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  • Chemistry  (114,948)
  • LUNAR AND PLANETARY EXPLORATION  (6,984)
  • 1995-1999  (38,545)
  • 1980-1984  (36,928)
  • 1975-1979  (33,097)
  • 1955-1959  (13,362)
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  • 1
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1978-10-13
    Description: Picosecond spectroscopy is a relatively new field of science that utilizes ultrashort laser pulses to monitor events taking place in the 10(-12) second regime. The continuing development of picosecond spectroscopy has made possible the detection and measurement of the primary events in many physical and tiological processes. This article describes a currently used picosecond spectroscopy system that is capable of reliably recording picosecond events. Two areas of picosecond research are discussed; one concerns the interaction of electrons in fluids, and the second the primary events in vision.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rentzepis, P M -- New York, N.Y. -- Science. 1978 Oct 13;202(4364):174-82.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/694523" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Electrons ; *Kinetics ; Lasers ; Protons ; *Retinal Pigments ; *Rhodopsin ; Spectrum Analysis/*methods ; Temperature ; *Vision, Ocular
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  • 2
    Publication Date: 1979-12-14
    Description: The structure and absolute stereoconfigurations of four adenosine adducts with (+/-)-7 alpha,8 beta-dihydroxy-9 beta, 10 beta-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene (BPDE) and their deoxyadenosine analogs have been determined. They result from both cis and trans addition of the N6 amino group of ademine to the 10 position of both enantiomers of BDPE. This was determined from studies of the nuclear magnetic resonance spectra, mass spectra, and circular dichroism spectra, as well as from their pKa values and chemical reactivities.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jeffrey, A M -- Grzeskowiak, K -- Weinstein, I B -- Nakanishi, K -- Roller, P -- Harvey, R G -- New York, N.Y. -- Science. 1979 Dec 14;206(4424):1309-11.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/316186" target="_blank"〉PubMed〈/a〉
    Keywords: *Benzopyrenes ; Chemical Phenomena ; Chemistry ; Circular Dichroism ; Dna ; *Deoxyadenosines/analogs & derivatives ; Magnetic Resonance Spectroscopy ; Mass Spectrometry ; Molecular Conformation ; Mutation ; Stereoisomerism
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  • 3
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-08-14
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Klotz, I M -- Haney, D N -- King, L C -- New York, N.Y. -- Science. 1981 Aug 14;213(4509):724-31.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7256275" target="_blank"〉PubMed〈/a〉
    Keywords: Anemia, Sickle Cell/*drug therapy ; Aspirin/analogs & derivatives/therapeutic use ; Chemical Phenomena ; Chemistry ; *Hemoglobin, Sickle ; Humans ; Protein Binding/drug effects ; Protein Conformation ; Salicylates/*therapeutic use ; Solubility ; Structure-Activity Relationship
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  • 4
    Publication Date: 1982-09-10
    Description: Alkyl-Substituted gamma-butyrolactones were synthesized and tested for their convulsant and anticonvulsant actions in mice and guinea pigs. The alpha-substituted compounds, alpha, alpha-dimethyl-, and alpha-ethyl-alpha-methyl-gamma-butyrolactone were anticonvulsant compounds with a spectrum of activity similar to that of ethosuximide. In contrast, beta-substituted compounds were convulsant agents similar to picrotoxinin. The alpha-substituted-gama-butyrolactones represent a new class of anticonvulsant drug with experimental and clinical potential.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Klunk, W E -- McKeon, A -- Covey, D F -- Ferrendelli, J A -- GM-07200/GM/NIGMS NIH HHS/ -- GM-24483/GM/NIGMS NIH HHS/ -- NS-14834/NS/NINDS NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1982 Sep 10;217(4564):1040-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6810462" target="_blank"〉PubMed〈/a〉
    Keywords: *4-Butyrolactone/analogs & derivatives/*therapeutic use/toxicity ; Animals ; *Anticonvulsants ; Chemical Phenomena ; Chemistry ; Convulsants ; Drug Evaluation, Preclinical ; Electroencephalography ; Epilepsy, Absence/drug therapy ; Ethosuximide/pharmacology ; *Furans/*therapeutic use ; Guinea Pigs ; Mice ; Structure-Activity Relationship ; Trimethadione/pharmacology
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  • 5
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1983-05-06
    Description: Crystalline cholesterol undergoes a phase transition a few degrees below human body temperature. The high-temperature form has an unusually complex structure with 16 independent molecules. In the transition two molecules change side chain conformation, four reorient about their long axes, and ten remain unchanged. The transition mechanism implies relatively nonspecific intermolecular interactions, qualitatively consistent with the behavior of cholesterol in biomembranes. The transition preserves a remarkably closely obeyed pseudosymmetry present in the structure.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hsu, L Y -- Nordman, C E -- GM15259/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1983 May 6;220(4597):604-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6836303" target="_blank"〉PubMed〈/a〉
    Keywords: Body Temperature ; Chemical Phenomena ; Chemistry ; *Cholesterol ; Crystallization ; Humans ; Magnetic Resonance Spectroscopy ; Molecular Conformation
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  • 6
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-07-20
    Description: The iron-carbon monoxide stretching mode and the iron-carbon-oxygen bending mode in carbon monoxide-bound cytochrome oxidase have been assigned at 520 and 578 cm-1, respectively. The frequencies, widths, and intensities of these modes show that the Fe-C-O grouping in carbon monoxide-cytochrome a3 is linear but tilted from the normal to the heme plane; that the iron-histidine bond in both five- and six-coordinate cytochrome a3 is strained; and that the carbon monoxide and the proximal histidine each have characteristic, well-defined orientations in all molecules. These data can account for the binding affinities of carbon monoxide and dioxygen under physiological conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Argade, P V -- Ching, Y C -- Rousseau, D L -- New York, N.Y. -- Science. 1984 Jul 20;225(4659):329-31.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6330890" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Carbon Monoxide/metabolism ; Cattle ; Chemical Phenomena ; Chemistry ; Electron Transport Complex IV/*metabolism ; Myoglobin/metabolism ; Oxidation-Reduction ; Oxygen/metabolism ; Spectrum Analysis, Raman
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  • 7
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1983-05-06
    Description: Arachidonic acid plays a central role in a biological control system where such oxygenated derivatives as prostaglandins, thromboxanes, and leukotrienes are mediators. The leukotrienes are formed by transformation of arachidonic acid into an unstable epoxide intermediate, leukotriene A4, which can be converted enzymatically by hydration to leukotriene B4, and by addition of glutathione to leukotriene C4. This last compound is metabolized to leukotrienes D4 and E4 by successive elimination of a gamma-glutamyl residue and glycine. Slow-reacting substance of anaphylaxis consists of leukotrienes C4, D4, and E4. The cysteinyl-containing leukotrienes are potent bronchoconstrictors, increase vascular permeability in postcapillary venules, and stimulate mucus secretion. Leukotriene B4 causes adhesion and chemotactic movement of leukocytes and stimulates aggregation, enzyme release, and generation of superoxide in neutrophils. Leukotrienes C4, D4, and E4, which are released from the lung tissue of asthmatic subjects exposed to specific allergens, seem to play a pathophysiological role in immediate hypersensitivity reactions. These leukotrienes, as well as leukotriene B4, have pro-inflammatory effects.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Samuelsson, B -- New York, N.Y. -- Science. 1983 May 6;220(4597):568-75.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6301011" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Arachidonic Acids/metabolism/pharmacology/physiology ; Bronchi/drug effects ; Cats ; Chemical Phenomena ; Chemistry ; Cricetinae ; Guinea Pigs ; Haplorhini ; Humans ; Hypersensitivity, Immediate/*physiopathology ; Inflammation/*physiopathology ; Leukocytes/drug effects/metabolism ; Leukotriene B4/pharmacology/*physiology ; Mice ; Microcirculation/drug effects ; Rabbits ; Rats ; SRS-A/*physiology
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  • 8
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-01-20
    Description: Peptide synthesis can be used for elucidating the roles of secondary structures in the specificity of hormones, antigens, and toxins. Intermediate sized peptides with these activities assume amphiphilic secondary structures in the presence of membranes. When models are designed to optimize the amphiphilicity of the secondary structure, stronger interactions can be observed with the synthetic peptides than with the naturally occurring analogs.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kaiser, E T -- Kezdy, F J -- HL-18577/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1984 Jan 20;223(4633):249-55.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6322295" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Apolipoprotein A-I ; Apolipoproteins ; Binding Sites ; Calcitonin ; Chemical Phenomena ; Chemistry ; Corticotropin-Releasing Hormone ; Endorphins ; Glucagon ; Growth Hormone-Releasing Hormone ; *Hormones/pharmacology ; Lipoproteins, HDL ; Melitten ; Models, Structural ; *Peptides/chemical synthesis/metabolism/pharmacology ; Protein Conformation ; Structure-Activity Relationship ; beta-Endorphin
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  • 9
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-10-19
    Description: Fourier transform mass spectrometry will play an important role in the future because of its unique combination of high mass resolution, high upper mass limit, and multichannel advantage. These features have already found application in gas chromatography-mass spectrometry, multiphoton ionization, laser desorption, and secondary ion mass spectrometry. However, its most notable feature is the ability to store ions. This characteristic, when combined with the others, will allow expeditious study of the interaction of gas-phase ions with both photons (photodissociation) and neutral molecules, and the convenient application of this fundamental information for chemical analysis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gross, M L -- Rempel, D L -- 2-8423576/PHS HHS/ -- New York, N.Y. -- Science. 1984 Oct 19;226(4672):261-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6385250" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Fourier Analysis ; Ions ; Lasers ; *Mass Spectrometry/instrumentation/methods
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  • 10
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-08-31
    Description: High-resolution carbon-13 nuclear magnetic resonance (NMR) spectra of enzyme-inhibitor and enzyme-substrate complexes provide detailed structural and stereochemical information on the mechanism of enzyme action. The proteases trypsin and papain are shown to form tetrahedrally coordinated complexes and acyl derivatives with a variety of compounds artificially enriched at the site or sites of interest. These results are compared with the structural information derived from x-ray diffraction. Detailed NMR studies have provided a clearer picture of the ionization state of the residues participating in enzyme-catalyzed processes than other more classical techniques. The dynamics of enzymic catalysis can be observed at sub-zero temperatures by a combination of cryoenzymology and carbon-13 NMR spectroscopy. With these powerful techniques, transient, covalently bound intermediates in enzyme-catalyzed reactions can be detected and their structures rigorously assigned.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mackenzie, N E -- Malthouse, J P -- Scott, A I -- New York, N.Y. -- Science. 1984 Aug 31;225(4665):883-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6433481" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Carbon Isotopes ; Carboxypeptidases/metabolism ; Carboxypeptidases A ; Catalysis ; Chemical Phenomena ; Chemistry ; Coenzymes/*metabolism ; Endopeptidases/metabolism ; Enzymes/*metabolism ; Freezing ; Fructose-Bisphosphate Aldolase/metabolism ; Magnetic Resonance Spectroscopy ; Papain/metabolism ; Pepsin A/metabolism ; Peptide Hydrolases/*metabolism ; Protease Inhibitors ; Pterins/metabolism ; Pyridoxal Phosphate/metabolism ; Serine Endopeptidases
