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  • 1
    ISSN: 1434-601X
    Keywords: 23.40.−s ; 25.30.−c ; 25.85.−w
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Fission fragments from the reaction237Np(μ −,γ,f) have been measured in coincidence with muonic X-rays. The efficiency of the fission fragment detector is determined from (μ −,γ,f)-data of the same experiment. The total fission probability perμ-stopP t has been measured as well as the fission probabilities Pf of the non-radiative muonic (3d→1s)- and (2p→1s)-transitions; the latter has been divided into two parts leading to different mean excitation energiesE:P t =(54±17)%,P f (3d→1s)=(41±21)%,P f (2p→1s,E=6.218 MeV)=(61±19)%, andP f (2p→1s,E=6.525 MeV)=(57±18)%. The influence of the muon on the fission barrier is discussed. The fission probability after muon capture is compared with a calculated value using a distribution of nuclear excitation energies following muon capture and the fission probability as measured in a238U(3He,αf)-reaction.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-601X
    Keywords: 25.30.−c ; 25.85.−w ; 25.85.Ge ; 36.10.Dr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The mean life times of negative muons bound to actinide nuclei have been measured by detecting the time difference between a stopped muon and the arrival of fragments from delayed fission after muon capture. The deduced capture ratesΛ c are 1.392(4)·107/s for237Np, 1.290(7)·107/s for242Pu and 1.240(7)·107/s for244Pu. The results are compared with published data for the fission and the neutron decay channels and for the electron decay of the bound muon. Including a former measurement ofΛ c for239Pu, an isotopic dependence of the muon capture rates in the Pu isotopes is clearly observed.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-601X
    Keywords: 13.10.+q ; 14.60.Ef ; 23.20.−g ; 25.30.−c ; 25.85.−w ; 27.90.+b ; 36.10.−k
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A study of muonic238U has been performed in a combined (μ −,γ f) and (μ −,γγ) coincidence experiment to investigate the role of non-radiative transitions and their fission probabilities. An augmentation of the outer fission barrier ofΔE b =(0.6±0.1) MeV due to the presence of the muon is deduced. A significant contribution to the prompt fission yield not only results from the (2p→1s) and (3d→1s) non-radiative transitions, but also from other radiationless transitions. Specifically, the measured fission probabilities of the transitions (2p→1s), (3d→1s), and (3p→1s) are (1.5±0.4)%, (5.7±1.7)%, and (5.3±1.9)%, respectively.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1434-601X
    Keywords: 23.40.Bw ; 13.10.+q ; 25.85.−w ; 25.30.−c ; 27.80.+w ; 13.60.−r
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The probability for delayed muon induced fission of209Bi has been determined from a (μ −,f 1 f 2) measurement. The measured fission probability P f =(4.2±0.7)×10−5 is compared with theoretical predictions. The high fission threshold reaction seems well suited for studying the influence of two-body meson-exchange currents in nuclear muon capture.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 125-129 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The in vivo pathway of folding and subunit assembly of a trimeric bacteriophage protein has been studied by characterizing precursors to the native protein and by analyzing temperature-sensitive mutations that kinetically block the pathway. The native trimer is formed via an intermediate composed of three partially folded chains, the protrimer. At 39°C, temperature-sensitive mutations prevent the formation of both the native trimer and the protrimer, possibly by destabilizing earlier intermediates. However, the mutations do not affect the stability of the native protein, formed at 30°C. Thus, these mutations identify amino acid residues involved in interactions that determine the folding pathway.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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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: Messungen der Linienbreite in den 1H NMR-Spektren von D2O Lösungen von Polymethacrylsäure (PMA) und von hydrolysiertem Butylvinyläther/Maleinsäureanhydrid Copolymer zeigen eine scharfe Abnahme der Linienbreite der Seitenkettenresonanzsignale bei einem Neutralisationsgrad α ≈ 0,2. Dies ist der Bereich, in dem schon früher potentiometrische Titrationen einen Konformationsübergang aufzeigten. Ein solcher Wechsel tritt weder bei der Polyacrylsäure noch beim Methylvinyläther/Maleinsäureanhydrid Copolymer auf. Die Art des Konformationsübergangs wird auf der Grundlage der Rotationsfreiheit der Seitenketten um die Hauptkette diskutiert.
