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  • 11
    Electronic Resource
    Electronic Resource
    Approaches to controlled polymerization of methyl acrylate through functional anionic initiators (1991)
    Springer
    Polymer bulletin 25 (1991), S. 77-81 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Controlled ‘living’ polymerization of methyl acrylate has been achieved at room temperature using functional carbanionic initiators in THF solvent. Methyl acrylate oligomers with reactive chain ends have been synthesized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00338902
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  • 12
    Electronic Resource
    Electronic Resource
    Theory of neutron scattering for gapless neutral spin-1 collective mode in graphite (2005)
    Springer
    The European physical journal 43 (2005), S. 175-185 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Using tight binding band picture for 2D graphite, and the Hubbard interaction, recently we obtained a gapless, neutral spin-1 collective mode branch in graphite [Phys. Rev. Lett. 89, 016402]. In this paper we present a detailed RPA analysis of the Neutron Scattering cross section for this collective mode. Near K-point and very close to Γ-point, the intensity of neutron scattering peaks vanishes as q3. This is shown using a simple Dirac cone model for the graphite band structure, which captures the small-q behavior of the system. As we move away from the Γ- and K-points in the Brillouin zone of the collective mode momenta, we can identify our collective mode quanta with spin triplet excitons with the spatial extent of the order of a few to a couple of lattice parameter a, with more or less anisotropic character, which differs from point to point. We also demonstrate that the inclusion of the long range tail of the Coulomb interaction in real graphite, does not affect our spin-1 collective mode qualitatively. This collective mode could be probed at different energy scales by thermal, hot and epithermal neutron scattering experiments. However, the smallness of the calculated scattering intensity, arising from a reduced form factor of carbon 2pz orbital makes the detection challenging.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2005-00040-8
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  • 13
    Electronic Resource
    Electronic Resource
    Unusual Photon Energy Dependence of the Cooper Pair Breaking Rate in YBa2Cu3O7−δ Epitaxial Thin Films (1999)
    Springer
    Journal of superconductivity 12 (1999), S. 675-680 
    Details
    ISSN: 1572-9605
    Keywords: YBCO ; Cooper pair ; thin films ; ultrafast phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The transient photoimpedance response of epitaxial YBa2Cu3O7−δ thin films has been studied using 100 fs Ti:Sapphire laser pulse excitation. Both temperature and photon energy dependence of the fast optical response signal (whose temperature dependence can be explained by a kinetic inductance model involving Cooper pair breaking) were studied. The pair breaking rate is strongly photon energy-dependent, with a resonance around 1.5 eV with a width of only 100 meV, which is very surprising given the strong electron correlation in this metallic system and may be explained in terms of the stripe phase model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007708304186
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  • 14
    Electronic Resource
    Electronic Resource
    On the statistical mechanics of the traveling salesman problem (1986)
    Springer
    Journal of statistical physics 45 (1986), S. 1-25 
    Details
    ISSN: 1572-9613
    Keywords: spin glass ; N-P complete optimization problems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We consider the statistical mechanics of the traveling salesman problem (TSP) and develop some representations to study it. In one representation the mean field theory has a simple form and brings out some of the essential features of the problem. It shows that the system has spontaneous symmetry breaking at any nonzero temperature. In general the phase progressively changes as one decreases the temperature. At low temperatures the mean field theory solution is very sensitive to any small perturbations, due to the divergence of some local susceptibilities. This critical region extends down to zero temperature. We perform the quenched average for a nonmetric TSP in the second representation and the resulting problem is more complicated than the infinite-range spin-glass problem, suggesting that the free energy landscape may be more complex. The role played by “frustration” in this problem appears explicitly through the localization property of a random matrix, which resembles the tight binding matrix of an electron in a random lattice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01033073
