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  • Polymer and Materials Science  (1,642)
  • Life and Medical Sciences
  • 1995-1999
  • 1965-1969  (1,826)
  • 1967  (1,826)
Collection
Publisher
Years
  • 1995-1999
  • 1965-1969  (1,826)
Year
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 73-84 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Complexes of aluminum alkyls with Lewis bases catalyze the polymerization of vinyl chloride. Triethylaluminum is most effective, but other compounds of type R3Al, R2AlCl, R2AlH, and LiAIR4 are operable. Dialkylmagnesiums are active, but Grignard reagents, as well as a number of other metal alkyls are inactive. Among Lewis bases, tetrahydrofuran (THF) and tetrahydropyran give the best yields of poly(vinyl chloride). Oxygen bases, such as ethers and esters, are more effective than nitrogen bases, e.g., tertiary amines. Cyclic compounds are better than acyclic ones. The polymerization occurs in a variety of hydrocarbon, chlorinated hydrocarbon, or ether solvents, but especially well in CCl4. Radical polymerization is probably initiated through the reaction R3Al:Base + CCl4 → R2AlCl: Base + R + Cl3C., to form trichloromethyl radical.
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  • 2
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 57-71 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Copolymerization of unsaturated polyester with styrene in water-in-oil (W/O) type emulsion was carried out with the use of various basic compounds as emulsifiers. It was found that a stable, gellike W/O type emulsion of unsaturated polyester resin is formed only when pKa's of the bases are above 6 and their concentrations are higher than some critical value. In these conditions, water can be dispersed in emulsion up to 900% to the resin. By polymerization, the stable W/O type emulsion is transformed to a white solid copolymer which is dry to the touch and which contains 90-95% of initially added water. It was confirmed that the basic compounds react with the carboxylic group of the polyester to form at the water-resin interface polyester salts, which act as true emulsifying agents. The stabilization mechanism of the emulsion at various concentrations of the polyester salt was investigated, mainly by microscopic observations, and an interpretation of the critical value of emulsifier concentration is proposed.
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  • 3
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 133-136 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Certain homopolymer-polyol mixtures, after treatment with a free-radical generating agent or ionizing radiation, will produce polyurethane elastomers of nearly twice the stiffness and tensile properties compared to control elastomers made with untreated mixtures. Specific examples of these mixtures include the homopolymers of acrylonitrile and vinyl chloride with a poly(oxypropyl) triol of about 3000 molecular weight as the polyol in each case. The marked improvement in the stiffness and tensile properties of elastomers made with the treated mixtures over those of the untreated controls indicates a grafting process occurring between the polyol and homopolymer upon the generation of free radicals. In the present work, grafting could occur by a chain-transfer hydrogen-abstraction mechanism, whereby a free-radical site is generated on both the homopolymer and polyol chains. Coupling of these two free-radical sites would thus result in the establishment of a polymer-polyol graft bond.
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  • 4
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 115-126 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Graft copolymerization of vinyl monomers, mainly methyl methacrylate, in reduced, successively alkylated, or KCN-Treated wool fibers was performed in the redox LiBr-persulfate system without homopolymer. The reduction gives a striking effect in promoting the graft copolymerization. Methylation or ethylene recrosslinking of the reduced wool, especially the former, decreases the graft-on remarkably. By the KCN treatment in which the conversion of disulfide to lanthionine bonds occurs, the grafting is decreased in the bromide-persulfate system but promoted in the system with persulfate alone. Methylation or KCN treatment of wool as well as reduction brings about a great increase in the absorption of persulfate. The grafting of the lanthionine-containing wool in the redox system accompanied by the liberation of bromine might be retarded by the pronounced bromination of monomers over the inhibiting of homopolymerization, because the lanthionine bonds are more stable to bromine than the disulfide bonds. In general, disulfide bonds and the other easily oxidized components of wool may perhaps play an important role in regulating the bromination of monomers and in the graft copolymerization without homopolymer. The molecular weight of graft polymer is decreased distinctly with increasing extent of reduction of wool. From these results, the thiol groups on wool are considered to give predominantly graft centers by the radicalotropy from SO4-·, OH·, and/or Br·.
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  • 5
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 153-153 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 6
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 357-368 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Previous studies by Black and Blomquist on the degradative failure of polymer-metal adhesive bonds have shown that composite failure depends largely on the type of metal substrate employed. In the work reported herein, metal powders of high surface area have been employed to maximize the metal-polymer interface. The composite systems studied consisted for aluminum and iron with polycondensates of bisphenol A-diglycidyl ether, phenol-formaldehyde and poly-2,2′-(m-phenylene)-5,5′-bibenimidazole. The composites were prepared in the absence of air and thermally degraded in a time-of-flight mass spectrometer while the degradation products were continuously monitored from mass 1 to 200. In the polymer and polymer-metal systems investigated, iron accelerated the decomposition of all polymers studied. This was determined by plotting m/e against degradation temperature for the more common mass peaks such as hydrogen and carbon monoxide for the carbon-hydrogen-oxygen-containing polymer and hydrogen cyanide and ammonia for the carbon-hydrogen-nitrogen-containing polymer. This technique offers promise in determining the nature of the interface as well as the effect of the interface on polymer degradation.
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  • 7
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A study was made of the influence of selected chain modifiers on both the molecular weight of grafted polyacrylonitrile and the grafting frequency of the starch-polyacrylo-nitrile graft copolymer. Gelatinized wheat starch was used with ceric ammonium nitrate as the initiator. The organic chain modifiers investigated were ethyl mercaptan, 1-dodecanethiol, methyl ethyl ketone, acetaldehyde, and chloroform. Sodium chromate, cupric bromide, cupric nitrate, cupric acetate, and cupric chloride were also tested as chain modifiers. In the presence of cupric chloride, there was a tenfold reduction in the molecular weight of grafted polyacrylonitrile; however, fewer chains were grafted to the starch backbone than were observed without cupric chloride.
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  • 8
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    Journal of Applied Polymer Science 11 (1967), S. 475-478 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 9
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    Journal of Applied Polymer Science 11 (1967), S. 499-514 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The supermolecular structure of mixtures of crystalline polymers (low pressure and high pressure polyethylene, isotactic polypropylene) with an amorphous polymer (atactic polypropylene) from the point of view of the influence of the amorphous component on the morphology of the crystalline component has been investigated. The criterion of changes in the morphological state of larger supermolecular formations was the microscopic image of the samples obtained with an optical microscope, both between crossed nicols and in phase contrast. It has been established that the formation of typical spherulites depends on the amount of admixture of the amorphous polymer and also on the treatment of the samples. Upon crystallization in presence of a small amount of solvent (p-xylene), formation of typical spherulites of the crystalline component of the mixture can be observed while the same mixture in case of evaporation of the solvent presents a granulated refractive structure without typical spherulites, regardless of the rate of cooling. The probable role of the solvent is to facilitate mutual segregation of the microphases of both polymers in consequence of decrease in viscosity of the mixture. It has been further shown that even after briefly heating the mixture to a temperature of 220°C., before crystallization, spherulites do not form; on the contrary, spherulites originally present disappear and a structure consisting of smaller refractive formations of crystalline polymer is obtained. The formation of this structure, emerging after destruction of spherulites, might be attributed to an increase of interpenetration of both polymers and to an increase of the contact surfaces between components of the mixture.
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  • 10
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An experimental assembly incorporating a capacitance-type, differential pressure transducer, which provides resolutions of 3 × 10-4 torr at pressures extending to 30 torr, has been employed to monitor the effect of hydrogen environmental pressure on the hydrogen yield from x-irradiated polyethylenes. Contrary to the observations of previous investigators, the hydrogen yield is found to be independent of hydrogen environmental pressures extending over the critical range up to at least 30 torr. It is demonstrated that neglecting the temperature and density gradients inherent in closed-volume irradiation assemblies employing cryogenic traps to separate liberated gases into condensable and noncondensable fractions may lead to erroneous conclusions with respect to gas yields arising from the irradiation of materials. A homogeneous, variable-plate separation ion chamber consisting of a polyethylene body and utilizing flowing ethylene as the cavity gas was employed to obtain total volatile G values of 3.6 ± 0.4, 3.8 ± 0.4, and 4.0 ± 0.4 molecules/100 e.v., for Marlex 6002, Dow Ziegler (Q 917.5), and DuPont A-1410 polyethylenes, respectively. A hydrogen contribution of approximately 98 mole-% was obtained with this experimental method.
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  • 11
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    Journal of Applied Polymer Science 11 (1967), S. 601-602 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 12
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 629-638 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Castor oil has been used to prepare millable elastomers by using 2,4-toluene diisocyanate, 4,4′-diphenylmethane diisocyanate, and 1,5-naphthalene diisocyanate, respectively. These elastomers are vulcanized with sulfur and 4,4′-diphenylmethane diisocyanate separately by using the standard methods of rubber technology, and the properties of these vulcanizates are reported.
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  • 13
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 673-685 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A model nucleating agent for polypropylene crystallization is described. A series of compounds consisting mainly of organocarboxylic acid salts is evaluated as heterogeneous nucleating agent for polypropylene crystallization by measuring their effect upon the polymer supercooling. Sodium benzoate and basic aluminium dibenzoate were among the best nucleating agents found. The nucleating abilities of the various compounds are discussed in terms of their structural features.
