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  • General Chemistry  (1,886)
  • SPACE RADIATION  (811)
  • Chemical Engineering  (650)
  • Cell & Developmental Biology
  • 1970-1974  (3,726)
  • 1965-1969
  • 1972  (2,005)
  • 1970  (1,721)
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  • 1970-1974  (3,726)
  • 1965-1969
Year
  • 1
    Electronic Resource
    Electronic Resource
    Characterization of polymer composites by electron microprobe analysis (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 34-40 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper describes the use of an electron microprobe for characterizing filler and polymer dispersios in polymer composites. Examples described are: filler distribution in sisal reinforced polyester; aggregation of titanium dioxide in glassreinforced polyester; mixing behavior in a blend of silicone rubber, natural rubber, and titanium dioxide; and distribution of silica in a low-gloss paint on an ABS plastic surface. The limitations of electron microprobe analyses for qualitative and quantitative studies, the use of back scattered electrons for surface topography, and techniques for preparing specimens are mentioned.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120106
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  • 2
    Electronic Resource
    Electronic Resource
    Heat transfer to molten polymersThe author wishes to acknowledge the Society of Plastics Engineers for allowing the use of tabulated temperature and flow data that were published in Polym. Eng. Sci. The author further wishes to thank the Naval Research Laboratory for supporting the conduct and publication of this work. (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 140-149 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The processing of polymers and other solids, such as waxes and acids, often requires the melting of a bulk or granular charge before its introduction into a process stream. Two approximate techniques for relating heat transfer and melting rates are presented here and the shielding effect of the melt formation is considered. The heat available for melting is sometimes remarkably decreased by the heat carried away by the flowing melt. Means are presented for quantitatively determining the shielding or sensible heat effect of the film. The thermal efficiency of the phase transformation process is discussed, and the effects of heat loss to both increased bulk temperature of the flowing melt and conduction in the solid are demonstrated. A comparison with experiment is made using temperature and melt flow data for polyethylene and polyoxymethylene. Heat transfer coefficients and melting correlations useful in practice are presented.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120211
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  • 3
    Electronic Resource
    Electronic Resource
    Polybutadiene/polystyrene interpenetrating polymer networks (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 101-108 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Interpenetrating polymer networks (IPN's) of polybutadiene (PB) and polystyrene (PS) were prepared using both random (containing 36% cis, 55% trans, and 9% 1,2 vinyl) PB and high-cis PB. For both series, a wide range of PB/PS compositions were synthesized. Using samples stained with osmium tetroxide, electron microscope studies revealed an irregular cellular structure of a few hundred Ångstrom diameter with the first component, PB, making up the cell walls. The size of the cells was found to depend on the PB crosslink density for the random materials. Modulus-temperature data revealed two distinct glass transitions, confirming the microscopy finding of two phases. However, the transition temperature and transition slope varied with composition, and with the microstructure of the polybutadiene, giving evidence of significant molecular mixing. Stress-strain data on the IPN's showed that materials rich in PB behave like self-reinforced elastomers. Charpy impact resistance experiments on materials rich in PS indicated values of 5 ft-lb/in. of notch, which compares well with graft-type polyblends of similar PB/PS composition. The results were interpreted in the light of the recent theoretical work of Bragaw, who considered the importance of the distances between domain boundaries with respect to crack acceleration mechanics. Although the IPN's considered herein exhibited somewhat less than the predicted optimum phase dimensions, the arrangement of the domains is different from ordinary impact resistant plastics.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120205
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  • 4
    Electronic Resource
    Electronic Resource
    Growth of fatigue cracks in polycarbonate (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 193-198 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The rapid increase in the rate of application of thermoplastics in engineering design problems and the interest in the structural use of these materials have resulted in the requirement of comprehensive information about the behaviour of thermoplastics when subjected to cyclic loading conditions. In addition to the “total fatigue life” data already available for many materials, attempts have been made to analyse the crack initiation and steady crack growth processes and determine the effects of parameters such as mean load, frequency and crack geometry on the rate of crack propagation. The results of an investigation of these aspects of fatigue crack growth in a brittle thermoplastic, polymethylmethacrylate (PMMA), have already been reported. In this paper, the results of a test program devised to study the behaviour, at room temperature and in air, of a polycarbonate, (PC), under similar loading conditions, are presented. Fracture Mechanics concepts have been used to analyse the results. It was found that a relationship of the form ȧN = β λn already shown to predict the cyclic fatigue crack propagation rate in PMMA, is also applicable to polycarbonate. However, when the effects of frequency and loading rate were studied, it was found that after the magnitude of parameter K̇( = ΔK/half the periodic time) exceeded 4000 lbf in. -3/2 s-1, the influence of the mean level of stress intensity factor, Km, became negligible in comparison to the effect of ΔK.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120306
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  • 5
    Electronic Resource
    Electronic Resource
    Cold rolled ABS. Part 1: The effect of rubber particle size on the tensile properties of ABS before and after cold rollingPresented in part to the Polymer Division, The American Chemical Society, Washington, D. C., September 1971. (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 213-218 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of rubber particle size on the tensile properties of rolled and unrolled acrylonitrile-butadiene-styrene has been studied by considering model systems consisting of mixtures of a small particle (0.1 micron diam) rubber, S, and a large particle (0.56 micron diam) rubber, L, in an SAN matrix. Before rolling, tensile toughness is characterized by crazing. While both rubber induce matrix crazing, ABS systems containing only the S rubber exhibits early failure due to crack formation, before crazing is propagated very far along the tensile axis. The inefficiency of the small particle rubber is interpreted in terms of high composite yield stress and insufficient distance between particles to allow craze branching. The efficiency of the small particle rubber is improved via the addition of a small amount of large particle, L, rubber to the composite or by a slight degree of cold rolling, both of which enhance craze propagation in the tensile direction. With further rolling, the tensile deformation mode changes from one of localized crazing, which is propagated, to one of uniform deformation, which occurs without crazing.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120310
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  • 6
    Electronic Resource
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    Uniaxial extension of polyvinyl chloride in the high-elastic state (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 317-322 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The dependence of true stress on the extension ratio of PVC threads has been determined for a wide range of extension rates. Since the polymer subjected to deformation was in the high-elastic state (at temperatures from 90 to 160°), the deformations were predominantly high-elastic. The dependence of true stress on the amount of high-elastic deformation is described by the Mooney-Rivlin equation.Relaxation moduli have been found on the basis of measurements of stress relaxation at constant deformation after various extension ratios were attained at different rates. Within the limits of deformation regimes at which the true stress is an increasing function of extension ratio the relaxation moduli do not depend on extension ratio and rate of extension. This enables one to arrive at a master curve of the relaxation modulus versus relaxation time with the reservation indicated above concerning the increasing character of the dependence of true stress on extension ratio. The relaxation spectrum represented by the high-elasticity plateau has been determined from the relaxation moduli according to the first approximation.The experimental data for a very wide range of deformation regimes and temperatures are presented in the form of an invariant dependence of the ratio of true stress to the rate of deformation on the product of deformation time by extension ratio.The ultimate strength of the specimens frozen rapidly after the attainment of definite extension ratios is determined by the accumulated high-elastic deformation.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120502
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  • 7
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    The elastic, anelastic and plastic components of strain in the load-extension curve for bisphenol-A polycarbonateThis Material was presented at the meeting of the American Physical Society, Atlantic City, N.J., March 27-30, 1972. (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 346-352 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A procedure has been developed for analyzing the elongation of a specimen in a tensile test for the elastic, anelastic, and plastic components of strain. The procedure was applied to bisphenol-A polycarbonate, which showed the division between the anelastic and plastic components to be justified and gave the following results. First, the elastic modulus was found to be essentially constant, independent of stress up to at least 7,000 psi. Second, the strain accumulated at the yield point was found to be mainly anelastic and recoverable with release of the stress. Third, plastic or non-recoverable strain was mainly accumulated only beyond the yield point. These latter two results suggest that anelasticity is important for ductility. The relatively large anelastic response at low stresses that contribute to the ductility of polycarbonate probably arises from both the large size of the moving segment and the large low temperature loss process.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120506
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  • 8
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    Evaluation of melt flow as a measure of low density polyethylene processability into blown films (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 459-463 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Melt capillary flow and extrudate swelling for low density polyethylenes (LDPE), differing in ease of heavy-duty, blownfilm extrusion, have been employed as processability criteria. LDPE of good processability is characterized by a unique combination of melt fluidity, temperature, shear rate dependence and melt elasticity. These characteristics of flow are correlated with LDPE film blowing process variables such as maximum take-up speed, film thickness scatter, and extruder temperatures profile. Intuitively, these melt flow criteria should be extended to Trouton's viscosity and the tensile strength of the melt. The limited development of the elongation viscometry techniques, however, has limited their application.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120613
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  • 9
    Electronic Resource
    Electronic Resource
    Melting rates of crystalline polymers under shear conditions (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 59-63 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The melting of solids under shear conditions is an important operation in the processing of most thermoplastics. In this study, solid blocks of high density polyethylene were melted on a hot, moving surface over a range of surface temperatures and velocities. The conservation equations for mass, momentum, and energy were applied to the molten layer and then simplified by an order of magnitude analysis. A general model that included all significant terms gave rates of melting that agreed closely with the measured rates. A simpler model that was analogous to present extruder models predicted melting rates that were ten to twenty-five percent lower than the experimental values. Models for polymers with low to moderate crystallinity should be modified to account for physical removal of amorphous material by shear forces.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120110
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  • 10
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    Rheological behavior of two-phase polymer melts (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 81-90 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Rheological behavior of dispersed two-phase polymer melts has been investigated by means of a capillary rheometer. The two-phase systems chosen for study were blends of two polymers: high-density polyethylene and polystyrene, which are incompatible in the molten state. In order to investigate the state of dispersion, photographs were taken of the microstructure of extrudate samples, showing that the polystyrene forms long fibers or droplets as a discrete phase dispersed in the polyethylene which forms a continuous phase. Measurements were made of the axial pressure distributions of the two-phase molten polymers flowing through circular tubes, which permit one, according to the theory advanced by Han, to determine viscous and elastic properties of the melts. Also measured was melt die swell ratio. It has been found from the two independent experimental techniques that there exist a maximum and/or minimum elastic property at a certain blending ratio, and that the elastic property decreases first with L/D ratio of a capillary and then levels off.
