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  • Polymer and Materials Science  (1,970)
  • General Chemistry  (865)
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  • THERMODYNAMICS AND COMBUSTION
  • Wiley-Blackwell  (3,027)
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  • 1910-1914
  • 1970  (3,027)
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  • Wiley-Blackwell  (3,027)
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  • 1970-1974  (3,027)
  • 1910-1914
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  • 101
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    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 657-678 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: On axial extension of polymer melts at constant deformation rates, the development of high-elastic deformation is of predominant importance during the initial period. High-elastic deformation is accompanied by a rise in viscosity and in the modulus of high-elasticity and by retardation of the relaxation processes in the region of large relaxation times. At relatively low deformation rates, the rise in viscosity and high-elasticity modulus and the retardation of relaxation processes may give way to a decrease in viscosity and high-elasticity modulus and acceleration of relaxation processes, so that stationary flow regimes are attained. The transition from strain regimes with increasing viscosity and modulus of high elasticity to those with a decrease of these quantities corresponds to an increase in the rate of accumulation of irreversible deformation. Accordingly, a competing influence due to the orientation effect and to destruction of the network of intermolecular bonds becomes evident while stationary flow is being attained. The orientation effect must be responsible for the retardation of the relaxation processes, whereas rupture of the intermolecular network bonds results in structural relaxation accelerating relaxation processes. In contrast to shearing, during extension the orientation effect is of predominant importance. Hence in stationary flow regimes the viscosity may not only remain independent of the rate of strain, but even increase with it. In this case the contribution of the large relaxation times to the relaxation spectrum increases with increasing stress in stationary flow regimes. The fact that the longitudinal viscosity and the modulus of high elasticity are independent of the stress in stationary flow regimes does not guarantee linearity of the mechanical properties of the polymer in the prestationary stage of deformation when complex changes occur in its relaxation characteristics. At high deformation rates the viscosity and the modulus of high elasticity keep rising with increasing deformation until rupture occurs. Determination of the strength of polystyrene samples vitrified after extension showed that it is due not to the entire degree of extension, but only to the value of accumulated high-elastic deformation. The strength of the vitrified samples is to a first approximation independent of the rate at which the melt was extended.
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  • 102
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 727-738 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dielectric relaxation data have been obtained for two ethylene-methacrylic acid copolymers (containing about 4 mole-% methacrylic acid units and about 8 mole-% methacrylic acid units, respectively) and the lithium, sodium, and calcium salts prepared by partial neutralization of the polyacids. The frequency range employed was from 50 Hz to 10 kHz and the temperature range was from -130°C to 100°C. Attention is focused on three dielectric loss regions labeled β, β and α in order of increasing temperature. The β′ process (-10°C at 100 Hz in the salts only) correlates with a mechanical loss process previously reported and is attributed to microbrownian motion taking place in an amorphous hydrocarbon phase. The β′ process (20°C at 100 Hz) has also been observed mechanically and is attributed to the same mechanism as the β process. The higher temperature of this relaxation compared to the β relaxation is attributed to the presence of acid groups which form crosslinks composed of interchain hydrogen bonds. The α process (〉50°C at 100 Hz in the salts only) correlates with dielectric and NMR data previously reported for a sodium salt and is assigned to motions within ionic domains formed by the clustering of salt groups.
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  • 103
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 807-811 
    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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  • 104
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 815-816 
    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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  • 105
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Sedimentation equilibrium in the ultracentrifuge means that there is such a distribution of molecular species throughout the cell, that the centrifugal forces are balanced by differences in the activities. This provides a method for determination of the activities and the chemical potentials in polymer solutions which, in principle, is very simple and reliable. A complication is caused by polydispersity of the dissolved polymer. If one assumes that the interaction parameter depends on concentration and temperature, but not on molecular weight, it is possible to determine the chemical potential of polymer and solvent from the ultracentrifugal data. Experiments have been carried out on the systems polystyrene-toluene and polystyrene-cyclohexane at different temperatures and in the concentration range 0-80 wt-%. The results are expressed in the data for the chemical potential of the solvent, the number average chemical potential of the polymer and the interaction parameter χ.
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  • 106
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 921-935 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Several partially interpenetrating polymeric networks (IPN) were made by combining chemically different linear elastomers. The polymer combinations were deposited as films from aqueous emulsions made by mixing the individual emulsions in equal proportions. The films were crosslinked to form two superimposed networks. In two cases, the networks were cleanly separated by hydrolysis of one of the component networks to demonstrate that there was no chemical interaction between the polymers. Measurement of crosslink density showed that, in most cases, partial interpenetration does occur as evidenced by an effective crosslink density of the IPN's greater than the arithmetic mean of the crosslink densities of the component networks. The swelling ratios, densities, and stress-strain properties were determined. For one of the network combinations, a poly(urethane-urea) and a poly(butadiene-acrylonitrile), a series of IPN's varying in polymer composition was made. The swelling ratios and densities are close to the arithmetic means; however, both the tensile strength and crosslink density exhibit a maximum at about 70% poly(butadiene-acrylonitrile). The maximum tensile strength is actually significantly higher than that of either of the component polymers. The elongations all approach that of the poly(urethane-urea), the more extensible material, except for compositions approaching 100% poly(butadiene-acrylonitrile), which exhibit a very low extensibility.
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  • 107
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 969-977 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Characteristic wide-line proton magnetic resonance absorption spectra of a number of representative cellulose preparations have been obtained in the dry state and after addition of about 7% water. Line widths, second moments, spin-spin and spin-lattice relaxation times have been determined. The second moment of the absorption curve of dry cellulose was found to correlate well with the crystalline fraction for most specimens. A technique is described for determining the number of water-cellulose protons exchanging relative to the number of cellulose protons not exchanging. The reduction in absorption line width observed when water is added to cellulose is shown to be quantitatively consistent with such a proton exchange phenomenon.
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  • 108
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1755-1772 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The morphology of selenium has been studied in light of present concepts of crystallinity in crystalline organic polymers. Spherulitic crystallization and resultant morphology were examined as a function of temperature by transmission and replication electron microscopy, electron diffraction, and optical microscopy. Evidence is given for polymer chain folding during crystallization of trigonal selenium. Theoretical thermodynamic calculations presented yield several thermodynamic values including an equilibrium melting point of 219.2°C, a fold surface energy of 337 ergs/cm2 and a lateral surface energy of 9.8 ergs/cm2.
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  • 109
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1803-1821 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Various procedures for universal calibration in gel-permeation chromatography with polystyrene gels are examined for polystyrene and polydimethylsiloxane fractions. For o-dichlorobenzene at 138°C, experimental intrinsic viscosity-molecular weight data show that the Mark-Houwink exponents are 0.70 and 0.57 for polystyrene and polydimethylsiloxane, respectively. In principle, this difference permits a distinction between the various polymer size parameters proposed for universal calibration. An interpretation of the experimental polydimethylsiloxane calibration for o-dichlorobenzene at 138°C requires a consideration of errors in average molecular weights and errors arising from the use of average molecular weight instead of peak molecular weight. When calibration procedures utilizing hydrodynamic volume and unperturbed dimensions are examined, the difference between them is comparable with experimental error. If the Flory-Fox viscosity expression is employed, the perturbed end-to-end distance (or radius of gyration) and the hydrodynamic volume give equivalent universal calibrations. The experimental data are sufficiently accurate to show that the perturbed dimension determined with the Ptitsyn-Eizner relation does not give an adequate universal calibration.
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  • 110
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1545-1564 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Crystallization of compression-molded isotactic polypropylene and polyethylene is invariably spherulitic; generally, nucleation occurs randomly throughout the sample. In a special case where nucleation predominates at the surface, spherulitic growth centers become crowded and are forced to propagate unidirectionally into the bulk (transcrystallinity). Conditions for the formation of transcrystallinity have been investigated by optical and scanning electron microscopy. The occurrence of transcrystallinity is attributed to heterogeneous nucleation induced at the mold surface. To be effective, the mold surface must have a nucleating efficiency equal to or greater than that of adventitious nuclei present in the polymer. As the crystallization temperature approaches the melting point, the activity of mold surfaces is found to increase leading invariably to transcrystalline formation. The degree of activity of various mold surfaces correlates with the known activity of specific dispersed nucleating agents having similar chemical structures. Contrary to claims in the literature, the surface energy of the mold surface and temperature gradients across the melt surface do not play a primary role in transcrystalline formation of polypropylene.
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  • 111
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1909-1916 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The flow behavior of α,ω-dihydroxypolydimethylsiloxanes, having a weight-average number-average molecular weight ratio of 1.1-1.2, was studied with a Cannon-Manning viscometer and an Instron rheometer. Comparison of the flow behavior of samples with narrow and broad molecular weight distributions indicated that the onset of non-Newtonian behavior occurred at a much higher shear rate for narrow-distribution polydimethylsiloxanes than for polydisperse polydimethylsiloxanes. A plot of reduced viscosity versus \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma \eta _0 {M \mathord{\left/ {\vphantom {M T}} \right. \kern-\nulldelimiterspace} T} $\end{document} gave two experimental master curves, one for polymer of narrow distribution and the other for polydisperse polymer. The experimental master curve obtained from the narrow-distribution polymer was found to fit the theoretical master curve derived from Graessley's entanglement theory. The viscosity-molecular weight relationship for the higher molecular weight polydimethylsiloxanes was found to be the same for both hydroxydimethylsilyl- and trimethylsilyl-endblocked polymers. However, at low molecular weight, the viscosity-molecular weight curve deviated from linearity because of the association of polydimethylsiloxanols, which apparently is not significant at higher molecular weights. The critical molecular weight of entanglement, Mc, was found to be about 30,000.
