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  • Polymer and Materials Science  (26)
  • Life and Medical Sciences  (16)
  • General Chemistry  (4)
  • Inorganic Chemistry
  • Physics
  • 1985-1989  (48)
  • 1970-1974
  • 1988  (48)
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  • 1985-1989  (48)
  • 1970-1974
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  • 1
    Digitale Medien
    Digitale Medien
    Iminophosphorane-mediated synthesis of mesoionic 1,3,4-Oxadiazolo-[3,2-a]pyridinylium-2-aminides (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 1495-1500 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Iminophosphoran-vermittelte Syntheses von mesoionischen 1,3,4- Oxadiazolo[3,2a]pyridinylium-2-aminidenDas Iminophosphoran 2 reagiert mit Methylisocyanat zu dem mesoionischen 1,3,4-Oxadiazolo[3,2-a]pyridinylium-2-methylaminid 3, das durch CF3SO3CH3 zum 1,3,4-Oxadiazolo[3,2-a]-pyridinium-Kation 4 methyliert wird. Struktur 4 wurde durch Röntgenstrukturanalyse gesichert. Durch Einwirkung von Base lagert das mesoionische Aminid 3 zum isomeren mesoionischen 1,3,4-Triazolo[3,2-a]pyridinylium-2-olat 11 um. Verbindung 3 wird durch (Arylimino)triphenylphosphorane in die entsprechenden 1,3,4-Oxadiazolo[3,2-a]pyridinium-2-arylaminide 12 umgewandelt, die auch aus Iminophosphoran 2 und Hydroximoylchloriden zugänglich sind.
    Notizen: Reaction of iminophosphorane 2 with methyl isocyanate yields the mesoionic 1,3,4-oxadiazolo[3,2-a]pyridinylium-2-methylamindie 3, which undergoes N-methylation with CF3SO3CH3 to give the 1,3,4-oxadiazolo[3,2-a]pyridinium cation 4. The structure of compound 4 has been established by means of X-ray crystallography. Mesoionic aminide 3 undergoes rearrangement by the action of base to give the isomeric mesoionic compound 1,3,4-triazolo[3,2-a]pyridinylium-2-olate 11. Compound 3 by the action of (arylimino)triphenylphosphoranes is converted into the corresponding 1,3,4-oxadiazolo[3,2-a]pyridinylium-2-arylaminides 12, which can be also prepared from iminophosphorane 2 and hydroximoyl chlorides.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19881210825
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  • 2
    Digitale Medien
    Digitale Medien
    Influence of chemical structure on glass transition temperatures of poly(propylene terephthalate) and poly(propylene isophthalate) (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 691-699 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Poly(propylene terephthalate)Systematic IUPAC name: poly(oxypropyleneoxyterephthaloyl). (PPTP) and poly(propylene isophthalate)Systematic IUPAC name: poly(oxypropyleneoxyisophthaloyl). (PPIP) were prepared by melt polycondensation. Different fractions with number-average molar masses in the range 5 000 - 20 000 g·mol-1 were obtained and their respective glass transition temperatures (Tg) determined by calorimetry. The solubility parameters of the polymers were obtained by viscosity measurements in different solvents and were found to be 9,4 and 9,5 cal1/2·cm-3/2 (19,2·103 and 19,4·103 J1/2·m-3/2) for PPIP and PPTP, respectively. The glass transition temperatures were compared with those reported for analogous polyesters and it was shown that intramolecular interactions highly influence the Tg of these polyesters, whereas the effect of intermolecular interactions seems to be less important.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1988.021890321
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  • 3
    Digitale Medien
    Digitale Medien
    Quantitative electromyography of the masticatory muscles of Pteropus giganteus (Megachiroptera) (1988)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 196 (1988), S. 73-106 
    Details
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Mastication has been studied by cinematography and quantitative electromyography while flying foxes, Pteropus giganteus, were freely feeding on standardized pieces of apple, soaked raisin, and banana.The primarily orthal mandibular movements are caused by mainly bilaterally symmetrical firing of all the masticatory muscles. Asymmetric activity in the superficial and deep masseter and medial pterygoid causes slight protrusion early in opening. Slight lateral deviations at the end of opening and at the start of closing are caused by asymmetric and asynchronous activity in the pterygoids and digastrics, and by asynchronous firing of the deep temporalis and zygomaticomandibularis. Food consistency affects movement characteristics as well as characteristics of muscular activity.In this study electromyograms were digitized and the number of spikes and mean amplitude per interval (set by the filming rate) recorded. Although a significant correlation exists between these descriptors, the product thereof appears to be the best predictor of certain kinematic variables (cycle length and maximum excursion of the mandible). On the other hand, the changes in magnitude of muscular activity as a function of the position of a cycle in the reduction sequence and as a function of food consistency are more translated in a variation of the mean amplitude than in a variation of the number of spikes per interval. Observed variation differs among muscles studied. It is most apparent in the superficial and deep masseter and least in the temporalis and zygomaticomandibularis.Late cycles of apple and raisin mastication are long and exhibit large gapes but almost no anterior movement. The adductor activity frequently shows a synchronized, pulsatile pattern leading to an unfused tetanus.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jmor.1051960107
