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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Numerische Mathematik 41 (1983), S. 287-307 
    ISSN: 0945-3245
    Keywords: AMS (MOS): 30C30 ; 65R20:CR: 5.18
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary A numerical method, based on the integral equation formulation of Symm, is described for computing approximations to the mapping functions which accomplish the following conformal maps: (a) the mapping of a domain interior to a closed Jordan curve onto the interior of the unit disc, (b) the mapping of a domain exterior to a closed Jordan curve onto the exterior of the unit disc, (c) the mapping of a doubly-connected domain bounded by two closed Jordan curves onto a circular annulus. The numerical method is based on approximating the unknown source density by cubic splines and “singular” functions, and is particularly suited for the mapping of difficult domains having sharp corners.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0509
    Keywords: Esophagus, reflux ; Esophagus, motility ; Pharynx
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: A cricopharyngeal bar seen on barium fluoroscopy has been shown to be related to the presence of gastroesophageal reflux (GER). We investigated premature contraction of the cricopharyngeus (PCC) muscle, which may be a precursor of a fixed cricopharyngeal bar, to assess its significance in GER. Methods: The prevalence of PCC on barium swallow was recorded in three groups: (1) 83 patients with noncardiac chest pain who were investigated for possible GER; (2) 21 patients with severe GER undergoing fundoplication; and (3) 25 normal controls. Results: Group 1: PCC was observed in 42 of 77 with documented GER (54.5%), and in two of six patients without GER. Group 2: PCC was present in 11 of 21 fundoplication subjects. Group 3: PCC was seen in five of 25 normal controls. The incidence of PCC in patients with GER was statistically significantly higher than in normal subjects (p = 0.002). The sensitivity of the presence of PCC as a predictor of GER is only 0.54, but the specificity is 0.774, with a positive predictive value of 0.883. Conclusion: We conclude that observing premature cricopharyngeal contraction during the first swallows of an upper gastrointestinal (GI) study should direct attention to the possibility of GER.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Numerische Mathematik 37 (1981), S. 133-147 
    ISSN: 0945-3245
    Keywords: AMS(MOS): 30A28 ; CR: 5.18
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary We consider the integral equation method of Symm for the conformal mapping of simply-connected domains. For the numerical solution, we examine the use of spline functions of various degrees for the approximation of the source density σ. In particular, we consider ways for overcoming the difficulties associated with corner singularities. For this we modify the spline approximation and in the neighborhood of each corner, where a boundary singularity occurs, we approximate σ by a function which reflects the main singular behaviour of the source density. The singular functions are then blended with the splines, which approximate σ on the remainder of the boundary, so that the global approximating function has continuity of appropriate order at the transition points between the two types of approximation. We show, by means of numerical examples, that such approximations overcome the difficulties associated with corner singularities and lead to numerical results of high accuracy.
    Type of Medium: Electronic Resource
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