    Additional Material: 23 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120203
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  • 11
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    Determination of cure of diallyl phthalate using differential scanning calorimetry (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 120-124 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Kinetic parameters (reaction rate constant, activation energy, and frequency factor) were determined by differential scanning calorimetry using a linearly rising temperature program for the polymerization of diallyl phthalate monomer catalyzed with dicumyl peroxide. Cure times for specific degrees of cure at constant temperature were calculated and found to agree with the degree of cure measured by infrared spectroscopy. The relationship between non-isothermal and isothermal cure cycles is discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120208
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  • 12
    Electronic Resource
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    Masthead (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120101
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  • 13
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    Weathering of fibre reinforced plastics. Progress of dbonding detected in model systems by using fibres as light pipes (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 30-33 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The progress of interfacial debonding caused by the diffusion of boiling water to glass fibre/polyester resin interfaces has been followed by shining a He-Ne laser beam along fibres and recording the changes in intensity of the emergent beam. Compared with measurements of electical conductivity arising from the presence of diffused water at the interface, it is concluded that the laser beam method provides more certain evidence of debonding.The glass/resin interface has also been investigated in partially cured composites and in filled composites, during exposure to boiling water.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760120105
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  • 14
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    Weatheirng study of glass-fiber reinforced polyester sheets by scanning electron microscopy (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 53-58 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Evidence is presented of the main steps in the physical breakdown of glass-fiber reinforced polyester (GRP) composites on outdoor weathering. The chronological sequence is fiber ridging, rupture of the resin layer covering ridging fibers or fibers running close to the surface, spalling of the resin at the site of failure and subsequent erosion, fiber prominence and formation of a network of microcracks. Breakdown is believed to be caused by a type of stress fatigue imposed on the composite by cyclic variation of humidity and temperature in conjunction with solar radiation, and by the action of water and oxygen. The under side of the exposed GRP sheeting shows only incipient breakdown, indicating that solar radiation is an important factor. Countermeasures suggested to reduce breakdown include techniques to keep fibers away from the surface, use of resins with better thermal and moisture characteristics, and use of resin formulations with the best light stability.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120109
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  • 15
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    Converging flow of polymer melts in extrusion dies (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 64-73 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Practical extrusion processes often involve geometrically complex dies. Such dies are usually tapered, or streamlined, to achieve maximum output rate under conditions of laminar flow. These converging flows may be analysed in terms of their extensional and simple shear components to calculate the relationships between volume flow rate, pressure drop, and post extrusion swelling. The analysis can also be extended to cover the free convergence as fluid flows from a reservior into a die. Comparisons between predicted and observed data for a series of coni-cylindrical dies suggest that using this approach the pressure drop/flow rate relationship can be predicted within ±20% and the swell ratio/flow rate relationship within ±10%. Similar treatments have been in use for the last three years in solving such complex flow problems as radial flow in injection moulding and two-dimensional annular convergence in blow moulding dies.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120111
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  • 16
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    Ultraviolet depolymerization of photoresist polymers (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 109-111 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new method for removal of thin films of photoresist polymers has been found. When polymeric films are exposed to ultraviolet light in the presence of air, the material can be removed leaving an extremely clean surface, free of carbonaceous material. This process has been examined for a variety of photoresist polymers as well as on nonphotoresist polymers and on a variety of substrates. The process offers a new method of photoresist removal.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760120206
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  • 17
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    Thermal conductivity of polyethylene: The effects of crystal size, density and orientation on the thermal conductivity (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 204-208 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Thermal conductivity measurements were made on polyethylene samples which had been crystallized at different temperatures in order to vary density and lamellar crystal thickness. Tests were also made on polyethylenes which were oriented by mechanical shearing and by crystallization in a temperature gradient. The thermal conductivity increased linearly by 50% as the density went from 0.96 to 0.99 gm/cc. By orientation the conductivity was increased ten fold in the direction of molecular orientation and decreased two fold in the perpendicular direction. For samples oriented by deformation at different temperatures, the conductivity apparently correlates with birefringence.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760120308
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  • 18
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    Some factors influencing cooling rates of rotationally molded parts (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 335-339 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Recently, rotational molding engineers, concerned with warpage and uneven cooling in parts, have been “pre-cooling” the mold in forced draft air after removal from the oven and prior to water quenching to removal temperature. In this paper, we analyze some of the factors that influence the rate of heat removal from an amorphous plastic in a metal mold. We find that mold thickness and thermal diffusivity, convection heat transfer coefficient of the cooling fluid, the thermal properties of the plastic and the initial, final and “freezing” temperatures of the plastic influence this cooling rate and the corresponding rate of volumetric shrinkage. We illustrate our analysis with several examples and discuss some guidelines in detail.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760120504
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  • 19
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    Some aspects of orientation in injection molded objects (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 358-363 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The birefringences of injection molded plates and the birefringence during steady, isothermal shear flow were compared for some amorphous polymers. The materials studied were a polystyrene, a “toughened” polystyrene and an acrylonitrile-butadiene-styrene copolymer. The birefringence of the plates, notably the maximum value for the average over the thickness was found to be related to the shear stress at the cavity wall that had occurred during the mold filling process. This relationship was independent of temperature. To a good approximation, it was also the same as the relationship between the flow birefringence and the shear stress at the wall in isothermal channel flow. It thus appears that the anisotropy of injection molded objects is dominated by the shear stresses during the mold filling process regardless of the temperature and of the macroscopic rate of deformation.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760120508
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  • 20
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    Masthead (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120601
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  • 21
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    Energy transport to molten flowing polymer systems: II. Analysis of data and development of temperature profiles with axial length (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 402-408 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Energy transport to molten, flowing polymer has been studied. Experimental temperature profiles were determined at various axial lengths. These data are both precise and reproducible. Viscous dissipation was found to be a significant factor in these systems. In addition, sizable thermal expansion cooling effects were noted. It was also shown that the effect of viscous dissipation on Nusselt number was a function of Graetz number. At high Graetz numbers viscous dissipation had a sizable effect that declined to negligible proportions at Graetz values of 7 or less. Prior theoretical treatment of temperature profile development is shown to be only qualitatively correct.
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    Solids conveying in screw extruders part III: The delay zoneParts of this paper were presented at the 1971 ANTEC in Washington. (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 387-395 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A theoretical model was developed for the newly-defined delay zone of the plasticating screw extruder. The delay zone starts at the end of the solids conveying zone, i.e. at the point where the solid plug surface contacting the barrel melts and forms a film of melt up to where the steady state melting mechanism starts to operate. The model permits the film thickness and pressure profiles in this zone to be calculated. Published results were used to support the validity of the model. The results indicate that the film thickness at the end of the delay zone is several times the flight clearance. Finally, a criteria, based on the final value of the film thickness, is suggested to calculate the length of the delay zone.
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    The particle flow of polystyrene during capillary extrusion (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 416-419 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The melt flow of emulsion polymerized polystyrene has been investigated in accordance with the particle flow concepts developed by Berens and Folt. Particles were found to be present in the extrudate up to 210°C and resins with larger particles were found to have lower viscosities. The molecular weight appears to have no significant effect on the melt viscosity above a certain molecular weight. The energy of activation for viscous flow at 190°C and at shear stress of 5 × 105 dynes/cm2 was found to be 29-33 kcal/mol depending on type of resin.
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    Corrections (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 395-395 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120512
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    Energy transport to molten flowing polymer systems: I. Development of an apparatus to obtain temperature profiles (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 397-401 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An improved apparatus for studying temperature profiles in molten, flowing polymers has been developed. The apparatus incorporates modifications and improvements of earlier temperature profile devices. In addition, this unit made it possible to study temperature profile development as a function of axial flow length. Data taken with the apparatus were found not only to be precise and highly reproducible but also to show the proper trends with respect to physical behavior.
    Additional Material: 4 Ill.
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    Strain ratio and volume change during tension and compression creep of thermoplastics (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 420-424 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Creep tests up to 106 seconds in tension and compression were conducted on polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), and polypropylene (PP). Measurements of longitudinal and lateral strain provided values for tension and compression strain ratio. These increased with time and stress for PMMA and PVC from about 0.38 to 0.44. The results for PP increased from 0.44 to above 0.5 in. tension and showed a decreasing ratio in compression, which suggested a time and stress dependent structural change. Volumetric strain was computed from the linear strains and plotted against stress and axial strain. Except at 102 seconds, the relationships were non-linear up to volumetric strains of about 0.3% and in the cases of PMMA and PVC there were greater changes of volume in tension than compression.
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    URL: http://dx.doi.org/10.1002/pen.760120606
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    Tensile yield energy in glassy polymers (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 444-449 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An activation energy theory of yielding in glassy polymers has been proposed by Starita and Keaton. It predicts a linear relation between energy to yield and test temperature. This concept was tested and found valid for five amorphous polymers; poly(methyl methacrylate), polycarbonate, polyarylsulfone, polysulfone and poly(vinyl chloride), in uniaxial extension at temperatures from 25°C to the glass transition. For extenstion rates of 0.2 in/min, yield energy was found to go to zero at Tg, as commonly determined by thermodynamic methods like dilatometry or scanning calorimetry. The effect of other extension rates, plasticizer and molecular weight appears to affect only the intercept much as Tg is affected by the same changes. The slope, or the ratio of thermal to mechanical energy efficiency in overcoming the flow activation barrier, is largely unchanged.
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    Low temperature dynamic mechanical properties of polyurethane-polyether block copolymers (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 25-29 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dynamical mechanical relaxation spectra of a number of polyurethane-polyether block copolymers have been studied as a function of composition, temperature and frequency. At low temperatures these copolymers are characterized by a high glass-like modulus which decreases to a much lower typically elastomeric value in a narrow temperature range. The latter is a function in certain cases of the composition of the polymer. The rubbery plateau is maintained up to at least 140°C. In addition, a secondary relaxation is observed around -130°C. These observations can be interpreted in terms of an overall structure consisting of a polyether matrix containing segregated polyurethane domains, the latter serving as physical crosslinks in the system at ambient temperatures and above.
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    URL: http://dx.doi.org/10.1002/pen.760120104
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    Critcal stress and recoverable shear for polymer melt fracture (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 184-192 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The phenomenon of extrudate distortion, which is called melt fracture, was studied for polystyrene samples of narrow and broad molecular weight distribution, and commerical samples of polypropylene and linear and branched polyethylene. It was experimentally found that the shear stress at the onset of melt fracture (τcr) is of the order of 106 dynes/cm2 and independent of the distribution of molecular weights. As the weight average molecular weight increases the shear stress τcr decreases. For polystyrene extruded at τcr the recoverable shear strain, which is defined to be half the ration (first normal stress difference/shear stress), was found proportional to the factor MzMz+1/Mw2 which represents the distrubution of molecular weights. The proportionality is expected to hold for other polymer systems. The polymer behavior at the onset of melt fracture was explained in terms of Graessley's entanglement theory and his correlation between true and Rouse shear compliance.
