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  • Articles  (13,372)
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  • 1
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    Mathematical programming 68 (1995), S. 105-130 
    ISSN: 1436-4646
    Keywords: primary 49B34 ; secondary 90C31 ; 93C30 ; Variational inequalities ; Sensitivity analysis ; Generalized Jacobian
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Optimization problems with variational inequality constraints are converted to constrained minimization of a local Lipschitz function. To this minimization a non-differentiable optimization method is used; the required subgradients of the objective are computed by means of a special adjoint equation. Besides tests with some academic examples, the approach is applied to the computation of the Stackelberg—Cournot—Nash equilibria and to the numerical solution of a class of quasi-variational inequalities.
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  • 2
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    Mathematical programming 69 (1995), S. 1-43 
    ISSN: 1436-4646
    Keywords: Mathematical programming ; Cutting planes ; Analytic center
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Anoracle for a convex setS ⊂ ℝ n accepts as input any pointz in ℝ n , and ifz ∈S, then it returns ‘yes’, while ifz ∉S, then it returns ‘no’ along with a separating hyperplane. We give a new algorithm that finds a feasible point inS in cases where an oracle is available. Our algorithm uses the analytic center of a polytope as test point, and successively modifies the polytope with the separating hyperplanes returned by the oracle. The key to establishing convergence is that hyperplanes judged to be ‘unimportant’ are pruned from the polytope. If a ball of radius 2−L is contained inS, andS is contained in a cube of side 2 L+1, then we can show our algorithm converges after O(nL 2) iterations and performs a total of O(n 4 L 3+TnL 2) arithmetic operations, whereT is the number of arithmetic operations required for a call to the oracle. The bound is independent of the number of hyperplanes generated in the algorithm. An important application in which an oracle is available is minimizing a convex function overS.
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  • 3
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    Mathematical programming 69 (1995), S. 45-73 
    ISSN: 1436-4646
    Keywords: Cutting plane ; Stochastic programming ; Analytic center ; Interior-point method
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    Topics: Computer Science , Mathematics
    Notes: Abstract The stochastic linear programming problem with recourse has a dual block-angular structure. It can thus be handled by Benders' decomposition or by Kelley's method of cutting planes; equivalently the dual problem has a primal block-angular structure and can be handled by Dantzig-Wolfe decomposition—the two approaches are in fact identical by duality. Here we shall investigate the use of the method of cutting planes from analytic centers applied to similar formulations. The only significant difference form the aforementioned methods is that new cutting planes (or columns, by duality) will be generated not from the optimum of the linear programming relaxation, but from the analytic center of the set of localization.
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  • 4
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    Mathematical programming 69 (1995), S. 237-253 
    ISSN: 1436-4646
    Keywords: Variational inequality ; Nonlinear complementarity ; Nonlinear programming ; Continuation method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract This paper presents a continuation method for monotone variational inequality problems based on a new smooth equation formulation. The existence, uniqueness and limiting behavior of the path generated by the method are analyzed.
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  • 5
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    Mathematical programming 69 (1995), S. 269-309 
    ISSN: 1436-4646
    Keywords: Quadratic programming ; Submodular constraints ; Kuhn-Tucker conditions ; Lexicographically optimal flow ; Parametric maximum flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We present new strongly polynomial algorithms for special cases of convex separable quadratic minimization over submodular constraints. The main results are: an O(NM log(N 2/M)) algorithm for the problemNetwork defined on a network onM arcs andN nodes; an O(n logn) algorithm for thetree problem onn variables; an O(n logn) algorithm for theNested problem, and a linear time algorithm for theGeneralized Upper Bound problem. These algorithms are the best known so far for these problems. The status of the general problem and open questions are presented as well.
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  • 6
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    Mathematical programming 69 (1995), S. 335-349 
    ISSN: 1436-4646
    Keywords: Polyhedral combinatorics ; Valid inequalities ; Travelling salesman ; Worst-case analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We consider most of the known classes of valid inequalities for the graphical travelling salesman polyhedron and compute the worst-case improvement resulting from their addition to the subtour polyhedron. For example, we show that the comb inequalities cannot improve the subtour bound by a factor greater than 10/9. The corresponding factor for the class of clique tree inequalities is 8/7, while it is 4/3 for the path configuration inequalities.
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  • 7
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    Mathematical programming 70 (1995), S. 1-16 
    ISSN: 1436-4646
    Keywords: Stochastic programming ; Polyhedral functions ; Simplicial functions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract A dual method is presented to solve a linearly constrained optimization problem with convex, polyhedral objective function, along with a fast bounding technique, for the optimum value. The method can be used to solve problems, obtained from LPs, where some of the constraints are not required to be exactly satisfied but are penalized by piecewise linear functions, which are added to the objective function of the original problem. The method generalizes an earlier solution technique developed by Prékopa (1990). Applications to stochastic programming are also presented.
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  • 8
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    Mathematical programming 70 (1995), S. 107-122 
    ISSN: 1436-4646
    Keywords: Linear complementarity problem ; Predictor—corrector algorithm ; Complexity analysis ; Central trajectory ; Curvature integral ; Interior-point methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this paper, we propose a predictor—corrector-type algorithm for solving the linear complementarity problem (LCP), and prove that the actual number of iterations needed by the algorithm is bounded from above and from below by a curvature integral along the central trajectory of the problem. This curvature integral is not greater than, and possibly smaller than, the best upper bound obtained in the literature to date.
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  • 9
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    Mathematical programming 70 (1995), S. 159-172 
    ISSN: 1436-4646
    Keywords: Parametric nonlinear programming ; Directional differentiability ; B-derivative ; Piecewise smooth function ; Nonunique multipliers ; Degeneracy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Consider a parametric nonlinear optimization problem subject to equality and inequality constraints. Conditions under which a locally optimal solution exists and depends in a continuous way on the parameter are well known. We show, under the additional assumption of constant rank of the active constraint gradients, that the optimal solution is actually piecewise smooth, hence B-differentiable. We show, for the first time to our knowledge, a practical application of quadratic programming to calculate the directional derivative in the case when the optimal multipliers are not unique.
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  • 10
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    Mathematical programming 70 (1995), S. 191-200 
    ISSN: 1436-4646
    Keywords: Strictly pseudomonotone map ; Z-map ; Complementarity problem ; Least element problem
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    Topics: Computer Science , Mathematics
    Notes: Abstract Strictly pseudomonotoneZ-maps operating on Banach lattices are considered. Equivalence of complementarity problems and least-element problems is established under certain regularity and growth conditions. This extends a recent result by Riddell (1981) for strictly monotoneZ-maps to the pseudomonotone case. Some other problems equivalent to the above are discussed as well.
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  • 11
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    Mathematical programming 70 (1995), S. 251-277 
    ISSN: 1436-4646
    Keywords: Linear programming ; Barrier methods ; Interior-point methods
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    Topics: Computer Science , Mathematics
    Notes: Abstract Many interior-point methods for linear programming are based on the properties of the logarithmic barrier function. After a preliminary discussion of the convergence of the (primal) projected Newton barrier method, three types of barrier method are analyzed. These methods may be categorized as primal, dual and primal—dual, and may be derived from the application of Newton's method to different variants of the same system of nonlinear equations. A fourth variant of the same equations leads to a new primal—dual method. In each of the methods discussed, convergence is demonstrated without the need for a nondegeneracy assumption or a transformation that makes the provision of a feasible point trivial. In particular, convergence is established for a primal—dual algorithm that allows a different step in the primal and dual variables and does not require primal and dual feasibility. Finally, a new method for treating free variables is proposed.
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  • 12
    ISSN: 1436-4646
    Keywords: Linear programming ; Mixed-integer programming ; Large-scale optimization ; Airline fleet assignment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Given a flight schedule and set of aircraft, the fleet assignment problem is to determine which type of aircraft should fly each flight segment. This paper describes a basic daily, domestic fleet assignment problem and then presents chronologically the steps taken to solve it efficiently. Our model of the fleet assignment problem is a large multi-commodity flow problem with side constraints defined on a time-expanded network. These problems are often severely degenerate, which leads to poor performance of standard linear programming techniques. Also, the large number of integer variables can make finding optimal integer solutions difficult and time-consuming. The methods used to attack this problem include an interior-point algorithm, dual steepest edge simplex, cost perturbation, model aggregation, branching on set-partitioning constraints and prioritizing the order of branching. The computational results show that the algorithm finds solutions with a maximum optimality gap of 0.02% and is more than two orders of magnitude faster than using default options of a standard LP-based branch-and-bound code.
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  • 13
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    Mathematical programming 71 (1995), S. 77-100 
    ISSN: 1436-4646
    Keywords: Convex linearly constrained problems ; Variational inequalities ; Interior methods ; Entropy-like proximal method ; Maximal monotone operator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this paper, an entropy-like proximal method for the minimization of a convex function subject to positivity constraints is extended to an interior algorithm in two directions. First, to general linearly constrained convex minimization problems and second, to variational inequalities on polyhedra. For linear programming, numerical results are presented and quadratic convergence is established.
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  • 14
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    Mathematical programming 71 (1995), S. 29-50 
    ISSN: 1436-4646
    Keywords: Max-cut ; Cut polytope ; Metric polytope ; Linear relaxation ; One-third-integrality ; Box one-third-integrality ; Forbidden minor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Given a graphG = (V, E), the metric polytopeS (G) is defined by the inequalitiesx(F) − x(C∖F) ⩽ |F| − 1 for $$F \subseteq C$$ , |F| odd,C cycle ofG, and 0 ⩽x e ⩽ 1 fore ∈ E. Optimization overS (G) provides an approximation for the max-cut problem. The graphG is called 1/d-integral if all the vertices ofS(G) have their coordinates in{i/d ∣ 0 ⩽ i ⩽ d}. We prove that the class of 1/d-integral graphs is closed under minors, and we present several minimal forbidden minors for 1/3-integrality. In particular, we characterize the 1/3-integral graphs on seven nodes. We study several operations preserving 1/d-integrality, in particular, thek-sum operation for 0 ⩽k ⩽ 3. We prove that series parallel graphs are characterized by the following stronger property. All vertices of the polytopeS (G) ∩ {x ∣ ℓ ⩽ x ⩽ u} are 1/3-integral for every choice of 1/3-integral boundsℓ, u on the edges ofG.
