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  • 1985-1989  (10,611)
  • 1980-1984  (7,205)
  • Cell & Developmental Biology  (10,763)
  • Chemical Engineering  (6,138)
  • Ultrastructure  (929)
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  • 101
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1340-1367 
    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: Studies of strength development at polymer-polymer interfaces are examined and applications to welding of similar and dissimilar polymers are considered. The fracture properties of the weld, namely, fracture stress, σ, fracture energy, GIc, fatigue crack propagation rate da/dN, and microscopic aspects of the deformation process are determined using compact tension, wedge cleavage, and double cantilever beam healing experiments. The mechanical properties are related to the structure of the interface via microscopic deformation mechanisms involving disentanglement and bond rupture. The time dependent structure of the welding interface is determined in terms of the molecular dynamics of the polymer chains, the chemical compatibility, and the fractal nature of diffuse interfaces. Several experimental methods are used to probe the weld structure and compare with theoretical scaling laws, Results are given for symmetric amorphous welds, incompatible and compatible asymmetric amorphous welds, incompatible semicrystalline and polymer-metal welds. The relevance of interface healing studies to thermal, friction, solvent and ultrasonic welds is discussed.
    Additional Material: 33 Ill.
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  • 102
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1387-1395 
    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 integrity of a pipeline system is determined by its weakest links. Joints may be such places. Heat fusion is the most common joining method for distribution gas piping. There are procedural, thermal, and mechanical aspects of making fusion joints. Procedural aspects, such as heater calibration and cleanliness, can be assured only by rigorous training and certification of the operators. Thermal and mechanical aspects consist of specifying joining conditions such as the heater temperature, heating time, and joining pressure. In the absence of procedural errors, the strength of a fusion joint should depend on the pipe material, pipe dimensions, and the thermal and mechanical joining conditions.The measured parameters that are measures of strength are impact energy and location of failure in the tensile impact test. A parameter, termed the joining parameter, was found to characterize the joining conditions. This parameter is a function of bead volume, melt volume at the end of the heating phase, and pipe wall thickness. Of the mechanical test parameters, the impact energy was found to correlate best with the joining parameter.
    Additional Material: 13 Ill.
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  • 103
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1413-1418 
    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 variety of thermoplastic fully imidized poly(imide siloxane) segmented copolymers with useful thermal and mechanical properties have been prepared. Other interesting properties described are the materials' hydrophobic character, surface domination, UV stability, and atomic oxygen plasma resistance.
    Additional Material: 7 Ill.
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  • 104
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1446-1455 
    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 study deals with the cold compaction of polyether-etherketone (PEEK) and nickel powder blends. Four different types of PEEK powders which are commercially available from Imperial Chemical Industries (ICI) were utilized for this investigation. These PEEK powders included fine and coarse size powders of a low viscosity grade (150PF and 150P) and similar powders of a high viscosity grade (450PF and 450P). Each of the four different PEEK powders were blended with about 10 vol-% nickel powder (Novamet) using a dry mixing technique. These PEEK/nickel powder blends were then successfully compacted at room temperature. Green strengths as high as 39.5 MPa and 26.3 MPa were measured on nickel filled 150 grade and 450 grade compacts, respectively. The higher strength values of the nickel filled compacts compared to their respective unfilled ones were attributed to a higher degree of mechanical interlocking and plastic deformation, which was induced in the polymer particles during compaction by the hard nickel filler. These composites also exhibited lower viscoelastic recoveries than their respective unfilled compacts. Electrical resistivities as low as 0.06 ohm-cm were achieved by compacting 150P/nickel powder blends. This resistivity value agreed well with the calculated value predicted from the literature.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 105
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1456-1465 
    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 study deals with the characterization and cold compaction of polyetheretherketone (PEEK) powders. Four different types of PEEK powders which are commercially available from Imperial Chemical Industries (ICI) were characterized for density, crystallinity, particle size, particle size distribution, and particle morphology. Fine and coarse size powders of a low viscosity grade (150PF and 150P) and similar powders of a high viscosity grade (450PF and 450P) were processed. Compaction was successful at room temperature using the 150 grade powders but not with the 450 grade powders. Compressibility curves were obtained at room temperature for the 150 grade powders and their post-compaction viscoelastic recoveries were measured. The coarse and fine size 150 grade powders reached relative plateau densities of 95.8% and 95.1%, respectively, when compacted at pressures exceeding 300 MPa. These high densification values at room temperature were associated with minimal post-compaction viscoelastic recoveries and as-compacted strengths as high as 8.9 MPa. A modified densification parameter (DP*) was developed based on the plastic deformation of the crystalline regions alone. This new dimensionless parameter, DP*, demonstrated a better fit of all the compaction data. The transverse rupture strength and the green density data are presented and explained in terms of this DP*.
    Additional Material: 12 Ill.
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  • 106
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    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
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  • 107
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1528-1533 
    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 study was conducted of blends of poly(vinyl chloride) (PVC) with a poly(methyl methacrylate co imide). The latter polymer was found to be miscible in PVC and to raise the glass transition temperature of the blend. Blends of all compositions could be oriented, but the processing temperature increased in proportion with Tg. For a given blend composition, orientation increased with increasing stretch ratio and strain rate and with decreasing stretch temperature. Increasing copolyimide content and increasing orientation generally lead to improved mechanical properties, though the blends containing high levels of copolyimide exhibited low ductilities.
    Additional Material: 14 Ill.
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  • 108
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1574-1578 
    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 optical properties of polyetherimide resin as described by the complex index of refraction, N = n - ik, are derived by Kramers-Kronig analysis of experimental absorption and reflectance data obtained in the range 40 μm ≥ λ ≥105 nm. Potential uses of this polymer as a printed circuit board material and as a packaging medium for microelectronic circuitry and the relevance of optical data in laser-assisted processing schemes used in these and other applications are briefly discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 109
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 214-226 
    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: Shear modification treatment represents a special shearing history affecting mainly the elastic behavior of polymer melts. This process has been attributed to reversible physical changes in the entanglement structure of the polymer chain network. Shear modification studies were performed for two well-characterized low-density polyethylene (LDPE) grades differing in molecular weight distribution and degree of long chain branching. The shear working of the material was carried out using a specially designed shearing unit producing definable amounts of pure shear in a continuous process. Measurements of the dynamic storage modulus, G′, steady-state shear compliance; Je, extrudate swell, melt flow index, and the extensional behavior (Rheotens test) indicate that primarily properties associated with the elasticity of the melt are reduced in value. The observed reduction is found to correlate with the mean specific energy dissipated during sample preparation. Comparing the two LDPE grades showed that higher degrees of modification can be obtained at lower energy input levels for the more highly branched grade. Reversibility tests were performed and complete recovery of the initial material behavior was observed. Comparison of measurement results for samples prepared using the shearing unit presented here and a Brabender Plasticorder indicates that the degree of modification depends not only on the molecular structure of the polymer but also on the manner in which the shearing history is imposed upon the material.
    Additional Material: 20 Ill.
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  • 110
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    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
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  • 111
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1637-1637 
    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
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  • 112
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1628-1635 
    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 compressive and tensile properties of polyester mortar were studied under various curing conditions, temperature, and strain rate. The curing temperature was varied from room temperature to 80°C. The behavior of polyester mortar was studied using a uniform sand with strain rate and temperature varied between 0.01 to 6 percent strain per minute and 22°C and 120°C, respectively. The strength, failure strain, modulus and stress-strain relationships of polyester mortar are influenced by the curing method, testing temperature, and strain rate to varying degrees. The influence of test variables on the mechanical properties of polyester mortar are quantified. Pretreating the aggregates with a silane coupling agent further enhances the compressive and tensile strength of the mortar. The compressive modulus and splitting tensile strength of polyester mortar are related to the compressive strength. A constitutive model is used to predict the compressive stress-strain behavior of polyester mortar.
    Additional Material: 13 Ill.
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  • 113
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1667-1676 
    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: Under the right conditions, high strengths are shown to be achievable in vibration welded polycarbonate to polyetherimide Joints. While welding of thermoplastic interfaces of the same material can be understood in terms of interchain diffusion at elevated temperatures, this mechanism is severely limited in the case of dissimilar materials. Scanning electron microscopy is used to show that part of the bond strength in such dissimilar materials results from mechanical interlocking of the two polymers, which is caused by viscous mixing. The effects of the weld parameters on the weld morphology are considered in detail.
    Additional Material: 19 Ill.
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  • 114
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1689-1698 
    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: Ultrasonic welding is one of the most popular techniques for joining thermoplastics because it is fast, economical, and easily automated. In near-field ultrasonic welding, the distance between the horn and the joint interface is 6 mm or less. This study investigated the near-field ultrasonic welding of amorphous (acrylonitrile-butadiene-styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. High frequency ultrasonic wave propagation and attenuation measurements were made in order to estimate the dynamic mechanical moduli of the polymers. The estimated moduli were entered into a lumped parameter model in order to predict heating rates and energy dissipation. Experimental results showed that variations in the welding pressure had little effect on energy dissipation or joint strength; Increasing the amplitude of vibration increased the energy dissipation and the weld strength. For the semicrystalline polymers, increasing the weld time improved strength up to weld times greater than 1.5 s, where strength leveled off. For the amorphous polymers, the weld strength increased with Increasing weld time up to times of 0.8 s; for longer weld times, the power required was too high, causing overloading of the welder. Monitoring of the energy dissipation and static displacement or collapse provided valuable information on weld quality.
    Additional Material: 16 Ill.
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  • 115
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1733-1737 
    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 hydrolytic stability of a new commercial polycarbonate (Calibre 300, Dow Chemical USA) was investigated and compared with that of other commercial polycarbonates. The tests were conducted between 56% and 95% relative humidity (R. H.) at 100°C. Also performed were water immersion tests at 80 and 100°C. The water diffusivity was found to be 8.7 × 10-7 cm2/s at 100°C with an activation energy of 7.9 kcal/mole. These values are similar to other glassy polymers. The equilibrium water sorption, C∞, was found to increase with temperature and R.H. The isotherm at 100°C was determined to be: C∞ = 0.005945 [R.H.]. When samples immersed in a water bath at 100°C were transferred into room-temperature water, visible aqueous microcavities were formed due to the condition of super-saturation, and under stress may become crack initiation sites. For the polycarbonate investigated here, it was found that the decrease in weight-average molecular weight (M̄)w was a first-order process under a constant R.H. and temperature, and that hydrolytic embrittlement, i. e., (M̄)w 〈34,000, was reached after ca. 188, 143, 99, and 66 days under 56%, 73%, 87%, and 95% R.H., respectively, at 100°C. A comparison with reported hydrolytic stability data for other polycarbonates showed large differences in their stability which are believed to be due to the extent of end-group capping (over 95% in Calibre 300) and resin purity: both phenolic end-groups and some additives (i.e., fire retardants, thermal stabilizers) are known to accelerate hydrolytic degradation.
    Additional Material: 8 Ill.