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  • 4
    Digitale Medien
    Digitale Medien
    Fully aromatic poly(ether-esters) (1988)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 26 (1988), S. 313-317 
    Details
    ISSN: 0887-6258
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1988.140260707
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  • 5
    Digitale Medien
    Digitale Medien
    Eine Methode zur ldentifizierung von Gitter-Leerstellen in Zeolithen (1988)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 564 (1988), S. 72-80 
    Details
    ISSN: 0044-2313
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: A Method for the Identification of T-Atom Vacancies in the Lattices of ZeolitesSilanol groups in the lattices of zeolites can be silylated with trimethylchlorosilane and the products can be characterized by means of 29Si (CP) MAS NMR. T-atom vacancies are indicated by the formation of silylation products with three or four siloxy-linkages under mild reaction conditions as this requires the presence of three or silanol groups in favourable geometrical arrangements.
    Notizen: Am Beispiel der Zeolithe ZSM-5 und Y wird gezeigt, wie amn Gitter-Leer-stellen in Zeolithen identifizieren kann. Terminale Hydroxylgruppen, die auch Gitter-Leerstellen umgeben, werden dabei mit Trimethylchlorsilan (TCS) silyliert und die Produkte mit 29Si-(CP)-MAS-NMR untersucht. Die Anwesenheit von Gitter-Leerstellen wird angezeigt durch die Bildung von Silylierungsprodukten mit drei oder vier Siloxybindungen, die Insertion des TCS zwischen drei beziehungsweise vier terminalen Hydroxylgruppen im Zeolithgitter unter sehr milden Reaktions bedingungen entstehen.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/zaac.19885640109
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  • 6
    Digitale Medien
    Digitale Medien
    Helix-coil dynamics of a Z-helix hairpin (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1319-1327 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The helix-coil transition of a Z-helix hairpin formed from d(C-G)5T4(C-G)5 has been characterized by equilibrium melting and temperature jump experiments in 5M NaClO4 and 10 mM Na2HPO4, pH 7.0. The melting curve can be represented by a simple all-or-none transition with a midpoint at 81.6 ± 0.4°C and an enthalpy change of 287 ± 15 kJ/mole. The temperature jump relaxation can be described by single exponentials at a reasonable accuracy. Amplitudes measured as a function of temperature provide equilibrium parameters consistent with those derived from equilibrium melting curves. The rate constants of Z-helix formation are found in the range from 1800 s-1 at 70°C to 800 s-1 at 90°C and are associated with an activation enthalpy of -(50 ± 10) kJ/mole, whereas the rate constants of helix dissociation are found in the range from 200 s-1 at 70°C to 4500 s-1 at 90°C with an activation enthalpy +235 kJ/mole. These parameters are consistent with a requirement of 3-4 base pairs for helix nucleation. Apparently nucleation occurs in the Z-helix conformation, because a separate slow step corresponding to a B to Z transition has not been observed. In summary, the dynamics of the Z-helix-coil transition is very similar to that of previously investigated right-handed double helices.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270810
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  • 7
    Digitale Medien
    Digitale Medien