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    Positive and negative photoresist applications of thin films surface-photopolymerized from hexachlorobutadiene (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 209-212 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polymeric films deposited from the vapor of C4Cl6 by the surface-photopolymerization technique are electrically and mechanically continuous on various substrates when very thin. The thickness of the films depends upon irradiation time with wavelengths in the region 2000-3000Å. Re-irradiation in oxygen (air) of the polymeric films with light of these low wavelengths leads to patterned removal of the films. Since films 500Å thick and less can resist etchants for various substrates, a new and extremely thin positive photoresist system is possible. Resolution of etched substrates to lines a few microns wide has been demonstrated. If the polymeric films from C4Cl6 are deposited from the monomeric vapor at lower substrate temperatures they are soluble in various solvents. Re-irradiation with UV light with the films in vacuum produces a patterned fixing of the polymer with respect to acetone. A negative photoresist system is therefore possible. Again, films of thickness 500Å and less can resist various etchants such that substrates can be etched to high resolution.
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    Structure-property relationships of chlorinated polyethylenes (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 224-235 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This experimental study of suspension-chlorinated linear polyethylenes (CPE), (degree of chlorination 25 to 48% Cl), covers dynamic mechancial behavior at 3.5 and 110 Hz in the temperature range - 100 to 120°C. The semicrystalline samples, with a maximum degree of crystallinity of 25%, showed the main relaxations α and β. The effect of thermal treatment was examined. In the amorphous specimens, in addition to the Tg relaxation, other low temperature damping peaks were observed. The mechancial spectra indicate structure heterogeneity and increasing stiffness with increasing chlorine substitution. For the most prominent β relaxation, the apparent activation energy was determined from the frequency shift of tan δ and E″ maxima. The effect of structure, crystallinity and frequency on Young's moduli are also discussed. For the amorphous γ ray-Crosslinked elastomeric samples the photoelastic properties were examined at near equilibrium conditions between 30° and 80°C at various degrees of crosslinking. The polarizability anisotropy of the optical link and the Mooney-Rivlin elasticity constants were determined and an attempt was made to relate the result to the specimens' structure. A compatibility study was also made for a 42% Cl, CPE/high cis polybutadiene polyblend. The damping mechanical spectra indicate a noninteracting system whose Young's moduli can be correlated with those of the pure components using a phenomenological model proposed by Takayanagi.
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    An analysis of fiber buckling (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 272-276 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper presents results obtained by the experimental technique of photoelastic stress analysis and by finite or discrete element analysis, applied to the case of buckling of a single, axially-loaded metal fiber embedded in a plastic matrix. The program was conducted utilizing a mild steel fiber embedded in an epoxy resin system. The fiber was loaded axially with an increasing compressive force until buckling occurred. Along with determination of the critical load for the fiber, the maximum shearing stress at any point in the epoxy matrix was determined using two-dimension photoelastic stress analysis. In the analytical study, the fiber was modeled by a series of bending elements and the matrix by an assemblage of constant-strain triangular elements. The total system was thus modeled by the two types of elements connected at common nodal points. The instability was solved as a standard eigenvalue problem and the stress tensor was obtained by finite element stress analysis.
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    URL: http://dx.doi.org/10.1002/pen.760120404
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    The injection molding of thermoplastics part II: Experimental test of the model (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 302-308 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Experimental studies have been conducted with a 2 1/3 oz reciprocating-screw injection molding machine to check the validity of a proposed theoretical model for injection molding. A semi-circular cavity has been employed in the study to achieve spreading radial flow during the filling stage. Both high speed photography and pressure transducer measurements have been employed to obtain data on polyethylene. The photographic studies confirm the existence of spreading radial flow throughout the filling stage, and are in very good agreement with data obtained with the transducer on the progression of the melt front in the cavity. The results show that the proposed theoretical model yields predictions which are in good agreement with experimental data for all stages of the injection molding cycle with polyethylene. The model also predicts a composite pressure-time curve for the overall cycle which is similar to those reported in the literature and which satisfactorily represents the data obtained in this study. It is also possible to predict a short shot under selected molding conditions in agreement with observation. The main problems in the application of the model arise during the filling stage near the cavity entrance where viscoelastic and end effects are important and where some of the assumptions inherent in the model may not be valid.
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    URL: http://dx.doi.org/10.1002/pen.760120409
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    Fusion of particulate structure in polyvinyl chloride during powder extrusion (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 199-203 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: It has been recognized recently that suspension polyvinyl chloride granules consist of particles ca 1μ in diam which are linked together to form a three-dimensional, sponge-like lattice. This paper deals with the fusion process of this particulate structure of PVC resin during powder extrusion. Extrudates prepared under various extrusion conditions are investigated through the electron microscope using a methyl methacrylate (MMA) embedding method followed by ultrathin sectioning. The MMA embedding method has been proven to be an effective means of revealing the detailed structure of molded PVC. Results showed that the 1μ-particles were subjected to breakdown due to heat and shear into fibrils 100-300 Å in thickness, which were the final structure attainable by extrusion. Discussion was focused on the fibrillar structure especially in relation to the elasticity in plasticized PVC.
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    Stability of fiber spinning of power-law fluids (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 219-223 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A stability analysis of fiber spinning of isothermal power-law fluids has been carried out. The analysis for purely viscous fluids indicates that the critical extension ratio increases with an increase in power-law constant q above 1. For q greater than approximately 1.5, very high values of critical extension ratio are obtained. A stability analysis in the presence of viscous and inertial forces indicates that for q 〉 1 critical extension ratio can be correlated to a quantity Rq = q - 1 + 3Re, wherein Re is the Reynolds number. For the values of Rq greather than approximately 0.5, very high values of critical extension ratios are obtained.
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    Dimensional recovery of cold-rolled polycarbonate (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 288-293 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The dimensional recovery of cold-rolled polycarbonate was measured between 100 and 147°C, and compared to stress-relaxation data. The strain-recovery isotherms were superimposed to produce a master curve which could be represented by a distribution function, U(τ), termed the strain recovery spectrum. U(τ) is found to be nearly identical to the relaxation spectrum, H(τ), calculated from the stress-relaxation master curve; and the shift in U(τ) as a function of temperature, WLF shift factor, is similar to that obtained from other viscoelastic measurements on polycarbonate. For the deformations studied, 25 and 50% reduction in thickness, the recovery behavior is found to be independent of strain (linear), suggesting that nonlinearity in a polymer glass results from large stresses, and not from large strains.
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    Masthead (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972) 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120501
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    Critical regimes of shear in linear polymers (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 323-334 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The state of the problem of elastic turbulence is critically discussed. It is shown that the development of elastic turbulence is associated with the transition of polymer systems to the high elastic state.Model experiments with a narrow-MWD polybutadiene have been carried out. The method of vizualization of the flow in a flat slit with the aid of circular-polarized light has been used. The results of polarization-optical investigation are compared with the results of capillary viscometry and dynamic measurements at small amplitudes. It is shown, in accordance with theoretical predictions, that when a polymer passes from the fluid to the high elastic state with an increase in the shear rate, it ceases to behave as a fluid under shear. This is accompanied by various forms of flow perturbation at the duct exit and entrance and inside the duct. Perturbations at the duct entrance and exit are due to stress concentration in these zones. The transition of a polymer to the high elastic state near the walls inside the duct gives rise to the “stick-slip” process or to continuous slippage along the duct walls, depending on the velocity of polymer movement. This can be clearly traced by the changes in the interference band pattern. Still higher velocities result in an intensive process of continuity break (rupture) in the polymer and in its chaotic movement in the duct as an aggregate of irregularly shaped lumps, which, relaxing, may form a continuous body again. Attention is drawn to the significance of these observations for a quantitative description of the viscosity anomaly of polymer systems and of the relationship between the viscosity anomaly with various flow irregularities and perturbations in such systems.
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    Prediction of polymer processing characteristics using the C. W. Brabender plasti-corder torque rheometer (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 353-357 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The Brabender Plasti-Corder is shown to be an effective tool for predicting the processing characteristics of thermoplastic polymers. Procedures for determining the molding temperature range, the relative melt viscosity over a continuous temperature range, and the stability of molding and experimental curtain coating materials are presented.Molding temperature ranges can be determined by first establishing the Brabender torque which corresponds to the maximum viscosity at which a material will just fill the cavity in a particular injection system under full injection pressure and maximum injection rate. This torque is constant for any material to be molded in this system. A Brabender torque-temperature curve is then obtained on the pertinent resin and the temperature which corresponds to the torque associated with the maximum viscosity is the minimum molding temperature. Maximum molding temperature is the temperature at which the log of the torque deviates from a linear dependence on temperature.The stability of thermoplastic compositions can be shown by a Brabender torque-time curve at constant temperature. An unstable polymer shows decreasing torque with time if the decomposition predominantly consists of chain scission.
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    The macroscopic volume changes of selected polymers subjected to uniform tensile deformation (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 432-436 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: High density polyethylene (PE), polycarbonate (PC), and polymethylmethacrylate (PMMA) were subjected to uniaxial tensile deformation up to the onset of instability or necking. Simultaneous readings of longitudinal extension and transverse contraction (width and thickness) were obtained continuously during the loading period. From these data, plots of longitudinal versus “average” transverse strain were produced and it was found that the trends were neither constant nor linear over the full strain range employed. Additional plots of per cent volume change versus longitudinal strain indicate that the PMMA and PC show a maximum volume increase of about 0.6% while PE shows a maximum volume decrease on the order of 2.5%. Similar volume decreases have been noted by others and it would appear that structural changes are the most likely cause of this behavior.
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    Kinetics of the thermal degradation of poly(1,4-cyclohexylenedimethylene terephthalate) (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 454-458 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The kinetics for the thermal degradation of poly (1,4-cyclohexylenedimethylene terephthalate) (PCHDT) were evaluated by means of a melt extruder. The effects of temperature, residence time, and oxygen content of the gas blanketing the polymer during storage on degradation of PCHDT were determined. The rate of thermal degradation was measured in terms of the rate of decrease of inherent viscosity and the rate of increase of carboxyl end group concentration.Residence time, temperature, and their interaction all contributed significantly to the degradation. For the conditions investigated, the oxygen content of the blanketing gas had no measurable effect on degradation. Analysis of the kinetic data yielded equations based on a random chain scission mechanism. These equations enabled the prediction of inherent viscosity and carboxyl end group concentration as functions of temperature and residence time and the inherent viscosity and carboxyl end group concentration of the original polymer. The activation energies for decrease in inherent viscosity and increase in carboxyl end group concentration of poly (1,4-cyclohexylenedimethylene terephthalate) were determined as 38.7 kcal/mole, respectively.