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  • 11
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-03-09
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Maugh, T H 2nd -- New York, N.Y. -- Science. 1984 Mar 9;223(4640):1051-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6695193" target="_blank"〉PubMed〈/a〉
    Keywords: *Air Pollutants ; *Atmosphere ; Carbon Tetrachloride ; Chemical Phenomena ; Chemistry ; *Chlorofluorocarbons, Methane ; Free Radicals ; Nitrogen Dioxide ; Nitrous Oxide ; Oxygen ; *Ozone ; Photochemistry ; Risk ; Singlet Oxygen ; Trichloroethanes ; Ultraviolet Rays
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  • 12
    Publication Date: 1984-10-19
    Description: Pyrolysis mass spectrometry in combination with computerized multivariate statistical analysis enables qualitative and quantitative analysis of nonvolatile organic materials containing molecular assemblies of a complexity and size far beyond the capabilities of direct mass spectrometry. The state of the art in pyrolysis mass spectrometry techniques is illustrated through specific applications, including structural determination and quality control of synthetic polymers, quantitative analysis of polymer mixtures, classification and structural characterization of fossil organic matter, and nonsupervised numerical extraction of component patterns from complex biological samples.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Meuzelaar, H L -- Windig, W -- Harper, A M -- Huff, S M -- McClennen, W H -- Richards, J M -- New York, N.Y. -- Science. 1984 Oct 19;226(4672):268-74.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6484572" target="_blank"〉PubMed〈/a〉
    Keywords: Biochemical Phenomena ; Biochemistry ; Chemical Phenomena ; Chemistry ; Coal ; Enterobacteriaceae/analysis/isolation & purification ; Hot Temperature ; Mass Spectrometry/*methods ; Polymers
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  • 13
    Publication Date: 1984-08-31
    Description: The splicing of messenger RNA precursors in vitro proceeds through an intermediate that has the 5' end of the intervening sequence joined to a site near the 3' splice site. This lariat structure, which has been characterized for an adenovirus 2 major late transcript, has a branch point, with 2'-5' and 3'-5' phosphodiester bonds emanating from a single adenosine residue. The excised intervening sequence retains the branch site and terminates in a guanosine residue with a 3' hydroxyl group. The phosphate group at the splice junction between the two exons originates from the 3' splice site at the precursor.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Padgett, R A -- Konarska, M M -- Grabowski, P J -- Hardy, S F -- Sharp, P A -- P01-CA14051/CA/NCI NIH HHS/ -- P01-CA26717/CA/NCI NIH HHS/ -- R01-GM32467/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1984 Aug 31;225(4665):898-903.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6206566" target="_blank"〉PubMed〈/a〉
    Keywords: Adenoviruses, Human/metabolism ; Base Sequence ; Chemical Phenomena ; Chemistry ; Nucleic Acid Conformation ; Nucleic Acid Precursors/analysis/*metabolism ; Oligoribonucleotides/metabolism ; Phosphates/metabolism ; RNA/analysis/*metabolism ; RNA Precursors ; *RNA Splicing ; RNA, Messenger/analysis/*metabolism ; RNA, Viral/analysis/*metabolism
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  • 14
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-05-11
    Description: The mechanism of lipid peroxidation and the manner in which antioxidants function is reviewed. beta-Carotene is a purported anticancer agent, which is believed by some to have antioxidant action of a radical-trapping type. However, definitive experimental support for such action has been lacking. New experiments in vitro show that beta-carotene belongs to a previously unknown class of biological antioxidants. Specifically, it exhibits good radical-trapping antioxidant behavior only at partial pressures of oxygen significantly less than 150 torr, the pressure of oxygen in normal air. Such low oxygen partial pressures are found in most tissues under physiological conditions. At higher oxygen pressures, beta-carotene loses its antioxidant activity and shows an autocatalytic, prooxidant effect, particularly at relatively high concentrations. Similar oxygen-pressure-dependent behavior may be shown by other compounds containing many conjugated double bonds.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Burton, G W -- Ingold, K U -- New York, N.Y. -- Science. 1984 May 11;224(4649):569-73.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6710156" target="_blank"〉PubMed〈/a〉
    Keywords: Antioxidants/*metabolism ; Carotenoids/*metabolism ; Chemical Phenomena ; Chemistry ; Free Radicals ; Humans ; Linoleic Acids/metabolism ; *Lipid Metabolism ; Oxidation-Reduction ; Oxygen/metabolism ; Partial Pressure ; Peroxides/metabolism ; Tetrahydronaphthalenes/metabolism ; beta Carotene
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  • 15
    Publication Date: 1983-12-16
    Description: Aplysiatoxin and debromoaplysiatoxin, which are isolated from the seaweed, Lyngbya gracilis, differ in their chemical structure only by the presence or absence of a bromine residue in the hydrophilic region. The function and the structure-activity relation of the hydrophilic region are not known. Aplysiatoxin increased malignant transformation, stimulated DNA synthesis, and inhibited the binding of phorbol-12,13-dibutyrate and epidermal growth factor to cell receptors. Debromoaplysiatoxin inhibited the binding of these two substances as strongly as aplysiatoxin but did not increase malignant transformation or stimulate DNA synthesis. These results indicate that a slight change in the chemical structure of the hydrophilic region of aplysiatoxin affects its abilities to increase cell transformation and stimulate DNA synthesis and that the abilities of the tumor promoters to inhibit the binding of phorbol-12,13-dibutyrate and epidermal growth factor are dissociable from their abilities to increase cell transformation and stimulate DNA synthesis under some circumstances.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Shimomura, K -- Mullinix, M G -- Kakunaga, T -- Fujiki, H -- Sugimura, T -- New York, N.Y. -- Science. 1983 Dec 16;222(4629):1242-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6316505" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Caenorhabditis elegans Proteins ; Carcinogens/*pharmacology ; Carrier Proteins ; Cell Line ; Cell Transformation, Neoplastic/*drug effects ; Chemical Phenomena ; Chemistry ; DNA/biosynthesis ; Epidermal Growth Factor/metabolism ; Lactones/analysis/*pharmacology ; *Lyngbya Toxins ; Mice ; Phorbol 12,13-Dibutyrate ; Phorbol Esters/metabolism ; *Protein Kinase C ; Receptor, Epidermal Growth Factor ; Receptors, Cell Surface/metabolism ; *Receptors, Drug ; Structure-Activity Relationship
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  • 16
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-03-16
    Description: Yeast phenylalanine transfer RNA was subjected to a 12-picosecond molecular dynamics simulation. The principal features of the x-ray crystallographic analysis are reproduced, and the amplitudes of atomic displacements appear to be determined by the degree of exposure of the atoms. An analysis of the hydrogen bonds shows a correlation between the average length of a bond and the fluctuation in that length and reveals a rocking motion of bases in Watson-Crick guanine X cytosine base pairs. The in-plane motions of the bases are generally of larger amplitude than the out-of-plane motions, and there are correlations in the motions of adjacent bases.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Harvey, S C -- Prabhakaran, M -- Mao, B -- McCammon, J A -- New York, N.Y. -- Science. 1984 Mar 16;223(4641):1189-91.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6560785" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Computers ; Cytosine ; Guanine ; Hydrogen Bonding ; Nucleic Acid Conformation ; *RNA, Fungal ; *RNA, Transfer, Amino Acyl ; Yeasts/analysis
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  • 17
    Publication Date: 1984-11-16
    Description: Sequence-dependent variations in DNA revealed by x-ray crystallographic studies have suggested that certain DNA-reactive drugs may react preferentially with defined sequences in DNA. Drugs that wind around the helix and reside within one of the grooves of DNA have perhaps the greatest chance of recognizing sequence-dependent features of DNA. The antitumor antibiotic CC-1065 covalently binds through N-3 of adenine and resides within the minor groove of DNA. This drug overlaps with five base pairs for which a high sequence specificity exists.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hurley, L H -- Reynolds, V L -- Swenson, D H -- Petzold, G L -- Scahill, T A -- New York, N.Y. -- Science. 1984 Nov 16;226(4676):843-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6494915" target="_blank"〉PubMed〈/a〉
    Keywords: Antibiotics, Antineoplastic/*metabolism ; *Base Sequence ; Binding Sites ; Chemical Phenomena ; Chemistry ; DNA/*metabolism ; *Indoles ; Leucomycins/*metabolism ; Molecular Conformation ; X-Ray Diffraction
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  • 18
    Publication Date: 1984-06-15
    Description: A new class of synthetic antifungal agents, the allylamines , has been developed by modification of naftifine , a topical antimycotic. SF 86-327, the most effective of these compounds so far, is highly active in vitro against a wide range of fungi and exceeds clinical standards in the oral and topical treatment of guinea pig dermatophytoses. SF 86-327 is a powerful specific inhibitor of fungal squalene epoxidase, a key enzyme in sterol biosynthesis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Petranyi, G -- Ryder, N S -- Stutz, A -- New York, N.Y. -- Science. 1984 Jun 15;224(4654):1239-41.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6547247" target="_blank"〉PubMed〈/a〉
    Keywords: Allylamine/analogs & derivatives/*chemical synthesis/pharmacology ; Amines/*chemical synthesis ; Animals ; Antifungal Agents/*chemical synthesis/pharmacology ; Chemical Phenomena ; Chemistry ; Dermatomycoses/drug therapy ; Fungi/*drug effects/enzymology ; Guinea Pigs ; Naphthalenes/chemical synthesis/pharmacology ; Oxygenases/*antagonists & inhibitors ; Squalene Monooxygenase
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  • 19
    Publication Date: 1984-11-02
    Description: By recombinant DNA techniques, a disulfide bond was introduced at a specific site in T4 lysozyme, a disulfide-free enzyme. This derivative retained full enzymatic activity and was more stable toward thermal inactivation than the wild-type protein. The derivative, T4 lysozyme (Ile3----Cys), was prepared by substituting a Cys codon for an Ile codon at position 3 in the cloned lysozyme gene by means of oligonucleotide-dependent, site-directed mutagenesis. The new gene was expressed in Escherichia coli under control of the (trp-lac) hybrid tac promoter, and the protein was purified. Mild oxidation generated a disulfide bond between the new Cys3 and Cys97, one of the two unpaired cysteines of the native molecule. Oxidized T4 lysozyme (Ile3----Cys) exhibited specific activity identical to that of the wild-type enzyme when measured at 20 degrees C in a cell-clearing assay. The cross-linked protein was more stable than the wild type during incubation at elevated temperatures as determined by recovered enzymatic activity at 20 degrees C.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Perry, L J -- Wetzel, R -- New York, N.Y. -- Science. 1984 Nov 2;226(4674):555-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6387910" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; DNA, Recombinant/metabolism ; Escherichia coli/enzymology ; *Genetic Engineering ; Kinetics ; Muramidase/*genetics/metabolism ; Protein Denaturation
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  • 20
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1983-09-09
