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  • Chemistry  (7)
  • Geosciences (General)  (5)
  • 1
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    Paleobiology of the Mesoproterozoic Billyakh Group, Anabar Uplift, northern Siberia (1995)
    In:  Other Sources
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    Publikationsdatum: 2019-08-16
    Beschreibung: Silicified peritidal carbonates of the Mesoproterozoic Kotuikan and Yusmastakh Formations, Anabar Uplift, northeastern Siberia, contain exceptionally well-preserved microfossils. The assemblage is dominated by ellipsoidal akinetes of nostocalean cyanobacteria (Archaeoellipsoides) and problematic spheroidal unicells (Myxococcoides); both are allochthonous and presumably planktonic. The assemblage also includes distinctive mat-forming scytonematacean and entophysalidacean cyanobacteria, diverse short trichomes interpreted as cyanobacterial hormogonia or germinated akinetes, rare longer trichomes, and several types of colonial unicells. Although many taxa in the Kotuikan-Yusmastakh assemblage are long-ranging prokaryotes, the overall character of the assemblage is distinctly Mesoproterozoic, with its major features shared by broadly coeval floras from Canada, China, India, and elsewhere in Siberia. Microfossils also occur in middle to inner shelf shales of the Ust'-Il'ya and lower Kotuikan Formations. Leiosphaerid acritarchs (up to several hundred microns in diameter) characterize this facies. As in other Mesoproterozoic acritarch assemblages, acanthomorphic and other complex forms that typify Neoproterozoic assemblages are absent. The combination in Billyakh assemblages of exceptional preservation and low eukaryotic diversity supports the hypothesis that nucleated organisms diversified markedly near the Mesoproterozoic-Neoproterozoic boundary. The assemblages also demonstrate the antiquity of cyanobacteria capable of cell differentiation and suggest the importance of both changing peritidal substrates and evolving eukaryotes in determining stratigraphic patterns of Proterozoic prokaryotes. The permineralized assemblage contains 33 species belonging to 17 genera. Ten new species or new combinations are proposed: Archaeoellipsoides costatus n. sp., A. elongatus n. comb., A. dolichos n. comb., A. minor n. nom., A. crassus n. comb., A. major n. comb., A. bactroformis n. sp., Veteronostocale medium n. sp., Filiconstrictosus cephalon n. sp., and Partitiofilum yakschinii n. sp.
    Schlagwort(e): Geosciences (General)
    Materialart: Journal of paleontology (ISSN 0022-3360); 69; 1 Pt 2; 1-37
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  • 2
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    Paleobiology of the Mesoproterozoic-Neoproterozoic transition: the Sukhaya Tunguska Formation, Turukhansk Uplift, Siberia (1997)
    In:  Other Sources
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    Publikationsdatum: 2019-08-16
    Beschreibung: Silicified carbonates of the latest Mesoproterozoic Sukhaya Tunguska Formation, northwestern Siberia, contain abundant and diverse permineralized microfossils. Peritidal environments are dominated by microbial mats built by filamentous cyanobacteria comparable to modern species of Lyngbya and Phormidium. In subtidal to lower intertidal settings, mat-dwelling microbenthos and possible coastal microplankton are abundant. In contrast, densely woven mat populations with few associated taxa characterize more restricted parts of tidal flats; the preservation of vertically oriented sheath bundles and primary fenestrae indicates that in these mats carbonate cementation was commonly penecontemporaneous with mat growth. Eoentophysalis mats are limited to restricted environments where microlaminated carbonate precipitates formed on or just beneath the sediment surface. Most microbenthic populations are cyanobacterial, although eukaryotic microfossils may occur among the simple spheroidal cells interpreted as coastal plankton. Protists are more securely represented by large (up to 320 micrometers in diameter) but poorly preserved acritarchs in basinal facies. The Sukhaya Tunguska assemblage contains 27 species in 18 genera. By virtue of their stratigraphic longevity and their close and predictable association with specific paleoenvironmental conditions, including substrates, Proterozoic cyanobacteria support a model of bacterial evolution in which populations adapt rapidly to novel environments and, thereafter, resist competitive replacement. The resulting evolutionary pattern is one of accumulation and stasis rather than the turnover and replacement characteristic of Phanerozoic plants and animals.
    Schlagwort(e): Geosciences (General)
    Materialart: Precambrian research (ISSN 0301-9268); 85; 4-Mar; 201-39
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  • 3
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    Taphonomic and evolutionary changes across the Mesoproterozoic-Neoproterozoic transition (1995)
    In:  Other Sources
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    Publikationsdatum: 2019-08-15
    Beschreibung: The principal biological distinction between Mesoproterozoic and Neoproterozoic is the abundance and diversity of eukaryotic fossils in the Neoproterozoic rocks, but the two eras also differ in the composition of preserved cyanobacterial assemblages. Evolving eukaryotes provide a partial explanation for observed differences in prokaryotic fossils, but the taphonomic and environmental influences of shifting carbonate depositional pattern are also important.
