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  • Polymer and Materials Science  (539)
  • PROPULSION SYSTEMS  (170)
  • ASTROPHYSICS
  • FLUID MECHANICS
  • 1970-1974  (831)
  • 1973  (250)
  • 1972  (282)
  • 1971  (299)
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  • 1970-1974  (831)
Year
  • 1973  (250)
  • 1972  (282)
  • 1971  (299)
  • 1974  (273)
  • 1970  (257)
  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 6 (1972), S. 59-79 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Advantages of a hollow-fiber hemodialyzer have been well described. The goal of this program was to provide a working model of a noncellulosic hollow fiber artificial kidney with nonthrombogenic blood-contacting surfaces, low blood-priming volume and low pressure drop, a satisfactory rate of urea transport, and high rate of ultrafiltration of water. Also, the reliability and utility of these devices was to be demonstrated through clinical evaluation.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 1213-1224 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthetic details of solution polymerization in benzene and bulk polymerization of vinylferrocene are reported. In benzene solutions, with azobisisobutyronitrile (AIBN) as the initiator, small yields of low-polydispersity low molecular weight (M̄n ≃ 5000) polyvinylferrocene is obtained. However, high yields can be obtained by continuous or multiple AIBN addition. Higher molecular weight polymers and binodal polymers can be obtained as the monomer concentration is increased. In bulk polymerizations, yields of 80% can be obtained. The molecular weight increases as temperature decreases from 80 to 60°C in bulk polymerizations, and an increasing amount of insoluble polymer results. The soluble portion is often binodal, the higher molecular weight node consisting of an increasingly branched structure. Lower molecular weight polymer was readily fractionated into narrow fractions from benzene-methanol systems, but higher molecular weight polymer proved impossible to fractionate into narrow fractions due to branching.
    Additional Material: 3 Ill.
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  • 3
    Publication Date: 2019-07-13
    Description: A computer code which will rapidly calculate time-optimal low thrust transfers is being developed as a mission analysis tool. The final program will apply to NEP or SEP missions and will include a variety of environmental effects. The current program assumes constant acceleration. The oblateness effect and shadowing may be included. Detailed state and costate equations are given for the thrust effect, oblateness effect, and shadowing. A simple but adequate model yields analytical formulas for power degradation due to the Van Allen radiation belts for SEP missions. The program avoids the classical singularities by the use of equinoctial orbital elements. Kryloff-Bogoliuboff averaging is used to facilitate rapid calculation. Results for selected cases using the current program are given.
    Keywords: PROPULSION SYSTEMS
    Type: AIAA PAPER 73-1074 , Electric Propulsion Conference; Oct 31, 1973 - Nov 02, 1973; Lake Tahoe, NV
    Format: text
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 89-106 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Raman spectra of poly-γ-benzyl-L-glutamate, poly-L-leucine, poly-L-valine, and poly-L-serine are reported. For the α-helical polymers, the conformationally sensitive amide I, II, and III modes are observed in the Raman as, well as the infrared. For the β form, the Raman effect, supplies the infrared inactive inphase motion which is useful for the determination of a parallel or antiparallel chain alignment. Modes characteristic of the specific polypeptide are also observed which are insensitive to conformation.
    Additional Material: 4 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 1339-1360 
    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: Free-radical polymerization in a flow reactor represented by the tanks-in-series model with backflow was considered. Conversions and molecular weight distributions were computed as functions of the backflow parameter, and the results were compared with the conversion and molecular weight distribution from a CSTR and those from a plug-flow reactor. Backflow was found to be undesirable for the polymerization mechanism under investigation. Values of the degree of segregation for the tanks-in-series model were calculated by using Zwietering's approach as a function of backflow.
    Additional Material: 11 Ill.
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  • 6
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The anionic polymerization of styrene was studied in tetrahydropyran as solvent by kinetical and conductivity measurements in order to determine all thermodynamic and kinetical parameters of the formerly proposed three-way-mechanism. These parameters are compared with those in other ethereal solvents. It turns out that the largely differing individual propagation rate constants of the contact-ion pairs, of the solvent-separated ion-pairs, and of the free anions are hardly influenced by the solvent. The unusually great influence of the solvent on the overall polymerization rate is caused by shifting the equilibria between the above mentioned different species.
