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  • 1
    Electronic Resource
    Electronic Resource
    Unbiased Estimates of Circle Parameters (2000)
    Springer
    Journal of optimization theory and applications 106 (2000), S. 49-60 
    Details
    ISSN: 1573-2878
    Keywords: Circle fitting ; instrumental variables ; Fisher scoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract It is of practical value to estimate the center and radius of a circle from a given set of noisy coordinate measurements. Since the coordinates of the points on a circle relate to its parameters through the nonlinear circle equation, the estimation problem is inherently nonlinear. Additionally, if the measurements are available only along a small arc, the estimation exhibits generally a bias, together with large variances, even at low-noise magnitudes. This paper presents two algorithms, one iterative and another which has a closed-form solution, aiming at the elimination of biases that occur at small arcs. Simulation results show that the two algorithms do provide unbiased and reliable estimates of the circle parameters for noisy measurements on arcs as small as 45°.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004603023018
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of C677T mutation of methylene tetrahydrofolate reductase gene and plasma folate level on hyperhomocysteinemia in patients with meningomyelocele (2000)
    Springer
    Child's nervous system 16 (2000), S. 559-563 
    Details
    ISSN: 1433-0350
    Keywords: Keywords Meningomyelocele ; Methylenetetrahydrofolate reductase (MTHFR) ; Folate ; Homocysteine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  To evaluate the relationship between genotypes of methylene tetrahydrofolate reductase (MTHFR), and plasma folate and homocysteine (Hcy) levels in meningomyelocele, 21 Korean patients, 47 of their family members, and 43 healthy controls were recruited. The presence of C677T mutation in the MTHFR gene and plasma concentrations of folate/Hcy were investigated. The genotype frequency of C677T mutation was not higher in study groups (patients and family members). The plasma folate concentration showed no difference either between the study and the control groups or among MTHFR-genotypic groups. The plasma Hcy concentration in homozygotes in the study group was higher than that in the control group, and higher than that in heterozygotes when plasma folate levels were low (P=0.006). Although neither MTHFR genotype nor plasma folate/Hcy level plays a definite part on its own, they seem to have an additive effect on the occurrence of meningomyelocele. Our results support folate supplementation for the prevention of hyperhomo- cysteinemia and meningomyelocele.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00007298
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    Paper (German National Licenses)
    Fulltext
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