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  • 112
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1937-1953 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It has been considered for some time that the presence of birefringence in an oriented polymer must affect the light-scattering behavior. Previous analyses of this phenomenon are restricted to single-particle scattering. A more complete theory of the effect of birefringence on the scattering of light from correlated systems is presented. The measured scattering intensity is shown to be dependent upon the optical properties of the sample as well as the experimental technique and conditions.
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  • 113
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 2029-2032 
    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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  • 114
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 2039-2050 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Fujita equation relating molecular weight distribution to concentration of solution subjected to centrifugal forces in equilibrium proved to be an improperly posed problem in the Hadamard sense. Application of Tikhonov's regularizing functions leads to a good approximate solution of Fujita's equation. Such functions have been applied to a monomodal and a bimodal molecular weight distribution, and approximate results have been computed.
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  • 115
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 2095-2103 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Electron-microscopic texture and physical properties of a styrene-butadiene-styrene (SBS) block copolymer obtained by casting from toluene, carbon tetrachloride, ethyl acetate, and methyl ethyl ketone are discussed. Two peaks are observed in the mechanical loss (tan delta;) curve at -70 and 100°C which are attributed to segmental motion of polybutadiene and polystyrene, respectively. The polybutadiene peak heights are in the order of solubility in the solvent used; the polystyrene peak heights are in converse order. In addition to these peaks, a third peak is observed at 10°C for specimens cast from ethyl acetate or methyl ethyl ketone. A transition corresponding to this peak is also noticed in thermal analysis. It is proposed that aggregation of styrene blocks is relatively incomplete in specimens cast from solution in poor solvents.
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  • 116
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 2141-2151 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Low molecular weight poly(ethylene terephthalate) samples were crystallized isothermally at 120-245°C from both the amorphous state and the melt. Isothermal annealing of these polymers at 215°C provided polymers which exhibited multiple melting peaks in thermal analysis, referred to as form I and form II, as assigned by Bell and Dumbleton. In these samples the peak temperature of the form II melting endotherm and the average crystallite size are dependent on the temperature of initial crystallization. This result requires a mechanism for retaining some structural feature during the conversion from morphological form I to form II. DSC thermograms obtained at varying heating rates on samples showing only form II endotherms support the assignment of superheating as the cause of the shift to higher peak temperatures with increasing heating rate.
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  • 117
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1411-1412 
    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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  • 118
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1457-1465 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect upon seeding behavior of adding well characterized fractions has been studied, so as to assess the technique as a measure of small amounts of high molecular weight. The material available to us restricted the study to fractions with comparatively low average molecular weights. Self-seeding is shown to be an extremely sensitive measure of high molecular weight tails. Knowledge of the molecular weights concerned enabled estimates to be made of the weight of molecules involved in seeding. Instability of seeds has been observed, and is explained in terms of a particular amorphous crystalline “equilibrium” within the seeds.
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  • 119
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    Journal of Polymer Science: Macromolecular Reviews 4 (1970), S. 91-181 
    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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  • 120
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    Journal of Polymer Science: Macromolecular Reviews 4 (1970), S. 67-90 
    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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  • 121
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: It has been shown that the external parameters of eggs of the garden lizard, Calotes versicolor, are not suitable for assessing the exact developmental stages of embryos. In order to make use of this lizard's embryos for experimental work, a series of developmental stages has been characterized, using various morphological features.
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  • 122
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    Journal of Morphology 130 (1970), S. 467-478 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The cytology of the vitellogenic stages in the development of the oocyte of Drosophila melanogaster is described following an electron microscopic study of sections of plastic-embedded ovaries and single egg chambers. One of the first morphological manifestations of yolk deposition is an infolding of the plasma membrane of the oocyte and the abscission of membranous tubules and vesicles. The protein (alpha) yolk spheres originate along the oocyte periphery from membranous sacs to which are attached membranous tubules. It is assumed that the majority of the protein within the alpha sphere is synthesized by neighboring tubular, rough surfaced endoplasmic reticulum. The other organelles in the ooplasm are described, and their origin and possible roles in vitellogenesis are examined. The relative importance of intra- and extra-ovarian synthesis of yolk protein in different insect species is discussed.
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  • 123
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In order to further support the thesis that myoblast fusions lead to the formation of multinucleate myotubes during early amphibian development, prospective myoblasts from frog embryos (Rana pipiens; Xenopus laevis) were orthotopically and heterotopically transplanted into embryonic salamanders (Ambystoma maculatum; A. tigrinum). The stages employed ranged from gastrula to early tail bud. After the hosts had developed to more advanced stages, they were fixed, sectioned in the frontal plane, and prepared for histological observation. Of special interest in these xenoplastic combinations are the nuclear and cytoplasmic differences between anuran and urodele embryonic cells.In most cases, transplanted cells tended to form a tissue complex distinct from the host tissues. This naturally decreased the opportunity for cell intermingling and consequently reduced the chances for fusions between graft and host myoblasts. Thus, there was a correlation between the extent of dispersion of the transplanted cells and the frequency of chimeric myotubes. Nevertheless, in each experimental series, a number of multinucleate myotubes emerged consisting of nuclear and cytoplasmic components of both graft and host cells. These chimeric myotubes, which must have originated by multiple cell fusions of anuran and urodele cells, (1) retained their distinct nuclear differences, (2) displayed resorption of both anuran and urodele yolk platelets, and (3) contained cross-striated myofibrils. The function of these chimeric cells, their synthesis of myofibrils, and the apparent lack of free intermingling at the cellular level, are discussed.
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  • 124
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: (1) The frontal wall of the encrusting cheilostome, Watersipora arcuata is a one-layered, evenly perforated calcareous shield which subdivides the metacoel into two compartments, the perigastric coelom and the hypostega. These compartments communicate through four and six “intrazoidal septulae” at the corners of the frontal wall. (2) The frontal wall develops by apposition independently of the ectocystal epitheca. The ascus develops as an invagination of the epitheca. These observations are consistent only with the view that the frontal wall of this species is a cryptocyst. (3) The terms “tremocyst,” “olocyst,” and “pleurocyst” are poorly understood and ambiguously defined; they should not be used until more information is available. (4) The taxa Anasca, Ascophora, Ascophora Imperfecta, and Ascophora Vera are polyphyletic and should ge dropped and replaced by Silén's (1942) more natural taxa. Silén's Cryptocystidea should be enlarged to include Watersipora and related ascusbearing cheilostomes.
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  • 125
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A mass of pineal tissue has been observed associated with the habenular commissure and the apex of the pineal recess in the golden hamster. Previously, it had been thought that all of the pineal system in the hamster was located at the confluence of sinuses just beneath the skull. To distinguish the two components of the pineal system, that in the dural position is called the superficial pineal and the mass associated with the habenular commissure is called the deep pineal.
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  • 126
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    Journal of Morphology 131 (1970) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 127
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    Journal of Morphology 131 (1970), S. 195-209 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Ovarian changes during the reproductive cycle of the oviparous garden lizard (Calotes versicolor) are described. It ovulates from last week of June to first week of September but most often in July and August when the monsoon occurs. The number of eggs ovulated vary from 10 to 32. After ovulation, the ovaries are reduced in size. From October to May, the ovaries contain small pre-vitellogenic follicles, which increase in size in June when most of yolk deposition occurs. Several nuclei are seen in the ooplasm of pre-vitellogenic follicles; they are finally absorbed before yolk deposition starts. Follicular atresia generally occurs in follicles with polymorphic granulosae, in post-ovulatory ovaries. Presumably interstitial gland cells are formed by the hypertrophy of the theca interna cells of atretic follicles. Pre-ovulatory follicles have highly vascularized thecae and invaginations of the follicular epithelium. After ovulation, the follicle cells hypertrophy to form the luteal cell mass filling the follicular cavity. Fibroblasts, which appear to arise from the theca interna, invade the luteal cell mass and form septa. Capillaries occur in the luteal cell mass.
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  • 128
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The adventitia of the crayfish heart consists of about five layers of uninucleated cells that often contain large amounts of glycogen. The outer and inner boundaries of the adventitia are represented by amorphous, homogeneous layers that are rich in neutral and acidic carbohydrates.The myocardium has a trabeculated appearance, due to the branching and anastomosing of the muscle cells. Studies on the localization of various oxidative enzymes show that the mitochondria are contained principally in the cell periphery and the myofibrils in the cell core. Intercalated discs appear as dark, irregular lines that traverse the muscle cell at a level that corresponds to that of a Z band. The myocardial cells branch and radiate from loci that are formed either by a single stellate cell or by the common end-to-end junctions (intercalated discs) of several cells. The function of these loci is discussed.The local cardiac nervous system consists of a Y-shaped ganglionic trunk that contains eight large anterior and eight small posterior nerve cells.