    Description: The structures of three proteins that regulate gene expression have been determined recently and suggest how these proteins may bind to their specific recognition sites on the DNA. One protein (Cro) is a repressor of gene expression, the second (CAP) usually stimulates gene expression, and the third (lambda repressor) can act as either a repressor or an activator. The three proteins contain a substructure consisting of two consecutive alpha helices that is virtually identical in each case. Structural and amino acid sequence comparisons suggest that this bihelical fold occurs in a number of proteins that regulate gene expression, and is an intrinsic part of the DNA-protein recognition event. The modes of repression and activation by Cro and lambda repressor are understood reasonably well, but the mode of action of CAP is still unclear.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Takeda, Y -- Ohlendorf, D H -- Anderson, W F -- Matthews, B W -- GM20066/GM/NIGMS NIH HHS/ -- GM28138/GM/NIGMS NIH HHS/ -- GM30894/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1983 Sep 9;221(4615):1020-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6308768" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Chemical Phenomena ; Chemistry ; *DNA Helicases ; DNA-Binding Proteins ; Escherichia coli/genetics ; Gene Expression Regulation ; Models, Chemical ; Protein Conformation
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  • 21
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-06-08
    Description: The effect of a partial pressure of nitrogen of 50 atmospheres (5065 kilopascals ) on the hydrogen evolution reaction of nitrogenase has been investigated. Evolution of hydrogen was not blocked completely by 50 atmospheres of nitrogen in any of four experiments; rather, 27.3 +/- 2.4 percent of the total electron flux through nitrogenase was directed toward production of hydrogen. The ratio of hydrogen evolved to nitrogen fixed was close to 1:1, which implies that hydrogen evolution is obligatory in the fixation of molecular nitrogen by nitrogenase.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Simpson, F B -- Burris, R H -- AI-00848/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1984 Jun 8;224(4653):1095-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6585956" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Hydrogen ; *Nitrogen ; Nitrogen Fixation ; *Nitrogenase ; Partial Pressure
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  • 22
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1978-03-17
    Description: The history of U.S. foreign aid support of science and technology in Latin America is examined and an attempt is made to evaluate the scientific and economic growth of that area in relation to the total foreign aid effort.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Szmant, H H -- New York, N.Y. -- Science. 1978 Mar 17;199(4334):1173-82.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/415363" target="_blank"〉PubMed〈/a〉
    Keywords: Chemistry ; Cost-Benefit Analysis ; Education ; History, 20th Century ; International Educational Exchange ; Latin America ; *Research Support as Topic ; *Science/history ; United States
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  • 23
    Publication Date: 1980-01-04
    Description: In concentrates of water produced in a laboratory simulation of a drinking water treatment process, direct-acting, nonvolatile mutagens were readily detected by means of the Ames Salmonella test. The mutagens were shown to be produced by the chlorination process. Treatment of the water with chloramine resulted in less mutagenic activity than treatment with free chlorine. Dechlorination of drinking water with sulfite sharply reduced the mutagenic activity. Treatment with sulfur dioxide is proposed as an effective, inexpensive method of reducing the direct-acting mutagenic activity of drinking water and of aqueous industrial effluents.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cheh, A M -- Skochdopole, J -- Koski, P -- Cole, L -- New York, N.Y. -- Science. 1980 Jan 4;207(4426):90-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6985746" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Chloramines ; Chlorine ; Mutagens/*analysis ; Salmonella typhimurium/genetics ; Sulfites ; Water Pollutants/*analysis ; Water Pollutants, Chemical/*analysis ; Water Supply/*analysis
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  • 24
    Publication Date: 1981-10-16
    Description: The DNA/RNA Synthesizer provides a complete and automated procedure for the synthesis of DNA sequences. Each base unit is added in a 30-minute cycle, permitting a tetradecamer to be constructed in 6 1/2 hours. The complete procedure is described, including a practical procedure for isolation and purification of the desired DNA sequence.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Alvarado-Urbina, G -- Sathe, G M -- Liu, W C -- Gillen, M F -- Duck, P D -- Bender, R -- Ogilvie, K K -- New York, N.Y. -- Science. 1981 Oct 16;214(4518):270-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6169150" target="_blank"〉PubMed〈/a〉
    Keywords: Automation ; Chemical Phenomena ; Chemistry ; DNA/*chemical synthesis ; *Genes, Synthetic ; RNA/*chemical synthesis ; Solubility
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  • 25
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-05-15
    Description: Research on chitin as a marine resource is pointing to novel applications for this cellulose-like biopolymer. Discovery of nondegrading solvent systems has permitted the spinning of filaments, for example, for use as surgical sutures. New methods for preparing the bioactive alkyl glycoside of N-acetyl-D-glucosamine (the monomer unit of chitin) and a microcrystalline chitin has encouraged their use as promoters for growth of bifidobacteria and as an aid in digestion of high-lactose cheese whey by domestic animals. Chitin-protein complexes of several crustacean species show great variability in ratios of chitin to covalently bound protein and in residual protein in the "purified" chitins.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Austin, P R -- Brine, C J -- Castle, J E -- Zikakis, J P -- New York, N.Y. -- Science. 1981 May 15;212(4496):749-53.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7221561" target="_blank"〉PubMed〈/a〉
    Keywords: Animal Feed ; Animals ; Cheese ; Chemical Phenomena ; Chemistry ; Chickens ; *Chitin ; Crystallography ; Lactose/metabolism ; Proteins/analysis ; Sutures ; *Technology
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  • 26
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-12-18
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gilbert, W -- New York, N.Y. -- Science. 1981 Dec 18;214(4527):1305-12.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7313687" target="_blank"〉PubMed〈/a〉
    Keywords: Base Sequence ; Chemical Phenomena ; Chemistry ; DNA/*genetics ; Eukaryotic Cells/physiology ; *Genes ; Hydrazines ; Lac Operon ; Methylation ; Prokaryotic Cells/physiology ; Sulfuric Acid Esters
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  • 27
    Publication Date: 1982-07-09
    Description: A new process has been developed which is called "Boradeption" to signify boronic acid--dependent phase transfer of water-insoluble agents. Highly fluorescent boronic acid dervatives, FluoroBoras, are solubilized with a physiologically compatible carrier buffer containing a receptor group for boronate adduct formation. The system can be used to stain living cells. In another variation of the Boradeption concept, an insoluble reporter molecule containing a boronate receptor is solubilized with a carrier buffer containing a boronic acid functional group. The boronate-receptor complexes, which are in dynamic equilibrium, can be designed as vital stains and reagents for a variety of biological and medical applications.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gallop, P M -- Paz, M A -- Henson, E -- AG-00376-07/AG/NIA NIH HHS/ -- HL-20764-04A1/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1982 Jul 9;217(4555):166-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6178158" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Biological Transport ; *Boron Compounds/therapeutic use ; *Boronic Acids/therapeutic use ; *Cell Membrane Permeability ; Cells, Cultured ; Chemical Phenomena ; Chemistry ; Chromogenic Compounds/metabolism ; Cricetinae ; Fibroblasts ; Fluorescent Dyes/metabolism ; Humans ; Rats ; Staining and Labeling
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  • 28
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-12-11
    Description: The scrapie agent causes a degenerative nervous system disease in sheep and goats. Studies with extensively purified preparations demonstrated that the agent contains a protein that is required for infectivity. Chemical modification of the scrapie agent by diethyl pyrocarbonate reduced the titer 1000-fold. Exposure of the inactivated agent to hydroxylamine, a strong nucleophile, resulted in complete restoration of infectivity. Presumably, nucleophilic residues within a scrapie agent protein undergo carbethoxylation on reaction with diethyl pyrocarbonate, and subsequent addition of hydroxylamine displaces these carbethoxy groups.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McKinley, M P -- Masiarz, F R -- Prusiner, S B -- NS14069/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1981 Dec 11;214(4526):1259-61.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6795721" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biological Assay ; Brain/microbiology ; Chemical Phenomena ; Chemistry ; Cricetinae ; Diethyl Pyrocarbonate/pharmacology ; Histidine/pharmacology ; *Prions ; Ribonucleases/pharmacology ; Serum Albumin, Bovine/pharmacology ; Viral Proteins/*isolation & purification/pharmacology
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  • 29
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-01-30
    Description: The incubation of lens proteins with reducing sugars leads to the formation of fluorescent yellow pigments and cross-like similar to those reported in aging and cataractous human lenses. Called nonenzymatic browning or the Maillard reaction, this aging process also occurs in stored foods. Reducing sugars condense with the free amino group of proteins, then rearrange and dehydrate to form unsaturated pigments and cross-linked products. Although most proteins in living systems turn over with sufficient rapidity to avoid nonenzymatic browning, some, such as lens crystallins and skin collagen, are exceptionally long-lived and may be vulnerable.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Monnier, V M -- Cerami, A -- AM 19655/AM/NIADDK NIH HHS/ -- New York, N.Y. -- Science. 1981 Jan 30;211(4481):491-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6779377" target="_blank"〉PubMed〈/a〉
    Keywords: *Aging ; Animals ; Cattle ; Chemical Phenomena ; Chemistry ; *Crystallins ; Diabetes Mellitus/physiopathology ; Glucose ; Glucosephosphates ; In Vitro Techniques ; Lysine ; *Proteins ; Spectrophotometry, Ultraviolet
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  • 30
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-03-13
    Description: Great advances have been made in fundamental scientific research in recent years. The new knowledge gathered, in addition to deepening our understanding of the physical universe, contributes a range of abilities and opportunities to society that would not otherwise be available. Much research that may be called applied because it addresses needs of society is quite fundamental in character, and support of such research at the National Science Foundation is to be handled in tandem by the research directorates. Other areas that require a refocusing of support are engineering science and education, at all levels, in science and engineering. Increasing our strength in these areas is essential to achieve our national economic, social, and political goals. Steps are being taken by the National Science Foundation to make its structure better able to deal with engineering and applied research and to provide greater mutual reinforcement between applied and basic research.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Slaughter, J B -- New York, N.Y. -- Science. 1981 Mar 13;211(4487):1131-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7466384" target="_blank"〉PubMed〈/a〉
    Keywords: Cell Biology ; Chemical Phenomena ; Chemistry ; *Forecasting ; Geological Phenomena ; Geology ; *Government Agencies ; Molecular Biology ; Neurochemistry ; Physical Phenomena ; Physics ; Research Support as Topic ; United States
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  • 31
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1982-12-10