    Notes: Linewidth measurements on the 1H NMR spectra of D2O solutions of poly(methacrylic acid), (PMA), and the hydrolyzed form of butyl vinyl ether/maleic anhydride copolymer show a sharp decrease in the linewidths of side chain resonances at a degree of neutralization α ≈ 0,2. This is the region in which potentiometric titrations previously have shown a conformational transition to occur. Such a change does not occur in poly(acrylic acid) on the one hand and methyl vinyl ether/maleic anhydride copolymer on the other. The nature of the transition is discussed in terms of the freedom of rotation of the side chains about the main chain.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 36 (1988), S. 495-509 
    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: The series of nylon 612 copolymers was synthesized from caprolactam (C) and laurolactam (L) at 145°C. The 50/50 C/L molar ratio copolymer was found to have the minimum melting temperature (Tm ) for the series. The glass transition temperatures (Tg 's) of the copolymers were affected by the crystallinity of the copolymers. The Tg was at a minimum for the 50/50 copolymer for crystalline samples. However, for amorphous samples there was a decrease in Tg with increasing L content. Percent crystallinity was determined by differential scanning calorimetry and X-ray techniques. It was found that the degree of crystallinity was at a minimum for copolymers of 70/30 to 40/60 C/L ratios. Coefficients of linear thermal expansion (CLTE) were obtained for the copolymers at 10°C intervals from 20 to 70°C for dry and from 20 to 50°C for samples conditioned at 50% relative humidity and 50°C. The dry samples gave lower initial values, but had a greater temperature dependence than the conditioned samples. As expected, the CLTE was found to be lowest for samples exhibiting the highest crystallinity. The tensile strengths and moduli decreased rapidly with increasing L up to the 70/30 C/L ratio after which they remained relatively constant. Elongations reached maximums between 70/30 and 40/60 C/L ratios. An inverse relationship was found between crystallinity and impact strength.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2441-2451 
    ISSN: 0887-624X
    Keywords: fluorinated diaminobiphenyls ; poly(amic acid)s ; polyimides ; spin-coated films ; physical property characterization ; thermal expansion coefficient ; electronics applications ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new fluorinated diamine monomers, 3,3′-diamino-5,5′-bis(trifluoromethyl)biphenyl and 3,3′-diamino-6,6′-bis(trifluoromethoxy)biphenyl, as well as a known nonfluorinated analog, 3,3′-diaminobiphenyl, were synthesized. Reaction of these diamines with rigid, highly rod-like dianhydrides produced poly(amic acid)s and polyimides, which were spin coated and thermally treated to produce polyimide films for evaluation in electronics applications. It was hoped that these polyimide films would exhibit an ideal combination of low thermal expansion, reduced water absorption, and low dielectric constant but with improved elongation due to the “crankshaft” nature of the 3,3′-biphenyl unit. Unlike polyimide films from analogous 4,4′-diaminobiphenyls, however, the 3,3′-diaminobiphenyl-based polyimides did not yield low in-plane thermal expansion coefficient in spin-coated films. In some cases high elongation was achieved, but with high thermal expansion. These new diamines may nevertheless find utility in polyimides and polyaramides for membrane, fiber, and other applications. Additionally, they may be useful in modifying the properties of polymer backbones via copolymerization. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2441-2451, 1997
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 167-182 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The available experimental date on the kinetics of unfolding and refolding of small proteins are reviewed. Excluding slow transitions in the unfolded protein due to cis-trans isomerization of peptide bonds, the rate-limiting transition state in both unfolding and refolding is concluded to be a high-energy distortion of the fully folded state. Partially folded intermediates are undoubtedly important for folding, but their formation is normally not rate limiting. A simple model is used to illustrate some of the aspects of protein-folding energetics.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 251-257 
    ISSN: 0887-6266
    Keywords: poly(aryl-ether-ether-ketone) (PEEK), solvent-induced crystallinity in ; crystallization of PEEK, solvent-induced ; sorption of solvents in PEEK, crystallinity induced by ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The amount and structure of the crystals formed by the solvent-induced crystallization (SIC) following a sorption-desorption cycle of five fluids (benzene, toluene, chloroform, methylene chloride, and carbon disulfide) in amorphous PEEK was determined by wideangle x-ray scattering (WAXS). The SIC crystal structure was compared with that produced by thermal methods, both those formed at low temperature by heating the amorphous material 10-20°C above Tg or by cooling from the melt. Although smaller in size, the SIC crystals are tighter and more organized than those produced thermally. The WAXS data indicates that all five fluids produce approximately 35% crystallinity in PEEK. Gravimetric data suggest that a low-density region, consisting of either microvoids or highly disordered amorphous region, surrounds the crystals.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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