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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Algorithmica 4 (1989), S. 77-96 
    ISSN: 1432-0541
    Keywords: Computational geometry ; Modified pruning technique ; LinearL 1 approximation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this paper we present a linear-time algorithm for approximating a set ofn points by a linear function, or a line, that minimizes theL 1 norm. The algorithmic complexity of this problem appears not to have been investigated, although anO(n 3) naive algorithm can be easily obtained based on some simple characteristics of an optimumL 1 solution. Our linear-time algorithm is optimal within a constant factor and enables us to use linearL 1 approximation of many points in practice. The complexity ofL 1 linear approximation of a piecewise linear function is also touched upon.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0878
    Keywords: Key words Pepsinogen C ; Ontogeny ; Mucous neck cell ; Chief cell ; Intermediate mucopeptic cell ; Immunocytochemistry ; In situ hybridization ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The ontogeny of pepsinogen C-producing cells in rat fundic glands was studied by means of light and electron microscopy using an antiserum raised against a synthetic peptide based on rat pepsinogen C. To confirm the immunocytochemistry results, the expression of rat pepsinogen C messenger RNA (mRNA) in the fundic gland was also examined by in situ hybridization using a digoxigenin-labeled RNA probe. In adult rats, pepsinogen C was produced by chief cells, mucous neck cells, and intermediate mucopeptic cells. Pepsinogen C-producing cells appeared in embryos as early as 18.5 days’ gestation. The development of these cells could be classified into four stages: (1) 18.5 days’ gestation to 0.5 days after birth; (2) 0.5 days to 2 weeks after birth; (3) 3–4 weeks after birth; (4) 4–8 weeks after birth. In embryos and young animals, pepsinogen C-producing cells were mucopeptic cells. By 4 weeks after birth, mucous neck cells could be distinguished morphologically. The maturation stages of the chief cells could be traced by electron microscopy along the longitudinal axis of the rat fundic gland by double-staining with anti-pepsinogen C antibody and periodic acid-thiocarbohydrazide-silver proteinate. Positive reactions for pepsinogen C and pepsinogen C mRNA expression were detected in mucous neck cells. Therefore, we conclude that mucous neck cells are precursor cells of chief cells. Mucous neck cells, intermediate cells, and chief cells are in the same differentiating cell lineage.
    Type of Medium: Electronic Resource
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