    Description: The discovery that cis-diamminedichloroplatinum(II) (cis-DDP) has clinically useful antitumor properties and can form platinum blues spawned an extensive investigation of its chemistry in water. Several new molecules have been synthesized, some rather old ones have been characterized for the first time, and clues have begun to emerge about the chemical interaction of cis-DDP with its likely biological target, DNA.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lippard, S J -- New York, N.Y. -- Science. 1982 Dec 10;218(4577):1075-82.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6890712" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Cisplatin ; *Dna ; Hydrolysis ; Pigments, Biological
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  • 32
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1982-12-03
    Description: The visual response is initiated by light reception and transduction into chemical and electrical energy in the outer-segment membranes of rod and cone cells. Recent research on the molecular events controlled by light has clarified the roles of some of the rod outer-segment biomolecules. These developments and the current unresolved questions are described.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉O'Brien, D F -- New York, N.Y. -- Science. 1982 Dec 3;218(4576):961-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6291153" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Blood Proteins/metabolism ; Calcium/metabolism ; Chemical Phenomena ; Chemistry ; Enzyme Activation ; Enzymes/metabolism ; GTP-Binding Proteins ; Light ; Membranes/metabolism ; Models, Biological ; Phosphoric Diester Hydrolases/biosynthesis ; Photoreceptor Cells/*metabolism ; Receptors, Cell Surface/metabolism ; Rhodopsin/metabolism ; Rod Cell Outer Segment/*metabolism ; Vision, Ocular/*physiology
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  • 33
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1983-06-10
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Krenitsky, T A -- Beauchamp, L -- New York, N.Y. -- Science. 1983 Jun 10;220(4602):1106.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6857236" target="_blank"〉PubMed〈/a〉
    Keywords: Acyclovir/metabolism ; *Antiviral Agents/metabolism ; Chemical Phenomena ; Chemistry ; Humans ; Vidarabine/metabolism
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  • 34
    Publication Date: 1983-05-06
    Description: Resonance Raman spectra of photolyzed carbonmonoxyhemoglobin obtained with 10-nanosecond pulses are compared with the spectra of photolyzed carbonmonoxyhemoglobin stabilized at 80 K. In comparing the deoxy with the photodissociated species, the changes in the Raman spectra are the same for these two experimental regimes. These results show that at ambient and cryogenic temperatures the heme pocket in liganded hemoglobin is significantly different from that of deoxyhemoglobin. It is concluded that measurements of the properties of intermediate species from photodissociated hemoglobin stabilized at low temperatures can be used to probe the short-lived metastable forms of hemoglobin present after photodissociation under biologically relevant solution conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ondrias, M R -- Friedman, J M -- Rousseau, D L -- New York, N.Y. -- Science. 1983 May 6;220(4597):615-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6836305" target="_blank"〉PubMed〈/a〉
    Keywords: Carboxyhemoglobin ; Chemical Phenomena ; Chemistry ; Freezing ; *Hemoglobins ; Humans ; Ligands ; Spectrum Analysis, Raman ; Temperature
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  • 35
    Publication Date: 1983-04-15
    Description: Alkylating agents that display strong selectivity for opiate receptor types delta or mu were prepared by appropriate modification of the structures of the strong analgesics fentanyl, etonitazene, and endoethenotetrahydrooripavine. The availability of these substances should facilitate studies of the structural basis of receptor specificity and of the physiologic roles of these receptors.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rice, K C -- Jacobson, A E -- Burke, T R Jr -- Bajwa, B S -- Streaty, R A -- Klee, W A -- New York, N.Y. -- Science. 1983 Apr 15;220(4594):314-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6132444" target="_blank"〉PubMed〈/a〉
    Keywords: Alkylation ; Animals ; Benzimidazoles/analogs & derivatives/metabolism ; Brain/physiology ; Cells, Cultured ; Chemical Phenomena ; Chemistry ; Enkephalin, Methionine/analogs & derivatives/metabolism ; Fentanyl/analogs & derivatives/metabolism ; *Isothiocyanates ; Ligands ; Rats ; Receptors, Opioid/*metabolism/physiology ; Thebaine/analogs & derivatives/pharmacology
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  • 36
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1978-04-07
    Description: Glucose reacts nonenzymatically with the NH2-terminal amino acid of the beta chain of human hemoglobin by way of a ketoamine linkage, resulting in the formation of hemoglobin AIc. Other minor components appear to be adducts of glucose 6-phosphate and fructose 1,6-diphosphate. These hemoglobins are formed slowly and continuously throughout the 120-day life-span of the red cell. There is a two- to threefold increase in hemoglobin AIc in the red cells of patients with diabetes mellitus. By providing an integrated measurement of blood glucose, hemoglobin AIc is useful in assessing the degree of diabetic control. Furthermore, this hemoglobin is a useful model of nonenzymatic glycosylation of other proteins that may be involved in the long-term complications of the disease.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bunn, H F -- Gabbay, K H -- Gallop, P M -- New York, N.Y. -- Science. 1978 Apr 7;200(4337):21-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/635569" target="_blank"〉PubMed〈/a〉
    Keywords: Blood Glucose/metabolism ; Chemical Phenomena ; Chemistry ; Diabetes Complications ; Diabetes Mellitus/*blood/diagnosis ; Diphosphoglyceric Acids/blood ; Glycosides/blood ; Glycosuria/etiology ; Hemoglobin A/*metabolism ; Hemoglobins/*analysis/*metabolism ; Humans ; Kinetics ; Oxygen/blood ; Structure-Activity Relationship
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  • 37
    Publication Date: 1979-06-08
    Description: It has been proposed that nitrilotriacetic acid be substituted for trisodium polyphosphates in detergents as a way to reduce the rate of eutrophication in the Great Lake Basin. The reaction of nitrilotriacetic acid with chlorine-containing solutions produces a hitherto unknown degradation production, N-formyliminodiacetic acid, in high yield. The toxicological and environmental implications of this reaction are unclear.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Spanggord, R J -- Tyson, C A -- New York, N.Y. -- Science. 1979 Jun 8;204(4397):1081-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/36659" target="_blank"〉PubMed〈/a〉
    Keywords: *Acetates ; Chemical Phenomena ; Chemistry ; *Chlorine ; Dicarboxylic Acids ; Environmental Pollutants ; Hydrogen-Ion Concentration ; *Imino Acids ; Mutagens ; *Nitrilotriacetic Acid
    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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  • 38
    facet.materialart.
    Unknown
    American Association for the Advancement of Science (AAAS)
    Publication Date: 1979-03-16
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ferris, J P -- New York, N.Y. -- Science. 1979 Mar 16;203(4385):1135-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/218287" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Hydrogen Cyanide ; *Peptides
    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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  • 39
    Publication Date: 1980-10-01
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bumb, R R -- Crummett, W B -- Cutie, S S -- Gledhill, J R -- Hummel, R H -- Kagel, R O -- Lamparski, L L -- Luoma, E V -- Miller, D L -- Nestrick, T J -- Shadoff, L A -- Stehl, R H -- Woods, J S -- New York, N.Y. -- Science. 1980 Oct;210(4468):385-90.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6159682" target="_blank"〉PubMed〈/a〉
    Keywords: Air Pollutants/analysis ; Chemical Phenomena ; Chemistry ; Chromatography, High Pressure Liquid ; *Dioxins/analysis ; *Fires ; Power Plants ; Smoke/analysis ; Soil Pollutants/analysis ; Tetrachlorodibenzodioxin/analysis ; Vehicle Emissions/analysis ; Water Pollutants, Chemical/analysis
    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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  • 40
    Publication Date: 1984-05-25
    Description: Polypeptide analogs of the known members of the corticotropin-releasing factor (CRF) family were synthesized and tested in vitro and in vivo for enhanced potency or competitive antagonism. Predictive methods and physicochemical measurements had suggested an internal secondary alpha-helical conformation spanning about 25 residues for at least three members of the CRF family. Maximization of alpha-helix-forming potential by amino acid substitutions from the native known sequences (rat/human and ovine CRF, sauvagine, and carp and sucker urotensin 1) led to the synthesis of an analog that was found to be more than twice as potent as either of the parent peptides in vitro. In contrast, certain amino-terminally shortened fragments, such as alpha-helical CRF or ovine CRF residues 8 to 41, 9 to 41, and 10 to 41, were found to be competitive inhibitors in vitro. Selected antagonists were examined and also found to be active in vivo.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rivier, J -- Rivier, C -- Vale, W -- AA03504/AA/NIAAA NIH HHS/ -- AM20917/AM/NIADDK NIH HHS/ -- AM26741/AM/NIADDK NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1984 May 25;224(4651):889-91.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6326264" target="_blank"〉PubMed〈/a〉
    Keywords: Adrenocorticotropic Hormone/secretion ; Animals ; Binding, Competitive ; Chemical Phenomena ; Chemistry ; Corticotropin-Releasing Hormone/*antagonists & inhibitors ; Rats
    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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  • 41
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    In:  Other Sources
    Publication Date: 2011-08-24
    Description: Estimates of the mass of dust suspended in the Martian atmosphere are derived from global and regional 9-micrometer opacity maps produced from Viking Infrared Thermal Mapper data. During the peak of the 1977b storm, a total dust mass of approximately 4.3 x 10(exp 14) g was suspended, equivalent to 4.3 x 10(exp -4) g/sq cm, or a layer 1.4 micrometers thick. During a local dust storm near Solis Planum at L(sub s) 227 deg, approximately 1.3 x 10(exp 13) g of dust were lofted, equal to about a 6-micrometer layer in that vicinity.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; E4; p. 7509-7512
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  • 42
    Publication Date: 2011-08-24
    Description: We model an infrared outburst on Io as being due to a large, erupting lava flow which increased its area at a rate of 1.5 x 10(exp 5)/sq m and cooled from 1225 to 555 K over the 2.583-hr period of observation. The inferred effusion rate of 3 x 10(exp 5) cu m/sec for this eruption is very high, but is not unprece- dented on the Earth and is similar to the high eruption rates suggested for early lunar volcanism. Eruptions occur approxi- mately 6% of the time on Io. These eruptions provide ample resurfacing to explain Io's lack of impact craters. We suggest that the large total radiometric heat flow, 10(exp 14) W, and the size and temperature distribution of the thermal anomalies (McEwen et al. 1992; Veeder et al. 1994) can be accounted for by a series of silicate lava flows in various stages of cooling. We propose that the whole suite of Io's currently observed thermal anomalies was produced by multiple, high-eruptive-rate silicate flows within the past century.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 113; 1; p. 220-225
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  • 43
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    In:  Other Sources
    Publication Date: 2011-08-24
    Description: We investigate the orbital dynamics of small dust particles generated via the continuous micrometeoroid bombardment of the Martian moons. In addition to Mar's oblateness, we also consider the radiation pressure perturbation that is complicated by the planet's eccentric orbit and tilted rotational axis. Considering the production rates and the lifetimes of dust grains, we show that particles from Deimos with radii of about 15 micrometers are expected to dominate the population of a permanently present and tilted dust torus. This torus has an estimated peak number density of approximately equals 5 x 10(exp -12)/cu cm and an optical depth of approximately equals 4 x 10(exp -8).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; E2; p. 3277-3284