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  • 129
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Eleven different adult anuran species were observed for the presence or absence of the lymphomyeloid complex (LMI-7). The organs were compared with those of Rana catesbeiana, which were recently studied extensively. Three species (Kassina senegalensis, Bufo boreas and Bufo powerii) did not have any LM organs; six species, i.e., Hypopachus pearsei, Phrynomerus bifasciatus, Rana montezumae, Rana pipiens, Hyla arborea and Bufo marinus, had jugular bodies (LM3); Hyla had also procoracoid bodies (LM7); Bufo marinus had, in addition to LM3 and LM7, another pair that did not have any counterpart to those already reported. The two remaining species possessed entirely different sets of LM organs. Xenopus melleri had large, paired hemal nodes attached to the ventral surface of the laterorostral portion of the hyoid cartilage on either side of the midline and a lymphoid follicle in the neighboring connective tissue. The hemal nodes had a nodular cortex surrounding a nonnodular medulla; no lymphatic sinuses were found inside nor lymphatic vessels associated with these organs. Hemisus marmoratum had paired, small corpora subdermale that were partially overlapped by the depressor mandibulae. These were small, thickly encapsulated, well-vascularized lymphoid bodies. The organs in the six species were characterized as thinly encapsulated, highly vascularized, non-nodular lymphatic tissues; some were lymphomyeloid. The LM organs of starved Rana pipiens and Rana montezumae, in contrast to those of well-fed ones, were smaller and without fat cells. Lymphomyeloid organs of hibernating Rana catesbeiana were no different than those of non-hibernating frogs.
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  • 130
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    Journal of Morphology 131 (1970), S. 397-415 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Pygidial defence glands, which are universal in Caraboidea, are paired, cuticular invaginations of the body wall.In Pterostichus madidus F. the glands contain a nauseous, corrosive secretion that can be discharged forcibly to deter attack by predators. The cells producing the secretion are of one type only. Electronmicroscopy shows that the ducts which drain these cells are not intracellular but are separated from the cell contents by a plasma membrane. The cuticular walls of the duct appear to effectively screen the cell from the disruptive effect of its final products of secretion. The duct-carrying epidermal cells which are modifications of the epidermis covering the rest of the gland support the ducts from the secretory vesicles to their entry into the central lumen of each secretory lobe. There is a single duct-carrying cell around each duct.
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  • 131
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    Notes: The cyclic changes in the testis of the five-spined stickleback Eucalia inconstans (Kirtland) were studied histologically. Specimens were trapped between July 1965 and July 1967 in a shallow pond near London, Ontario.A three-dimensional microscopic study showed a main vas deferens and a system of primary, secondary and tertiary tubules.The testis cycle was divided into seven arbitrary stages. Spawning takes place from mid-April to mid-July. This is followed by the division of primary spermatogonia which are located along the walls of the tubules, producing cysts of spermatogonia enclosed in connective tissue which is surrounded by a thin epithelium. Both primary and secondary spermatocytes develop within these cysts. Breakdown of the cysts occurs with the development of spermatids and spermiogenesis occurs while spermatids are free in the tubules. Over-wintering of mature sperm takes place. Development of mature sperm from primary spermatogonia takes about 156 days.Germinal epithelium is absent but primary germ cells are believed to be those cells occupying the spaces between the tubules of the testis. No tissue which might be implicated in hormone production was observed.Phagocytic invasion of the testis has been studied. Massive infiltration by phagocytes is believed to be responsible for the sudden increase in testis weight observed during spawning. These cells ingest sperm nuclei and groups of them have been observed in the lumen of the tubules and the vas deferens, probably on their way out of the body.
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  • 132
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    Notes: A correlation of autoradiographic and histochemical data indicates that the type I and II pulmonary epithelial cells are endodermally-derived; and, that the interstitial pulmonary cells are mesodermally-derived. Tritiated thymidine (T-H3) was found to be an excellent cell marker for in vivo developmental studies of mammalian (rat) lung. At a dose of 3 μc per gm (specific activity, 15.6-16.9 c per mM) maternal body weight, T-H3 crosses the placenta in amounts sufficient to effect heavy labeling of dividing cells. A partial placental barrier to T-H3 was found in late stages of development. Following an injection of T-H3 on day 16 of gestation, a higher rate of endodermal cell division was reflected by higher labeling indices and a steeper slope of the endodermal dilution curve as opposed to the mesoderm. This differential in labeling was maintained through the third postnatal day. Neonatal labeling patterns of the definitive cell types (type I and II pulmonary epithelial cells, interstitial pulmonary cells) reflected those of their germ layer precursors.Histochemical analysis of the developing rat lung demonstrated large accumulations of cytoplasmic glycogen in areas of rapid cell division (endodermal cells). As the mitotic rate decreased and cellular differentiation progressed, glycogen decreased; postnatally it is not a feature of mature pulmonary cell types.
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  • 133
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    Journal of Morphology 132 (1970), S. 47-67 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Study of a series of embryos showed that the spiroboloid leg arrangement (1 pair of legs on each of the first 5 segments) is derived from the typical leg arrangement (no legs on segment 1, 1 pair on segments 2 through 4, and 2 pairs on segment 5) by a shifting forward one segment of the first four pairs of legs.A careful re-examination of the literature, especially papers by Robinson ('07), Silvestri ('03, '49), Pflugfelder ('32), and Manton ('61), combined with observations of Narceus embryos led to the conclusion that (1) the anterior body segments are primatively single (2) the gnathochilarium is composed of only one pair of mouthparts, the diplopod head having but two gnathal segments, and (3) the intercalary segment is present in the Diplopoda.
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  • 134
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    Journal of Morphology 132 (1970), S. 101-107 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Several oxidative enzymes in the testis of the teiid lizard Cnemidophorus tigris were studied histochemically. The cells of the circumtesticular sheath (Leydig cell tunic) are functionally equivalent to Leydig cells of the interstitium on the basis of similar histochemical reactions for the five enzyme systems studied. Both groups of cells were positive for 3β-hydroxysteroid dehydrogenase, 17β-hydroxysteroid dehydrogenase, NADH diaphorase, NADPH diaphorase, and glucose-6-phosphate dehydrogenase. These results support the hypothesis that the circumtesticular sheath has endocrine function as indicated by its vascularity and its ability to catalyze histochemical reactions involving steroid biosynthesis.
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  • 135
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    Journal of Morphology 132 (1970) 
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  • 136
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    Topics: Biology , Medicine
    Notes: The organization of the corpora cardiaca and corpora allata of the female alfalfa weevil, Hypera postica, generally parallels that reported for other insects with extrinsic neurosecretory axons, intrinsic neurosecretory cells, and interstitial or glial cells appearing in both glands.Connecting the brain with the cardiacum are the extrinsic neurosecretory axons containing granules between 600 and 2200 Å. Granules with a diameter of up to 4000 Å are found in the intrinsic secretory cells of the corpus cardiacum.From the lobed corpus cardiacum, axons extend along a short nerve trunk into the ovoid corpus allatum. A characteristic of this gland is the presence of a layer of axons, ensheathing most of the corpus allatum and situated beneath an external basement membrane. These axons are believed to have their origin in the protocerebral neurosecretory cells. Although the c. allatum is known to be engaged in the release of hormonally active material, the cytoplasmic organization does not strongly reflect such activity.The glands of the diapausing weevil appear similar to those of the active weevil with a reduction in cytoplasm and a consequent folding of the plasma membrane.
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  • 137
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    Topics: Biology , Medicine
    Notes: Somites, along with adjacent neural tube and overlying ectoderm, were extirpated unilaterally from embryos of Chelydra serpentina. Mesoderm of three somites was removed from various levels. The operations included the last formed somite and were done on embryos with 12 to 22 pairs of somites. In practice it was found that ventromedial portions of the somites were not included in the extirpation. The animals were preserved before pigmentation became heavy. The cartilaginous skeleton was stained selectively.The extirpations resulted in depletions of ribs consonant with relating the second rib to the fourteenth somite. The somites behaved as mosaics; they did not reconstitute each other nor did they regenerate after partial extirpation. The rudiments for the ribs were separable from the rudiments of the vertebrae, the sclerotomes, and were found to arise from a more lateral portion of the somite.The scutes are ectodermal derivatives, which are held to be dependent upon underlying somitic mesoderm for their differentiation. The extirpations resulted in abnormalities and depletions of scutes.
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  • 138
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  • 139
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: Virgin mosquitoes were studied with the electron microscope. Spermathecal duct walls contain cuticle, epithelium, and a richly innervated spiral muscle; myocytes are linked by desmosome-like attachment plaques to the underlying epithelium. Periductal cells along upper portions of the ducts have a large secretory droplet within a highly irregular extracellular lacuna and are attached to a long secretory ductule through which finely granular material is delivered to the duct lumen and this enters the spermathecae. Basal gland cells of spermathecae have short ductules containing secretion in virgins. Secretory material in spermathecae of virgins does not form a complete internal membrane.