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    Solids conveying in screw extruders part I: A modified isothermal model (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 12-24 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An improved theoretical model was derived for the solids conveying zone of a plasticating extruder. The model makes possible calculations in variable channel depth section. It also allows for a bulk density which is a function of pressure and for the non-isotropic pressure distribution in the solid plug. An expression for maximum flow rate was also derived. Results simulated by the model on a computer indicate the effect of variables on extruder performance. The power consumption terms in the solids conveying zone of a plasticating extruder were also derived. Total power consumption is the sum of power consumptions on the barrel surface, screw surfaces and those due to pressure rise. Their relative importance was analyzed by computations. The effect of operating conditions and coefficients of friction on the various power terms was also analyzed.
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    Strength of short-fiber reinforced composites (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 48-52 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The structural utility of short, glass fiber-reinforced epoxy composities is experimentally investigated for fiber volume fractions from 0.15 to 0.5. The strength and stiffness of systems with randomly oriented fibers are compared with those of similar composites with aligned fibers. The ultimate strength of both types of material increses in a reasonably linear fashion with volume fraction up to 0.5. For all volume fractions in this range, strength of the random composites is slightly higher than the longitudinal and much higher than the transverse strength of equivalent compsites with aligned fibers. The modulus of the random system is approximately two-thirds the longitudinal and twice the transverse modulus of the unidirectional material. The structural utility of the flow molded material is greatest in uniaxial, stiffness critical situations. The greater strength and planar isotropy of the random composites make them preferable in all strength limited or multiaxial applications.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760120108
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    Masthead (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120201
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    Mechanical properties of particulate composites (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 91-100 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The mechanical properties of glass bead (30 micron diameter glass spheres) filled epoxy and polyester resins have been studied as a function of volume fraction of filler and the strength of the interfacial bond. The bonding between glass and resin was varied by chemically surface treating the glass using a silicone mold release to prevent chemical bonding at one extreme and a silane coupling agent to maximize bonding at the other extreme. Theoretical predictions of the elastic modulus and tensile strength have been made utilizing a finite element method. Excellent agreement is obtained with the experimental results. Izod impact energies have been measured for these composites as a function of filler content and interface treatment.
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    URL: http://dx.doi.org/10.1002/pen.760120204
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    Characterization of lubricants for polyvinyl chloride (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 112-119 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The proper use of lubricants and other additives in the compounding of PVC is hampered by lack of knowledge of their interactions with the polymer. Differential scanning calorimetry has been applied to measure the effect of ingredients on the glass transition temperature of PVC. An interaction parameter, based on changes in the glass transition temperature, has been proposed which quantitatively defines the degree of compatibility and which relates to the more empirical definition of lubricants as internal or external. This study of the compatibility of compounding ingredients as a function of molecular weight and chemical structure provides fundamental information of value in formulating, compounding and processing of PVC.
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    URL: http://dx.doi.org/10.1002/pen.760120207
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    Deep drawability of biaxially rolled thermoplastic sheets (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 150-156 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The deep drawability of biaxially cold-rolled thermoplastic sheets has been studied using polycarbonate, polyvinyl chloride, and acrylonitrile-butadiene-styrene polymers. Each polymer was rolled to two different reductions in thickness. The deep drawability of these rolled sheets was measured by determining the limiting draw ratio using a Swift cup test. Strain ratios were measured in three directions for each of the rolled sheets in order to determine the normal and planar anisotropy of the sheets. It has been determined that the drawability of a sheet can be correlated with the normal anisotropy of the sheet and it is the increase in normal anisotropy of a sheet which increases the drawability of the sheet. It has also been shown that lubrication increases the drawability due to a reduction in punch force.
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    URL: http://dx.doi.org/10.1002/pen.760120212
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    The potential for reuse of plastics recovered from solid wastes (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 157-166 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Plastics in solid wastes is a problem of growing concern. Recycling of wastes is currently believed to be the most acceptable form of disposal in the long run; however, this route is known to be especially difficult for plastics. Recycling would be easier if the various generic types present in solid wastes, mainly polyethylene, polystyrene and poly (vinyl chloride), could be isolated; however, this would be very difficult and expensive. This is a first report on research aimed at evaluating the potential of recycling plastics as a polymer blend of the various generic types. This approach suffers from the difficulty that the different plastics are incompatible and the blend has poor mechanical properties. The extent of this problem is documented with data on many ternary blends employing virgin polyethylene, polystyrene and poly (vinyl chloride) of numerous grades likely to be found in solid wastes. Property degradation was found to be more severe as the complexity of the blend increased, indicating that general municipal wastes could be reused only in very low grade applications, whereas certain commercial wastes might have brighter prospects. Strategies for improving blend properties are outlined.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760120302
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    Masthead (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120401
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    Thermal transport in the contact melting of solids (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 265-271 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Many industrial processes require that solids be transformed to the molten state, thus accurate correlations of heat transfer and melting rates are important in process design. The heat-balance integral type of analysis is applied here to melter systems where phase change and convection effects are of equal importance, and the appropriate parameters that govern the thermal transport process are presented. Applications of the results to both Newtonian and non-Newtonian, power-law melts are discussed, and extensions to variable property situations are outlined. Although the results herein are directly applicable to contact melting systems, the governing parameters are useful in the correlation of other melting processes as well. Acomparison is made between the theory and some experimental data for a gravity-feed contact melter. The results are directly applicable in practice to the melting of bulk and granular crystalline polymers on melting grids, tube bundles, and plates.
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    URL: http://dx.doi.org/10.1002/pen.760120403
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    Analysis of thermoplastic cup drawing (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 277-281 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The cup drawing process of thermoplastic sheet is analyzed on the basis of small deformation theory. The drawability of thermoplastic sheets is related to material parameters which may be investigated without performing an actual drawing process. Values for the drawability which are obtained by this method agree with values which are obtained by the Swift cup test.
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    The effectiveness of polymer additives as determined by torsional braid analysisPresented at the First Symposium on Torsional Braid Analysis, Society of Plastics Engineers Annual Technical Conference, Washington, D. C., May 10, 1971. (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 282-287 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Torsional braid analysis has been explored as a means of providing a quantitative measure for the effectiveness of polymer additives. Quantitative determinations have been made of antioxidant activity of selected compounds when formulated with certain elastomers prone to oxidative crosslinking on heat aging. The torsional braid technique has been used to determine the time dependence of the sharp torsional modulus increase which corresponds to a change from a rubbery to a highly crosslinked state. This time dependence is taken as a measure of the rate of oxidative crosslinking in heat-aged elastomer films coated on a Fiberglas braid. In this manner an assessment of antioxidant activity can be made. The effect of concentration and aging temperature on antioxidant activity can be made also. It has been also possible to use this technique to study the effect of structural changes in an antioxidant on its resultant activity. Feasibility studies have also been made on antiozonants in natural rubber and cis-polybutadience at three temperatures. A value of 10.9 Kcal/mole was calculated for the activation energy for the oxidative crosslinking reaction of cis-polybutadiene.
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    URL: http://dx.doi.org/10.1002/pen.760120406
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    Predicting melt flow instability from a criterion based on the behavior of polymer solutions (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 309-314 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A criterion, based on the behavior of polymer solutions, is developed and applied for the prediction of the onset of flow anomalies observed at the capillary entrance for polymer melts. It is shown that a direct correspondence exists between the flow anomalies observed for polymer solutions and polymer melts. The onset of these anomalies can be correlated with a critical Weissenberg number which is consistent with the equality of the shear wave velocity and friction velocity. This critical condition can be employed to derive expressions useful for predicting the critical recoverable shear and critical shear stress for melt fracture.
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    URL: http://dx.doi.org/10.1002/pen.760120410
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    The effect of molecular weight distribution on polyethylene film properties (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 340-345 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polymer molecular weight heterogeneity affects the rheological properties of polymer melts such as melt viscosity, fracture and die swell. These rheological properties affect the conversion of the polymer from the bulk resin state to its final usable form. In this particular study, the effect of molecular weight distribution on polyethylene blown film characteristics was studied. The effect of the molecular weight heterogeneity on the rheological characteristics of the polymer in the molten state and its effect on the film properties is presented.The properties studied included film gloss, haze, tear resistance and film impact strength.This study shows that broadening the molecular weight distribution increases haze and reduces film gloss. Further, it was shown that a linear relationship exists between film gloss and external haze. Both values are measures of surface irregularities in the film which are affected by the drawing characteristics of the polymer.A broader molecular weight distribution results in increased impact strength as measured by the Dart Drop Impact Test. This is, it is believed, a result of the increase in long chain branching of the higher molecular weight fractions of the polymer which cause a higher degree of molecular weight entanglement at the branch sites. In contrast the tear strength is reduced as the molecular weight distribution broadens because of the low molecular weight fraction in the broad spectrum material which tend to decrease resistance to tear.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760120505
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    Microfibers within fibers: A review (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 364-377 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Literature relating to the fundamental nature of the fibrous state is reviewed with the goal of illustrating evidence for the existence of a possibly fundamental morphological unit, the elemental microfiber or fibril. Following a short summary of the rather well documented situation in natural fibers, the problem of the microfiber in synthetic fibers is probed in terms of phenomena in solution and bulk polymeric systems. The reviewed literature indicates the existence of unique, elemental microfibers in synthetic fibers is largely tenuous; however, there is wide evidence of the existence of complex elongated structures axially aligned within macrofibers which future work may resolve into a central microfiber. The structural complexity appears to simplify for transformations occurring in high shear fields. This review covers articles through 1971, and it is notable that in 1971 approximately 100 articles of high relevance appeared in major journals.
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    Solids conveying in screw extruders part II: Non isothermal modelParts of this paper were presented at the 1971 ANTEC in Washington. (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 378-386 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Isothermal solids conveying theories have been developed in the past. However, due to friction, the surface temperature of the solid plug does increase. This change in temperature will strongly affect the temperature sensitive coefficients of friction and consequently also the pressure that develops. The surface temperature of the solid plug is also an important variable on its own because, when it reaches the melting point, the solids conveying zone is terminated. A mathematical model has been developed to calculate the temperature profile in the solid plug together with the strongly interacting pressure profile. Calculations indicate that high pressure in the solids conveying zone can practically be obtained only by very efficient cooling of the barrel in this zone.
