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  • Chemistry  (11)
  • ASTROPHYSICS  (3)
  • 1980-1984  (11)
  • 1925-1929  (3)
  • 1
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    In:  Other Sources
    Publication Date: 2019-06-28
    Description: It is pointed out that the separate study of neutron star envelopes is a valuable technique for gaining insights into neutron star cooling calculations. It is shown that, to an excellent approximation, the temperature at the inner boundary of the envelope, T sub b, is a function only of T sub s to the 4th power over g sub s, where T sub s is the effective temperature and g sub s is the surface gravity. This result makes it possible to investigate very simply the effects of general relativity and of opacity changes on the T sub b - T sub s relation and to compare calculations by different workers, even though they use different neutron star models. It is also shown that the most important opacity source for obtaining a reliable T sub b - T sub s relation is the conductive opacity of matter when the ions are liquid. Calculations are presented in which particular attention is given to this region and the best available opacities are used.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 259
    Format: text
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  • 2
    Publication Date: 2019-06-28
    Description: The envelopes of nonmagnetic neutron stars are studied using the best available opacities and equation of state. The general relativistic equations of the structure and evolution of nonmagnetic neutron stars are discussed, and it is shown that they can be reduced to a single equation for calculating the thermal structure of neutron star envelopes. The physical input needed to solve the thermal structure equation is investigated and the numerical results of envelope model calculations are presented. It is shown that the thermal structure of neutron star envelopes is determined by the single parameter T(s) to the 4th/g(s), where T(s) is the effective surface temperature and g(s) the surface gravity of the star. This result is used to derive a number of other scaling relations, and the effects of general relativity on the envelope thermal structure are examined in detail. The results of a sensitivity analysis of the regional opacity needed to obtain a reliable relationship between the temperatures of the inner and outer boundaries of the envelope is presented.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 272; Sept. 1
    Format: text
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  • 3
    Publication Date: 2019-06-28
    Description: A method is given for determining the sensitivity of certain types of calculations to the uncertainties in the input physics or model parameters; this method is applicable to problems that involve solutions to coupled, ordinary differential equations. In particular the sensitivity of calculations of the thermal structure of neutron star envelopes to uncertainties in the opacity and equation of state is examined. It is found that the uncertainties in the relationship between the surface and interior temperatures of a neutron star are due almost entirely to the imprecision in the values of the conductive opacity in the region where the ions form a liquid; here the conductive opacity is, for the most part, due to the scattering of electrons from ions.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 204; Aug. 198
    Format: text
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  • 4
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 27-33 
    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: Solid state rolling of semi-crystalline polymers is shown to be an effective method of producing high strength, high modulus tape at acceptable production rates. High density polyethylene tape was produced having a tensile strength exceeding 300 MPa and a tensile modulus of 8.7 GPa at production rates exceeding 8 m/min. A significant factor in producing highly oriented tape by the rolling process is roll temperature. Increasing the roll temperature from 25°C to 125°C not only increases the maximum extent of orientation achievable, but increases the mechanical properties at a given degree of thickness reduction. Internal frictional heat development limited the maximum thickness reduction ratio of polypropylene to 6.6:1. This reduction was reached by rolling at 150°C. The resultant tape had a tensile modulus of 5.1 GPa and a tensile strength of 300 MPa.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 549-555 
    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: Slow crack growth behavior of medium-density polyethylene pipe samples has been investigated by applying standard and nonstandard fracture mechanics test methods. Slow crack growth rate varied by several orders of magnitude among the PE2306 materials from different manufacturers. Slow crack generated surfaces exhibit fibrous textures of varying degrees of coarseness when examined under the scanning electron microscope. When the measured fiber heights, δ/2, of these samples were plotted against the applied stress intensity factor, KI, they showed a simple power law relationship (of exponent 2). Assuming that the pulled-out fibers transmit almost uniform tensile stresses across the crazed zone at the crack front, the Dugdale-Barenblatt model was introduced to predict the fiber height. Although the model needs further modification, it provides a general power law relationship between the fiber height and the applied stress intensity factor.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 1049-1056 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental investigation of an impinging water jet freezing on a melting solid surface has been carried out. Attention was focused on the stagnation region of an axisymmetric jet. In the experiment, a water jet was directed upward against the lower end of a meltable rod, having a diameter about twice that of the jet orifice. Solid octane (m.p. - 56.5°C) and solid mercury (m.p. - 38.9°C) served as the meltable materials. A laminar-axisymmetric flow model was developed to describe melting heat transfer in the presence of jet solidification within the impingement region. Measurements of the melting rate and conditions for the onset of jet solidification were found to agree quite well with the values predicted with this model.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 27 (1981), S. 952-959 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Effects of molecular size and configuration on hindered diffusion were examined by measuring diffusion of two series of uncharged macromolecules through track-etch membranes with uniform and well-defined pore geometry. At any given Stokes-Einstein radius, diffusivities in small pores were lower for ficoll (crosslinked structure) than for dextran (more nearly linear structure).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 395-409 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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 process has been developed by which very high-modulus semicrystalline polymer films can be extruded continuously from a melt. This is accomplished by controlled cooling of the melt in a two-stage flow channel. A temperature gradient along the flow channel quenches the melt prior to an area reduction in which the polymer undergoes solid-state orientation. Analysis of high-density polyethylene tapes extruded by this process shows that they have properties similar to samples hydrostatically extruded at 120°C. Infrared analysis was used to determine both the degree of crystallinity and degree of orientation in these tapes as well as previously prepared hydrostatically extruded samples.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1249-1259 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We consider the irreversible dissociation kinetics of proteins that bind cooperatively and nonspecifically to DNA. Our model consists of an infinitely long one-dimensional nucleic acid lattice on which are bound protein ligands. A set of adjacent bound proteins forms a cluster of length n. A protein molecule may dissociate from any site within the bound cluster, not only from the ends, as was assumed in a previous model of this process due to Lohman [(1983) Biopolymers 22, 1697-1713]. By considering this additional pathway, we present a more general treatment of the dissociation kinetics of cooperatively bound ligands. We show that dissociation from the (n-2) internal positions of an n-cluster is an important pathway when the initial fractional saturation of the lattice is close to unity and the co operatively is low. When the fractional saturation is initially equal to 1 and the co operatively is low, our model does not give the zero-order dissociation kinetics predicted by the Lohman model.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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