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  • 44
    Publication Date: 2011-08-24
    Description: The valley network channels on the heavily cratered ancient surface of Mars suggest the presence of liquid water approximately 3.8 Gyr ago. However, the implied warm climate is difficult to explain in the context of the standard solar model, even allowing for the maximum CO2 greenhouse heating. In this paper we investigate the astronomical and planetary implications of a nonstandard solar model in which the zero-age, main-sequence Sun had a mass of 1.05 +/- 0.02 Solar Mass. The excess mass was subsequently lost in a solar wind during the first 1.2(-0.2, +0.4) Gyr of the Sun's main sequence phase. The implied mass-loss rate of 4(+3, -2) x 10(exp -11) M/yr, or about 10(exp 3) x that of the current Sun, may be detectable in several nearby young solar type stars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); p. 5457-5464
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  • 45
    Publication Date: 2011-08-24
    Description: Hellas basin on Mars has been the site of volcanism, tectonism, and modification by fluvial, mass-wasting, and eolian processes over its more than 4-b.y. existence. Our detailed geologic mapping and related studies have resulted in the following new interpretations. The asymmetric distribution of highland massifs and other structures that define the uplifted basin rim suggest a formation of the basin by the impact of a low-angle bolide having a trajectory heading S60E. During the Late Noachian, the basin was infilled, perhaps by lava flows, that were sufficiently thick (greater than 1 km) to produce wrinkle ridges on the fill material and extensional faulting along the west rim of the basin. At about the same time, deposits buried northern Malea Planum, which are interpreted to be pyroclastic flows from Amphitrites and Peneus Paterae on the basis of their degraded morphology, topology, and the application of a previous model for pyroclastic volcanism on Mars. Peneus forms a distinctive caldera structure that indicates eruption of massive volumes of magma, whereas Amphitrites is a less distinct circular feature surrounded by a broad, low, dissected shield that suggests generally smaller volume eruptions. During the Early Hesperian, an approximately 1-to 2km-thick sequence of primarily fined-grained, eolian material was deposited on the floor of Hellas basin. Subsequently, the deposit was deeply eroded, except where armored by crater ejecta, and it retreated as much as 200-300 km along its western margin, leaving behind pedestal craters and knobby outliers of the deposit. Local debris flows within the deposit attest to concentrations of groundwater, perhaps in part brought in by outflow floods along the east rim of the basin. These floods may have deposited approximately 100-200m of sediment, subduing wrinkle ridges in the eastern part of the basin floor. During the Late Hesperian and Amazonian, eolian mantles were emplaced on the basin rim and floor and surrounding highlands. Their subsequent erosion resulted in pitted and etched plains and crater fill, irregular mesas, and pedestal craters. Local evidence occurs for the possible former presence of ground ice or ice sheets approximately 100 km across; however, we disagree with a hypothesis that suggest that the entire south rim and much of the floor of Hellas have been glaciated. Orientations of dune fields and yardangs in lower parts of Hellas basin follow directions of the strongest winds predicted by a recently published general circulation model (GCM). Transient frost and dust splotches in the region are, by contrast, related to the GCM prediction for the season in which the images they appear in were taken.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); p. 5407-5432
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  • 46
    Publication Date: 2011-08-24
    Description: Visible and near-IR refectivity, Moessbauer, and X ray diffraction data were obtained on powders of impact melt rock from the Manicouagan Impact Crater located in Quebec, Canada. The iron mineralogy is dominated by pyroxene for the least oxidized samples and by hematite for the most oxidized samples. Phyllosilicate (smectite) contents up to approximately 15 wt % were found in some heavily oxidized samples. Nanophase hematite and/or paramagnetic ferric iron is observed in all samples. No hydrous ferric oxides (e.g., goethite, lepidocrocite, and ferrihydrite) were detected, which implies the alteration occurred above 250 C. Oxidative alteration is thought to have occurred predominantly during late-stage crystallization and subsolidus cooling of the impact melt by invasion of oxidizing vapors and/or solutions while the impact melt rocks were still hot. The near-IR band minimum correlated with the extent of aleration Fe(3+)/Fe(sub tot) and ranged from approximately 1000 nm (high-Ca pyroxene) to approximately 850 nm (bulk, well-crystalline hematite) for least and most oxidized samples, respectively. Intermediate band positions (900-920 nm) are attributed to low-Ca pyroxene and/or a composite band from hematite-pyroxene assemblages. Manicouagan data are consistent with previous assignments of hematite and pyroxene to the approximately 850 and approximately 1000nm bands observed in Martian reflectivity spectra. Manicouagan data also show that possible assignments for intermediate band positions (900-920 nm) in Martian spectra are pyroxene and/or hematite-pyroxene assemblages. By analogy with impact melt sheets and in agreement with observables for Mars, oxidative alteration of Martian impact melt sheets above 250 C and subsequent erosion could produce rocks and soils with variable proportions of hematite (both bulk and nanophase), pyroxene, and phyllosilicates as iron-bearing mineralogies. If this process is dominant, these phases on Mars were formed rapidly at relativly high temperatures on a sporadic basis throughout the history of the planet. The Manicouagan samples also show that this mineralogical diversity can be accomplished at constant chemical composition, which is also indicated for Mars from the analyses of soil at the two Viking landing sites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); pp. 5319-5328
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  • 47
    Publication Date: 2011-08-24
    Description: The discovery of concentrations of meteorites in Antarctica by Japanese field parties in 1969, and subsequently by joint U.S.-Japanese and U.S. field parties since 1976 has provided a significant new resource for understanding the origin and evolution of the solar system. The number of meteorites as well as the variety of meteorites has increased dramatically, and substantial amounts of data derived from their study has begun to appear in the scientific literature. The U.S. program of investigation has drawn on curatorial experience derived from the lunar program to: (1) develop specific collection and preliminary examination protocols; (2) provide documented samples for scientific investigations in response to specific requests; and (3) coordinate research by scientific consortia. The productivity of scientific research is significantly enhanced by these management approaches. Some of the results of the curatorial program for Antarctic meteorites carried out over the past three years are described.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: National Institute of Polar Research, Memoirs (ISSN 0386-0744); 20, D
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  • 48
    Publication Date: 2011-08-24
    Description: Two unique meteorites were identified by means of a mineralogical examination of the smaller-sized Yamato achondrites. Yamato-74130 is the most iron-rich ureilite with Na, Cr-rich augite instead of pigeonite. Yamato-74160 was extensively recrystallized, but the composition and proportion of olivine, orthopyroxene, augite, and plagioclase is consistent with LL7 chondrites. ALHA77005 is a unique achondrite with olivine, possibly three pyroxene assemblages, and maskelynite. These meteorites provide evidence that there may be other 'thermalized' asteroids than the howardite parent body. Detailed petrologic descriptions of the unique achondrites, recrystallized diogenite Yamato-74013, and the rapidly cooled eucrite Yamato-74450 with pyroxene phenocrysts are given. It is inferred from the bulk chemistry and the mineralogical reexamination of Yamato-75028 that it is composed of the H5-type clasts and chondrule-rich H(L)3-like matrix with the H5 fragments. A close relationship in the collisional evolution of some asteroids with these materials is inferred.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: National Institute of Polar Research, Memoirs (ISSN 0386-0744); 15, 1; 54-76
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  • 49
    Publication Date: 2005-02-24
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Res. in the Space Sci., Vol. 2, No. 1; 3 p
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  • 50
    Publication Date: 2009-11-23
    Description: Opinions conflict over the role of surface gravity in shaping impact craters on Mercury. One view holds that the effects of g are evident in measurable aspects of crater form; other investigators find little or no evidence for g's geomorphic importance. Ambiguity in the role of g and other variables in cratering on Mercury stems largely from uncertainty in identifying major geomorphic contrasts and the crater sizes at which they occur. One of these, depth/diameter (d/D), undergoes a major change at the transition from simple (bowl shaped) to complex (peaks and terraces) crater interiors. Four least-squares d/D fits for fresh craters on Mercury were attemped. The results are inconsistent. The d/D data that should resolve previous shortcomings is presented. The revised d/D distributions for simple and complex craters, which intersect at a diameter of about 5 km, support the initial thesis that g substantially influences the form of Mercury's craters.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geol. Program, 1983; p 104-106
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  • 51
    facet.materialart.
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    In:  CASI
    Publication Date: 2006-06-26
    Description: The high closing speed of 57km/s between the spacecraft and Halley poses special problems in the design of the required meteoroid protection. A double wall structure with a total thickness equal to 0.1 to 1 times the diameter of the largest meteoroid encountered is sufficient to stop that meteoroid. However, the unusually high number of meteoroid impacts on the Halley probe will cause significant erosion of the outer wall so that failure of the second wall is more likely to occur from a small meteoroid passing through a previously created hole in the outer wall and then penetrating the second wall. Calculations of the shielding required based on this failure mode, show that a double wall structure must actually have a total thickness 1.2 to 7.3 times the diameter of the largest meteoroid encountered, depending on the size distribution of the meteoroids.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: ESA Comet Halley Micrometeoroid Hazard Workshop; p 73-76
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  • 52
    Publication Date: 2006-04-06
    Description: Craters within the Ganymede Jg-7 quadrangle were divided into seven mappable units. The units represent: (1) irregular or elongate craters, (2) craters with dark ejecta, (3) palimpsests, (4) secondary craters, (5) and craters of young, mature, and old age. Symbols used for crater floors include: (1) flat floors, (2) floors with pits, (3) floora with a central dome or peak, (4) and floors with a central dome and pit. Grooved terrains were divided into five mappable units. Three units of light grooved material represent small, medium, and large grooves, which are arbitrarily divided. The other two units of grooved terrain represent dark grooved materials, and reticulate grooves. Two units of ungrooved dark terrain and two units of ungrooved light terrain were defined. In Galileo Regio, two units were defined repesenting large furrowed grooves, and smaller grooves which are orthogonal to the furrowed grooves.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geology Program, 1983; p 314-316
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  • 53
    facet.materialart.