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    The bending of polymers under tension as related to a deep drawing process (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 409-415 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Two engineering plastics, an acrylonitrile-butadiene-styrene resin (ABS resin, Cycolac MS) and a rigid polyvinyl chloride resin (PVC resin, Dacovin 2082) were investigated to determine the effects of cold working. In particular, the “bending under tension” stress system of a deep drawing process was considered. The object was to determine the effect of the blank-holder pressure, the ratio of the punch radius to the material thickness, the speed of deformation and the temperature of deformation. The stress-strain characteristics of the deformed and undeformed material were markedly different. Upper yield points were lower in the deformed specimens, the tensile strengths were decreased by 10 to 15% and the %-elongation at break was higher - up to double the values for underformed specimens. An analysis indicated that these effects can be attributed to non-homogeneous yielding. The results also indicated that crazing plays an important role in permitting an ABS material to permanently conform to a radius with no geometric constraints.
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    Characterization of polyvinyl chloride. Part III. An alternative GPC method for measuring the radii of gyration, and the degree of long-chain branching of polydispersed polymers (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 437-443 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A method for measuring the unperturbed radius of gyration and the degree of long-chain branching in Gaussian-distribution polymers is proposed. Polyvinyl chloride (PVC) and polyvinyl acetate (PVAc) were selected to illustrate the method. It was observed that PVC samples prepared by homogeneous and heterogeneous polymerizations exhibit the same degree of long-chain branching. This conclusion is supported by viscometric data. The polydispersity ratios (Mw/Mn) indicate that both types of polymerizations would yield a very small amount of total branching (long chain and short chain.) The calculated unperturbed radius of gyration of linear PVC samples was found to be 0.185 \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {\frac{{{\rm \dot A}^{\rm 2} {\rm mole}}}{{{\rm gm}}}} \right) $\end{document}, and that of PVAc was determined to be 0.107 \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {\frac{{{\rm \dot A}^{\rm 2} {\rm mole}}}{{{\rm gm}}}} \right) $\end{document}. The value obtained for PVC is shown to be in agreement with the value determined from the viscometric method as described in our previous work.
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    The ultrastructure of developing wings in the giant silkmoth, Hyalophora cecropia. I. Generalized epidermal cells (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 136 (1972), S. 1-21 
    Details
    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 wing epidermis of the giant silkmoth, Hyalophora cecropia, was studied during pupal diapause and the first half of development to the adult. In diapause, the generalized epidermal cells are characterized by many free ribosomes, some vesicles and small lamellae of rough endoplasmic reticulum, some scattered short mitochondria and a few small Golgi complexes. During the early states of post-diapause development, before and after the time of apolysis (separation of the epidermis from the overlying cuticle), there is a marked increase in structures often associated with synthetic functions, such as polyribosomes, lamellate rough endoplasmic reticulum and Golgi complexes. On day five of post-apolysis development, just after the appearance of scale-forming and socket-forming cells, the generalized epidermal cells lay down the cuticulin layer of the adult cuticle. At this stage and later, the polyribosomes and lamellate rough endoplasmic reticulum decrease in abundance. Cell nuclei show three phases of temporary transition from predominantly lobed to predominantly round profile, which correspond to periods of reported DNA synthesis. Throughout this developmental process, therefore, there is good correlation of fine structure with changes in macromolecular synthesis recorded elsewhere.
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    URL: http://dx.doi.org/10.1002/jmor.1051360102
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    Aspects of the circulatory system of Pollicipes polymerus J. B. Sowerby (Cirripedia: Thoracica) (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 136 (1972), S. 79-107 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The circulatory system of Pollicipes polymerus exhibits a high degree of organization which precludes it from being referred to as an open system. The system is arbitrarily divided into four parts: (1) the circulation of the peduncle and mantle; (2) the distributive circulation of the body, which provides hemolymph to most of the cephalic gut, to the maxillary gland, and to the cirri; (3) the peripheral circulation which distributes blood from the cirri to the peripheral areas of the thoracic region, to most of the thoracic gut, and from the scutal sinus to the peripheral areas of the cephalic region; and (4) the collecting circulation, which conveys hemolymph mostly from the peripheral circulation of the body to the peduncle. There also may be a circulation that is comparable to the vertebrate lymphatic system.Pumping of hemolymph can be attributed to three pairs of skeletal muscles that compress the dorsolateral channels. These muscles are unique for crustacean muscles in that they do not appear to be striated.The rostral vessel appears to be a vestige of a heart in which the pump muscles have been lost. There is a similarity of the rostral vessel to the heart of Calanus finmarchicus (a copepod). This is additional evidence linking the cirripeds with the copepods within the Maxillopoda.Electron microscope observations of the walls of the midsagittal vessels indicate that there is a more or less random layering of cellular and noncellular elements within the wall. Muscle cells appear to be incorporated in the vessel wall.
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    Oogenesis in Xenopus laevis (Daudin). I. Stages of oocyte development in laboratory maintained animalsResearch sponsored by the U. S. Atomic Energy Commission under contract with Union Carbide Corporation. (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 136 (1972), S. 153-179 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Oogenesis in the anuran Xenopus laevis can be divided into six stages based on the anatomy of the developing oocyte. Stage I consists of small (50 to 100 μ) colorless oocytes whose cytoplasm is transparent. Their large nuclei and mitochondrial masses are clearly visible in the intact oocyte. Stage II oocytes range up to 450 μ in diameter, and appear white and opaque. Stage I and II are both previtellogenic. Pigment synthesis and yolk accumulation (vitellogenesis) begins during Stage III. Vitellogenesis continues through Stage IV (600 to 1000 μ), the oocytes grow rapidly, and the animal and vegetal hemispheres become differentiated. By Stage V (1000 to 1200 μ) the oocytes have nearly reached their maximum size and yolk accumulation gradually ceases. Stage VI oocytes are characterized by the appearance of an essentially unpigmented equatorial band. They range in size from 1200 to 1300 μ, are postivtellogenic and ready for ovulation. These stages of oocyte development have been correlated with physiological and biochemical data related to oogenesis in Xenopus.
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    Ultrastructural contributions to the identification of cell types in the lizard epidermal generation (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 136 (1972), S. 191-209 
    Details
    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 epidermis at different stages of the shedding cycle has been studied in Anolis carolinensis. Cells of the germinal layer are morphologically similar at all stages in the cycle. Immediately after leaving the germinal layer all daughter cells resemble one another closely. However, they later acquire specific ultrastructural features that enable them to be classified into six distinct fully differentiated types corresponding to the grouping previously set forth by light microscopy. A comparison of cytoplasmic filament size with the known X-ray diffraction data suggests that the Oberhautchen and β-layer contain a protein similar to that of avian feather; the protein in the α-layer and lacunar tissue is similar to that in mammalian hair, and the mesos layer cells probably contain a mixture of feather and hair-like proteins. The nature of the amorphous cytoplasmic material in the mature clear layer is as yet unknown.
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    Comparative observations on the morphology of the mammalian periovarial sac (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 136 (1972), S. 247-254 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The interspecific variation in the positional and mesenteric relationship of the mammalian oviduct to the ovary observed among 41 species is summarized by distinguishing eight morphological types of relationship. The recognition of types is based on wide species differences in: the position of the oviduct with reference to the mesosalpinxal fold and ovary; the extent to which oviducal mesenteries enclose the ovary in a periovarial sac; the degree of closure and method of formation of the peritoneal opening to the periovarial sac; and the morphology of the oviduct.
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    Masthead (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 136 (1972) 
    Details
    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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    URL: http://dx.doi.org/10.1002/jmor.1051360301
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    Fine structure of the stellate cell in the pars distalis of the lizard, Anolis carolinensis (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 136 (1972), S. 227-245 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The stellate cell in the pars distalis of Anolis carolinensis has been studied with the electron microscope. This cell type is characterized by the lack of secretory granules, and it possesses elongate processes that insert between secretory cells. Few cytoplasmic filaments are present in these processes, and desmosomes linking them to adjacent stellate cells or to secretory cells are seen infrequently in control animals. Stellate cells are often encountered in the caudal half of the pars distalis, but they are less commonly found in the rostral half. In animals undergoing thyroidal depression, thyroidectomy cells arise in the caudal pars distalis. Concurrently, stellate cells of that region hypertrophy and exhibit increased numbers of desmosomes, complex intercellular junctions, and micropinocytotic vesicles. Injected horseradish peroxidase penetrates the intercellular spaces, enters the micropinocytotic vesicles, and is transported to the interior of the stellate cell. It is suggested that stellate cells in Anolis under certain conditions may transport materials between the bloodstream and secretory cells.
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    A cytological study of the ovary of Rhodnius prolixus. I. The ontogeny of the follicular epithelium (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 136 (1972), S. 459-493 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The relatively undifferentiated cells comprising the prefollicular epithelium of the fourth and fifth instar of the reduvid bug Rhodninus prolixus are flattened and contain the regularly occurring organelles, lipid droplets, and aggregates of glycogen-like particles. These cells transform into the adult prefollicular tissue.During vitellogenesis there is a gradual shortening of the cells of the follicular epithelium and an increase in the size of the intercellular space between them and between follicle cells and oocyte. The follicle cells are binucleate, contain numerous microtubules, rough endoplasmic reticulum, many free and aggregate ribosomes, and Golgi complexes. They are associated with each other by gap junctions. Only the follicle cells on the lateral aspects of the oocyte exhibit the development of large extracellular spaces while those at the apical end, that produces the cap, remain tall and closely apposed to each other during vitellogenesis. The normal morphology of the follicle cells over various areas of the oocyte suggests that shape and/or volume changes of these cell may be important in regulating the access of yolk proteins to the colemma.Subsequent to vitellogenesis the follicle cells become cuboidal and once again become closely apposed to each other. They contain much rough endoplasmic reticulum and produce the secondary coat.
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    A comparison between the dermal glands in two insects Rhodnius prolixus (Hemiptera) and Calpodes ethlius (Lepidoptera) (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 136 (1972), S. 495-503 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The results of histochemical tests performed on the type “B” dermal gland in Rhodnius and the Verson's gland in Calpodes at different stages in their secretory cycle are presented. The secretions of both glands are slightly acidic sulphated mucosubstances. They differ in their main carbohydrate component which in Rhodnius is hyaluronic acid and in Calpodes is sialic acid. The glands, though structurally similar, differ in size, number, and development.
