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  • 1
    ISSN: 1434-601X
    Keywords: 23.40.Hc ; 21.10.Dr ; 21.10.Pc ; 27.60.+j ; 29.30.Kv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract With the use of the58Ni+50Cr fusion-evaporation reaction and chemically selective on-line mass separation, the EC/β + decay of104Sn was studied byγ-ray and conversionelectron spectroscopy. In the course of these studies, a new 15.7-s isomeric state of104In was observed. Reinvestigation of theβ-decays of the two heavier even isotopes of tin, produced in the58Ni+58Ni reaction and mass separated without chemical discrimination, brought new information on the decay of106Sn and108Sn. The QEC values of104Sn,106Sn and108Sn were determined to be 4550 −250 +300 keV, 3200±100 keV and 〈 2270 keV, respectively. In the data analysis, the emphasis is put on the identification of the 0+ → 1+ Gamow-Tellerβ transitions and determination of their strengths. For104−110Sn, the total Gamow-Teller strengths are measured to be 20% to 30% of that predicted by the single-particle shell model with the inclusion of pairing correlations and core polarization. Predictions of the decay properties of the as yet unobserved102Sn and100Sn are made.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 332 (1989), S. 275-284 
    ISSN: 1434-601X
    Keywords: 23.40.Hc ; 21.10.Dr ; 27.60.+j ; 29.30.Kv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Neutron-deficient isotopes of cadmium were produced in thep(600 MeV)+natSn spallation reaction. The ISOLDE facility provided mass-separated beams of these isotopes. The production yield was 103 to 104 atoms/s for100Cd and roughly two orders of magnitude less for98Cd. The properties of the100Cd→100Ag decay were studied in detail by X-ray,γ-ray and conversion electron spectroscopy. Forty nineγ-transitions were assigned to this decay, and all but five of them were placed in the decay scheme. The half-life was determined to be 49.1±0.5 s. TheQ EC value of 3890±70 keV was deduced from a comparison of experimental and theoreticalβ +/(EC+β + probability ratios. Seven 0+→1+ Gamow-Teller transitions with log ft values between 3.5 and 4.9 were identified. The total (summed) strength is about five times smaller than predicted by the shell model for the transformation of ag 9/2 proton into ag 7/2 neutron. The quenching of the Gamow-Teller strength and other questions of nuclear structure are discussed for the100Cd decay. The properties of98Cd are inferred by extrapolation of104,102,100Cd data, and some preliminary experimental results on98Cd decay are presented.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 329 (1988), S. 11-20 
    ISSN: 1434-601X
    Keywords: 21.10.−k ; 27.60.+j ; 27.70.+q
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In theN=83 nucleus151Er we observed the isomericE3 transition in conversion electron measurements following on-line mass separation and located its 0.6 s 27/2− isomer at 2.586 MeV. Gamma-ray data establish a 4.7(3)% Gamow-Tellerβ-decay branch proceeding to high-spin states above 2 MeV excitation in151Ho. A weakβ-decay branch of 0.7(3)% was also observed for the 0.5 s 27/2− isomer in the149Dy isotone, and it was established that a similar 27/2− E3-isomer does not occur in153Yb. First results on the151Tm and151Er ground-stateβ-decays are briefly discussed.
    Type of Medium: Electronic Resource
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  • 4
    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 theories of the minor phase (domain) formation in polyblends rendered as emulsions it is usually assumed that the size and shape of the domains are the result of melt viscosity effects (Taylor, Wu) or viscoelasticity effects (VanOene, Elmendorp) being balanced by interfacial tension. This assumption would predict a monotonic decrease of the domain size to a final limiting size with increasing energy of mixing. However, a systematic study of the dependence of domain morphology on industrial mixing processes which was carried out on a “model” LDPE/PS (2/1) mixture and the related polyalloy (i.e., the same mixture with a corresponding block copolymer as compatibilizer) does not support this expectation. Doirain size was found to go through a minimum as mixing energy was increased. A similar minimum was seen in data on specific volume of the melt vs. mixing energy, which indicates a correlation between melt specific volume and domain size. Calculation of the approximate surface area of the domains using a simple model of domain shape indicated that total interfacial energy in the polyblend and/or polyalloy is a trivial part of the mixing energy introduced. These calculations also indicated that if compatibilizer was located entirely at the interface, the surface layer would have a thickness of about 90 nm. Some micrographs seem to show such a surface layer. We propose that an abrasion mechanism is responsible for the early stage of the dispersion process, and that the final domain size may be controlled by a dispersion-coalescence equilibrium. This is compared with the theories of final particle size proposed by VanOene and Wu.