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  • 15
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    Mathematical programming 71 (1995), S. 101-112 
    ISSN: 1436-4646
    Keywords: Minmax ; Maximal covering problems ; Multi criteria decision-making
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this paper we introduce the parametric minquantile problem, a weighted generalisation ofkth maximum minimisation. It is shown that, under suitable quasiconvexity assumptions, its resolution can be reduced to solving a polynomial number of minmax problems. It is also shown how this simultaneously solves (parametric) maximal covering problems. It follows that bicriteria problems, where the aim is to both maximize the covering and minimize the cover-level, are reducible to a discrete problem, on which any multiple criteria method may be applied.
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  • 16
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    Mathematical programming 71 (1995), S. 71-76 
    ISSN: 1436-4646
    Keywords: Location theory ; Fermat—Weber problem ; Weiszfeld's iterative algorithm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The Fermat—Weber location problem requires finding a point in ℝ N that minimizes the sum of weighted Euclidean distances tom given points. A one-point iterative method was first introduced by Weiszfeld in 1937 to solve this problem. Since then several research articles have been published on the method and generalizations thereof. Global convergence of Weiszfeld's algorithm was proven in a seminal paper by Kuhn in 1973. However, since them given points are singular points of the iteration functions, convergence is conditional on none of the iterates coinciding with one of the given points. In addressing this problem, Kuhn concluded that whenever them given points are not collinear, Weiszfeld's algorithm will converge to the unique optimal solution except for a denumerable set of starting points. As late as 1989, Chandrasekaran and Tamir demonstrated with counter-examples that convergence may not occur for continuous sets of starting points when the given points are contained in an affine subspace of ℝ N . We resolve this open question by proving that Weiszfeld's algorithm converges to the unique optimal solution for all but a denumerable set of starting points if, and only if, the convex hull of the given points is of dimensionN.
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  • 17
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    Mathematical programming 71 (1995), S. 153-177 
    ISSN: 1436-4646
    Keywords: Network optimization ; Assignment problem ; Algorithms ; Experimental evaluation ; Cost scaling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The cost scaling push-relabel method has been shown to be efficient for solving minimum-cost flow problems. In this paper we apply the method to the assignment problem and investigate implementations of the method that take advantage of assignment's special structure. The results show that the method is very promising for practical use.
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  • 18
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    Mathematical programming 71 (1995), S. 195-206 
    ISSN: 1436-4646
    Keywords: Superfluous matrix ; Linear complementarity problem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Superfluous matrices were introduced by Howe (1983) in linear complementarity. In general, producing examples of this class is tedious (a few examples can be found in Chapter 6 of Cottle, Pang and Stone (1992)). To overcome this problem, we define a new class of matrices $$\bar Z$$ and establish that in $$\bar Z$$ superfluous matrices of any ordern ⩾ 4 can easily be constructed. For every integerk, an example of a superfluous matrix of degreek is exhibited in the end.
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    Mathematical programming 71 (1995), S. 249-258 
    ISSN: 1436-4646
    Keywords: Combinatorial optimization ; Integrality of polyhedra ; Generalized set packing ; Covering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract A 0, ±1-matrixA is balanced if, in every submatrix with two nonzero entries per row and column, the sum of the entries is a multiple of four. This definition was introduced by Truemper (1978) and generalizes the notion of a balanced 0, 1-matrix introduced by Berge (1970). In this paper, we extend a bicoloring theorem of Berge (1970) and total dual integrality results of Fulkerson, Hoffman and Oppenheim (1974) to balanced 0, ±1-matrices.
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    Mathematical programming 71 (1995), S. 369-370 
    ISSN: 1436-4646
    Keywords: Local Lipschitz property ; Infinite-dimensional Hilbert space
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract An oversight in a paper of Correa and Lemaréchal (this journal, 1993) is noted; a counterexample is given.
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    Mathematical programming 70 (1995), S. 27-45 
    ISSN: 1436-4646
    Keywords: Convex polytopes ; Enumeration of faces ; Adjacency ; Segments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We introduce the concept of a segment of a degenerate convex polytope specified by a system of linear constraints, and explain its importance in developing algorithms for enumerating the faces. Using segments, we describe an algorithm that enumerates all the faces, in time polynomial in their number. The role of segments in the unsolved problem of enumerating the extreme points of a convex polytope specified by a degenerate system of linear constraints, in time polynomial in the number of extreme points, is discussed.
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    Mathematical programming 70 (1995), S. 47-72 
    ISSN: 1436-4646
    Keywords: Bilevel programming ; Nonlinear nonconvex ; Nondifferentiable optimization ; Economic planning ; Sensitivity analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract This paper is concerned with general nonlinear nonconvex bilevel programming problems (BLPP). We derive necessary and sufficient conditions at a local solution and investigate the stability and sensitivity analysis at a local solution in the BLPP. We then explore an approach in which a bundle method is used in the upper-level problem with subgradient information from the lower-level problem. Two algorithms are proposed to solve the general nonlinear BLPP and are shown to converge to regular points of the BLPP under appropriate conditions. The theoretical analysis conducted in this paper seems to indicate that a sensitivity-based approach is rather promising for solving general nonlinear BLPP.
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    Mathematical programming 70 (1995), S. 123-148 
    ISSN: 1436-4646
    Keywords: Generalized equations ; Variational inequalities ; Nonlinear programming ; Sensitivity analysis ; Power series ; Strong regularity ; Constrained optimization ; Perturbation theory
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    Notes: Abstract We show that the solution of a strongly regular generalized equation subject to a scalar perturbation expands in pseudopower series in terms of the perturbation parameter, i.e., the expansion of orderk is the solution of generalized equations expanded to orderk and thus depends itself on the perturbation parameter. In the polyhedral case, this expansion reduces to a usual Taylor expansion. These results are applied to the problem of regular perturbation in constrained optimization. We show that, if the strong regularity condition is satisfied, the property of quadratic growth holds and, at least locally, the solutions of the optimization problem and of the associated optimality system coincide. If, in addition the number of inequality constraints is finite, the solution and the Lagrange multiplier can be expanded in Taylor series. If the data are analytic, the solution and the multiplier are analytic functions of the perturbation parameter.
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    Mathematical programming 70 (1995), S. 201-209 
    ISSN: 1436-4646
    Keywords: Disjoint paths ; Joins ; Packing cuts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Seymour (1981) proved that the cut criterion is necessary and sufficient for the solvability of the edge-disjoint paths problem when the union of the supply graph and the demand graph is planar and Eulerian. When only planarity is required, Middendorf and Pfeiffer (1993) proved the problem to be NP-complete. For this case, Korach and Penn (1992) proved that the cut criterion is sufficient for the existence of a near-complete packing of paths. Here we generalize this result by showing how a natural strengthening of the cut criterion yields better packings of paths. Analogously to Seymour's approach, we actually prove a theorem on packing cuts in an arbitrary graph and then the planar edge-disjoint paths case is obtained by planar dualization. The main result is derived from a theorem of Sebő (1990) on the structure of ±1 weightings of a bipartite graph with no negative circuits.
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    Mathematical programming 70 (1995), S. 279-351 
    ISSN: 1436-4646
    Keywords: Linear programming ; Complexity theory ; Interior-point methods ; Semi-definite programming ; Condition numbers ; Convex programming
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    Notes: Abstract We propose analyzing interior-point methods using notions of problem-instance size which are direct generalizations of the condition number of a matrix. The notions pertain to linear programming quite generally; the underlying vector spaces are not required to be finite-dimensional and, more importantly, the cones defining nonnegativity are not required to be polyhedral. Thus, for example, the notions are appropriate in the context of semi-definite programming. We prove various theorems to demonstrate how the notions can be used in analyzing interior-point methods. These theorems assume little more than that the interiors of the cones (defining nonnegativity) are the domains of self-concordant barrier functions.
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    Mathematical programming 71 (1995), S. 17-28 
    ISSN: 1436-4646
    Keywords: Descent method ; Proximal algorithm ; Direction-finding subproblem
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Most of the descent methods developed so far suffer from the computational burden due to a sequence of constrained quadratic subproblems which are needed to obtain a descent direction. In this paper we present a class of proximal-type descent methods with a new direction-finding subproblem. Especially, two of them have a linear programming subproblem instead of a quadratic subproblem. Computational experience of these two methods has been performed on two well-known test problems. The results show that these methods are another very promising approach for nondifferentiable convex optimization.
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    Mathematical programming 71 (1995), S. 51-69 
    ISSN: 1436-4646
    Keywords: Smoothing ; Convex inequalities ; Linear complementarity
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    Notes: Abstract A smooth approximationp (x, α) to the plus function max{x, 0} is obtained by integrating the sigmoid function 1/(1 + e−αx ), commonly used in neural networks. By means of this approximation, linear and convex inequalities are converted into smooth, convex unconstrained minimization problems, the solution of which approximates the solution of the original problem to a high degree of accuracy forα sufficiently large. In the special case when a Slater constraint qualification is satisfied, an exact solution can be obtained for finiteα. Speedup over MINOS 5.4 was as high as 1142 times for linear inequalities of size 2000 × 1000, and 580 times for convex inequalities with 400 variables. Linear complementarity problems are converted into a system of smooth nonlinear equations and are solved by a quadratically convergent Newton method. For monotone LCPs with as many as 10 000 variables, the proposed approach was as much as 63 times faster than Lemke's method.
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    Mathematical programming 71 (1995), S. 127-136 
    ISSN: 1436-4646
    Keywords: Parametric optimization ; Mixed-integer program ; Value functions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We identify a class of formulas computable in polynomial time such that the functions defined by these formulas are precisely the value functions of mixed-integer programs with rational constraint coefficients.
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    Mathematical programming 71 (1995), S. 137-151 
    ISSN: 1436-4646
    Keywords: Quadratic assignment problem ; Lower bounds
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract We consider transformations of the (metric) Quadratic Assignment Problem (QAP) that exploit the metric structure of a given instance. We show in particular how the structural properties of rectangular grids can be used to improve a given lower bound. Our work is motivated by previous research of Palubetskes (1988), and it extends a bounding approach proposed by Chakrapani and Skorin-Kapov (1993). Our computational results indicate that the present approach is practical; it has been applied to problems of dimension up ton = 150. Moreover, the new approach yields by far the best lower bounds on most of the instances of metric QAPs that we considered.