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  • 116
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1766-1773 
    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: Moldability and mechanical properties of polyethylene terephthalate (PET) under normal molding conditions were found to improve significantly when it was blended with bisphenol-A-polycarbonate (PC) and polypropylene (PP) to form ternary polymer blend systems. DSC results of these blends revealed that the PET and PC components formed a miscible blend while PP being incompatible with them, formed a separate phase. PP was also found to form a sleeve around the PET-PC miscible phase and, thereby, showed a skin-core type of morphology. Variations of mechanical properties with varying amounts of PP was measured keeping the ratio of PET and PC constant. Tensile and flexural properties of the blends decrease with the amount of PP. Notched impact strength increases up to a certain level of PP and then decreases, while the unnotched values decrease gradually. The effect of annealing on the mechanical properties of these blends have been discussed on the basis of the increased crystallinity of some of the components.
    Additional Material: 9 Ill.
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  • 117
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1786-1795 
    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 possible multimodal sorption mechanisms in glassy amorphous poly-ether-ether-ketone (PEEK) are presented. By varying the penetrant-polymer affinity, experimental temperature, and external solvent activity, a broad range of sorption behaviors from ideal Fickian diffusion to limiting relaxation controlled kinetics is observed. In particular, water, methylene chloride, and n-heptane sorption kinetics are analyzed and interpreted on the basis of the multiple transport mechanisms. Low uptake liquid n-heptane sorption follows ordinary Fickian diffusion. Analogously, water vapor at low activity, is sorbed in small amounts in the same limiting mode while, at higher activities, the moderately higher penetrant uptakes induce slow relaxation coupled with ideal Fickian diffusion. The highly interacting methylene chloride leads to ideal Fickian diffusion only at very low activities, while anomalous non-ideal Fickian diffusion and limiting Case II and diffusion controlled swelling are observed at moderate and at high solvent activities, respectively. Limiting Case II sorption of methylene chloride in PEEK has been observed only at a very low temperature (-32°C). The optical microscopy observations of cryogenically fractured samples contacted with liquid methylene chloride at 5, 20 and 36°C revealed the presence of a sharp front moving linearly with the square root of time. Solvent induced crystallization in methylene chloride swollen samples was detected by means of differential scanning calorimetry (DSC) and wide angle X-ray scattering (WAXS). Finally, sorption from liquid methylene chloride/n-heptane solutions with varying compositions are presented. The progressive increase of the more high sorbing methylene chloride concentration in the solutions, leads to the same wide variety of sorption behavior observed in the methylene chloride vapor sorptions. The gas chromatographic (GC) analysis indicated that the presence of methylene chloride enhanced the n-heptane sorption in the polymer.
    Additional Material: 19 Ill.
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  • 118
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1649-1654 
    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: Welding represents one of the key stages in the manufacture of injection molded or blow molded plastics products. One process frequently employed is heated-tool butt welding. However, the high seam quality associated with this process can only be attained through reliable process control and optimized welding parameters. This paper presents a simple new method for determining these parameters. Mathematical and physical descriptions of the individual process stages and a computer-controlled heated-tool butt welding machine serve as the basis for determining the parameters.
    Additional Material: 8 Ill.
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  • 119
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    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1661-1666 
    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 measuring method is presented for process monitoring and process analysis of linear vibration welding of thermoplastics. The method works by recording and evaluating time-dependent signals that describe the process - such as the frequency-dependent signals of the displacement of the two parts being joined, the tangential force in the welding plane - and the nonperiodic signals of the welding process, i.e. the normal force in the welding plane and the melting or joining displacement of the parts being joined. It is possible to determine the energy input into the welding zone as a function of the selected machine parameters and the process sequence over time.
    Additional Material: 12 Ill.
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  • 120
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1699-1704 
    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: In far-field ultrasonic welding of plastic parts the distance between the ultrasonic horn and the joint is greater than 6 mm. This study investigated the farfield ultrasonic welding of amorphous (acrylo butadiene styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. Far-field welding worked well for amorphous polymers. Weld strength improved substantially with increasing amplitude of vibration at the joint interface. Increasing the weld pressure and/or the weld time also resulted in higher weld strengths. Far-field ultrasonic welding was not successful for semicrystalline polymers. The parts melted and deformed at the horn/part interface with little or no melting at the joint interface. A model for wave propagation in viscoelastic materials, which was developed to predict the vibration amplitude experienced at the joint interface, indicates that increasing the length of the samples to a half a wavelength should improve the far-field welding of semicrystalline polymers by maximizing the amplitude of vibration at the joint interface.
    Additional Material: 12 Ill.
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  • 121
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    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
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  • 122
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    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1746-1758 
    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 methodological survey of preparation of microspheres and microcapsules by suspension cross-linking is presented. Thus, basic features of suspension cross-linking, i.e., the formation of small droplets of a polymer solution (or melt) in an immiscible liquid followed by hardening of these droplets by covalent cross-linking, are discussed. Typical microspherical and microcapsular products manufactured by suspension cross-linking of naturally occurring and preformed synthetic polymers, including agarose and cellulose beads, albumin microspheres and microcapsules, polystyrene beads and epoxy resin microcapsules, are described. Manufacturing parameters controlling microsphere/microcapsule characteristics are also briefly outlined.
    Additional Material: 10 Ill.
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  • 123
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    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
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  • 124
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1325-1331 
    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: In structures composed of polymer matrix composite materials, components must be joined such that the overall structure retains its structural integrity while it is performing its, intended function which can include both mechanical loads (static and dynamic) and environmental loads (temperature and humidity). The use of composite materials in complex structures almost always reduces the number of components in the structures compared to the use of metallic alloys for the same structure. Thus, using composite materials not only results in great savings in weight, but also through a reduced number of joining operations, results in significant savings in assembly, inspection, parts storage, and movement, resulting in increased reliability and lower cost. Yet joining is still required. Joining metallic structures is a mature technology involving riveting, bolting, welding, glueing, brazing, soldering, and other methods. However, for most polymer matrix composites only adhesive bonding and mechanical fastening can be utilized. Attention has been given recently, however, to localized welding of thermoplastic polymer matrix composites, and this will be discussed briefly later. Inherently, adhesive bonding is preferable to mechanical fastening because of the continuous connection, whereas in drilling holes for bolts or rivets, fibers or other reinforcements are cut, and large stress concentrations occar at each discrete fastener hole. The following is a review of much of the literature dealing with adhesive bonding of polymer matrix composite structures. It is Intended not only to be a review, but also a background for detailed study of the referenced and other documents, and a catalyst for future research.
    Additional Material: 5 Ill.
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  • 125
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1488-1491 
    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: Gelation phenomenon in thermoset polymers is an area of extreme importance from the processing point of view. Gel point (GP) has traditionally been detected using rheological and mechanical techniques. We wish to report the use of dielectric and especially calorimetric techniques for detecting GP. Using a particular thermoset system, we have compared the calorimetric, dielectric, and mechanical techniques and shown how to define GP in terms of time and temperature. As a matter of convenience, we have briefly defined the gelation phenomenon in thermosets, its significance and measurement, and a critical evaluation of the techniques for detecting GP.
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  • 126
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    Polymer Engineering and Science 29 (1989), S. 1516-1523 
    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 study of orientation development in polystyrene film by biaxial stretching is described. Stretch ratios up to 7.2 × 7.2 were used. Mechanical properties of polystyrene films were correlated with the level of molecular orientation developed by uniaxial or biaxial stretching. Sensitivity of the mechanical properties to change due to development of orientation varied as follows: Yield strength 〈 Young's modulus 〈 Tensile strength 〈 Elongation to break. Brittle to ductile transition phenomena were observed at certain orientation values in the orientation triangle diagram. The transition occurs when f1B × f2B ∼ 0.0025 for biaxially oriented and f1B ∼ 0.015 in the machine direction for uniaxially oriented films. SEM photomicrographs show that the fracture surfaces of ductile failures exhibit many fibrils while brittle failures exhibit no fibrils.
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  • 127
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    Polymer Engineering and Science 29 (1989) 
    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
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  • 128
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    Polymer Engineering and Science 29 (1989), S. 1579-1587 
    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 general kinetic model was developed to simulate the grafting of monomers such as unsaturated carboxylic acids and silanes to ethylene polymers. The polymers considered were ethylene-co-vinyl acetate (EVA), ethylene-co-butyl acrylate (EBA), and low-density polyethylene (LDPE). Grafting was assumed to proceed by a free-radical mechanism involving chain transfer. Organic peroxides having a strong tendency for hydrogen abstraction were selected as the source of primary radicals. The model simulated the grafting reaction as taking place in a single screw extruder. The residence time distribution in the extruder was experimentally determined by tracer analysis, according to which the extruder was a plug-flow reactor connected to two mixed reactors in parallel. The model is able to predict the extent of grafting in terms of predefined parameters. Comparison of model predictions with available experimental data showed slight deviations, the possible causes of which are discussed. However, the kinetic behavior expected on the basis of the input parameters was observed, and, as such, the model allowed study of the effect of process variables on grafting kinetics and provided insight into the reaction mechanism.
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  • 129
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    Polymer Engineering and Science 29 (1989), S. 1598-1603 
    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 characterizations performed on two types of polyethylene T-Joints as well as the starting resin from which they were manufactured. It was found that the melt flow rate of material taken from the two types of joints differed from that of the starting resin and differed from each other by as much as a factor of two. Investigation of the environmental stress-crack resistance (ESCR) and uniaxial creep behavior of material from the two joints revealed further significant differences in behavior between the two joints. These observations lead to the conclusion that subtle differences in the processing conditions can result in significant differences in the long-term mechanical behavior.
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  • 130
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    Polymer Engineering and Science 29 (1989), S. 1614-1617 
    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 tensile strength of solid-filled rubbers is predicted by the statistical model proposed in this paper, by which the maximum area fraction of the solid filler in a representative cube is calculated. The minimum net cross-section area of the rubber matrix is thus obtained, and this is used to calculate the reduction in strength of the compound in comparison to that of the unfilled rubber. The prediction is then tested by experiments using hydroxyl-terminated polybutadiene (HTPB) filled with glass spheres. After curing, tensile specimens were cut from sheets and exposed to humidity-controlled environments so as to debond the filler particles from the rubber matrix, and were tested in tension. The experimental results were found consistent with the predictions.
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  • 131
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    Polymer Engineering and Science 29 (1989), S. 1683-1688 
    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: In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. Past work on welding characterized the effects of weld parameters such as the weld frequency, the weld pressure, and the weld time, on the welding process and weld strength, and showed that the most important parameter affecting weld strength Is the weld penetration - the decrease in the distance between the parts being welded that is caused by lateral outflow of material in the molten film. However, those weld studies were based on specimens of constant nominal thickness (6.35 mm, 0.25 in). This paper is concerned with the effects of specimen thickness on the weld process and weld strength.
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  • 132
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    Polymer Engineering and Science 29 (1989), S. 1722-1729 
    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 transient two-dimensional thermal model for resistance welding of thermoplastic composites is presented. A parametric study is conducted that yields insight into the welding process enabling some critical process and material parameters to be identified. Time to melt is predicted by the model and is successfully compared to experimental observations. Local heating and meltthrough can also be explained by the transient thermal model in agreement with experimental observations. Mode I fracture toughness of unidirectional graphite reinforced poly(etheretherketone) resistance welded double cantilever beam specimens are conducted under various process conditions. Experimental results indicate that under optimum process conditions, the interlaminar fracture toughness of the bulk compression-molded thermoplastic composite material can be achieved using resistance heating as a joining technique.
