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  • Springer  (196)
  • American Journal of Science  (7)
  • 1980-1984  (192)
  • 1955-1959  (11)
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  • 1
    Electronic Resource
    Electronic Resource
    Traveling bands of chemotactic bacteria in the context of population growth (1984)
    Springer
    Bulletin of mathematical biology 46 (1984), S. 19-40 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A mathematical model for traveling bands of motile and chemotactic bacteria in the presence of cell growth and death is examined. It is found that asymptotic traveling wave solutions exist in the absence of chemotaxis, due to the balance of growth, death and random motility. Thus random motility confers the ecological advantage of population propagation through migration into nutrient-rich regions. The presence of chemotaxis amplifies this advantage by moving more cells into higher nutrient concentration regions, resulting in larger and faster bands. Therefore there seem to be two types of traveling bands that can be attained by chemotactic bacteria in the presence of growth and death: (1) these growth/death/motility bands; and (2) pure chemotactic ‘Keller-Segel'-type bands. Comparison to experimental observations by Chapman in 1973 indicate that the latter seem to be formed. The relationship between these two types of solution is at present uncertain. The growth/death/motility bands may have relevance on longer time or distance scales characteristic of microbial ecological systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02463721
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  • 2
    Electronic Resource
    Electronic Resource
    Traveling waves in a simple population model involving growth and death (1980)
    Springer
    Bulletin of mathematical biology 42 (1980), S. 397-429 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract The structure of solutions to a simple spatially dependent population model involving growth and death is investigated. Two forms of motility of the population are considered: (1) random motion only modeled by a Fickian law, and (2) a directed component of motion (chemotaxis), included in addition to the random motion. Under certain growth conditions a traveling wave of constant speed is approached. This speed can be increased by the addition of the chemotaxis with a corresponding increase in the asymptotic population. Development of initial conditions into a wave is illustrated numerically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02460793
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  • 3
    Electronic Resource
    Electronic Resource
    New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (Inifers) (1981)
    Springer
    Polymer bulletin 5 (1981), S. 379-384 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary This paper concerns the synthesis and characterization of new Si-Cl and Si-H end-groups containing polyisobutylenes. The syntheses involved 1) The preparation of polyisobutylenes carrying one or two -CH2C-(CH3)=CH2 termini, ii) Hydrosilylation with H(CH3)2-SiCl, H(CH3)SiCl2, and HSiCl3, and iii) Reduction of the Si-Cl groups to yield the corresponding -Si-H termini. A series of model compounds mimicking the end-groups have been synthesized and employed for end-group characterization. These Si-Cl and Si-H containing mono- and difunctional polyisobutylenes may be useful intermediates for the preparation of block and graft copolymers or for the synthesis of various terminal functional groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00282687
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  • 4
    Electronic Resource
    Electronic Resource
    New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers) (1981)
    Springer
    Polymer bulletin 4 (1981), S. 445-450 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Novel oxycarbonyl isocyanate telechelic polyisobutylenes have been prepared by conversion of hydroxylterminated polyisobutylenes with N-chlorocarbonyl isocyanate. This reaction is free from side-reactions and provides highly reactive isocyanate-terminated polyisobutylene prepolymers. Conversion of these prepolymers with glycol, urea, pentaerythritol, and polyethylene glycol led to linear chain extension, crosslinking, and multiblock copolymer formation, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00255699
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  • 5
    Electronic Resource
    Electronic Resource
    New telechelic polymers and sequential copolymers by polyfunctionalinitiator-transfer agents (inifers) (1981)
    Springer
    Polymer bulletin 6 (1981), S. 135-141 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary New acryl and methacryl telechelic polyisobutylenes, where R=H or CH3, have been prepared. The syntheses involved reactions between α,ω-di (hydroxy)polyisobutylene, HOCH2-PIB-CH2OH and excess acryloyl or methacryloyl chloride. Model studies coupled with H1 NMR and IR spectroscopic analyses of the products indicate quantitative introduction of two termini per polyisobutylene chain. These prepolymers may be useful for the synthesis of a variety of new composites containing a soft polyisobutylene segment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00956279