    Schlagwort(e): Geosciences (General)
    Materialart: Neues Jahrbuch fur Geologie und Palaontologie. Abhandlungen (ISSN 0077-7749); 195; 3-Jan; 289-302
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  • 4
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    Microfossils in cherts from the Mesoproterozoic (Middle Riphean) Debengda Formation, the Olenek Uplift, northeastern Siberia (1994)
    In:  Other Sources
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    Publikationsdatum: 2019-08-15
    Beschreibung: Silicified shallow-water marine carbonate deposits of the Proterozoic Debengda Formation (the Olenek Uplift, northeastern Siberia) contain well preserved microfossils. One or two distinct assemblages consists only of filamentous Siphonophycus microfossils, which are presumably the extracellular sheaths of hormogonium cyanobacteria. The other is dominated by coccoidal microfossils, first by the entophysalidacean cyanobacterium Eoentophysalis. The coccoidal assemblage was recognized in the layered carbonate precipitate structures of a superficially stromatolite appearance. Despite its simple composition, the microfossil assemblage supports the generally accepted Mesoproterozoic (middle Riphean) age of the Debengda Formation. This conclusion corresponds to the available data on isotopic geochronology, and to the composition of columnar stromatolites from the Dehengda Formation. Both the structural features and carbon isotopic composition of its rocks are comparable to those of rocks of known Mesoproterozoic age, but differ from the characteristics of definitely Neoproterozoic deposits.
    Schlagwort(e): Geosciences (General)
    Materialart: Stratigraphy and geological correlation = Stratigrafiya, geologicheskaya korrelyatsiya (ISSN 0869-5938); 2; 1; 19-33
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  • 5
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    Microfossils in cherts from the Middle Riphean (Mesoproterozoic) Avzyan Formation, southern Ural Mountains, Russian Federation (1994)
    In:  Other Sources
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    Publikationsdatum: 2019-08-15
    Beschreibung: A diverse assemblage of well-preserved microorganisms has been detected in black cherts from the approximately 1200 Ma-old Avzyan Formation (Suite) of the southern Ural Mountains, Russian Federation. The lower Kataskin Member contains a diverse, abundant microbiota dominated by mat-forming filamentous cyanobacteria, several types of colonial unicells, and morphologically distinctive stalked cyanobacteria. The upper Revet Member contains a less diverse biota dominated by unicellular cyanobacteria. Palaeoecological evidence indicates that the microbial community of the Kataskin Member inhabited a shallow water, presumably marine, carbonate environment. Revet microorganisms possibly lived in restricted peritidal environments. The biostratigraphic significance of the Avzyan microbiota is limited. Many of the taxa are long-ranging; they were already abundant in Palaeoproterozoic successions and continue into the Neoproterozoic. Nevertheless, in many respects, the Kataskin assemblage is comparable to those reported from the Middle-Late Riphean deposits of Northern America, Australia and Eurasia. The following taxa are here described: Chroococcaceae-Eogloeocapsa avzyanica Sergeev, Gloeodiniopsis lamellosa Schopf emend. Knoll et Golubic; Entophysalidaceae-Eoentophysalis belcherensis Hofmann; Dermocarpaceae-Polybessurus bipartitus Fairchild ex Green et al.; Nostocaceae-Eosphaeronostoc kataskinicum Sergeev; Nostocaceae or Oscillatoriaceae-Siphonophycus robustum (Schopf) emend. Knoll et Golubic emend. Knoll et al., Siphonophycus sp.; Incertae sedis-Eosynechococcus amadeus Knoll et Golubic.