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  • 133
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    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: Although fibers are subject to complex deformations during processing and end use, most research has concentrated on tensile properties. We have extended our studies to include the ultimate torsional properties, i.e., the breaking twist angle (BTA), and the flexural fatigue life of single fibers. We now have sufficient data on diverse fiber types that we may compare their mechanical properties. Thus, in this paper we report the mechanical properties of the different starting, untreated, fibers, tested under fiducial conditions. We then develop and consider some interrelationships between these selected single fiber physical properties.
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  • 134
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    Polymer Engineering and Science 29 (1989), S. 1774-1785 
    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: We have analyzed step growth polymerization in a flat film with finite mass transfer resistance. We have shown rigorously that the molecular weight distribution (MWD) at equilibrium is given by the Flory distribution, and under reaction the form of the MWD does not change if the feed is either pure monomer or in equilibrium initially. Extensive computations have shown that it is possible to split the film into growing interfacial and shrinking bulk regions. It is possible to obtain similarity transformations of concentrations of condensation product, and polymer as time invariant profiles. Based on this finding, we have determined a solution for step growth polymerization with finite mass transfer in films. The results lie within 5% of the “exact” numerical computations, for all possible variations of parameters.
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  • 135
    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 analysis of oriented polymers involves several transitional processes which may be coupled in a complex way. The disorientation process that occurs during heating is often accompanied by dimensional shrinkage which may occur in both amorphous and crystalline oriented polymers. From differential scanning calorimetry (DSC) measurements it has been determined that shrinkage is an exothermic process. In amorphous atactic polystyrene (PS), hot drawn uniaxially, the shrinkage occurs just above Tg. In triaxially oriented polyethylene (PE) and isotactic polypropylene (iPP), shrinkage and melting take place concomitantly, producing multiple melting peaks. In rolltruded (and also in biaxially oriented) poly(ethyleneterephthalate) (PET) films, shrinkage and crystallization are found to be coupled and to occur between Tg and Tm upon heating. If the enthalpy contribution due to shrinkage is ignored, it follows that crystallinities determined by DSC are incorrect. In this study, the influence of shrinkage upon transitional changes in oriented polymers is investigated in a systematic manner.
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  • 136
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    Polymer Engineering and Science 29 (1989), S. 1534-1543 
    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: We offer a detailed study on the anisotropic optical properties in uni and simultaneous biaxially stretched Poly(ethylene terephthalate) (PET) films. Cast amorphous sheets of PET were stretched to a series of extension ratios in two mutually perpendicular directions at 80, 90, and 100°C. Additionally, 0selected films were subsequently “heat-set” by annealing with their width and lengths constrained. The principal refractive indices at sodium D wavelength of these, asstretched and heat-set films were obtained using a modified Abbe refractometer. The changes in the principal refractive indices with the processing history were correlated with the orientation of PET chains and phenyl plane normals, which were determined independently by wide angle X-ray (WAXS) pole figure technique.
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  • 137
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    Polymer Engineering and Science 29 (1989), S. 1642-1648 
    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: In order to achieve high fatigue strengths in heated-tool butt welds in plastic pipes used in gas and water supply lines, it is essential that optimum welding parameters be selected. In this paper, the different process phases are described by means of dimensionless characteristic parameters that have been obtained by applying similarity principles to heated-tool butt welding. On the basis of strength studies conducted on welded Joints, it is shown that the best weld quality is attained when the welding parameters are selected such that identical sheaf deformations result in the joint zones of small and large pipes. Laws for scaling data from small-pipe to large-pipe welds are then based on the values of these nondimensional numbers.
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  • 138
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    Journal of Morphology 199 (1989), S. 165-174 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: During ontogeny, the apical and basal components of dicamptodontid teeth exhibit three major developmental stages: nonpedicellate, subpedicellate, and pedicellate. Premetamorphic larvae tend to have nonpedicellate teeth, incompletely or recently metamorphosed individuals tend to have subpedicellate teeth, and fully transformed adults usually have pedicellate teeth. In concert with this transition, cusp morphology is modified from a larval monocuspid, to an incipiently bicuspid, to definitive adult bicuspid, and finally to an adult monocuspid condition. Thus, the larval and adult monocuspid conditions are ontogenetically distinct. The morphology of the larval monocuspid, adult bicuspid, and adult monocuspid conditions differs between Dicamptodon and Rhyacotriton. However, the incipient bicuspid condition in these two genera is very similar in appearance, suggesting that Dicamptodon and Rhyacotriton may be more closely related to each other than to the family Ambystomatidae in which they both sometimes are placed. The method of establishing ontogenetic trajectories seems to be preferable to comparisons based on adult structure, since similarities in the morphology of adults often is owing to convergent or parallel evolution.
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  • 139
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    Journal of Morphology 199 (1989), S. 207-221 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Comparative morphological analysis of the female reproductive tract in macroglossine bats was undertaken to test the hypothesis that nectarivory arose at least twice within Old World fruit bats. Given that features of the female reproductive tract are not directly involved in adaptations for feeding, this data set should provide a test of the monophyly of macroglossine bats. A cladistic analysis of variation in the structure of the ovaries, oviducts, uterus, and external genitalia supports the hypothesis that Megaloglossus has developed a nectar-feeding habit independent of other macroglossine genera. Most of the variation in female reproductive organs among pteropodids is found in the development of derived external and internal features of the uterus. Fusion of uterine cornua, expansion of the common uterine body, and elaboration of the cervical region are found in a group which includes species of Pteropus, Dobsonia, Nyctimene, and the macroglossines (excluding Megaloglossus). Results of this study are concordant with independent data sets, thus providing a phylogenetic framework to evaluate critically structural and functional design in the evolution of pteropodid feeding mechanisms.
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  • 140
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    Journal of Morphology 200 (1989), S. 269-300 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Descriptive data are provided for ontogeny of bone to metamorphosis in the myobatrachine species Uperoleia trachyderma; in pre- and postmetamorphic specimens of U. lithomoda, Crinia signifera, and Pseudophryne bibroni; and in postmetamorphic specimens of U. laevigata. Data derived from postmetamorphic U. laevigata indicate that dermal and endochondral elements ossify independently of each other in Uperoleia. Crinia signifera does not show the same degree of independence of ossification of dermal and endochondral elements as Uperoleia, whereas dermal and endochondral elements are not independent in P. bibroni. Ten (or possibly eleven) features are identified as being influenced by heterochrony within Uperoleia, confirming that the genus represents a highly pedomorphic lineage, four elements are influenced by heterochrony in Crinia, but only two in Pseudophryne.
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  • 141
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    Journal of Morphology 200 (1989), S. 301-319 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Investigation of eight developmental stages by means of serial sections and subsequent graphic or wax model reconstructions, as well as by means of cleared-and-stained and dissected material, revealed that the ethmoidal endocranium in Pipa pipa consists in early states of a single horizontal ethmoid plate lacking labial cartilages. Later in the course of development, structures comparable with those in other anurans appear, though modified and of reduced size. These adult structures arise from the new cartilaginous tissue located above the former larval ethmoid plate, whereas the latter entirely disappear. This phenomenon can be observed also in P. carvalhoi and in Xenopus laevis; hence, it supposedly occurs in all pipids. On the other hand, in anuran larvae, which develop cornua trabecularum in the ethmoidal region, these persist in adults as part of the nasal septum. Positional and developmental differences suggest that, although the ethmoid plate and the cornua trabecularum arise from the same region of the cranial neural crest, they are not fully corresponding structures. Comparison with adults of other pipid genera confirmed the conclusion of some earlier investigators that P. pipa is the most specialized among pipids.
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  • 142
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The Harderian gland of the musk shrew Suncus murinus is elongated anteroposteriorly from in front of the eye to behind the ear. The gland is divided into two portions: an anterior portion (A portion) and a posterior portion (P portion). The single secretory duct of the gland emerges from the anterior end of the P portion, receives several secretory ducts of the A portion during the course along it, runs around the ventral aspect of the eyeball, and finally opens into the anterior corner of conjunctival sacs. The two portions of the gland show a fundamentally similar histological structure, having a poorly developed intraglandular duct system and wide tubular alveoli. The quantity of lipid vacuoles and stromal connective tissue in the A portion is greater than in the P portion. The lipid vacuoles in both portions are surrounded by unit membranes, but their contents appear different.The lacrimal gland of the musk shrew is located along the ventral side of the P portion of the Harderian gland. The lacrimal duct emerges from its anterior end, runs around the ventral and anterior aspects of the ear, crosses the A portion of the Harderian gapos; and, and finally opens at the posterior corner of conjunctival sacs. The lobules of the lacrimal gland comprise a branched duct system and terminal acini with two types of secretory cells: (1) acidic cells positive both for the periodic acid-Schiff reaction (PAS) and for Alcian blue (AB) and (2) neutral cells positive for PAS and negative for AB. Both cell types tend to make separate acini, but when present in the same acinus, the acidic cells occupy relatively peripheral positions in the acinus. Both cell types lack intercellular canaliculi.On the basis of the present study as well as previous descriptions in the literature, the author suggests that the mammalian lacrimal glands can be divided into two sets: (1) a Glandula lacrimalis superior with multiple secretory ducts associated with the upper eyelid and (2) a Glandula lacrimalis inferior with a single secretory duct opening into the lateral corner of the conjunctival sacs. These glands have a fundamentally similar histological structure; but in the rabbit, which possesses both sets of lacrimal glands, they are different. On the other hand, the secretory cells of lacrimal glands generally have no intercellular secretory canaliculi, which are characteristically present between the serous secretory cells of the salivary glands.
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  • 143
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The leg musculature from 11, 14, and 17 day chick embryos was analyzed histochemically to investigate the temporal and spatial distribution of various types of sulfated glycosaminoglycans present during skeletal muscle development. Types of glycans were identified by selective degradation with specific glycosidases and nitrous acid coupled with Alcian blue staining procedures for sulfated polyanions and with [35S]sulfate autoradiography. On day 11, radiolabeled chondroitin sulfate glycosaminoglycans are localized extracellularly in both the myogenic and connective tissue cell populations. By day 17, incorporation of [35S]sulfate into chondroitin sulfate is substantially reduced, although Alcian blue-stained chondroitin sulfate molecules are still detectable. With increasing age and developmental state of the tissues, radiolabeled and stained dermatan sulfate and heparan sulfate progressively increase in relative quantity compared to chondroitin sulfate both in muscle and in associated connective tissue elements. These changes in glycosaminoglycans correlate well with similar changes previously determined biochemically and further document the alterations in extracellular matrix components during embryonic skeletal myogenesis.