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  • 14
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 705-718 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We have shown by two separate measurements that polypropylene when melted after irradiation undergoes crosslinking from the inception of irradiation. The first proof was an immediate increase in the solution viscosity of a narrow molecular weight fraction of polypropylene. The second proof was the marked change in melt-flow properties on irradiation of a broad molecular weight distribution polypropylene. These findings tend to support one of the two currently held views on the action of radiation on polypropylene. In addition we have confirmed previous reports that melting after irradiation contributes to the overall crosslinking reaction.
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  • 15
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    Journal of Applied Polymer Science 11 (1967), S. 751-751 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 16
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    Journal of Applied Polymer Science 11 (1967), S. 811-815 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The preparation of polyisocyanurates by the polytrimerization of isocyanate prepolymers in the presence of organometallic catalysts leads to an increase in adhesive strength at 400°F. for bonding aluminum-to-aluminum. The trimerization efficiency of several other catalysts is briefly described.
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  • 17
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    Journal of Applied Polymer Science 11 (1967), S. 1283-1288 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dry mixtures of starch with various bases were roasted in air. The effects of roasting were determined by a viscosity method. The results suggest that roasting at alkaline pH's produces covalent crosslinks. The author speculates that the crosslinks result from a combination of autoxidation and aldolization.
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  • 18
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    Journal of Applied Polymer Science 11 (1967), S. 1333-1343 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Five examples are discussed showing how gel permeation chromatography was applied to studies of polymer systems. The calculation of molecular weights from the curves was not pertinent to the studies. The only requirement was that the seperation be a size separation and the results be reproducible.
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  • 19
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    Journal of Applied Polymer Science 11 (1967), S. 1387-1407 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A heterogeneous cellulose reaction was studied by reacting cotton fiber in pyridine medium with propionyl chloride at different initial molar concentrations and at different temperatures. It has been observed that the kinetics of reaction does not follow Sakurada's diffusion equation closely, and the deviation is more noticeable at lower initial concentrations of the reagent and at lower temperatures. A non-uniform reaction rate is also evident from the time-substitution curve. The rate of substitution changes twice during the reaction, the latter change being associated with the loss of cellulose I crystal structure. In an attempt to treat the data according to simple chemical kinetics, the order has been found to decrease continuously from the beginning, suggesting thereby an autocatalytic type of behavior. However, at the finàl stages of the reaction, when the cellulose I structure was completely lost, the reaction behaved as a pseudo first-order type. The x-ray diffractograms of the reacted samples indicate that cellulose I crystallinity decreases from the beginning of the reaction and that a new crystalline lattice develops gradually. The formation of this new crystal lattice is hindered in the cellulose crystalline region due to the lack of freedom of the chains. The diffusion equation has been modified by substituting a crystallinity index for the rate of diffusion of solvent in a solvent-gel system and thus extending Sakurada's equation. A new mechanism has been proposed considering the simultaneous reactions in the amorphous and crystalline regions. This mechanism can explain the deviation of Sakurada's equation. The kinetics expressions are derived, based on the proposed mechanism. The kinetics of decrystallization of cellulose I is also presented. A satisfactory theoretical explanation is given for the fact that the fall of reaction rate occurs at the conclusion of decrystallization of the cellulose I structure.
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  • 20
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    Journal of Applied Polymer Science 11 (1967), S. 1439-1448 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: It is shown that the glass temperature (Tg) for homopolymers of the type —CH2—CXY—can be expressed by a simple additive equation involving two terms: (1) a parameter E which is directly related to the molar cohesion energy and (2) a parameter Es* which is a measure of restricted rotation about valence bonds. Es*, at least for a large number of polymers, is related to the Mark-Houwink Kθ value (as measured in θ solvents at Tθ) via anti-log Es* ∝ 1/Kθ2/3. It is also shown that for homologous series [e.g., poly(n-alkyl methacrylates)], there is a constant relationship between E and antilog Es*. The Tg values for copolymers may be estimated by a simple weighted (via mole fraction) summation of the E and Es* values of the components. When used in this form, a linear variation between Tg and composition is assumed, which may not be strictly correct but still yields useful approximations.
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  • 21
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    Journal of Applied Polymer Science 11 (1967), S. 1483-1494 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Lattice spacings perpendicular to the molecular chain axes and crystallite orientation of dried and moist (boiled in water) bulk nylon 6 were determined by x-ray diffraction under tension of 30-300 kg./cm.2. The deformation of the specimen was also measured. The lattice spacings are changed reversibly by the presence of water in nylon 6, but the elastic moduli of the lattice are not affected. The lattice elastic modulus in the direction of the hydrogen bonds is approximately double its value in the direction normal to the hydrogen bonds. The elastic modulus of the dried nylon 6 approaches the value of the lattice elastic modulus in the direction normal to the molecular axes, while the modulus of the moist nylon 6 is several times lower. From these facts, and especially from the relations between the lattice deformation, crystallite orientation, and specimen deformation, the principal differences in the deformation mechanism of dried and moist nylon 6 were deduced. The results obtained have also made possible some general conclusions about the crystalline structure of nylon 6 and the deformation mechanism of linear polymers.
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  • 22
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    Journal of Applied Polymer Science 11 (1967), S. 1529-1538 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Graft copolymerization of methyl methacrylate and acrylamide onto ovalbumin was carried out with redox system with ceric ion. Initiation of grafting occurred very rapidly, and the number of grafting sites reached a maximum after about 2 min. regardless of initial ceric ion concentration. The grafted polymer chains were separated by selective hydrolysis of the protein backbone with hydrochloric acid or protease in order to characterize the graft copolymers. The grafted polyacrylamide separated by the proteolytic digestion contained a carbohydrate residue at the end of the polymer molecule. The problem of grafting sites on ovalbumin is discussed.
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  • 23
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    Journal of Applied Polymer Science 11 (1967), S. 1553-1562 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A process for adhering polyethylene to aluminum was developed which involves treating the aluminium substrate successively with chromic acid and then a selected organic acid. Certain organic acids utilized in this process appeared to produce a synergistic effect on the adhesion. This process, which required no modification or treatment of the polymer, resulted in peel strengths forty times greater than that obtained on untreated aluminum. Tensile shear values for the polyethylene-aluminum bond were greater than 2800 psi. The materials used for treating the metal in this system produced a maximum in the obtainable peel strength. Furthermore, minor changes in the etching acids resulted in drastic changes in the adhesion values.
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  • 24
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    Journal of Applied Polymer Science 11 (1967), S. 1613-1615 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A relatively simple and inexpensive automatic apparatus for chemical relaxation giving good accuracy has been developed for measurement of chemical relaxation in the gaseous phase in high polymers. The apparatus is based on a previously described balance-type stress relaxation apparatus intended for automatic operation.
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  • 25
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    Journal of Applied Polymer Science 11 (1967), S. 1581-1591 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of monomer sequence on physical properties was investigated for butadienestyrene solution copolymers made by organolithium initiation. The polymers varied from random copolymers of uniform composition along the polymer chain to ideal block polymers of specific block sequence arrangement and included rubbers of intermediate degrees of randomness. Uniform composition random copolymers exhibit a single glass transition temperature and a very narrow dynamic loss peak corresponding to this transition. The glass transition can be predicted from the styrene content and the microstructure of the butadiene portion of the rubber. Random copolymers in which composition varies along the polymer chain, and to some extent between molecules, exhibit a single glass transition, but the dynamic loss peak is broadened. The extent of this broadening is shown to be compatible with the sequence distribution, polymer segments of various compositions losing mobility at different temperatures. This indicates a tendency for association between segments of different temperatures. This indicates a tendency for association between segments of different chains which are similar in composition. Block copolymers display two transitions, corresponding to Tg for each type of block. The position and width of the dynamic loss peaks are related to block length and compositional purity of the blocks.
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  • 26
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    Journal of Applied Polymer Science 11 (1967), S. 921-924 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A simple, inexpensive microtome was developed for sectioning polystyrene foam prepuff. The cell structure is well defined and wall thicknesses can be measured easily from photomicrographs prepared with the microtome.
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  • 27
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    Journal of Applied Polymer Science 11 (1967), S. 925-947 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The applicability of Miner's law of cumulative damage to predict lifetimes in experiments involving complex load histories is examined. Lifetimes estimated by Σ ti/(tb)i = 1 are compared with those calculated by the expression for the time to rupture derived by Prevorsek and Lyons assuming that the time to rupture can be approximated by the time to form an unstable crack. For experiments in which the loading conditions became increasingly severe with time, lifetimes predicted by Miner's law are longer than those calculated from the rate of crack propagation, the opposite being found for experiments in which the loading conditions become decreasingly severe with time. Experimental data on hand are in agreement with these findings. Effects of changes in the structural parameters ρ, E, and ΔF* and of variations in the experimental conditions on the accuracy of the lifetime estimates are discussed.
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  • 28
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    Journal of Applied Polymer Science 11 (1967), S. 23-36 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The adduct of Kaolin and 2,2′-azobisisobutyramidine hydrochloride has been used to initiate the polymerization of methyl methacrylate, styrene, styrene-butadiene, vinyl acetate, chloroprene, acrylamide, and acrylonitrile. Both extractable and nonextractable polymers are obtained. The adduct of bentonite and 2,2′-azobisisobutyramidine hydrochloride will initiate the polymerization of methyl methacrylate, acrylamide, vinyl acetate, 4-vinylpridine, and styrene. Both extractable and nonextractable polymers are formed. When the bentonite or the hectorite adducts are more than 99% decomposed prior to the addition of methyl methacrylate, essentially no extractable polymer is formed, but an increased quantity of nonextractable polymer is produced. This is probably due to an increased accessibility of the monomer to the clay's interior surface and a decrease in the rate of chain termination. As is the case of the kaolin adduct, the clay surface of bentonite appears to accelerate the chain growth considerably.