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    Mathematical programming 71 (1995), S. 207-219 
    ISSN: 1436-4646
    Keywords: Subgradient optimization ; Relaxation methods ; Projection methods
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    Notes: Abstract We study conditions for convergence of a generalized subgradient algorithm in which a relaxation step is taken in a direction, which is a convex combination of possibly all previously generated subgradients. A simple condition for convergence is given and conditions that guarantee a linear convergence rate are also presented. We show that choosing the steplength parameter and convex combination of subgradients in a certain sense optimally is equivalent to solving a minimum norm quadratic programming problem. It is also shown that if the direction is restricted to be a convex combination of the current subgradient and the previous direction, then an optimal choice of stepsize and direction is equivalent to the Camerini—Fratta—Maffioli modification of the subgradient method.
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    Mathematical programming 71 (1995), S. 221-245 
    ISSN: 1436-4646
    Keywords: Linear programming ; Presolving ; Interior-point methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Most modern linear programming solvers analyze the LP problem before submitting it to optimization. Some examples are the solvers WHIZARD (Tomlin and Welch, 1983), OB1 (Lustig et al., 1994), OSL (Forrest and Tomlin, 1992), Sciconic (1990) and CPLEX (Bixby, 1994). The purpose of the presolve phase is to reduce the problem size and to discover whether the problem is unbounded or infeasible. In this paper we present a comprehensive survey of presolve methods. Moreover, we discuss the restoration procedure in detail, i.e., the procedure that undoes the presolve. Computational results on the NETLIB problems (Gay, 1985) are reported to illustrate the efficiency of the presolve methods.
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    Computing 54 (1995), S. 303-316 
    ISSN: 1436-5057
    Keywords: 05 C 60 ; 05 C 85 ; Graph isomorphism ; automorphism partition ; polynomial algorithm ; chordal graphs ; graphs with fewP 4s
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Ein Graph ist chordal, wenn er keine sehnenlosen Kreise der Länge mindestens vier enthält und (q, t), wenn keine Menge von höchstensq Knoten mehr alst Wege der Länge drei induziert. Es ist bekannt, daß das Isomorphieproblem für chordale Graphen und für (6, 3) Graphen Isomorphie-vollständig ist. Wir stellen polynomiale Verfahren vor zur Bestimmung der Automorphiepartition und zum Testen der Isomorphie von Graphen, die sowohl chrodal als auch (6, 3) sind. Der zugang basiert auf dem Studium von simplizialen Partitionen von chordalen Graphen. Es wird gezeigt, daß für chordale (6, 3) Graphen die Automorphiepartition mit der gröbsten regulären simplizialen Partition übereinstimmt. Dies führt zu einemO(n+m logn) isomorphietest.
    Notes: Abstract A graph is chordal if it contains no chordless cycles of length at least four and (q, t) if no set of at mostq vertices induces more thant paths of length three. It is known that the isomorphism problem is isomorphism complete for chordal graphs and for (6, 3) graphs. We present polynomial methods to determine the automorphism partition and to test isomorphism of graphs which are both chordal and (6, 3). The approach is based on the study of simplicial partitions of chordal graphs. It is proved that for chordal (6, 3) graphs the automorphism partition coincides with the coarsest regular simplicial partition. This yields anO(n+m logn) isomorphism test.
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    Computing 54 (1995), S. 317-330 
    ISSN: 1436-5057
    Keywords: 65M06 ; 65M55 ; 65Y05 ; Parabolic partial differential equation ; Multigird ; parallel computing
    Source: Springer Online Journal Archives 1860-2000
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    Description / Table of Contents: Zusammenfassung Die Erscheinung von Parallelrechnern hat zur Entwicklung neuer Lösungsverfahren for zeitabhängige partielle Differentialgleichungen geführt. Zwei der in letzter Zeit entwickelten Verfahren — die Mehrgitter-Wellenformrelaxations-Methode und die zeitparallele Mehrgittermethode —haben zum Ziel, die Lösung zu vielen verschiedenen diskreten Zeitpunkten simultan zu berechnen. In dieser Arbeit wird anhand der Ergebnisse einer Fourier-Analyse für ein Modell-problem das Konvergenzverhalten beider Methoden verglichen.
    Notes: Abstract The advent of parallel computers has led to the development of new solution algorithms for time-dependent partial differential equations. Two recently developed methods, multigrid waveform relaxation and time-parallel multigrid, have been designed to solve parabolic partial differential equations on many time-levels simultaneously. This paper compares the convergence properties of these methods, based on the results of an exponential Fourier mode analysis for a model problem.
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  • 34
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    Computing 54 (1995), S. 251-272 
    ISSN: 1436-5057
    Keywords: Iterative process ; variational inequality ; non-accurate iteration ; projection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Diese Arbeit behandelt numerische Methoden zur Lösung linearer Variations-Ungleichungen auf einer abgeschlossenen konvexen Teilmenge des ℝn. Es gibt zwar zahlreiche Iterationsverfahren für den FallC=ℝ + n für den Fall einer beliebigen abgeschlossenen konvexen TeilmengeC wurde aber nur wenig vorgeschlagen. Die wesentliche Schwierigkeit in diesem Fall liegt in den Nichtlinearitäten des Randes vonC. In dieser Arbeit werden Iterationsverfahren zur Lösung linearer Variations-Ungleichungen auf einer beliebigen abgeschlossenen konvexen TeilmengeC entwickelt. In unseren Algorithmen wird die Berechnung einer linearen Variations-Ungleichung zerlegt in eine Folge von Projektionen eines Vektors auf die abgeschlossene konvexe TeilmengeC, die berechnet werden können, solange die Bestimmungsgleichungen des Randes gegeben sind. Insbesondere kann mit unseren Iterationsverfahren leicht eine Lösung berechnet werden fürC als Würfel, Kugel, Ellipsoid etc. Außerdem werden Näherungs-Iterationen, Abschätzung der Lösungen für unbeschränkte Bereiche und die Theorie der Randapproximation untersucht. Weiters wird eine notwendige und hinreichende Bedingung dafür angegeben, daß ein Vektor eine Näherungslösung ist. Schließlich werden einige numerische Beispiele präsentiert, die zeigen, daß die vorgestellten Algorithmen effektiv und effizient sind.
    Notes: Abstract This paper deals with numerical methods for solving linear variational inequalities on an arbitrary closed convex subsetC of ℝ n . Although there were numerous iterations studied for the caseC=ℝ + n , few were proposed for the case whenC is a closed convex subset. The essential difficulty in this case is the nonlinearities ofC's boundaries. In this paper iteration processes are designed for solving linear variational inequalities on an arbitrary closed convex subsetC. In our algorithms the computation of a linear variational inequality is decomposed into a sequence of problems of projecting a vector to the closed convex subsetC, which are computable as long as the equations describing the boundaries are given. In particular, using our iterations one can easily compute a solution whenC is one of the common closed convex subsets such as cube, ball, ellipsoid, etc. The non-accurate iteration, the estimate of the solutions on unbounded domains and the theory of approximating the boundaries are also established. Moreover, a necessary and sufficient condition is given for a vector to be an approximate solution. Finally, some numerical examples are presented, which show that the designed algorithms are effective and efficient. The exposition of this paper is self-contained.
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    Computing 54 (1995), S. 331-346 
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    Keywords: 65N55 ; 65N30 ; Frequency decomposition ; multi-level method ; finite elements ; hierarchical basis ; additive and multiplicative Schwarz methods ; subspace decomposition ; robustness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Kürzlich haben wir eine effektive Modifizierung des Frequenzzerlegungs-Mehrgitterverfahrens vorgestellt. In diesem Artikel wird die multiplikative Variante dieses Verfahrens untersucht. Unter Verwendung der Theorie der Unterraumkorrekturverfahren wird die Robustheit sowohl für die multiplikative als auch für die additive Variante bei Anwendung auf anisotrope Probleme mit beliebiger Raumdimension bewiesen. Die Implementierung beider Varianten wird diskutiert und numerische Ergebnisse werden angegeben.
    Notes: Abstract Recently, we introduced a cheap modification of Hackbusch'sFrequency Decomposition multi-level method. In this paper, the multiplicative variant of this method is studied. Using the theory of Subspace Correction Methods robustness is proved of both the multiplicative and additive variant applied to anisotropic problems in an arbitrary number of space dimensions. Implementation of both variants is discussed and numerical results are given.
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  • 36
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    Computing 54 (1995), S. 347-357 
    ISSN: 1436-5057
    Keywords: 65G10 ; 65L05 ; 65L07 ; Interval arithmetic ; interval methods for the initial value problem
    Source: Springer Online Journal Archives 1860-2000
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    Description / Table of Contents: Zusammenfassung Wenn Systeme gewöhnlicher Differentialgleichungen mit Intervallmethoden gelöst werden, besteht die Hauptschwierigkeit in der Reduktion des Wrappingeffekts. Die verschiedenen bis jetzt vorgeschlagenen Lösungen sind nur bei engen Anfangsintervallen oder speziellen Gleichungsklassen anwendbar. Diese Arbeit beschreibt einen Algorithmus, der statt Intervallen eine größere Familie von Mengen verwendet. Der Algorithmus führt zu einem sehr geringen Wrappingeffekt und ist bei beliebigem Gleichungstyp und weiten Anfangsintervallen anwendbar. Zum gegenwärtigen Zeitpunkt können nur 2-dimensionale Probleme behandelt werden.
    Notes: Abstract When solving ODEs by interval methods, the main difficulty is reducing the wrapping effect. Various solutions have been put forward, all of which are applicable for narrow initial intervals or to particular classes of equations only. This paper describes an algorithm which, instead of intervals, uses a larger family of sets. The algorithm exhibits a very small wrapping effect and applies to any type of equation and initial region. For the time being it handles only two-dimensional equations.
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    Computing 54 (1995), S. 359-375 
    ISSN: 1436-5057
    Keywords: AMS(MOS) ; 65H05 ; Polynomial zeros ; Eulidean division of Chebyshev expansions ; Sturm sequences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Wir stellen einen global konvergenten Algorithmus zur Berechnung aller Nullstellen eines Polynomsp n ,p n (z) = ∑ v = 0 n a v z v, mit reellen Koeffizienten vor. Durch Aufspalten vonp n (exp(it)) in seinen Real-und Imaginärteil können wir mittels Euklidischer Division von Čebyševentwicklungen und durch Argumentation mit Sturmschen Ketten entscheiden, obp n Nullstellen im Einheitskreis hat und wie viele Nullstellen auf dem Rand und im Inneren davon liegen. Somit erhalten wir mittels einer Bisektionsstrategie die Beträge aller Nullstellen bis auf eine vorgegebene Genauigkeit, und zusätzlich finden wir die Argumente als reelle Nullstellen eines Polynoms niedrigen Grades. Auf diese Weise erzeugen wir Startnäherungen für alle Nullstellen, die in einem letzten Schritt mittels eines iterativen Prozesses höherer Konvergenzordnung verbessert werden (z.B. Newton- oder Bairstowverfahren).