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    Histological and histochemical studies of post-ovulatory and pre-ovulatory atretic follicles in Mustelus canisPartial support by a Grant-in-Aid of Research from The Society of The Sigma Xi. (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 136 (1972), S. 433-457 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The atresia of post-ovulatory and pre-ovulatory follicles of the viviparous smooth dogfish, Mustelus canis, is compared for approximately the first fourth of an 11 month gestation. A thick collagenous sheath and numerous tubules in the theca identify the large, folded stage A post-ovulatory follicle. In stage B the tubules have been filled by cells to form “islands.” In stage C the entire structure is greatly diminished, adjacent islands tend to fuse, the collagenous sheath is virtually gone and the granulosa is degenerating. Preovulatory follicles from large, yolky oocytes pass through four stages beginning with yolk phagocytosis by granulosa cells of the villi (stage I), which are long and granular in stage II; villi fuse, theca cells increase greatly, fill with granules (stage III), encroach on the granulosa and disperse it into small groups of cells which finally disappear (stage IV) leaving a mass of thecal cells. A special type of pre-ovulatory follicle from small non-yolky oocyte atresia exhibits prominent thecal tubules and an unusual arrangement of granulosa cells. This follicle appearrs to enlarge during the summer, becoming multilobed; few granules are present.The distribution of lipid in frozen sections, stained by Oil red O, is described for all types of follicles. Schultz and Lewis and Lobban tests for steroids were made on frozen sections with corresponding results. Positive green tests indicating the presence of steroids or possible steroidogenesis were limited to: (1) one post-ovulatory follicle, in the islands; (2) four stage III and seven late stage IV pre-ovulatory yolky atretic follicles; (3) two special atretic follicles. The special atretic follicle appears to be a unique feature of M. canis and it is suggested tentatively that it may be related to viviparity.
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    Masthead (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972) 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051370101
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    Muscular control of the vocal tract during release signaling in the toad Bufo valliceps (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972), S. 1-27 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The release vibration and release call of Bufo valliceps have been studied by electromyography of the muscles involved, coupled with pressure and sound recording. The sequences are powered by contraction of the muscles of the body envelope and with the energy transmitted via the compressed pulmonary contents. Each pulse of a call starts as the laryngeal muscles relax and pulmonary pressure forces the arytenoid cartilages apart. Sound emission ceases when the laryngeal dilators pull the arytenoids out of the airstream. Reverse flow of air from buccal cavity to lungs may occur within prolonged release sequences. Inflation of the vocal sac results in marked increase in amplitude of the radiated sound without equivalent increase in amplitude of the myograns. The call is intimately associated with the pulsepumping method of breathing used by frogs.
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    Ultrastructural observations on oogenesis in Drosophila (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972), S. 29-48 
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    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 follicle cells and oocyte periplasm is described during the stages of oogenesis immediately prior to, during, and immediately subsequent to, vitellogenesis. A number of features have not been described previously in Drosophila. Some yolk appears prior to pinocytosis of blood proteins. However, most of the protein yolk forms while the periplasm is filled with micropinocytotic invaginations and tubules derived from the oolemma. These tubules retain the internal layer of material characteristic of coated vesicles and are found to fuse with yolk spheres. No accumulation of electron-dense material in the endoplasmic reticulum or Golgi of the oocyte is found. Both trypan blue and ferritin are accumulated by the oocyte.The follicle cells have an elaborate endoplasmic reticulum during the period of maximum yolk accumulation. Adjacent cells are joined at their base by a zonula adhaerens, forming a band around the cells, and by plaques of gap junctions. Gap junctions are also present between nurse cells and follicle cells. During chorion formation, septate junctions also appear between follicle cells, adjacent to the zonula adhaerens.
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    The facial musculature of the suoidea (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972), S. 49-62 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The facial musculature and rhinarial anatomy of a tayassuid, Dicotyles, and four suids, Sus, Hylochoerus, Phacochoerus and Babirussa, are described. Differences found include the lack of m. zygomaticus in Hylochoerus and Phacochoerus and several modifications of the rostral muscles, mm. levator rostri, dilator naris, and depressor rostri. These differences are related to behavioral characteristics of the animals, particularly the occurrence of toothbaring and rhinarial mobility.The missing m. zygomaticus and relatively small mouth of Hylochoerus and Phacochoerus are probably associated with behavioral patterns which do not necessitate a large gape. In these genera the canines are exposed even when the mouth is closed. The development of the rostral musculature is correlated with movements of the rhinarium. Similarly, the distribution of terminal tendons depends on the shape of the nostril. In Hylochoerus and Phacochoerus, mobility of the rhinarium, especially the dorsal part, is less than in other suoids because of the firmer attachment of the rostral bone to the skull and the weaker development of the rostral muscles.
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    Formed elements of the blood of the fresh water mussel, Lamellidens corrianus (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972), S. 63-69 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The formed elements of the blood of L. corrianus are comprised exclusively of amoebocytes, whose total number is approximately 758 per cubic mm of blood. The blood cells are of three types, viz. acidophils, large basophils and small basophils, which are respectively 26.32%, 60.20% and 13.48% of the total blood cell population. The cytoplasm of the acidophils is filled with large acidophilic granules, while that of the basophils contains fine basophilic granules. Acidophils are the largest (7.6 μ × 6.7 μ), large basophils are smaller (6.5 μ × 4.9 μ), and small basophils are the smallest (4.1 μ × 3.8 μ). The nucleus occupies a very small volume of the cell (approx. 1/9th) in acidophils, a larger volume (approx. 1/4th) in large basophils, and a major volume (approx. 3/4th) in small basophils. The blood cells show amoeboid movement, which is brought about by means of broad lamellate pseudopodia. Large basophils move very slowly, acidophils move faster, and small basophils move quite fast. Fine bristle-like filipodia help the blood cells in getting entangled to form clumps. Filipodia are more abundant in large basophils and acidophils which pertake more actively in clumping than small basophils which rarely possess filipodia. Clumping is a reversible process which is promoted by mechanical agitation of blood.
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    Masthead (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972) 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051370201
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    Secretion by ependymal cells of the neurohypophysis and saccus vasculosus of Polypterus ornatipinnis (osteichthyes) (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972), S. 111-130 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Electron microscopic studies of the neurohypophysis and saccus vasculosus of the bichir (Polypterus ornatipinnis) reveal an apocrine release of secretory material by ependymal cells (e.g., crown cells). The secretory material appears to migrate along the microtubular apparatus and the ciliary filaments to the cell buds. It is postulated that the formation of the buds and their release is mediated by cilial action. Secretion buds are noted in the cerebrospinal fluid and vascular sinusoids.Bulbous projections of neurohypophyseal secretory tracts extend into the ependymal lumen which also contains elementary secretion granules. Specialized “liquorkontaktneurone” are interspersed with ependymal cells.An interrelation between the hypothalamus, neurohypophysis, saccus vasculosus, and the meta-adenohypophysis is postulated.
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    The mucigenous glandular mucosa in the complex stomach of two new-world camelids, the llama and guanacoThis investigation was supported by General Research Support grant 5-501-RR-05462 from the General Research Support Branch, Division of Research Facilities and Resources, National Institutes of Health and the Rockefeller Foundation. (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972), S. 71-109 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In contrast to the so-called true ruminants, the compartmentalized stomach of these camelids contained an extensive mucigenous glandular mucosa. This mucosal epithelium was studied with the light and electron microscope. Surface, foveolar, isthmic, and end-piece regions were identified. Undifferentiated cells with many free ribosomes and few mucigen granules were found in the gland isthmus. More fully differentiated mucigenous cells with fewer free ribosomes, an extensive Golgi complex and a large heterogeneous population of secretory granules were observed in the subjacent end-piece. These cells were compared with cardiac and other gastric glandular epithelia. The cells in the foveola contained a more extensive granular reticulum, a prominent Golgi complex, and large numbers of mucigen granules and mitochondria. In the upper foveolar cells, large supranuclear and narrow apical accumulations of mucigen granules were separated by an intervening mitochondrial mass. In the tall surface cells there was a diminution in the number of mucigen granules and a concomitant supranuclear massing of mitochondria. Basally, these cells were often separated by prominent intercellular spaces. Effete surface cells were also noted. These lacked desmosomal attachments and sometimes appeared partially extruded. These findings suggested that cells derived from the undifferentiated isthmic cells moved up the foveola and onto the luminal surface. During this migration, these cells appeared to undergo sequential cytologic differentiation. The possible functional significance of these differentiations was considered.
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    The mechanism of ultraplanktonic entrapment in anuran larvae (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972), S. 279-287 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Tadpoles of several different genera were fed graded suspensions of uniform polystyrene particles to determine the lower size limit of particles that could be ingested. Certain tadpoles can extract suspended particles as small as 0.126 μ in diameter from the water. In terms of particle size, this is an efficiency comparable to the best mechanical sieves that can currently be produced by man. A mechanism for ultrasplanktonic entrapment is proposed on the basis of scanning electron micrographs of the secretory ridges in the branchial food traps of Rana catesbeiana before and after feeding.Xenopus tadpoles in yeast suspensions modify their clearance and buccal pumping rates in response to varying food concentrations. This may be an adaptation for maintaining a constant input of food mass to the tissues that extract the food from the water.Variability in the lower size limit of filterable particles among tadpoles of different genera correlates with the availability of suspended matter in the microhabitat where these tadpoles may be found.
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    Fine structure of the triturating devices in the food pump of Notonecta (Heteroptera: Notonectidae) (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 138 (1972), S. 141-167 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The cibarial food pump of heteropteran insects conveys fluid food from the piercing stylets to the pharynx. In aquatic Heteroptera the pump also grinds and filters particulate matter in the food stream. The pump's sclerotized triturating devices differ from one family to the next and are often quite elaborate: because of their small size they are best studied by means of the scanning electron microscope. In Notonecta the main triturating devices occur on the transverse plates of the epipharyngeal roof of the pump. They consist of a complex anterior zone with raised nodes and bifurcating longitudinal ridges, and a simpler posterior zone with small nodules. Additional triturating surfaces occur on the hypopharyngeal floor of the pump. The oblique folds of the epipharynx, which lie anterior to the transverse plates, play only an accessory role. The fine structure of the grinding surfaces on the transverse plates of Gelastocoris (Gelastocoridae), Ambrysus (Naucoridae), and Aphelocheirus (Aphelocheiridae) is here briefly described and compared with that of Notonecta.