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  • 29
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    Journal of Applied Polymer Science 11 (1967), S. 37-55 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A quantitative characterization of natural rubber, both as the raw polymer, and unaccelerated vulcanized samples containing different proportions of sulfur and ranging from soft to hard rubber, is reported. A value of 86% of the chains of natural rubber could be accounted for against 37% as reported by Harries assuming that levulinic acid is the sole degradation product. About 5% of the chain is present as a 3,4 structure which gives rise to formic acid in the degraded product. A small amount of sulfuric acid is present in the degradation product from the vulcanized samples, which decreases with the increases in the percentage of sulfur in the stock as well as the cure time. A chromatographic technique for the separation of levulinic, acetic, and formic acid in the presence of sulfuric acid is reported. It is observed that the total amount of carbon main chain escaping sulfuration decreases and the amount of insoluble fraction increases with increasing proportion of sulfur in the stock.
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  • 30
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    Journal of Applied Polymer Science 11 (1967), S. 773-790 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polyacrylonitrile-β-propiolactone (βPL) graft copolymer was synthesized by means of ionic polymerization, in which polymerization of βPL was initiated by polyacrylonitrile containing a small amount of some reactive groups such as —COOK, —COONa, —COOLi, and —COOH. Lower electronegativity of the countercation favored higher total conversion and higher grafting percentage. The grafting percentage increased with the reaction time and concentration of reactive groups in the trunk polymer, but grafting efficiency varied very little under these conditions. In the bulk polymerization at 60°C., grafting efficiency was about 60%, but in the solution polymerization in toluene or dioxane, grafting efficiency was higher than in bulk or nitrobenzene.
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  • 31
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    Journal of Applied Polymer Science 11 (1967), S. 791-810 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polyacrylonitrile (PAN)-β-propiolactone (βPL) graft copolymer was synthesized by means of the ionic polymerization of βPL in the presence of polyacrylonitrile containing diketene units by using basic catalysts. A graft copolymer was produced by the copolymerization of βPL with the lactone ring in the trunk polymer. In this graft copolymerization method, the grafting efficiency was low. However, grafting efficiency increased with the mole ratio of polymeric lactone to βPL; also higher molecular weight of PβPL favored higher grafting efficiency. The reactivity ratio of polymeric lactone to βPL was estimated to be in the range of 0.1-0.3.
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  • 32
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    Journal of Applied Polymer Science 11 (1967), S. 839-858 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The radiation-induced grafting to cellulose of styrene, methyl methacrylate, vinyl acetate, 2-vinylpyridine, and 4-vinylpyridine in methanol has been studied. All monomers exhibit appreciable grafting at room temperature in either vacuum or air for total doses up to 10 Mrad and at dose rates as high as 1.4 Mrad/hr. in a spent fuel or 60Co facility. The magnitude of the grafting depends upon both the total dose and dose rate. Under certain experimental conditions, the grafting experiences a maximum which has been attributed to the Trommsdorff effect. A novel mechanism involving charge-transfer bond formation is proposed to account for the observed data in the grafting reactions.
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  • 33
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    Journal of Polymer Science: Macromolecular Reviews 1 (1967), S. 119-172 
    ISSN: 0076-2083
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 34
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    Journal of Polymer Science: Macromolecular Reviews 1 (1967), S. 173-275 
    ISSN: 0076-2083
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 35
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    Journal of Polymer Science: Macromolecular Reviews 2 (1967), S. 115-268 
    ISSN: 0076-2083
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 36
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    Journal of Morphology 121 (1967) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 37
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    Journal of Morphology 121 (1967), S. 55-70 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Light and electron microscopical studies allow a descriptive account to be given of he morphogenesis of the egg chamber of Drosophila melanogaster. The study demonstrates that the mitotic products of a single cystoblast generate a branching chain of 16 inter-connected cystocytes. Two specific cystocytes enter meiotic prophase, while the rest become nurse cells. The two pro-oocytes form synaptinemal complexes in their nuclei. However, one of the two cells later switches back into the nurse cell developmental pathway. The elongation of the synaptinemal complexes is described, and estimates are made of the time involved in their formation. These complexes continue to be synthesized long after the DNA replication which gives the oocyte its 4C DNA content. This finding implies that at least some genetic crossing over follows DNA replication. Evidence is presented that cells undergoing crossing over are most efficient in repairing radiation-induced chromosomal breaks. Suggestions are given as to the mechanisms by which (1) cell division is inhibited once 16 cystocytes are formed, (2) the future cleavage planes of cystocytes are programmed, (3) the pro-oocytes are differentiated from nurse cells, and (4) the oocyte is chosen from the twin pro-oocytes. The contrasting behaviors of the oocyte and nurse cell nucleoli are described. During oogenesis nucleolar synthesis of ribosomal RNAs is suppressed in the oocyte and concurrently stimulated in the nurse cells. It follows that the nurse nuclei are the major sources of the prodigious quantities of ribosomes found in the ooplasm of the mature oocyte.
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  • 38
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: The enigmatic lophophoral organs of phoronids are demonstrated to by accessory sex glands. In the hermaphroditic Phoronis vancouverensis, each mature adult has two pairs of such glands: female nidamental glands that facilitate the temporary brooding of the embryos and male accessory spermatophoral organs that function in spermatophore elaboration. Functional males of Phoronopsis harmeri have complex accessory spermatophoral organs while females of this non-brooding dioecious species lack accessory sex glands.In both species, coelomic spermatozoa are accumulated within the nephridia and passed en masse into the partially enclosed spermatophoral organs. There each sperm mass is molded into a characteristic shape and encased in one or more membranes before release as a spermatophore into the ambient water. The structure of the spermatophore is characteristic for each species and is correlated with the functional morphology of the distinctive spermatophoral organs.The existence of spermatophores, the non-primitive nature of the spermatozoa, and additional features of reproductive biology dictate that fertilization is internal in these species, but attempts to determine the means of sperm transfer proved futile. Reproductive potential and behaviour of male Phoronopsis, means of gamete segregation in Phoronis, and general pattern of reproductive biology for both phoronids were also studied.
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  • 39
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    Journal of Morphology 121 (1967), S. 241-254 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The middle ear and the cochlea have been described in 20 representatives from the superfamily Phyllostomatoidea of the suborder Microchiroptera. Various measurements have been made and the results compared by means of graphs. The ultrasonic pulses used by these bats for echolocation have been recorded and analysed. Generally, the structure of the cochlea does not show extreme modifications as found in some other superfamilies that have previously been discussed.
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  • 40
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: The study of the ultrastructure of the kidney tubules of the crocodile was made to compare the cellular structure with the capacity for electrolyte resorption and the ability to create an osmotic gradient across the tubular wall. The crocodile tubular cells were found to differ from the mammalian tubular cells in that they do not have basal infoldings, but instead have open lateral spaces between the cells, similar in many aspects to those found in the mammalian gallbladder. The physiological role of these lateral spaces in solute and fluid transfer is discussed.
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  • 41
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: In order to follow the movement of cells involved in the proliferative response induced by wounding, changes in the cell population of three regions of normal and injured frog lens epithelium were studied with respect to DNA synthesis and mitosis using autoradiography following intraperitoneal injection of H-3-thymidine. The injured lenses comprised two groups: one subjected to labeled thymidine at 40 hours post-injury when the proliferative response begins, the other at 72 hours when the proliferative response is at its peak. Lenses were fixed at increasing intervals after injection.The data show that a central injury initiates proliferation in a large number of cells; this response appears at first mainly among the cells in the outlying proliferative (pre-equatorial) zone, as judged by the number of labeled nuclei and mitoses seen there in the first few hours after injection in the 40 hour preparations. At later intervals labeled cells and mitoses appear centrally adjacent to the wound. And in the 72 hour preparations, the greatest concentration of reactive cells is adjacent to the wound. There is also thinning out of labeled cells in the proliferative zone and greater dilution of exposed emulsion grains over nuclei adjacent to the wound with time, suggesting that outlying cells migrate centrally, dividing en route. However, interpretation of these data is limited by the finding that H-3-thymidine injected intraperitoneally into the frog is not cleared rapidly from the circulation; the serum after 24 hours retains about 20% of the radioactivity (measured by scintillation counting) present at 15 minutes post-injection.
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  • 42
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: In this study, the condensation of the three thoracic and 11 abdominal segmental ganglia to form a prothoracic and central nerve mass during embryogenesis is described. During katatrepsis, many changes occur in the organization of these ganglia; this study suggests that some of these changes are caused by mechanical forces acting on the ventral nerve cord at this time. The ventral nerve cord begins its anterior migration and coalescence ten hours after katatrepsis and is completed 63 hours later. The central ganglion is made up of the meso- and metathoracic ganglia and seven abdominal ganglia. Intrasegmental median cord nuclei are shown to form glial elements in the median sagittal plane of the neuropile and in the longitudinal connectives. Intersegmental median cord neuroblasts migrate into the posterior gangliomeres but, apparently, degenerate soon after katatrepsis. Lateral cord cells bordering on the neuropile form a glial investment that surrounds this fiber tract region. Peripheral lateral cord cells are shown to form the cells of the outer ganglionic sheath, the perineurium.