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    In:  CASI
    Publication Date: 2006-04-06
    Description: The relative time of emplacement of some major rock units on Mars was recognized to some degree from geologic mapping using Mariner Images. Correlation charts showing the map units and their position in sequence, however, displayed little discrimination in their vertical range of occurrence. A more detailed time-stratigraphy is currently being developed as Viking geologic mapping of the planet progresses.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geology Program, 1983; p 296-297
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  • 54
    Publication Date: 2006-04-06
    Description: Although many radar profiles and images of the area within 20 deg of Mercury's equator had been obtained from 1971 to 1981, at both Goldstone and Arecibo radar facilities, surprisingly little geological analysis had been done with these data until recently. Topographic profiles and radar roughness reflectivity images which can be derived from these data will be crucial in completing the geological mapping of Mercury now underway at the U.S. Geological Survey. Processing of available radar data must be completed to establish any systematic relationship between radar reflectivities and roughness, density, dielectric constant, and other related geological parameters. Specific tasks accomplished for these purposes include the following. Documentation was located and searched to establish the type and quantity of Goldstone 12.5 cm radar observations which were available for Mercury. Data has been collected during approximately 50 observation periods from 1971 to 1981. About half of the data, collected during 1972 and 1973, have been processed, but without adequate documentation. A standardized, well-documented procedure for processing and analysis for all Goldstone Earth-based observations of Mercury was established.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geology Program, 1983; p 284-286
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  • 55
    Publication Date: 2006-04-06
    Description: The origin of Mars surface units and the extent of subsequent cratering play key roles in determining surface texture. At scale sizes of 0.1-10 meters, however, there is a growing body of evidence that wind is the dominant force. The direct and indirect evidence which implies that meter-scale surface texture on Mars is controlled by the wind is presented. Since radar is uniquely sensitive to structure on these scales, radio wave scattering data can provide insight on aeolian activity available from no other source.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geology Program, 1983; p 273-275
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  • 56
    Publication Date: 2006-04-06
    Description: Two old volcano-tectonic collapse structures are exposed north and northeast of the huge shield volcano, Olympus Mons. They are semicircular and were probably low shield volcanoes similar to Alba Patera, but whose central portions have subsided or collapsed. They form the basement upon which younger volcanic materials of Alba Patera Olympus Mons have been emplaced. The oldest structure, Acheron Fossae is over 700 km across and is north of Olympus Mons. It has a surface of considerable relief broken by graben and extensive en echelon and parallel fractures and faults with varied displacements. Acheron Fossae is the most densely cratered in the Olympus Mons region. The structure must have formed very early in martian time. The second is Halex Fossae, northeast of Olympus Mons. Where exposed, it is cut by a series of arcuate grabens that become closer spaced toward its center. The radii of the fractures indicate that the structure may be at least 250 km across and centered beneath the Olympus Plains. Lava flows appear to have issued from some of the arcuate fractures and to have flowed radially away from the center of Halex Fossae. North of Halex Fossae, material of the same age as Halex Fossae overlaps Acheron Fossae.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geology Program, 1983; p 293-295
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  • 57
    Publication Date: 2006-04-06
    Description: High spatial resolution data from the Viking infrared thermal mapper (IRTM) are used to examine the Tharsis volcanoes which are situated within a vast area of low thermal inertia material very fine particle size or very high porosity, with the volcanoes having the lowest thermal inertias. Thermal infrared images of the 1823 flow on Kilauea's southwest rift zone show lower thermal inertias near the vent area where shelly pahoehoe is common while individual channelized aa flows with abundant broken pahoehoe slabs are higher thermal inertia. The increase in aa flows to the southeast leads to a general trend of increasing thermal inertias from near vent to distal areas. Martian shield volcanoes have thermal inertias equal to or higher than their surrounding plans when atmospheric effects are removed from the data. The general increase in thermal inertias away from the summit calderas is consistent with the trend of the Hawaiian 1823 flow and may be related to changing lava properties away from the summit.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geology Program, 1983; p 266-267
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  • 58
    Publication Date: 2006-04-06
    Description: A photometrically and geometrically reduced data base is being produced for the Galilean Satellites using Voyager Imaging data. The basic data set used is essentially all the useful satellite images returned by Voyager. Each frame was radiometrically calibrated and many are projected into cartographic formats. Mosaics of low, medium and high resolution frames being made for each satellite consist of registered digital images with intensity values scaled through a traceable calibration procedure to normal albedo values. Many of the mosaics are being made in two versions. One version is an albedo version and the second is a maximum discrimination version in which large variations in brightness across the picture are suppressed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geology Program, 1983; p 259-260
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  • 59
    Publication Date: 2006-04-06
    Description: One unique feature on Mars is the presence of ring furrows which are apparently produced by inversion of topography at the rims of partially buried craters. Ring furrows are flat-floored trenches, circular in plan view, forming rings 7 to 50 km in diameter. The moat is on the order of 0.5 km deep and 2 to 10 km wide, and it surrounds a flat topped circular mesa or plateau that is 5 to 40 km across. The central plateau is at the same elevation or lower than the surrounding plain outside the ring. The circular nature and size range of ring furrows tend to suggest that these features are related to craters partially buried by younger lava flows. The rings have been formed by preferential removal of the exposed crater rims. Ground ice decay, sapping, or fluvial erosion removed the less resistant, porous material of crater rims while leaving the more resistant volcanic flow material. Differential erosion has thus led to a reversal of topography in which the original positive relief of the rim is reduced to a negative relief feature.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geology Program, 1983; p 228-229
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  • 60
    Publication Date: 2006-04-06
    Description: The morphology of channels, valleys, chaotic and fretted terrains and many smaller features on Mars is consistent with the hypothesis that localized deterioration of thick layers of ice-rich permafrost was a dominant geologic process on the Martian surface. Such ground ice deterioration gave rise to large-scale mass movement, including sliding, slumping and sediment gravity flowage, perhaps also catastropic floods. In contrast to Earth, such mass movement processes on Mars lack effective competition from erosion by surface runoff. Therefore, Martian features due to mass movement grew to reach immense size without being greatly modified by secondary erosional processes. The Viking Mission to Mars in 1976 provided adequate measurements of the relevant physical parameters to constrain models for Martian permafrost.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geol. Programs; p 209-211
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  • 61
    Publication Date: 2006-04-06
    Description: High-resolution pictures of talus slopes on Mars show small, dark streaks that characteristically widen downward. These streaks are different from the thin and even streaks of various albedos that stream from cliffs on talus slopes, but gradations between the two streak types occur and not all streaks can be classified with confidence. In order to study the nature and origin of the small, widening, dark streaks, all Viking pictures with a resolution of less than 100 m/pixel were surveyed. To date several hundred streaks were located, but only few are of high enough resolution to be confidently identified as widening downwards. The approximate dimensions of the streaks were measured and their shapes, numbers, position, and spacing on slopes were noted. They were plotted on a topographic map, and their relation to topography, geologic units, and regions of distinct thermal inertia and albedo were studied. Also noted was the season at which images containing streaks were acquired and the direction of illumination. Albedo measurements are in progress. Several streaks can be seen stereoscopically, but none are observed on color images. The observation of small dark streaks on talus slopes on Mars is compatible with an interpretation of their origin as eruptions of small masses of wet debris in places where steep walls intersect aquifers or where seasonal equatorial warming permits the local melting of ground ice.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geol. Programs; p 188-190
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  • 62
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    In:  CASI
    Publication Date: 2006-04-06
    Description: The valley networks of Mars are widely believed to have formed at a time when climatic conditions on the planet were significantly different from those that currently prevail. This view arises from the following observations: (1) the valleys form integrated branching networks which suggests fluid drainage, and water is the most plausible fluid, (2) the present atmosphere contains only minute amounts of water, (3) the networks appear to be more akin to terrestrial valleys that are eroded by streams of modest discharges than features that form by catastrophic floods, and (4) small streams of water will rapidly freeze under present climatic conditions. Climatic conditions at the time of formation of the valleys are studied based on the assumption that they were cut by running water.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geol. Programs; p 185-187
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  • 63
    Publication Date: 2006-04-06
    Description: Images of the surface of Venus obtained by the Soviet Venera 9, 10, 13 and 14 landers are analyzed to provide a basis for understanding the nature of geologic processes operating there. Bedrock is exposed at the Venera 10, 13 and 14 sites and is characterized by semi-continuous, flat polygonal to subrounded patches up to several meters in width. The bedrock surface is often dominated by sub horizontal to horizontal layered plates with thicknesses of several cm and abundant linear and polygonal vertical fractures. Soils (particles 1 cm) are abundant at the Venera 9, 10 and 13 sites, but are uncommon at Venera 14. Features indicative of a strong aeolian influence (moats, dunes, wind tails) are not observed. Several hypotheses are considered for the origin of the bedrock surfaces, and it is concluded that bedrock originated from surface lava flows. The relative freshness of features observed by the Veneras suggests that erosion rates are very low or that some bedrock surfaces are geologically young.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 76-78
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  • 64
    Publication Date: 2006-04-06
    Description: A tectonic orgin for Venus banded terrain is consistent with band spacing. Both compressional (folding) and extensional models for band formation can fit present observations. Band spacing cannot distinguish among scenarios for global heat loss and for the origin of highland terrain. Tectonic models for band formation indicate that the surface brittle layer in the venus highlands is no more than a few kilometers thick.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 74-75
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  • 65
    Publication Date: 2006-04-06
    Description: A study to determine the feasibility of conducting experiments to simulate the aeolian environment on Venus as related to wind abrasion was completed. Ideally, such experiments should involve complete investigation of weathering, in which mechanical, thermal, and chemical parameters are taken into account. This is particularly important for Venus, where atmospheric temperatures and pressures at the surface produce an environment which is equivalent to low or medium grade metamorphic conditions on Earth. Details that describe the Venus Aeolian Abrasion Device (VAAD) are included. The VAAD device would enable experiments to be conducted with the same chemistry, temperature, pressure, and other physical properties of the Venus atmosphere near the surface. The proposed device enables the important aeolian parameters to be controlled and monitored, including particle size, velocity, impact-angle and flux, atmospheric pressure, temperature, and gas composition.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 67-68
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  • 66
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    In:  CASI
    Publication Date: 2006-04-06
    Description: Why the lowlands of Mars are concentrated in the Northern Hemisphere and the highlands in the Southern Hemisphere is probably the most fundamental unsolved problem in martian geology. No explanation that accounts both for this asymmetric distribution and for the isostatic equilibrium across the scarp or sloping transition zone dividing the two provinces has been generally accepted; thinning of the lithosphere in the northern hemisphere by internal processes has been suggested. Because other lowland-highland distributions on Mars, Moon, and Mercury are controlled by impact basins, it is proposed that a giant basin formed early in Mars' history has caused the martian hemispheric dichotomy as well.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geol. Program, 1983; p 110-112
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  • 67
    Publication Date: 2006-04-06
    Description: A number of researchers have concluded that saturation equilibrium cratering exists nowhere in the solar system, and therefore that diameter distributions in even the most heavily cratered provinces reveal initial production functions related to impacting bodies. Based on this premise, different populations of impactors are identified in different epochs and regions of the solar system. These hypotheses are clearly crucial to interpreting planetary history and need further independent examination. The production function in the outer solar system may differ from that in the inner solar system, but it is also possible that viscous relaxation of ice craters or immediate flooding of craters that penetrate through an ice lithosphere into watery substrate may explain the greater deficiency of large craters on icy moons. This problem is controversial and needs more study.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of the Planetary Geol. Program, 1983; p 97-99
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  • 68
    Publication Date: 2006-04-06
    Description: Properties of the planetary surface and subsurface can affect the morphology of impact craters. A mechanism was proposed to explain pedestal craters and domed floors within fresh craters on Ganymede. Voyager 1 and 2 images with resolutions = to or 3.2 km/lp were examined and 523 fresh craters were identified. For each crater, the rim and ejecta diameters were measured, and the crater was characterized by ejecta class(es), interior features, floor morphology and target terrain. Of the craters examined, 97 show moderate to prominent doming of the crater floor; 340 craters have continuous ejecta which terminates in a scarp pedestal craters, of which 86 (25%) have a high albedo diffuse deposit beyond the pedestal.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geol. Program, 1983; p 94-96
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  • 69
    Publication Date: 2006-04-06