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  • 15
    Electronic Resource
    Electronic Resource
    Comparative role of salps and other zooplankton in the cycling and transport of selected elements and natural radionuclides in Mediterranean waters (1985)
    Springer
    Biogeochemistry 1 (1985), S. 353-360 
    Details
    ISSN: 1573-515X
    Keywords: element and radionuclide cycling ; zooplankton ; gelatinous plankton ; fecal pellets ; vertical flux
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Salps, salp fecal pellets and other zooplankton species were analyzed for a suite of elements and natural radionuclides to assess their role in the biogeochemical cycling of nuclides in oceanic waters. The nuclide/Al ratios in organisms normalized to the same ratio in crustal rock indicated that Ca, Sr, Zn, Cu, U,210Po, and210Pb are enriched in the organisms. The concentrations of Fe, Al, Th isotopes and210Pb in salps and fecal pellets were about an order of magnitude higher than those in salps, whereas Ca, Cu, Zn, Mn and Po were higher by factors of about 2–5. Fluxes via salp defecation were higher than those which have been measured in crustacean zooplankton species, a result primarily due to the high defecation rates characteristic of salps. High nuclide levels in salp fecal pellets coupled with high defecation rates and presumed high salp biomass in many areas underscore the importance of these indiscriminate filter feeders in packaging and transporting to depth particulate-associated nuclides in surface waters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02187377
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  • 16
    Electronic Resource
    Electronic Resource
    Studies on the utilization of single cell protein by the silkworm Bombyx mori (1984)
    Springer
    Entomologia experimentalis et applicata 36 (1984), S. 61-68 
    Details
    ISSN: 1570-7458
    Keywords: Bombyx mori ; silkworm ; algae ; single cell protein ; consumption ; utilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Des chenilles du dernier stade de Bombyx mori, alimentées sur mûrier additionné de Spirulina fusiformis comme source de protéine de cellule isolée (SCP), atteignent en 6 jours le poids larvaire maximum de 2090 mg; les chenilles témoins consommaient pendant 9 jours pour obtenir leur poids larvaire final de 1470 mg. Les quantités consommées, les coefficients d'assimilation et de conversion ont augmenté substantiellement chez les chenilles avec SCP. Des augmentations significatives de critères économiques, comme les poids de cocon, de nymphe et de cogul, ont été observées avec l'addition de SCP par rapport aux témoins. Environ 15% du S. fusiformis marqué a été incorporé directement dans les tissus larvaires. La présence de SCP dans l'intestin a permis une meilleure conversion des protéines foliaires consommées.
    Notes: Abstract Final-instar larvae of Bombyx mori fed mulberry leaves, supplemented with Spirulina fusiformis (Woronichin) as a source of single cell protein (SCP), required 6 days to attain a maximum larval weight of 2090 mg; control group larvae needed 9 days to attain a final larval weight of 1470 mg. Quantity of feeding, assimilation and conversion efficiencies increased substantially in the SCP-fed group. Significant improvements in the economic characters such as cocoon, pupal, and shell weights were obtained in the SCP supplemented larvae in comparison to the normal leaf fed larvae. About 15% of the labelled S. fusiformis was directly incorporated into larval tissue. Presence of SCP in the gut facilitated better conversion of consumed leaf protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00345206
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  • 17
    Electronic Resource
    Electronic Resource
    Mechanical Properties of Calcium-Substituted Yttrium Chromite (1999)
    Springer
    Journal of materials science 18 (1999), S. 819-822 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006605620688
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  • 18
    Electronic Resource
    Electronic Resource
    Role of crack size in the bi-modal static fatigue failure of a cordierite glass and glass-ceramic (1987)
    Springer
