*physiology ; Saguinus/physiology ; Scent Glands/physiology ; Sex Attractants/*physiology ; Structure-Activity Relationship
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 24
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    Accurate GPS measurement of the location and orientation of a floating platform (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: This article describes the design and initial tests of the GPS portion of a system for making seafloor geodesy measurements. In the planned system, GPS antennas on a floating platform will be used to measure the location of an acoustic transducer, attached below the platform, which interrogates an array of transponders on the seafloor. Since the GPS antennas are necessarily some distance above the transducer, a short-baseline GPS interferometer consisting of three antennas is used to measure the platform's orientation. A preliminary test of several crucial elements of the system was performed. The test involved a fixed antenna on the pier and a second antenna floating on a buoy about 80 m away. GPS measurements of the vertical component of this baseline, analyzed independently by two groups using different software, agree with each other and with an independent measurement within a centimeter. The first test of an integrated GPS/acoustic system took place in the Santa Cruz Basin off the coast of southern California in May 1990. In this test a much larger buoy, designed and built at SIO, was equipped with three GPS antennas and an acoustic transducer that interrogated a transponder on the ocean floor. Preliminary analysis indicates that the horizontal position of the transponder can be determined with a precision of about a centimeter.
    Keywords: GEOPHYSICS
    Type: Marine Geodesy (ISSN 0149-0419); p. 255-264.
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    AVHRR imagery reveals Antarctic ice dynamics (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A portion of AVHRR data taken on December 5, 1987 at 06:15 GMT over a part of Antarctica is used here to show that many of the most significant dynamic features of ice sheets can be identified by a careful examination of AVHRR imagery. The relatively low resolution of this instrument makes it ideal for obtaining a broad view of the ice sheets, while its wide swath allows coverage of areas beyond the reach of high-resolution imagers either currently in orbit or planned. An interpretation is given of the present data, which cover the area of ice streams that drain the interior of the West Antarctic ice sheet into the Ross Ice Shelf.
    Keywords: GEOPHYSICS
    Type: EOS (ISSN 0096-3941); 71; 741
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    Earth Radiation Budget Experiment - Preliminary seasonal results (1990)
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    Publication Date: 2011-08-24
    Description: Data from the Earth Radiation Budget Satellite (ERBS) and from the operational NOAA-9 satellite being placed in the archive of the earth Radiation Budget Experiment (ERBE) are discussed. The results of the ERBE data validation effort are reviewed along with ERBE solar constant observations and earth-viewing results. The latter include monthly average results for July 1985, annual average clear-sky fluxes, and annual average, zonal, and global results.
    Keywords: GEOPHYSICS
    Type: EOS (ISSN 0096-3941); 71; 297
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    Error analysis for earth orientation recovery from GPS data (1990)
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    Publication Date: 2011-08-24
    Description: The use of GPS navigation satellites to study earth-orientation parameters in real-time is examined analytically with simulations of network geometries. The Orbit Analysis covariance-analysis program is employed to simulate the block-II constellation of 18 GPS satellites, and attention is given to the budget for tracking errors. Simultaneous solutions are derived for earth orientation given specific satellite orbits, ground clocks, and station positions with tropospheric scaling at each station. Media effects and measurement noise are found to be the main causes of uncertainty in earth-orientation determination. A program similar to the Polaris network using single-difference carrier-phase observations can provide earth-orientation parameters with accuracies similar to those for the VLBI program. The GPS concept offers faster data turnaround and lower costs in addition to more accurate determinations of UT1 and pole position.
    Keywords: GEOPHYSICS
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    Geomagnetic sudden impulses and storm sudden commencements - A note on terminology (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The definitions of and distinctions between storm sudden commencements (SSCs) and geomagnetic sudden impulses (SIs) are examined and present definitions of SIs and SSCs are modernized. Quantitative definitions of the two terms are recommended.
    Keywords: GEOPHYSICS
    Type: EOS (ISSN 0096-3941); 71; 1808
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    Seismic analysis of the large 70-meter antenna, part 1: Earthquake response spectra versus full transient analysis (1985)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: As a check on structure safety aspects, two approaches in seismic analysis for the large 70-m antennas are presented. The first approach, commonly used by civil engineers, utilizes known recommended design response spectra. The second approach, which is the full transient analysis, is versatile and applicable not only to earthquake loading but also to other dynamic forcing functions. The results obtained at the fundamental structural frequency show that the two approaches are in good agreement with each other and both approaches show a safe design. The results also confirm past 64-m antenna seismic studies done by the Caltech Seismology Staff.
    Keywords: GEOPHYSICS
    Type: The Telecommun. and Data Acquisition Progr. Rept.; p 31-42
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    Theoretical and experimental design studies for the Atmospheric General Circulation Experiment (1985)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The major criterion for the Atmospheric General Circulation Experiment (AGCE) design is that it be possible to realize strong baroclinic instability in the spherical configuration chosen. A configuration was selected in which a hemispherical shell of fluid is subjected to latitudinal temperature gradients on its spherical boundaries and the latitudinal boundaries are insulators. Work in the laboratory with a cylindrical version of this configuration revealed more instabilities than baroclinic instability. Since researchers fully expect these additional instabilities to appear in the spherical configuration also, they decided to continue the laboratory cylindrical annulus studies. Four flow regimes were identified: an axisymmetric Hadley circulation, boundary layer convection, baroclinic waves and deep thermal convection. Regime diagrams were prepared.
    Keywords: GEOPHYSICS
    Type: NASA(MSFC FY-85 Atmospheric Processes Research Review; 2 p
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    The use of satellite data in understanding and predicting convective and large-scale dynamical processes (1985)
    In:  CASI
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    Publication Date: 2006-02-14
    Description: A two-layer truncated baroclinic spectral model was developed to study the long-term evolution of disturbances to a baroclinically unstable mean flow. Topography and crudely-parameterized radiative processes were accounted for. As a result of Robert Schlaak's discovery of the underlying barotropic nature of the index oscillation as well as reviewers suggestions about the original manuscript, the model has been revised to allow for barotropic as well as baroclinic wave-mean flow interactions. The form-drag exerted by the topography on the barotropic part of the mean flow is larger than on the baroclinic part and thus researchers anticipate significant changes from the original calculations on the index oscillation when it is strongly modulated by topography. Researchers believe that since the index oscillation accounts for a significant portion of atmospheric temporal variance, the long term predictability could be improved if reliable forecasts of the index oscillation were available. Two spectral models of the index oscillation, one barotropic and the other baroclinic, have been developed. The latter allows for moisture, radiation, land-sea temperature countrasts, and energy exchanges with the underlying surface.
    Keywords: GEOPHYSICS
    Type: NASA. Marshall Space Flight Center NASA(MSFC FY-85 Atmospheric Processes Research Review; 2 p
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    Age-dating volcanic and alluvial surfaces with multipolarization data (1985)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: A false-color multipolarization version of one of the images of Owens Valley area acquired by the JPL Synthetic Aperture Radar (SAR) is given. A geologic map of the alluvial fans there (Gillespie, 1982) is also given for comparison. In general, brightness in the multipolarization images can be seen to be inversely proportional to the age of the surfaces. A more detailed investigation of the relationship between backscatter and age of the surfaces was undertaken with calibrated aircraft SAR data. The quantitative relationship between backscatter coefficient and age for the three polarizations is shown. The straight lines connecting the measured data points imply a steady-state process, although the process or processes leading to this relationship may have operated at rates that varied with climate fluctuations, such as the glacial ages. It is expected that the relationship between radar brightness and age is a consistent one, and that with the wider availability of calibrated radar backscatter data, these relationships can be less well-known areas. The effect of variable such as past climate fluctuations, tectonic disturbance, and rock type must be understood before extension beyond the Mojave Desert region can be attempted.