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  • 43
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    Journal of Morphology 122 (1967) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 44
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: Five types of sense organs have been found on the antennal flagellum of Forficula auricularia Linnaeus: (1) tactile hairs; (2) long, thick-walled chemoreceptors; (3) short, thick-walled chemoreceptors; (4) thin-walled chemoreceptors and (5) coeloconic chemoreceptors. Earlier workers have placed the first three of these in a single class. The structural characteristics and distribution of these five kinds of sensilla on the antenna are described. All of the types except the third have been reported previously for other species but short, thick-walled chemoreceptors have not been described before. They are remarkable for the presence of (1) a broad pad-Like structure that absorbs dyes readily at the distal end of the peg and (2) a spheroid body, over a micron in diameter, on the dendrite of each olfactory neuron at the point where it narrows to assume the structure of a cilium. The antennal sense organs of a few specimens of Chelisoches morio (Fabricius), Labidura riparia (Pallas) and Euborellia annulipes (Lucas) were also examined.
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  • 45
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    Journal of Morphology 122 (1967), S. 115-130 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The origin of the internal carotid artery in the lizards Tiliqua occipitalis and Trachysaurus rugosus has been shown to be both extremely variable and complex. In the dense connective tissue investing the junction of the internal carotid artery and the summit of the carotid arch are groups of cells associated with sinusoids derved from arterioles arising from the neighboring great vessels. The conspicuous epithelioid cells in these groups resemble the mammalian carotid body glomus and amphibian α cells. Nerve fibers showing no obvious synaptic specializations pass to and over these cell groups. It is suggested that these cell groups and sinusoids are comparable to mammalian carotid body glomeruli. A similar group of cells has been described in the concavity of the summit of the fourth aortic arch. This cell group, however, gives a distinct chromaffin reaction.
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  • 46
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    Journal of Morphology 121 (1967) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 47
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    Journal of Morphology 121 (1967), S. 179-207 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Detailed descriptions are presented of morphogenetic and histogenetic events occurring in the membranous and bony labyrinths, sensory areas, acoustic ganglia, and acoustic centers of the hindbrain of the chick embryo, stages 11 to 45. Major morphogenetic changes occur between stage 11 and stage 30. During this period primordial ganglionic neuroblasts are segregated from the otic epithelium and differentiate into the bipolar neuroblasts of the vestibular and cochlear ganglia, neuroblasts of the alar plate in the acoustic region of the rhombencephalon differentiate, migrate, and are organized into acoustic nuclei, and the otic cup closes to form a vesicle which undergoes complicated structural changes to become a labyrinth. Morphological events in neural structures are closely followed by structural changes in the labyrinth. Minor morphological changes continue to occur through stage 44. The histogenetic period, stage 26 to 38, is the same for all parts of the acoustic apparatus. Minor histogenetic events occur up to hatching. In this period, differentiation of ganglionic and central neurones precedes differentiation of sensory cells.
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  • 48
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    Journal of Morphology 122 (1967), S. 19-33 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ovary in Callosobruchus analis consists of telotrophic ovarioles with the so called nurse cells confined to one chamber at the anterior end of the ovariole. There are three types of lipids in the ovary: (1) L1 bodies that are present in the early oocytes, in the posterior prefollicular tissue and in the follicular epithelium and contain unsaturated phospholipids; (2) L2 bodies that have a complete or incomplete sheath of phospholipids and a triglyceride core; (3) L3 bodies that are formed of highly saturated triglycerides. Lipids are absent from the trophic tissue. In a mature oocyte the L1 and L2 bodies are cortical in distribution while the L3 bodies are centrally located.The mitochondria contain lipoproteins with RNA. The yolk spheres are acid mucopolysaccharides and protein in nature. The precursors of the yolk spheres appear first in the cortical coplasm and are absent from the follicular epithelium or the trophic tissue. The nucleolus of the oocyte shows evidence of extrusions that are believed to pass into the ooplasm.There are no nutritive cords connecting the trophic tissue to the oocytes; nor is there any evidence of any histochemically demonstrable nutritive material being contributed to the oocyte by the trophic tissue. The circumstantial evidence points towards a contribution of the raw materials to the oocyte by the haemolymph either through or in between the follicular epithelium in some soluble form or as submicroscopic particles.
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  • 49
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    Topics: Biology , Medicine
    Notes: Parenteral administration of methylcellulose causes massive splenomegaly and hemolytic anemia in rats. The red pulp of the spleen is markedly cellular due mainly to: (1) large numbers of voluminous free macrophages containing methylcellulose-induced vacuoles, (2) an increase in the number of plasma cells and (3) stasis of blood evidenced by a large number of erythrocytes and platelets in vessels, sinuses and cords. White pulp changes are usually less marked. Here the major change is the presence of macrophages containing methylcellulose-induced inclusions. The slow circulatory time in the spleen and the increase in macrophages may cause the hemolytic anemia observed in these animals.
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  • 50
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    Topics: Biology , Medicine
    Notes: The squirrel monkey uterine cervix was studied macroscopically and microscopically in intact and ovariectomized monkeys. The effect in ovariectomized monkeys of estradiol dipropionate or progesterone of both given after estrogen priming was studied by PAS staining.The lower portion of the cervix was dilated to form a vestibule into which projected fibromuscular colliculi which arose from the isthmic end of the cervix. The stratified squamous epithelium of the vagina was continuous through the external os with a similar epithelium lining the vestibule and covering the external surfaces of the colliculi. The transitional zone between the stratified epithelium and columnar cells was variable. The colliculi were covered internally with mucosal folds of columnar epithelium continuous with those of the endocervical canal.Glycogen concentration in the smooth muscle did not fluctuate markedly, irrespective of the hormones used. Glycogen granules were more numerous in the stratified squamous epithelium. Malt-diastase-resistant material appeared to be more abundant in the columnar epithelium and glandular lumina when the monkeys received both hormones than when they received solely estrogen or progesterone.
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  • 51
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: A detailed gross anatomical study of the innervation of the respiratory muscles was made on twenty mature, male, Single Comb White Leghorn chickens. The aim was to demonstrate the general pattern and degree of terminal branching of the intercostal and lumbar nerves that innervate respiratory muscles.The point of entry for all nerves was on the medial face of the proximal third of the belly of the muscles, except for the transversus abdominis and costopulmonary muscles. The nerves were not always accompanied by blood vessels at the point of entry but both were invariably related at their terminal branches within the muscle belly and the tendon or aponeurosis. Within the muscle, primary, secondary, tertiary, and quarternary subdivisions of nerves coursed parallel to the muscle fibers, but some were tortuous. Plexus formation and/or segmental nerve anastomosis was most evident in strongly active expiratory and inspiratory muscles, i.e., all abdominal muscles and the m. costisternalis pars major.A craniocaudal gradient in the size and development of the contractile mass of the intercostal muscles was observed. The mm. intercostales interni increased in size in the caudal intercostal spaces, while the reverse was true for the mm. intercostales externi. Variable forms and sizes of lateroventral abdominal muscles were observed and the m. rectus abdominis was consistently present.The mm. intercostales interni and externi received branches from both the nn. intercostales interni and externi.
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  • 52
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    Journal of Morphology 123 (1967), S. 71-83 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ctenophore, Vallicula multiformis (V. multiformis) (Rankin), can reproduce asexully by segregating pieces of tissue from its periphery. These pieces of tissue then differentiate to form new individuals. In 99% of the cases the pieces of tissue form normal animals; however in 1% of the cases they form “half animals” which have only one set of tentacles (the animal normally has two sets of tentacles). V. multiformis can also regenerate its apical organ, and one or both sets of tentacles.By cutting V. multiformis in half through the apical organ along the sagittal plane it is possible to produce “half animals” in 30% of the cases. “Half animals” can reproduce asexually. In 6% of the cases the new individuals which form from them differentiate as “half animals.” A part of a “half animal” that contains an apical organ will regenerate as a “half animal” while a part that does not contain an apical organ will regenerate as a normal individual. If one removes the apical organ from a “half animal,” it will regenerate it. A part of this animal containing the regenerated apical organ will regenerate as a “half animal.” If one removes the apical organ from a “half animal” and replaces it with the apical organ of a normal individual, the part containing the apical organ will regenerate as a normal individual. The results of these experiments are discussed in terms of possible mechanisms that control the process of regeneration.
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  • 53
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: The venom glands of several species of elapid snakes are described. The main venom gland consists of many tubules which usually contain large amounts of secretion product. The accessory gland surrounds the entire venom duct and is usually composed of uniform mucous epithelium. The epithelium lining the tubules of the accessory gland of Naja naja is composed of two distinct types of cells. Histochemical tests indicate that the main venom gland reacts with mercury bromphenol blue and PAS but not with alcian blue. The accessory gland reacts with PAS and alcian blue, and not with mercury bromphenol blue. Treatment of sections with sialidase demonstrates the presence of a sialomucin in the accessory gland. Stimulation of the muscles associated with the venom gland offers an indication of the venom expulsion mechanism of Bungarus caeruleus. A comparison of the venom apparatus of elapid and viperid snakes emphasizes marked differences in the internal anatomy of the venom glands, muscles associated with the gland, and arrangement of glandular components. The morphological differences and dissimilar venom expulsion mechanisms support the recent view of the polyphyletic origin of venomous snakes.