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  • 6
    Electronic Resource
    Electronic Resource
    Characterization and degradation of poly(vinyl chloride-g-lsobutylene) carrying tertiary chlorine and cyclopentadienyl branch termini (1981)
    Springer
    Polymer bulletin 6 (1981), S. 155-162 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Poly(vinyl chloride-g-isobutylene)s have been synthetized by using PVC backbones containing relatively high concentration of allylic chlorines [PVC(A)] in conjunction with BCl3 coinitiator. Since graft-termination occurs by ion-collapse, graft copolymers with tertiary chlorine branch termini [PVC(A)-g-PIB-Cl] were formed. The presence of terminal tertiary chlorines has been demonstrated by degradation and cyclopentadienylation experiments. UV-visible spectra of ungrafted and grafted PVC(A) , molecular weight data, and branching frequency as a function of concentration of allylic chlorines indicate chain transfer to polyenes. Thermal and thermooxidative stability of PVC(A) increases upon grafting due to the replacement of allylic chlorines by PIB branches. The introduction of highly oxidizable Cp groups in PVC(A)-g-PIB-Cl by Me2CpAl-treatment decreases the thermooxidative stability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00956282
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  • 7
    Electronic Resource
    Electronic Resource
    Cationic reactions in the melt (1982)
    Springer
    Polymer bulletin 6 (1982), S. 327-333 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The effect of Lewis acids on various ethylene-propylene co- and terpolymers has been investigated in the mixing chamber of a Brabender Plastograph at 180°C. Fast degradation of the polymers was observed upon the addition of Lewis acids. Terpolymers containing unsaturations undergo crosslinking: the structure of the third monomer (diene) determines the rate of crosslinking and the characteristics of the crosslinked materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00255406
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  • 8
    Electronic Resource
    Electronic Resource
    Cationic modifications of polychloroprene (1982)
    Springer
    Polymer bulletin 7 (1982), S. 337-344 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The synthesis of the novel graft-block copolymer poly[chloroprene-g-(isobutylene-b-α-methylstyrene)], i.e., a polychloroprene backbone carrying isobutylene/α-methylstyrene block copolymer branches, is described. The synthesis was accomplished by exploiting detailed insight into the mechanisms of initiation of isobutylene and α-methylstyrene polymerization, and termination of isobutylene polymerization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00254288
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  • 9
    Electronic Resource
    Electronic Resource
    New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers) (1982)
    Springer
    Polymer bulletin 8 (1982), S. 25-32 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Linear and three-arm star tosyl-telechelic polyisobutylenes (i.e., PIB's carrying two and three p-toluene-sulfonic acid ester end groups, respectively) have been synthesized and characterized by a variety of techniques. Subsequently these prepolymers were used as macroinitiators for the ring opening polymerization of 2-methyl-2-oxazoline leading to linear poly(N-acetylethyleneimine-b-isobutylene-b-N-acetylethyleneimine) and three-arm star poly(N-acetylethyleneimine-b-isobutylene). High yields (78–98%) and blocking efficiencies (70–80%) have been obtained. The absence of free polyisobutylene in the product indicates highly efficient initiation of 2-methyl-2-oxazoline polymerization by the tosyl-telechelic polyisobutylene. The less than 100% blocking efficiencies are probably due to chain transfer to 2-methyl-2-oxazoline. Hydrolysis of these block copolymers yielded poly(ethyleneimine-b-isobutylenes).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293558
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  • 10
    Electronic Resource
    Electronic Resource
    New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (Inifers) (1982)
    Springer
    Polymer bulletin 8 (1982), S. 551-555 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary α, ω-Di(hydroxy)polyisobutylene was converted to the corresponding α,ω-di(allylether)- and α,ω-di(allylphthalyl)polyisobutylene by reacting the diol with allyl bromide in the presence of alkali and tetrabutylammonium bisulfate phase transfer catalyst, and monoallyl phthalic acid chloride in the presence of 4-N,N-dimethylaminopyridine, respectively. The reaction conditions were defined by suitable model experiments. IR and 1H-NMR analysis of the reaction products indicates quantitative conversions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262934
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