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  • Salinity  (38)
  • Polymer and Materials Science  (23)
  • Statistical Physics
  • 1
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    Standard and inverse bond percolation of straight rigid rods on square lattices (2018)
    American Physical Society (APS)
    Details
    Publikationsdatum: 2018-04-11
    Beschreibung: Author(s): L. S. Ramirez, P. M. Centres, and A. J. Ramirez-Pastor Numerical simulations and finite-size scaling analysis have been carried out to study standard and inverse bond percolation of straight rigid rods on square lattices. In the case of standard percolation, the lattice is initially empty. Then, linear bond k -mers (sets of k linear nearest-neighbor bond... [Phys. Rev. E 97, 042113] Published Tue Apr 10, 2018
    Schlagwort(e): Statistical Physics
    Print ISSN: 1539-3755
    Digitale ISSN: 1550-2376
    Thema: Physik
    Publiziert von American Physical Society (APS)
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  • 2
    Digitale Medien
    Digitale Medien
    Fourier transform IR study of enzymatically isolated tomato fruit cuticular membrane (1992)
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 1425-1429 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Fourier transform ir study on enzymatically isolated tomato fruit cuticle has been performed. Assignments of the observed frequencies to functional groups present in the cuticular membrane yield information on the polyester cross-links and the interactions among the different components that form this plant protective barrier. © 1992 John Wiley & Sons, Inc.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360321102
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  • 3
    Digitale Medien
    Digitale Medien
    Dextran functionalized by cyclic carbonate groups as supports of bioactive compounds (1993)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 206 (1993), S. 77-85 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Es werden Aspekte der Reaktion von Dextran mit Ethyl-chlorformiat und Triethylamin als Katalysator behandelt. Mittels 1H- und 13C NMR-Spektroskopie wurden in den gebildeten modifizierten Dextranen cyclische und acyclische Carbonatgruppen nachgewiesen. Vorversuche zeigten, daß die Reaktion cyclischer Carbonatgrupen mit verschiedenen Amin-Modellverbindungen stark vom Basencharakter des Amins abhängt. Phenethylamin und Tyramin wurden quantitativ an aktiviertes Dextran mit cyclischen Carbonatgruppen gebunden. Die Dextran-Phenethylamin- und Dextran-Tyramin-Addukte werden unter den angewendeten Bedingungen (pH 1,0 oder 9,1 bei 37°C) nicht heterogen hydrolysiert.
    Notizen: This work deals with some features of the reaction of dextran with ethyl chloroformate using triethylamine as catalyst. The presence of cyclic and acyclic carbonate groups in the resulting modified dextrans was demonstrated by IR, 1H and 13C NMR spectroscopy. Preliminary experiments have shown that the reaction of cyclic carbonate groups with several model amines is greatly dependent on the basic character of the amine. Model amino type drugs (Phenethylamine and tyramine) were quantitatively bound to activated dextran with cyclic carbonate groups. The heterogeneous hydrolysis of dextran-phenethylamine or dextran-tyramine adducts showed that no hydrolysis takes place under the applied conditions.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1993.052060108
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  • 4
    Digitale Medien
    Digitale Medien
    Dextran functionalized by 4-nitrophenyl carbonate groups. Aminolysis reactions (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 225 (1995), S. 123-130 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Dextran wurde mit 4-Nitrophenylchloroformat und Pyridin als Katalysator umgesetzt. Die Struktur der modifizierten Dextrane wurde mittels IR-, 1H- und 13C-NMR-Spektroskopie bestimmt. Unter den gewählten Reaktionsbedingungen entstehen nur acyclische Carbonate. Vorversuche zeigten, daß die Reaktion der 4-Nitrophenyl-chloroformat-Gruppen mit verschiedenen Amin-Modellverbindungen stark von der Basizität des Amins abhängt. Die Anbindung der Modellamine Phenethylamin und Tyramin an das modifizierte Dextran war befriedigend. Die Dextran-Phenethylamin-und Dextran-Tyramin-Verbindungen sind gegen heterogene Hydrolyse bei 37°C (pH 9 und pH 1) weitgehend beständig.
    Notizen: The modification reaction of dextran with 4-nitrophenyl chloroformate using pyridine as catalyst was studied. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy as well as by chemical analysis. Under the used experimental conditions only acyclic carbonate groups have been detected. Preliminary experiments have shown that the reaction of 4-nitrophenyl carbonate groups with several model amines is greatly dependent on the basic character of the amine. Model amino-type drugs (phenethylamine and tyramine) were satisfactorily bound to activated dextran with 4-nitrophenyl carbonate groups. The heterogeneous hydrolysis of dextran-phenethylamine or dextran-tyramine adducts showed that no significant hydrolysis takes place under the applied conditions (pH 1 and pH 9, 37°C).