    Description: A systematic survey of the entire Mariner 10 coverage of Mercury was performed to determine the number, distribution and dimensions of additional ancient basins on the planet. Ancient multi-ringed basins on Mercury can be recognized by the following criteria: (1) arcs of massif chains and isolated massifs that protrude through younger units, (2) arcuate segments of lobate ridges (rupes) that align with massifs in circular patterns, (3) arcuate scarps that are aligned with ridges and massif, and (4) isolated regions of anomalously high topography within the intercrater regions of heavily cratered terrain. All of the newly identified basins predate the mercurian intercrater plains, previously held to be the oldest geologic unit on the planet. Subsequent structural evolution of various regions was influenced by the presence of these basins. Smooth plains units appear to be more extensive than mapped by Mariner 10 and more than 90 percent of them appear to be basin contained or basin related. The concentration of extensive smooth plains material within and associated with basin structural and depositional environments suggests a volcanic origin for most of this unit, analogous to the lunar maria. Basins appear to provide the basic structural pattern of early terrestrial planetary crusts.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geol. Program, 1983; p 87-89
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  • 70
    Publication Date: 2006-04-06
    Description: An improved version of the Pionner-Venus orbital data was used for a statistical analysis of global radar roughness and (alpha(0)) (rho) reflectivity. Classification maps of the venusian surface are produced in a supervised manner on the basis of statistical and empirical studies of the individual data sets. The primary objective is to assess the degree of homogeneity of surface radar properties within topographic provinces in order to map possible geologic boundaries. Maps were produced by correlating two data sets at a time. Classification of specific regions, such as Ishtar, has demonstrated that distinct geological units can be identified.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 81-82
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  • 71
    Publication Date: 2006-04-06
    Description: Interest on Venus has centered on three regions; (1) Aphrodite Terra, especially east of the main uplant portion, (2) Ishtar Terra, especially Lakshmi Planum and its bounding scarp and massifs, and (3) Beta Regio-Phoebe Regio. The last region is topographically similar to the East African rift system, and has been inferred to have a similar tectonic origin. The Aphrodite region is part of a 21,000 km long tectonic zone that seems best explained as due to extension, and that may represent hot spots clustered along an incipient divergent plate boundary. The most interesting and complex portion of this tectonic zone is that part of eastern Aphrodite between Thetis Regio and Atla Regio. In contrast, the Lakshmi Planum region has many topographic characteristics suggesting that it is a true continent, and thus indicative of convergence and a thick crust. Detailed topographic contour maps of eastern Aphrodite Terra and of Lakshmi Planum are included.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 71-73
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  • 72
    Publication Date: 2006-04-06
    Description: The results of analyses of near infrared reflectance spectra are inconsistent with numerous previous interpretations of the Reiner Gamma Formation. These include: (1) nue ardente or volcanic ash deposits, (2) volcanically derived sublimates, (3) high albedo volcanic deposits, and (4) highlands debris emplaced as impact ejecta. These results, strongly suggest that the selective preservation of high albedo features (formed by secondaries) by a local magnetic field enhancement is not a viable hypothesis. The results are generally consistent with, but place constraints on, the cometary impact hypothesis of Schultz and co-workers. While the presence of a magnetized component was not detected in either the bright or dark portions of the Reiner Gamma Formation, this material may be present in amounts under the current detection limits.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 59-61
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  • 73
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    In:  CASI
    Publication Date: 2006-04-06
    Description: On the basis of the icy conglomerate model of cometary nuclei, various observations demonstrate the spotted nature of many or most nuclei, i.e., regions of unusual activity, either high or low. Rotation periods, spin axes and even precession of the axes are determined. The observational evidence for variations in activity over the surfaces of cometary nuclei are listed and discussed. On June 11 the comet IRAS-ARAKI-ALCOCK approached the Earth to a distance of 0.031 AU, the nearest since C/Lexell, 1770 I, providing a unique opportunity for near-nucleus observations. Preliminary analysis of these images establishes the spin axis of the nucleus, with an oblioquity to the orbit plane of approximately 50 deg, and a lag angle of sublimation approximately 35 deg from the solar meridian on the nucleus. Asymmetries of the inner coma suggests a crazy-quilt distribution of ices with differing volatility over the surface of the nucleus. The observations of Comet P/Homes 1892 III, exhibiting two 8-10 magnitude bursts, are carefully analyzed. The grazing encounter produced, besides the first great burst, an active area on the nucleus, which was rotating retrograde with a period of 16.3hr and inclination nearly 180 deg. After the first burst the total magnitude fell less than two magnitudes from November 7 to November 30 (barely naked eye) while the nuclear region remained diffuse or complex, rarely if ever showing a stellar appearance. The fading was much more rapid after the second burst. The grazing encounter distributed a volume of large chunks in the neighborhood of the nucleus, maintaining activity for weeks.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 51-53
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  • 74
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    In:  CASI
    Publication Date: 2006-04-06
    Description: Dione is one of the most geologically complex of the Saturnian satellites. Crater counts and surface morphology indicates the geologic units observed are of variable age and origin. In an attempt to understand the processes which have affected Dione, a geologic map was prepared. Several geologic units were identified; ancient heavily cratered terrain, two plains units: cratered plains and lightly cratered plains, lobate deposits, crater rim deposits and bright wispy materials.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 34-36
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  • 75
    Publication Date: 2006-04-06
    Description: For large parts of the surfaces of the Galilean satellites there is no stereoscopic high resolution imagery, and so for shadow-free regions far from the terminator, the only method of obtaining topograpic information is photoclinometry, the technique of converting brightness variations into local surface tilts and hence into topographic profiles and contour maps. The conversion from brightness changes to slopes require knowledge of the angular photometric function for the type of planetary surface terrain being analyzed, i.e., the relationship describing the brightness of the surface as a function of the angles of incidence (I) and emergence (E) of light at a surface element. In order to investigate the effects of these changes on the shapes of topographic profiles deduced from the functions, an area of grooved terrain (lines 500-505, samples 550-650 on frame 20640.27 0060J2) using wide ranges of values of all the adjustable parameters in Hapke's new photometric function were analyzed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 27-28
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  • 76
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    In:  CASI
    Publication Date: 2006-04-06
    Description: Exploratory work on the structure of the Ionian lithosphere is reported. The approach is to examine temperature profiles within the lithosphere that result from different distributions of sulfur and silicates and different conductive heat fluxes, then compare such profiles with observations in the expectation that only a limited set of the profiles are possible. In this preliminary work some rather simplistic assumptions were taken and the report should be viewed more as a demonstration of a method rather than a presentation of results.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 11-13
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  • 77
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    In:  CASI
    Publication Date: 2006-02-14
    Description: Improvements to the design of the Mariner spacecraft resulted in the Viking spacecraft. The Viking spacecraft would consist of two major systems - an orbiter and a lander, while the lander would provide the means for safely delivering the scientific instruments to the surface, house, and provide the necessary power source and communication links for those experiments, the orbiter would transport the lander to Mars, rovide a platform for the Viking imaging system so that proposed landing sites could be surveyed and certified, relay lander science information back to Earth, and conduct scientific observations in its own right.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: On Mars: Exploration of the Red Planet, 1958 - 1978; p 155-202
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  • 78
    Publication Date: 2006-04-06
    Description: The Tharsis ridge system appears to form a great circle around the major volcanoes. The roughly circumferential orientation of these ridges could be interpreted as the formation of a ridge system in response to a single stress field with a center near Pavonis Mons. Wise, et al. (1979) plotted the perpendiculars to strikes of ridges on the eastern flanks of Tharsis as great circles on the upper hemisphere of an equal area net. In order to further test for circular symmetry and possible other influences on ridge orientations, normals to vector means of ridge orientations were calculated using over 1850 digitized ridge segments sampled in 10 degree boxes. Orientations of individual ridge segments were weighted by their lengths, and the magnitudes of normals to vectors means were weighted by cummulative length of the ridge segments. Normals to vector means with magnitudes less than 100 km are not shown. Assuming a single fold origin for ridges, the resulting plot shows compressive stress trajectories for the ridges in the Tharsis region. The averaged compressive stress orientation around Tharsis confirm the suggestion by Wise, et al. that the ridge system is not concentric to any single point.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geology Program, 1983; p 304-306
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  • 79
    Publication Date: 2006-04-06
    Description: In this paper the tectonic features of the Elysium region are identified and characterized. Identification of features was made using USGS controlled photomosaics (Elysium quadrangle, and portions of Amenthes and Cebrenia quadrangles); Viking Orbiter photographic data were used in individual cases to assist in identification. The positions and orientations of tectonic features can then be used, in conjunction with estimates of the mass of the volcanic load obtained from gravity modelling, to constrain the thickness of the elastic lithosphere in the region.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geology Program, 1983; p 291-292
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  • 80
    Publication Date: 2006-04-06
    Description: Several 3.8 cm radar frames were calibrated empirically by histogram fitting, because no instrument background data is available. Then data were corrected for geometric distortion by: (1) redetermining position of individual frames using most accurate recent lunar ephemerides; (2) reprojecting frames into simple cylindrical map projection; (3) using most recent catalog of lunar craters to determine the exact positions of features identifiable on radar frames; and (4) correcting for apparent distortion (misplacement of features in frames) by resampling using a different bilinear interpolation derived for each of the parallelopideds of the set defined for each frame. A hardcopy set of corrected frames was produced. Attempts to produce a mosaic of such corrected frames continue. The resulting mosaic can be used to show the systematic relationship between photographic thermal IR and radar data at different wavelengths in a region dominated by both mare and highland terrain.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geology Program, 1983; p 282-283
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  • 81
    Publication Date: 2006-04-06
    Description: Studies of the stratigraphy of southwest Coprates have led to further constraints on both the geographic extent and the relative age of the major compressional ridge forming events in the Tharsis region of Mars. Southwestern Coprates is characterized by curvilinear ridges that are regularly spaced, suggestive of harmonic folding. The western edge of the ridged plains unit of Coprates is marked by volcanic flow fronts. In an enhanced Viking-Orbiter image, a ridge can be seen completely surrounded by a flow with only a small portion of the ridge crest still exposed. Comparison of partially buried ridges on the western edge of the ridged plains to those in central Coprates suggests that flooding of the inter-ridge plains does not exceed a few hundred meters. The morphological relationship between the flow units to the west and the ridged plains indicates that the deformational events in this region predates the emplacement of the younger units.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geology Program, 1983; p 301-303
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  • 82
    Publication Date: 2006-04-06
    Description: Layered deposits within Valles Marineris and its associated system of canyons have been considered to consist of two different rock types: (1) thick, competent, cliff-forming, light and dark bedded material in canyon walls, and (2) relatively thin, alternating series of light and dark layered material, both horizontal and inclined, that form rounded hills and large flat-topped mesas rising above the canyon floors. The dissimilarity in appearance between canyon wall and floor materials, as well as their contrasting patterns of erosion, have been considered strong evidence that their modes of origin were different.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geology Program, 1983; p 298-300
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  • 83
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    In:  CASI
    Publication Date: 2006-04-06
    Description: The scarps along the margins of the Vales Marineris display a complex assemblage of forms that have been related to a variety of mass wasting and sapping processes. These scarp segments display variations in the degree of development of spur and gully topography, the number and density of apparent sapping features and the frequency of large scale landslides which reflect the age, geology and processes of slope development throughout the Valles Marineris. This regional analysis should provide more information on the geologic evolution of the Valles Marineris as well as new insight into the relative importance of different processes in the development of the scarp forms. In order to evaluate the regional variation in scarp form and the influence of time and structure on scarp development geomorphic mapping and morphometric analysis of geologically distinct regions of Valles Marineris is being undertaken.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geology Program, 1983; p 234-236
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  • 84
    Publication Date: 2006-04-06
    Description: Parallel studies of Martian geomorphic features and their analogs on Earth continue to be fruitful in deciphering the geologic history of Mars. In the context of rock weathering, the Earth-analog approach is admirably served by the study of meteorites recovered from ice sheets in Antarctica. The weathering environment of Victoria Land possesses several Mars-like attributes. Four of the five Antarctic meteorites being studied contain rust and EETA79005 further possesses a conspicuous, dark, weathering rind on one side. Secondary minerals (rust and salts) occur both on the surfaces and interiors of some of the samples and textural evidence indicates that such secondary mineralization contributed to physical weathering (by salt riving) of the rocks. Several different rust morphologies occur and emphasis is being placed on identifying the phase compositions of the various rust occurrances. A thorough understanding of terrestrial weathering features of the meteorites is a prerequisite for identifying possible Martian weathering features (if such features exist) that might be postulated to occur in some meteorites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 216-218