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  • 144
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    Journal of Morphology 201 (1989), S. 119-129 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The aquiferous system of representatives of the orders Dictyocer-atida, Dendroceratida, and Verongida has been studied to note its relevance to the systematics of the groups. The volume of the choanocyte chamber, the size and shape of the choanocytes, the number of choanocytes per chamber, the relative development of the mesohyl, and the features of endopinacocytes are estimated from scanning and transmission electron microscopic observations of representatives of most families of the three orders. Although the Dysideidae have a reticulate skeleton and were classified in the order Dictyoceratida, they are actually closer to the Aplysillidae (Dendroceratida) than to dictyoceratids. The anatomy and cytology of the Halisarcidae differ profoundly from those of these three orders and are clearly more closely related to nonkeratose sponges. Some changes in classification lead to a pattern with highly homogeneous orders that clearly differ in their anatomic and cytologic features, which does not support the hypothesis of a common origin of the “keratose” sponges.
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  • 145
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    Journal of Morphology 201 (1989), S. 161-178 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The wall of the asymmetrical saclike lungs of the fishes Polypterus and Erpetoichthys consists of several functionally different tissue layers. Their lumen is lined by a surface epithelium composed of (1) highly attenuated cells, termed pneumocytes I; (2) pneumocytes II with lamellar bodies, presumably indicating surfactant production; (3) mucous cells; and (4) ciliated cells. Underlying the pneumocytes I is a dense capillary net. The thin continuous endothelium of this net, together with the pneumocytes I, constitute the very thin blood-air barrier. The basement membrane of epithelium and endothelium fuse in the area of the blood-air barrier (thickness 210 m̈m). Secretory and ciliary cells form longitudinal rows in the epithelium. Below the zone with a gas-exchanging tissue, a layer of connective tissue containing collagen and special elastic fibers occurs. The blood vessels that give rise to or drain the superficial capillary plexus are located in this connective tissue. The outermost layer of the lung consists of muscle cells, a narrow inner zone with smooth muscle cells, and an outer, broader zone with cross-striated muscle cells. The lung is innervated by myelinated and nonmyelinated nerve fibers. The morphology of the gas-exchange tissue in the lungs of these primitive bony fish is fundamentally very similar to that of the lungs of tetrapod vertebrates. The morphologic observations are in close agreement with physiologic data, disclosing well-developed respiratory capacities. Structural simplicity can be regarded as a model from which the lungs of the higher vertebrates derived. In addition to respiratory function, the lungs seem also to have hydrostatic tasks.
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  • 146
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    Journal of Morphology 201 (1989), S. 179-186 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Effect of turning of the egg during incubation on development of the area vasculosa of the chick embryo was investigated. The size of the area vasculosa was determined by two methods: direct measurement with calipers and measurement of a template cut from the eggshell by use of an automatic surface area recorder. The effects of turning and additionally the effects of lowered temperature (36°C) on both growth of the area vasculosa by day 7 and embryo growth by day 14 of incubation were investigated. The effects of turning during a critical period for turning, from 3 to 7 days of incubation, were also recorded. Generally, failure to turn eggs retarded growth of the area vasculosa. Turning during the critical period stimulated the extent of growth of the area vasculosa by day 7 of incubation and of subsequent embryonic growth by day 14. Incubation at low temperature resulted both in reduced expansion of the area vasculosa and retarded embryonic growth in a pattern similar to that observed for unturned eggs. It is suggested that turning stimulates development of blood vessels in the area vasculosa via localized increases in blood pressure. The effect of a reduced area vasculosa is considered to retard embryonic development through restricted nutrient uptake from the yolk. The prevailing hypothesis that turning prevents deleterious membrane adhesions is questioned in light of these observations. It is suggested that the physiological basis for the need for turning lies in maximizing the growth rate of the area vasculosa to maximize yolk use and embryonic growth rate.
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  • 147
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    Journal of Morphology 200 (1989), S. 123-130 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Recessive mutant gene c in axolotls results in a failure of the heart to function because of abnormal embryonic induction processes. The myocardium in this mutant lacks organized sarcomeric myofibrils. The present study was undertaken to determine if developmental abnormalities were evident in other areas of the heart besides the myocardium. A detailed comparative survey of the structure of developing normal and mutant hearts, including the endocardium, its cellular derivatives, and the extracellular matrix, known as cardiac jelly, showed that in the mutant there are fewer than the normal number of endocardial cells lining the heart lumen, the number of mesenchyme cells is reduced, and the cardiac jelly area is greatly enlarged in the posterior part of the truncus adjacent to the ventricle.
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  • 148
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    Journal of Morphology 200 (1989), S. 163-174 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Plethodontid salamanders have unique nasolabial grooves that may function as “capillary tubes” to convey chemicals to the vomeronasal organ when these animals nose-tap. 3H-proline was placed at the base of these grooves in Plethodon cinereus, and autoradiography revealed large concentrations of radioactive material in the vomeronasal organs. There was no significant accumulation of radioactive material in the main olfactory epithelium. Salamanders with blocked nasolabial grooves lacked significant accumulation of material in their nasolabial grooves or vomeronasal epithelia, although some salamanders had radioactive material in the posterior portion of their vomeronasal organ that had entered through the internal nares. Anteriorly placed vomeronasal organs situated adjacent to the posterior limits of the nasolabial grooves may insure that nose-tapping primarily stimulates the vomeronasal sensory epithelium.
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  • 149
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    Journal of Morphology 200 (1989) 
    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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  • 150
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    Journal of Morphology 200 (1989), S. 231-245 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A new mechanical model for function of the pharyngeal jaw apparatus in generalized perciform fishes is developed from work with the family Haemulidae. The model is based on anatomical observations, patterns of muscle activity during feeding (electromyography), and the actions of directly stimulated muscles. The primary working stroke of the pharyngeal apparatus involves simultaneous upper jaw depression and retraction against a stabilized and elevating lower jaw. The working stroke is characterized by overlapping activity in most branchial muscles and is resolved into three phases. Four muscles (obliquus dorsalis 3, levator posterior, levator externus 3/4, and obliquus posterior) that act to depress the upper jaws become active in the first phase. Next, the retractor dorsalis, the only upper jaw retracting muscle, becomes active. Finally, there is activity in several muscles (transversus ventrales, pharyngocleithralis externus, pharyngohyoideus, and protractor pectoralis) that attach to the lower jaws. The combined effect of these muscles is to elevate and stabilize the lower jaws against the depressing and retracting upper jaws.The model identifies a novel mechanism of upper jaw depression, here proposed to be the primary component of the perciform pharyngeal jaw bite. The key to this mechanism is the joint between the epibranchial and toothed pharyngobranchial of arches 3 and 4. Dorsal rotation of epibranchials 3 and 4 about the insertion of the obliquus posterior depresses the lateral border of pharyngobranchials 3 and 4 (upper jaw). The obliquus dorsalis 3 muscle crosses the epibranchial-pharyngo-branchial joint in arches 3 and 4, and several additional muscles effect epibranchial rotation. Five upper jaw muscles cause upper jaw depression upon electrical stimulation: the obliquus dorsalis 3, levator posterior, levator externus 3/4, obliquus posterior, and transversus dorsalis. This result directly contradicts previous interpretations of function for the first three muscles. The presence of strong depression of the upper pharyngeal jaws explains the ability of many generalized perciform fishes to crush hard prey in their pharyngeal apparatus.
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  • 151
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    Journal of Morphology 200 (1989), S. 255-267 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Changes in body morphology during growth and reproduction in the hydromedusa Eleutheria dichotoma are described in terms of variations in eight different characters: umbrella diameter, total surface area, tentacle area, umbrella area, tentacle knob diameter, number of embryos, and diameter and area of buds. Sexually (sex) and vegetatively (veg) reproducing medusae differ significantly in their body morphometrics. Statistically significant allometric relations exist between umbrella diameter and (1) central area (sex and veg); (2) tentacle area (veg); (3) total area (veg); (4) tentacle knob diameter (veg); (5) bud diameter; and (6) number of embryos. A significant correlation between umbrella diameter and area is also found in undetached buds. During sexual reproduction, umbrella area shows positive allometry and loses its correlations to total area, tentacle area, and tentacle knob diameter. Linear and nonlinear bivariate allometric coefficients allow estimation of total body size from only one or two easily measurable attributes, e.g., umbrella and tentacle knob diameter. Curve fitting by the classic allometric equation (y = bxc) is only negligibly worse than that obtained with a “full” equation (y = a + c), and statistical confidence is better.Chemical analyses for carbon and nitrogen content allow estimation of biomass from the projection area of the body surface. The relation factors are 1.06 μgC mm-2 (sex) and 1.14 μgC mm-2 (veg) for carbon and 0.293 μgN mm-2 (sex) and 0.287 μgN mm-2 (veg) for nitrogen. The C:N ratios are 3.6 and 4.0 for sexual and vegetative medusae, respectively. The use of allometric regression formulas to calculate surface areas and to relate these to carbon content provides quick estimations of body size in a microscopic animal.
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  • 152
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    Journal of Morphology 202 (1989), S. 13-28 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The neuronal organization of the accessory olfactory bulb (AOB), which receives sensory information from the vomeronasal organ, was described in a squamate reptile (Podarcis hispanica) by means of light microscopy. Using the Golgi-impregnation method, seven neuronal types could be distinguished:Periglomerular cells constitute a morphologically heterogeneous population of small neurons located between and around the glomeruli.The mitral cells are diffusely distributed in the AOB. Their cell bodies are usually located within the mitral cell layer, but some of them could be also observed in the plexiform layers. Mitral cells were classified into three subgroups on the basis of their sizes and dendritic tree morphologies. Thus, the “outer mitral cells” have the biggest cell bodies, and their distal secondary dendrites are mainly distributed rostrocaudally in the external plexiform layer. The “inner mitral cells” have large cell bodies, and their secondary dendrites are distributed dorsoventrally and are located deeper than those of the other two subgroups. The third type, the “small mitral cells,” is the smallest one among mitral cells in the AOB, and from their cell bodies, only two main dendritic trunks arise.The granule cells are composed of several categories based on their different cell body locations and dendritic tree morphologies. Thus, the “superficial granule cells” are located exclusively in the external plexiform layer and have small dendritic fields. The “middle granule cells” have fusiform cell bodies - situated in the internal plexiform layer - and present a wide dendritic projection area. Finally, the “deep granule cells” are distributed throughout the granule cell layer and include a great variety of dendritic tree morphologies.The distribution and morphological features of all neuronal types constituting the AOB of Podarcis were compared with those reported on other vertebrates. The results suggest that the lamination pattern and neuronal organization of the AOB in lizards are more similar to that of mammals than to that of the remaining vertebrates.
