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  • Electronic Resource  (23)
  • 1
    Electronic Resource
    Electronic Resource
    Observations on the natural history of the Gulf of Mexico sturgeon (Acipenser oxyrinchus de sotoi Vladykov 1955) in the Suwannee River, southeastern United States (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Ecology of freshwater fish 5 (1996), S. 0 
    Details
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: From 1986 to 1994, we collected 3,098 Gulf of Mexico sturgeon (Acipenser oxyrinchus de sotoi) during their spring migration from the Gulf of Mexico to the Suwannee River, Florida. We estimated population size and described migratory and seasonal growth patterns of sturgeon in the Suwannee River, using data from tag returns, movement of ultrasonic-lagged fish and weight records. Population size estimates for 3.0- to 81.0-kg Gulf of Mexico sturgeon in the Suwannee River ranged from 1,504 to 3,066 fish. Sturgeon migrated from the Gulf of Mexico into the Suwannee River from mid-February to early May. Fish moved upstream and remained within a 2-km upstreamdownstream “home” area. These sites were closely associated with undenvater springs that discharge into the river. Sturgeon migrated downstream and into the Gulf of Mexico in October and November. In the Gulf of Mexico, ultrasonic-tagged fish were located in the Suwannee Sound area just north of Cedar Key, Florida. On an annual basis, fish gained an average of 20% of their body weight while in the Gulf of Mexico and lost about 12% of their weight during their stay in the Suwannee River. We observed movement of tagged sturgeon between the Suwannee and Apalachicola Rivers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0633.1996.tb00130.x
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  • 2
    Electronic Resource
    Electronic Resource
    Electric field-induced structure in poly(acrylonitrile) (1979)
    Springer
    Colloid & polymer science 257 (1979), S. 913-919 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Experimental evidence has been obtained for alteration of the molecular organization in polyacrylonitrile which has been given a thermoelectric treatment that creates a persistent electrical polarization. These studies have involved infrared spectroscopy and X-ray diffractometry, and their results have been interpreted as suggesting the existence of dipolar clusters in polarized material. These clusters cause polyacrylonitrile chains to adopt a structure which is different from any previously reported for this material. It is suggested that stability of the polarized state of polyacrylonitrile results, in part, from this new molecular organization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01520713
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  • 3
    Electronic Resource
    Electronic Resource
    Morphologie und Deformation von aus der Schmelze gesponnenen Polyäthylen-Fasern (1974)
    Springer
    Colloid & polymer science 252 (1974), S. 182-182 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01555662
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  • 4
    Electronic Resource
    Electronic Resource
    Epitaxial crystallization of poly (γ-benzyl L-glutamate) on alkali halide single crystals (1968)
    New York : Wiley-Blackwell
    Biopolymers 6 (1968), S. 469-477 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Single crystals of poly(γ-benzyl L-glutamate) were formed by epitaxial crystallization from solution in mesitylene on NaCl, KI, and KCl (001) cleavage faces. From electron microscopy and diffraction studies, the structure of these overgrowths was determined to be that of lamellae containing chain-folded α-helical macromolecules. The usual type of crystal perfection, that of ordered helix axes and disordered side groups, was exhibited by this synthetic polypeptide. Unique orientation regimes were observed with each substrate.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1968.360060404
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  • 5
    Electronic Resource
    Electronic Resource
    Relationship between self-seeded and epitaxial crystallization from polymer solutions: A potentially new method for molecular weight separation and a new decoration method for alkali halides (1970)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1467-1490 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It was established that polyethylene and polyoxymethylene crystallize epitaxially on NaCl cleavage faces over a temperature range in which the usual polymer single crystals dissolve but a crystallization memory remains due to very small quantities of self-seeding nuclei persisting in the solution. By performing this epitaxial crystallization in the presence of self-seeding nuclei, it could be established that epitaxial crystallization at these elevated temperatures involves only the very largest molecules in the distribution. Further, the self-seeding nuclei themselves could be isolated for observation, and these results were found consistent with previous predictions. By utilizing both the adhesion of these nuclei to NaCl and the selective nature of the epitaxial crystallization, the largest molecules could be extracted and reintroduced again to the same or different solutions. This opens up the possibility of a novel kind of chromatography for the separation and characterization of the highest molecular weight end of a distribution to a sensitivity which cannot be approached by other methods. The epitaxy phenomenon itself, under the circumstances involved, provides a new decoration method for the study of the surface topography of alkali halides. The origin of such as epitaxy occurring at low supercoolings and terminating at a limiting thickness raises important questions regarding long-range forces and some unsettled features in the theory of chain-folded crystal growth in polymers.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1970.160080905
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  • 6
    Electronic Resource
    Electronic Resource
    Formation of bimodal crystal textures in polypropylene (1975)
    Springer