    Notes: Abstract We present a globally convergent algorithm for calculating all zeros of a polynomialp n ,p n (z) = ∑ v = 0 n a v z v, with real coefficients. Splittingp n (exp(it)) into its real and imaginary part we can decide via Euclidean division of Chebyshev expansions and Sturm sequence argumentations whetherp n has some zeros on the unit circle and how many zeros lie on the boundary and in the interior of it. Hence, by a bisection strategy we get the moduli of all zeros to a prescribed accuracy, and additionally we find the arguments as real zeros of a low degree polynomial. In this way we generate starting approximations for all zeros which in a final step are refined by an iterative process of higher order of convergence (e.g. Newton's or Bairstow's method).
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    Computing 55 (1995), S. 23-42 
    ISSN: 1436-5057
    Keywords: Radiosity ; Monte Carlo ; algorithms ; stochastic convergence ; transillumination method ; stochastic shooting method ; variance reduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Die vorgestellten neuen Radiosity Methoden für diffuse Szenen sind besonders geeignet, um die Lichtausbreitung in sehr komplexen Umgebungen in linearer Zeit zu berechnen. Die Verfahren beruhen auf rekursiven Algorithmen, die das Radiosity-Gleichungssystem mittels stochastischer Konvergenz löseu. Approximationen der ‘gathering-’ und ‘shooting-’ Verfahren werden statt einer exakten Berechnung jedes Reflexionsschrittes verwendet. Die Effizienz der Verfahren kann durch geeignete Varianzreduktionsmethoden verbessert werden.
    Notes: Abstract The fast radiosity-type methods for very complex diffuse environments, introduced herein, present a nearly linear-time solution. The outlined procedures rely on recursive algorithms with stochastic convergence for solving the radiosity equation system. Approximations of gathering and shooting at very low computational cost—rather than the exact matrix of a single reflection—are used. The efficiency of the methods will be increased by applying variance reduction techniques.
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    Computing 55 (1995), S. 43-53 
    ISSN: 1436-5057
    Keywords: Interval analysis ; range computation ; inclusion monotonicity ; Bernstein coefficients
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    Description / Table of Contents: Zusammenfassung Bekanntlich ist der Wertebereich eines Polynomsf über einem Intervall durch den kleinsten und größten Koeffizienten vonf bezüglich der Bernstein Basis auf dem Intervall eingeschränkt. Dadurch wird eine IntervallerweiterungF vonf definiert, die sogenannte Bernstein Form. In dieser Arbeit zeigen wir, daß die Bernstein Form inklusionsmonoton ist, d. h. wenn.X⊇Y dannF(X)⊇F(Y).
    Notes: Abstract It is well known that the range of polynomialf over an interval is bounded by the smallest and the largest coefficient off with respect to the Bernstein basis over the interval. This defines an interval extensionF off, which is called Bernstein form. In this paper we show that the bernstein form is inclusion monotone, i.e.X⊇Y impliesF(X)⊇F(Y).
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    Computing 55 (1995), S. 1-22 
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    Keywords: 65L ; 34C ; Reversible integration ; symplectic integrators ; variable step size ; long time integration
    Source: Springer Online Journal Archives 1860-2000
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    Description / Table of Contents: Zusammenfassung Werden symplektische oder reversible Integrationsverfahren mit herkömmlichen Schrittweitensteuerungen verwendet, so geht die symplektische, bzw. die reversible Struktur des Problems verloren. In dieser Arbeit wird gezeigt, dass die symplektische Struktur des Verfahrens nur dann erhalten wird, wenn die Schrittweite fast konstant bleibt. Für reversible Verfahren sind echt variable Schrittweiten möglich, die Schrittweite muss jedoch für “gespiegelte” Schritte gleich sein. Es werden verschiedene Wege aufgezeigt, um reversible, variable Schrittweiten zu konstruieren. Numerische Experimente zeigen, dass für das Keplerproblem die neuen Methoden den herkömmlichen Schrittweitensteuerungen oder den symplektischen Verfahren mit konstanter Schrittweite überlegen sind. Insbesondere wächst der globale Fehler linear.
    Notes: Abstract Conventional variable-step implementation of symplectic or reversible integration methods destroy the symplectic or reversible structure of the system. We show that to preserve the symplectic structure of a method the step size has to be kept almost constant. For reversible methods variable steps are possible but the step size has to be equal for “reflected” steps. We demonstrate possible ways to construct reversible variable step size methods. Numerical experiments show that for the Kepler problem the new methods perform better than conventional variable step size methods or symplectic constant step size methods. In particular they exhibit linear growth of the global error (as symplectic methods with constant step size).
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    Computing 55 (1995), S. 91-111 
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    Keywords: 65F15 (47A56) ; Nonlinear eigenvalue problem ; numerical solution ; condition number
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    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Wir betrachten die numerische Lösung des nichtlinearen EigenwertproblemsA(λ)x=0, wobei die MatrixA(λ) in nichtlinearer Weise vom Eigenwertparameter λ abhängt. Einige neue Methoden (die BDS Methoden) werden zusammen mit einer Untersuchung der Bedingungen dieser Methoden vorgestellt. Numerische Beispiele, welche diese Methoden vergleichen, werden präsentiert.
    Notes: Abstract We consider the numerical solution of the nonlinear eigenvalue problemA(λ)x=0, where the matrixA(λ) is dependent on the eigenvalue parameter λ nonlinearly. Some new methods (the BDS methods) are presented, together with the analysis of the condition of the methods. Numerical examples comparing the methods are given.
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  • 42
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    Computing 55 (1995), S. 55-73 
    ISSN: 1436-5057
    Keywords: 68P [Theory of data] ; 68P05 Data structures ; 68P20 information storage and retrieval ; Object-oriented data models ; ISA hierarchy ; complex objects ; transitive closure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung In den letzten Jahren sind viele objekt-orientierte Datenmodelle vorgeschlagen worden und dieses Gebiet ist zu einem der vielversprechendsten für die Entwicklung neuer Datenbanksysteme geworden. Bei Verwendung von komplexen Datenstrukturen, auf denen eine ISA Hierarchie definiert ist, wird effizientes Speichern and Zugreifen auf Objekte um vieles wichtiger. In dieser Arbeit schlagen wir effiziente mengenorientierte Algorithmen zur Speicherung und zum Zugriff auf komplexe Objekte in einer „Inheritance Hierarchie” vor.
    Notes: Abstract Many object oriented data models have been proposed in the past few years, and this field is one of the most promising for the development of new generation database systems. With complex data structures where an ISA hierarchy has been defined, the problem of efficiently storing and retrieving (a collection of) objects increases its relevance dramatically. This paper proposes efficient set-oriented algorithms for the storage and retrieval of complex objects in an inheritance hierarchy.
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    Computing 55 (1995), S. 75-89 
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    Keywords: 68Q20 ; 90C39 ; String edit distance ; finte state automaton ; nearest neighbor search ; doctionary lookup
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Es wird ein neuer Algorithmus für die Berechnung der Editierdistanz von Zeichenketten angegeben. Der Algorithmus beruht auf der Annahme, dass eine der beiden zu vergleichenden Zeichenketten ein a priori bekannter Eintrag in einen Wörterbuch ist. Dieser Wörterbucheintrag wird in einer off-line Phase in einen deterministischen endlichen Automaten konvertiert. Für einen gegebenen Automaten und ein Eingabewort entspricht die Berechnung der Editiordistanz einer Traversierung verschiedener Zustände dieses Automaten. Diese Prozedur benötigt Zeit, die lediglich linear von der Länge des Eingabeworts abhängt. Die Zeit ist unabhängig von der Länge des Wörterbucheintrags. Die endlichen Automaten, welche zuN verschiedenen Wörterbucheinträgen gehören, können zu einem einzigen Automaten zusammengefasst werden. Auf diese Weise benötigen die Berechnung der Editierdistanz zwischen dem Eingabewort und jedem Wörterbucheintrag sowie die Bestimmung des nächsten Nachbarn im Wörterbuch lediglich lineare Zeit hinsichtlich der Länge des Eingabeworts. Die Anzahl der Zustände des Automaten ist jedoch von exponentieller Grössenordnung.
    Notes: Abstract A new algorithm for string edit distance computation is given. The algorithm assumes that one of the two strings to be compared is a dictionary entry that is known a priori. This dictionary word is converted in an off-line phase into a deterministic finite state automaton. Given an input string and the automaton derived from the dictionary word, the computation of the edit distance between the two strings corresponds to a traversal of the states of the automaton. This procedure needs time which is only linear in the length of the input string. It is independent of the length of the dictionary word. Given not only one butN different dictionary words, their corresponding automata can be combined into a single deterministic finite state automaton. Thus the computation of the edit distance between the input word and each dictionary entry, and the determination of the nearest neighbor in the dictionary need time that is only linear in the length of the input string. However, the number os states of the automation is exponential.
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    Computing 55 (1995), S. 163-180 
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    Keywords: 65L05 ; Hopf bifurcation ; Runge-Kutta ; Poincare map
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    Description / Table of Contents: Zusammenfassung Um das Verhalten bestimmter Ein- und Mehrschrittverfahren für gewöhnliche Differentialgleichungen an schwach anziehenden Fixpunkten bzw. schwach anziehenden periodischen Lösungen zu untersuchen, wird Rückwärts-Fehleranalyse eingesetzt. Bei vielen Methoden tritt eine Hopf-Verzweigung auf; der Effekt einer adaptiven Gitteranpassung für solche Situationen wird an einem Spezialfall demonstriert.
    Notes: Abstract Backward error analysis is used to analyze the behavior of selected one-step and multi-step methods for ordinary differential equations at weakly attracting fixed points and weakly attracting periodic solutions. For many methods, a Hopf bifurcation for maps occurs. The effect of an adaptive mesh selection procedure on these results is presented for a special case.