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  • 54
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    Journal of Morphology 123 (1967), S. 441-461 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: An electron microscopic study of the functional mesonephros in the 8-day chick embryo revealed the following features of the nephron:Proximal tubule cells. Nuclei are spherical and basally oriented. Mitochondri are round or elongate with clear-cut cristae. Intramitochondrial granules occur sporadically. The Golgi complex, lying adjacent to the nucleus in apical cytoplasm, consists of flattened lamellae and associated secretion droplets. The cytoplasm is filled with ribosomes which occasionally are spiral in arrangement. Characteristic microvilli project from the apical end of cells. Basal regions of the cells are bounded by a homogeneous basement membrane. Adjacent epithelial cells are separated at their base by wide intercellular spaces. Interdigitating processes between cells are common in this area. At their apices, cells are joined by junctional complexes.Distal tubule cells. Nuclei are round and centrally located. Microvilli are sparse and usually absent. When present, they are short and blunt. Cells are closely allied at their base and joined tightly at their apices. Interdigitating processes are not as prevalent as in proximal tubules. Infoldings of the plasma membrane are prominent and compartmentalize mitochondria.Glomerulus. Endothelial cells are elongate, bordering the capillary lumen, and their membranes contain definite slit-pores. Epithelial pedicels extend from the cell body, intergiditate with each other and rest on the capillary basement membrane. The latter consists of three layers resembling those in adults.The similarity in the fine structural characteristics between chick mesonephros and adult metanepros corroborates the holonephric theory of vertebrate kidney evolution.
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  • 55
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The forms of the tectorial membrane and its connections to the ciliary tufts of the hair cells have been studied in detail in 18 species of lizards and, less thoroughly, in three others. This group, which represents eight lizard families, exhibits three forms of tectorial membrane: a complete form that connects to all parts of the auditory papilla, an abbreviated form that makes this connection only in one limited region of the papilla, and a dendritic form in which the distal portion of the membrane subdivides into strands reaching all the hair cells.Sometimes the tectorial membrane connects directly with the tufts of the hair cells, but more often it makes this connection through intermediary structures. Seven types of such intermediary structures have been identified (if we include the sallet, which is not “intermediate” in a strict sense).Detailed descriptions are given of the various forms of tectorial membrane structures and their variations along the auditory papilla in 12 lizard species. The description for Iguana iguana is offered as representative of the iguanid pattern found in ten members of this family.Consideration is given to the functioning of the tectorial membrane, and also of the sallet, in the process of hair-cell stimulation.
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  • 56
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: There were no lymphatic vessels and lymph nodes demonstrable in adult and larval Rana catesbeiana by a method that adequately demonstrated the same in mammals. Although the parenchymal arrangement in the lymphomyeloid organs is not exactly the same as in mammalian hemal nodes, nonetheless the vascular patterns of the lymph glands and jugular bodies are prima facie evidence that they function as blood-filtering organs among other probable functions. The vascular pattern of the lymph gland is that of a rete mirabile, particularly a venous portal system, inasmuch as the afferent and efferent vessels are venous in character and interposed between them is a labyrinth of sinusoids. This is not the case, though, in the adult organs. The vascular pattern of the jugular bodies is very much like the spleen, viz., artery-capillary-sinusoid-vein sequence. It is doubtful, however, if the propericardial and procoracoid bodies ever filter blood, because the smallest blood vessels in them are capillary in type Because of the absence of a well-defined capsule in some parts of the propericardial body, similarly to lymphoid follicles, especially in the mammalian gastrointestinal tract, it is probable that it filters tissue fluid. The last two organs are apparently mainly blood cell-forming organs. It is inferred from the vascular connections of the larval and the adult lymphomyeloid organs that they are not genetically related. This aspect was analyzed from earlier developmental data, but actual follow-up of the larval organs to the adult stage is still in progress.
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  • 57
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1327-1328 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
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  • 58
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 23-35 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyacrylamide having a fluorescent residue at the chain end was prepared by polymerization of acrylamide in the presence of a fluorescent dye. The segmental motion of the chain end in dilute solution was studied by the fluorescence polarization method on the fluorescent polyacrylamide conjugates thus obtained. The linear relation between 1/p and T/η0 held for every sample studied in aqueous media, where p is the degree of polarization of the fluorescence, T is the absolute temperature, and η0 is the viscosity of the medium. The mean relaxation time 〈ρ〉 of the conjugate was evaluated from these data as a function of the molecular weight of the conjugate. The value of 〈ρ〉 increased slightly with molecular weight, varying from 3.3 × 10-9 to 7 × 10-9 sec. The absolute values of 〈ρ〉 and its molecular weight dependence suggest that 〈ρ〉 represents the mean rotational relaxation time for the cooperative motion of about ten monomeric units at the chain end. The effect of the mean extension of polymer chain on the segmental motion was found to be negligible.
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  • 59
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 37-45 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The fluorescence polarization method has been used to study the micro-Brownian motion of a terminal segement of a polymer chain in concentrated solutions. A new apparatus for determining the fluorescence intensity and its polarization degree was designed. By using this apparatus, the rotational relaxation time 〈ρ〉 of the terminal segment of the fluorescent conjugates of polyacrylamide in aqueous polyacrylamide solutions was obtained as a function of polymer concentration from 0 to 65%, molecular weight of the conjugate from 3.5 × 104 to 3 × 105, and temperature from 10 to 30°C. The logarithm of 〈ρ〉 increased approximately linearly with increasing polymer concentration. This increase in 〈ρ〉, amounting to a factor of 20 times, was less marked than that in macroscopic viscosity. At concentrations less than 30%, 〈ρ〉 depended appreciably on the molecular weight of the conjugate.
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  • 60
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 47-61 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyethylene networks were prepared by γ-irradiation of linear polyethylene, both molten and crystalline. The elastic and photoelastic properties of the networks were studied at high temperatures, i.e., in the molten state. The equilibrium swelling was also measured in several solvents. Values of the crosslinking efficiency G of γ-radiation, the molecular, weight Me between entanglements, the optical anisotropy α of the equivalent random link, and the polymer-solvent interaction parameter μ are deduced. Samples prepared by irradiation in the amorphous state showed markedly non-Gaussian elastic behavior. The presence of a large non-Gaussian term in the optical anisotropy is also deduced. The value of α obtained for swollen samples, which showed substantially Gaussian elastic behavior, was 3.9 × 10-24 cm.3, about one-half of that obtained for dry samples. It corresponds to an equivalent random link of only about 5 CH2 units, on the basis of Denbigh's values for bond polarizabilities. The samples prepared by irradiation in the crystalline state showed lower values for α, which also depended upon the degree of crosslinking. This is attributed to the nonrandom chain configurations prevailing at the time of crosslinking. The same samples were found to show more nearly Gaussian elastic behavior, which is attributed to the same cause.
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  • 61
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 63-81 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Detailed structure analysis of the polyoxymethylene molecule was carried out by the method of three-dimensional Fourier synthesis. The diffraction data were measured on a highly ordered polyoxymethylene sample prepared from a single crystal of tetraoxane by solid-state radiation polymerization. By assuming the anisotropic thermal factors for the oxygen and carbon atoms and taking into account the contribution of the hydrogen atoms, good agreement between the observed and calculated structure factors was obtained; the R factor is 8.8%. The distance between the oxygen atom and the helix axis r(O) = 0.671 A. is slightly shorter than r(C) = 0.691 A. The bond distance C—O = 1.421 A., the angle ∠COC = 112°24′, and ∠OCO = 110°49′. All the internal rotation angles of the skeletal bonds are 78°13′. It is deduced from the experimental results that each crystallite of polyoxymethylene is composed of only one type of helix, right-handed or left-handed.
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  • 62
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 83-87 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relation of the high-frequency elastic moduli of semicrystalline polymers to volume fraction crystallinity is correctly described by the Hashin-Shtrikman theory, without any disposable constants, as a function of the ratio of the modulus of the amorphous to that of the crystalline phase. Hence the (high-frequency) reduced modulus of semicrystalline polymers is largely a function of the temperature T/Tg. The importance of T/Tm for the modulus of the crystalline phase precludes the existence of a single universal reduced modulus versus temperature curve.
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  • 63
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 239-262 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The infrared absorption spectra of selected crystalline and noncrystalline bands were studied in bulk-crystallized specimens of linear polyethylene which encompassed the extremely wide density range of 0.92-0.99 g./cm.3. The analysis of the data obtained at room temperature yield degrees of crystallinity by infrared methods which are in very good accord with the values deduced from the density measurements. Studies of the infrared spectra as a function of temperature give fusion curves which are in agreement with those obtained by thermodynamic methods. However, in order to obtain these latter results cognizance must be taken of the large negative temperature coefficient of the specific extinction coefficients of the crystalline bands from room temperature to the melting point. The necessary data to account for this phenomena were obtained from studies of the spectra of the n-paraffin, C94H190, where molecular crystals are formed. Analysis of the two gauche bands, at 1352 and 1303 cm.-1, which are assigned to the noncrystalline regions demonstrate that for bulk-crystallized samples of lowest densities the intensity ratio at room temperature is identical to that expected from the pure melt at this temperature. The conclusion is thus reached that the noncrystalline regions in these cases and the pure melt are structurally very similar. For samples of higher density, where the crystallite size is comparable to the extended chain length, the intensity ratio of the two gauche bands is altered. This change could reflect a change in the sequential distribution of gauche bonds. This intensity ratio for crystals formed from dilute solution is very similar to that for the high-density bulk-crystallized material and indicates a similarity in structure of the noncrystalline regions in the two cases.
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  • 64
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 277-288 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: To investigate the solution properties of polyethylene, which has the simplest structure of the vinyl polymers, experiments were made with a magnetically suspended equilibrium ultracentrifuge. Preliminary studies were carried out with a polystyrene-chloroform system at 25°C. and a polystyrene-methylcyclohexane system at 68°C. (which is close to the theta temperature) in order to check the difficulties involved in the flotation equilibrium in the former case and the high temperature measurement in the latter. However, no trouble was encountered in either system, and the results were discussed and compared with earlier results for polystyrene solutions. It was found that chloroform is a good solvent for polystyrene, and the measured weight-average molecular weight is somewhat smaller than the value obtained in a theta solvent. After overcoming some technical difficulties involved in studies at higher temperatures, we carried out experiments on polyethylene in α-chloronaphthalene at 130°C. The results are considered reasonable by comparison with results obtained by other methods. The sample employed, Marlex 50 of melt index 0.7, has a wide molecular weight distribution: i.e., Mz/Mw = 5.2 and Mz+1/Mz = 2.4.