    Keywords: GEOPHYSICS
    Type: NASA(JPL Aircraft SAR Workshop Proc.; p 31-36
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    Mobile VLBI and GPS measurement of vertical crustal motion (1985)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Mobile Very Long Base Interferometry (VLBI) and Global Positioning System (GPS) geodetic measurements have many error sources in common. Calibration of the effects of water vapor on signal transmission through the atmosphere, however, remains the primary limitation to the accuracy of vertical crustal motion measurements made by either technique. The two primary methods of water vapor calibration currently in use for mobile VLBI baseline measurements were evaluated: radiometric measurements of the sky brightness near the 22 GHz emission line of free water molecules and surface meteorological measurements used as input to an atmospheric model. Based upon a limited set of 9 baselines, it is shown that calibrating VLBI data with water vapor radiometer measurements provides a significantly better fit to the theoretical decay model than calibrating the same data with surface meteorological measurements. The effect of estimating a systematic error in the surface meteorological calibration is shown to improve the consistency of the vertical baseline components obtained by the two calibration methods. A detailed error model for the vertical baseline components obtained indicates current mobile VLBI technology should allow accuracies of order 3 cm with WVR calibration and 10 cm when surface meteorological calibration is used.
    Keywords: GEOPHYSICS
    Type: The Telecommun. and Data Acquisition Progr. Rept.; p 185-198
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    Theoretical and experimental studies in support of the geophysical fluid flow experiment (1985)
    In:  CASI
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    Publication Date: 2006-02-14
    Description: Meteorologists and astrophysicists interested in large scale planetary and solar circulations have come to recognize the importance of rotation and stratification in determining the character of these flows. In particular, the effect of latitude-dependent Coriolis force on nonlinear convection is thought to play a crucial role in such phenomena as differential rotation on the Sun, cloud band orientation on Jupiter, and the generation of magnetic fields in thermally driven dynamos. The continuous low-gravity environment of the orbiting space shuttle offers a unique opportunity to make laboratory studies of such large-scale thermally driven flows under the constraint imposed by rotation and sphericity. This is possible because polarization forces in a dielectric liquid, which are linearly dependent on fluid temperature, give rise to an effectively radial buoyancy force when a radial electrostatic field is imposed. The Geophysical Fluid Flow Cell (GFFC) is an implementation of this ideal in which fluid is contained between two rotating hemispheres that are differentially heated and stressed with a large a-c voltage. The experiment, to be flown on Spacelab III (currently set for launch April 29, 1985), will explore non-linear mode selection and high Rayleigh number turbulence in a rotating convecting spherical shell of liquid. Experiments will be carried out in a low driving parameter range where some limited numerical experimentation is currently feasible, as well as in a parameter range significantly beyond numerical computation for many years.
    Keywords: GEOPHYSICS
    Type: NASA. Marshall Space Flight Center NASA(MSFC FY-85 Atmospheric Processes Research Review; 3 p
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    GPS measurements of regional deformation in southern California - Some constraints on performance (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Results from the first major survey of southern California with GPS equipment are presented along with some limited results from late experiments assessing GPS performance by analysis of day-to-day and longer-term repeatability, as well as comparisons with VLBI. GPS performance on longer (50-500 km or longer) baselines, a length range useful for measurement of regional deformation and fault block velocities, is emphasized. The implications of this level of performance for meeting longer-term scientific objectives is addressed. It is concluded that GPS techniques and yield results comparable to those achieved with mobile VLBI techniques in California, assuming that appropriate network design and analysis techniques are used. GPS can thus provide important constraints on regional deformation in California with five yrs or less of measurements.
    Keywords: GEOPHYSICS
    Type: EOS (ISSN 0096-3941); 71; 1051-105
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    Interannual and decade fluctuations in the earth's rotation (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The main findings of a study of earth rotation changes on the longer interannual and decade range of time scales are summarized. The earth rotation data provide important constraints on models of the internal structure and dynamics of the core and lower mantle. Torques at the core-mantle interface are due to time varying fluid motions in the core. A torque of about 0.2 Hadley units is found in the axial component during the 1980 period.
    Keywords: GEOPHYSICS
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    Study of the crust and mantle using magnetic surveys by Magsat and other satellites (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This article summarizes some of the methodology and results for studies of the earth's mantle and crust. Mantle conductivity studies can be made either by studying signals impressed on the earth from outside, e.g., the ionosphere or magnetosphere, or by studing signals originating in the core and transmitted through the mantle. Crustal field studies begin with a careful selection of the data and subsequent removal of core and external fields by some sort of filtering. Average maps from different local times sometimes differ, presumably due to the remaining presence of fields of external origin. Several techniques for further filtering are discussed. Where large-area aeromagnetic maps are available, crustal maps derived from satellite data can be compared with upward continued data. In general, the comparisons show agreement, with some differences, particularly in and near the auroral belts. The satellite data are further reduced by various methods of inverse and forward modeling, sometimes including reduction to the pole. These techniques are generally unstable at the equator. Common methods of stabilizing the inversions include principle components analysis and ridge regression. Because of the presence of the core field, the entire crustal contribution from the field is not known. Also, there is a basic nonuniqueness to the inverse solutions. Nevertheless, magnetizations that are interpretable can be derived.
    Keywords: GEOPHYSICS
    Type: (ISSN 0253-4126); 99; 581-618
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  • 38
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    Differential absorption lidar detection of ozone in the troposphere and lower stratosphere (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The DIAL technique for deriving O3 profiles from lidar measurements is discussed. Examples of a variety of O3 and aerosol measurements are presented from studies of (1) photochemically produced O3 in the summertime over the eastern United States and in biomass burning plumes during the dry season over the Amazon Basin of Brazil; (2) vertical O3 transport from the mixed layer into the free troposphere via cloud dynamics and from the stratosphere into the troposphere via tropopause fold events; and (3) O3 depletion in the O3 hole over Antarctica. The NASA airborne DIAL system is considered to be an advanced field system.
    Keywords: GEOPHYSICS
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    Short wavelength striations on expanding plasma clouds (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The present evaluation of current understanding of the growth and evolution of less-than-1 ion gyroradius 'flute modes' on a plasma as it expands across and ambient magnetic field notes that the mechanism by which the instability is generated, and its approximate linear theory (encompassing nonlocal, finite-beta, and collisional effects), have reached a satisfactory degree of development. AMPTE Ba releases have been the bases of most of the observational studies. Substantial progress is also noted in the development of a nonlinear mode-coupling theory which can resolve remaining differences between theory and observation.