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  • 45
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    Computing 55 (1995), S. 181-189 
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    Keywords: 65N55 ; 65F10 ; Smoothing property ; multi-grid method ; semi-iteration
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    Description / Table of Contents: Zusammenfassung Eine Modifikation des Lemmas von Reusken wird angegeben. Sie gestattet, im Falle von konvergenten Glättungsiterationen die Konvergenzgeschwindigkeit in die Abschätzung der Glättungseigenschaft mit aufzunehmen. Eine derartige Abschätzung wird bei robusten Mehrgitterverfahren benötigt. Ferner wird ein einfacher semiiterativer Glätter angegeben, der ein asymptotisch besseres Verhalten besitzt.
    Notes: Abstract A modification of the Lemma of Reusken is given. It allows us to improve the estimate of the smoothing property in cases where the contraction number of the iteration is small. This is of importance for robust multi-grid methods. Moreover, we describe a simple semi-iterative smoother with better asymptotic behaviour than for the stationary iterative smoother.
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  • 46
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    Computing 55 (1995), S. 207-221 
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    Keywords: 65COS ; 65DIS ; Particle methods ; discrepancy estimates ; nonlinear functionals
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    Description / Table of Contents: Zusammenfassung Wir betrachten die numerische Berechung nichtlinearer Funktionale von Verteilungsfunktionen, die durch Punktmaße angenähert werden. Zwei Methoden werden beschrieben und Abschätzungen für die Konvergenzgeschwindigkeit werden angegeben. Außerdem werden numerische Resultate für das Entropiefunktional vorgestellt.
    Notes: Abstract We consider the numerical computation of nonlinear functionals of distribution functions approximated by point measures. Two methods are described and estimates for the speed of convergence as the number of points tends to infinity are given. Moreover, numerical results for the entropy functional are presented.
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    Computing 55 (1995), S. 223-236 
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    Keywords: 65L05 ; 65L06 ; Runge-Kutta methods ; interpolations ; delay differential equations
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    Description / Table of Contents: Zusammenfassung Beim numerischen Lösen von Differentialgleichungen mit nacheilendem Argument (DDEs) mit Hilfe von stetigen expliziten Runge-Kutta Methoden entstehen Schwierigkeiten, wenn die Argumentverzögerung verschwindet oder zumindest kleiner als die Verfahrensschrittweite wird. In dieser Situation wird der herkömmlich explizite und sequentielle Prozeß der Stufenberechnungen des RK-Schemas ein impliziter und muß überdies iteriert werden. In dieser Arbeit werden einige Iterationsmethoden untersucht und deren Ordnung bestimmt.
    Notes: Abstract In the numerical solution of delay differential equations by a continuous explicit Runge-Kutta method a difficulty arises when the delay vanishes or becomes smaller than the stepsize the method would like to use. In this situation the standard explicit sequential process of computing the Runge-Kutta stages becomes an implicit process and an iteration scheme must be adopted. We will consider alternative iteration schemes and investigate their order.
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    Computing 55 (1995), S. I 
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    Computing 55 (1995), S. 237-253 
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    Keywords: 65N06 ; Finite difference method ; impulsive partial differential-functional equations
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    Description / Table of Contents: Zusammenfassung Wir betrachten Anfangs- und Randwertprobleme von partiellen Impuls-Differential-Funktionalgleichungen erster Ordnung. Wir leiten hinreichende Bedingungen für die Konvergenz einer allgemeinen Klasse von Einschrittmethoden her. Wir nehmen weiters an, daß die gegebenen Funktionen bezüglich ihrer Funktionalargumente einer nichtlinearen Abschätzung vom Perron-Typus genügen. Der Stabilitätsbeweis basiert auf einem Theorem über Differenzen-Funktionalgleichungen, die von einem Impuls-Differential-Funktionalproblem stammen. Grundsätzlich nehmen wir an, daß die betrachteten Funktionen die Volterra-Bedingung erfüllen. Ein numerisches Beispiel wird angeführt.
    Notes: Abstract We consider initial boundary value problems for first order impulsive partial differential-functional equations. We give sufficient conditions for the convergence of a general class of one step difference methods. We assume that given functions satisfy the non-linear estimates of the Perron type with respect to the functional argument. The proof of stability is based on a theorem on difference functional inequalities generated by an impulsive differential-functional problem. It is an essential assumption in our consideration that given functions satisfy the Volterra condition. We give a numerical example.
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    Computing 55 (1995), S. 191-206 
    ISSN: 1436-5057
    Keywords: 68Q25 ; 68U05 ; Rectangles ; balanced cuts ; separation ; binary space partition
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    Description / Table of Contents: Zusammenfassung Gegeben sei eine Menge vonn (ggf. überlappenden) isothetischen Hyperrechtecken imd-dimensionalen Raum. Diese Arbeit beschäftigt sich mit Zerlegungen dieser Hyperrechteckmenge durch Schnitthyperebenen, wobei wir annehmen, daß jedes von einer Hyperebene geschnittene Hyperrechteck in zwei nicht-überlappende Hyperrechtecke zerschnitten wird. Wir untersuchen das Verhalten einiger Balancierungskriterien für Schnitte und präsentieren optimale and praktikable Algorithmen zur Berechnung der entsprechenden balancierten Schnitte. Schließlich geben wir auch scharfe Worst-case-Schranken für die bestmöglich erreichbare Qualität der balancierten Schnitte an.
    Notes: Abstract We are given a set ofn d-dimensional (possibly intersecting) isothetic hyperrectangles. The topic of this paper is the separation of these rectangles by means of a cutting isothetic hyperplane. Thereby we assume that a rectangle which is intersected by the cutting plane iscut into two non-overlapping hyperrectangles. We investigate the behavior of several kinds of balancing functions, as well as their linear combination and present optimal and practical algorithms for computing the corresponding balanced cuts. In addition, we give tight worst-case bounds for the quality of the balanced cuts.
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    Computing 55 (1995), S. 271-288 
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    Keywords: 65F10 ; Finite elements ; multigrid methods ; error control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Wir behandeln das Problem einer adaptiven Fehlerkontrolle bei Finite-Elemente-Methoden unter Enschluß des Fehlers, der durch ungenaue Lösung der diskreten Gelichungen entsteht. Wir beweisen A-posteriori-Fehlerabschätzungen für ein elliptisches Modellproblem, welches mit linearen finiten-Elementen diskretisiert wird. Die diskreten Gleichungen werden mit Hilfe des kanonischen Finite-Elemente-Mehrgitterverfahrens gelöst. Die Beweise beruhen auf der Kombination der «starken” stabilitätseigenschaft des zugrundeliegenden Differentialoperators und der Galerkin-Orthogonalität sowohl des Finite-Elemente-als auch des Mehrgitterverfahrens.
    Notes: Abstract We consider the problem of adaptive error control in the finite element method including the error resulting from, inexact solution of the discrete equations. We prove a posteriori error estimates for a prototype elliptic model problem discretized by the finite element with a canomical multigrid algorithm. The proofs are based on a combination of so-called strong stability and, the orthogonality inherent in both the finite element method can the multigrid algorithm.
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  • 52
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    Computing 55 (1995), S. 289-304 
    ISSN: 1436-5057
    Keywords: 65N15 ; 65N30 ; 65N50 ; Adaptive mesh refinement ; a posteriori error estimate ; nonlinear Poisson equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Wir entwickeln adaptive Methoden zur Berechnung von Finite Elemente-Lösungen der Partiellen Differentialgleichung −Δu=f(u) auf einem beschränktem Gebiet Ω ⊆ ℝ2. In der Praxis arbeitet man mit einer Approximationf h vonf, was zu falschen Ergebnissen führen kann, wenn man den zugehörigen Approximationsfehler auf dem groben Gitter nicht mitberücksichtigt. Wir verwenden eine Strategie, die zu Beginn der Iteration robust aber weniger effizient ist und gehen zu effektiveren Methoden über, falls gewisse Sättigungsbedingungen erfühlt sind. Dazu leiten wir a posteriori Fehlerschranken und a posteriori Sättigungsbedingungen her, um die Qualität der numerischen Lösung zu beurteilen.
    Notes: Abstract Our goal is to develop adaptive strategies in order to obtain finite element solutions of the partial differential equation-Δu=f(u) in a bounded domain Ω ⊆ ℝ2. In practice one works with an approximationf h off. But this may give wrong results if we do not control the coresponding approximation error on coarse girds. In this work we develop a strategy that is robust, but less efficient, in the beginning of the adaptive algorithm and switches to a more efficient procedure if certainsaturation conditions are satisfied. The results are based on a posteriori saturation criterial that measure the quality of the approximation solution.
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  • 53
    ISSN: 1436-6215
    Keywords: Kraftsportler ; hohe Proteinzufuhr ; renale Nettosäureausscheidung ; Urin pH ; Ammoniumausscheidung ; Ammoniumproduktion ; renale Säureausscheidungskapazität ; Sulfat ; Bodybuilder ; high protein diet ; renal net acid excretion ; urine-pH ; ammonium excretion ; ammonia production ; sulfate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary Bodybuilders often prefer a high protein diet to achieve maximum skeletal muscle hypertrophy. In this study the effect of a high protein diet on renal acid load and renal handling of proton excretion was studied comparing dietary intake and urinary ionograms in 37 male bodybuilders and 20 young male adults. Energy intake (+7 %), protein intake (128 vs 88 g/d/1.73 m2), and renal net acid excretion (95 vs 64 mmol/d/1.73 m2) were higher in the bodybuilders than in the controls, however, urine-pH was only slightly lower (5.83 vs 6.12). In the bodybuilders renal ammonium excretion was higher at any given value of urine pH than in the controls. In a regression analysis protein intake proved to be an independent factor modulating the ratio between urine-pH and renal ammonium excretion. The concomitant increase of renal net acid excretion and maximum renal acid excretion capacity in periods of high protein intake appears to be a highly effective response of the kidney to a specific food intake leaving a large renal surplus capacity for an additional renal acid load.
