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  • 1
    ISSN: 1434-601X
    Keywords: 13.75.Cs ; 25.40.Jt ; 36.10.−k
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Spectra of protons with momenta greater than 500 MeV/c following antiproton annihilation at rest in carbon and uranium nuclei have been measured. They are compared to recent results from other experiments and to predictions of an intranuclear cascade model. Evidence is presented for a substantialB〉0 component in the annihilation process, and an estimate of the magnitude of that component is made.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-601X
    Keywords: 13.75.Cs ; 21.10.Dr ; 24.90.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The momentum spectra of charged pions following antiproton annihilation at rest in carbon and uranium have been measured. This information complements our previous measurement of the neutral pion spectra. The total charged pion multiplicity is 2.84±0.10 and 2.47±0.09 for carbon and uranium, respectively, in good agreement with recent INC model predictions of 2.96 and 2.48 for the same quantities. However, structures predicted by the model near 200 MeV/c and 300 MeV/c related to delta-resonance production are not seen in the data. The total energy transfers to the nucleus are calculated to be 119±59 MeV(carbon) and 455±50 MeV(uranium). The possibility of exciting multifragmentation with a¯p beam impinging on heavy nuclei is discussed.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-601X
    Keywords: 13.75.Cs ; 21.10.Dr ; 25.90.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The energy transfer by pi-zeros in the intranuclear cascade initiated by antiproton annihilation at rest in carbon and uranium has been measured to be 28 ± 43 and 232 ± 33 MeV respectively. We estimate the total energy transfer due to all pions to be 75 ± 53 and 447 ± 42 MeV respectively. The uranium value is ∼ 17% larger than a recent theoretical prediction. No predictions for carbon are available. Given the expected increase in efficiency of energy transfer from antiproton beams at ∼ 3 GeV/c momentum, the prospects for initiating multifragmentation and disintegration of heavy nuclei at these energies appear good.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1434-601X
    Keywords: 13.75.Cs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Deuteron yields from 20–350 MeV kinetic energy in antiproton annihilation at rest in12C and238U targets are compared with a coalescence model calculation. Agreement of the data with the model up to approximately 80 MeV is good. However, from 80 to 350 MeV the model increasingly underestimates the yield, by as much as on order of magnitude. These results, along with previously reported failures to explain proton spectra with first order rescattering of pions, suggest that other mechanisms are manifest in relatively rare, high energy light nucleus emission, e.g.B 〉 0 annihilations or possible six quark interactions.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dynamic moduli G′(ω) and G″(ω) for two groups of linear polyethylene fractions (reported Mw/Mn 〈 1.2) were measured in the melt state using the eccentric rotating disk method. Values of zero shear viscosity η0 were obtained and compared with published results on similar fractions. Molecular weight data were converted to a common basis through intrinsic viscosities in trichlorobenzene (TCB) at 135°C. With recent data on Mw (light scattering) vs. [η]TCB, for linear polyethylene, the relationship at 190°C, η0 = 3.40 × 10-14(Mw)3.60, was obtained. The flow activation energy Ea was 6.4 kcal (T = 140-195°C). The plateau modulus G0N at 190°C was determined from the area under the loss modulus peak in one high-molecular-weight sample. The value obtained, G0N = 1.58 × 107 dyn/cm2, corresponds to an apparent molecular weight between entanglements of 1850. The storage compliance J′(ω) becomes anomalously large at low frequencies. The recoverable compliance J0e could not be determined for any of the fractions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Some results are reported on the linear viscoelastic properties of polybutadienes with narrow-molecular-weight distributions. The zero shear viscosity η0 varies as M3.4 in the linear samples, and viscosity enhancement is found in star-branched samples with long arms, in good agreement with results reported earlier by Kraus and Gruver. The temperature coefficient of viscosity appears to be slightly larger in stars when the arms become long. The steady state recoverable compliance J0e is 2.1 × 10 -7 cm2/dyn in linear samples of high molecular weight, but it increases to values as much as 10 times larger in the stars. The plateau modulus G0N, obtained from a composite curve for the linear samples, is 1.32 × 107 dyn/cm2. The terminal relaxation spectrum of the stars is too broad to allow an evaluation of plateau modulus.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Three methods for hydrogenating anionically prepared polybutadiene (containing about 8% vinyl double bonds) were investigated: homogeneous catalysis (alkylated transition metal salts), heterogeneous catalysis (nickel on kieselguhr; paladium on calcium carbonate), and stoichiometric reaction with in situ generated diimide. The products were characterized by intrinsic viscosity, gel permeation chromatography, infrared spectroscopy, and melt viscosity. Only the heterogeneous catalysts were found to yield completely hydrogenated products without incorporation of foreign groups and without significant change in the large-scale molecular structure of the chain. The 195°C melt viscosity of linear polybutadiene hydrogenated with heterogeneous catalysts is virtually identical with that of linear polyethylene with the same intrinsic viscosity in trichlorobenzene at 135°C. The solid state properties of hydrogenated polybutadiene, containing about 20 ethyl branches/1000 main chain atoms, closely resemble those of commercial branched polyethylene.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 3367-3381 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rutherford backscattering spectrometry (RBS) has been used to detect and quantitate the thallium concentration resulting from the thallous ethoxide derivatization of phenol and carboxylic acid groups contained in the surface region of bisphenol-A polycarbonate (PC) sheet. Hydrolysis of the PC surface prior to derivatization leads to increased thallium levels, in which the chemical nature of the thallium is shown to be of the form R-O-Tl (R = alkyl or aromatic) by electron spectroscopy for chemical analysis (ESCA). Similar trends in thallium concentrations were observed by both RBS and ESCA for PC surfaces that had been exposed for increasing lengths of time to accelerated weathering and outdoor Florida conditions. The detection limit for thallium in PC using RBS is ca. 5 × 1013 atoms/cm2. The diffusion of thallous ethoxide and transesterification of the aromatic carbonate linkage led to a thallium-containing layer 300-700 Å thick, which increased the experimental uncertainty when assaying residual uncapped polymer chains in unweathered material. During the course of the RBS analysis, the interaction of 2-MeV 4He+ with the PC substrate caused dramatic chemical and physical changes. Microscopy and profilometry indicate that a crater was formed having the same cross-sectional area as the incident ion beam with a depth (ca. 0.3-1.5 μ) that varied according to the beam energy and integrated charge. ESCA analysis provided evidence for the loss of the carbonate linkage and the appearance of carbonyl and ester groups. Infrared analysis of the crater bottom shows the appearance of O-H stretch, carbonyl functionality other than aromatic carbonate, and enhanced aromatic ring stretch vibrations. Crosslinking and subsequent densification of the polymer matrix are though to be responsible for the observed morphological changes. It is suggested that this beam-induced damage does not prohibit the use of RBS to measure high-Z elements on a PC matrix since quantitation of 1000-Å Au layers on silicon and PC gave identical results.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 7 (1969), S. 707-713 
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of the reaction product of TiCl4, Al, AlCl3, and an aromatic compound with an ether and subsequently with TiCl4 yields very pure β-TiCl3. This material, when treated with small amounts of aluminum trialkyls, is a very active catalyst for the stereospecific polymerization of isoprene. If the above reaction is stopped after the ether addition, before the addition of TiCl4, the product so obtained is largely TiCl2. Reaction variables in the preparation of TiCl3 are described as is the effect of various organoaluminum compounds as cocatalysts for polymerization.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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