    Additional Material: 13 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 29 (1989), S. 617-624 
    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 details some of the immediate findings for phase morphology formation and persistence in an industrial melt mixing of a polyblend/alloy (‘PB’/‘PBA’). Estimation of the minor phase domain size in a polyblend is feasible if the viscoelasticity functions, interfacial tension of the component-polymers, and the mixing process shear stress level are available. Clusters of domains are formed in the mixer (following streamlines). During steady flow in capillaries the clusters are forming rings which result from the flow velocity profile. Quantitative description of the clusters requires an expansion of image analysis software to account for the interdomain spacing in the clusters, as well as for their pattern. The on-line rheometry was found useful for monitoring coalescence and the effectiveness of the compatibilizer: higher “stiffness” of the PAB melt compared with that of PB shows up in measurements of complex viscosity and modulus. Further study is required, however, for correlating domain spacing and the real time rheometry data (esp. the relaxation spectrum plateau [13]). Finally, the study of phase morphology for the “model” polyblend provides an insight into the melt deformation history in an industrial mixer. It is expected that the distribution of domain sizes would correlate with the pass frequency in the mixing blocks [41], stress distribution in the extruder, and coalescence of the dispersed (“minor”) phase.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 23 (1983), S. 618-626 
    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: Particular rheology compositions (PRC) so far observed for blends of polyolefins are confirmed with composition dependence of melt elasticity and viscosity functions for polypropylene/rubbers and blends of other commercial polymers. Particular morphology at PRC was indirectly ascertained from the composition dependence of specific volume, vT-compositions for which the maximum vT observed are those of minimum viscoelasticity. Direct evidence from scanning electron microscopy (SEM) indicates that the disperse morphology undergoes distinct change at PRC: from uniform into bimodal, with coarser core. Rubber rich mixtures display stratified texture confirming that the melt elasticity ratio (Van Oene's) criterion for disperse/stratified morphology transition is valid in case of polypropylene/rubber blends. For a set of polymers of given melt elasticity ratios and at a composition ratio, static and rotational distributive mixers generate polyblends differing significantly in the melt rheology - morphology interaction.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 82-91 
    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: Set of procedures employing melt viscoelasticity functions for selecting components and composition of the binary polyblends and estimating minor phase domain size is introduced and illustrated with examples. The procedures intended for Computer Aided Manufacture of the polyblends (CAMOBLE) are based on shear stress dependent viscoelasticity ratios, and the selection of the composition exploits stress dependent synergism of the viscoelasticity functions. Also used is auxilary procedure for composition selection is based on verified blending laws accounting for interaction and shear effects. Evaluation of the performance characteristics (“mechanical properties”) is illustrated with a modified Kerner model.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1153-1165 
    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 review of current knowledge of the composition dependence of polymer-blend processability and morphology shows that development of industrial blends requires use of a semiempirical approach, based on the particular rheological composition (PRC) concept. Selecting blend composition in the close proximity to PRC and employing factorial experiments for the mixing process allows the development of successful industrial polyethylene/polypropylene blends designed for film and blow-molding applications.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 9
    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 comprehensive study of polyethylene extrusion was carried out with an instrumented extruder on several screws differing in geometry and paralleled with capillary rheometry of the extrudate leading to melt viscosity and elasticity functions. Assuming Oldroyd's constitutive equation for molten polyethylene and the extrudate melt temperature oscillation (ΔTm) as a measure of the process stability and an indication of melt mixing quality, it was found that the product of the dimensionless numbers (Deborah, De and Brinkman, Br) correlates well (r = 0.93) with ΔTm. Since the Br and De groups follow from the rheological characteristics of the melt and the extrusion process parameters, a relationship of type: ΔTm = a + b (De) (Br) appears useful in designing an extrusion process (for a polymer of known rheology) with respect to its stability, and indirectly, its mixing efficiency.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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