    Journal of materials science 22 (1987), S. 871-876 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A study was conducted of the static fatigue behaviour at room temperature of a cordierite glass and glass-ceramic with model flaws of two different sizes introduced by the indentation fracture method. For the cordierite glass the stress intensity exponent, N, for sub-critical crack growth inferred from the dependence. of time-to-failure on stress was the same for the two different crack sizes and showed good agreement with the value of N for data obtained in an earlier study for dynamic fatigue and by the double-torsion method. For the cordierite glass-ceramic, which consisted of larger crystallites (a few micrometres in size) embedded in a primarily crystalline fine-grained matrix, the static fatigue response depended strongly on crack size, also observed during dynamic fatigue. This effect was attributed to the relative size difference between the cracks and the crystallites. The small cracks could propagate in a planar fashion, whereas the larger cracks were subject to toughening by crack-deflection around the crystallites and a corresponding decrease in the rate of sub-critical crack growth. An analysis for the case of idealized “bi-modal” crack-size dependent sub-critical crack-growth indicated that, for a cordierite glass-ceramic with small cracks, the role of the larger crystallites serves to introduce a “pseudo” fatigue-limit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01103523
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  • 19
    Electronic Resource
    Electronic Resource
    Effect of test method and crack size on the fracture toughness of a chain-silicate glass-ceramic (1986)
    Springer
    Journal of materials science 21 (1986), S. 2365-2372 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The fracture toughness of a canasite glass-ceramic with a highly acicular, interlocked grain structure was measured by a number of different methods. The values at room temperature obtained by the chevron-notch, short-bar and notched-beam methods ranged from 4 to 5 M Pa m−1/2, well above literature values for other glass-ceramics. Similar values of toughness were obtained by the fracture of bars with indentation cracks introduced with loads ranging from 1.96 to 400 N, but only for crack sizes 〉200 μm, with lower values for cracks of smaller size. The toughness values obtained by the direct measurement of the size of the indentation cracks were appreciably lower than the values obtained by all other methods over the total range of indentation loads and corresponding crack size. SEM fractography showed that the surface within the indentation cracks was appreciably smoother than the surrounding fracture surface. The high values of fracture toughness were attributed to the combined mechanisms of crack-deflection and microcrack-toughening due to the stress-enhanced creation of microcracks caused by the residual stresses which arise from the thermal expansion anisotropy of the canasite monoclonic crystal structure. The strong negative temperature dependence of the fracture toughness suggests that at room temperature microcrack toughening represents the primary contributing mechanism to the fracture toughness. The combined effects of crack-deflection and microcrack-toughening can lead to the development of glass-ceramics with greatly improved resistance to crack propagation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01114280
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  • 20
    Electronic Resource
    Electronic Resource
    Enhancement of O2 and CO2 Transfer Through Microporous Hollow Fibers by Pressure Cycling (1998)
    Springer
    Annals of biomedical engineering 26 (1998), S. 1044-1054 
    Details
    ISSN: 1573-9686
    Keywords: Lung ; Gas exchange ; Mathematical model ; O2 and CO2 transfer ; Microporous hollow fibers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract An intravascular gas exchange device for the treatment of respiratory failure consisted of a multitude of blind-ended hollow fibers glued in a pine-needle arrangement to a central gas supply catheter. It has previously been shown that gas desorption rates can be significantly enhanced by cycling gas pressure between a hypobaric level of 130 and an ambient level of 775 Torr. In this study, influences of the cycling frequency (f) and the cycle fraction during which hypobaric pressure is applied (Θ) were investigated. Rates of O2 desorption from O2-saturated water and CO2 desorption from CO2-saturated water into a manifold containing 198 fibers, 380 μm in diameter, were measured over a range of f from 0.2 to 1.0 Hz, Θ from 0.1 to 0.8, and fiber lengths from 4 to 16 cm. Relative to operation at ambient pressure, pressure cycling increased O2 transfer 3–4 times and CO2 transfer 4–6 times when the water flowed over the fiber manifold at 2.3 l/min. Transfer rates were relatively insensitive to f and Θ with 80–90% of maximum enhancement obtained when Θ was as low as 0.2. Transfer rates increased continuously with fiber length, implying that pressure cycling reduced the intra-fiber resistance to gas diffusion. A mathematical diffusion model which utilized only two adjustable parameters, a mass transfer coefficient for O2 and for CO2, simulated the trends exhibited by desorption data. © 1998 Biomedical Engineering Society. PAC98: 8745Hw, 8790+y
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1114/1.115
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