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  • 140
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    Notes: Neurosecretory cells of only one type (A, sub type A2) are seen in adult Melanoplus. Two groups of about 400 cells each are located dorsally in the pars intercerebralis medialis; four cells are located deep within the protocerebrum. We found no neurosecretory cells in other parts of the central or sympathetic nervous systems. In about 10% of the specimens, there was marked asymmetry in the location of the dorsal cell groups, with both of these groups and their axons located in one lobe of the protocerebrum.The nervi corporis cardiaci 1 cross-over in the corpus cardiacum, with the result that material produced by neurosecretory cells on one side of the brain is transported along axons that undergo two chiasmata to the corpus cardiacum of the same side.Stainable secretory material could be traced clearly from the cerebral cells to the corpus cardiacum, and even into the oesophageal nerves from the hypocerebral ganglion. However, stainable neurosecretory material is never present in the corpus allatum or along any of the nerves to this gland.
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  • 141
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  • 142
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: The integument and podia of the sea cucumber Thyone briareus were examined by bright field and electron microscopy. The epidermal surface was found to be covered by an acellular, PAS positive cuticle which appeared to be secreted by the underlying epidermal cells. Although the superficial portion of the cuticle contains numerous fine filaments, their ultrastructure bears no resemblance to collagen fibers. The epidermal cells are widely spaced and have long apical processes that extend along the under surface of the cuticle forming a contiguous epithelium. The apical expansions of the epidermal cells are attached to one another by means of septate desmosomes which may run continuously around all epidermal cells. Special attachment structures within these apical expansions appear to bind the cuticle to the dermis. The epidermal cells and their apical expansions are separated from the dermis by an 800 Å thick basement membrane. Granule containing cells in the upper dermis send processes up to the cuticle where they are bound to the typical epidermal cells by septate desmosomes. The abundant membrane bound granules of the cells enter villous-like processes which pass through the cuticle. The function of these cells may be to produce an adhesive material on the podia or they may be pigment cells.The thick dermis consists of a superficial zone, containing largely ground substance; a middle or laminated zone containing laminae of collagen fibers arranged in an orthogonal fashion; and a hypodermis consisting largely of ground substance and reticular fibers. Fibroblasts are abundant in the superficial dermis and between the collagen laminae. Wandering coelomocytes, or morula cells, accumulate between the collagen laminae and in the hypodermis. They may also become an integral part of the epidermis by forming septate desmosomes with epidermal cells. Morula cells contain highly specialized spherules whose tinctorial properties and electron microscopic appearance suggest that they contain protein and mucopolysaccharide.
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  • 143
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    Journal of Morphology 131 (1970) 
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  • 144
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    Notes: The present work describes the ultrastructure of the spinal cord in the regenerating tail of the lizard, Anolis. The distal growing region of the tail contains the advancing ependymal tube which is relatively devoid of axons but already contains channels between ependymal cell processes which anticipate their ingrowth. More proximally, fascicles of naked axons having their origin in the stump are present in the ependymal channels. Therefore, the pattern of fiber regeneration in the spinal cord is prescribed by the ependyma and not by the growing axons. Details of the ultrastructure of proximal, intermediate, and distal regions of the regenerate are reported. Particular attention is paid to the structure and differentiation of the ependymal cells and the relation of the ependyma to other glial cells, to nerve fibers, and to meningeal tissues.
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  • 145
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    Journal of Morphology 131 (1970), S. 253-275 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Submandibular glands of five adult female cats were examined by conventional electron microscopic techniques. All gland acini are mucous secreting and each acinus is capped with mucous secreting demilunar cells. Secretory product of demilunar cells is more electron lucent than that of acinar cells. The demilunes show intercellular tissue spaces and intercellular canaliculi whereas similar specializations are absent between acinar cells. Mitochondria and arrays of granular endoplasmic reticulum are more numerous in demilunar cells than in acinar cells. In acinar and demilunar cells secretory droplets first appear as enlarged Golgi saccules which subsequently become closely related to cisternae of the granular endoplasmic reticulum. Filamentous structures, interpreted as mucin molecules, are present in secretory droplets of acinar cells. Intercalated ducts are short, consisting of several junctional cells between acini and striated ducts. Striated ducts are long and tortuous and contain light cells, dark cells and basal cells. Light cells contain numerous membrane bound granules in their distal ends whereas dark cells show electron lucent vesicles in the same position. Basal cells contain a paucity of organelles and membrane plications but exhibit hemidesmosomes along their basal plasma membranes. Myoepithelial cells are abundant in relation to acinar and demilunar cells. Nerve terminals are present in some instances between acinar cells or between acinar and myoepithelial cells.
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  • 146
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    Journal of Morphology 131 (1970), S. 359-382 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Small swellings near the base of the radial vein in each fore wing of the green lacewing, Chrysopa carnea, resemble typical insect tympanal organs, but some important differences are apparent. The swellings are bounded dorsally and laterally by thick cuticle and ventrally by thin, membranous cuticle. The ventral membrane is formed by a single, thin sheet of exocuticle with flattened hypodermis internally, but lacks the tracheal component that forms part of the tympanum in the typical insect tympanal organ. The portion of the membrane beneath each swelling is rippled while proximally it is smooth. In contrast to typical insect tympanal organs, the swellings in C. carnea are largely fluid-filled since an unexpanded trachea runs through each organ. A distal and a proximal chordotonal organ composed of typical chordotonal sensory units are associated with each swelling. The distal organ contains from five to seven units while the proximal organ is composed of from 18 to 20 units. Each sensory unit is composed of three readily identifiable cells. Distally, an attachment cell unites with the membrane and is contiguous with the scolopale cell, which surrounds the dendrite of the bipolar neuron. On the basis of the morphological evidence, one would not expect these swellings to function as sound receptors. However, the results of physiological and behavioral experiments, presented elsewhere, show that these organs are receptors for ultrasound.
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  • 147
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  • 148
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    Notes: Six types of sense organs are present on the antennal flagellum of Ctenolepisma lineata pilifera: tactile hairs, trichobothria, thick-walled chemoreceptors, small thin-walled chemoreceptors and coeloconic chemoreceptors. The number, size and distribution on the antenna of each type have been recorded. The base of the tactile hair is more complex than is that of other insects examined earlier. Trichobothria, long, slender hairs that oscillate in a gentle puff of air, are an unusal feature in insects and especially so for the antenna. The two types of thin-walled chemoreceptors differ in shape, size and in the structure of their walls and internal parts. A pocket-like depression of the floor of the cavity in which the peg of the coeloconic sense organ is set has not been found in earlier studies. Its function is unknown.The axons from the sensory neurons extend along the inner surface of the antennal epidermis as a sheet of fibers lining the antennal lumen. Near the pedicel the axons leave the epidermis and join to form the antennal nerve.A few observations on sense organs on appendages other than the antennae and some notes on behavior are included.
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  • 149
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 541-554 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dilute solution parameters were determined for polymethylphenylsiloxamer fractions (5 × 104 〈 M 〈 1.5 × 106) in toluene, cyclohexane, and diisobutylamine (θ ≈ 30.4°C). The data are interpreted by the procedure suggested by Flory and Fox. Minor deviations from theory are noted. Polymers from both cis- and trans-cyclotrisiloxanes were investigated. The major portion of the work, however, was concentrated on fractions derived from the trans form. From the data obtained, a characteristic ratio of dimensions (r02/rof2)½ of 1.56 was determined. The hydrodynamic parameter Φ was determined to be (2.0 ± 0.3) × 1021. The appropriate model for the polymer is indicated to be the impermeable random coil with slight hindrance to rotation about backbone skeletal bonds.
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  • 150
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 595-603 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The adsorption of tritium-labeled sodium stearate and 35S-labeled sodium dodecylsulfate from aqueous solution on bent and on stretched polyethylene strips was directly measured. The amount of adsorption increased from 2.5 to 4.5 times on surfaces of various polyethylene samples stretched from 5.2 to 5.3 times the original length. For one sample, adsorption increased 8 and 2.5 times, respectively, on the convex and concave surfaces of a bent strip. Autoradiographs of the strips taken after adsorption revealed the appearance of both homogeneous and heterogeneous adsorption on the stretched surface of the polyethylene. The electron micrographs of the strips showed that many small fissures, about 1-5μ in length, formed on their surfaces after the strips were bent or stretched. Enhanced adsorption of the surface-active substance along these fissures was suggested. On the basis of these observations, it is proposed that in stretching or bending, fissures increase adsorption of the detergent, and the adsorption in turn promotes further development of fissures. Thus, bending and adsorption mutually promote the growth of fissures which finally result in failure of the polyethylene.
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 655-656 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
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  • 152
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 689-703 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reduced specific viscosity of poly(methacrylic acid) has been studied in ethanol-0.002N HCI solvent mixtures as a function of polymer concentration, alcohol concentration, and temperature. In addition, experiments were performed at different HCI concentrations and with KCI instead of HCI. Both intrinsic viscosity and Huggins coefficient were shown to undergo unusually strong variations. Two minima and two maxima could be demonstrated in intrinsic viscosity. The Huggins coefficient seems to show corresponding variations. The first minimum in intrinsic viscosity indicates that the coil volume has collapsed almost to an Einstein sphere. In this region the Huggins coefficient is extremely large (of order 102) and is controlled by coil association. It was shown that several forms of intramolecular interaction must be assumed to be competing to account for this behavior. The presence of HCI, particularly in the preponderantly aqueous phase, is required to suppress the polyelectrolyte effect. It is found, however, that the behavior of the solutions at relatively high ethanol concentrations is more sensitive to HCI content than is that of highly aqueous solutions. KCI can be used to replace HCI over most of the range. Increase in temperature shifts the turning points of the curves to lower alcohol concentrations. Some evidence has been found that the association constant giving rise to dimers increase with rate of shear. The importance of poly(methacrylic acid) as a chemically simple model substance for various biopolymer effects is stressed.