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  • 153
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    Journal of Morphology 202 (1989), S. 69-88 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Iridescent butterfly scales are structurally colored, relying upon the interaction of light with detailed architecture to produce their color. In some iridescent scales, the reflective elements are contained within the body of the scale and come in two basic forms, lattices that produce diffraction colors (analogous to those produced by opal), and stacks of laminae that produce thin-film interference colors (analogous to those produced by soap or oil films). Both structures are remarkably complex and precise, yet each is only part of the total edifice built by the cell that makes the scale.To understand better how a cell can produce lattices or thin-film laminae, I studied the development of iridescent scales from two lycaenid butterflies. The presence of diffraction and thin-film scales in the same family (and in some cases on the same individual) suggests that the two types must be developmentally related; yet these results yield no clear explanation as to how. The diffraction lattice appears to be shaped within the boundaries of the scale cell by means of a convoluted series of membranes in which the smooth endoplasmic reticulum plays an important part. The thin-film interference laminae appear to result from the condensation of a network of filaments and tubes secreted outside the boundaries of the cell. This paper outlines the developmental histories of both types of scale and discusses the developmental implications of the mechanisms by which they form.
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  • 154
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Wing folding spicules, elytral binding patches, and elytral locking devices of adult male and female seed weevils, Smicronyx fulvus LeConte and S. sordidus LeConte, involved in stridulation are described. Sound is produced by both sexes of the two species when the plectrum, paired conical teeth located along the anterior margin of the dorsally elevated seventh sternite, is struck against an elongate file, the pars stridens, on the under surface of the apical portion of each elytron. A second plectrum, on the sixth tergite, is well-developed in males of both species and is used by males to produce sound before and during mating.Sex-specific and species-specific differences in the sound produced is attributed to structural variation in the pars stridens and the elytra. The pars stridens determines frequencies, while the elytra may further modify the sound. The frequency range for male S. fulvus is 1,000 cycles per second (cps) through 13,000 cps and for male S. sordidus is 2,500 cps through 13,000 cps. The frequency range for female S. fulvus is 2,000 cps through 11,500 cps and for female S. sordidus is 900 cps through 11,500 cps.
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  • 155
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    Journal of Morphology 202 (1989), S. 53-68 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A study of neuromast ontogeny and lateral line canal formation in Oreochromis aureus and Cichlasoma nigrofasciatum reveals the existence of two classes of neuromasts: those that arise just before hatching (presumptive canal neuromasts, dorsal superficial neuromasts, gap neuromasts, and caudal fin neuromasts) and pairs of neuromasts that arise on each lateral line scale lateral to each canal segment at the same time as canal formation. In the anterior trunk canal segment, each presumptive canal neuromast is accompanied by a dorsoventrally oriented superficial neuromast forming an orthogonal neuromast pair. It is suggested that each of these dorsoventrally oriented superficial neuromasts is homologous to the transverse superficial neuromast row described by Münz (Zoomorphology 93:73-86, '79) in other cichlids. It is further suggested that the longitudinal lines described by Münz (Zoomorphology 93:73-86, '79) are derived from the pair of superficial neuromasts that arise during canal formation. Distinct changes in neuromast topography are documented. Neuromast formation, scale formation, and lateral line canal formation are three distinct and sequential processes. The distribution of neuromasts is correlated with myomere configuration; there is always one presumptive canal neuromast on each myomere. A single scale forms beneath each presumptive canal neuromast. Canal segment formation is initiated with the enclosure of each presumptive canal neuromast by an epithelial bridge which later ossifies. The distinction of these three processes raises questions as to the causal relationships among them.
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  • 156
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    Journal of Morphology 199 (1989), S. 299-311 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Gonadal differentiation in premetamorphic Bombina orientalis is described and staged. The pattern of events during differentiation in Bombina differs in several respects from that previously described in other anurans. The Bombina gonad initially develops on the ventral surface of the vena cava, where there is no pre-existent somatic genital ridge prior to the arrival of the germ cells. The sexually undifferentiated gonad does not have a distinct cortex and medulla; instead, medullary cells ingress from the mesonephric blastema during sexual differentiation. Formation of a testis or an ovary appears to depend on the ability (or lack of ability) of the medulla to invade the germ cell-containing cortex. In the germ line, sexual differetiation can be recognized by a premeiotic increase in oogonial cell volume.
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  • 157
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    Polymer Engineering and Science 29 (1989), S. 1569-1573 
    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 gel melting temperature and crystallization kinetics of ultra-high molecular weight polyethylene (UHMW-PE)/decalin systems were investigated. Two methods were used to determine gel melting temperature; thermomechanical analysis (TMA) with a penetration probe and differential scanning calorimetry (DSC). The melting points determined from TMA and DSC were in good agreement, indicating that the crystallization of UHME-PE is an essential step for gelation. The gel melting temperature increases with UHMW-PE concentration. The change in gel melting temperature with composition results from interaction of the components in the amorphous phase. The gelation and crystallization rates increase with decreasing UHMW-PE concentration.
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  • 158
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    Polymer Engineering and Science 29 (1989), S. 1553-1559 
    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 cure of an epoxy-anhydride resin system used in pultrusion was characterized to develop an understanding of the cure behavior and to determine potential process controls parameters. Isothermal cures of neat resin formulations were monitored by differential scanning calorimetry (DSC), torsional braid analysis (TBA), and microdielectrometry (MDE). The processing conditions define a time/ temperature region in which monitoring would be applicable. Both DSC and MDE were found to yield useful information in this region, however, the events typically monitored by TBA either did not occur or occurred too quickly to be monitored. Significant ionic conductivity was observed in the fully cured resins at temperatures above the glass transition temperature and could possibly be used as a control parameter. This study revealed an apparent change in reaction mechanism with increasing cure temperature. DSC showed a change in activation energy with extent of reaction and a decrease in heat of reaction at the higher isothermal cure temperatures. The formation of a different network structure was indicated by a decreasing glass transition temperature of the cured resin with increasing cure temperature by both DSC and TBA.
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  • 159
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    Polymer Engineering and Science 29 (1989), S. 1604-1610 
    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 investigation of the effect of physical aging on excess enthalpy of compatible polymer blends was carried out. Poly(methyl methacrylate) (PMMA) and poly(styrene-co-acrylonitrile) (SAN) were chosen for this study. Blends of different ratios of PMMA and SAN were physically aged at different times and temperatures below their glass transition (Tg) and then subjected to enthalpy relaxation measurement in a differential scanning calorimeter (DSC). An improved procedure was developed and, employed to analyze the data. The error associated with the calculation of the normalized deviation in enthalpy, known as the “Φ” function, was below 4%. The relaxation was observed to proceed faster at higher aging temperature. It was also found that at higher aging temperatures of Tg - 20 and Tg- 35°C, enthalpy relaxation in SAN-rich blends proceeds faster than in PMMA rich blends, while at the low aging temperature of Tg- 50°C the rate of relaxation becomes independent of the composition.
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  • 160
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    Polymer Engineering and Science 29 (1989), S. 1638-1641 
    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: Die-drawing techniques recently developed at Leeds University make it possible to produce oriented polymer tubes with both axial draw and hoopwise expansion. These products have increased axial stiffness, improved barrier properties, and excellent resistance to chemical reagents. Normally mechanical methods are used to join such tubes in order to preserve their orientation: however we show that electrofusion techniques produce joints of strengths such that in tensile tests, failure always occurs in the fittings, not at the joint interfaces. Optical and electron microscopy reveal different zones in the welds and indicate that only 20 percent of the wall thickness is affected by the electrofusion process. The pipe studied was biaxially drawn medium density polyethylene of outside diameter 63 mm with draw ratios of 4 in the axial direction and 2, inner hoop. Optimum welding conditions were determined using socket and saddle electrofusion fittings. The joints did not fail in a standard crush test. Careful control of welding parameters is essential in butt fusion welding when the maximum weld strength exceeds that of the undrawn polymer.
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  • 161
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The lungs of the New Caldeonian gecko Rhacodactylus leachianus were examined by means of gross dissection and light and electron microscopy. This tropical species, which is the largest living gecko, possesses two simple, single-chambered lungs. Right and left lungs are of similar size and shape. The lung volume (27.2 ml · 100 g-1) is similar to that of the tokay (Gekko gecko) but differs in that the gas exchange tissue is approximately homogeneously distributed, and the parenchymal units (ediculae) are very large, ∼2 mm in diameter. The parenchymal depth varies according to the location in the lung, being deepest near the middle of the lung and shallowest caudally. Scanning and transmission electron microscopy reveal an unusual distribution of ciliated cells in patches on the edicular walls as well as on the trabeculae. Secretory cell are very numerous, particularly in the bronchial epithelium, where they greatly outnumber the ciliated cells. The secretory cells form a morphological continuum characterized by small secretory droplets apically and large vacuoles basally. This continuum includes cells resembling type II pneumocytes but which are devoid of lamellar bodies. Type I pneumocytes similar to those of other reptiles cover the respiratory capillaries, where they form a thin, air-blood barrier together with the capillary endothelial cells and the fused basement laminae. The innervation, musculature, and vascular distribution in R. leachianus are also characterized. Apparent simplification of the lungs in this taxon may be related to features of its sluggish habits, whereas peculiarities of cell tissue composition may reflect demands of its mesic habitat.
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  • 162
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    Journal of Morphology 199 (1989) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 163
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    Journal of Morphology 199 (1989) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
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  • 164
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    Journal of Morphology 199 (1989), S. 41-52 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The molting cycle of Artemia is described and subdivided in stages A-D3 according to the system of Drach. Determination of the stages is done in living animals by light microscopic observation of changes in the texture of the setal matrix of the exopodites. A parallel ultrastructural investigation of the integument was carried out to control the proposed staging scheme. The duration of each stage was calculated.
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  • 165
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    Journal of Morphology 199 (1989), S. 71-92 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The extracellular matrix surrounding the sea urchin embryo (outer ECM) contains fibers and granules of various sizes which are organized in recognizable patterns as shown by ultrastructural studies, particularly stereoimaging techniques. The use of the ruthenium red method for retaining and staining the ECM, with modification of the Luft (Anatomical Record 171:347-368, 1971) method for invertebrate embryos, allows for the clarification of certain structures, particularly fiber compaction in the interzonal region, and microvillus-associated bodies.The inner ECM in the sea urchin embryo includes the basal lamina and blastocoel matrix. Stereoimages show that the fibers which are loosely distributed in the blastocoel matrix become compacted around the periphery of the blastocoel to form the basal lamina.The ruthenium red method was also used on a number of marine invertebrate embryos and larvae, representing different phyla, to facilitate comparisons between their surface coats. The similarities observed in the specimens shown suggest that ECMs are widely found on marine invertebrate eggs, embryos, and larvae, and that they resemble vertebrate ECMs and may, therefore, have similar functions.
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  • 166
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    Journal of Morphology 199 (1989), S. 151-164 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The coronate larva of the ascophoran bryozoan Watersipora arcuata has a ring of 32 large, multiciliated coronal cells that are used for swimming. Fourteen pairs of small cells are intercalated between the lateral margins of adjacent coronal cells. These intercoronal cells are arranged in a precise pattern and are polymorphic: seven pairs have multiple cilia and seven pairs are mono- or oligociliated. Three pairs of multiciliated intercoronal cells have their cilia arranged as a whorl that is recessed in a pocket formed between the adjacent coronal cells, and they are thought to be photoreceptors that sense general light intensity. Two other pairs of multiciliated cells with cohesive tufts of cilia may be chemo- or mechanoreceptors. Roles of the other intercoronal cells in this species are not evident, but it is proposed that the majority, if not all, of them are sensory. The close proximity of all the intercoronal cells to the equatorial nerve ring is compatible with this interpretation. Analyses of the literature on cleavage patterns, pigment cup ocelli, and flagellar tufts that serve as balancers in coronate larvae lead us to propose that (1) an intercoronal cell is the sensory element of most, if not all, pigment cup ocelli of bryozoan larvae; and (2) intercoronal cells are not modified coronal cells but probably are specialized supra- and/or infracoronal ones that have migrated to an intercoronal position.