    Notes: Zusammenfassung Kraftsportler ernähren sich zur Förderung des Muskelwachstums häufig proteinreich. In dieser Studie wurde die Wirkung einer hohen Proteinzufuhr auf die renale Säurelast und die renale Säureausscheidungskapazität anhand des Vergleichs der Daten der Nährstoffzufuhr und der Harnionogramme von 37 Kraftsportlern mit hoher Proteinzufuhr und 20 jungen Erwachsenen mit normaler Proteinzufuhr (Vergleichsgruppe) untersucht. Die Kraftsportler zeigten eine höhere Energie-(+7 %) und Proteinzufuhr (128 vs 88 g/d/1.73 m2) und eine höhere renale Nettosäureausscheidung (95 vs 64 mmol/d/1.73 m2) als die Vergleichsgruppe. Die Differenz der Urin pH-Werte der beiden Gruppen war allerdings erstaunlich gering (5.83 vs 6.12). Bei den Kraftsportlern war die renale Ammoniumausscheidung bei allen Urin pH-Werten deutlich höher als bei der Vergleichsgruppe. Eine Regressions-analyse ergab, daß die Proteinzufuhr das Verhältnis von Urin pH und renaler Ammoniumausscheidung eigenständig zu beeinflussen vermag. Eine vermehrte Proteinzufuhr führt zu einer erhöhten renalen Säurelast und Nettosäureausscheidung. Die gleichzeitig auftretende Steigerung der renalen Säureausscheidungskapazität infolge einer erhöhten Ammoniumproduktion stellt einen sinnvollen Anpassungsmechanismus des Körpers an diese besondere Form der Ernährung dar, der dem Körper eine ausreichende funktionelle Reservekapazität für weitere den Säure-Basen-Haushalt belastende pathophysiologische Ereignisse erhält.
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  • 54
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    European journal of nutrition 34 (1995), S. 160-163 
    ISSN: 1436-6215
    Keywords: Immunglobulin G ; Dotterantikörper ; Intestinale Absorption ; Kalb ; Immunoglobulin G ; yolk antibodies ; intestinal absorption ; calf
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary Studying the prophylactic effects of specific yolk antibodies against diarrhea in newborn calves, also the intestinal absorption of unspecific heterogeneous avian antibodies as well as their effects on the uptake of maternal bovine colostral antibodies (bIgG) was investigated. Two groups of newborn calves received egg powder (16 g or 8 g per day) for the first 10 days of their life beginning with the first meal. A third group was kept as a control without any egg powder in their diet. Blood samples (5 to 10 calves per sampling time) were taken from 123 calves at 6, 12, 24, 48, or 96 h postnatally. With both doses the highest chicken IgG (cIgG) levels (3.1 µg resp. 1.2 µg per ml serum) have been measured 12 h after birth. These concentrations decreased continuously to the levels of 1.1 µg resp. 0.2 µg cIgG per ml serum at 96 h postnatally. The uptake into blood at 6 h postnatally has roughly been estimated as approximately 23 % (bIgG) and 7 % resp. 6 % (cIgG) of the IgG dosages given with the first meal. The time-course (6 to 96 h) of the bIgG level in blood was quite stable, plateauing already after 6 h at a mean of 5.9 mg per ml serum. Significant differences between the bIgG levels of calves with yolk antibodies in their diet (6.2 resp. 6.1 mg bIgG per ml serum) and those of the control group (5.4 mg per ml serum) could not be observed. Obviously, the prophylactic use of egg powder in newborn calves has no negative effect on the absorption of colostral antibodies. However, with the feeding of chicken egg yolk antibodies already with the first meal also the absorption of avian antibodies has to be taken into consideration.
    Notes: Zusammenfassung Im Rahmen einer Untersuchung zur prophylaktischen Wirksamkeit von spezifischen Dotterantikörpern bei erregerbedingten Kälberdurchfällen wurde auch die Absorption der unspezifischen heterologen aviären Dotterantikörper (cIgG) und deren Wirkung auf die Aufnahme von maternalen bovinen Kolostrumantikörpern (bIgG) überprüft. Zwei Gruppen von neugeborenen Kälbern wurde sprühgetrocknetes Volleipulver ab der ersten Tränke in einer Dosierung entweder von 16 g oder von 8 g pro Tag während der ersten 10 Lebenstage verabreicht. Eine dritte Gruppe diente als Kontrolle und erhielt kein Eipulver. Von insgesamt 123 Kälbern (5 bis 10 Kälber pro Entnahmezeitpunkt) wurden 6, 12, 24, 48, 72 bzw. 96 Stunden post natum Blutproben genommen. Bei beiden Eipulverdosierungen wurden die höchsten Hühner-IgG-Konzentrationen (3,1 µg bzw. 1,2 µg pro ml Serum) jeweils 12 Stunden post natum ermittelt. Diese cIgG-Konzentrationen nahmen danach kontinuierlich auf Konzentrationen von 1,1 µg bzw. 0,2 µg pro ml Serum zum Zeitpunkt 96 Stunden post natum ab. Bezogen auf die mit der ersten Tränke verabreichte bIgG- bzw. cIgG-Menge wurde überschlagsweise zum Zeitpunkt 6te Lebensstunde eine Anflutung im Blut von 23 % (bIgG) bzw. von 7 % und 6 % (cIgG) errechnet. Der zeitliche Verlauf (6te bis 96te Stunde) der Konzentration des bovinen IgGs in den Blutproben war vergleichsweise stabil und lag durchschnittlich bei 5,9 mg pro ml Serum, wobei das Plateau bereits nach 6 Stunden erreicht war. Signifikante Unterschiede zwischen den bIgG-Werten der Kälber, die Dotterantikörper bekamen (6,2 bzw. 6,1 mg pro ml Serum), und denen der Kontrollgruppe (5,4 mg pro ml Serum) waren nicht zu beobachten. Eipulver kann somit offensichtlich zur Prophylaxe bei neugeborenen Kälbern ohne Beeinträchtigung der Absorption der kolostralen Antikörper verabreicht werden. Allerdings muß bei einer Eipulververgabe mit der ersten Tränke auch mit einer Absorption von aviären Dotterantikörpern gerechnet werden.
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  • 55
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    European journal of nutrition 34 (1995), S. 190-197 
    ISSN: 1436-6215
    Keywords: Verzehrserhebungen ; Nationale Verzehrsstudie ; Lebensmittelverzehr ; internationaler Vergleich von Verzehrserhebungen ; Dietary surveys ; national food consumption study ; food intake ; international comparison of dietary surveys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary Referring to the data of the National Food Consumption Study in Germany and the Dietary and Nutritional Survey of British Adults, this article compares the food intake of German and British adults. Such a comparison is possible because both studies have mainly the same methodology. The comparison of the food intake of German and British adults points out food groups which Germans consume inhigher amounts than British people do. To this category belong meat products and sausages, eggs, cheese and cottage cheese, butter, fat for cooking and salad oil, bread and pastries, vegetables, fruit, preserves and soft drinks. The Germans consumeless meat, fish and fish products, milk and milk products, pasta, rice and miscellaneous cereals, potatoes, sugar, sweets and tea than the British people do. The consumption of fruit products, alcoholic beverages and coffee is nearly the same in Germany and Great Britain.
    Notes: Zusammenfassung Anhand der Nationalen Verzehrsstudie und des „Dietary and Nutritional Survey of British Adults“ wird der Lebensmittelverzehr der Erwachsenen in Deutschland und Großbritannien verglichen. Dies ist möglich, weil die Methodik weitgehend übereinstimmt. Beim Vergleich des Lebensmittelverzehrs von Deutschen und Briten fallen Lebensmittel auf, von denen die Deutschenmehr zu sich nehmen als die Briten. Dazu gehören Fleisch- und Wurstwaren, Eier, Käse und Quark, Butter, Speisefette und -öle, Brot und Backwaren, Gemüse, Obst, Marmelade/Konfitüre und alkoholfreie Getränke. Die Deutschen nehmen dagegenweniger Fleisch, Fisch und Fischwaren, Milch und Milchprodukte, Nährmittel, Kartoffeln, Zucker, Süßwaren und Tee zu sich als die Briten. Beim Konsum von Obstprodukten, alkoholischen Getränken und Röstkaffee herrschen nur geringfügige Unterschiede zwischen Deutschen und Briten.
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  • 56
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    European journal of nutrition 34 (1995), S. 206-213 
    ISSN: 1436-6215
    Keywords: Fischöl ; Olivenöl ; Überernährung ; Sauen ; Energiebilanz ; Thermogenese ; Gaswechsel ; Fish oil ; olive oil ; overfeeding ; sows ; energy balance ; thermogenesis ; gaseous exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary A trial on total metabolism was conducted in eight nonpregnant, nonlactating sows over eight periods, each of 16 days duration, to measure potential fatty acid induced thermogenesis. During the first and last experimental periods, the animals received a basal ration which just covered the energy maintenance requirement. In the second to seventh periods supplements of olive oil, fish oil, or puffed wheat starch as reference nutrient were added to the diet in random sequence at two levels up to 50 % above the maintenance requirement. All rations were calculated with reference to the sows' initial weight and remained quantitatively unchanged throughout the experiment. The animals were fed twice daily. During each metabolism period a complete energy balance was assessed for all sows by means of collection technique (feed, feces, urine), and 48-h measurements of the gas exchange in a respiration chamber. The sows' body mass increased linearly during the course of the experiment by 5.8 kg per period. The three supplement types had no influence on the animals' final body weight, wich averaged 205.5 kg with the starch supplement, 204.8 kg with olive oil, and 205.8 kg with fish oil. Energy digestibility (DE/GE) was 100 % for all three supplements, and metabolizability of energy (ME/GE) one percentage point less. Carbon and energy depositions showed a pronounced linear relationship to the level of supplementation and were also influenced by the type of supplement. Heat production was 20.9 MJ/d after feeding the basal ration alone and, taking the average of the two supplementation levels, 21.6 MJ for the starch supplement, 21.0 MJ for olive oil, and 20.6 MJ for fish oil. The relationship between energy deposition and the supply of ME resulted in regression coefficients of 0.9 MJ/MJ after feeding starch and 1.0 MJ/MJ after feeding the two oils. It can be concluded from these results that supplementation of the diet with fat containing mono- or polyunsaturated fatty acids above the energetic maintenance requirement under conditions of severely restricted movement (respiration chamber) has no influence on thermogenesis and consequently causes a deposition of energy equivalent to the amount supplied with the dietary fat.