    Journal of materials science 10 (1975), S. 870-886 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Electron microscopy, selected area electron diffraction, X-ray diffraction, and dynamic-mechanical testing have been used to study flow-crystallized and hot drawn isotactic polypropylene. As a result of these investigations, it was found that bimodal crystal textures can apparently be formed by at least two different treatments, but the corresponding morphologies are completely different. Flow-induced crystallization was observed to result in a microstructure of lamellae oriented perpendicular to the flow direction, while hot drawing of polypropylene films above a critical temperature produced a morphology of microfibrils lying parallel to the draw direction. Below this critical temperature, drawing produced a fibrillar morphology having only a typical unimodal fibre texture. As a result of information obtained here, a mechanism involving epitaxial deposition of chain segments onto growing lamellae is concluded to be responsible for formation of the bimodal crystal texture in flow-crystallized material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01163082
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  • 7
    Electronic Resource
    Electronic Resource
    Studies of epoxy resin systems: Part B: Effect of crosslinking on the physical properties of an epoxy resin (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1213-1220 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An epoxy system consisting of diglycidyl ether of butanediol, DGEB, cured with 4-4′ diaminodiphenyl sulfone, DDS, has been used for a study of the effect of crosslinking density on the properties of the epoxy resin. Because of the low curing rate at room temperature and the low glass-transition temperature, this system was amenable to a wide range of controlled cross-linking density. The crosslinking density was monitored by FTIR (Fourier transform infrared spectroscopy), which followed the change in concentration of the epoxy groups during the curing reaction. The bulk density was found to increase linearly with the crosslinking density. The modulus, the upper yield point, the lower yield point, and the degree of retraction of a deformed sample all increased with the degree of crosslinking. The thermally stimulated depolarization (TSD) β-peak was found to vary with crosslinking density, but the γ-peak was not changed. The TSD a peak was found to decrease in strength, but increased in temperature as the crosslinking density increased. This observation suggests that TSD measurements arc a good monitor of crosslinking density of epoxy resins, particularly near the final stage of the crosslinking reaction.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760221807
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  • 8
    Electronic Resource
    Electronic Resource
    Flow-induced crystallization of polypropylene in stretched ribbons (1976)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 16 (1976), S. 217-221 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Ribbons of molten polypropylene have been extruded into a thermostatted chamber and subjected to elongations ranging as high as 4400-fold. Some of these ribbons have been shown to possess the unusual ability of recovering nearly all of the strain from large levels of stretch (≤100 percent). This property, as well as the magnitude of the tensile yield drop, has been found to be directly proportional to the uniaxial character of the flow present at the moment of crystallization. The structure in the final solid films has been characterized by wide angle X-ray diffraction and crystal orientation distribution. Both of these factors have been found to be proportional to the character of flow at the moment of crystallization. Finally, the temperature in the thermostatted chamber has been shown to affect the character of the flow.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760160316
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  • 9
    Electronic Resource
    Electronic Resource
    Studies of epoxy resin systems: Part A: A study of the origins of the secondary relaxations of epoxy resins by thermally stimulated depolarization (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1205-1212 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The relaxation behavior of several epoxy resin systems, which have systematic structural differences, has been studied by the thermally stimulated discharge (TSD) technique. Two TSD peaks centered at about 115°K (β peak) and 185°K (β peak) were found for epoxy resins cured with a diamine. Structural change, either in the epoxy resin molecule or the amine molecule, did not seem to affect those two peaks. The TSD thermogram of the DGEBA (diglycidyl ether of disphenol A) epoxy resin part only showed a small new peak at 160°K instead of the ft peak at 185°K. This result, together with the fact that postcuring increased β peak height, leads to the conclusion that the ft peak is most likely due to the newly-created molecular segment during the curing reaction. The peak at 160°K was assigned to the epoxy group. This assignment was based on the fact that the 160°K peak of an epoxy homopolymer, which has fewer epoxy groups, was smaller than that of the parent DGEBA. The β and γ peaks were found to be of distributed characteristics, and the distribution of activation energy was studied by the partial heating method.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760221806
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  • 10
    Electronic Resource
    Electronic Resource
    Development of stress-crystallized morphology during melt-spinning of polypropylene fibers (1973)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 13 (1973), S. 295-299 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Melt-spinning of isotactic polypropylene was performed in an effort to assess how the flow field that exists within a filament affects final as-spun fiber morphology. It was concluded that the molten filament deforms chiefly by elongational flow, with some small amount of shearing flow bearing localized near the filament periphery. The resulting crystal texture is mostly comprised of lamellae oriented perpendicular (chain direction parallel) to the fiber axis, but a minority population of crystallites whose orientation is orthogonal (chain direction perpendicular) to the primary population is also present in these fibers. Post-drawing steps initially cause crystallites to rotate toward the axial direction, while the chains within them undergo intralamellar slip and become better oriented parallel to the fiber axis. At larger extensions, lamellar crystallites are pulled into microfibrillar units.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760130409
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