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  • 153
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 747-752 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Growth rates of G of low-melting spherulites in fractions of trans-1,4-polyisoprene have been measured. The data were analyzed by use of an equation, ln G = ln G0 - ΔF*/RTc, valid at temperatures close to the equilibrium melting point. Plots of ln G against a function of the critical free energy of nucleation ΔF* result in a family of straight lines having a common intercept, ln G0, which is independent of molecular weight. The slope of these lines is a measure of the interfacial free energy of the crystallites and increases with the molecular weight, reflecting increasing irregularity in the structure of the semicrystalline mass. Comparison of growth rates of low-melting and high-melting trans-1,4-polyisoprene indicates that G0 does not, to a first approximation, depend on the nature of the crystals growing from the melt. The temperature at which spherulites of the two crystalline forms grow at equal rates has been calculated.
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  • 154
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 489-497 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A quantitative theoretical calculation is made of the effect of birefringence of the surrounding medium on the light-scattering pattern from a two-dimensional anisotropic spherulite. The calculated modification of the light-scattering pattern is in accord with the prediction previously made on the basis of qualitative considerations and model experiments.
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  • 155
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 571-581 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal expansion of a butadiene-styrene copolymer filled with carbon blacks differing tenfold in mean particle size (HAF and MT) was investigated. The glass transition was unaffected by MT and was raised only 0.2°C for every 10 parts per hundred by weight of polymer of HAF black added. The coefficient of expansion of the polymer component of the composite in the rubbery region was substantially unaffected by either carbon black, but decreased markedly with increasing black loading in the glassy state. These results suggest that free volume is not altered appreciably by the presence of the filler in the rubbery state, but expands with decreasing temperature below Tg. The latter effect is explained by dilatation due to stresses set up around filler particles, arising from differences in the expansion coefficients of filler and polymer, which are not relieved in the glassy state. The near invariability of Tg and of the rubbery fected by adsorption of polymer segments on the carbon black surface. A conservative rough estimate indicates that restriction of segmental motion is confined to a 30 Å layer around the particles in which Tg is elevated by only 10°C.
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 637-642 
    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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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 653-654 
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    Keywords: Physics ; Polymer and Materials Science
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  • 158
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 705-712 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The intrinsic viscosity of poly(methacrylic acid) has been studied in mixtures of 0.002N HCI and a series of aliphatic alcohols. The behavior found previously with ethanol is shown to apply in the case of admixture with methanol, n-propanol, and 1,2-ethanediol. The intrinsic viscosity first drops to a minimum and then increases sharply to a maximum. With ethanol and n-propanol the maximum is followed by another minimum and maximum. With methanol and 1,2-ethanediol this effect is absent or much smaller. Methanol and 1,2-ethanediol are equivalent, molecule for molecule, in their influence on the intrinsic viscosity. With ethanol and n-propanol there are in addition one and two shoulders, respectively, in the passage from the first minimum to the first maximum. Good correlation of the data is obtained if alcohol concentration is plotted as the mole fraction of carbon atoms per OH group (in the alcohol). The first maximum in particular was shown to correspond to the point where the number of water molecules per alcohol in the solvent mixture equals the number of C atoms per hydroxyl in the alcohol. The shoulders and first minima were found to correspond to other simple ratios. This behavior reflects changes in alcohol-water structure. The maximum in the case of ethanol was found to be the most pronounced and ethanol seems to possess optimal properties from this point of view.
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  • 159
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 739-745 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dc conductivity of poly(sebacyl piperazine), a polyamide prepared from the secondary diamine piperazine, in which no N—H groups are present and no hydrogen bonding can occur, has been examined and compared with that of a normal 610 polyamide. The results obtained point clearly to the conduction in the 610 polyamide being electronic below about 100°C but probably involving protons as well as electrons above this temperature. This is largely consistent with the findings of earlier work and clarifies the nature of conduction below about 80°C as being almost certainly electronic where previously it was in doubt. A definite and sometimes marked hysteresis in the conductivity was observed with regard to raising and lowering the temperature of the polyamides. This is explained in terms of the space-charge polarization developed in the materials at higher temperatures and which becomes clearly evident in their dielectric behavior. This shows the importance of discharging specimens at a sufficiently high temperature before making conductivity measurements. The polarization is a bulk and not an electrode effect, and it will probably depend to a marked extent on the morphology of the polyamides.
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  • 160
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Measurements of the NMR second moment of a uniaxially oriented sample of polyethylene single crystals in the range of temperatures from -196°C to 130°C and its dependence on the alignment angle γ between the orientation axis (preferential direction of the molecular chains) and the NMR magnetic field are presented. The experimental results are discussed mainly with respect to the high temperature relaxation, called the α process, in polyethylene. They are compared to theoretical predictions made for a number of mechanisms of molecular motion in Part I of this work. Only one of the mechanisms considered is found to be in quantitative agreement with experiment, the mechanism here referred to as flip-flop motion. This consists of thermally activated rotational jumps of the crystalline chain segment between folds around its axis between two equilibrium sites in the lattice. Each rotational jump through 180° is accompanied by a shift of the molecule along its axis by one CH2 group. The discussion of the low-temperature relaxation of polyethylene, the γ process, is based partly on the above measurements and partly on measurements of second moments for unoriented polyethylene samples varying widely in morphology and noncrystalline content. The decrease of the second moment observed with these samples between -196°C and 20°C is taken as a measure of the intensity of the γ process. A linear correlation is found between the decrease in the second moment, designated ΔS, and the noncrystalline content, 1 - αm; this can be represented by ΔS = 1.4 + 22.1(1 - αm). It is shown that neither the crankshaft mechanism not the kink mechanism is able to account quantitatively for this result. The model of a chain end moving in a vacancy fails to adequately describe the angle dependence of ΔS in oriented polyethylene single crystals. The “sandwich model” of a polyethylene single crystal, in which the crystalline core is covered by noncrystalline surface layers, is in better agreement with observations.
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  • 161
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 813-813 
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    Keywords: Physics ; Polymer and Materials Science
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  • 162
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    Keywords: Physics ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: It is shown that the Hirai-Eyring model for the liquid state is capable of accurately describing the p, V, T behavior of liquid polymers in the temperature range over which measurements are now made, and below. Once the parameter choices necessary to accomplish the fit are made for a particular polymer, the excess thermodynamic functions (differences in properties, liquid less solid) are determined by the same parameters. Above the glass transition temperature Tg the volume, excess enthalpy, and square of the excess entropy are predicted by the model to be essentially linear with temperature, in agreement with experiment. Below Tg, these functions do not remain linear (as is usually assumed in extrapolating the equilibrium behavior to low temperatures), but instead they rapidly approach zero in a continuous way as the temperature is lowered. These remarks apply to glass-forming materials composed of small molecules, as well as to polymers. The “paradox” raised by Kauzmann is thus resolved, and the Gibbs-DiMarzio second-order transition appears to be unnecessary.
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  • 163
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 979-990 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have measured the relaxation modulus in the temperature range 150-220°C of two samples of poly(vinyl chloride) resin with different molecular weights. The data were treated by the principle of reduced variables to yield composite curves. The shift factors (aT) when plotted against reciprocal temperature gave good straight lines from which apparent activation energies were obtained. An apparent activation energy of 50 kcal/mole was obtained for both samples. A relaxation spectrum for each resin was calculated from the relaxation modulus data. These spectra showed a marked molecular weight dependence. The spectra were in the range characteristic of the terminal zone of the entanglement plateau. Zero-shear-rate viscosities were obtained from the integration of relaxation modulus plots. From extrapolation of capillary viscosity data it is shown that the viscosity of the higher molecular weight resin used in this study does not approach its zero-shear value until shear rates less than 10-3 sec-1 are reached. The effect of supermolecular flow units is briefly discussed.
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  • 164
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1015-1026 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An investigation of small-angle scattering produced by polarized light from stretched and annealed polymer systems containing spherulites yields information on the supermolecular transitions that occur during such treatment. A series of semicrystalline polymer systems (films, fibers) show that stretching leads to deformation of spherulites and subsequent transformation to an orientational supermolecular order. The size of the single element C2 of the supermolecular order in the direction of stretching, determined from the distance between the layer lines of the scattering pattern, is related to the diameter D0 of the initial spherulites by the relation C2 = KD0λs, where λ, is the draw ratio of the macrosystem and K is a parameter determining the deformability of the spherulites. For polyethylene at room temperature K is unity and for polychloroprene it is 1.2. Changes of C2 after annealing and restretching of the systems also obey this ratio.