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    Development of electric organs of Gymnarchus niloticus (Fam. Gymnarchidae): I. Origin and histogenesis of electroplates (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 138 (1972), S. 375-385 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The development of the electric organs of Gymnarchus niloticus has been studied and the origin and histogenesis of an electroplate worked out. A segmental origin of the electroplate is reported for the first time for this fish. Light has been thrown on many hitherto obscure phenomena, viz., growth of core girth, loss of transverse striations on the myofibrillar elements, differentiation of electroplate polarities, shortening in length of the electroplate etc. The transverse striations of the myofibrillar bundle of the electroplate primordium progressively disappear with development owing to splitting apart of the constituent myofilaments and consequent loss of their parallel order, and not to degeneration of the myofibrillar bundle. The excessive growth of the core girth of the electroplates is caused by the deposition of some kind of interfibrillar substance probably secreted by the peripheral cytoplasm.
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    Fine structure and differentiation of ascidian muscle. I. Differentiated caudal musculature of Distaplia occidentalis tadpolesThis investigation was supported by NIH Developmental Biology Training grant 5-T01-HD00266 to the University of Washington and NSF Research grant GB 5394. (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 138 (1972), S. 349-373 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The structure of the caudal muscle in the tadpole larva of the compound ascidian Distaplia occidentalis has been investigated with light and electron microscopy. The two muscle bands are composed of about 1500 flattened cells arranged in longitudinal rows between the epidermis and the notochord. The muscle cells are mononucleate and contain numerous mitochondria, a small Golgi apparatus, lysosomes, proteid-yolk inclusions, and large amounts of glycogen. The myofibrils and sarcoplasmic reticulum are confined to the peripheral sarcoplasm.Myofibrils are discrete along most of their length but branch near the tapered ends of the muscle cell, producing a Felderstruktur. The myofibrils originate and terminate at specialized intercellular junctional complexes. These myomuscular junctions are normal to the primary axes of the myofibrils and resemble the intercalated disks of vertebrate cardiac muscle. The myofibrils insert at the myomuscular junction near the level of a Z-line. Thin filaments (presumably actin) extend from the terminal Z-line and make contact with the sarcolemma. These thin filaments frequently appear to be continuous with filaments in the extracellular junctional space, but other evidence suggests that the extracellular filaments are not myofilaments.A T-system is absent, but numerous peripheral couplings between the sarcolemma and cisternae of the sarcoplasmic reticulum (SR) are present on all cell surfaces. Cisternae coupled to the sarcolemma are continuous with transverse components of SR which encircle the myofibrils at each I-band and H-band. The transverse component over the I-band consists of anastomosing tubules applied as a single layer to the surface of the myofibril. The transverse component over the H-band is also composed of anastomosing tubules, but the myofibrils are invested by a double or triple layer. Two or three tubules of sarcoplasmic reticulum interconnect consecutive transverse components.Each muscle band is surrounded by a thin external lamina. The external lamina does not parallel the irregular cell contours nor does it penetrate the extracellular space between cells. In contracted muscle, the sarcolemmata at the epidermal and notochordal boundaries indent to the level of each Z-line, and peripheral couplings are located at the base of the indentations. The external lamina and basal lamina of the epidermis are displaced toward the indentations.The location, function, and neuromuscular junctions of larval ascidian caudal muscle are similar to vertebrate somatic striated muscle. Other attributes, including the mononucleate condition, transverse myomuscular junctions, prolific gap junctions, active Golgi apparatus, and incomplete nervous innervation are characteristic of vertebrate cardiac muscle cells.
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    Masthead (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 138 (1972) 
    Details
    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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    URL: http://dx.doi.org/10.1002/jmor.1051380401
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    Masthead (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 136 (1972) 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051360101
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    Ultrastructural changes in the pars distalis of the maturing male rat (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 136 (1972), S. 53-77 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Anterior pituitary glands of male rats (2, 3, 5, 8, 12, 25, 36, 52, 56, and 62 days of age) were processed for electron microscopy. During early postnatal stages secretory cells are found in various stages of differentiation and comparatively few secretory granules are seen. Nuclei are mostly irregular, and the nucleo-cytoplasmic ratio is large. Many free ribosomes are present; the endoplasmic reticulum is generally sparse and the Golgi complex small or invisible. Cells are of variable shape, and numerous cytoplasmic processes project into large intercellular spaces. Many electron-dense cells which often contain myelinlike figures are seen. Lysosomes and lysosomal precursors are frequently found in secretory cells, predominantly in somatotrophs, of all immature glands. Mitotic figures are numerous in early stages after brith and decrease in number as the gland grows in size. A gradual increase in cytoplasmic volume with concomitant differentiation of cytoplasmic components as well as accumulation of secretory granules, accompanied by loss of myelin-like figures and decrease in the number of electron-dense cells, is observed as the animal reaches the prepuberal stage. Few lysosomes are seen in cells of mature glands. At 36 days of age all secretory cells seem to have differentiated, and morphological features as well as granule content show little change until puberty is reached. Gonadotrophs attain their characteristic morphology later than other cells. Cilia are observed in all developmental stages but are relatively infrequent in the mature gland. The described ultrastructural characteristics reflect the degree of maturation as well as the functional capacities of secretory cells at particular stages of development.
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    The fine structure of an absorptive epithelium in a viviparous teleostWork performed under the auspices of the U.S. Atomic Energy Commission, and with support from the National Science Foundation, grant GB2378. (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 136 (1972), S. 109-129 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Embryos of the viviparous teleost, “Characodon” eiseni, have unusual anal processes that function only during gestation and are lost shortly after birth. This study was undertaken to determine if the fine structure of the process epithelium supports the assumption that these cells have an absorptive function. The process epithelium is a single layer of columnar cells. At peak activity intercellular spaces become very large and isolate individual cells which simultaneously lose much of their cell mass. The cells are characterized by microvilli on their free surface, much pinocytic activity and by the formation of at least four different kinds of vesicles. There is much evidence that these vesicles fuse together. A distinctive characteristic of these cells is a system of tubules and flattened cisternae that somewhat resemble the endoplasmic reticulum yet they differ from it in several respects. It is suggested these profiles aid in fragmenting the cell at periods of peak absorptive activity, thereby increasing the cell surface. Possible mechanisms of food absorption are considered. The fine structure of these cells supports the contention that these embryonic processes serve as absorptive organs during gestation.
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    The spermatozoon of Branchiostoma lanceolatum L (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 136 (1972), S. 211-226 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Under the electron microscope, the spermatozoon of Branchiostoma lanceolatum shows a spherical nucleus deeply grooved along its caudal third, a bistratified acrosome enriched by plentiful subacrosomal material, two centrioles, mitochondria fused into a single mass surrounding the centriolar region which is highly asymmetrical, a 9 + 2 flagellum tilted with respect to the longitudinal symmetry axis of the nucleus. The sperm of Branchiostoma shares the overall features of that of the Tunicata and fits in perfectly with the phylogenetic position of the Leptocardia.
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    The structure and prenatal morphogenesis of the nasal septum in the rat (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972), S. 131-147 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: One hundred fetuses of the Sprague-Dawley rat were used: ten for each prenatal day, beginning with the twelfth day of gestation. Pregnant animals were sacrificed, fetuses removed and subsequently fixed in buffered formalin solution. Fetal heads were dehydrated, embedded in paraffin, and sectioned serially in the rostrocaudal direction at 10 to 15 μ. Serial sections from fetuses representing each day of gestation were stained with either H and E, Mallory's trichrome procedure, Gomori's reaction for alkaline phosphatase, or Steedman's alcian blue reaction. At the twelfth day, the primary nasal cavities were first observed. One day later, the nasobuccal membrane was established, and the vomeronasal organ invaginated into the nasal septum. Following the rupture of the membrane, at the fourteenth day, the nasal and buccal cavities remained in communication until the palatal shelves fused with the septum, at the seventeenth day. Prior to the thirteenth day, the septal skeleton is mesenchymal. The ossification in the vomer started at the sixteenth day and expanded progressively throughout prenatal life. First glandular primordia, one on each side of the septum, were observed during the sixteenth day, the number increased to five at term. The ducts ended in single blind sacs, before the eighteenth day, afterwards, the ducts presented an increasing number of collateral and terminal branches. There was no evidence of mucigen secretion from the septal glands during prenatal life. The initial stratified olfactory epithelium differentiated morphologically into a vestibular, respiratory, and an olfactory epithelium prior to the sixteenth prenatal day.
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    A light microscopic study of the mononuclear cells infiltrating skin homografts in the garter snake, Thamnophis sirtalis (Reptilia: Colubridae)Submitted to the State University of New York, Upstate Medical Center, in partial fulfillment of the requirements for the degree of Doctor of Philosophy. Supported by Training grant GM-00326 and Research grant HD-03484 from the National Institutes of Health. (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972), S. 149-159 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The rejection of skin homografts in the snake, Thamnophis sirtalis is preceded by an infiltration of mononuclear cells into the graft bed. The initial arrangement of infiltrating cells in perivascular halos suggests that these cells emigrate from the blood stream of the host. A cytological study showed that the vast majority of the cells can be classified as small and mediumsized lymphocytes, monocytes and macrophages. Early stages of infiltration were associated with large proportions of lymphocytes while later stages were characterized by a predominance of macrophages. It was concluded that the mononuclear cells associated with graft rejection include large proportions of lymphocytes and macrophages and not just one kind of lymphoid cell.
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    Morphology of the nasal fossae and associated structures of the hamster (Mesocricetus auratus) (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972), S. 161-179 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The hamster nasal cavity consists of vestibular, non-olfactory and olfactory portions. Much of the non-olfactory nasal cavity surface is lined by cuboidal, stratified cuboidal, and low columnar epithelia, devoid of cilia. Goblet cells and ciliated respiratory epithelium are present over only a small portion of the nasal cavity surface.The largest glandular masses in the hamster nose are the maxillary recess glands, the vomeronasal glands and the lateral nasal gland 1; these three glands contain neutral mucopolysaccharides (PAS-positive). Other nasal glands contain both acidic and neutral mucopolysaccharides; the staining reaction for acidic mucopolysaccharide is stronger in goblet cells and olfactory glands than in the other nasal glands.The ducts which open into the nasal vestibule are the excretory ducts of compound tubuloacinar serous glands. The one major PAS-positive gland whose duct opens into the nasal vestibule is the lateral nasal gland 1. The ducts of the compound tubuloacinar vomeronasal glands open into the lumen of the vomeronasal organ, which is connected to the ventral nasal meatus by means of the vomeronasal duct. The ducts of the branched tubuloacinar maxillary recess glands open into the maxillary recess. Few ducts open into the caudal half of the nasal cavity.