    Keywords: GEOPHYSICS
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    Recent advances in magnetospheric substorm research (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: More than two decades of magnetospheric exploration have led to a reasonably clear morphological picture of geomagnetic substorms, which is often summarized in terms of the near-earth neutral line model of substorms. Although this qualitative theory is quite comprehensive and explains a great many observations, it is hard pressed to explain both recent observations of consistently earthward flow within 19 RE and also the prompt onset of magnetic turbulence at 8 RE at the time of substorm onset. Other theories have recently been proposed which tend to be more quantitative, but which explain a more limited number of substorm observations. The challenge seems to be to understand the esential physics of these various quantitative theories and integrate them into a larger structure such as provided by the near-earth neutral line model.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics (ISSN 0021-9169); 52; 1155-116
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  • 41
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    The AMPTE lithium releases in the solar wind - A possible trigger for geomagnetic pulsations (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Shortly after the AMPTE/IRM satellite had released Lithium ions into the solar wind, magnetometers on the ground and in the frontside magnetosphere observed deflections of a type similar to those associated with solar wind pressure pulses. Since the natural solar wind was very stable during this event and did not exhibit pressure changes, the magnetic deflections have likely been caused by the artificially injected Lithium cloud when it hit the magnetosphere. Order of magnitude estimates show that 300 g of Lithium vapor released in the solar wind are indeed able to produce a 300 nT magnetic deflection on the ground under favorable conditions.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 2301-230
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  • 42
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    Lidar observations of ozone changes induced by subpolar air mass motion over Table Mountain, California (34.4 deg N) (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Between October 15 and November 8, 1988, the Goddard Space Flight Center mobile stratospheric lidar was in place at the (JPL) Table Mountain Facility (located at 34.4 deg N, 117.7 deg W) for the purpose of intercomparing with the JPL lidar permanently stationed at the observatory. During the course of the intercomparison both lidar systems detected a significant change in the vertical profile of ozone lasting for several days. An analysis of meteorological data available from the National Meteorological Center has shown this change to be dynamical in origin due to the transport of subpolar air over Table Mountain.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 20527-20
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  • 43
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    Comment on 'A new method of spectral analysis and its application to the earth's free oscillations - The 'Sompi' method' by S. Hori et al (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 19789
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  • 44
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    Laboratory measurements of NO2 line parameters near 1600/cm for the interpretation of stratospheric spectra (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Tunable diode laser laboratory measurements of infrared spectral parameters of selected NO2 lines near 1600/cm have been made to assess the contribution of uncertainties in these parameters to stratospheric measurements of NO2 made using the Balloon-Borne Laser In-Situ Sensor (BLISS) tunable diode laser spectrometer. Relative line intensities are measured to accuracies of better than 2 percent, with a root-sum-squared uncertainty in the absolute linestrengths of 4.5 percent. Air-broadening coefficients have been determined from measurements at total pressures in the range 20-100 Torr, at temperatures of 293 K and 214 K. These results are also discussed in the light of the discrepancies between infrared instruments flown in the 1982 and 1983 Balloon Intercomparison Campaigns.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 2157-216
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  • 45
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    Intrusive and extrusive growth of the Mount St Helens lava dome (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: High-resolution, digital topographic maps of the Mount St. Helens dome derived from aerial photographs are used here to make a quantitative assessment of the partitioning of magma into endogenous intrusion and exogenous lobes. The endogenous growth is found to be predictable, which shows that the cooling dome controls its own development independently of such deep-seated factors as magma overpressure and extrusion rate. The observed regular decrease in exogenous growth rate also allows volume prediction. Knowledge of the volume can be used to determine when an ongoing eruptive event should end. Finally, the observed transition from predominantly exogenous to predominantly endogenous growth reflects the increase in crust thickness, which in turn seems to depend on long repose periods rather than some fundamental change in the character of the dome.
    Keywords: GEOPHYSICS
    Type: Nature (ISSN 0028-0836); 348; 435-437
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  • 46
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    Pc1 pulsations observed by AMPTE/CCE in the earth's outer magnetosphere (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Electromagnetic ion-cyclotron waves in the Pc1-2 frequency range (0.1-5 Hz) have been observed in earth's equatorial magnetosphere over the range L = 3 to 9 by the AMPTE/CCE magnetic-field experiment. Detailed analysis of data from two orbits together with preliminary occurrence statistics from 31 days are reported. One example occurred during disturbed geomagnetic conditions (maximum AE greater than 1000 nT) and exhibited intense Pc1 from L = 5 to the magnetopause (L = about 7.5). The second example occurred during moderate to quiet conditions (average AE = about 300 nT) and displayed Pc1 in two distinct L ranges: low (L = about 4) and high (L greater than 7.5). Statistical results show that Pc1 are about 4 times more common for L greater than 7 than for L less than 6 and occur primarily in the afternoon. The discovery of a statistically dominant outer-magnetospheric source region implies that ring-current interaction with the plasmasphere is not the primary source of Pc1 excitation, but suggests that plasma sheet ions may be a significant energy source for Pc1. This result is consistent with the strong dependence of the linear convective growth rate on magnetic-field strength.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 1853-185
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  • 47
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    The mechanics of the South Iceland Seismic Zone (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The mechanics of the South Iceland Seismic Zone is examined by means of boundary element modeling. The differences between the observed geometry of the major tectonically active features and that of a geometrically orthogonal ridge-transform system (which assumes that the upper part of the earth's crust is an elastic plate containing vertical cuts) are examined. It is suggested that north-south faults can accommodate transform deformation only if the faults are longer or more numerous than those observed so far. This is considered reasonable because earthquake surface rupture lengths are commonly less than the inferred fault length at depth. The South Iceland Seismic Zone is subject to sequences of large earthquake every 45-112 years. In comparing the seismic moment release derived from earthquake magnitudes with that predicted by the models, it is confirmed that the system of north-south faults can act as a transform fault.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 17339-17
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    Carbon monoxide over the Amazon Basin during the wet season (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Measurements of the distribution of carbon monoxide in the lower atmosphere (150-5000 m) over the Amazon region of Brazil during the wet season, taken in conjunction with the 1987 NASA Global Tropospheric Experiment/Amazon Boundary Layer Experiment (ABLE 2B), are analyzed. About 100 hr of airborne, in situ CO measurements were obtained using a tunable diode laser system, providing insights into factors influencing the basin-scale distribution of CO in the Amazonian troposphere during wet season conditions. Distribution of CO over the altitudes 0.15-4.5 km was influenced by such factors as surface emissions from biological sources and long-range transport of pollutants from Northern Hemisphere sources. It is noted that the disruption of mixed layer growth and decay processes has a particularly important influence on CO concentration in the daytime lower troposphere and that the correlation of CO with O3 was positive under conditions influenced by Northern Hemisphere air and negative under all other conditions observed.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 16927-16
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    Multiple ground-based and satellite observations of global Pi 2 magnetic pulsations (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Four Pi 2 events are examined using data obtained concurrently at the Syowa-Iceland conjugate stations, the EISCAT-Magnetometer Cross, low-latitude stations HER on the nightside and KAK on the dayside, and at AMPTE/CCE in the outer magnetosphere during the period from 2300 UT on May 22 to 0300 UT on May 23, 1985. Several characteristics of Pi 2 are established on the basis of high time resolution magnetic field data. First of all, horizontal components, H and D, of the Pi 2 oscillate nearly antiphase and in-phase, respectively, between the high- and low-altitude stations in the midnight southern hemisphere. Both H and D components of the Pi 2 have nearly in-phase relationships between the nightside and the dayside stations at low altitude. The Pi 2 amplitude is larger at the high-latitude station and decreases toward low latitudes. The dominant periods of the Pi 2 are nearly identical at all stations.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 15175-15
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    The ice-core record - Climate sensitivity and future greenhouse warming (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The prediction of future greenhouse-gas-warming depends critically on the sensitivity of earth's climate to increasing atmospheric concentrations of these gases. Data from cores drilled in polar ice sheets show a remarkable correlation between past glacial-interglacial temperature changes and the inferred atmospheric concentration of gases such as carbon dioxide and methane. These and other palaeoclimate data are used to assess the role of greenhouse gases in explaining past global climate change, and the validity of models predicting the effect of increasing concentrations of such gases in the atmosphere.
    Keywords: GEOPHYSICS
    Type: Nature (ISSN 0028-0836); 347; 139-145
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    Chaotic, subduction-like downflows in a spherical model of convection in the earth's mantle (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Model calculations are described for a compressible fluid in a three-dimensional spherical shell with 80 percent of the surface heat flow generated within the model mantle. The numerical solutions are strongly chaotic, with surface planforms dominated by long curvilinear downflows reminiscent of the descending slabs in the earth's mantle. The results suggest that descending slabs play an important part in driving mantle convection, and that their chaotic evolution may influence the spatial and temporal behavior of plates and thus the dispersal and aggregation of continents.
    Keywords: GEOPHYSICS
    Type: Nature (ISSN 0028-0836); 347; 274-277
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    Extensional reactivation of an abandoned thrust - A bound on shallowing in the brittle regime (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Shallow dip angles (not greater than 45 deg) suggested by field observations of continental extensional faults are not predicted by classical isotropic Mohr-Coulomb-Anderson theory. Earthquake data indicate that normal faults exist in the upper crust with dip angles commonly as shallow as 30 deg. One explanation of the apparent conflict between theory and structural/seismic observations is that intrinsically weak, shallow-dipping pre-existing faults are preferentially reactivated. An analytical treatment clarifies the roles of geometry, intact/preexisting fault strengths and fluid pore pressures. Frictional strength ratios of 3 or greater could account for extremely shallow normal faults (dips 10-20 deg) without consideration of pore pressures in excess of the least principal stress or of principal stress systems rotated away from the gravity vector. Moderate reduction in friction (3/4) with respect to wall rock can reduce the dip to 30 deg and can account for shallow normal-slip earthquakes.