    Schlagwort(e): Geosciences (General)
    Materialart: Precambrian research (ISSN 0301-9268); 65; 231-54
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  • 6
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    Sulphur-containing polyarylenequinodiimides (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 1125-1141 
    Details
    ISSN: 0887-624X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Different synthetic approaches have been used for preparing some new polymers relating to sulphur-containing polyarylenequinodiimides. The latter have been obtained both from quinodi-imidedichloride and aromatic dithioles and directly from 1,4-phenylenediamine and disulphenylchlorides. The mechanism of this process has been proposed on the basis of studying a model reaction of phenylsulphenylchloride with 1,4-phenylenediamine. Polyarylenesulphonequinodi-imides have been obtained by selective oxidation of polyarylenesulphoneamides with phenyliodozoacetate. Their structure has been proved by IR, PMR, and 13C-NMR spectroscopies. Electrophysical properties of synthesized polymers have been studied.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1988.080260414
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  • 7
    Digitale Medien
    Digitale Medien
    Ultrahigh molecular-weight polyethylene-chalk composites resulting from in situ polymerization (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 40 (1990), S. 1095-1114 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Ethylene polymerization on chalk surface under the action of TiCl4-organoaluminium compound systems yields filled composites possessing high stress-strain properties and preserving their ductility up to the chalk content of 60-70 wt %. The kinetics of the process and the properties of the composites have been investigated, as well as the interrelation between catalyst fixation technique, polymerization rate, and the ductile properties of composites containing 50 wt % of chalk. The conditions leading to the formation of “homogeneous” composites with a high ductility are examined. The possible causes of the formation of composites with a low value of elongation at break are analyzed. The principal regularities of the mechanical behavior of composites are considered for the case when the process is taking place on the filler surface and leads to “homogeneous” composites.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1990.070400703
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  • 8
    Digitale Medien
    Digitale Medien
    Investigation and pecularities of the synthesis of sulfur-containing polyacrylenes (1982)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 33 (1982), S. 647-653 
    Details
    ISSN: 0323-7648
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Es wurde die Bilding von Polyarylensulfiden bei der Polykondensation polyhalogenaromatischer Verbindungen mit Natriumsulfid untersucht, um die Hauptgesezmäßigkeiten dieser Reaktion aufzuklären. Ferner wurden die wege zur Regulierung der physikalischen Eigenschaften der schwefelhaltigen Polyarylene mittels chemischer Modifikation der Polymerketten durch Einflührung von Sulfonbrückenbindungen, reaktionsfähigen Amino-, Cyano- und Malenimid-gruppen sowie metallorganischen Fragmenten erörtert.
    Notizen: The formation of polyarylene sulfides by polycondensation of polyhalogenoaromatic compounds with sodium sulfide was investigated in order to elucidate the basic relationsships of this reaction. Further, approaches to controlling the physical properties of sulfur-containing polyarylenes by chemical modification of the polymer chain, such as introducing sulfone bridges, reactive amino, cyano and maleimide groups and metalorganic substituents, are discussed.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/actp.1982.010331107
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  • 9
    Digitale Medien
    Digitale Medien
    Zum Einfluß der Brückenbindungen auf die thermische Beständigkeit von aromatischen Bismaleinsäureimiden und aus ihnen hergestellten Polymeren (1987)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 38 (1987), S. 87-91 
    Details
    ISSN: 0323-7648
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: The thermal stabilities of N,N′-(4,4′-diphenylmethane)bismaleimide and N,N′-(4,4′-diphenylsulfide)bismaleimide, of the respective homopolymers, and of high molecular weight linear poly(aminoimide) and poly(sulfideimide) have been investigated. The homopolymers of the two bismaleimides are thermally more stable than the initial bismaleimides. The linear poly(aminoimide) and poly(sulfideimide) are thermally less stable than the bismaleimides and the homopolymers. Poly(aminoimide) shows less thermostability as compared to poly(sulfideimide), probably due to ringopening of the succinimide rings in poly(aminoimide) by secondary bridge aminogroups.
    Notizen: Die thermische Beständigkeit von N,N′-(4,4′-Diphenylmethan)bismaleinsäureimid und N,N′-(4,4′-Diphenylsulfid)-bismaleinsäureimid, der Homopolymere aus diesen beiden Verbindungen und hochmolekularer linearer Polyaminoimide und Polysulfidimide wurde untersucht. Die Homopolymere beider Bismaleinsäureimide sind thermisch beständiger als die Ausgangs-Bismaleinsäureimide. Die linearen Polyaminoimide und Polysulfidimide weisen eine geringere thermische Beständigkeit als die Bismaleinsäureimide und ihre Homopolymere auf. Die thermische Beständigkeit des Polyaminoimids ist wahrscheinlich als Folge einer Ringöffnung der Succinimidringe im Polyaminoimid durch sekundäre Aminobrückenbindungen geringer als die des Polysulfidimids.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/actp.1987.010380118
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  • 10
    Digitale Medien
    Digitale Medien
    Chemical modification as a method of synthesis of organometallic polymers (1989)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 40 (1989), S. 389-393 
    Details
    ISSN: 0323-7648
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die chemische Modifizierung wird als aussichtsreiche Methode zur Synthese organometallischer Polymere diskutiert. Hochmolekulare Verbindungen mit Benzenringen werden als Makroliganden eingesetzt, um makromolekulare Übergangsmetall-π-Komplexe zu synthetisieren.
    Notizen: Chemical modification as a prespective method for synthesizing organometallic polymers is discussed. High-molecular compounds with benzene rings are used as macroligands to synthesize macromolecular transition metal π-complexes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/actp.1989.010400606
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