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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 7260-7270 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The size of free-volume holes in neat poly[(ethylene glycol)23dimethacrylate] [poly((EG)23DMA)] and in the same polymer doped with 0.6 mol/kg LiCF3SO3 have been studied as a function of temperature in the range between 100 and 370 K using positron annihilation lifetime spectroscopy. The results are compared with differential scanning calorimetry and ionic conductivity measurements. In both systems, the hole volume νh shows a typical glass-transition behavior, i.e., a small linear increase with temperature below the glass transition temperature Tg and a steeper increase above Tg. From these measurements Tg was estimated to be 233 K (neat polymer) and 240 K (polymer with salt) and the coefficients of the thermal expansion of the hole volume were determined. The fractional free volume (f=0.080) and the number density of holes (Nh=0.6 nm−3) were also estimated. Below Tg the average hole volume of the polymer electrolyte is larger than in the neat polymer. This is consistent with the bulky character of the CF3SO3− anion. Above Tg the salt-doped system shows the lower hole volume of the two systems, probably caused by a reduced segmental mobility as a consequence of the interactions of the Li+ ions with the ethylene oxide units of the polymer. Based on the free-volume theory of Cohen–Turnbull the ionic conductivity σ is correlated with the mean hole volume νh. A linear relation between log(σT 0.5) and 1/νh was observed to be valid for variations of the conductivity over several orders of magnitudes. From these plots critical hole sizes of γν*=0.65 nm3 (neat polymer) and 0.87 nm3 (polymer-salt system) were estimated. The parameters B and T0 of the Vogel–Tamman–Fulcher equation were also determined, as well as the apparent activation volume ΔVapp by pressure-dependent conductivity measurements. The cationic transference number in the polymer-salt system was determined by pulsed field gradient-nuclear magnetic resonance to be t+(approximate)0.3. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 4476-4487 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Coherent anti-Stokes Raman Scattering (CARS) is used to monitor the rovibrational population distribution of prompt H2 produced from H2CO+hν→H2+CO. Photolysis is performed on K=1 lines of the 2141 S1←S0 transition. Scanning CARS spectroscopy is employed, with suppression of the nonresonant background of the H2CO. The detection sensitivity is ∼1012 cm−3 per quantum state. Helium buffer is added to cool the product translation to near room temperature. States v=0–4, J=1–9 are detected. The vibrational distribution peaks at v=1. The rotational distributions in the vibrational states are somewhat Boltzmann with "temperatures'' ranging from 1700 to 2500 K for v=3–0. The total energy, 29 500 cm−1, is chosen near the threshold for dissociation. The internal energy of H2(v, J) sums with that found earlier for CO(v, J) and for translation to this total. An average impact parameter of 0.9 A(ring) with a spread of a few tenths A(ring) is found. H2 pushes away from a point about 0.3 A(ring) beyond the C nucleus of CO. The distributions are controlled by the dynamics of the fragments as they separate in the steep, repulsive exit valley of the potential energy surface; they are entirely different from the statistical distributions typical for bond fission without a barrier. Rotational relaxation of H2 in collisions with He occurs at 300 K with a rate constant of (9±3)×10−13 cm3 molecule−1 s−1 for J=3→J=1 and (2.6±1)×10−13 cm3 molecule−1 s−1 for J=5→J=3.
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Nuclear Instruments and Methods in Physics Research Section A: 296 (1990), S. 89-97 
    ISSN: 0168-9002
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 27 (1979), S. 0 
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Seismic velocity anisotropy is predicted for cracked rocks containing either a naturally-occurring or an artificially-induced preferred orientation of cracks. Methods developed for the study of velocity anisotropy in the uppermost mantle have been applied to the in situ measurement of P-wave velocity anisotropy in fractured Carboniferous Limestone in Northwest England. At three different sites, first-arrival travel-time data has been obtained using conventional refraction equipment and a weight-drop source. Velocity anisotropy of 15–29% is identified with directions of maximum and minimum velocities that can be broadly related to previously mapped orientations of joints.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 82 (1973), S. 291-304 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The absorption of neutral amino acids byArenicola marina was studied using anin vitro preparation of the alimentary canal. Regional variation in absorption was observed, with the intestine being the region of greatest uptake. The L enantiomorphs of the neutral amino acids alanine and leucine were shown to be actively absorbed by the intestine as was the D enantiomorph of alanine. A saturable component was demonstrated in the absorption of L-alanine and this was shared by L-methionine, which was found to competitively inhibit alanine uptake. Inhibition of L-alanine uptake also occurred in the presence of other neutral, basic and acidic amino acids. The greatest inhibition was found with the L stereoisomers of methionine, leucine, valine, histidine and phenylalanine, whilst proline, lysine and aspartic acid decreased uptake to a smaller extent.
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 344 (1990), S. 497-497 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 137-142 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The protease-sensitive self-flocculation of Flavobacterium sp. strain 304 was studied by analysing genetically or biochemically obtained flocculationdeficient cells. The flocculation of this species was dependent on three separable characteristics: (a) a sufficiently high buoyant density, (b) the capability for initial aggregate formation and (c) aggregate stabilization.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 137-142 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The protease-sensitive self-flocculation of Flavobacterium sp. strain 304 was studied by analysing genetically or biochemically obtained flocculation-deficient cells. The flocculation of this species was dependent on three separable characteristics: (a) a sufficiently high buoyant density, (b) the capability for initial aggregate formation and (c) aggregate stabilization.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 73-79 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The cultivated and uncultivated bacterial communities of an activated sludge plant were studied. Two samples were taken and a total of 516 bacterial isolates were classified into groups using their whole-cell protein patterns. The distribution of bacteria into protein-pattern groups differed significantly between the two samples, suggesting variation in culturable bacterial flora. Partial 16S rRNA gene sequences were determined for representatives of the commonest protein-pattern groups. Most of the sequences obtained were previously unknown, but relatively closely related to known sequences of organisms belonging to the α, β or γ subclasses of the proteobacteria, the first two subclasses being predominant. This classification of bacteria isolated on a diluted nutrient-rich medium differed from recent culture-dependent studies using nutrient-rich media. The uncultivated bacterial community was studied by analyzing ten partial 16S rRNA gene sequences cloned directly from activated sludge. None of the cloned sequences was identical to those determined for culturable organisms; or to those in the GenBank database. They were, however, related to the α or β subclasses of the proteobacteria, or to the gram-positive bacteria with a high G+C DNA content.
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