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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Algorithmica 23 (1999), S. 14-30 
    ISSN: 1432-0541
    Keywords: Key words. Parallel computation, Competitive analysis, Communication delay, Scheduling, Compiler.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. We apply the methodology of competitive analysis of algorithms to the implementation of programs on parallel machines. We consider the problem of finding the best on-line distributed scheduling strategy that executes in parallel an unknown directed acyclic graph (dag) which represents the data dependency relation graph of a parallel program and which is revealed as execution proceeds. We study the competitive ratio of some important classes of dags assuming a fixed communication delay ratio τ that captures the average interprocessor communication measured in instruction cycles. We provide competitive algorithms for divide-and-conquer dags, trees, and general dags, when the number of processors depends on the size of the input dag and when the number of processors is fixed. Our major result is a lower bound Ω (τ / log τ ) of the competitive ratio for trees; it shows that it is impossible to design compilers that produce almost optimal execution code for all parallel programs. This fundamental result holds for almost any reasonable distributed memory parallel computation model, including the LogP and BSP model.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2753-2759 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Macroscopic instabilities are governed by transport-determined plasma profiles and transport, in turn, is affected by instabilities. It is clear that neither transport process nor the behavior of instabilities can be treated in isolation. A model is developed for investigating the effects of the instabilities on global energy confinement in tokamaks. The results clearly demonstrate that magnetohydrodynamic (MHD) instabilities coupled with the transport process change not only the value of global energy confinement time, but also, perhaps more importantly, the energy confinement scaling law. While considering MHD effects, global energy confinement becomes sensitively dependent on the boundary transport conditions, and the cases with and without MHD stability can result in quite different parameter behavior of the global energy confinement. Such coupling should be considered when attempts are made to analyze the global energy confinement in tokamaks. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 7689-7693 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the morphological evolution of strained, low-mismatch Si0.67Ge0.33 and Si0.75Ge0.25 films on Si (110), covering both the elastic and early stages of plastic relaxation during growth. It is seen that three-dimensional island formation is suppressed at 650 and 700 °C on the Si (110) surface, unlike on the Si (100) surface under the same growth conditions. Instead, a high density of ledges oriented along an elastically hard 〈111〉 direction, and a very low density of nanowires oriented along the single in-plane 〈110〉 azimuth are observed. Continued growth leads to the formation of misfit defects oriented along the 〈110〉 direction and disappearance of the nanowires. © 1999 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 212-216 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The epitaxial growth of thin (∼20–40 nm) Si buffer layer on Si(110) leads to the formation of ∼100-nm-wide, uniformly sized faceted pits. The cause of these rhombohedral pits is revealed to be the overgrowth of a homoepitaxial layer over clusters of coherent contaminant particles, possibly SiC. Deposition of Ge on such "pitted" surfaces shows highly selective nucleation of pairs of coherent islands at the opposite corners of the pits along the 〈110〉 direction. Continued deposition leads to strain relaxation of one or both of the islands within the pit which then rapidly coarsen to form a single Ge island within the pit. Our observations offer insight into heterogeneous nucleation mechanisms important for producing controlled arrays of self-assembled quantum dots. © 1998 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 20 (1997), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The Arabidopsis seedling can follow two contrasting developmental programmes, photomorphogenesis in light and skotomorphogenesis in darkness. CONSTITUTIVE PHOTOMORPHOGENIC I (COP1) is an essential regulatory gene required for repression of seedling photomorphogenic development in darkness. Recent mutational and overexpression analyses of the COP1 gene suggest a central role for COP1 in light control of seedling development and point to functional implications of its structural domains. Cell biological studies of COP1 have provided a clue to how light regulates the repressive activity of COP1 and thus seedling development.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 20 (1997), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Light signals perceived by photoreceptors are transduced into the nucleus to regulate gene expression and development. The COP9 protein complex localized in the nucleus has a central role in modulating light-regulated development, and may have a role in regulating development in general in all organisms. This review considers recent advances in the study of the COP9 complex and its sub-units in plant and animal systems, and discusses the possible functional implications.
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  • 7
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Gene therapy has been investigated and used for the treatment for malignant tumors and ischemic diseases in both animal models and clinical settings. Previously, effective ulcer healing with intragastric administration of growth factors such as VEGF (vascular endothelial growth factor) and PDGF ...
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Theory of computing systems 30 (1997), S. 547-558 
    ISSN: 1433-0490
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract. We present a randomized parallel algorithm for constructing the three-dimensional convex hull on a generic p-processor coarse-grained multicomputer with arbitrary interconnection network and n/p local memory per processor, where n/p ≥ p 2+ε (for some arbitrarily small ε 〉 0). For any given set of n points in 3-space, the algorithm computes the three-dimensional convex hull, with high probability, in $O((n\log{n})/p)$ local computation time and O(1) communication phases with at most O(n/p) data sent/received by each processor. That is, with high probability, the algorithm computes the three-dimensional convex hull of an arbitrary point set in time $O((n\log n)/{p} + \Gamma_{n,p})$ , where Γ n,p denotes the time complexity of one communication phase. The assumption n/p ≥ p 2+ε implies a coarse-grained, limited parallelism, model which is applicable to most commercially available multiprocessors. In the terminology of the BSP model, our algorithm requires, with high probability, O(1) supersteps, synchronization period $L = \Theta((n\log n)/{p})$ , computation cost $O((n\log n)/{p})$ , and communication cost O((n/p) g).
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  • 9
    ISSN: 1432-203X
    Keywords: Key words Somatic hybridization ; RAPD ; Citrus huanglongbin ; Sexual and graft incompatibility ; Aurantioideae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Protoplasts isolated from `Page' tangelo (Minneola tangelo × clementine) cell suspension cultures were electrically fused with mesophyll protoplasts of orange jessamine [Murraya paniculata (L.) Jack]. Shoots were regenerated after 6 – 10 months of culture, but they were extremely recalcitrant to producing roots in root-induction medium. Complete plantlets were formed via micrografting. Chromosome counting of shoot tips revealed they were tetraploids (2n = 4x = 36). Glutamateoxaloacetate transaminase isozyme and randomly amplified polymorphic DNA analysis confirmed their hybridity. Orange jessamine is immune to citrus huanglongbin, a severe disease of citrus, but sexual incompatibility and limited graft compatibility exist between Citrus and orange jessamine. The cell fusion technique may make it possible to transfer the huanglongbin resistance trait from orange jessamine to Citrus.
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  • 10
    ISSN: 1432-2242
    Keywords: Key words Somatic hybridization ; Hexaploid ; RAPD ; Chromosome number variation ; Genetic improvement ; Aurantioideae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Chinese wampee [Clausena lansium (Lour.) Skeels], a sexually incompatible relative of citrus, is commercially cultivated in South China. In this study, embryogenic protoplasts of ‘Bonanza’ navel orange [Citrus sinensis (L.) Osbeck] were electrically fused with leaf protoplasts isolated from ‘Chicken Heart’ Chinese wampee. After 8 months of culture, fusion products regenerated into shoots. More than 70% of the shoots unexpectedly rooted well. Chromosome counting of several shoot- and root-tips revealed that their chromosome numbers were not 2n=4x=36 as expected, but 2n=6x=54, suggesting that chromosome doubling occurred rather than chromosome elimination in this intertribal fusion combination. RAPD analysis of embryoids and the leaves of unrooted and rooted shoots verified their hybridity. This is the first report of hexaploid somatic hybrid plant regeneration from fusion between diploids in Aurantioideae.
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