    Notes: Kinetische und konduktometrische Messungen am System Polystyrl-Natrium in THP werden mit dem Ziel durchgeführt, alle in dem früher vorgeschlagenen dreiteiligen Reaktionsschema vorkommenden thermodynamischen und kinetischen Parameter zu bestimmen und mit den in anderen Lösungsmitteln gefundenen Werten zu vergleichen. Es zeigt sich, daß die Geschwindigkeitskonstanten der Monomeraddition an das Kontaktionenpaar, das solvatgetrennte Ionenpaar und das freie Anion, die sich um Größenordnungen unterscheiden, vom Lösungsmittel nur geringfügig beeinflußt werden. Der ungewöhnlich große Einfluß der Lösungsmittel auf die Polymerisationsgeschwindigkeit geschieht durch Verschiebung der Gleichgewichte zwischen den genannten Formen der Kohlenstoff-Natriumbindung.
    Additional Material: 10 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 10 (1972), S. 1415-1445 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A reaction rate model of fracture in polymer fibers is described. This model assumes that bond rupture is governed by absolute reaction rate theory with a stress-aided activation energy. It is demonstrated that the key in obtaining good agreement between the model and experiment lies in taking proper account of the variation of stress on the tie-chain molecules. The more taut chains rupture first, and the load is redistributed among the remaining unruptured tie chains. The effect of varying the temperature both in the model and in experiments on fracture in fibers is explored. Good agreement between predictions of the model and experiment is possible only with an undeterstanding of the distribution in stress on the tie chains. The distribution in stress on the chains was experimentally determined by monitoring the kinetics of bond rupture with electron paramagnetic resonance (EPR) spectroscopy. Temperature is found to have two effects on macroscopic strength. (1) The thermal energy aids the atomic stress in breaking the atomic bonds; as a consequence the rate of bond rupture of a family of bonds under a given molecular stress is increased. In this respect temperature might be viewed as decreasing the “strength” of a bond. (2) Temperature also serves to “loosen” the molecular structure and in this way modify the distribution in stress on the tie chains. To explain bond rupture and macroscopic fracture behavior quantitatively, account must be taken of both effects.
    Additional Material: 13 Ill.
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  • 8
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Electron paramagnetic resonance (EPR) spectroscopy was used to compute the surface bond rupture density in polyurethane and to determine the phase experiencing fracture in styrene-butadiene block copolymers when these elastomers are subjected to mechanical degradation by grinding. The polyurethane grinding was done at temperatures above and below the glass transition Tg; 0.155 × 1013 radicals/cm2 of fracture surface area were formed above the Tg and 4.42 × 1013 radicals/cm2 for grinding below the Tg. These values are essentially equal to those found earlier for spherulitic polymers. In all cases the fracture appears able to progress along preferential paths so as to rupture significantly fewer molecular chains than one would expect on the basis of calculations of the number of chains passing through each square centimeter of cross section. Comparison of EPR spectra formed by grinding styrene-butadiene copolymer with those of styrene and butadiene above indicated that at cryogenic temperature, the fracture in the copolymer takes place in the butadiene phase.
    Additional Material: 5 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2161-2176 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The frequencies and intensities of the laser Raman spectra of poly-L-lysine (PLL) have been observed in the following studies: (1) the thermally induced α-to-β transition which occurs with increasing temperature at high pH; (2) the ionized form to α transition at 10°C by increasing pH; and (3) the ionized form to α transition by ionic strength at low pH.The frequency-dependent bands which have been observed are the amide I (in H2O), amide I′ (in D2O), amide III, and C-C stretch. It has been found possible to assign an unique set of frequencies and intensities to each conformation of PLL of α, β, and ionized form. In this way the nature of the conformations intermediate in the transitions can be determined. The frequencies of the amide III and amide III′ are very weak in the α-helix and somewhat higher than usual in the β form. Hence it appears the amide III and amide III′ bands may differ from one type of polypeptide to another with the same backbone conformation.
    Additional Material: 11 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 15 (1971), S. 1425-1435 
    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: Cotton fibers were treated with an aqueous solution of ceric ammonium nitrate and examined with the electron microscope. The greatest deposition of cerium occurred in the primary wall due largely to the reaction with noncellulosic constituents in this area of the fiber. The use of ceric ions for an electron-microscopic stain was found ineffective for producing the desired contrast in the cotton fiber.
    Additional Material: 15 Ill.
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