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  • Articles  (117)
  • Chemical Engineering  (104)
  • Cells, Cultured  (13)
  • Physical Chemistry
  • 1975-1979  (74)
  • 1970-1974  (43)
  • Physics  (117)
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  • Articles  (117)
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  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 420-424 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Creep tests up to 106 seconds in tension and compression were conducted on polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), and polypropylene (PP). Measurements of longitudinal and lateral strain provided values for tension and compression strain ratio. These increased with time and stress for PMMA and PVC from about 0.38 to 0.44. The results for PP increased from 0.44 to above 0.5 in. tension and showed a decreasing ratio in compression, which suggested a time and stress dependent structural change. Volumetric strain was computed from the linear strains and plotted against stress and axial strain. Except at 102 seconds, the relationships were non-linear up to volumetric strains of about 0.3% and in the cases of PMMA and PVC there were greater changes of volume in tension than compression.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 18 (1978), S. 660-667 
    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 operation of a twin screw extruder processing a powder or granular solid is reviewed. The operating variables of screw speed and barrel temperature profile interact with a number of design parameters -  screw design, die geometry, feed zone geometry and with the material properties, in determining machine performance. The factors that determine output and pressure development are specified in a sequence of block diagrams. The dynamic response of an operating machine to disturbances in the steady state conditions is explained in the light of the established relationships and interpreted in conventional control theory terms. Attention is drawn to the importance of mixing in the chambers formed by the screw channels and of the residence time distribution in determining the quality of the final product.
    Additional Material: 14 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 14 (1974), S. 429-434 
    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 is devoted to the mechanical properties of impregnated asbestos-cements. We studied the influence of the degree of impregnation and of the nature of the resin on the modulus of elasticity and on the strength of the materials. The impregnation of asbestos-cement by polymeric resins produces composites of outstanding mechanical properties. The relative increase in flexural and tensile strength is much higher for mortar and concrete but the improvement produced by the polymer on asbestos-cement is especially significant if one takes into consideration the already high absolute strengths of the materials.
    Additional Material: 8 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 13 (1973), S. 398-400 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Creep data in uniaxial tension, compression and shear on PVC, PMMA, and PP sheet were used to test analytical correlating procedures. It was shown that shear and uniaxial creep could be closely related using the concept of shear stress and shear strain on octahedral planes. This correlating procedure was only effective if due allowance was made for the different creep response in simple tension and compression for each of these materials. It was also shown that the relationship between the viscoelastic creep moduli and strain ratio, which is stress and time dependent, has the same form as the analogous relationship between the linear elastic constants.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 10 (1970), S. 86-93 
    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: Boron fiber reinforced composites have been extensively evaluated in epoxy resin matrix materials, which are satisfactory for applications in comparatively moderate environments, and are usually inapplicable at temperatures in excess of 400°F. For use in high temperature environments in excess of this figure, it is necessary to use more thermally stable resins. A modified phenolic resin was selected for this application because of the versatility of the material and the successful performance of phenolics in glass fiber reinforced structures. The modifications increased the viscosity and tack of the formulation so that consolidation could not be readily accomplished by a combination of tension and heat during the winding process, so that a multi-stage winding process with intermediate consolidation steps became necessary. Winding a complex path to make a uniformly thick wall on a frustrum required further modifications to the basic winding process. The successful solution of these problems and the development of structurally sound composites was the primary object of this work.
    Additional Material: 15 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 18 (1978), S. 299-305 
    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: One of the problems to be considered in the application of the Halpin-Kardos theory to crystalline polymers is the relation of the crystal length to the only related and measurable parameter, spherulite size. The number average crystal length has been computed for various two and three dimensional models for the crystallization process assuming heterogeneous nucleation. It was found that high values of crystallinity are consistent only with lamellae that are stacked in a parallel fashion. For these systems the number average lamellar length is 0.55 of the spherulite radius. Lower crystallinity polymers have an average lamellar length 0.3 to 0.5 of the spherulite radius, the actual value being determined by the radius. For spherulites of radius 1μm or greater, the size of the primary nucleus has no noticeable influence on the average lamellar length.
    Additional Material: 8 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 18 (1978), S. 869-874 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of time of indentation and time of recovery on the Rockwell hardness, of a series of glassy and crystalline polymers has been determined. An analytical technique, based on conventional viscoelastic approaches, has been developed. This technique permits the resolution of the hardness number into its components of permanent deformation, retarded elastic compression, and retarded elastic recovery. Subtraction of components due to retarded elastic response results in hardness numbers dependent only the time-dependent permanent deformation. Extrapolation of this data to zero time results in an absolute or time-independent value of Rockwell hardness, designated Ro.
    Additional Material: 14 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 11 (1971), S. 335-343 
    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: Polymethyl methacrylate, polyacetal and polypropylene samples were subjected to constant-load uniaxial creep in tension and compression up to 3% strain in times up to 105 sec. A higher creep resistance was obtained in compression compared with tension due to the influence of free volume on mobility. Square wave cyclic creep tests alternately in tension and equal compression for dwell times of 10, 100, 1000 sec were also conducted on each material up to a total time of 105 sec. Under low cyclic creep stresses tension creep cancelled out compression creep in each successive half cycle so that there was no overall increase in creep strain as cycling proceeded. The unidirectional creep data was used successfully to predict this behavior. At higher cyclic stress levels creep strain range increased steadily throughout the test indicating a softening process. A few tests were conducted in unidirectional and cyclic stress relaxation on polymethyl methacrylate.
    Additional Material: 16 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 14 (1974), S. 371-381 
    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: Recent morphological studies of plasticized and unplasticified poly(vinyl chloride) (PVC) are reviewed. Suspension polymerized PVC contains particles in a number of different size ranges 100-200Å, 1000-5000Å, 1μ and larger. The larger size particles are broken down during plasticization but both the 100Å and the 1000Å suspension particles retain their identity. The visibility, and presumably, coalescence of these particles is a function of the processing conditions. In particular, the size of the 100Å particle increases with plasticizer content and is most distinct as characterized both by small angle x-ray scattering and electron microscopy for milling temperatures in the 160-170°C. range. Consideration is given to the effect of these particles, their structure, and interrelationship on the rheological properties of the resins.
    Additional Material: 17 Ill.
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  • 10
    Publication Date: 1979-08-17
    Description: Mouse spinal neurons grown in tissue culture were used to study the membrane effects of the benzodiazepine flurazepam and the naturally occurring purine nucleoside inosine, which competes for benzodiazepine receptor sites in the central nervous system. Application of inosine elicited two types of transmitter-like membrane effects: a rapidly desensitizing excitatory response and a nondesensitizing inhibitory response. Flurazepam produced a similar excitatory response which showed cross-desensitization with the purine excitation. Flurazepam also blocked the inhibitory inosine response. The results provide electrophysiological evidence that an endogenous purine can activate two different conductances on spinal neurons and that flurazepam can activate one of the conductances and antagonize the other.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉MacDonald, J F -- Barker, J L -- Paul, S M -- Marangos, P J -- Skolnick, P -- New York, N.Y. -- Science. 1979 Aug 17;205(4407):715-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/37602" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Benzodiazepines/*metabolism ; Cells, Cultured ; Electric Conductivity ; Flurazepam/antagonists & inhibitors ; Inosine/*metabolism/pharmacology ; Ligands ; Mice ; Neurotransmitter Agents/metabolism ; Receptors, Drug/*metabolism ; Receptors, Neurotransmitter/metabolism ; Spinal Cord/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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