    Keywords: GEOPHYSICS
    Type: Journal of Structural Geology (ISSN 0191-8141); 12; 3, 19
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    Calibration correction of an active scattering spectrometer probe to account for refractive index of stratospheric aerosols (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The use of the active scattering spectrometer probe (ASAS-X) to measure sulfuric acid aerosols on U-2 and ER-2 research aircraft has yielded results that are at times ambiguous due to the dependence of particles' optical signatures on refractive index as well as physical dimensions. The calibration correction of the ASAS-X optical spectrometer probe for stratospheric aerosol studies is validated through an independent and simultaneous sampling of the particles with impactors; sizing and counting of particles on SEM images yields total particle areas and volumes. Upon correction of calibration in light of these data, spectrometer results averaged over four size distributions are found to agree with similarly averaged impactor results to within a few percent: indicating that the optical properties or chemical composition of the sample aerosol must be known in order to achieve accurate optical aerosol spectrometer size analysis.
    Keywords: GEOPHYSICS
    Type: Aerosol Science and Technology (ISSN 0278-6826); 12; 992-1002
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    Improved line parameters for ozone bands in the 10-micron spectral region (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A complete update of spectroscopic line parameters for the 10-micron bands of ozone is reported. The listing contains calculated positions, intensities, lower state energies, and air- and self-broadened halfwidths of more than 53,000 lines. The results have been generated using improved spectroscopic parameters obtained in a number of recent high resolution laboratory studies. A total of eighteen bands of (O-16)3 (sixteen hot bands plus the nu(1) and nu(3) fundamentals) are included along with the nu(1) and nu(3) fundamentals of both (O-16)(O-16)(O-18) and (O-16)(O-18)(O-16). As shown by comparisons of line-by-line simulations with 0.003/cm resolution balloon-borne stratospheric solar spectra, the new parameters greatly improve the accuracy of atmospheric calculations in the 10-micron region, especially for the isotopic (O-16)(O-16)(O-18) and (O-16)(O-18)(O-16) lines.
    Keywords: GEOPHYSICS
    Type: Applied Optics (ISSN 0003-6935); 29; 3667-367
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    Determination of the optical thickness and effective particle radius of clouds from reflected solar radiation measurements. I - Theory (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A method is presented for determining the optical thickness and effective particle radius of stratiform cloud layers from reflected solar radiation measurements. A detailed study is presented which shows that the cloud optical thickness (tau c) and effective particle radius (r/e/) of water clouds can be determined solely from reflection function measurements at 0.75 micron and 2.16 microns, provided tau c is not less than 4 and r(e) is not less than 6 microns. For optically thin clouds, the retrieval becomes ambiguous, resulting in two possible solutions for the effective radius and optical thickness. Adding a third channel near 1.65 micron does not improve the situation noticeably, whereas the addition of a channel near 3.70 microns reduces the ambiguity in deriving the effective radius. The effective radius determined by the above procedure corresponds to the droplet radius at some optical depth within the cloud layer.
    Keywords: GEOPHYSICS
    Type: Journal of the Atmospheric Sciences (ISSN 0022-4928); 47; 1878-189
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    Comment on 'Solar sources of interplanetary southward B(z) events responsible for major magnetic storms (1978-1979)' by F. Tang, B. T. Tsurutani, W. D. Gonzalez, S. I. Akasof, and E. J. Smith (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 12301-12
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    Solar maximum-minimum extremes in the summer noontime polar cap F region ion composition - The measurements (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 12269-12
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  • 58
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    CDAW 7 revisited - Further evidence for the creation of a near-earth substorm neutral line (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Eastman et al. (1988) have interpreted the CDAW 7 substorm of April 24, 1979, previously taken as unambiguously supporting the near-earth neutral line model of magnetospheric substorms, in terms of spatial movements of a preexisting plasma-sheet boundary layer (PSBL) and its associated current sheets across the observing ISEE 1 and 2 spacercraft. It is presently noted that, by contrast, a reinvestigation of ISEE 1 and 2 energetic particle measurements around substorm onset on short time-scales shows the observed flux pattern to require the formation of a particle source eastward of the ISEE spacecraft, well within the plasma sheet, associated with the substorm onset. Strong flows were absent prior to substorm onset, indicating the temporal nature of the event, as opposed to an encounter with a preexisting PSBL containing large flows.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 12045-12
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    Low-latitude coronal hole as the only possible explanation for the November 25, 1978, geomagnetic storm - Comment on 'Solar sources of interplanetary southward Bz events responsible for major magnetic storms (1978-1979)' by F. Tang et al (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 10717-10
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    Aircraft measurements of NO(x) over the eastern Pacific and continental United States and implications for ozone production (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Results are reported from airborne measurements of NO, NO2, O3, and CO obtained in the free troposphere (FT) and boundary layer (BL) over the western U.S. and eastern Pacific during the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 (CITE 2) in summer 1986. The aircraft instrumentation and the CITE 2 flight protocols are described, and the results are presented in extensive tables and graphs. Over the ocean the median mixing ratios for NO and NO2 were found to be 4.0 and 10.4 parts per trillion by volume (pptv), respectively, in the BL and 12.4 and 18.0 pptv in the FT; the corresponding values over land were 34.5 and 75.0 pptv in the BL and 13.0 and 36.0 pptv in the FT. in continental air masses. NO(x) is shown to be positively correlated with O3 and CO and negatively correlated with dewpoint over the ocean, whereas over land NO(x) was positively correlated with O3, CO, and dewpoint.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 10205-10
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    Peroxyacetyl nitrate measurements during CITE 2 - Atmospheric distribution and precursor relationships (1990)
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    Publication Date: 2011-08-19
    Description: Results are reported from airborne PAN measurements obtained at altitudes 0-6 km over the continental U.S. and the eastern Pacific during the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 (CITE 2) in summer 1986. The CITE 2 flights and instrumentation are described, and the results are presented in extensive graphs and characterized in detail. It is shown that PAN is an important reactive N-containing species in the troposphere. Although the PAN mixing ratios were highly variable, in general high mixing ratios of 100-300 parts per trillion by volume (pptv) were found at 4-6 km, and very low ratios (5-20 pptv) were detected in the marine boundary layer. Good correlation was seen between the CITE 2 PAN values and those for O3, NO(y), NO(x), HNO3, C2H6, CO, and CFCl3.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 10163-10
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    Calibration of the C-14 timescale over the past 30,000 years using mass spectrometric U-Th ages from Barbados corals (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Uranium-thorium ages obtained by mass spectrometry from corals raised off the island of Barbados confirm the high precision of this technique over at least the past 30,000 years. Comparison of the U-Th ages with C-14 ages obtained on the Holocene samples shows that the U-Th ages are accurate, because they accord with the dendrochronological calibration. Before 9,000 yr BP, the C-14 ages are systematically younger than the U-Th ages, with a maximum difference of about 3500 yr at about 20,000 yr BP. The U-Th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration.
    Keywords: GEOPHYSICS
    Type: Nature (ISSN 0028-0836); 345; 405-410
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    Heterogeneous reactions on nitric acid trihydrate (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The first direct measurements are reported of the reaction probabilities at stratospheric temperatures for two important heterogeneous reactions on nitric acid trihydrate (NAT), the compound which makes up the predominant, type I form of polar stratospheric cloud (PSC). Sticking coefficients and solubilities of HCl and NAT, which are important in modeling physicochemical processes in the stratosphere, are also reported. The results show that the conversion of the chlorine reservoir species in the stratosphere to photochemically active forms can occur within a few days of the first appearance of type I PSCs during the polar winter.