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  • 85
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    In:  CASI
    Publication Date: 2006-04-06
    Description: Photometric studies of crater related bright and dark streaks have strongly supported the hypothesis that the bright streaks are excess dust deposits and dark streaks are erosional windows in a partial dust cover. Red-blue (and red-violet) plots show that bright streaks are consistent with mosaics of bright red dust and background material. Here the plains are also consistent with a partial dust cover; the dark streak is the least covered area. Bright and dark streaks both reverse contrast relative to surrounding plains at phase angles over 100 deg in violet filter images. The similar phase behavior of both bright and dark streaks supports the idea that they are both changes in the amount of dust cover. Red-violet plots of bright streaks are most easily explained by mosaics of optically thick dust and plains material. Lengths of bright streaks are independent of their contrasts. This suggests the streak deposition, if in the mosaic patterns indicated above, is a function of available sites of deposition, rather than atmospheric dust loading. Contrasts of dark streaks with plains indicate the plains have fractional dust covers nealy as great as the maximum additional cover in bright streaks. The bright streaks thus store little of the global supply of dust.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geol. Program, 1983; p 161-162
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  • 86
    Publication Date: 2006-04-06
    Description: Viking Lander 1 observations on Mars were punctuated by a strong local dust storm after two martian years of mild wind conditions. Tens of micrometers of dust settled to the surface during global dust storms of the first two falls and winters; some of this dust was locally removed during the second year. A late winter local dust storm of the first year caused little or no erosion of the surface materials despite wind speeds of 25 to 30 m/s. The strong local dust storm occurred during late winter of the third martian year. Winds of this storm altered and demolished small conical piles of surface materials constructed at the onset the first winter, removed 4 to 5 mm size fragments, displaced centimeter size fragments, destroyed clouds in areas disrupted by the sampler and footpad, eroded impact pits, and darkened the sky. Movement of erosional products and tiny wind tails indicate easterly to northeasterly winds. If the 4 to 5 mm size fragments were entrained and removd by the wind, threshold friction speeds near 3 to 5 m/s would have been required for the atmospheric temperatures and pressures that prevailed during the late winter of the third year.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geol. Program, 1983; p 158-159
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  • 87
    Publication Date: 2006-04-06
    Description: There are classes of landforms whose presence on Mars is strongly suggestive, if not confirmatory, of the participation of volatiles, presumably water, in its geomorphic development: (1) valley networks, (2) outflow channels, (3) landslides, and (4) flow-ejecta blankets. The first two may represent landforms generated by the movement of volatiles from sources, while the latter two probably represent the dissipation of energy generated by forcing inputs (e.g., kinetic energy and gravity) modulated by volatiles. In many areas on Mars, all four processes have acted on the same lithologic materials and were influenced by the composition of those units, and possibility by the climatic regime at the time of their formation. One of the approaches discussed to this specific problem of landform genesis, and to the general problem of the present and past states of martian volatiles, is to attempt to constrain the distribution, amount, and history of available volatiles by using possible evidence of volatile participation expressed in the morphology of other related landforms (e.g., flow-ejecta blankets and landslides) coupled with physical models for landform genesis.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geol. Program, 1983; p 116-118
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  • 88
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    In:  CASI
    Publication Date: 2006-04-06
    Description: Most cratering experiments are designed to study the effects of a single hypervelocity impact into a target of uniform properties. Experiments involving multiple impacts are usually limited to low velocity projectiles and unconsolidated target materials. Gault described saturation cratering in an unconsolidated target. Quaide and Oberbeck studied crater forms produced by hypervelocity impact into layered targets. Several investigators have modeled the generation of either a regolith or megaregolith by repeated impact on planetary surfaces. Studies now in progress examine changes in crater morphology and target properties by repeated impact into an initially consolidated target. Current studies employ low velocity projectiles (2 g at 0.5 km/sec) and consolidated salt targets. Records of crater size, morphology, and accumulated ejecta thickness are maintained as impacts collect on the surface.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geol. Program, 1983; p 102-103
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  • 89
    Publication Date: 2006-04-06
    Description: The crater size/frequency distributions of large ( 8 km) craters on the Moon and terrestrial planets display two very different curves representing two crater populations. The heavily cratered regions of the Moon, Mercury, and Mars show the same highly structured curve which cannot be represented by a single slope distribution function. In contrast, the lunar post mare crater population has a size/frequency distribution which differs significantly from that in the highlands over the same diameter range, and can be represented by a single-slope distribution function of -2.8 differential. On areas of martian lightly cratered northern plains, the crater population is essentially identical to that of the post mare population. This indicates that the same two families of impacting objects were responsible for the cratering records on both Moon and Mars. The thickness of mantling material varies among the various plains units, and can be calculated from the depth/diameter scaling relations for martian craters.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Rept. of Planetary Geol. Program, 1983; p 85-86
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  • 90
    Publication Date: 2006-04-06
    Description: A generalized model for short period comets is developed which integrates in a fairly rigorous manner the isolation history of regions on rotating comets with specified axial orientation and the complex feedback processes involving heat, gas and dust transport, dust mantle development and coma opacity. Attention is focused on development, reconfiguration and partial or complete launching of dust mantles and the reciprocal effects of these three processes on ice surface temperature and gas and dust production. The dust mantle controls the H2O flux not only by its effect on the temperature at the ice interface but (dominantly) by its dynamic stability which strongly influences vapor diffusivity. The model includes the effects of latitude, rotation and spin axis orientation are included and applied to an initially homogeneous sphere of H2O ice and silicate using the orbital parameters of comet Encke. Numerous variations of the model, using combinations of grain size distribution, dust-to-ice ratio, latitude and spin axis orientation, are presented and discussed. Resulted for a similar nonrotating, constant Sun orientation models are also included.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 54-55
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  • 91
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    In:  CASI
    Publication Date: 2006-04-06
    Description: Imaging data from the Voyager 1 and 2 encounters with the Jupiter system provide a data set for the examination of short time-scale variations of surface features on Io. Clear evidence exists for variations near the known eruption sites and for other areas which appeared to have erupted between the encounters. Regions outside the known active eruption sites were examined in order to look for variations in the surface scattering properties which is due to undetected small-scale volcanic activity. The phase functions of many areas are intercompared in order to look for regions with phase functions outside the normal range for satellite surface properties. Areas with unusual scattering properties are related to small-scale eruptions of gas or particles. Determination of the distribution of these areas has strong implications for the resurfacing rates for Io.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 39-40
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  • 92
    Publication Date: 2006-04-06
    Description: A fundamental limitation in the quantitative analysis of planetary geomorphology and structural geology results from the absense of topographic data. Among the studies that might be addressed, were such data available, are volumetric and slope relationships of Ionian volcanics, fracture and annealing processes in icy crusts on Europa and Ganymede, and evaluation of viscous relaxation as a means of degrading landforms on Europea, Ganymede, and Callisto. A technique for acquiring topographic data on the Galilean satellites using photoclinometry was developed and applied.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 29-31
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  • 93
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    In:  CASI
    Publication Date: 2006-04-06
    Description: The Laplacian resonance amongst Io, Europa, and Ganymede was examined, taking into account tidal dissipation in Jupiter, Io and Europa. In equilibrium, it is not possible to neglect dissipation in Europa nor the torques of Jupiter on Europa and Ganymede. A formal calculation was made on the assumption that the tidal torques and the torques in orbit-orbit resonance reached an equilibrium such that the rates of decrease of the mean motions of the satellites are in the ratios 4:2:1. Q(j)/k(j)=167 Q(1)/k(1), Q(2)/k(2) = 0.44 Q(1)/K(1), where Q denotes the quality at the body's frequency of rotation, k its second degree Love number and the subscripts J, 1 and 2 denote Jupiter, Io, and Europa. The Q(J) found is at Jupiter's frequency of rotation. The rate of tidal dissipation in Europa comes to 1/5 that of Io. Such a low value of Q(2)/K(2) is plausible if dissipation in both Io and Europa is due to tidal friction in fluid against underlying and overlying solid layers.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 8-10
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  • 94
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    In:  CASI
    Publication Date: 2006-04-06
    Description: Color versions of the highest resolution Voyager images of Io were produced by combining the low resolution color images with the high resolution, clear filter images. High resolution versions of the orange, blue, and violet filter images are produced by: orange = high-res clear * low-res orange / low-res clear blue = high-res clear * low-res blue / low-res clear violet = high-res clear * low-res violet / low-res clear. The spectral responses of the high and low resolution clear filter images cancel, leaving the color, while the spatial frequencies of the two low resolution images cancel, leaving the high resolution.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 38
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  • 95
    Publication Date: 2006-04-06
    Description: Interim results of thermal and structural modeling of volcanism on Io were presented. The final results of the modeling are summarized. The basic analysis is an evaluation of the magma trigger mechanism for initiating and maintaining eruptions. Secondary aspects include models of the mechanical mode of magma emplacement, interactions with a sulphur-rich upper crust, and more speculative implications for Io's volcanism.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 14-16
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  • 96
    Publication Date: 2006-04-06
    Description: As was the case for Jupiter, Saturn formed either as a result of a gas instability within the solar nebula or the accretion of a solid core that induced an instability within the surrounding solar nebula. In either case, the proto-planet's history is divided into three major stages: early, quasi-hydrostatic evolution (stage 1); hydrodynamical collapse (stage 2); and late, quasi-hydrostatic contraction (stage 3). During stage 1, Saturn had a radius of several hundred times that of its present radius, R(s), while stage 3 began when Saturn had a radius of 3.5 R(s). Stages 1 and 2 lasted 10(6) to 10(7) years and 1 year, respectively, while stage 3 is continuing through the present epoch. During the early history of the Saturn system, giant impact events may have catastrophically disrupted most of the original satellites of Saturn. Such disruption, followed by reaccretion, may be responsible, in part for the occurrence of Trojans and co-orbital moons in the Saturn system, the apparent presence of a stochastic component in the trend of satellite density with radial distance, and the present population of ring particles.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Repts. of Planetary Geol. Program; p 6-7
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  • 97
    Publication Date: 2006-01-16
    Description: A window environmental protection assembly developed for the shuttle infrared leeside temperature experiment is described. The assembly consists of a carbon phenolic composite window mount which contains two silicon windows, a fibrous environmental protection plug to protect the windows during launch operations and ascent heating, a release mechanism used to jettison the plug just prior to atmospheric entry, and two pin puller mechanisms which retain the plug. The plug is released from the window mount assemblies using pneumatic pin pullers and separation springs in the release mechanism. The assembly was designed and tested to withstand the severe mechanical and thermal environments which could be experienced at the top of the shuttle orbiter vertical stabilizer during the ascent, on-orbit, and entry periods of the shuttle trajectory.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Marshall Space Flight Center The 15th Aerospace Mech. Symp.; p 303-329
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  • 98
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    In:  CASI
    Publication Date: 2006-02-14
    Description: Raypaths for decametric wavelength radiation in Jupiter's magnetosphere were calculated. The model-dependent raypaths with the Voyager observations were compared. Characteristics of the source regions and the influence of propagation effects were deduced. A three dimensional ray tracing program was employed to calculate the raypaths. Families of rays were launched at particular angles with respect to the magnetic field lines to generate conical sheets of radiation for various frequencies and various source locations. As the planet's magnetic field rotates, these warped sheets of radiation sweep past the observer, producing signatures in frequency versus time plots. These signatures match some of those found in the Voyager data. The greatest propagation effects occur in and around the source regions in the Io auroral oval.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Alabama Univ. in Huntsville The 1981 NASA(ASEE Summer Fac. Fellowship Program; 16 p
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  • 99
    Publication Date: 2006-01-16
    Description: Winograd's algorithm for computing the discrete Fourier transform is extended considerably for certain large transform lengths. This is accomplished by performing the cyclic convolution, required by Winograd's method, by a fast transform over certain complex integer fields. This algorithm requires fewer multiplications than either the standard fast Fourier transform or Winograd's more conventional algorithms.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Deep Space Network; p 134-140
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  • 100
    Publication Date: 2006-01-12
    Description: Spacecraft- and Earth-based studies on the physical nature of the planets Mercury, Venus, and Mars are reported. Charts and graphs are presented on planetary surface properties, rotational parameters, atmospheric compositions, and astronomical characteristics.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Found. of Space Biol. and Med., Vol. 1; p 133-196
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