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  • 65
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 289-300 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Accurate measurements of stress relaxation after steady-state flow have been carried out, in the Newtonian flow region, for a polystyrene and a poly(methyl methacrylate) melt, with a cone-and-plate rotational rheometer. From the stress relaxation σ(t) versus t curves the relaxation spectra H were calculated by means of the first approximation equation: \documentclass{article}\pagestyle{empty}\begin{document}$ H = - ({1 \mathord{\left/ {\vphantom {1 {\dot \gamma t)d\sigma {{(t)} \mathord{\left/ {\vphantom {{(t)} d}} \right. \kern-\nulldelimiterspace} d}}}} \right. \kern-\nulldelimiterspace} {\dot \gamma t)d\sigma {{(t)} \mathord{\left/ {\vphantom {{(t)} d}} \right. \kern-\nulldelimiterspace} d}}}\ln t $\end{document}. The shear stress-shear rate curves, σ versus \documentclass{article}\pagestyle{empty}\begin{document}$ {\dot \gamma } $\end{document} were also measured, in large ranges of shear rates, for the same melts, and from these data the relaxation spectra H were obtained by means of equations given by Faucher and Ferry. The Faucher equation, \documentclass{article}\pagestyle{empty}\begin{document}$ H = - \dot \gamma ^2 d{\sigma \mathord{\left/ {\vphantom {\sigma d}} \right. \kern-\nulldelimiterspace} d}\dot \gamma ^2 $\end{document}, has been found to give results which compare satisfactorily with those obtained from the first approximation equation. It has been found that the Ferry equation has to be modified for comparable agreement.
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  • 66
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 315-322 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of polydispersity on liquid-liquid phase equilibrium in systems containing polymer, solvent, and nonsolvent is investigated numerically in the Flory-Huggins approximation for several special cases. The resulting phase diagrams indicate that, except in the immediate vicinity of the critical region, the degree of swelling of a polymer precipitate phase with a given number-average molecular weight is essentially independent of polydispersity.
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  • 67
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 399-415 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The statistical mechanical treatment of polymeric chains in terms of the largest eigenvalue of the product of statistical weight matrices for the rotational interactions of skeletal bonds of the repeat unit becomes excessively complicated if the repeat unit spans more than three or four skeletal bonds. Moreover, such treatment is necessarily limited to chains in which the number of repeat units is indefinitely large. Newer methods are readily applicable to chains of any degree of polymerization comprising repeat units of any realizable length. If interdependence of neighboring bond rotations is confined to bond pairs within a given unit, rotations about a pair of bonds belonging to neighboring units being mutually independent, further simplifications may be introduced without sacrifice of rigor. Polyamides, in which rotation about bonds on opposite sides of the amide group are independent, are polymers of this type. Adherence of the amide group to the planar trans conformation favors a more extended configuration of the chain, but this effect is dominated by the smaller steric repulsions affecting rotations about bonds which are first, second, and third neighbors of the amide group. It is for this reason that the characteristic ratio 〈r2〉0〉/nl2 for poly(hexamethylene adipamide), ca. 6.0 according to experimental results of Saunders, is less than the value, 8.0, for polymethylene at 25°C. The characteristic ratios and molecular dipole moments are computed as functions of the degree of polymerization. The poly(εaminocaproamide) chain also is treated.
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  • 68
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 461-470 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Proceeding from the work of Zimm and Stockmayer and of Benoit, a general formula is derived for the calculation of the radius of gyration of block and graft copolymers. It appears that with linear block copolymers the ratio of the mean-square radius of gyration and the mean-square end-to-end distance is usually not far from 1/6. With a great number of blocks the difference from 1/6 can entirely be neglected. Also the influence of the composition of the molecules on the scattered light intensity has been considered.
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  • 69
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 639-652 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The primary reaction of oxygen with irradiated polyethylene has been followed by observing the rapid disappearance of the ultraviolet absorption bands at 258 and 285 mμ, bands attributed to the allyl and dienyl free radicals. A mathematical theory based on diffusion equations has been developed by means of which a quantitative estimate of the total initial free-radical concentration can be made. From the shape of the free-radical decay curve it can be concluded that the initial oxygen-free-radical reactions occur about three times as frequently in the amorphous regions as in the crystalline.
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  • 70
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 653-662 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Aromatic poly(amic acids) derived from pyromellitic dianhydride and 4,4′,-diaminodiphenyl ether were characterized by dilute solution techniques. Number-average molecular weights M̄n of 13 samples ranged from 13,000 to 55,000 (DP 31-131). Weight-average molecular weights M̄w of 21 samples ranged from 9,900 to 266,000. The ratio M̄w/M̄n was between 2.2 and 4.8. Heterogeneous polymerization yielded higher molecular weight polymer than homogeneous polymerization. The molecular weight could be varied systematically by control of stoichiometric imbalance. Use of very pure monomers and solvent gave polymers of relatively high number-average molecular weight (∼50, 000) and the most probable molecular weight distribution M̄w/M̄n = 2. Impure monomers and/or solvent resulted in lower number-average molecular weight (M̄n ≅ 20,000-30,000) and wider distributions (M̄w/M̄n = 3-5). The Mark-Houwink relation obtained was [η] = 1.85 × 10-4M̄w0.80 The exponent is characteristic of moderately extended solvated coils. The unperturbed chain dimensions (r02/M)1/2 were 0.848 A., and the steric factor σ was 1.24 which is close to the limiting value of unity for an equivalent chain with free internal rotations. The sedimentation constant-molecular weight relation was S0 = 2.70 × 10-2M̄w0.39. This exponent is consistent with the Mark-Houwink exponent.
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  • 71
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 705-710 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Recent precision measurements of the heats of combustion of atactic and isotactic polystyrene permit an unequivocal calculation of the enthalpy difference in the bulk amorphous forms of the two isomers of this polymer. Contributions to this quantity arise mainly from the differences in nonbonded interactions in the two configurations but may also contain terms relating to higher energy conformations and to intermolecular interactions. The thermochemical and NMR data of specific polymers and of simple molecules are discussed in a comparison with model compound calculations. The thermochemical method has potentially important applications in studying molecular interactions in stereoregular polymers.
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  • 72
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The Tian-Calvet microcalorimeter has been used to measure the heat of solution of atactic polystyrene in toluene at 30°C. By using a special technique for polymer sample preparation, it has been possible to measure directly the difference in conformational energy of the polystyrene chain at different temperatures, from 30 to 100°C. and to calculate its contribution to the specific heat.
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  • 73
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 761-769 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The α, β, and γ transitions at temperatures between -200 and +100°C. of crosslinked aromatic and aliphatic epoxy polymers were determined from damping and shear modulus data, and compared with their fluorine containing analogs. Loci of segmental relaxation are suggested at various temperatures, and similarities between aliphatic and fluorocarbon segments, and polyethylene and polytetrafluoroethylene are discussed. Two systems of structurally similar monomers 2,2,3,3,4,4-hexafluoropentane diglycidyl ether-1,5 and 1,4-butane diglycidyl ether, and 2,2-bis(4-glycidyl phenyl ether)hexafluoropropane and 2,2-bis(4-glycidyl phenyl ether) propane were polymerized with the aid of two diamine curing agents, namely, ethylenediamine and m-xylylenediamine. Polymers of the aromatic diepoxides showed transitions with peaks at -56°C. and above +70°C. Three main peaks were registered for the aliphatic and fluorocarbon diepoxides: at -125 and at -100°C., at -56°C., and at 0°C. It is suggested that the Tg is affected by an interdependence of relaxation of all components of the polymer main chain.
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  • 74
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    Journal of Polymer Science: Macromolecular Reviews 1 (1967), S. 35-56 
    ISSN: 0076-2083
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 75
    ISSN: 0076-2083
    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Heterogeneous olefin polymerization catalysts generally consist of a transition metal compound from groups IVB or VB in combination with an organometallic compound from groups I, II, and III of the periodic table of the elements, but in some instances may contain a third component possessing at least one strongly complexing ligand atom. The composition of a coordination catalyst of this type determines both the rate of polymerization of the α-olefin and the stereoregularity of the polymer produced. In order to predict activity and stereospecificity of catalysts for the polymerization of α-olefins, data from the polymerization of propylene using catalysts of the following types were correlated: (1) titanium(III) chloride catalysts in which the organometallic component was varied, (2) coordination catalysts containinig a ligand third component in which the ligand was varied, and (3) coordination catalysts in which the transition metal component was varied.The electronegativity of an orgariometallic compound is known to be important in determining its reactivity with ethers, hydrogen, and other reagents. Both the ionic size and the electronegativity of the central atom appear to be important in determining the utility of both the organometallic and the transition metal compounds as components for coordination catalysts. In general, organometallic and transition metal compounds having small central atoms with similar electronegativities favor the formation of stereospecific catalysts.The present correlation has made it possible to predict the activity and stereospecificity of coordination catalysts for olefin polymerization.