    Keywords: GEOPHYSICS
    Type: Nature (ISSN 0028-0836); 345; 333-335
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    The distortion of the magnetotail equilibrium structure by a net cross-tail magnetic field (1990)
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    Publication Date: 2011-08-19
    Description: Explicit solutions are presented for quiet, quasi-static magnetotail configurations in the presence of a net cross-tail magnetic field component in addition to field components associated with tail flaring. The solutions are derived using the general three-dimensional equilibrium theory of Birn (1987). It is found that the net By(N) field varies only weakly along field lines and across the tail. The presence of the net By(N) in the neutral sheet implies that a part of the cross-tail current becomes field-aligned, flowing from the southern to the northern hemisphere for By(N) larger than zero and from north to south for By(n) less than zero. The deformations of magnetic flux surfaces suggest that there may be a class of field lines extending from the earth into the magnetosheath region through the low-latitude flanks of the tail. A topological connection is found of the low-latitude region near the magnetopause with the plasma sheet boundary layer, separating closed plasma sheet and open lobe field lines.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 8019-802
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  • 65
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    Outgoing long-wave radiation computed from HIRS2/MSU soundings (1990)
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    Publication Date: 2011-08-19
    Description: Fields of outgoing long-wave radiation (OLR) have been computed using geophysical parameters retrieved from analysis of HIRS2/MSU sounding data as input to a modified version of the Wu-Kaplan radiation code used in the Goddard Laboratory for Atmospheres fourth-order general circulation model. Monthly mean results for 1979 agree with monthly mean OLR fields measured by the Nimbus 7 earth radiation budget (ERB) broadband narrow field of view instrument within standard deviations of 6.3 W/sq m but with a global mean bias of 8.0 W/sq m. Results are shown for July 1979. The areas of disagreement between high-resolution infrared radiation sounder OLR and ERB OLR are small but spatially coherent with patterns which may be related to sampling differences. The difference patterns are much less extensive than those between OLR derived from advanced very high resolution radiometer 11-micron observations and ERB OLR.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 7579-760
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    Measuring tropospheric HNO3 - Problems and prospects for Nylon filter and mist chamber techniques (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A series of laboratory and field measurements was performed to evaluate the mist chamber technique for determining tropospheric HNO3 concentrations. Both the mist chamber and standard Nylon filter techniques exhibit high collection efficiency and excellent agreement measuring HNO3 vapors from a permeation source. When simultaneously sampling ambient air in eastern Virginia, the Nylon filter measured an average of 70 percent higher HNO3 concentration than the mist chamber technique. The results indicate that O3 causes a low-level positive artifact interference in HNO3 measurements performed with the filter technique. This O3-induced error is small, however, compared to the large difference between atmospheric HNO3 concentrations determined with the two techniques. It is hypothesized that unidentified (organic?) nitrogen species in the atmosphere react for form NO3(-) on the filter and this phenomenon may interfere with Nylon filter measurements of HNO3 vapor. These potential interferences did not appear to affect measurements of HNO3 with the mist chamber method.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 7553-756
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    Effect of solar proton events on the middle atmosphere during the past two solar cycles as computed using a two-dimensional model (1990)
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    Publication Date: 2011-08-19
    Description: This paper investigates the effects of solar proton events (SPEs) on the middle atmosphere during the past two solar cycles (1963-1984), by examining changes in the production of odd nitrogen, NO(y), and ozone and using a proton energy degradation scheme to derive ion pair production rates. These calculations show that NO(y) is not substantially changed over a solar cycle by SPEs; significant SPEs last only 1-5 days, tend to occur near solar maximum, and are typically months to years apart, preventing a build up of SPE-produced NO(y). Fractional ozone changes are even smaller than the fractional NO(y) changes and are significant only for the August 1972 SPE. Ozone, like NO(y), returns to its ambient levels on time scales of several months to a year.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 7417-742
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  • 68
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    Analysis of the eight-year trend in ozone depletion from empirical models of solar backscattered ultraviolet instrument degradation (1990)
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    Publication Date: 2011-08-19
    Description: Arguments are presented showing that the basic empirical model of the solar backscatter UV (SBUV) instrument degradation used by Cebula et al. (1988) in their analysis of the SBUV data is likely to lead to an incorrect estimate of the ozone trend. A correction factor is given as a function of time and altitude that brings the SBUV data into approximate agreement with the SAGE, SME, and Dobson network ozone trends. It is suggested that the currently archived SBUV ozone data should be used with caution for periods of analysis exceeding 1 yr, since it is likely that the yearly decreases contained in the archived data are too large.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 7403-741
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    Balloon Intercomparison Campaigns - Results of remote sensing measurements of HCl (1990)
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    Publication Date: 2011-08-19
    Description: The balloon-borne instruments used in the two Balloon Intercomparison Campaigns in 1982 and 1983 to measure stratospheric HCl included five different IR spectrometers, three of which operated in the solar absorption mode and two in emission mode (at distinctly different wavelengths). This paper describes the instruments and the data reduction and analysis procedures used in each case, together with the sources and estimated magnitudes of associated errors. Comparisons are made between different techniques (absorption vs emission) used on the same gondola, as well as between the same technique used on different gondolas. The final results yield a mean profile of HCl concentration between 18 and 40 km altitude. The absolute accuracy of the final profile is estimated to be no worse than 10 percent.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric Chemistry (ISSN 0167-7764); 10; 237-272
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    Intercomparison of measurements of stratospheric hydrogen fluoride (1990)
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    Publication Date: 2011-08-19
    Description: Observations of the vertical profile of hydrogen fluoride (HF) vapor in the stratosphere and of the vertical column amounts of HF above certain altitudes were made using a variety of spectroscopic instruments in the 1982 and 1983 Balloon Intercomparison Campaigns. Both emission instruments working in the far-infrared spectral region and absorption instruments using solar occultation in the 2.5-micron region were employed. No systematic differences were seen in results from the two spectral regions. A mean profile from 20 - 45 km is presented, with uncertainties ranging from 20 to 50 percent. Total columns measured from ground and from 12 km are consistent with the profile if the mixing ratio for HF is small in the troposphere and low stratosphere.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric Chemistry (ISSN 0167-7764); 10; 219-236
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    Ozone measurements from the Balloon Intercomparison Campaign (1990)
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    Publication Date: 2011-08-19
    Description: Measurements of the Balloon Intercomparison Campaign (BIC), conducted during fall, 1982 (BIC-1) and summer, 1983 (BIC-2), are reported. Results of five remote and two in situ techniques agree (with a few exceptions) within 95-percent confidence level uncertainties and generally within 15 percent above 20 km. Weighted mean profiles, which best represent conditions during the campaign, are used as a comparison standard. Accuracies of experiments indicated by BIC generally confirm estimated uncertainties for ECC sondes, UV photometry, and microwave emission experiments, are somewhat better for far-IR emission and IR absorption experiments, and are somewhat worse for IR emission and solar UV absorption experiments. The large collection of BIC measurements confirms a problem reported earlier with current theoretical modeling of ozone near 40 km.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric Chemistry (ISSN 0167-7764); 10; 181-218
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    Intercomparison of remote measurements of stratospheric NO and NO2 (1990)
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    Publication Date: 2011-08-19