    Notes: Zusammenfassung Zur Messung einer fettsäureninduzierten Thermogenese wurde ein Gesamtstoffwechselversuch mit 8 nichtgraviden, nichtlaktierenden Sauen über 8 Perioden von jeweils 16 Tagen Dauer durchgeführt. Die Tiere erhielten in der ersten und letzten Versuchsperiode eine den energetischen Erhaltungsbedarf deckende Grundration. In Periode 2 bis 7 wurden in zufälliger Reihenfolge Olivenöl, Fischöl bzw. als Referenznährstoff Weizenquellstärke in jeweils 2 Mengenstufen bis 50 % über das Erhaltungsniveau zugelegt. Alle Rationen wurden aufgrund der Anfangsmasse der Sauen eingestellt und über den gesamten Versuch in unveränderter Menge beibehalten. Die Fütterung erfolgte zweimal täglich. Von allen Tieren wurde in jeder Stoffwechselperiode eine vollständige Bilanzmessung mit Sammeltechnik (Futter, Kot, Harn) und 48stündiger Messung des Gaswechsels in der Respirationskammer durchgeführt. Die Körpermasse der Sauen stieg im Versuchsablauf linear um 5,8 kg je Zulageperiode an. Die drei Zulagearten hatten keinen Einfluß auf die Körpermasse der Tiere, sie wogen im Mittel bei Stärkezulage 205,5 kg, bei Olivenöl und Fischöl 204,8 bzw. 205,8 kg. Die Verdaulichkeit der Energie (DE/GE) betrug bei allen drei Zulagen 100 %, die Umsetzbarkeit der Energie (ME/GE) einen Prozentpunkt weniger. Der Kohlenstoffund Energieansatz zeigte eine ausgeprägte lineare Abhängigkeit zur Zulagenhöhe sowie einen signifikanten Effekt der Zulagenart. Die Wärmebildung betrug bei alleiniger Fütterung der Grundration 20,9 MJ und im Mittel der beiden Zulagestufen bei Stärkefütterung 21,6 MJ und bei Olivenöl und Fischöl 21,0 bzw. 20,6 MJ/d. Die Abhängigkeit des Energieansatzes von der Zufuhr an ME ergab Regressionskoeffizienten von 0,9 MJ/MJ bei Verabreichung von Stärke und 1,0 MJ/MJ bei Fütterung der beiden Öle. Aus den Ergebnissen ist zu folgern, daß eine Zulage von Fetten mit einfach oder mehrfach ungesättigten Fettsäuren über dem energetischen Erhaltungsbedarf unter der Bedingung stark eingeschränkter Bewegungsaktivität (Respirationskammer) keinen Einfluß auf die Thermogenese und somit einen energetischen Ansatz entsprechend der zugeführten Energie des Nahrungsfettes bewirkt.
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  • 57
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    European journal of nutrition 34 (1995), S. 269-276 
    ISSN: 1436-6215
    Keywords: Iod ; Uriniod ; Quotient Uriniod/Urinkreatinin ; Iodresorption ; Iodbioverfügbarkeit ; Nahrungsiod ; Iodine ; urinary iodine ; quotient iodine in urine/creatinine in urine ; iodine absorption ; iodine bioavailability ; alimentary iodine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary The standard food for our volunteers, prepared in the central kitchen of the University Hospital of Tuebingen, consisted of breakfast, warm lunch and cold supper and contained, on average, approximately 230 µg of iodine/day. It is generally assumed that an equilibrium is established between iodine intake from food and urinary iodine excretion. Hence, the amount of iodine excreted with the urine within 24 h may reflect the daily ingestion of iodine. The fecal iodine losses are considered negligible. The alimentary iodine supply from food of our clinic would meet the WHO recommendations of 〉150 µg/day to prevent iodine-deficiency goiters. In 27 healthy volunteers the daily uptake of iodine was determined and the urinary excretion of iodine within 24 h was measured. Unexpectedly, only 16 % to 18 % of the alimentary iodine were excreted with the urine. Hence, the utilization of iodine from the food appears to be limited and therefore cannot prevent goiters in goiter areas. In addition, it was found that the correlation between urinary excretion of iodine and urinary excretion of creatinine is not a reliable parameter for the real daily excretion of iodine and iodine balance.
    Notes: Zusammenfassung Die Verpflegung (Frühstück, Mittagessen und Abendessen) aus der Zentralküche des Universitätsklinikums in Tübingen enthält durchschnittlich 230 µg Iod/Tag. Bei Personen, die täglich an dieser Verpflegung teilnehmen, stellt sich ein Gleichgewicht zwischen Iodaufnahme und renaler Iodausscheidung ein. Die Iodausscheidung über die Faeces gilt als vernachlässigbar. Die in unserer Klinikverpflegung angebotene Iodmenge entspricht dem von der WHO geforderten Angebot von 〉150 µg Iod/Tag, um endemische Strumen zu verhindern. Bei 27 gesunden Probanden wurden die tägliche Iodaufnahme und die zugehörige Ausscheidung von Iod im 24-h-Urin ermittelt. Dabei zeigte sich überraschend, daß vom angebotenen Iod nur 16 % bis 18 % mit dem Urin ausgeschieden wurden. Das mit der Nahrung angebotene Iod steht offenbar dem Organismus nur begrenzt zur Verfügung und kann Strumen in Iodmangelgebieten nicht verhindern. Der Bezug der Uriniodausscheidung auf das Kreatinin liefert nur einen groben Parameter für die tägliche Iodausscheidung und für die Iodbilanzierung.
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    European journal of nutrition 34 (1995), S. 261-268 
    ISSN: 1436-6215
    Keywords: Auswahl von Mahlzeiten ; Einschätzung von Mahlzeiten ; Gesundheitswert ; Entwicklungsstand ; Ernährungserziehung ; Selection of meals ; estimation of meals ; value of health ; age differences ; education of nutrition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary With regard to the reported knowledge concerning the health value of food in 9–10-year-old children (DGE, 1984) the question arose of whether this knowledge is also valid if pupils have to evaluate meals. Twenty-seven photos of meals (9 each of breakfast, lunch and supper) were presented to 252 children of the age groups 6–7, 9–10 and 12–13 years. By means of these photos, they were requested to organize their meals for 3 days. Subsequent to this procedure the children were asked to evaluate the meals with regard to their health value. The presented meals were classified by five experts of nutrition as more healthy, indifferent and less healthy. The results showed an improved selection of more healthy meals with increasing age. Likewise, the selection of meals for lunch and supper was better than the one for breakfast. There were no differences between boys and girls and children with and without experience of dieting. The evaluation of more healthy and less healthy meals demonstrated an improvement with increasing age. In contradiction to these results, children within all age groups showed a very low level of estimation (10 %) for indifferently classified meals and this level did not improve with increasing age. The results were discussed concerning the establishment of an appropriate education of nutrition with regard to the developmental stage and the emotional and motivational engagement of the children.
    Notes: Zusammenfassung Im Hinblick auf die relativ gute Bewertung einzelner Nahrungsmittel durch 9–10jährige Kinder (DGE, 1984) stellte sich die Frage, ob dieses Wissen gleichfalls für die Einschätzung von Mahlzeiten gilt. 252 Kinder der Altersgruppe 6–7 Jahre, 9–10 Jahre und 12–13 Jahre wurden daher 27 Fotos von Mahlzeiten (je 9mal Frühstück, Mittagessen und Abendbrot) vorgelegt. Die Kinder wurden aufgefordert, ihre Mahlzeiten auf der Basis der vorgelegten Fotos für 3 Tage zusammenzustellen. Danach wurden die Kinder befragt, wie sie die Mahlzeiten bezüglich ihres Gesundheitswertes einschätzen würden. Die vorgelegten Mahlzeiten waren von 5 Experten zuvor als „eher gesund“, „mittelmäßig gesund“ und „eher ungesund“ eingestuff worden. Die Ergebnisse weisen auf eine häufigere Auswahl „eher gesunder“ Mahlzeiten mit ansteigendem Alter hin. Die Auswahl für das Mittagessen und das Abendbrot war unter dem Aspekt des Gesundheitswertes in allen Altersstufen besser als die Auswahl für das Frühstück. Es zeigten sich keine deutlichen Unterschiede zwischen Jungen und Mädchen und Kindern mit und ohne Diäterfahrung. Die Einschätzung der „eher gesunden“ bzw. „eher ungesunden“ Mahlzeiten verbesserte sich gleichfalls mit zunehmendem Alter. Andererseits fand sich bei der Einschätzung der als „mittelmäßig gesund“ eingestuften Mahlzeiten ein recht niedriges Niveau in der richtigen Einschätzung (etwa 10 %) auf allen 3 Altersstufen. Die Ergebnisse werden im Zusammenhang mit gegenwärtigen und künftigen Maßnahmen in der Ernährungserziehung diskutiert, wobei aufgrund der Ergebnisse Entwicklung und Motivation und die emotionalen Bedürfnisse der Kinder stärker zu berücksichtigen sind.
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    European journal of nutrition 34 (1995), S. 166-166 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
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    European journal of nutrition 34 (1995), S. 167-176 
    ISSN: 1436-6215
    Keywords: Vitamin C ; Vitamin E ; β-Carotin ; antioxidative Vitamine ; Vitaminaufnahme ; Augenlinse ; Katarakte ; Alter ; Vitamin C ; vitamin E ; β-carotene ; antioxidant vitamins ; vitamin intake ; ocular lens ; cataracts ; elderly
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary Senile cataract indicates the opacity of ocular lenses occuring in old and especially in very old people. Lens proteins are extremely long-living and often show oxidative damages. Aging and smoking appear to be the greatest risk factors for the development of lens opacities. The sufficient antioxidant protection of young lenses decreases with the aging process. Consequently, the importance of other protective factors increases. Nutritional factors, particularly vitamins with antioxidant properties, may influence the development of senile cataracts in the ocular lens. Meanwhile an association between the supply with vitamin C, E and β-carotene and the risk of cataract development was demonstrated in animal studies and also in an increasing number of epidemiological studies. These epidemiological studies mainly support the hypothesis that higher vitamin intakes reduce the risk of developing cataracts in old age. The antioxidant properties of the named nutrients give a plausible explanation for the mechanism of cataractogenesis. On the basis of the present data definitive recommendation, necessary for cataract prevention can not yet be established. Some results seem to support higher recommendations. At the moment several large human intervention trials are carried out. Form these studies a further confirmation of the antioxidant hypothesis and of a dose-response-relationship are expected.