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  • 165
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1073-1087 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A convenient pressure apparatus was designed for crystallization of high polymers under hydrostatic pressure up to 5000 atm. Melt crystallization as well as heat treatment under various temperatures and pressures was carried out on several polymers, and the effects of pressure on the molecular and crystal structures of the samples are discussed. Heat treatment of syndiotactic polypropylene under high pressure yields a new crystal modification rather than the previously known helix and planar zigzag modifications. Of the three modifications of poly(vinylidene fluoride), modification III was found as a high-pressure phase for specimens in the unoriented state, while modification I was obtained as the most stable one on heat treatment of oriented specimens under high pressure. Heat treatment under high pressure converts ordinary isotactic poly-4-methylpentene-1 with a lower density than the noncrystalline value, to a new crystal modification with higher density. As is reasonable, the dense modification is stable in a high-pressure range. For these three cases, the orientation of specimens was found to remain unchanged during the transitions, which must therefore occur in the solid state.
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1137-1157 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The scattering of light by a two-dimensional spherulite of radius R is calculated when there is disorder of optic axis orientation with respect to the radius. Special cases are considered when (1) the disorder occurs in the radial direction only, (2) the disorder occurs in the angular direction only, (3) there is combined radial and angular disorder, and (4) the optic axis makes a constant angle with the radius but there is disorder in the twist angle about the axis. In all of these calculations, a correlation function for disorder is defined and the scattering pattern depends on the ratio of the associated correlation distance to the size of the spherulite. With decreasing correlation distance, the azimuthal dependence of the scattering becomes less and there is a change in the variation of scattered intensity with scattering angles in a manner dependent upon the type of disorder.
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1187-1194 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The nonrandom orientational distribution of structural units, such as crystallites and chain segments, prevailing in an anisotropic bulk polymer sample can be represented fully by an orientation distribution function. Measurements of fluorescence polarization and wide-line NMR are, in principle, capable of yielding information on the moments of the distribution function up to the fourth order. This work presents the method of analysis required to determine these moments. For this purpose, the distribution function is expanded in a series of generalized spherical harmonies. The method is an extension of a similar technique previously proposed for analysis of x-ray diffraction data for determination of a complete crystallite orientation distribution function.
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  • 168
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1195-1209 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The strain-optical coefficient and relaxation modulus were simultaneously measured for high-density polyethylene at various temperatures ranging from 12 to 100°C. Not only horizontal but also vertical shifts were necessary to obtain smooth master curves by the application of time-temperature superposition. However, the relaxation modulus decreases with rising temperature while the strain-optical coefficient increases. This behavior indicates that the variation of the relaxation modulus and the strain-optical coefficient with time can not be explained by a decrease in crystallinity with rising temperature since a decrease in crystallinity usually causes a decrease in the strain-optical coefficient with time can not be explained by a decrease in crystallinity with rising temperature since a decrease in crystallinity usually causes a decrease in the strain-optical coefficient. It was emphasized that another explanation should be sought for the vertical shift in the time-temperature superposition of the time-dependence curves of the relaxation modulus and the strain-optical coefficient at various temperatures. The master curve of the strain-optical coefficient at various temperatures. The master curve of the strain-optical coefficient or the optical distribution function of relaxation times determined from it serve to distinguish the type and thermal history of the polyethylene.
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1291-1302 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Changes produced in γ-irradiated polyethylene by subsequent ultraviolet irradiation have been investigated by ESR measurements, ultraviolet spectroscopy, and viscometric determination of average molecular weight. The photoinduced changes depend on the wavelength of irradiation. Upon irradiation at wave length greater than 3900 Å, main-chain scission occurs by reaction of trapped allylic radicals: A reduction in molecular weight sndicated by this reaction was verified by fractionation experiments and molecular weight determinations.
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  • 170
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    Topics: Chemistry and Pharmacology , Physics
    Notes: A mathematical representation of the transformation of an orientation function between two sets of Cartesian coordinates is discussed in terms of a series expansion of the distribution function in generalized spherical harmonics. A general procedure for calculating the mechanical anisotropy of a single-phase system (a polycrystalline material) from the orientation of its structural units and the intrinsic mechanical anisotropy of the structural unit is discussed in relation to the transformation of the orientation distribution function, i.e., mutual conversion of the coefficients in the expansion of the distribution function between the two sets of Cartesian coordinates. The procedure is extended to a two-phase systems (semicrystalline polymers) containing structural units composed of crystalline and noncrystalline materials in three different geometrical arrangements.
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1387-1393 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(ethylene adipate), poly(ethylene suberate), and poly(ethylene sebacate) were synthesized by a modified ester interchange procedure. Polydispersity was reduced and low molecular weight material removed by fractional crystallization. Samples of 50-60% crystallinity were prepared by bulk crystallization and annealing. Melting points and amorphous densities were obtained by dilatometry. Melting points were 7-12°C higher than previously reported. Heats of fusion were measured by differential scanning calorimetry and extrapolated to 100% crystallinity by using measured amorphous densities and recently redetermined crystalline densities. Entropies of fusion were calculated and separated for the first time into volume expansion and conformational contributions.
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1057-1072 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dielectric properties of poly(vinylidene fluoride) have been studied in the frequency range 10 Hz to 100 kHz at temperatures between -196 and 150°C. Three dielectric relaxations were observed: the α relaxation occurred near 130°C, the β near 0°C, and the γ near -30°C at 100 kHz. In the α relaxation the magnitude of loss peak and the relaxation times increased not only with increasing lamellar thickness, but also with decrease of crystal defects in the crystalline regions. In the light of the above results, the α relaxation was attributed to the molecular motion in the crystalline regions which was related to the lamellar thickness and crystal defects in the crystalline phase. In the β relaxation, the magnitude of the loss peak increased with the amount of amorphous material. The relaxation times were independent of the crystal structure and the degree of crystallinity, but increased slightly with orientation of the molecular chains by drawing. The β relaxation was ascribed to the micro-Brownian motions of main chains in the amorphous regions. The Arrhenius plots were of the so-called WLF type, and the “freezing point” of the molecular motion was about -80°C. The Cole-Cole distribution parameter of the relaxation time α increased almost linearly with decreasing temperature in the temperature range of the experiment. The γ relaxation was attributed to local molecular motions in the amorphous regions.
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1127-1136 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The theory for scattering of light from films in which the orientation correlation between two scattering elements depends upon the angle β between the optic axes and the vector connecting the two elements is extended. A delta-function type dependence is assumed in which the correlation is strongest when β equals some preferred value β0. Calculated results of scattered intensities are shown to be similar to experimental observations.
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1159-1168 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: ESR and electrical conductivity measurements have been made on a recently prepared polymer, polypropiolamide. The polymer was obtained as a fine powder which exhibited a nearly Lorentzian line with a width between derivative maxima of 5.2 ± 0.1 gauss and a g value of 2.0036 ± 0.0005. The signal intensity increased with increasing molecular weight. The signal was retained in a dilute solution in formic acid with a slight narrowing of the line. Permanent changes were produced in the spectra at room temperature by heat treatments of the polymer at temperatures up to 800°K. The changes were similar for samples sealed in tubes containing air, dry nitrogen gas and a vacuum of 3 × 10-5 mm of Hg. Spectra obtained at temperatures up to 500°K showed no dependence on the presence or absence of oxygen in the ambient atmosphere. The deresistance of pressed pellets of the polymer was measured in the temperature range 450°K to 525°K, and the results were described by the relation R = R0cE/kT. The activation energy E had a value of 1.2 ± 0.2 ev and the resistivity at 500°K was approximately 1013 ohm-em. The ESR signal is attributed to an intrinsic property of the polymer which is associated with a conjugated bond system along the polymer backbone. Neither the activation energy nor the magnitude of the resistivity suggest that the delocalized electrons associated with the conjugated bond system have produced unusual electrical characteristics in the polymer.
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1235-1237 
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    Keywords: Physics ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
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  • 176
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    Notes: Critical miscibility data obtained from measurements of phase-volume ratios have been used to calculate the concentration dependence of the pair interaction parameter for the system polystyrene-cyclohexane. The measured temperature and concentration ranges are 11-30°C and 4-18% polymer by weight, respectively. With the Gibbs free energy of mixing expressed in polymer segment mole fractions, x*, the pair interaction parameter is g(x*, T) = 0.4961 + 71.92/T + 0.2312x* + 0.0750x*2. In a polymer volume fraction formulation the parameter is g(ϕ, T) = 0.4099 + 90.65/T + 0.2064 ϕ + 0.0518 ϕ2, which approximates to χ(ϕ, T) = 0.2035 + 90.65/T + 0.3092 ϕ + 0.1554 ϕ2. Comparison of the temperature and concentration dependence with that obtained by other authors shows very good agreement, even when extensive extrapolations in temperature and concentration are applied. The present function is believed to be the most accurate. Solutions of mixtures of two narrow-distribution polystyrenes in cyclohexane show separation into three liquid phases under the exact conditions predicted by theoretical calculation with the present pair-interaction function.
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1279-1289 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Selenacyclobutane (trimethylene selenide) readily undergoes photochemical reaction to give polymeric products. Also, the material polymerizes rapidly when the polycrystalline solid film liquifies on a salt substrate in vacuum. Upon polymerization of the sample, infrared and Raman spectra exhibit profound changes which definitely establish ring cleavage. The Raman spectra of the polymer reveal strong C-Se stretching peaks but little or no scattering in the region of Se-Se stretching, strongly suggesting that the polymerization process proceeds in a regular head-to-tail fashion. An EPR study of the monomer exposed to ultraviolet radiation at -180°C supports this fact, since the resulting spectrum is indicative of an intermediate radical species, (CH2CH2-CH2Se)n., where n is sufficiently large that the terminal electrons do not interact. No triplet spectra were observed. Molecular oxygen apparently plays an important role in the polymerization kinetics, since it is found that degassed samples of the substance, in contrast to those which have not been degassed, polymerize rapidly even under room illumination. Freezing-point depression measurements fix a lower limit to the average molecular weight of the polymer at 2700 (n = 23 monomer units).