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  • 76
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    Journal of Morphology 121 (1967), S. 1-18 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Catostomus macrocheilus, a sucker, and Poecilia reticulata, a live-bearer, are subjected to dissimilar mechanical stresses while most of their bony structures are forming. Osteogenesis occurs in the sucker when it is a free-living larva, whereas in the livebearer it occurs intrafollicularly. The first-formed bones ofboth species are those that meet functional demands and are subjected to the greatest stresses. These are the movable bones associated with the acts of respiration and feeding, and some of the axial bones. The cranial roof is the last to calcify. The primary differences in osteogenesis of the two species, such as in the vertebral column and caudal fin, can be correlated with differences in stress. Surface forces on calcifiable tissue perhapsassist in the deposition of calcium salts.
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  • 77
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: Histological serial sections of spleens from the adult raccoon (Procyon lotor) and woodchuck (Marmota monax) were processed for microscopic examination. Observations related to various aspects of the internal vascular pattern in the spleen of the raccoon and woodchuck demonstrated features that were characteristic of the respective animal. The spleen of the raccoon possess well-developed ellipsoid sheaths, whereas these same structures were not as prominent in the spleen of the woodchuck. The spleen of both mammals examined demonstrated the presence of an anastomosing series of venous sinuses within the red pulp tissue and may be classified as sinusal in nature.
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    Journal of Morphology 121 (1967), S. 19-28 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the column of hydra, tissues continually move away from a region located just underthe whorl of tentacles. Above this subtentacular region, tissues proceed into the hypostome and tentacles; below it tissues pass into the buds or continue down the stalk. These movements represent a steady state pattern of tissue renewal in which column growth is balanced by tissue loss at the body extremities. But the existence of a subtentacular zone in which tissue appears stationary does not necessarily indicate that growth is restrictedto this region, as is commonly stated.The body column of hydra can be viewed as an expanding cylinder whose elongation is balanced by tissue loss at the two ends. In such a body there must be one region from whichtissue appears to emanate, regardless of how growth is distributed along the cylinder. Only the rates at which tissues move will be characteristic of the underlying growthpattern. In Hydra littoralis, the measured rates of tissue movement down the gastric column are consistent with the distributions of mitotic figures, which indicate that growth is spread out along the column.
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  • 79
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    Journal of Morphology 121 (1967), S. 71-80 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Profiles of fresh chick lenses of 5, 8, 11, 14, 17 and 20 days embryological age were photographed and from tracings of these profiles, volumes were calculated using a formula for volume of a solid of revolution. Accurate volumes were also obtained by assuming the lens to be two half oblate spheroids of different minor axis, or, better, two half-solids of profile (x/a)k + (y/b)k = 1. In addition, the k in this equation described well the curvature of the lens profiles and thus provided a quantitative measure of developing lens shape. Lens diameter, depth and shift of equatorial diameter upon lens axis as a function of age were also studied.
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  • 80
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Ductuli efferentes in four examined genera of family Didelphidae are organized into highly convoluted tubules, located within a conical body adjacent to the vascular plexus supplying the testis. They have yellowish-green color in the adult Didelphis virginiana and grey pink color in other genera. The ductuli efferentes in all examined animals are lined by very low columnar cells, covered by microvilli or booth cilia and microvilli.Histochemical analysis reveals several types of cytoplasmic granules in the genera examined. A single sperical body about 1.5 μ in diameter is found in epithelial cells of the four eyed opossum (genus Philander); this body stains positively for RNA and non-histone protein, and appears granular under the electron microscope, without a limiting membrane. Abundant cytoplasmic bodies in the Virginia opossum show strong reactions for SH groups; these granules may be responsible for the green color of the ductuli in this species. Ultrastructural studies show that the morphology of membrane limited granules in the ductuli of the examined genera is characteristic for each genus. Abundant pinocytotic vacuoles in the apices of these cells and a strongly positive alkaline phosphatase reaction suggest a marked absorptive activity of epithelial cells.
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  • 81
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The fine structure of the nerve cell types in the white planarian Procotyla fluviatilis were described. Ganglion cells comprise the major portion of the brain. These cells are irregular in shape with several cytoplasmic processes and contain ribosomes, a sparse endoplasmic reticulum, microtubules, lysosomes, and a Golgi apparatus with numerous small vesicles. Granule-containing cells are situated in the peripheral regions of the brain and along the nerve cords. These cells contain ribosomes, rough-surfaced endoplasmic reticulum and a Golgi apparatus with associated dense granules. The granules occupy most of the cytoplasm and are ∼ 750A in diameter with moderately dense contents, ∼ 750A with opaque contents, and ∼ 1000A with contents of medium density. These granules are similar to those in the nervous systems of higher animals that contain epinephrine, norepinephrine, and neurosecretory substance, respectively. Each cell contains predominantly one type of granule although there is some intermixing of granules and intermediate types between the three most abundant granules. Small clear vesicles, resembling cholinergic synaptic vesicles, and all types of dense granules occur in the neuropil and within nerve endings.
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  • 82
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    Journal of Morphology 122 (1967), S. 169-173 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Histological examination of the fibrous and cellular connective tissue components of the periodontal ligament in the Caiman and the Alligator reveals the presence of reticular fibrillae, collagenic, elastic, and oxytalan fibers, as well as fibrocytes, osteoblasts, cementoblasts and epithelial rests. The oxytalan fibers differentiated by the peracetic acid aldehyde-fuchsin method are most numerous in the coronal region, radiating from the primary cementum into the periodontal ligament a short distance. Oxytalan fibers in fewer numbers are found interspersed between the oblique and the horizontal principal fiber bundles. Inasmuch as the crocodilian teeth have continuous replacement and thus a relatively short functional life, the oxytalan fibers of the Caiman and the Alligator appear to be proportionally fewer in number than they are in the mammalian periodontal tissues. The presence of the oxytalan fibers and epithelial rests in the Order Crocodilia (Crocodilia) adds to the number of dental structures shared with the Class Mammalia (Mammalia) (mammals) such as a stellate reticulum, a primary and secondary cementum and a periodontal ligament. This furnishes additional histological evidence for evaluation of the phylogenetic position of this group.
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  • 83
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Histochemical methods, especially azo dye methods for detecting acid phosphomonoesterase activity were applied to normal, regenerating and denervated, amputated limbs from larval Amblystoma maculatum. Efforts were made to control inactivation of enzymic activity and diffusion of both enzyme and reaction product. “Base-line” values for enzymic activity were determined for normal limbs. Activity appeared most intense in macrophages, less intense in epidermis and cartilage matrix. Some activity was detected in Schwann cells, peri- and endoneurium and muscle fibers form normal limbs. Enzymic activity in regenerating limbs was strongest within macrophages which appeared in increased numbers especially in early stages. Wound tissue showed little increased activity. As the blastema formed, increased enzymic activity was detected in epidermis and within increased numbers of macrophages. Chondrocytes showed increased activity especially during cartilage matrix deposition. Amputated, denervated limbs showed large numbers of active macrophages beneath and within epidermis and along muscle. As regression commenced, areas of cartilage matrix breakdown showed increased enzymic activity but, in general, greatest activity was in macrophages. The various possible roles of acid phosphomonoesterase activity in the specific biological situations dealt with are considered in light of such observations.
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  • 84
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    Journal of Morphology 122 (1967), S. 249-263 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Adult newts, Triturus viridescens, were treated with from 1.0-10.0 μg/g body weight of actinomycin D one day before amputation of both forelimbs. Mean survival times ranged from over 50 days in newts treated with 1.0 μg/g to 13.2 days in animals given 10.0 μg/g body weight of actinomycin. Low doses little altered the course of regeneration, but animals treated with over 2.0 μg/g never formed blastemas. In another series, animals were given doses of 2.5 μg/g body weight of actinomycin D at intervals from 14 days before to 30 days after amputation. It was found that certain signs of toxicity (loss of equilibrium) are related to the time of administration of the drug whereas others (hemorrhage into the limb stumps) are restricted to a definite phase of the regenerative process. Early administration of actinomycin completely inhibits regeneration whereas later treatment results in a considerably lessened effect. The postamputational stages which are basically destructive in nature are not noticeably affected by actinomycin D, but the phases of dedifferentiation, blastema formation and redifferentiation are strongly inhibited.
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  • 85
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    Journal of Morphology 122 (1967), S. 345-365 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The major events associated with the morphogenesis of the amphibian alimentary tract are described and illustrated with a series of photomicrographs that present a continuous account of the differentiation process from its onset at stage 38 until the initiation of feeding at stage 46. Histological evidence is presented for the normal disappearance of the midgut region of the archenteron and the de novo formation of the intestine through the yolk mass. The mechanics of intestinal lumen formation are discussed in terms of the dynamic autonomous actions and interactions of the endoderm and the splanchnic mesoderm. The opening of the intestinal lumen as a consequence of cytolysis or cellular digestion is discounted. The relation of the present observations to the previously described polar endoderm cells is considered.
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  • 86
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    Journal of Morphology 123 (1967) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 87
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The bullfrog, Rana catesbeiana, possesses lympho-myeloid and epithelial structures that are morphologically similar in some respects to lymph nodes of mammals. These organs are present during the entire life cycle of the frog, however, the structures that are present during larval stages do not appear to be morphological precursors of adult organs. According to certain terms used previously by other investigators, two major organs are present throughout the larval stages: the lymph gland and the ventral cavity body. In the adult, the jugular body, the epithelial body, the precoracoid and propericardial bodies are found in the ventral neck region in contrast to the lateral and ventral arrangement of the lymph gland and ventral cavity body in larvae. The function of these organs is not known but it is believed that they play a role in the production of certain blood cells, particularly lymphocytes, and they may be involved in some aspects of the differentiation and maintenance of the immune response capacity.