    Description: During the 1982 and 1983 Balloon Intercomparison Campaigns, the vertical profile of stratospheric NO2 was measured remotely by nine instruments and that of NO by two. Total overhead columns were measured by two more instruments. Between 30 and 35 km, where measurements overlapped, agreement between NO profiles was within + or - 30 percent, which is better than the accuracies claimed by the experimenters. Between 35 and 40 km, there was similarly good agreement between NO2 profiles, but below 30 km, differences of greater than a factor of 3 were found. In the second campaign, NO2 values from most instruments agreed within their quoted errors, except that the Oxford radiometer gave much lower values; the first campaign and the column measurements show a more uniform spread of results.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric Chemistry (ISSN 0167-7764); 10; 111-144
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    Analysis of the origins and implications of the O-18 content of stratospheric water vapor (1990)
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    Publication Date: 2011-08-19
    Description: Factors influencing the O-18 content of stratospheric H2O are reviewed in order to provide a theoretical framework for the interpretation of measurements of this quantity, which are now becoming available. Depletions in O-18 of 5-10 percent in stratospheric H2O are expected based on the known correlation between that of D and O-18 in tropospheric H2O and observed measurements of large (typically 50 percent) depletions of D in stratosphere H2O. H2O formed in the stratosphere as a result of oxidation of CH4 can be expected to reflect primarily the O-18 content of stratospheric O2, which is the same as that of tropospheric O2 (slightly enhanced with respect to standard mean ocean water). Thus, a reduction in the O-18 depletion is expected with increasing altitude, but not a large enhancement in O-18 in upper stratospheric H2O as found in recent far infrared measurements. The observed large enhancement of O-18 in stratospheric O3 is not expected to be reflected in stratospheric H2O. Necessary laboratory data for the improved quantification of these effects are reviewed.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric Chemistry (ISSN 0167-7764); 10; 39-57
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  • 74
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    Hydrogen constituents of the mesosphere inferred from positive ions - H2O, CH4, H2CO, H2O2, and HCN (1990)
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    Publication Date: 2011-08-19
    Description: The concentrations in the mesosphere of H2O, CH4, H2CO, H2O2, and HCN were inferred from data on positive ion compositions, obtained from one mid-latitude and four high-latitude rocket flights. The inferred concentrations were found to agree only partially with the ground-based microwave measurements and/or model prediction by Garcia and Solomon (1985). The CH4 concentration was found to vary between 70 and 4 ppb in daytime and 900 and 100 ppbv at night, respectively. Unexpectedly high H2CO concentrations were obtained, with H2CO/H2O ratios between 0.0006 and 0.1, and a mean HCN volume mixing ratio of 6 x 10 to the -10th was inferred.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 5613-563
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    Heterodyne spectrophotometry of ozone in the 9.6-micron band using a tunable diode laser (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Tunable diode laser heterodyne spectrophotometry (TDLHS) has been used to make extremely high resolution (0.0003/cm) solar spectra in the 9.6-micron ozone band. Observations have shown that a signal-to-noise ratio of 120:1 (about 30 percent of theoretical) for an integration time of 1/8 s can be achieved at a resolution of 0.0013 wave numbers. The spectral data have been inverted to yield a total column amount of ozone, in good agreement with that measured at the nearby NOAA ozone monitoring facility in Boulder, Colorado. Line positions for several ozone lines in the spectral region 996-997/cm are reported. Recent improvements have produced a signal-to-noise ratio of 95:1 (about 40 percent of theoretical) at 0.0003/cm and extended the range of wavelengths which can be observed.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 5567-557
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    Comparison of stratospheric ozone profiles and their seasonal variations as measured by lidar and Stratospheric Aerosol and Gas Experiment during 1988 (1990)
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    Publication Date: 2011-08-19
    Description: A ground-based, high power, laser remote sensing system for measurements of stratospheric ozone concentration profiles has been in operation at the Jet Propulsion Laboratory Table Mountain Facility located in southern California, since January 1988. The seasonal variations observed in the ozone profiles, during 1988 and as a function of altitude, are described here. These profiles are compared with those from the Stratospheric Aerosol and Gas Experiment satellite instrument made within a radius of 1000 km from the lidar and also with the zonal mean measurements made in the band 34.4 +/- 5 deg. Comparison with the proposed new CIRA ozone reference model has also been carried out. The seasonal variations, between 25 and 50 km, observed by the two instruments and indicated by the reference model are in good agreement.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 5605-561
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    Comment on 'Detection of multiply deuterated methane in the atmosphere' (1990)
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    Publication Date: 2011-08-19
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 659
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    CASA Uno GPS orbit and baseline experiments (1990)
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    Publication Date: 2011-08-19
    Description: CASA Uno data from sites distributed in longitude from Australia to Europe have been used to determine orbits of the GPS satellites. The characteristics of the orbits determined from double difference phase have been evaluated through comparisons of two-week solutions with one-week solutions and by comparisons of predicted and estimated orbits. Evidence of unmodeled effects is demonstrated, particularly associated with the orbit planes that experience solar eclipse. The orbit accuracy has been assessed through the repeatability of unconstrained estimated baseline vectors ranging from 245 km to 5400 km. Both the baseline repeatability and the comparison with independent space geodetic methods give results at the level of 1-2 parts in 100,000,000. In addition, the Mojave/Owens Valley (245 km) and Kokee Park/Ft. Davis (5409 km) estimates agree with VLBI and SLR to better than 1 part in 100,000,000.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 643-646
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    Molten (Mg0.88Fe0.12)2SiO4 at lower mantle conditions - Melting products and structure of quenched glasses (1990)
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    Publication Date: 2011-08-19
    Description: Infrared spectra of quenched magnesium silicate glasses synthesized by fusing olivine at pressures in excess of 50 GPa and temperatures greater than 2500 K demonstrate that silicon is dominantly present in four-fold coordination with respect to oxygen within these quenched glasses. This low coordination is attributed, by analogy with the structural behavior of glasses compressed at 300 K, to the instability of higher coordinations in glasses of these compositions on decompression. Spectra of glasses formed in a hydrous environment document that water is extensively soluble in melts at these high pressures and temperatures. Also, these results are consistent with the melting of (Mg0.88Fe0.12)2SiO4 compositions to liquids near pyroxene in stoichiometry under these conditions, with iron-rich magnesiowuestite being the liquidus phase.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 635-638
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    Laboratory studies of the electrical conductivity of silicate perovskites at high pressures and temperatures (1990)
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    Publication Date: 2011-08-19
    Description: The electrical conductivities of two silicate perovskites and a perovskite-magnesiowuestite assemblage, all having an atomic ratio of Mg to Fe equal to 0.88/0.12, have been measured with alternating current and direct current (dc) techniques at simultaneously high pressures and temperatures. Measurements up to pressures of 80 GPa and temperatures of 3500 K, using a laser-heated diamond anvil cell, demonstrate that the electrical conductivity of these materials remains below 10-3 S/m at lower mantle conditions. The activation energies for electrical conduction are between 0.1 and 0.4 eV from the data, and the conduction in these perovskites is ascribed to an extrinsic electronic process. The new measurements are in agreement with a bound that was previously obtained from dc measurements for the high-PT conductivity of perovskite-dominated assemblages. The results show that the electrical conductivity of (Mg/0.88/Fe/0.12)SiO3 perovskite differs significantly from that of the earth's deep mantle, as inferred from geophysical observations.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 5067-507
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    Mapping transformations for broadband atmospheric radiation calculations (1990)
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    Publication Date: 2011-08-19
    Description: Two methods of mapping the line-by-line absorption coefficient (k) spectrum onto a new variable to produce a set of k coefficients which can be used for accurate and efficient broadband radiative transfer calculations in vertically inhomogeneous, nongray scattering atmospheres are described. These methods are intended for applications for which the less accurate correlated-k method is inadequate. These methods are tested for model atmospheres containing CO2 and H2O, with pressure in the range 0.05-0.9 bar. The results obtained differed by no more than 1 or 2 percent from the line-by-line results if the number of k coefficients was about 100 times less than the number required for the line-by-line calculation. These algorithms can be used for gas mixtures and for a variety of pressure-temperature profiles.