    Diffusion coefficients of segmentally flexible macromolecules with two subunits: A study of broken rods (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1771-1786 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A general treatment for the solution dynamics of segmentally flexible macromolecules having two subunits is presented. Bead modeling allows for a complete inclusion of hydrodynamic interactions in this treatment. The finite size of the beads is also considered, so that it is therefore possible to account properly for torsional motions of the subunits. Expressions for the components of the resistance matrix are derived. From them, the translational and rotational diffusion coefficients can be calculated. Distinction is made between hinged macromolecules, whose only internal motion is bending, and swivel-jointed macromolecules, for which torsions of the subunits are also allowed. Numerical results are presented for broken rods with the two types of flexibility. The effects of hydrodynamic interaction between arms of broken rods are about 25% for translation and under 10% for rotation. These findings give support to the treatments of Harvey, Wegener, and co-workers in which interactions were neglected. The rotational dynamics of hinged and swivel-jointed rods are compared. Although there are differences in the short-time behavior, the longest relaxation time is the same for the two cases. Finally, the validity of Wegener's rotational diffusion constants is discussed.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360271107
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  • 8
    Digitale Medien
    Digitale Medien
    Physical behaviour of stereoblock-isotactic polypropylene (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 815-821 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Preliminary results regarding the physical behaviour of a stereoblock-isotactic polypropylene are reported. The polymer was obtained using a soluble Ziegler-Natta catalyst and films were prepared by pressure molding. The particular steric configuration is responsible of low crystallinity and small crystal size; the bulk structure can be represented by a fringed micellar model in which small crystallites act as physical crosslinks. The observed behaviour being typical of a thermoplastic elastomer well agrees with the suggested model.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1988.021890413
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  • 9
    Digitale Medien
    Digitale Medien
    Viscoelastic properties of mixtures of polystyrene with low-molecular-weight poly[oxy(2,6-dimethyl-1,4-phenylene)]Dedicated to Professor H.-J. Cantow on the occasion of his 65th birthday (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 2169-2186 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A series of poly[oxy(2,6-dimethyl-1,4-phenylene)]s (PPE) (trivial names: polyphenylenether, polyoxyxylene, polyphenyleneoxide) with narrow molecular weight distribution were prepared by polymerization of 4-bromo-2,6-dimethylphenol and subsequent fractionation. The molecular weight dependence of the glass transition temperature obeys the Fox-Flory equation. Polystyrene (PS)/PPE blends (PS: number-average molecular weight M̄n = 144 000, ratio of weight- to number-average molecular weight M̄w/M̄n = 1,05) were prepared using PPE samples with molecular weights below the entanglement spacing of PPE, in order to obtain information about the influence of specific interactions on the linear viscoelastic properties in the plateau and terminal region. The iso-free-volume state turned out to be the most appropriate reference state to compare samples of various compositions. Low-molecular-weight PPE essentially acts as a solvent for polystyrene. The concentration dependence of the zero-shear viscosity η0 is proportional to φ3,6PS, φPS being the volume fraction of PS, and the temperature dependence of the logarithmic shift factor log aT indicates that interactions, which are responsible for the thermodynamic miscibility in this system, do not alter the linear viscoelastic properties of PS. The concentration dependence of the plateau modulus (G(0)N ∝ φ1,2 for PS/PPE-1500) blends is explained by an additional small elastic contribution of the short PPE chains to the plateau modulus at higher frequencies.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1988.021890920
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  • 10
    Digitale Medien
    Digitale Medien
    Study of the initiation mechanism of the vinyl polymerization with the system persulfate/N,N,N′,N′-tetramethylethylenediamine (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 77-83 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The reaction mechanism of the redox initiation system persulfate/N,N,N′,N′-tetramethyl-ethylenediamine (TMEDA) was studied by spin trapping technique and ESR spectra. The free radical (CH3)2NCH2CH2(CH3)NCH·2 (1) is one of the initial free radicals responsible for the initiation of the vinyl polymerization in addition to the sulfate free radical (HO3SO·). The result of amino end group analysis confirmed the fact that the free radical 1 initiates vinyl polymerization and becomes the end group of the resulting polymers. The effect of TMEDA concentration on the final percentage of conversion of acrylamide polymerization and on the molecular weights of the resulting polymer were also studied. An initiation mechanism was proposed.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1988.021890108
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