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  • 167
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    Journal of Morphology 199 (1989), S. 245-247 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 168
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    Journal of Morphology 199 (1989), S. 223-243 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The projectile tongue of caudate amphibians has been studied from many perspectives, yet a quantitative kinetic model of tongue function has not yet been presented for generalized (nonplethodontid) terrestrial salamanders. The purposes of this paper are to describe quantitatively the kinnematics of the feeding mechanism and to present a kinetic model for the function of the tongue in the ambystomatid salamander Ambystoma tigrinum. Six kinematic variables were quantified from high-speed films of adult A. tigrinum feeding on land and in the water. Tongue protrusion reaches its maximum during peak gape, while peak tongue height is reached earlier, 15 ms after the mouth starts to open. Tongue kinematics change considerably during feeding in the water, and the tongue is not protruded past the plane of the gape. Electrical stimulation of the major tongue muscles showed that tongue projection in A. tigrinum is the combined result of activity in four muscles: the geniohyoideus, Subarcualis rectus 1, intermandibularis posterior, and interhyoideus. Stimulation of the Subarcualis rectus 1 alone does not cause tongue projection. The kinetic model produced from the kinematic and stimulation data involves both a dorsal vector (the resultant of the Subarcualis rectus 1, intermandibularis posterior, and interhyoideus) and a ventral vector (the geniohyoideus muscle), which sum to produce a resultant anterior vector that directs tongue motion out of the mouth and toward the prey. This model generates numerous testable predictions about tongue function and provides a mechanistic basis for the hypothesis that tongue projection in salamanders evolved from primitive intraoral manipulative action of the hyobranchial apparatus.
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  • 169
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have attempted to develop an objective, semiquantitative classification of fiber types in turtle neck and limb muscle using microphotometry and multivariate statistical techniques. We first stained serial sections for myosin adenosine triphosphatase (ATPase) (with acid and alkaline preincubation and without preincubation), NADH-diaphorase, and two glycolysis-associated markers, α-glycerophosphate dehydrogenase (α-GPDH) and glycogen phosphorylase A (GPA). This allowed us to characterize individual muscle fibers in terms of their contraction speed and metabolic properties. Next we used microphotometry to measure the optical density of the reaction product in each fiber, and we subjected the resulting optical density matrix to cluster and discriminant function analyses in order to assign fibers to groups (fiber types) and to determine which stains contribute most to the distinction between groups. As a control, we processed a well characterized mammalian muscle (rat sternomastoid) simultaneously. Our results suggest that both neck and limb muscle in Pseudemys can best described as falling into three groups: (1) slow oxidative (SO) fibers; (2) fast oxidative glycolytic (FOG) fibers, with relatively high oxidative and glycolytic capacities; and (3) fast glycolytic (Fg) fibers, with low oxidative, low/intermediate α-GPDH, and high GPA activities. These three fiber types differ from like-named types in rat muscle both in the pH lability of their myosins and in their metabolic profiles.
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  • 170
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    Journal of Morphology 200 (1989) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
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  • 171
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    Journal of Morphology 200 (1989), S. 1-8 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Distribution and density of the chloride cells in the newly hatched larvae of teleosts vary depending on species and environmental salinity at hatching. In the euryhaline freshwater ayu (Plecoglossus altivelis), chloride cells are concentrated in the skin posterior to the pectoral fins and gradually decrease in number toward the head and tail. In the stenohaline sea water flounder (Kareius bicoloratus), most chloride cells are localized at the inner membrane of gill chambers and in the skin near the openings of gill chambers, but only a few cells appear in the skin of the yolk sac. In the stenohaline freshwater carp (Cyprinus carpio), only a few small chloride cells are scattered in the body skin. The density and abundance of chloride cells appears to be correlated with the different requirements for osmoregulation in teleost larvae.
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  • 172
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This investigation relates the occlusal morphology of the continuously growing molars of common wombats (Vombatus ursinus) to the underlying enamel ultrastructure that was investigated using the techniques of light microscopy, scanning electron microscopy, and transmission electron microscopy. The main feature of the occlusal enamel was a prominent ridge, which followed the contour of the dentine-enamel junction (DEJ). It was found that the occlusal morphology depended upon the orientation of the dentinal and enamel tissues, variations in prism orientation, Hunter-Schreger bands (HSB), and presence or absence of cleavage. Cleavage of enamel promoted by sheets of parallel prisms occurred along the face between the DEJ and the ridge, whereas on the face between the ridge and the cementum-enamel junction (CEJ) cleavage was inhibited by HSB. The slope of the latter face was mainly due to a decrease in wear resistance going from the ridge, where prisms were intercepted transversely, toward the CEJ, where they were intercepted obliquely. Occasionally small surface undulations were observed on the face between the ridge and the CEJ. These undulations were found to correspond to gradually decussating enamel regions. The pronounced cleavage of enamel parallel to the face between the DEJ and the ridge played an important role in conferring on the continuously growing molars a distinct property to develop and maintain a self-sharpening ridge throughout the life of the tooth.
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  • 173
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    Journal of Morphology 200 (1989), S. 215-230 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The internal anatomy of juveniles and adults of Hypochthonius rufulus selected as a model species representing the lower Oribatida was investigated histologically and compared with the published characteristics of higher oribatid internal anatomy. In this species, the cuticle is weak and flexible, consisting of epicuticle and endocuticle on the body, but including an exocuticle between the epicuticle and endocuticle of the legs. Walls of the mesenteron in the digestive tract are of uniform thickness and structure without any regional thickening, and there are no proventricular glands. The hindgut is apparently divided into five parts: colon 1 and 2, rectum 1 and 2, and anal atrium; food bolus exhibits a multilamellar structure in this section. The glandular system is less diversified than in some other oribatids. Tracheae are apparently lacking. Females possess only two relatively large eggs, filling one-half of opistosoma, and they lack ovipositors. Eggs are present in females during the whole year. Gonad buds appear first in the protonymph stage. Only one male was found among 146 adults studied. No male external organ (aedeagus or penis) is present.
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  • 174
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    Journal of Morphology 200 (1989), S. 199-213 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have investigated the structural organization of the wind-sensitive giant interneurons in the thoracic ganglia of adult American cockroaches. These seven bilaterally paired interneurons have long been thought to play a role in directing the wind-elicited escape response of the animal. Each of the giant interneurons was labeled individually by intracellular injection of cobaltic hexamine chloride. An individual giant interneuron could be reliably identified from animal to animal based on its branching pattern in thoracic ganglia. The axons of the giant interneurons are situated on each side of the nerve cord in two recognizable subgroups. Comparisons of the axonal arbors of the dorsal and ventral subgroups showed that they project into distinct but partly overlapping regions of thoracic ganglia. Three of the giant interneurons were found to have axonal arbors that cross the longitudinal midline of thoracic and abdominal ganglia. Bilateral pairs of these giant interneurons were labeled concomitantly, and many of the individual neurites from these cells appeared to be closely apposed. All these morphological characteristics are discussed in relation to the connectivity and functional significance of the giant interneurons.
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  • 175
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    Journal of Morphology 200 (1989), S. 247-253 
    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 adductor muscle of the boring clam (Tridacna crocea) was investigated. The adductor was composed of opaque and translucent portions. The opaque portion contained smooth muscle cells; the translucent portion contained obliquely striated cells. Smooth muscle cells were classified, according to the statistically analyzed diameters of their thick myofilaments, into two types, S-1 and S-2. S-1 cells had thick myofilaments, 50-60 nm in diameter. S-2 cells had thick myofilaments of two sizes, about 55-65 nm and 85-100 nm in diameter, respectively. Obliquely striated muscle cells in the translucent portion were also classified into two types: O-1 cells, with thick myofilaments 30-35 nm in diameter, and O-2 cells, with myofilaments of 50-60 nm.
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  • 176
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    Journal of Morphology 201 (1989) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 177
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    Journal of Morphology 201 (1989), S. 23-37 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Sensory and motor innervation of the proboscis by branches of the maxillary and labial nerves of the worker honey bee has been investigated in specimens stained vitally by methylene blue or viewed by scanning electron microscopy. A chordotonal organ consisting of a single scolopidium is present in the maxillary palp. Flexion of the maxillary palp occurs only passively, induced by the flexion of the galea. This chordotonal organ may function as a proprioceptor for the movement of the galea. Another chordotonal organ exists in the prementum of the labium. It contains, on the average, 12 sensory cells and presumably responds to the bending of the labial palp. A nerve-net of bipolar cells arises from the sensory branches of the maxillary nerve. Free nerve endings derived from the periphery of this nerve-net expand broadly on the intersegmental membranes connected to the stipes. The right and left nerves to the dilator muscles of the salivarium exchange branches, resulting in the reciprocal innervation of each muscle.
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  • 178
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    Journal of Morphology 201 (1989), S. 59-68 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The tectorial structures of the inner ear of the proteid salamander Proteus anguinus were studied with transmission and scanning electron microscopy in order to analyze the ultrastructure of the otoconial membranes and otoconial masses of the maculae and the tectorial membrane of the papilla amphibiorum. Both otoconial and tectorial membranes consist of two parts: (1) a compact part and (2) a fibrillar part that joins the membrane with the sensory epithelium. Masses of otoconia occupy the lumina above these membranes.There are two types of calcium carbonate crystals in the otoconial masses within the inner ear of Proteus anguinus. The relatively small otoconial mass of the utricular macula occupies an area no greater than the diameter of the sensory epithelium, and it is composed of calcite crystals. On the other hand, the enormous otoconial masses of the saccular macula and the lagenar macula are composed of aragonite crystals. In the sacculus and lagena, globular structures 2-9 m̈m in diameter were discovered on the lower surfaces of the otoconial masses above the sensory epithelia. These globules show a progression from smooth-surfaced, small globules to large globules with spongelike, rough surfaces. It is hypothesized that these globules are precursors of the aragonite crystals and that calcite crystals develop similarly in the utriculus. The presence of globular precursors in adult animals suggests that the formation of new crystals in the otoconial membranes of the sacculus and lagena of Proteus is a continuous, ongoing process.