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1995.052250111
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  • 5
    Digitale Medien
    Digitale Medien
    Condensation of DNA by basic protiens does not depend on protien composition (1994)
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 285-292 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We have studied by electron microscopy the size and morphology of the complexes obtained with different DNAs (between 500 and 5243 base pairs long) and four different proteins: sea urchin histone H1; sea cucumber histone φ0, chicken erythrocyte histone H5, and clupeine. Surprisingly, the type of protein used has only a marginal influence on the complexes formed. The molecular weight and topology of DNA do not show any influence. The size of the complexes depends strongly on the ratio of positive to negative charges and also on the ionic conditions. Our studies have been mainly carried out at a ratio of 0.4. Under these conditions the average thickness of rods and toroids observed varies between 165 Å at 1.5 mM salt to 290 Å at 100 mM salt, with minor variations around these values depending on the type of DNA and protein used. We conclude that the formation of DNA condensates is mainly determined by a balance of electrostatic and intermolecular forces, the influence of specific interactions is only marginal. This conclusion seems to apply not only to the complexes described here, but also to chromatin fibers and to DNA condensed by low molecular weight counterions and other compounds (polyamines, inorganic ions, ethanol, etc.). © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360340214
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  • 6
    Digitale Medien
    Digitale Medien
    Terpolymérisation acrylonitrile-styrène-acrylate de méthyle, 4Partie 3: cf. J. Guillot, L. Rios Guerrero, Makromol. Chem. 183, 1979 (1982). Copolymérisation en emulsion styrène-acrylate de méthyle en réacteur fermé (batch) en présence de persulfate de potassium (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 361-377 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: To improve the knowledge of emulsion copolymerization of monomers both swelling their copolymers, but which are of quite different polarity (water solubility), a series of styrene (S)/methyl acrylate (MeA) copolymerizations was carried out in batch at 50°C with potassium persulfate as initiator. The overall rates of copolymerization increase with the amount of MeA in the monomer feed. Copolymer composition follows the usual copolymerization equation if bulk/solution reactivity ratios (rij) and monomer partition between aqueous and organic phase are taken into account (simulation). However, accurate kinetic data at low conversion (gas chromatography) put in evidence an enhanced polymerization of the more hydrophilic monomer (MeA), which can be attributed to polymerization in the water phase. Particle sizes increase with conversion and tend to a limiting value, the higher the MeA content is. Particle number (Np), which is practically constant with conversion of S homopolymerization, tends to increase with MeA content as polymerization proceeds. This trend is enhanced if the emulsifier (sodium dodecanesulfonate, SDS) concentration is increased. Overall propagation rate constants were estimated as function of the experimental conditions and monomer concentration within the particles. From kinetic data (rate of polymerization) and Np, it was found that the average number of radicals per particle, ñ, remains close to 0,5. It was then possible considering S(kp = 125 1 · mol-1 · s-1) as a standard monomer, to estimate the polymerization rate constant for MeA (335 1 · mol-1 · s-1). Since adsorption of emulsifier was shown to be closely related to particle surface composition, the specific area As of SDS was measured on latices at various conversions and initial monomer feeds. As conversions increases, the particle surface appears to be richer and richer in MeA, which corresponds to a particle structuration. Strong and weak acid group titration is also in quite good agreement with the colloidal behaviour.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1988.021890211
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  • 7
    Digitale Medien
    Digitale Medien
    Terpolymérisation acrylonitrile-styrène-acrylate de méthyle, 5Partie 4: cf.1. Copolymérisation en emulsion styrène-acrylate de méthyle en réacteur fermé en présence du styrène amorceur redox persulfate the potassium/hydrogénodisulfite de sodium (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 379-397 
