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  • Jagers, Peter, 1941- (författare)
  • Matematikens ord
  • 2009
  • Ingår i: LexicoNordica. ; 16, s. 315-318
  • Tidskriftsartikel (refereegranskat)
  • Mishchenko, Kateryna, et al. (författare)
  • Assessing a multiple QTL search using the variance component model
  • 2010
  • Ingår i: Computational biology and chemistry (Print). - 1476-9271. ; 34, s. 34-41
  • Tidskriftsartikel (refereegranskat)abstract
    • Development of variance component algorithms in genetics has previously mainly focused on animal breeding models or problems in human genetics with a simple data structure. We study alternative methods for constrained likelihood maximization in quantitative trait loci (QTL) analysis for large complex pedigrees. We apply a forward selection scheme to include several QTL and interaction effects, as well as polygenic effects, with up to five variance components in the model. We show that the implemented active set and primal-dual schemes result in accurate solutions and that they are robust. In terms of computational speed, a comparison of two approaches for approximating the Hessian of the log-likelihood shows that the method using an average information matrix is the method of choice for the five-dimensional problem. The active set method, with the average information method for Hessian computation, exhibits the fastest convergence with an average of 20 iterations per tested position, where the change in variance components <0.0001 was used as convergence criterion.
  • Freij, Ragnar, 1984-, et al. (författare)
  • Partially ordered secretaries
  • 2010
  • Ingår i: Electronic Communications in Probability. - 1083-589X. ; 15, s. 504-507
  • Tidskriftsartikel (refereegranskat)abstract
    • The elements of a finite nonempty partially ordered set are exposed at independent uniform times in [0, 1] to a selector who, at any given time, can see the structure of the induced partial order on the exposed elements. The selector’s task is to choose online a maximal element. This generalizes the classical linear order secretary problem, for which it is known that the selector can succeed with probability 1=e and that this is best possible. We describe a strategy for the general problem that achieves success probability at least 1=e for an arbitrary partial order.
  • Jagers, Peter, 1941- (författare)
  • A plea for stochastic population dynamics
  • 2010
  • Ingår i: Journal of Mathematical Biology. - 0303-6812. ; 60:5, s. 761-764
  • Tidskriftsartikel (refereegranskat)abstract
    • It is argued that biological populations are finite and consisting of individuals with varying life span and reproduction, and that they should be thus modelled. Modern probability theory provides tools for this.
  • Otani, Hiroki, et al. (författare)
  • Morphometric study on the characteristic external features of normal and abnormal human embryos
  • 2008
  • Ingår i: Congenit Anom Kyoto. ; 48:1, s. 18-28
  • Tidskriftsartikel (refereegranskat)abstract
    • The embryonic period is characterized by organogenesis and accompanying dynamic changes in external features. The measurement of human embryos has been limited to whole body dimensions, such as crown-rump length. More detailed measurements would add quantitative information about these characteristic events and provide a better understanding of normal and abnormal embryonic development. In the present study, we defined axes, landmarks, and measurements for human embryos, and measured 250 externally normal human embryos at Carnegie stages 14-23 (6.5-29.3 mm in crown-rump length, approximately 5-8 weeks of estimated ovulation age) that were fixed in Bouin's solution and preserved in 10% formalin solution. The axes, landmarks, and measurements defined for human embryos are corresponding to those in human and primate fetuses. The whole body, head, face, and extremities were measured using a scale attached to a dissecting microscope. Axial length, head height plus ear-shoulder length plus trunk height, was designated as a new measurement of the whole body, which is comparable with crown-rump length. Approximate standards of these measurements were obtained. The ratios of some measurements to trunk height and between the different parts were also obtained, and several different developmental patterns were recognized. The reproducibility of each measurement was evaluated by measuring 50 specimens three times each at intervals of one or two months. As a pilot study for the application of the proposed measurements, 84 human embryos with external anomalies, including holoprosencephaly, anomalies of extremities, and pharyngeal arch anomalies, were measured using the same method, and a few tendencies characteristic to holoprosencephaly were noticed.
  • Heintz, Alexey, 1955-, et al. (författare)
  • A convolution thresholding scheme for the Willmore flow
  • 2008
  • Ingår i: Interfaces and Free Boundaries. - 1463-9971. ; 10:2, s. 139-153
  • Tidskriftsartikel (refereegranskat)abstract
    • A convolution thresholding scheme fro geometric Willmore flows is suggested and the consistency is proved.
  • Lundh, Torbjörn, 1965-, et al. (författare)
  • Cross- and triple-ratios of human body parts during development
  • 2011
  • Ingår i: Anatomical Records. - 1932-8486. ; 294, s. 1360-1369
  • Tidskriftsartikel (refereegranskat)abstract
    • Recently developed landmark-based geometric morphometry has been used to depict the morphological development of organisms. In geometry,four landmarks can be mapped to any other four by Mo¨bius transformations,if the cross-ratio of the landmarks is invariant and vice versa. To geometrically analyze the morphological development of the human body, we examined the cross-ratio of three consecutive body parts that are segmented by four landmarks in their configuration. Moreover, we introduced the triple-ratio of five landmarks that segments four consecutive parts (e.g., the shoulder, upper arm, forearm, and hand) and examined their growth patterns. The cross- and triple-ratios of the upper limb and shoulder girdle in fetuses were constant when biomechanical landmarks were used, although the cross-ratio of the upper limb varied when anatomical landmarks were used. The cross-ratios of the lower limbs, trunk,and pelvic girdles in fetuses differed from their corresponding cross-ratios in adults. These results suggest Mo¨bius growth in the fetal upper limb and shoulder girdle but not in the other body parts examined. However, the growth balance of the three contiguous body parts was represented by the developmental change in the cross-ratio. Therefore, the cross- and triple-ratios may be applicable for simple but significant assessments of growth balance or proportion of the body parts. Anat Rec, 294:1360–1369, 2011.
  • Dahl, Ingolf, 1950- (författare)
  • Mathematica package Obtuse
  • 2010
  • Annan publikation (övrigt vetenskapligt)abstract
    • This Mathematica package (freeware) contains routines and tools for obtuse angle shadowing networks and distance-based interpolation between scattered, multidimensional points. Four variants of distance-based interpolation can be compared with (coordinate-based) 2D Delaunay interpolation.
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