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  • 179
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    Journal of Morphology 201 (1989) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 180
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: When homozygous, recessive mutant gene c in Ambystoma mexicanum results in a failure of embryonic heart function. This failure is apparently due to abnormal inductive influences from the anterior endoderm resulting in an absence of normal sarcomeric myofibril formation. Biochemical and immunofluorescent studies were undertaken to evaluate the contractile proteins actin and tropomyosin in normal and mutant hearts. For the immunofluorescent studies, cardiac tissues were fixed in periodate-lysine-paraformaldehyde, frozen sectioned, and immunostained by an indirect method with monospecific polyclonal antibodies produced against highly purified chicken heart actin and tropomyosin. In normal hearts, both antiactin and antitropomyosin stained the myofibrillar I-bands intensely. In mutant hearts, intensity of staining with antiactin antibody was similar to normal, although sarcomeric patterns were not observed. Staining intensity for tropomyosin with antitropomyosin antibody was significantly reduced in mutant hearts when compared to normal. Biochemical studies were used to evaluate antibody specificity, antigenic variability, and relative protein concentrations of actin and tropomyosin in normal and mutant cardiac tissues. Tissue homogenates were electrophoresed in two dimensions, and second-dimension slab gels were either Coomassie Blue silver-stained or transblotted onto nitrocellulose and the proteins stained with antibodies. Stained gels and immunoblots of cardiac proteins reveal that the amounts of actin isoforms are identical in normal and mutant hearts. However, these methods demonstrate a significantly reduced amount of tropomyosin in mutant tissue. This confirms earlier studies suggesting reduced amounts of tropomyosin in mutant hearts based upon immunological assays. Thus, failure of normal myofibrillogenesis in gene c mutant hearts does not appear to result from a change in actin isoform composition but may be related to a deficiency in tropomyosin.
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  • 181
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    Journal of Morphology 202 (1989) 
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  • 182
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Knee joints from adult, juvenile, hatchling, and embryonic (full term) American alligators were dissected to reveal the cruciate ligaments and the medial and lateral menisci. Two anterior cruciate (major and minor), a posterior cruciate, an intermeniscal, and a meniscofemoral ligament were identified. In addition, we found a fourth internal ligament which has not been reported previously. Menisci and ligaments from left knees were fixed in formalin and processed for routine histological observation. Those from right knees were stained in bulk by using a gold chloride method and were either frozen and sectioned at 100 m̈m on a sliding microtome or were processed for paraffin sections at 30 m̈m. The morphology of the collagenous, cartilaginous, and vascular constituents of the tissues was similar to that of the dog, cat, and human. Nerve fibers were observed in all tissues sampled. Structures resembling Golgi tendon organs and Pacinian corpuscles were identified, reinforcing the theory that neural elements within cruciate ligaments and menisci may provide afferent input that affects the function of the knee joint.
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  • 183
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    Journal of Morphology 202 (1989), S. 205-223 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ultrastructural changes occurring in the adenohypophysis (AH) of the anadromous sea lamprey, Petromyzon marinus, during metamorphosis (stages one through seven) were examined. The rostral pars distalis initially contains one granulated (secretory) cell type A and one nongranulated type I cell. A second granulated cell (type B) appears during the later stages (stages six and seven) of metamorphosis. The most pronounced ultrastructural changes take place in the caudal pars distalis (CPD). Initially, most cells (80-90%) are nongranulated cells type II and some type I. Granulated type C and D cells form the remainder of the CPD. Almost all cells during stages three and four demonstrate a marked increase in synthetic activity evident by conspicuous Golgi regions, abundant rough endoplasmic reticulum (RER), and increased cell volume. Most cells are sparsely granulated. Secretory cell types C and D and, two new cell types, E and F, are present. Synthetic activity subsides by stage five. Most cells (80-90%) during stages five through seven are granulated. Type E are most prevalent with variable numbers of types C and D and few type F. Nongranulated cells now represent only 10-20% of the CPD. The increase in granulated cells occurs at the expense of type II cells that differentiate into granulated cell types. The fine structure of the pars intermedia throughout metamorphosis remains similar to that of the larva. Most cells are granulated, highly vesiculated type G cells. A few nongranulated type I cells are also present. The functional significance of the secretory cells in the AH is related to the requirement for an intact pituitary gland for the initiation and completion of metamorphosis.
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  • 184
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  • 185
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    Journal of Morphology 202 (1989), S. 255-269 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The gastrodermis of the black coral Antipathes aperta is associated with eight distinct types of cells, including two types of microbasic b-mastigophores (nematocysts), spumous and vesicular mucus cells, and ganglion cells that are essentially the same as in the epidermis. Three additional types of cells are unique to the gastrodermis, and are readily distinguished from those of the epidermis by their electron-opaque inclusions. These include lipoidal cells, zymogen digestive cells, and an unusual type of epitheliomuscular collar cell. The pharyngeal region is characterized by the presence of electron-opaque nematocysts, a scattering of zymogen cells, and a large number of collar cells. The latter are distinguished in part by the presence of dense microfibrillar processes that surround the microvilli and extend into adjacent collars. This interconnection results in the formation of an extensive pharyngeal meshwork. These collar cells are additionally distinguished by the placement of the collar and flagellum adjacent to a flared cup of cytoplasm. This portion of the cell is capable of endocytosis of relatively large unicellular prey, and apparently is capable of forming digestive vesicles as well. The pharyngeal gastrodermis grades into simple lobate septal filaments toward the base of the coelenteron, where large, granular nematocysts all but replace the smaller electron-opaque types Collar cells are found here as well, but in fewer numbers compared to the zymogen cells. Ultrastructural results are compared with those of other coelenterates and discussed in terms of food and modes of nutrition.
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  • 186
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: In Holland, bugs of the species Hebrus pusillus and H. ruficeps have one generation per year and overwinter as unmated adults. Males have two testes with two follicles + vasa efferentia each, paired vasa deferentia and seminal vesicles, an ejaculatory duct, and a protrusible phallus comprising an articulatory apparatus, phallotheca, endosoma, and paired claspers. The skeletomusculature of this system is described (it has 12 paired and four unpaired muscles) and its functions in generating and transferring sperm (summarized in Figs. 70-75) are reconstructed from study of living bugs, dissections, whole mounts, and serial sections.Males of both species produce sperm 〉2 mm long from stem spermatogonia in the germarium of each follicle. Initial definitive spermatogonia divide synchronously three times to form clones of eight, interconnected, primary spermatocytes. These enlarge up to 43-fold in males of H. pusillus and 78-fold in those of H. ruficeps, undergo meiosis, and, after adult emergence, complete their differentiation into bundles of 32 sperm which coil transversely about the periphery of each follicle at its base. These begin to enter the vasa efferentia in mid August, rupture, and release their sperm into the seminal vesicles where they are stored overwinter. Most spermatocyte and spermatid cysts remaining in the testes degenerate in fall, leaving only stem spermatogonia and a few early spermatocysts in the germaria.Males of H. pusillus begin to mate the first warm days of spring but only the most persistent succeed. A male jumps on the back of a female, induces her to lower her ovipositor, and, within 12 min (@ 18-24°C), introduces the endosoma of his phallus up its shaft and fills his seminal duct with sperm. The female draws this into her gynatrial sac at the end of copulation and transfers it into her spermatheca in about 30 min, the sperm reversing themselves within it so that their heads face towards its mouth. The male may stay on her back for up to 2 hours and may copulate again up to three times before leaving to mate with other females.Males of H. pusillus may be sexually active for months after overwintering, because spermatogonia in their germaria reactivate in spring to produce additional sperm. Those of H. ruficeps do not and males mate successfully only until their supply of overwintered sperm is exhausted.The chromosome complement of H. pusillus males is 2N = 22 + XY. The X and Y chromosomes are of unequal length, form a pseudo pair at metaphase I, and segregate to opposite poles at anaphase I - the first instance of pre-reductional segregation of sex chromosomes to be recorded in the Gerromorpha. The chromosome complement of H. ruficeps may be 2N = 24 + XO but the nature of two chromosomes was not resolved. The single X segregates to half the spermatids at anaphase II.
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  • 187
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    Journal of Morphology 202 (1989), S. 409-424 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The solum nasi of Microcebus murinus is characterized by the presence of a zona annularis, continuity between the anterior transverse lamina and the paraseptal cartilage, a continuous paraseptal cartilage, a palatine cartilage and a posterior transverse lamina. It lacks a fibula reuniens and possibly a cartilage of the nasopalatine duct as well as a palatine papillary cartilage. The morphology in M. murinus closely resembles that seen in Tupaia and Galago. This affinity results from the retention of primitive traits. However, Galago is reported to lack a zona annularis, thus displaying a specialization not shared with M. murinus. Therefore, the zona annularis provides a useful trait for distinguishing between the ontogenies of M. murinus and Galago.
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  • 188
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    Journal of Morphology 202 (1989), S. 435-455 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In each of 30 dipteran species, representing 13 acalyptrate and 7 calyptrate families, the cardia is formed from specialized cells at the junction between foregut and midgut. Foregut epithelium forms the stomodeal valve; midgut epithelium envelops the valve to form the cardia's outer wall. Cytological characteristics within these epithelia differ from region to region and from species to species. Since the cardia secretes the peritrophic membrane, cardias with diverse patterns of cellular differentiation may be expected to produce peritrophic membranes with similarly diverse properties. Close relatives often share more details of cardia structure than do distantly related taxa. Within the monophyletic Calyptratae, a common pattern of cellular differentiation includes three distinct zones of columnar midgut cells enclosing a flanged stomodeal valve. Among species in the paraphyletic Acalyptratae, midgut typically includes a single zone of tall columnar cells, while the valve may be spheroidal, cylindrical, conical, or flanged. The correlation of phylogenetic distance with divergence in cardia organization implies a strong influence of ancestry upon current structure, regardless of current diet. However, at least some of the observed diversity in cardia structure is associated with dietary divergence. Calyptrate flies with derived blood-feeding behavior display cellular differentiation that is simplified from that seen in calyptrate relatives with less specialized feeding habits. This evolutionary modification suggests that cardia organization and hence peritrophic membrane structure can adapt to dietary changes, with possible significance for the spatial organization of digestive processes and interactions with ingested microorganisms.
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  • 189
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    Journal of Morphology 202 (1989), S. 239-253 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The tentacular epidermis of the black coral Antipathes aperta is organized into three distinct regions, containing at least nine different types of cells. The outermost region is dominated by spirocytes along with two types of nematocytes, organized into discrete wart-like batteries. The two nematocyte types both contain microbasic b-mastigophore nematocysts. The outer boundary of the wart is marked by the presence of both spumous and vesicular mucus cells. The ciliation of the wart is contributed principally by the spirocytes. Warts are enveloped and separated from one another by an unusual neurosensory cell complex that extends from the tentacular surface to the mesogleal connective tissue foundation. Funnel-like, flagellated cells composing the complex connect with ganglion cells composing the dominant portion of the nerve net system. Branches of this complex also penetrate the central portion of the wart, making direct contact with the cnidae. The tentacular mid-region is composed of nematocytes and spirocytes in various stages of maturation, along with epitheliomuscular cell (EMC) somata. The EMC's narrow apically extend toward the tentacle surface, forming contacts with the cnidae. The basal end of the EMC expands to form the larger portion of the tentacular musculature. The inner region of tentacular epidermis is marked by a neuromuscular complex sheathed by extensions of mesoglea. The ganglion cells occur as a plexus deep within the tentacle and form polarized junctions with the EMC's, but neuromuscular synapses are not well enough defined for documentation. Polarized synapses lacking well-defined membrane thickenings characterize the interneuronal junctions. Granular cells lining the mesogleal surface appear to be responsible for mesogleal fibrillogenesis.
