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  • 1995-1999  (4)
  • 2-norm  (1)
  • Colon  (1)
  • Householder transformation  (1)
  • Innervation  (1)
  • Intrapancreatic neuron  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Diseases of the colon & rectum 38 (1995), S. 509-513 
    ISSN: 1530-0358
    Keywords: Colon ; Innervation ; Nerves ; Muscle ; Immunohistochemistry ; Constipation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract PURPOSE: This study was designed to investigate neural and muscular features of the colonic wall in patients with severe idiopathic constipation. METHODS: By using quantitative immunohistochemistry, resected specimens from 14 patients with idiopathic chronic constipation and 17 nonobstructed cancer controls were studied. RESULTS: Routine histology revealed no significant histologic abnormality throughout the colon apart from four cases of melanosis coli. Ratio of the thickness of circular to longitudinal muscle was significantly lower in the left colon in constipated subjects. The myenteric plexus appeared morphologically normal in all subjects. S-100 protein, which stains neuronal supporting tissues, demonstrated an increase in the proportion of neural tissue in the myenteric plexus. There was an increased number of PGP-9.5 immunoreactive nerve fibers in the muscularis propria in constipated patients, and this was significantly higher in the ascending and descending colon. CONCLUSION: Intractably constipated patients have alterations in the neural composition of the colonic myenteric plexus and innervation of the circular muscle.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    BIT 36 (1996), S. 166-181 
    ISSN: 1572-9125
    Keywords: QR decomposition downdating ; Gram-Schmidt downdating algorithm ; Householder transformation ; least squares problems ; modified Gram-Schmidt algorithm ; reorthogonalization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A new algorithm for downdating a QR decomposition is presented. We show that, when the columns in the Q factor from the Modified Gram-Schmidt QR decomposition of a matrixX are exactly orthonormal, the Gram-Schmidt downdating algorithm for the QR decomposition ofX is equivalent to downdating the full Householder QR decomposition of the matrixX augmented by ann ×n zero matrix on top. Using this relation, we derive an algorithm that improves the Gram-Schmidt downdating algorithm when the columns in the Q factor are not orthonormal. Numerical test results show that the new algorithm produces far more accurate results than the Gram-Schmidt downdating algorithm for certain ill-conditioned problems.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    BIT 39 (1999), S. 757-779 
    ISSN: 1572-9125
    Keywords: Overdetermined linear systems ; rank reduction ; Hankel structure ; Toeplitz structure ; structured total least norm ; total least squares ; 1-norm ; 2-norm ; singular value decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The structure preserving rank reduction problem arises in many important applications. The singular value decomposition (SVD), while giving the closest low rank approximation to a given matrix in matrix L 2 norm and Frobenius norm, may not be appropriate for these applications since it does not preserve the given structure. We present a new method for structure preserving low rank approximation of a matrix, which is based on Structured Total Least Norm (STLN). The STLN is an efficient method for obtaining an approximate solution to an overdetermined linear system AX ≈ B, preserving the given linear structure in the perturbation [E F] such that (A + E)X = B + F. The approximate solution can be obtained to minimize the perturbation [E F] in the L p norm, where p = 1, 2, or ∞. An algorithm is described for Hankel structure preserving low rank approximation using STLN with L p norm. Computational results are presented, which show performances of the STLN based method for L 1 and L 2 norms for reduced rank approximation for Hankel matrices.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2013
    Keywords: Key words Cholecystokinin ; Cysteamine ; Intrapancreatic neuron ; Islets ; Pancreatic secretion ; Pertussis toxin ; Somatostatin ; Somatostatin antagonist
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The role of intrapancreatic neurons in the action of cholecystokinin (CCK) on pancreatic exocrine secretion of the totally isolated, perfused rat pancreas was investigated. Intrapancreatic neurons were activated by applying electrical field stimulation (EFS) to the isolated pancreas for 45 min. When applying EFS, spontaneous pancreatic secretions of fluid and amylase increased until the second 15-min period of EFS and then decreased during the third 15-min period. Atropine (2 µM) notably reduced the EFS-evoked pancreatic secretions of fluid and amylase. The CCK-induced (10 pM) pancreatic secretions of fluid and amylase elevated further in the first 15-min period of EFS and then gradually resumed to the levels observed during application of CCK alone in the third 15-min period of EFS. However, the CCK-induced pancreatic secretions remained elevated even in the third 15-min period of EFS when an action of endogenous somatostatin was inhibited by cyclo-(7-aminoheptanonyl-Phe-d-Trp-Lys-Thr[BZL]) (10 nM) or pertussis toxin (200 ng/ml). EFS further elevated spontaneous exocrine secretion by the cysteamine-treated (300 mg/kg) pancreas, but this was markedly reduced, to normal levels, by infusing somatostatin (100 pM). EFS increased the numbers of immunoreactive somatostatin cells in the Langerhans’ islets. The results indicate that intrapancreatic neuronal activation influences CCK-induced pancreatic secretions in a dual-phase pattern in the rat: an increase during the early phase and a decrease during the late phase. Endogenous somatostatin released from the islets appears to inhibit the enhancing effect of neuronal activation on CCK-induced pancreatic secretion. Of the intrapancreatic neurons, the cholinergic ones appear to predominate in EFS’s effects on CCK-induced pancreatic secretion.
    Type of Medium: Electronic Resource
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