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  • 1
    ISSN: 0941-1216
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The lifetime of cation selective carrier-PVC-membranes partially depends on the components' remaining in the membrane. An exchange of monomeric by polymeric plasticizers with low tendency to migrate lengthens the function time drastically. Other than for Na+ - and NH4+-selective membranes, it is essential for K+ - and Ca2+-selective membranes and optional for H+-selective membranes to incorporate lipophilic anions in order to make the phase transfer catalysis more efficient. The resistence to saponification of phthalic acid polyester gives H+-selective membranes a high stability of measured values even in the alkaline range.For anion selective PVC-membranes, instead of cation selective plasticizers the plasticizing qualities of a liquid charged ligand should be used.The tubular carrier-PVC-membranes of our ion selective flow through measuring systems are diffusion welded to the ends of two PVC-tubes [1] so that they are absolutely tight with no risk of potential leakage. Migration of the membrane components plasticizer and ionophore across this border as well as their extraction [2, 3] into the measuring solution [4] will naturally reduce the membrane's functionning time [5].
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    ISSN: 0021-8383
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Substituted Alkinyles as Axial Ligands at Hemine Like Bound Iron(III) - Incorporation into a Spectrochemical Series.Substituted lithium alkynyles Li—C≡C—R (R = tBu, Ph, p-Cl—C6H4, Me3Si, iPr3Si, Ph3Si) react with the hemine like macrocyclic iron(III) complex 6,13-di(ethoxycarbonyl)-5, 14-dimethyl-1, 4, 8, 11-tetraazatetradeca-4,6,12,14-tetraenato[2-]iron(III)-iodide (formula 2;) in tetrahydrofuran to form anionic low-spin di-adducts [fe(C≡C—R)2]-. The incorporation of the alkynyles into a spectrochemical series of the axial ligands (studied by the sharp equatorial-ligand-to-metal CT absorption band) results in the wavelength-sequence (nm): OH- (≍ 510) « N3- (≍ 625) 〈 tBu—C≡C- (664) 〈 NH3 (666) 〈 Ph—C≡C- (692) 〈 Ph—NH2 (695) 〈 Me3Si—C≡C- (698) 〈 SCN- (713) 〈 Ph3Si—C ≡ C- (716) 〈 CN- (739) 〈 4-picoline (759) 〈 pyridine (765) 〈 nicotinamide (776) 〈 methylnicotinat (788) 〈 pyrazine (798) and points to a significant π-acceptor ability of the silyl substituents.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    facet.materialart.
    Unbekannt
    In:  Other Sources
    Publikationsdatum: 2011-08-24
    Beschreibung: Proposals for continuing the search for extant life on Mars are primarily predicated on the assumption that specialized environmental niches that could support a biota may exist on the planet. Before attempting any critical tests for extant organisms, either in situ or on returned samples, it is imperative to determine whether any such sites actually exist. If, through remote sensing and landed instrumentation, sites of potential biological interest are discovered and characterized, biological tests can then more effectively be planned to elicit the presence of organisms that are adapted to living in these particular environments.
    Schlagwort(e): Exobiology
    Materialart: Icarus (ISSN 0019-1035); Volume 120; 431-6
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Publikationsdatum: 2019-07-13
    Beschreibung: No abstract available
    Schlagwort(e): Exobiology
    Materialart: Analytical chemistry (ISSN 0003-2700); 67; 19; 605A-610A
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Publikationsdatum: 2019-07-13
    Beschreibung: The mechanism for synthesis of monounsaturated fatty acids under aerobic and anaerobic conditions was studied in the facultative anaerobic cyanobacterium, Oscillatoria limnetica. The hexadecenoic acid (C16:1) of aerobically grown O. limnetica was shown to contain both the delta 7 (79%) and delta 9 (21%) isomers, while the octadecenoic (C18:1) acid was entirely the delta 9 acid. Incorporation of [2-14C] acetate into the fatty acids under aerobic conditions resulted in synthesis of the delta 7 and delta 9 C16:1 and the delta 9 C18:1. Synthesis of unsaturated fatty acids in the presence of DCMU required sulfide. Anaerobic incubations in the presence of DCMU and sulfide (less than 0.003% atmospheric oxygen) resulted in a two-fold increase in monounsaturated fatty acids of both delta 7 and delta 9 C16:1 and delta 9 and delta 11 C18:1. The synthesis of these is characteristic of a bacterial-type, anaerobic pathway.
    Schlagwort(e): Exobiology
    Materialart: Archives of microbiology (ISSN 0302-8933); 152; 215-7
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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