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  • 1
    ISSN: 1432-2048
    Keywords: Chalcone synthase ; Footprinting in vivo ; Gene expression (transient) ; Light regulation (UV-B photoreceptor, blue-light photoreceptor) ; Petroselinum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the chalcone synthase (chs) promoter from parsley [Petroselinum crispum Miller (A.W. Hill)] for the existence of separate promoter elements responsible for transcriptional activation of the chs gene by UV-B and by blue light. A combination of in-vivo footprinting in parsley cells and light-induced transient expression assays with different chs promoter constructs in parsley protoplasts was used. Dark controls and bluelight-irradiated cells gave identical in-vivo footprints on the chs promoter. Pre-irradiation with blue light prior to a UV-B-light pulse is known to cause a shift in the timing of UV-B-light-induced increase in chs transcription rates. This shift was also manifested on the DNA template, since UV-B-light-induced in-vivo footprints in cells pretreated with blue light were detected earlier than in cells which had been irradiated with a UV-B-light pulse only. Although there was a clear shift in the timing of footprint appearance, the patterns of footprinting did not change. Light-induced transient-expression assays revealed that the shortest tested chs promoter which retained any light responsiveness, was sufficient for mediating both induction by UV light and the blue-light-mediated kinetic shift. These findings argue against a spatial separation of UV-B- and blue-light-responsive elements on the chs promoter. We interpret these data by postulating that the signal transduction pathways originating from the excitation of UV-B- and blue-light receptors merge at the chs promoter, or somewhere between light perception and protein-DNA interaction.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Computational optimization and applications 2 (1993), S. 47-75 
    ISSN: 1573-2894
    Keywords: Shortest-paths ; parallel algorithms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Four new shortest-path algorithms, two sequential and two parallel, for the source-to-sink shortest-path problem are presented and empirically compared with five algorithms previously discussed in the literature. The new algorithm, S22, combines the highly effective data structure of the S2 algorithm of Dial et al., with the idea of simultaneously building shortest-path trees from both source and sink nodes, and was found to be the fastest sequential shortest-path algorithm. The new parallel algorithm, PS22, is based on S22 and is the best of the parallel algorithms. We also present results for three new S22-type shortest-path heuristics. These heuristics find very good (often optimal) paths much faster than the best shortest-path algorithm.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Computational optimization and applications 3 (1994), S. 7-26 
    ISSN: 1573-2894
    Keywords: network programming ; assignment ; integer programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This manuscript presents a new heuristic algorithm to find near optimal integer solutions for the singly constrained assignment problem. The method is based on Lagrangian duality theory and involves solving a series of pure assignment problems. The software implementation of this heuristic, ASSIGN+1, successfully solved problems having one-half million binary variables (assignment arcs) in less than 17 minutes of wall clock time on a Sequent Symmetry S81 using a single processor. In computational comparisons with MPSX and OSL on an IBM 3081D, the specialized software was from 100 to 1,000 times faster. In computational comparisons with the specialized code of Mazzola and Neebe, we found that ASSIGN+1 was 40 times faster. In computational comparisons with our best alternating path specialized code, we found that ASSIGN+1 was more than three times faster than that code. This new software proved to be very robust as well as fast. The robustness is due to an elaborate scheme used to update the Lagrangean multipliers and the speed is due to the fine code used to solve the pure assignment problems. We also present a modification of the algorithm for the case in which the number of jobs exceeds the number of men along with an empirical analysis of the modified software.
    Type of Medium: Electronic Resource
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