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  • 88
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: The morphology and possible functional significance of cytoplasmic filaments associated with herpes-like viruses of the frog renal carcinoma is described. Filaments, invariability arranged in elongated bundles or sheaths, individually measure approximately 30 mμ in diameter, and are composed of finely granular, proteinaceous material. During the viral maturation sequence, this material is believed to be deposited on the surface of the capsid, thereby possibly providing the virus with a defensive coating prior to ergression from the cell.
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  • 89
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    Journal of Morphology 123 (1967), S. 109-119 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The development of Stannius corpuscles in the teleost Colisa lalia is described. Certain cells of the mesonephric tubules differentiate and proliferate to form buds which evaginate and finally become separated from the structure of origin. The separated cellular masses undergo further histologic differentiation to attain the adult structures.The corpuscles in C. laha, in contrast to some other teleosts, develop only from mesonephric tubules. A possible explanation for the different types of distribution of Stannius corpuscles in teleosts is suggested, and the possible homology of these structures with part of the adrenal cortex or higher vertebrates is discussed.
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  • 90
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    Journal of Morphology 123 (1967), S. 157-171 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The morphology of the epidermal generations throughout the sloughing cycle of Anolis carolinensis is essentially the same as that described for other squamates, whether studied in control or hormone-injected animals. Readily identifiable granules in the clear layer of this and other lizard species emphasize the eventual hardening of this layer prior to its separation from the subjacent Oberhautchen, which brings about sloughing. Eosinophils are described for the first time in the lacunar tissue of lizard, but their functional role remains problematical. Daily 25 μg injections of prolactin (alone or in combination with gonadotropins) raise the frequency of sloughing by shortening the resting phase as compared with controls and animals receiving 1.0 I.U./day injections of gonadotropins. The duration of the proliferation-renewal phase and the pattern of histological changes occurring therein is unchanged by experimental treatments. The results show that neither endogenous nor exogenous gonadotropins affect the sloughing frequency, but exogenous prolactin produces a similar effect to that described for thyroxine. Although the mechanisms of action are unknown, the results provide another example of the cutaneous action of prolactin in vertebrates.
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  • 91
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    Journal of Morphology 123 (1967), S. 559-567 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Hemolymph cells of Orconectes virilis were stained during the months of August to November by a variety of histological and histochemical techniques. Cells were classified as hyaline cells, small granulocytes, and large granulocytes. Presence of mitochondrial enzymes was indicated by tests for succinic dehydrogenase and cytochrome oxidase. Reaction to test for the hydrolytic enzyme, leucine acylnaphthylamidase was intense in the granules of the large granulocytes. The PAS reaction indicated a mucopolysaccharide at the cell membrane. Lipid was found in all three hemolymph cell types of Orconectes virilis at the time of this study.
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  • 92
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ultrastructural changes occurring during the differentiation of the pancreatic acinar cell were studied in White Leghorn chick embryos from the onset of pancreatic morphogenesis on day 3 of incubation (day 3) to hatching. Generally, the changes included a loss of some structures, the addition of others and modification of existing structures. Numerous cytoplasmic filaments which were present in the early migrating cells of the pancreatic bud were no longer present on day 5. The nucleoli enlarged temporarily on days 5-6 and then resumed a reduced size. The Golgi apparatus enlarged by day 6 and remained this way throughout the embryonic period. Associated with these changes was the initial appearance of the zymogen granules on day 5. The endoplasmic reticulum was present initially in both the smooth and the rough forms. The rough form and the outer nuclear membrane were both initially studded intermittently with aggregates of ribosomes. Subsequently, there was an increase in the number of attached ribosomes, an increase in the amount of rough reticulum and a decrease in smooth membranes. The ribosomes attached to the membranes appeared to augment the large free ribosome population characteristic of the early cells. Mitochondria did not appear to increase in number but there was an increase in size. The granules varied in kind, number and size with developmental age. The first granules formed (days 3-5) appeared to be miniatures of the mature type. Subsequently, a heterogeneity of granule morphologies was present.
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  • 93
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The content and synthesis of ribonucleic acid (RNA) and protein was studied by microphotometry and autoradiography in the developing pancreatic acinar cells of White Leghorn chick embryos. These findings were correlated with previously reported changes in ultrastructural components. Shortly before or concomitant with zymogen granulation, RNA synthesis increased, in association with increases in the amount of nucleolar and cytoplasmic protein. The cytoplasmic fraction was transitory, whereas the accumulated nucleolar protein was maintained and was soon followed by an increase in nucleolar RNA. Concomitantly, a decrease in chromosomal RNA was observed, with the total amount of nuclear RNA staying constant. When zymogen first appeared, nucleoli were greatly enlarged due to large amounts of RNA and protein; total cellular RNA and protein had decreased slightly, in association with a decrease in cell volume. Subsequent development presented smaller nucleoli with decreased amounts of RNA and protein. Total cellular RNA increased due to its accumulation in the cytoplasm, probably as ribosomes. The accumulation of zymogen and the enlargement of other cellular structures contributed to an increase in total cellular protein. Prior to hatching, total cell RNA and protein decreased in amount, probably due to a reduction in cell volume through cell division.
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  • 94
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    Journal of Morphology 123 (1967), S. 213-230 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Seventy-seven hearts from one species of bat, Eidolon helvum Kerr, have been examined as a preliminary step in correlating cardiac form the and function in relation to flight in mammals. The supposition is that the heart, like the upper limbs and pectoral girdle, will show deviations from the common mammalian plan because of the animal's unusual way of life.The first thing that happens in flight, as in any form of exercise, is an immense increase in venous return to the heart. The architecture of the sinus venarum of the right atrium and of the right ventricle in the region of the atrioventricular valve, including the position of the papillary muscles, may be related to prevention of rapid overdistension of the right side of the heart. The walls of the inflow and outflow tracts of the right ventricle are exceptionally smooth, an anatomical feature that may have significance in that friction may be reduced. The left side of the heart resembles that of other mammals more closely.
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  • 95
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have examined the fine structure of injured, repairing and regenerating tissues of the amputated forelimbs of the adult newt: observations were made on wound epithelium, nerves, striated muscle, the regeneration blastema, connective tissues and cartilage.The wound epithelium shows little modulation from the adjacent epidermis: a subjacent glycocalyx and hemidesmosomes are initially absent. Some cells reveal phagocytic activity. As regeneration progresses, a glycocalyx, hemidesmosomes, and an adepidermal reticulum of fibers develop.Nerve fiber degeneration and regeneration lie side by side in the same nerve bundle. Myelin degeneration is evident within 24 hours; neural connective tissues loosen and fibers appear to spread apart.Striated muscle fibers display a nonuniform response to trauma, due to unequal degree of injury inflicted by amputation. The moderately and greatly injured fibers lose their distal fibril organization. There is a numerical increase in mitochondria, and occasionally a pyknotic nucleus is present. The myofiber glycocalyx appears to resist destruction, even when cell degeneration is extensive. Satellite cells have been observed intimately in contact with injured myofibers. Myogenesis is accompanied by an increase in collagen fibrillogenesis associated with adjacent fibroblasts. Many of these latter cells appear to contain intracellular fibrils: the significance of these observations are discussed, and a basis for intracellular fibrillogenesis and tropocollagen accretion is proposed.The fine structure of the regeneration blastema cell agrees with the description offered by others for the adult newt limb regeneration.Early prochondral condensation of blastema cells is described briefly.
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  • 96
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1313-1316 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 97
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. i 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 98
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1-21 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Light-scattering, viscometric and osmometric studies have been carried out on dilute solutions of polycarbonate fractions both in a good solvent and in theta solvents. The data span the molecular weight interval 5 〈 10-3M 〈 760. It has been concluded that: (1) the overall behavior in dilute solution is consistent with a flexible chain conformation; (2) the ratio of the unperturbed mean-square radius to the molecular weight, or to the number of chain elements, is larger than commonly observed for vinyl polymers; (3) the ratio of the unperturbed radius to the radius calculated for a chain with free rotation about valence bonds has the unusually small value 1.3; and (4) the hydrodynamic behavior of the chain may reflect partical draining affects.
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  • 99
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 125-142 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Degradation of poly(ethylene oxide) (PEO) by violent stirring was studied in various solvents. The chain scission or the limit of the degradation was measured, and the effects of solvents, polymer concentration, stirring speed and degree of polymerization (DP) were investigated. It was found that the number of bonds broken per polymer chain was independent of the concentration but increased with the stirring speed and with decrease in the DP. The rate was much affected by the solvent used, being larger in a poor solvent. It was also found that the rate could be represented either by Jellinek's or Ovenall's rate equations, which have been applied to the ultrasonic degradation of polymers in solution.
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  • 100
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 165-177 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermal expansion and dielectric relaxation of polyacrylonitrile were measured in the temperature range from -75 to 152°C. at frequencies from 30 cps to 3 Mc./sec. The thermal expansion curve and the temperature dependence of logarithmic relaxation time both show an inflection at 85°C. An x-ray study by Bohn reveals that this inflection comes from the thermal expansion of the paracrystalline phase of this polymer, and consequently the transition at 85°C. and the associated relaxation are ascribed to molecular motion in the paracrystalline phase. The relaxation strength increases with increasing temperature above this point. The transition is caused by freezing of the bending vibration of chains whereas the relaxation results from rotational vibration. The length of segments in this phase is roughly estimated to be ca. 100 A. by comparing the observed relaxation strength with the theory developed on the basis of the above considerations.
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