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  • mathematical programming  (3)
  • parameter optimization  (3)
  • Synapse development  (2)
  • Springer  (6)
  • American Geophysical Union (AGU)
  • 1975-1979  (6)
Collection
Keywords
Publisher
  • Springer  (6)
  • American Geophysical Union (AGU)
Years
  • 1975-1979  (6)
Year
  • 1
    Electronic Resource
    Electronic Resource
    An investigation of the foetal rat spinal cord (1975)
    Springer
    Cell & tissue research 158 (1975), S. 251-268 
    Details
    ISSN: 1432-0878
    Keywords: Synapse development ; Spinal cord ; Foetal rat-Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Electrophysiological and ultrastructural studies were carried out on foetal rat spinal cord. The electrophysiological observations allowed certain identification of the site of second order sensory neurones, regions of the most functionally mature ventral horn cells and the adequacy of reflex conduction at 18 days. In the ultrastructural studies we made use of these identifications. No definitive synapses were found at 13–14.5 days in dorsal and ventral horn neuropil though some possible precursors were seen. Immature axodendritic synapses are found first in both dorsal and ventral marginal zones at 14.5 days and in both dorsal and ventral neuropil regions at 15–16 days. At 17 days there is an abrupt increase in frequency and maturity of synaptic profiles in all regions; synapses containing pleomorphic populations of vesicles are first seen in the ventral horn neuropil at this age as rare axo-somatic synapses. At 18 days the synapses population increases and multiple contacts involving axons or dendrites commonly occur. Furthermore, axo-somatic synapses are seen for the first time in the dorsal horn. From 20 days onwards mature synapses were commonplace and all earlier stages can be found. In addition axo-dendritic synapses with pleomorphic populations of vesicles were first seen in the dorsal horn. Axo-somatic synapses in the dorsal horn remained immature in appearance at this time. These findings are discussed particularly in relationship to previous studies by others on the development of motility in the rat. It appears that in the rat lumbar cord, onset of formation of different synapse types in specific locations precedes the onset of possible related function by 1–2 days.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00219964
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  • 2
    Electronic Resource
    Electronic Resource
    An investigation of the foetal rat spinal cord (1975)
    Springer
    Cell & tissue research 158 (1975), S. 241-249 
    Details
    ISSN: 1432-0878
    Keywords: Synapse development ; Spinal cord ; Foetal rat ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ultrastructural studies on the foetal rat spinal cord show that during synaptogenesis there is difficulty in recognizing true synaptic precursors. Asymmetric densities are found at unusual sites forming, for example, somato-dendritic and somato-somatic junctions. They are also found between neurons and possible glial processes. Symmetric densities occur between nerve cells but may be confused with desmosomes. Profiles exhibiting membrane density, cleft material and 50 nm vesicles, which are the most reliable indicators of presumptive synapses, are found between neurones, but also at junctions between neurones and what may be glial processes. The picture is further confused by the presence of degenerating axodendritic synapses at early foetal stages. Caution must be exercised in defining an apparent synapse or precursor in foetal cord as that of a presumptive functional synapse because of the observed degenerating profiles and because to our knowledge, somato-somatic, somatodendritic, and neurono-glial synapses have not been observed in adult cord. It is not known whether these structures are an unwanted consequence of development or play a role in guiding development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00219963
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  • 3
    Electronic Resource
    Electronic Resource
    Solving the nonlinear least square problem: Application of a general method (1976)
    Springer
    Journal of optimization theory and applications 18 (1976), S. 469-483 
    Details
    ISSN: 1573-2878
    Keywords: Nonlinear least-square problems ; parameter optimization ; penalty function methods ; mathematical programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract An algorithm for solving the general nonlinear least-square problem is developed. An estimate for the Hessian matrix is constructed as the sum of two matrices. The first matrix is the usual first-order estimate used by the Gauss method, while the second matrix is generated recursively using a rank-one formula. Test results indicate that the method is superior to the standard Gauss method and compares favorably with other methods, especially for problems with nonzero residuals at the solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00932656
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  • 4
    Electronic Resource
    Electronic Resource
    An accelerated multiplier method for nonlinear programming (1977)
    Springer
    Journal of optimization theory and applications 21 (1977), S. 137-174 
    Details
    ISSN: 1573-2878
    Keywords: Augmented penalty function ; method of multipliers ; penalty function methods ; nonlinear programming ; mathematical programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper describes an accelerated multiplier method for solving the general nonlinear programming problem. The algorithm poses a sequence of unconstrained optimization problems. The unconstrained problems are solved using a rank-one recursive algorithm described in an earlier paper. Multiplier estimates are obtained by minimizing the error in the Kuhn-Tucker conditions using a quadratic programming algorithm. The convergence of the sequence of unconstrained problems is accelerated by using a Newton-Raphson extrapolation process. The numerical effectiveness of the algorithm is demonstrated on a relatively large set of test problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00932517
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  • 5
    Electronic Resource
    Electronic Resource
    A gradient projection-multiplier method for nonlinear programming (1978)
    Springer
    Journal of optimization theory and applications 24 (1978), S. 523-548 
    Details
    ISSN: 1573-2878
    Keywords: Multiplier method ; gradient projection method ; penalty function methods ; nonlinear programming ; parameter optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper describes a gradient projection-multiplier method for solving the general nonlinear programming problem. The algorithm poses a sequence of unconstrained optimization problems which are solved using a new projection-like formula to define the search directions. The unconstrained minimization of the augmented objective function determines points where the gradient of the Lagrangian function is zero. Points satisfying the constraints are located by applying an unconstrained algorithm to a penalty function. New estimates of the Lagrange multipliers and basis constraints are made at points satisfying either a Lagrangian condition or a constraint satisfaction condition. The penalty weight is increased only to prevent cycling. The numerical effectiveness of the algorithm is demonstrated on a set of test problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00935298
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  • 6
    Electronic Resource
    Electronic Resource
    An improved penalty function method for solving constrained parameter optimization problems (1975)
    Springer
    Journal of optimization theory and applications 16 (1975), S. 1-24 
    Details
    ISSN: 1573-2878
    Keywords: Penalty-function methods ; mathematical programming ; nonlinear programming ; pseudo Newton-Raphson methods ; parameter optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract An effective algorithm is described for solving the general constrained parameter optimization problem. The method is quasi-second-order and requires only function and gradient information. An exterior point penalty function method is used to transform the constrained problem into a sequence of unconstrained problems. The penalty weightr is chosen as a function of the pointx such that the sequence of optimization problems is computationally easy. A rank-one optimization algorithm is developed that takes advantage of the special properties of the augmented performance index. The optimization algorithm accounts for the usual difficulties associated with discontinuous second derivatives of the augmented index. Finite convergence is exhibited for a quadratic performance index with linear constraints; accelerated convergence is demonstrated for nonquadratic indices and nonlinear constraints. A computer program has been written to implement the algorithm and its performance is illustrated in fourteen test problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00935620
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