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of long-and short-chain branching in polymer molecules on gel-permeation chromatographic (GPC) separation is discussed. The calculation of calibration curves for branched polymers is developed from the universal calibration technique based on the hydrodynamic volume concept and previously established relationships for the effect of branching on molecular dimensions. Typical calibration curves are shown for different branching models and degrees of branching. As branching increases, the curves are shown to converge. Methods of characterizing branching and molecular weight distributions of franctions and whole polymers from GPC and intrinsic viscosity data are presented.
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 2177-2186 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Branched polyethylene, melt-crystallized in commercial fabrication processes, cleaves into two layers when exposed to a prolonged “chemical filling” treatment (i.e., formation of filler in situ by interdiffusion of two reactive permeants). Cleavage has been observed in film and blown bottles. With film, progressive changes in experimental conditions from one sample to another, shifted the cleavage plane from near the surface to deeper lying planes. Separation of a thin surface layer requires more filler deposit than does separation into layers of more equal thickness. These observations suggest that a well defined layer structure may exist in branched polyethylene and that cohesive bonding is stronger between layers near the surface of the film than it is between deeper lying layers. Linear polyethylene showed slight layer separation after prolonged chemical filling, but clean cut separation of large areas was not achieved. This behavior may indicate that the cohesive bonding between layers is much stronger in linear polyethylene than in branched polyethylene.
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1797-1801 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The current theoretical treatment of diffusion of gases in glassy polymers is based on the “dual sorption” model, but also includes certain other important assumptions, at least some of which cannot be fully justified a priori. They require experimental validation, which, however, is not possible by the procedures used or proposed so far. Methods suitable for this purpose are discussed here.
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1773-1786 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The temperature dependence of the crystallinity of bulk polyethylene is calculated in terms of branching (methyl or ethyl side groups on the chain). In the model, the chains are approximately parallel and they pass through alternating amorphous and crystalline layers forming a periodic structure. The crystalinity and the thicknesses of the layers are determined by minimization of the free energy. The theory shows that the temperature at which the polymer begins to crystallize is lower than the melting point of pure polyethylene and that the thicknesses of the layers becomes smaller as the temperature decreases.
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1837-1839 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1831-1835 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Average polymer segment densities and thermodynamic properties of polymer adsorbed at liquid-solid interfaces were computed by extension of the polymer adsorption theory of Forsman and Hughes. Expressions were derived for the total free energy of adsorbed polymer chains by using the Flory-Huggins theory to represent free energy of mixing. A square-well potential was used to represent segment-surface interaction, and configurational entropy was calculated from the probability density function for the radius of gyration of random-flight chains. For each specified amount of surface coverage the free energy of the adsorbed polymer was minimized by varying the density of segments normal to the adsorbing surface and using a modified gradient search algorithm on a digital computer. Two different segment densities were considered, and they both gave qualitatively the same results. The two densities were (1) the sum of two Gaussian distributions and (2) a two-step density distribution. Isotherms were then calculated by equating the partial molal free energy of polymer at the surface to that of polymer in bulk solution for each specified amount of surface coverage. The results showed that for the initial region of the isotherms the distribution of polymer segments normal to the surface consisted of a high-density layer adjacent to the surface and a low-density “tail” extending far out into the solution. At higher amounts of adsorbed polymer, i.e., in the general concentration range of the pseudo-plateau, the tail of the polymer density distribution was predicted to thicken, and a single Gaussian distribution best described the segment density. Predicted adsorptions were in good agreement with reported experimental values.
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  • 184
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1897-1908 
    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 molecular weight distribution on the viscoelastic properties of “entangled” polymers has been examined with blends of narrowly distributed polystyrene and broadly distributed polydimethylsiloxane. It is shown that blending laws established for nonentangled polymers do not apply to high molecular weight systems. The steady-state shear compliance of a blend is examined as a function of its molecular weight and the molecular weight of its components, and an approximation is given for the longtime viscoelastic response of entangled blends.
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  • 185
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    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1927-1935 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The storage (J′) and loss (J″) shear compliances have been measured for two random copolymers of styrene and n-hexyl methacrylate with styrene contents of 18% and 30% (by weight) in the frequency range 45-4400 Hz and the temperature range 31-107°C. The data at different temperatures were combined by the method of reduced variables, and the WLF coefficients were calculated from the temperature shift factors by the method of Pierson and Kovacs. The data were compared with earlier data for the two homopolymers. The thermal expansion coefficient of the fractional free volume, and the free volume at the glass transition temperature, varied monotonically with composition, but the fractional free volume at a reference temperature of 100°C appeared to pass through a maximum as a function of concentration. Comparison of isothermal plots of J′ at 100°C, plots of the relaxation spectrum at 100°C, the monomer friction coefficient and its temperature dependence, and isochronal plots of the storage shear moduls at 100 radians/see all show that the properties of poly(n-hexyl methacrylate) are very slightly affected by incorporation of 18% styrene and only moderately affected by 30% styrene. By contrast, comparison of styrene-butadiene rubber with 1,4-polybutadiene shows a very large effect of incorporation of 23.5% styrene. These differences may be associated with local packing relations of the comonomer residues and suggest that copolymer properties cannot be readily predicted from those of the component homopolymers.
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  • 186
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    Journal of Morphology 130 (1970) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 187
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In further consideration of the lizard ear, the fine structure of the cochlea has been investigated and related to auditory sensitivity in members of the family Cordylidae. The ear of this group of lizards is unusual in that a tectorial membrane is present only in a modified and seemingly vestigial form, and this membrane makes no connections with the auditory hair cells. These cells are provided instead with a series of sallets, small bodies extending in a single row through the dorsal and middle regions of the cochlea, where they rest upon the tips of the ciliary tufts and evidently bring about a stimulation of the hair cells because of their inertia. At the ventral end of the cochlea this line of sallets ends, and here is a single, relatively enormous structure, the culmen papillae, that serves a similar purpose for a large group of hair cells. Consideration is given to the manner of stimulation of the auditory sense cells in these species in relation to others with the usual arrangements involving connections between the ciliary tufts and a tectorial membrane.Included also is a study of a species of Gerrhosaurus, which some have included in the cordylid family and others have placed in a family of its own. The cochlear structure in this species is similar to that of the cordylids in many respects but differs in the ventral region, where instead of the culmen there is a heavy tectorial plate, similarly covering a large number of hair cells but connected to a tectorial membrane.The functioning of these ears is assessed in terms of the cochlear potentials, and is found to vary with species from better than average to excellent in comparison with other lizards investigated. The structural differentiation also is of fairly high degree, and hence it appears that ears without tectorial connections, or with such connections only in a limited region of the cochlea, can perform in a highly serviceable manner.
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  • 188
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The black carpet beetle, Attagenus megatoma (Fab.), has been reported to exhibit negative phototaxis immediately after emergence. In later adult life, after the period during which most oviposition has occurred, the beetles are found to be photopositive. The compound eyes of one-day-old (Post-emergence) and nine-day-old (Post-ovipositional) female beetles were studied by electron microscopy and a number of strong differences were found between eyes at the two ages. The corneal facets of one-day eyes had the form of convex-concave lenses, while those of nine-day beetles were double-convex lenses. The primary and secondary pigment cells of young eyes were large and contained much endoplasmic reticulum and little accessory pigment. In the older eyes the pigment cells were reduced and contained much pigment, the proportion of endoplasmic reticulum being greatly reduced by comparison with the one-day eye. The cross-sectional area of the rhabdom was greater in the older eye.The possible relationships between age-related changes in eye morphology and behavioral changes during the same period are discussed.
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  • 189
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Desert-dwelling male Uma notata, U. inornata and U. scoparia were autopsied monthly from 1959 through 1962. Seasonal changes in the histological morphology of the testes were observed. A series of eight stages, indicating these changes in spermatogenic activity, was established. These categories arbitrarily divide a continuous process into several recognizable stages.Present evidence indicates that male breeding cycles can be determined rather precisely by examining any of several reproductive features. Data from several sources reveal that the male breeding season of U. scoparia is shorter than that of U. notata or U. inornata. Nevertheless, the testes of all three species appear to function reproductively during the hottest month of the year. Possible explanations for this ability are suggested.Little difference was observed in the time the seminiferous tubules of U. notata testes reached full breeding condition (stage 6) following dry winters. This is in contrast to the time motile sperm appeared at the cloacal end of the vas deferens in these animals. Thus is appears that the major cause of postponement in male U. notata reproductive activity following dry winters is due to a delay in sperm reaching the vas deferens rather than a retardation in sperm production.
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  • 190
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    Journal of Morphology 130 (1970), S. 297-313 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Four types of haemocytes may be distinguished in Rhodnius adults, based on their fine structure. The plasmatocytes are most active in the repair of an integumental wound. They contain dens homogeneous granules whose contents become less dense in response to wounding until microtubules about 150å in diameter are distinguishable. The significance of these changes is not yet known. Tight and intermediate junctions, and septate desmosomes appear between haemocytes which have accumulated in an excision.