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    Granular secretion in the kidney sexual segments of female lizards, Cnemidophorus I. lemniscatus (Sauria, Teiidae) (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972), S. 181-191 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A differentiated segment, analogous in location and structure to the first portion of the sexual segment of the males, but much smaller, is observed in the renal collecting ducts of female C. lemniscatus. In addition to this first portion, with cells full of granules strongly positive to periodic acidleucofuchsin, males have a consecutive second portion, with granules localized only in the apical part of the cells, moderately positive to the reaction mentioned and with a marked affinity for orange G. The two portions of the male sexual segment are considered to correspond to the middle and final parts of the collecting ducts; the initial part in both sexes and the final one in the female are mucigenous.
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    Morphogenesis of intestinal villi. I. Scanning electron microscopy of the duodenal epithelium of the developing chick embryo (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972), S. 193-213 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Development of villi in the duodenum of the chick was studied in stages ranging from 11 days of incubation to one week after hatching. Formation of definitive villi is preceded by development of a set of previllous ridges that run lengthwise along the duodenum. The first set of 16 previllous ridges (Set I) is complete by about 13 days of incubation; all ridges in the set are fairly uniform and proceed through their subsequent development in synchrony. Previllous ridges in Set I fold into a highly regular zigzag pattern between 14 and 16 days of incubation. Definitive villi develop from Set I ridges beginning at about 17 days when populations of distinct cells appear on the crests of the ridges between angles in the zigzag folds. Cells in these populations lack the rounded appearance of cells seen in earlier stages; their apical surfaces are densely covered with microvilli. A second set of villi (Set II) develops at about 16 days of incubation when about 16 rows of tongue-like flaps erupt between the previllous ridges of Set I. At hatching, Set II villi are still smaller than villi of Set I; this distinction disappears by about the fourth day after hatching. The significance of the morphological changes in epithelial cells is discussed in terms of several hypotheses bearing on the mechanisms of villus formation.
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    The relationship of early oocytes to putative neoblasts in the serpulid Spirorbis borealisWork supported by a grant (GB 18429) form N.S.F. (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972), S. 215-227 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The fine structure of the ovary in the serpulid Spirorbis borealis has been described. The ovarian wall consists of from one to several layers of peritoneal cells. Peritoneal cell processes extend deep into the ovary and may be seen between developing oocytes. Although young oocytes may also be in close apposition to one another, intercellular bridges have not been observed. When primary oocytes at the surface of the ovary reach a diameter of about 20 μ, they start to erupt into the coelom. Ovulation results from a simple separation of overlying peritoneal cells which lack specialized cell-to-cell contacts. Once a free surface of an ovulating oocyte is exposed to the coelom, microvilli and primary coat develop. Previtellogenic coelomic oocytes are often observed in close proximity to putative neoblasts (perivasal cells), which suggests a possible functional relationship. The confusion that extists between germ cells, peritoneal cells, and so-called neoblasts in polychaetes is discussed.
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    A new model for the structure of the centriolar satellite complex in spermatozoa (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972), S. 229-241 
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    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 centriolar satellite complex in the spermatozoon of the hydroid, Pennaria, is presented. The complex consists of nine spoke-like arms which emanate from the distal centriole and of nine wedgeshaped connectives which extend into the flagellum joining each of the alpha doublets and the flagellar plasmalemma. Based upon these observations a new model for the structure of the centriolar satellite complex is proposed. In addition, similar centriolar satellite complexes are reported in the spermatozoa of two echinoderms, Ctenodiscus crispatus and Thyone briareus, in support of the proposed model.
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    Masthead (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972) 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051370301
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    Origin of mono- and binucleate cells with heterochromatic chromosomes in the malpighian tubules of the european elm scale, Gossyparia spuria (Coccoidea: Homoptera)Supported by grants GB 6745 and GB 23665 from the National Science Foundation, Washington, D.C. (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972), S. 243-256 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Males of the European elm scale, Gossyparia spuria (Erioccoccidae) have two Malphigian tubules, each made up of mononucleate and binucleate cells. Both types of cells may contain heterochromatic (H) chromosomes which form an H body. The cells with H bodies (H cells) usually appeared singly anywhere along the tubule. However, when two or more H cells were present they tended to be closer to each other than would be expected by chance. The possible origin of this tendency is discussed. Following squashing, the nuclei of the binucleate cells were much larger than those of most other somatic cells, suggesting that they were highly endopolyploid. However, the H bodies of the cells of the tubules were of about the same size as those of the other cells. These observations suggested that the H chromosomes of the binucleate cells did not replicate while the euchromatic chromosomes of these cells replicated several times. The great majority of the nuclei of the H cells contained a single H body per nucleus. An analysis of the number of H bodies in binucleate cells indicated that when two H bodies were present in the same nucleus they usually did not fuse. Thus, they were believed also not to fuse in the mononucleate cells. Since almost all the mononucleate H cells had only a single H body (rather than 2) it was concluded that they did not originate from binucleate cells by nuclear fusion.
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    Ultrastructure of the parathyroid gland of fresh-water turtles (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 138 (1972), S. 131-140 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The parathyroid glands of fresh-water turtles (Pseudemys scripta and Chrysemys picta) are composed of cords of cells in which dark and light variants of chief cells and occasional oxyphil cells can be distinguished. Cytoplasmic granules measuring about 0.3-0.4 μm and all the cellular organelles associated with protein and carbohydrate synthesis can be seen in both dark and light chief cells; the cytoplasm of oxyphils is packed with mitochondria which obscure other organelles. An unusual feature of the dark chief cells is the presence of crystalline-like material within parallel arrays of cisternae of rough endoplasmic reticulum. A similar crystalline-like structure is seen occasionally within some cytoplasmic granules.
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    The anatomy, physiology, functional significance and evolution of specialized hearing organs of gerbilline rodents (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 138 (1972), S. 41-120 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Middle and inner ear anatomy correlates with neurophysiological responses to a wide range of sound frequencies for species of the Gerbillinae representing generalized, intermediate, and specialized anatomical conditions. Neurophysiological data were recorded from 81 specimens of 13 species representing six genera. Anatomical parameters involved in the process of hearing were correlated with the neurophysiological data to assess the effects of different degrees of anatomical specialization on hearing. The 13 species tested in this manner have graphic curves of auditory sensitivity of remarkably similar disposition over the frequencies tested and to those published for Kangaroo Rats. Ears with anatomical specializations show greater auditory sensitivity.The natural history of the Gerbillinae, particularly the kinds of predators, degree of predation, and habitat is reviewed and utilized to interpret the significance of the degree of auditory specialization in the forms studied and to evaluate the prevailing hypothesis that these specializations enhance the ability of these rodents to survive in open desert situations by detecting and evading predators.The middle ear anatomy of five additional genera and species was also studied. Thus, data on the entire spectrum of gerbilline middle ear morphology provide an evolutionary sequence. Certain anatomical parameters of the organ of Corti show a degree of specialization parallel to that of features of the middle ear. The morphological changes and possible functional roles of these features are considered.A very high correlation exists for degree of specialization and aridity of habitat, thus specialization increases with increasing aridity. This increased specialization may result from more effective predation in open xeric environments. Auditory acuity for a wide range of low frequency sounds augmented by auditory specialization is hence more advantageous here. There does not appear to be selection for hearing at particular frequencies in this range. The peaks of greatest auditory sensitivity appear to correspond to the resonant frequencies of the different components of the middle ear transformer and cavity.
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    Embryology of the sheep. II. The alimentary tract and associated glands (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 138 (1972), S. 187-205 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The day-by-day development of the alimentary system of the sheep embryo from 14 to 34 days is documented and described. This includes development of the mouth, the pharynx and its derivatives, esophagus, stomach, intestine, cecum, pancreas and liver.This work provides standards within the normal range of development of the ovine alimentary system on which studies of abnormal development can be based.
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    Embryology of the sheep. I. Extraembryonic membranes and the development of body form (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 138 (1972), S. 169-185 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The developmental anatomy of the sheep in the early prenatal period (14 to 34 days) was studied using embryos of known coital age, and embryos of known size with estimated coital age. Characteristics of the embryos were studied by gross observation under the dissecting microscope, and by means of serial sections. The period of the ovum (from conception to 10 days) and the early embryonic period (from 11 to 14 days) are summarized from the literature.This work provides a detailed, systematic account of embryonic development in the sheep and establishes size-age standards. Anatomical features encountered in the normal development of the sheep embryo are documented day-by-day because they are essential for studies of teratogenesis and early prenatal mortality.
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    Skeletal morphology of the mud star, Ctenodiscus crispatus (Echinodermata: Asteroidea) (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 138 (1972), S. 239-262 
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    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 following eight major ossicle types is described and illustrated for the goniopectinid asteroid Ctenodiscus crispatus: terminal plates, superomarginal and inferomarginal ossicles, adambulacral and ambulacral ossicles, odontophores, oral intermediate plates, and superambulacral ossicles. Development, variation, and relationships with soft body-parts and with other ossicles are embphasized. Each ossicle type is distinguished by numerous structures related to its function and to articulation with adjoining skeletal elements. Because major structures (such as pustules, alveoli, and articulation surfaces) distinguishing ossicle types develop early during ontogeny, immature ossicles are readily identifiable. However, changes in form and orientation of these structures occur during ossicle growth. Ontogenetic changes are influenced by development of associated skeletal and soft parts. Ambulacral and adambulacral ossicles near the peristome are highly modified but retain the basic characteristics of structure and orientation which define these major types of skeletal elements.
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    An ultrastructural analysis of mitosis and cytokinesis in the zygote of the sea urchin, Arbacia punctulataThis investigation was supported in part by grants [HD-36162, HD-05846, and HD-04924 (awarded to Dr. Everett Anderson)] from the National Institutes of Health and was carried out in the laboratory of Dr. Everett Anderson, the Department of Zoology, University of Massachusetts. The assistance of Mrs. Ellen Looney is gratefully appreciated. (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 138 (1972), S. 207-237 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Post-fertilization events leading to the cleavage of the zygote of the sea-urchin, Arbacia punctulata were examined with the light and electron microscopes. Prior to prophase of the first cleavage division, endoplasmic reticulum and annulate lamellae become organized around the zygotic nucleus to produce a crescent-shaped structure which is defined as the streak (Harvey, '56). With the advent of prophase the streak undergoes morphogenic events which lead to the formation of the mitotic asters. During this transition there is a loss of annulate lamellae and a concomitant increase in endoplasmic reticulum. Annulate lamellae are not found as a part of the mitotic apparatus and are not again observed within the embryo until the two cell stage. During telophase, karyomeres are formed which consist of chromosomes delimited by a porous bilaminar envelope. Blastomere nuclei are produced following the fusion of the outer laminae, and subsequently by the fusion of the inner laminae of the envelopes encompassing the karyomeres.
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