    Keywords: GEOPHYSICS
    Type: Journal of Quantitative Spectroscopy and Radiative Transfer (ISSN 0022-4073); 43; 191-199
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    Do interplanetary Alfven waves cause auroral activity? (1990)
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    Publication Date: 2011-08-19
    Description: A recent theory holds that high-intensity, long-duration, continuous auroral activity (HILDCAA) is caused by interplanetary Alfven waves propagating outward from the sun. A survey of Alfvenic intervals in over a year of ISEE 3 data shows that while Alfvenic intervals often accompany HILDCAAs, the reverse is often not true. There are many Alfvenic intervals during which auroral activity (measured by high values of the AE index) is very low, as well as times of high auroral activity that are not highly Alfvenic. This analysis supports the common conclusion that large AE values are associated with a southward interplanetary field of sufficient strength and duration. This field configuration is independent of the presence of Alfven waves (whether solar generated or not) and is expected to occur at random intervals in the large-amplitude stochastic fluctuations in the solar wind.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 4327-433
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    Equilibrium structure of the plasma sheet boundary layer-lobe interface (1990)
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    Publication Date: 2011-08-19
    Description: Observations are presented which show that plasma parameters vary on a scale length smaller than the ion gyroradius at the interface between the plasma sheet boundary layer and the lobe. The Vlasov equation is used to investigate the properties of such a boundary layer. The existence, at the interface, of a density gradient whose scale length is smaller than the ion gyroradius implies that an electrostatic potential is established in order to maintain quasi-neutrality. Strongly sheared (scale lengths smaller than the ion gyroradius) perpendicular and parallel (to the ambient magnetic field) electron flows develop whose peak velocities are on the order of the electron thermal speed and which carry a net current. The free energy of the sheared flows can give rise to a broadband spectrum of electrostatic instabilities starting near the electron plasma frequency and extending below the lower hybrid frequency.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 2313-231
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    Evaluation of GPS estimates of relative positions from central California, 1986-1988 (1990)
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    Publication Date: 2011-08-19
    Description: Estimates of long-term precision and accuracy of interstation vectors using GPS are reported. Precision is estimated from three experiments conducted in central California over a period of 1.2 years. Horizontal precision is 3 to 8 mm for baseline vectors between 100 and 450 km in length, and the vertical precision ranges from 11 to 33 mm. Accuracy is assessed by comparing VLBI estimates with results from six GPS experiments conducted at Mojave and Palos Verdes over a period of 2.2 years. Rates for all vector components agree with VLBI within one standard deviation.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 2433-243
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    Are there interactions of iodine and sulfur species in marine air photochemistry? (1990)
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    Publication Date: 2011-08-19
    Description: The effects of dimethyl sulfide (DMS) and methyl iodide (MI) emissions are analyzed using a two-dimensional photochemical model of a marine tropical tropospheric synoptic system. The model traces the atmospheric transformation cycles of the emissions to aerosols. The study is focused on remote tropical ocean regions and includes simulations of the spatial and diurnal variations of various iodine and sulfur species, and the species OH, HO2, and H2O2. One line of analysis leads to the conclusion that the reaction IO + DMS yields DMSO + I may play a significant role in destroying DMS if it proceeds at the published fast rate. Alternative lines of analyses are presented.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 22319-22
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    Recent trends in stratospheric ozone - Implications of ozone and temperature correlation (1990)
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    Publication Date: 2011-08-19
    Description: The relation between ozone and temperature in the upper stratosphere is used to estimate the drift in the SBUV spectrometer on Nimbus-7 and the linear trend in ozone from 1979 to 1986. The ozone and temperature variabilities are coupled through chemical and dynamical processes. In the upper stratosphere they are anticorrelated through temperature-dependent loss rates, while in the lower stratosphere their variabilities are positively correlated through dynamical coupling. These relations are used to determine the ozone sensitivity to temperature and ozone trends in terms of temperature trends. It is shown that in the upper stratosphere (approximately 2 mbar), the eight-year trend in ozone is a manifestation of dynamical perturbations. It varies from about +4 percent at the equator to about -1 to -2 percent at high latitudes in both hemispheres.
    Keywords: GEOPHYSICS
    Type: Indian Journal of Radio and Space Physics (ISSN 0367-8393); 19; 534-541
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    Wintertime nitric acid chemistry - Implications from three-dimensional model calculations (1990)
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    Publication Date: 2011-08-19
    Description: A three-dimensional simulation of the evolution of HNO3 has been run for the winter of 1979. Winds and temperatures are taken from a stratospheric data assimilation analysis, and the chemistry is based on Limb Infrared Monitor of the Stratosphere (LIMS) observations. The model is compared to LIMS observations to investigate the problem of 'missing' nitric acid chemistry in the winter hemisphere. Both the model and observations support the contention that a nitric acid source is needed outside of the polar vortex and north of the subtropics. Observations suggest that HNO3 is not dynamically controlled in middle latitudes. The model shows that given the time scales of conventional chemistry, dynamical control is expected. Therefore, an error exists in the conventional chemistry or additional processes are needed to bring the model and data into agreement. Since the polar vortex is dynamically isolated from the middle latitudes, and since the highest HNO3 values are observed in October and November, a source associated solely with polar stratospheric clouds cannot explain the deficiencies in the chemistry. The role of heterogeneous processes on background aerosols is reviewed in light of these results.
    Keywords: GEOPHYSICS
    Type: Journal of the Atmospheric Sciences (ISSN 0022-4928); 47; 2696-270
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  • 88
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    DE 2 observations of disturbances in the upper atmosphere during a geomagnetic storm (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Results are presented of physical interpretations of a sequence of in situ measurements taken in the midlatitude dusk sector during the geomagnetic storm of November 24, 1982 by instruments on board the DE-2 spacecraft in polar orbit. The results represent the first comparison of nearly simultaneous measurements, obtained at different seasons in a common local time sector, of storm disturbances in dc electric fields, zonal ion convection, zonal winds, gas composition and temperature, and electron density and temperature.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 21017-21
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  • 89
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    Cleft contribution to ring current formation (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The storm time transport of ionospheric plasma from the 'cleft fountain' to the plasma sheet and ring current is investigated by means of three-dimensional trajectory codes. Using observations to define the source location and flow rate, test particles are traced during a 'taillike' to 'dipolelike' reconfiguration of the geomagnetic field. Emphasis is placed on the behavior of heavy ions of low charge state, O(+). As a result of their long periods of gyration, these ions are highly sensitive to rapid field variations and possibly display transient nonadiabatic motions. It is demonstrated that O(+) which have originated in the high-latitude ionosphere but which find themselves in the vicinity of the equator at substorm onset can experience considerable energization (from several keV up to several hundred keV) and pitch angle increase leading to trapping, as an effect of the induced electric field.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 20937-20
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  • 90
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    IMP 8 magnetic observations of the high-latitude tail boundary - Locations and force balance (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 20759-20
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  • 91
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    An approach to the detection of long-term trends in upper stratospheric ozone from space (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A central problem in the detection of long-term trends in the upper stratospheric ozone from orbiting remote sensors involves the separation of instrument drifts from true geophysical changes. Periodic flights of a Solar Backscatter Ultraviolet radiometer (SSBUV) on the Space Shuttle will allow the detection of drifts in optically identical sensors (SBUV/2) carried on operational satellites. A detailed simulation of the SSBUV and SBUV/2 datasets defines the accuracy that can be attained by the in-orbit calibration procedure. The repeatability of the SSBUV calibration from one flight to the next is the most critical variable in the analysis. A repeatability near + or - 1.0 percent is essential for detection and correction of drifts in the SBUV/2 radiance measurements. The simulations show that true geophysical trends in backscattered radiance can be inferred to an accuracy of approximately + or - 1.0 percent per decade when SSBUV flies approximately once per year and provides a precise calibration correction to the SBUV/2 dataset over a full decade.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Oceanic Technology (ISSN 0739-0572); 7; 734-740
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  • 92
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    Mechanism of the gamma-beta phase transformation of Mg2SiO4 at high temperature and pressure (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The results of experiments on the phase transformation of Mg2SiO4 olivine at 15 GPa pressure in a multianvil cell are reported. At this pressure and a temperature of 900 C, early formed metastable gamma-spinel transforms partially to the beta-phase. The observed microstructures, which are similar to those in shocked meteorites, show that the gamma-to-beta transformation can occur either by diffusion-controlled growth or by a martensitic mechanism, depending on how far the pressure-temperature conditions deviate from their values at phase equilibrium. The results suggest that the diffusion-controlled mechanism is most likely to operate at the beta/gamma phase boundary in the mantle, but martensitic beta-to-gamma transformation might occur in subduction zones and could reduce the shear strength of the subducting slab.