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  • 191
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    Journal of Morphology 130 (1970), S. 337-351 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effect of aging on the rat submandibular gland was studied by using ultrastructural, ultrastructural cytochemical and biochemical techniques. There was an age-related clumping of the nucleolar-associated and peripheral chromatin in many of the acinar cells and a decrease in the number of cisternae of rough endoplasmic reticulum. Many aged acinar cells were binucleated. There was also an age-related increase in pigment granules throughout the gland. These membrane bound granules consisted of a lipid droplet and an associated dense cap which had a granular matrix and pigment droplets. The lead capture method for acid phosphatase activity demonstrated that activity was associated with the granular matrix of the dense cap. These results were correlated with the age-related increase in acid phosphatase activity as determined by colorimetric procedures.There was an age-related increase in the number of cells characterized by small secretory granules. These cells were found as part of the intercalated ducts or at the junction of the duct with the acini. Oncocytes were also found as part of the parenchyma of the aged submandibular gland. These cells were characterized by the pleomorphic mitochondria that fill their cytoplasm. Occasionally, cells that possessed extraordinary numbers of mitochondria and small secretory granules were also observed.The determinations of total DNA and RNA revealed and age-related decrease in RNA while there was no significant change in the concentration of DNA.
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  • 192
    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 cardiac ganglion of Limulus polyphemus (L) was examined by reconstructions from stained serial sections. This ganglion is composed of two distinct parts: a fiber tract extending the entire length of the heart and a cellular portion underlying the fiber tract. The cellular portion extends continuously from the third pair of ostia to the posterior terminus of the heart. The mean number of ganglion cell bodies is 231. Most of the ganglion cells are located among the glial elements of the cellular portion. The greatest density of cells is found in segments 5 and 6. Six cell types are recognized: (1) large pigmented unipolar cells approximately 120 μ in diameter with distinct connective tissue capsules around them; (2) large pigmented bipolar cells approximately 120 μ in length which are also encapsulated; (3) pigmented multipolar cells approximately 80 μ in diameter which are free of capsules; (4) small pigmented bipolar cells approximately 40 μ in length which are encapsulated but which are found exclusively within the fiber tract; (5) non-pigmented multipolar cells approximately 30 μ in diameter which are found scattered among the connective tissue elements of the cellular portion; and (6) small non-pigmented cells approximately 10 μ in diameter which are found within the unipolar cell capsule and scattered among the connective tissue elements of the ganglion.The variability in cell numbers and the random location of cells points toward non-specific anatomical connectivity between elements of this ganglion.
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  • 193
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Development of the secondary palate in Swiss white mouse embroyos was studied from age nine-and-one-half days in utero to the stage of mesenchymal coalescence in the secondary palate (approximately fifteen-and-one-half days). The greatest changes observed occur in the mesenchyme. At early stages, mesenchymal cells underlying oral ectoderm of the head are few and only occasionally contact the ectoderm. Electron micrographs show large intercellular spaces between the ectodermal cells. As embryogenesis continues, the mesenchymal cells become more numerous, closer to each other and closer to the epithelium. Just prior to horizontal transposition of shelves, the mesenchymal cells spread farther from each other and from the palatal epithelium and epithelium of the palatal tip becomes stretched. Ultrastructurally the intercellular spaces between epithelial cells of the palate tip have become much smaller. Some mitochondria in some epithelial cells are swollen and have clear matrices and distorted cristae. The shelves become horizontal and meet in the midpalate. Cells with degeneration bodies are seen in the epithelial seam. The seam undergoes autolysis and is replaced by mesenchyme. The morphological changes described, particularly in the mesenchyme, may play an important role in determining the effect of various teratogens at different stages of palatal development. The changes in both mesenchyme and epithelial cells in the later stages may constitute part of the process of preparing shelves for fusion as postulated by Pourtois ('66).
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  • 194
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    Journal of Morphology 130 (1970), S. 501-509 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Although there are many reports of tooth replacement patterns in lower vertebrates, few show the range of pattern to be found in a number of similar aged specimens of one species. Fifteen specimens of Caiman sclerops, head length 4-5 cms, were examined by a radiographic technique and their tooth replacement patterns analysed. Whole head radiography and dissected head radiographs were compared and the resulting tooth replacement waves were found to be comparable. Wave replacement (sensu Edmund, '60) in odd and even tooth positions in the tooth row was observed in all the specimens examined. Whereas most waves passed in a cephalad direction, wave reversal (caudad) was also observed, particularly in the anterior parts of the jaws. In some specimens simple alternation in tooth replacement was observed, particularly in the mid-portion of each quadrant. The smooth, age-related change-over from cephalad to caudad demonstrated by Edmund ('62) in captive Alligator mississippiensis was not observed in wild specimens of Caiman sclerops.
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  • 195
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    Journal of Morphology 131 (1970), S. 89-101 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Retrogressive analysis of the cn gene effect has been performed on crooked neck dwarf chick embryos between stages 28-38 (5-12 days). The phenocritical stage of mutant embryos studied is stage 29. Histolytic degeneration of neck tissues is first recognized by the appearance of localized degenerate nuclei in the tracheal mesenchyme. Pleiotropic autolysis of the embryonic thymus, loose mesenchyme and the ventral neck tissue is also observed. Histolysis occurs in a caudocephalic gradient in all cn-affected embryos. The degenerative effects in crooked neck dwarf embryos vary in their intensity, but the pattern of autolysis seems constant. Histological observations provide some explanation for “escapers,” homozygous lethal embryos known to survive until hatching. A mechanism for surviving developmental crises in cn embryos is proposed.
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  • 196
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    Journal of Morphology 130 (1970), S. 187-206 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A histological study of the spleen of the Brown-headed cowbird, Molothrus ater, is presented.One of the most striking differences from the mammalian spleen is the lack of trabeculae and of smooth muscle in the capsule which would suggest that the spleen is not an organ of storage or pumping of blood. Without trabeculae to foster the close association of the major arteries and veins, these vessels take separate courses. Their support is provided by elaboration of the collagenous and reticular fibres of the stroma.A peculiar ovoid structure, the ampulla, carries the blood from the terminal arterioles of the white pulp to both the sinusoids and the reticular cords of the red pulp so that both open and closed circulations are seen but the open circulation predominates. The ampulla has perforated walls consisting of a simple cuboidal endothelium surrounded by a dense reticular sleeve. Leucocytes were seen passing through the holes in the walls of the ampullae by diapedesis. It is suggested that the ampullae may be contractile and act as sphincters controlling the flow of blood through the spleen.The major functions of the spleen appear to be haemopoiesis, production of antibodies, and filtration of blood.
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  • 197
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    Journal of Morphology 130 (1970) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 198
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ultrastructure of the gut regions of the marine filter-feeder Phoronis vancouverensis was correlated with enzyme activity as revealed histochemically. The oesophagus, proventriculus, and stomach epithlia showed intense esterase and acid and alkaline phosphatase activity. The staining reaction was confined primarily to small globules in the apical cytoplasm of the epithlial cells. Electron micrographs of the same regions showed a high incidence of zymogenlike granules, with a corresponding abundance of ribosomes and of rough endoplasmic reticulum. Also, the proventricular and to a lesser extent the stomach epithelia were found to contain a large number of lipid bodies. This was confirmed with positive Sudan IV staining for fats.The intestinal region of the gut was found devoid of esterase and phosphatase activity. The epithelial surface in this region was found elaborated into microvilli. The entire gut is ci iated. A new paired-cilium apparatus is described in this phylum.From these findings Phoronis vancouverensis is concluded to be suitably adapted to its continuous filter-feeding existence, with the anterior gut epithelia synthesizing hydrolytic enzymes for release into the lumina of the proventriculus and stomach. Subsequently, in the hindgut the products of initial extra-cellular digestion are absorbed via the microvilli and treated intracellularly within the intestinal epithelium. The proventriculus is further thought to function in lipid absorption and storage. The presence of chromaffin-like granules observed in some proventricular and intestinal epithelial cells suggests that digestion in this phylum may in part be under neurosecretory control.
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  • 199
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    Journal of Morphology 131 (1970) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 200
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    Journal of Morphology 131 (1970), S. 383-395 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In Drosophila melanogaster embryos cuticle formation occurs between 12 and 16 hours of development at 25°C. The formation of the cuticulin and the protein epicuticular layers is simultaneous in the hypoderm, the tracheoblasts, and the fore- and hindgut cells. The cuticulin forms as a dual lamina, aggregating from granules secreted by the hypodermal cells. This is followed by the formation of a granular protein epicuticle and finally by the secretion of a mixed fibrous and granular endocuticle.All secretory cells are relatively simple in their ultrastructure. The secretory process is a membrane phenomenon, occurring at the tips of hypodermal microvillae on cells at the surface of the embryo and on those hypodermal cells lining the lumen of the fore- and hindgut. It also occurs along the entire surface of the tracheoblast lumen as well as on the outer surface of those cells which form exoskeletal chitinous setae. The process involves a specialization of the plasma membrane with the formation of secretory granules intracellularly beneath the membrane and the extrusion of these granules through the membrane to the outside where final cuticle formation occurs.
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