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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4910-4912 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The feasibility of a high-temperature superconducting switch based on the principle of the superconducting vector switch (SVS) is discussed. This switch exploits the anisotropy in electrical conductivities of the high-temperature superconductors. Underlying the SVS mechanism is the ability to turn on/off large superconducting currents confined to the CuO2 planes that characterize these materials using lower currents flowing normal to the planes. The required conditions to optimize the switch and increase the gain are presented.
    Type of Medium: Electronic Resource
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  • 2
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    Unknown
    Baltimore, Md. : Periodicals Archive Online (PAO)
    Behavioral science. 39:4 (1994:Oct.) 293 
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  • 3
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    Unknown
    London, etc. : Periodicals Archive Online (PAO)
    Slavonic and East European review. 68:1 (1990:Jan.) 154 
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 370 (1994), S. 31-34 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Recent research has revealed the nature of the reactions that underlie the conversion of solar energy into chemical energy by photosynthesis. Armed with this knowledge, a blueprint for new technologies to exploit solar energy is ...
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-5079
    Keywords: molecular biology ; Photosystem II ; psbK gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The psbK gene encodes a small protein of Photosystem II. The gene has previously been cloned and sequenced in Synechocystis sp. PCC 6803. Our new results, presented here, confirm the conclusions of Ikeuchi et al. Based on Northern hybridization and primer extension analyses, we show that psbK is transcribed as a monocistronic message in this cyanobacterium. Analysis of DNA sequence immediately upstream of the transcription start site revealed an E. coli-like-10 consensus sequence. A deletion mutant was constructed where the psbK gene was replaced by a kanamycin resistant cartridge. In situ complementation experiments, as well as Southern and Northern hybridization analyses, confirmed that the mutant strain contains a lesion in psbK. The psbK-less mutant could grow photoautotrophically as well as photoheterotrophically both in liquid culture and on agar plates. The rate of growth was slightly less compared with the wild-type as clearly observed by in situ complementation experiments. Although the mutant showed correspondingly lower rates of electron transport, thermoluminescence, oxygen flash yield and chlorophyll a fluorescence measurements did not detect any significant modification of the reactions of PS II. Moreover, the mutant was no more susceptible to excess light than the wild-type. It is, therefore, concluded that the product of the psbK gene is not crucial for PS II activity and possibly plays some other role in the metabolism of Synechocystis.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5079
    Keywords: Photosystem II ; charge recombination ; flash absorption spectrocopy ; time-resolved fluorescence spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A Photosystem two (PS II) core preparation containing the chlorophyll a binding proteins CP 47, CP 43, D1 and D2, and the non-chlorophyll binding cytochrome-b559 and 33 kDA polypeptides, has been isolated from PS II-enriched membranes of peas using the non-ionic detergent heptylthioglucopyranoside and elevated ionic strengths. The primary radical pair state, P680+Pheo-, was studied by time-resolved absorption and fluorescence spectroscopy, under conditions where quinone reduction and water-splitting activities were inhibited. Charge recombination of the primary radical pair in PS II cores was found to have lifetimes of 17.5 ns measured by fluorescence and 21 ns measured by transient decay kinetics under anaerobic conditions. Transient absorption spectroscopy demonstrated that the activity of the particles, based on primary radical pair formation, was in excess of 70% (depending on the choice of kinetic model), while time-resolved fluorescence spectroscopy indicated that the particles were 91% active. These estimates of activity were further supported by steady-state measurements which quantified the amount of photoreducible pheophytin. It is concluded that the PS II core preparation we have isolated is ideal for studying primary radical pair formation and recombination as demonstrated by the correlation of our absorption and fluorescence transient data, which is the first of its kind to be reported in the literature for isolated PS II core complexes from higher plants.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of elasticity 28 (1992), S. 111-122 
    ISSN: 1573-2681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The paper investigates the perturbation in an otherwise uniform stress field in an elastic half-space due to a doubly-periodic array of small hemispherical holes at the free surface. The solution is obtained using three potential functions of double Fourier series form in Galerkin's strain potential solution, the coefficients of which are determined using the collocation method. The unperturbed field is taken to be one of uniform plane stress parallel to the free surface. Two special cases are studied—uniform tension and uniform shear stress. Numerical results for these cases can be generalized by superposition to give solutions for a general state of biaxial plane stress. It is found that, for both tension and shear, the maximum stress concentration occurs at the bottom of the holes. The stress concentration factor increases with the ratio of hole spacing to radius, approaching the known solution for a single hemispherical hole at large ratios.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of elasticity 26 (1991), S. 75-86 
    ISSN: 1573-2681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The classical formulation of the ‘homogeneous’ problem of a curved bar loaded only by and end force involves the assumption of an appropriate stress function with four arbitrary constants and the determination of these constants from the boundary conditions. Since there are five boundary conditions, four on the curved edge and one at the end, the solution is only possible because the coefficient matrix of the resulting algebraic equations is singular. This in turn means that certain inhomogeneous problems in which the curved edges are loaded by sinusoidally varying tractions cannot be solved using apparently appropriate stress functions. Additional stress functions which resolve this difficulty are introduced and an example problem is solved, which exhibits qualitatively different behavior from that in more general cases of loading. The problem is then reconsidered as a limiting case of sinusoidal loading of arbitrary wavelength. It is shown that the solution of the latter problem appears to become unbounded as the special case is approached, but that when the end conditions have been correctly satisfied by superposing an appropriate multiple of the end-loaded solution, the limit can be approached regularly and the correct special solution is recovered. The limiting process reveals a general procedure for determining the additional stress functions required for the special case. Similar relationships between homogeneous and inhomogeneous solutions for other common geometries are discussed.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of elasticity 31 (1993), S. 141-161 
    ISSN: 1573-2681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The elastodynamic super-Rayleigh/subseismic indentation paradox is examined in this paper. Both the Craggs/Roberts steady-state problem and the Robinson/Thompson transient problem are reconsidered. Certain features of these solutions are discussed from a new point of view, by considering asymptotics at the end of the contact region, the influence of contact inequalities, energetics of the process and existence/uniqueness.
    Type of Medium: Electronic Resource
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