    Keywords: GEOPHYSICS
    Type: Nature (ISSN 0028-0836); 348; 628-631
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  • 93
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    The GEM-T2 gravitational model (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The GEM-T2 is the latest in a series of Goddard Earth Models of the terrestrial field. It was designed to bring modeling capabilities one step closer towards ultimately determining the TOPEX/Poseidon satellite's radial position to an accuracy of 10-cm RMS (root mean square). It also improves models of the long wavelength geoid to support many oceanographic and geophysical applications. The GEM-T2 extends the spherical harmonic field to include more than 600 coefficients above degree 36 (which was the limit for its predecessor, GEM-T1). Like GEM-T1, it was produced entirely from satellite tracking data, but it now uses nearly twice as many satellites (31 vs. 17), contains four times the number of observations (2.4 million), has twice the number of data arcs (1132), and utilizes precise laser tracking from 11 satellites. The estimation technique for the solution has been augmented to include an optimum data weighting procedure with automatic error calibration for the gravitational parameters. Results for the GEM-T2 error calibration indicate significant improvement over previous satellite-only models. The error of commission in determining the geoid has been reduced from 155 cm in GEM-T1 to 105 cm for GEM-T2 for the 36 x 36 portion of the field, and 141 cm for the entire model. The orbital accuracies achieved using GEM-T2 are likewise improved. Also, the projected radial error on the TOPEX satellite orbit indicates 9.4 cm RMS for GEM-T2, compared to 24.1 cm for GEM-T1.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 22043-22
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  • 94
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    Measurement of horizontal motions in Alaska using very long baseline interferometry (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Results are presented on an analysis of VLBI measurements performed between 1984 and 1990 by means of a network of 53 sites in Alaska, the Yukon Territory, and the conterminous United States to determine the extent of horizontal motions in Alaska. Results are presented in two ways, one showing the evolution of individual baselines and the other yielding site velocities; both approaches use VLBI data from other permanent stations in order to define a global reference frame. It was found that VLBI sites within the Alaska-Aleutian subduction boundary zone (Yakataga, Kodiak, and Sand Point) had higher instantaneous velocities relative to eastern North America than the interior sites of Alaska. The results of Yakataga data modeling suggests that the observed motion is the result of elastic straining of the overriding plate due to a locked main thrust zone with a component of oblique slip.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 21991-22
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  • 95
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    Tectonic motion and deformation from satellite laser ranging to Lageos (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Data on satellite laser ranging (SLR) to Lageos aquired during the period 1978-1988 are analyzed on the basis of the precise modeling of the orbit dynamics of Lageos, producing estimates of tectonic motion for 22 sites located on seven major plates. It was estimated that intraplate motion within northern Europe is below the 2 mm/yr level in absolute rate, in agreement with conclusions of Zoback et al. (1989) regarding the stress across the region. A comparison of SLR geodesic rates with those from NUVEL-1 and AMO-2 models showed high correlations between tracking sites that are well within plate interiors, but displayed small but significant departures from unity in slope which are attributed to the possibility of recent changes in relative velocities or geologic time scale uncertainties. For lines crossing the Nnorth Atlantic, the San Andreas fault, and within the Basin and Range province, the geodesic rates determined by SLR are in good agreement with those determined by VLBI.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 22013-22
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  • 96
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    Thermal infrared spectral character of Hawaiian basaltic glasses (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Thermal IR reflectance spectra of exposed surfaces of Hawaiian basalt samples from Mauna Loa and Kilauea show systematic changes with age. Spectra of fresh glass collected from active lava flows showed evidence of a strong degree of disorder. After a few weeks of exposure to the laboratory environment, spectra of the top surfaces of these samples began to exhibit spectral features suggestive of ordering into silicate chainlike ansd sheetlike units. With progressive aging, features of apparent sheetlike structures became the preferred mode.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 21657-21
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  • 97
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    High pressure-temperature electrical conductivity of magnesiowustite as a function of iron oxide concentration (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The electrical conductivity of (Mg, Fe)O magnesiowustite containing 9 and 27.5 mol pct FeO has been measured at simultaneously high pressures (30-32 GPa) and temperatures using a diamond anvil cell heated with a continuous wave Nd:YAG laser and an external resistance heater. The conductivity depends strongly on the FeO concentration at both ambient and high pressures. At the pressures and temperatures of about 30 GPa and 2000 K, conditions expected in the lower mantle, the magnesiowustite containing 27.5 percent FeO is 3 orders of magnitude more conductive than that containing 9 percent FeO. The activation energy of magnesiowustite decreases with increasing iron concentration from 0.38 (+ or - 0.09) eV at 9 percent FeO to 0.29 (+ or - 0.05) eV at 27.5 percent FeO.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 21609-21
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  • 98
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    A Van de Graaf source mechanism for middle atmospheric vertical electric fields (1990)
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    Publication Date: 2011-08-19
    Description: It is proposed that meteoric and other debris descending through the mesosphere constitute a natural Van de Graaf generator for vertical electric fields within the mesosphere. Dust and aerosol particles falling from above 85 km are charged negatively in the upper D-region. Charge is lost in the region below 70 km. This net charge transport creates a vertical polarization electric field. Calculated fields are in the range of 10 mV/m for the average input of meteoric debris. Observed vertical electric fields are confined to a few occasions when large fields of the order of 4 V/m are observed to maximize at 65 km. Calculated fields from this model also maximize at this altitude, but a special event with increased dust density or another mechanism to increase relative vertical velocity is required to explain the large fields. Such large values are the exception rather than the rule for D-region vertical electric fields.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics (ISSN 0021-9169); 52; 695-705
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  • 99
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    Melting relations in the iron-sulfur system at ultra-high pressures - Implications for the thermal state of the earth (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The melting temperatures of FeS-troilite and of a 10-wt-pct sulfur iron alloy have been measured to pressures of 120 and 90 GPa, respectively. The results document that FeS melts at a temperature of 4100 (+ or - 300) K at the pressure of the core-mantle boundary. Eutecticlike behavior persists in the iron-sulfur system to the highest pressures of measurements, in marked contrast to the solid-solutionlike behavior observed at high pressures in the iron-iron oxide system. Iron with 10-wt-pct sulfur melts at a similar temperature as FeS at core-mantle boundary conditions. If the sole alloying elements of iron within the core are sulfur and oxygen and the outer core is entirely liquid, the minimum temperature at the top of the outer core is 4900 (+ or - 400) K. Calculations of mantle geotherms dictate that there must be a temperature increase of between 1000 and 2000 K across thermal boundary layers within the mantle. If D-double-prime is compositionally stratified, it could accommodate the bulk of this temperature jump.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 19299-19
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  • 100
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    On the consequences of strong stable stratification at the top of earth's outer core (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The consequences of strong stable stratification at the top of the earth's fluid outer core are considered, concentrating on the generation of the geomagnetic secular variation. It is assumed that the core near the core-mantle boundary is both strongly stably stratified and free of Lorentz forces: it is found that this set of assumptions severely limits the class of possible motions, none of which is compatible with the geomagnetic secular variation. Relaxing either assumption is adequate: tangentially geostrophic flows are consistent with the secular variation if the assumption that the core is strongly stably stratified is relaxed (while retaining the assumption that Lorentz forces are negligible); purely toroidal flows may explain the secular variation if Lorentz forces are included.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 2081-208
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