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  • 190
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    Journal of Morphology 202 (1989), S. 325-338 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The stages of differentiation of the inner ear sensory epithelia of the neotenous cave urodele, Proteus anguinus, was studied with light and electron microscopy. Comparative ultrastructural analysis among specimens of different sizes confirms that new sensory cells may be generated throughout life, particularly along the periphery of the saccular macula. The inner ear of Proteus contains at least four types of sensory cells that differ in their apical ciliary part.The lungs and air-filled buccal cavity may function as transducers of sound pressure in underwater conditions. Sound waves might be transmitted from the buccal cavity to the connected oval window. The very complex orientation of the sensory hair cells of the saccular macula and the large overlying saccular otoconial mass suggest that this macula facilitates orientation of Proteus in its underground aqueous habitat.
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  • 191
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    Journal of Morphology 202 (1989), S. 351-359 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the Uloboridae, web reduction is accompanied by changes in opisthosomal shape, leg length, and web-monitoring tactics. These morphological changes make reduced-web spiders more cryptic and alter their leg leverage and centers of mass. When compared with the orb-weaver Uloborus glomosus, the irregular, reduced-web spider, Miagrammopes animotus, invests more mass in its prosoma and first legs. However, the latter species' elongate opisthosoma posteriorly shifts this region's center of mass, causing the relative position of its composite center of mass and the distribution of weight between its first and fourth legs to be similar to that of the orb-weaver. Like these species, the opisthosomal center of mass of the triangle-weaver, Hyptiotes cavatus, lies near its midpoint. However, the shorter first legs and rounder, heavier opisthosoma of Hyptiotes posteriorly shift its composite center of mass and distribute more of its weight onto its fourth legs. Consequently, the morphology of M. animotus can be adequately explained by its adaptiveness for web manipulation, balance, and weight distribution and the crypsis that these features confer as an ancillary advantage. In contrast, anatomical changes in H. cavatus are better explained as adaptations for web manipulation and crypsis.
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  • 192
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    Journal of Morphology 202 (1989), S. 425-433 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Eosinophilopoiesis in the musk shrew, Suncus murinus, a representative of the order Insectivora, was studied by light and electron microscopy. To examine biochemical features of cytoplasmic granules, extraction with proteolytic enzymes was carried out on ultrathin sections of bone marrow. In this species, eosinophils are produced in the same manner in both spleen and bone marrow. Developing eosinophils were distinguished as belonging to four stages, recognized by ultrastructural changes in cytoplasmic organelles as well as the eosinophilic granules during maturation. Granulogenesis began by budding of vacuoles containing flocculent material from the concave face of the Golgi apparatus, in the promyelocyte to myelocyte stage. The matrix of developing granules transformed into a finely granular structure, and the large spherical granules of mature eosinophils were homogeneous without crystalline cores. It was shown by proteolytic enzyme extraction that the proteinaceous cores of mature granules were uniformly removed; there was no evidence that they contained crystalloid inclusions. These results indicate that shrew eosinophils can be regarded as cells that retain a prototype of eosinophil granules, probably like those of ancestral mammals rather than those of higher living Mammalia.
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  • 193
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 199 (1989), S. 363-378 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The chelonian carapace is composed of the endochondral ribs and vertebrae associated with a specialized dermis. The ribs are found in an aberrant position compared to those of all other tetrapods; they are superficial and dorsal to the limb girdles. This morphological arrangement, which constitutes the unique chelonian Bauplan, is examined from a developmental perspective. Embryos of Chelydra serpentina were studied during stages of carapace development. Tissue morphology, autoradiography, and indirect immunofluorescent localization of adhesion molecules indicate that the outgrowth of the embryonic carapace occurs as the result of an epithelial-mesenchymal interaction in the body wall. A carapacial ridge composed of mesenchyme of the dermis and overlying ectoderm is formed dorsal to the ectodermal boundary between somitic and lateral plate mesoderm. It is the anlage of the carapace margin, in which the ribs will eventually terminate. The ectoderm of the carapacial ridge is thickened into a pseudostratified columnar epithelium, which overlies a condensation in the mesenchyme of the dermis. Patterns of cell proliferation and the distribution of N-CAM and fibronectin in the carapacial ridge are consistent with patterns seen in other structures initiated by epithelial-mesenchymal interactions such as feathers and limb buds.Based on an analogy to this developmental mechanism in the development of the limb skeleton, a further analogy with the evolution of the limbs from lateral fin folds is used to form a hypothesis on the evolution of the carapace from elements of the primitive reptilian integument.
    Additional Material: 11 Ill.
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  • 194
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 200 (1989), S. 29-36 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Autologous tongues were transplanted onto the liver of the anuran Rana catesbeiana, specimens of which were sacrificed at intervals from 6 hr to 5 months after transplantation. Light and electron microscopy as well as histochemistry disclose that the grafts start to organize into cysts after 14 days. The taste organs occur in all grafts irrespective of the age of the graft. All surviving taste organs exhibit intense adenosine triphosphatase (ATPase) activity and contain fluorescent basal cells of the usual type. Ultrastructurally, the taste organs are composed of three distinct types of cells that lack nerves. The taste and basal cells retain the characteristic dense-core granules in their cytoplasm through the experimental periods. The present results suggested that the taste organs of Rana can survive ectopically in the liver for up to 5 months.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 195
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 200 (1989), S. 63-69 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Epithelium of the sea anemone Acontiophorum niveum is modified into four general arrangements of microappendages: (1) uniform microvilli covering pedal disc and column, (2) an interspersion of microvilli, ciliary cones, and kinocilia on tentacles, (3) flagella among an understory of microvilli from the oral disc, actinopharynx, filaments, and acontia, and (4) sparse flagella among irregular microvilli from endoderm. These arrangements are similar to those described previously in the epithelia of other anthozoans.
    Additional Material: 14 Ill.
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  • 196
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 200 (1989), S. 87-92 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Inserting on the buccal and esophageal foregut of Gammarus minus are numerous pairs of serially arranged dorsal dilator muscles, a single pair of lateral muscles, and two pairs of posterior muscles. Muscles of the cardiac stomach include three dorsal sets, a single pair associated with the pterocardiac ossicles, and two pairs inserting on the ventral aspect. A single pair of muscles inserts on the lateral aspect of the pyloric stomach. The extrinsic muscles of the foregut originate from exoskeletal apodemes of the cephalothoracic cuticle, sockets of the mandible, and a maxillary bridge that lies just ventral to the cardiac stomach. The extrinsic musculature of the hindgut is restricted to the rectal region and consists of paired dorsal and ventral series in an X-configuration. A single unpaired muscle inserts on the ventral midline. Extrinsic muscles of the hindgut originate from the integument of the last pleonic segment. The general arrangement of extrinsic gut muscles in G. minus is similar but not identical to that of other amphipods studied. However, the pattern is quite different from that of other malacostracans.
    Additional Material: 6 Ill.
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  • 197
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1677-1682 
    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 study has been made of vibration butt welds between plaques of polypropylene. The quality of the welds, as determined by impact tests, has been examined as a function of the welding variables: pressure and vibration amplitude. In addition, the microstructure of the welds has also been examined, classified, and correlated with the welding variables and weld quality. Penetration as a function of time shows three distinct regimes and It is shown that the impact strength of the welds is independent of time once the third regime is reached. The time required to reach the third regime decreases as pressure or amplitude increases and is more sensitive to amplitude of vibration than to pressure. The highest quality welds were produced at low pressure and low amplitude with corresponding long times to reach regime three and exhibited a unique, readily identifiable microstructure.
    Additional Material: 10 Ill.
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  • 198
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    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1705-1721 
    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 ultrasonic welding process is modeled using a five part model that includes mechanics and vibration of the parts, viscoelastic heating, heat transfer, flow and wetting, and intermolecular diffusion. The model predicts that melting and flow occur in steps, which has been confirmed by experiments. The model also indicates the possibility of monitoring joint quality by measuring the dynamic mechanical impedance of the parts during welding, which has also been verified experimentally by indirectly monitoring the magnitude of the impedance. via measurements of both the power and the acceleration of the base. When the melt fronts of the energy directors meet, at the end of welding, the dynamic impedance of the composites' interface is shown to rise rapidly. This raises the possibility of developing closed loop control procedures for the ultrasonic welding of thermoplastic composites. Ultrasonic welding of polyetheretherketone (PEEK) graphite APC-2 composites produced joints with excellent strengths.
    Additional Material: 31 Ill.
    Type of Medium: Electronic Resource
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  • 199
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1759-1765 
    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: Fluorescence spectroscopy has been employed to monitor the mixing of polymer melts with filler material. The polymer melts were low molecular weight polybutadiene and PBAN, a terpolymer consisting of 85% butadiene, 11% acrylonitrile, 4% acrylic acid, and the filler material was aluminum oxide. To carry out the fluorescence observations, a dopant chromophore was mixed into the polymer melt at very low concentrations, 10-4 to 10-6 molar or 11 to 0.11 ppm by weight. The mixing experiments were carried out using a small laboratory mixer which had glass walls for viewing the fluorescence spectra from the dopant chromophore. Fluctuations in fluorescence intensity were observed to decrease as a function of mixing time indicating that the spatial distribution of the fluorescent chromophores was becoming more uniform. Concerning the mixing of polymer melt and filler, we hypothesize that uniform mixing of ingredients is achieved when fluorescence intensity as a function of time is constant. In order to obtain quantitative support for this hypothesis, we used a fluorescence microscope to measure fluorescence intensity and optical transmittance from microscopic regions of well-mixed and poorly mixed specimens.
    Additional Material: 10 Ill.
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  • 200
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 199 (1989), S. 1-13 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This study examines the morphology of sporadic congenital microphthalmia in 1-day-old chicks, with particular emphasis on the neural retina. On the basis of the size of the eyeball it is possible to classify microphthalmia into two groups, severe and mild. In severe microphthalmia (less than 5 mm in equatorial diameter), the eyeball is severely malformed, but in most cases it shows evidence of an organized neural retina. Although ganglion cells and an optic nerve head are present in a small proportion of these retinae, we could not trace an optic nerve projection to the brain. These results indicate that some ganglion cells are able to be sustained after the period of naturally occurring cell death, suggesting either that those ganglion cells have established some contact with the central nervous system or that the presence of their axons in a rudimentary optic nerve is adequate for survival. In mild microphthalmia (greater than 5 mm in equatorial diameter), the most consistent abnormality is a defect in the pecten, which together with other abnormalities such as orbital cysts and colobomas indicates that the major abnormality occurs in the region of the choroid fissure. Associated with these defects are abnormalities within the ganglion cell layer. In some cases the number of ganglion cells was reduced, and in others the numbers of both ganglion and displaced amacrine cells were reduced. Unexpectedly, there were localized regions completely devoid of cells in the ganglion cell layer. The timing of the congenital defect may provide some clue as to the presence of a critical period in which displaced amacrine cells are formed or are sensitive to events related to ganglion cell loss.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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