    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 emulsion copolymerizations of styrene (S) with methyl acrylate (MeA) initiated by the redox system potassium persulfate (KPS)/sodium hydrogen disulfite (SBS) was carried out at 50°C. The monomer feed composition and the monomer/water (M/W) ratios were widely varied. The polymerization rate was found to be higher than in the case when only KPS was applied. Initial (influence of polymerization in water phase) and final copolymer molecules (accumulation of MeA in the feed due to a lower reactivity) are richer in the more hydrophilic monomer (MeA). It could be shown that a high water solubility makes the emulsion reactivity ratios to be “apparent” kinetic parameters, which result in a higher number of azeotropic compositions, compared to bulk or solution, according to the M/W ratio. Particle sizes are smaller and the size distribution is larger than in polymerizations in the presence of KPS alone. Particle number (Np) tends to increase with conversion for monomer mixtures rich in MeA, contrary to S homopolymerizations in which Np remains constant. Comparison of Np and kinetic data suggests that only part of the particles in actually active in polymerization (N*p). N*p can be estimated assuming that the average number of radical per particle, ñ remains close to 0,5 - as found in a previous study - which gives also an estimate of very tiny particles generated at low conversion and undetectable by the usual QELS and MET techniques. The experimental data, to some extent, allow to quantify the competition between micellar and homogeneous nucleation mechanisms.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1988.021890212
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  • 8
    Digitale Medien
    Digitale Medien
    Absolute calibration of microwave loss in ESR spectrometers (1994)
    Weinheim : Wiley-Blackwell
    Advanced Materials 6 (1994), S. 59-62 
    Details
    ISSN: 0935-9648
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/adma.19940060112
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  • 9
    Digitale Medien
    Digitale Medien
    Functionalization of dextran: Incorporation of carboxy groups by O-succinoylation (1992)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 194 (1992), S. 79-89 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die Modifizierung von Dextran rnit Bernsteinsaureanhydrid unter Verwendung von Pyridin als Katalysator und DMF/LiCl als Liisungsmittel wurde untersucht und die Struktur der gebildeten Polymeren IH- und 13C-NMR-spektroskopisch bestimmt. Es wurde eine lineare Abhangigkeit zwischen der Reaktionsgeschwindigkeit und der Bernsteinsaureanhydrid-Konzentration gefunden, wobei die Reaktion beziiglich Pyridin erster und beziiglich des Polymeren zweiter Ordnung war. Die Aktivierungsenergie betrug 69,O kUmol. Die I3C-NMR-Spektren von teilweise, d. h. rnit nur einer SuccinatGruppe pro Anhydroglucose-Einheit modifiziertem Dextran wurden untersucht, um die Selektivitat der Reaktion von Dextran rnit Bernsteinsaureanhydrid in homogener Phase abzuschatzen. Die Analyse der Ring-Kohlenstoffatome der Anhydroglucose-Einheit zeigte, dal3 die Reaktivitat der einzelnen Hydroxy-Gruppen in der Reihenfolge C-2 3 C-3 〉 C-4 abnimmt; Proben rnit einem hoheren Substitutionsgrad, d. h. rnit mehr als einer Succinat-Gruppe pro Anhydroglucose-Einheit, zeigten die umgekehrte Reihenfolge C-4 〉 C-3 〉 C-2. Dieses Ergebnis ist vermutlich auf intramolekulare Wasserstoffbriicken Bindungen in Verbindung rnit sterischen Effekten zuriickzufiihren.
    Notizen: The modification reaction of dextran with succinic anhydride using pyridine as catalyst and N,N-dimethylformamide/lithiumchloride system as solvent was studied. The structure of the resulting polymers was determined by means of 1H and 13C NMR spectroscopy. A linear dependence of the reaction rate on succinic anhydride concentration was found. The orders with respect to pyridine and polymer concentrations were 1 and 2, respectively. The activation energy was found to be 69.0 kJ/mol. 13C NMR spectra at 75.4 MHz of partially modified dextran with monosuccinate groups were studied in order to evaluate the selectivity of the reaction of dextran with succinic anhydride in the homogeneous phase. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of individual hydroxy groups decreases in the order C-2 ∽ C-3 〉 C-4. For samples with higher degree of substitution the order is C-4 〉 C-3 〉 C-2. The results were explained by considering the formation of intramolecular hydrogen bonds as well as by steric considerations.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1992.051940107
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  • 10
    Digitale Medien
    Digitale Medien
    Ir and Raman spectra of L-aspartic acid and isotopic derivatives (1994)
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 1065-1077 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The ir and Raman spectra of L-aspartic acid, L-aspartic-d4 acid, and L-aspartic-15N acid as solid samples have been recorded and measured. The data obtained were used to propose a general assignment of the fundamental vibrational modes in the basis of the isotopic shifts measured and correlations with previous data reported for other amino acids and related molecules. A MNDO-scaled semiempirical force field was obtained, and vibrational frequencies and descriptions were used to support the previous assignments based on experimental features. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360340810
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