    Notes: Zusammenfassung Die senile Katarakt ist eine im Alter und besonders häufig im hohen Alter auftretende Trübung der Augenlinsen. Die extrem langlebigen Linsenproteine weisen häufig oxidationsbedingte Schädigungen auf. Altern und Rauchen erscheinen als die größten Risikofaktoren für eine Kataraktbildung. Während junge Augenlinsen in der Regel über eine ausreichende antioxidative Schutzkapazität verfügen, nimmt diese mit dem Alter ab. Damit wächst die Bedeutung anderer Schutzfaktoren. Nahrungsfaktoren, besonders Vitamine mit antioxidativen Eigenschaften, schützen möglicherweise vor einer Bildung von senilen Katarakten in den Augenlinsen. Ein Zusammenhang zwischen der Versorgung mit Vitamin C, E und β-Carotin und dem Kataraktrisiko konnte in tierexperimentellen Untersuchungen aufgezeigt und inzwischen auch in einer wachsenden Zahl epidemiologischer Studien nachgewiesen werden. Die bisher vorliegenden epidemiologischen Studien unterstützen mehrheitlich die Hypothese, daß erhöhte Vitaminaufnahmen das Risiko einer Kataraktbildung reduzieren. Die antioxidative Wirkung der genannten Nährstoffe liefert eine plausible Erklärung für den Mechanismus der Kataraktgenese. Es fehlen aber noch Studien, aus denen sich die für eine Prävention notwendigen Vitaminmengen ableiten lassen. Einige Untersuchungsergebnisse sprechen möglicherweise dafür, daß diese über den bisher geltenden Empfehlungen liegen. Zur Zeit werden verschiedene, große Interventionsstudien durchgeführt, die eine weitere Absicherung der Antioxidanshypothese und von Dosis-Wirkungsbeziehungen erwarten lassen.
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    European journal of nutrition 34 (1995), S. 240-242 
    ISSN: 1436-6215
    Keywords: Iodine ; iodized salt ; canteen ; lunch meals ; sodium chloride ; Jod ; jodiertes Speisesalz ; Großküche ; Mittagessen ; Natriumchlorid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung In zwei Universitäts-Großküchen, die für die Nahrungszubereitung jodiertes Speisesalz immer (Mensa A) oder nie (Mensa B) verwendeten, wurden 15 möglichst gleiche Mittagessen gesammelt und auf ihre Gehalte an Jodid und NaCl analysiert. Bei durchschnittlich ähnlichem Kochsalzgehalt enthielt das Essen in Mensa A im Mittel 6,1 µg I/100 g ww (8,5 µg I/g NaCl) mehr Jod als in Mensa B. Die Gesamtjodaufnahme mit einem durchschnittlichen Mittagessen in Mensa A betrug demnach 56,5±24,1 µg (Mensa B: 17,0±9,9 µg). Dem Einsatz von jodiertem Speisesalz in der Gemeinschaftsverpflegung scheint somit eine wichtigere Rolle auf dem Weg zu einer ausreichenden Jodaufnahme zuzukommen als bisher angenommen wurde.
    Notes: Summary In each of two university canteens differing in the use (canteen A) or non-use (canteen B) of iodized salt for food preparation, 15 mostly equal lunch meals were collected for iodide and NaCl analysis. With similar NaCl content, the meals of canteen A contained on average 6.1 µg I/100 g ww (8.5 µg I/g NaCl) more I than the meals of canteen B. Total I intake by consumption of an average meal of canteen A was estimated as 56.5±24.1 µg (canteen B: 17.0±9.9 µg). Consequently, the use of iodized salt in central catering seems to play a more important role in a sufficient I intake than assumed so far.
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  • 62
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    European journal of nutrition 34 (1995), S. 284-292 
    ISSN: 1436-6215
    Keywords: Human placenta ; brush border membrane ; alanine transport ; group specific reagents ; SH-groups ; Alanintransport ; menschliche Plazenta ; Kinetik ; gruppenspezifische Reagentien ; SH-Gruppen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Transportsysteme in der apikalen Zellmembran der Syncytiothrophoblasten der Plazenta sind für den Nährstoff-transport aus dem mütterlichen Kreislauf in den fetalen Stoffwechsel von elementarer Bedeutung für Wachstum und Entwicklung des Fötus. Die Carriersysteme für Aminosäuren limitieren dabei die Versorgung des Fötus mit essentiellen und nicht essentiellen Aminosäuren. An isolierten Bürstensaummembranvesikeln (BBMV) reifer menschlicher Placenta haben wir die Aufnahme von neutralen Aminosäuren am Beispiel von Alanin charakterisiert. Darüber hinaus wurden durch den Einsatz gruppenspezifischer Reagentien wichtige Aminosäureseitengruppen der entsprechenden Transportproteine identifiziert. Die Alaninaufnahme in die BBMV wird durch zwei sättigbare Carriersysteme mit unterschiedlichen Eigenschaften vermittelt. Neben einem elektrogenen Na+-abhängigen System, das auch Gln, meAIB und Met transportiert, existiert ein Na+-unabhängiges System, das kein meAIB, dafür aber zusätzlich Leu und Tyr transportiert. Beide Transportsysteme haben gleiche Affinitätskonstanten (Km-Werte) für Alanin (0,45±0,06 mmol/l). Das Na+-abhängige System transportiert Alanin mit einer 1:1 Stöchiometrie mit Na+-Ionen und weist eine 3fach höhere maximale Transportgeschwindigkeit auf. Durch Einsatz gruppenspezifischer Reagentien wurden freie SH-Gruppen in den beiden Carriern identifiziert, die für die Funktion von entscheidender Bedeutung sind. Durch Oxidation und Rückreduktion der SH-Gruppen konnte die Transportleistung der Carrier reversibel verändert werden. Da die modifizierenden Reagentien die SH-Gruppen auch in Gegenwart der Substrate blockierten, ist zu vermuten, daß die wichtigen SH-Gruppen nicht in der Substratbindungsstelle der Transportproteine liegen.
    Notes: Summary We have determined the kinetic characteristics of alanine transport into brush border membrane vesicles (BBMV) of human full term placenta and identified functional groups of the carrier proteins that are important for transport function. Alanine influx into BBMV was found to be mediated by two transport systems with different kinetic features and distinct substrate specificities. An uphill operating electrogenic Na+-dependent contransport system could be kinetically separated from a Na+-independent facilitated diffusion system. The Na+-dependent transporter mediates Na+-alanine cotransport with a 1:1 flux coupling ratio (Hill coefficient 1.13±0.12) and a Km for alanine of 0.45±0.06 mmol/l. Halfmaximal stimulation of Na+-dependent alanine influx was observed at a Na+ concentration (NaCl) of 51.4±1.3 mmol/l. A variety of group specific reagents were used to identify functional groups in the transport proteins. Only compounds reacting with SH-residues (NEM, DTNB, PCMBS) or NH2-groups (PITC) were found to affect Na+ dependent and Na+ independent alanine transport. The EC50 value for inhibition of alanine influx by PCMBS was 450±48 µmol/l. Chemical modifications of SH-groups by PCMBS caused a significant reduction (p〈0.005) in the Vmax for Na+-dependent alanine influx from 0.57±0.06 to 0.16±0.05 nmol·mg protein−1·10s−1 without affecting significantly the Km value. Inhibition by PCMBS was reversed by treatment of BBMV with DTT. When the substrate binding site of the transporter was protected by alanine or leucine, PCMBS still blocked transport function, indicating that the cruical SH groups are not located within the substrate binding site of the transport proteins.
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  • 63
    ISSN: 1436-6215
    Keywords: Sardinen ; Diäten mit Cholesterol bereichert ; Cholesterolspiegel ; Serumtriglyceride ; Olivenöl ; Sonnenblumenöl ; Fried sardines ; cholesterol-enriched diets ; serum cholesterol ; serum triglycerides ; olive oil ; sunflower oil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary The effect of diets containing olive-oil-fried sardines (diet 1) or sunflower-oil-fried sardines (diet 3) upon the serum cholesterolraise induced by dietary cholesterol was studied after a 4-week experiment in growing Wistar rats. Results of diet 1 were compared to those obtained in diets containing casein plus olive oil (diet 2), whereas results of diet 3 were compared to those obtained with casein plus sunflower oil (diet 4). All diets contained cholesterol and bovine bile as a cholesterol-raising agent. The hypercholesterolemic effect of dietary cholesterol in fried-sardine groups (a total cholesterol (TC) increase of 0.9 mmol/L (p〈0.05 and 0.4 mmol/L (not significant) in groups 1 and 3, respectively) was markedly lower than in groups 2 and 4 (a TC increase of 13.9 mmol/L (p〈0.01) and 18.2 mmol/L (p〈0.01), respectively). Serum triglyceride levels decreased in fried-sardine diets (p〈0.05) while they increased in casein diets (p〈0.05). HDL-cholesterol levels appear lower in diet 1 than in diet 2 (p〈0.05), but similar in diets 3 and 4. However, HDL-fraction carries in diets 1, 2, 3 and 4, 13 %, 4 %, 53 % and 5 % of TC, respectively. Results showed that fried-sardine diets exert a powerful check effect on the cholesterol-raising effect induced by dietary cholesterol.
    Notes: Zusammenfassung In Versuchen von 4 Wochen Dauer wurde der Einfluß cholesterolangereicherter Diäten, die in Olivenöl (Diät 1) oder in Sonnenblumenöl (Diät 3) gebratene Sardinen enthielten, auf die Erhöhung des Cholesterolspiegels bei wachsenden Wistar Ratten untersucht. Die Ergebnisse von Diät 1 wurden mit denen von Diät 2 (Kasein plus Olivenöl) und die Resultate von Diät 3 mit denen von Diät 4 (Kasein plus Sonnenblumenöl) verglichen. Alle Diäten enthielten Cholesterol und Rindergalle als cholesterolerhöhende Agentien. Der hypercholesterolämische Effekt war in den Diäten mit den gebratenen Sardinen (eine Erhöhung des Cholesterolspiegels (TC) von je 0.9 mmol/L (p〈0.05) und 0.4 mmol/L (nicht signifikant) in den Gruppen 1 und 3) auffallend kleiner als in den Kontrollgruppen 2 und 4 mit Kasein (eine Erhöhung des TC von je 13.9 mmol/L (p〈0.01) und 18.2 mmol/L (p〈0.05)). Die Serumtriglyceride fielen bei Aufnahme der Sardinen (p〈0.05) und stiegen bei Aufnahme der Kasein-Diäten (p〈0.05). Das HDL-Cholesterolgehalt war niedriger mit Diät 1 als mit Diät 2 (p〈0.05) aber ähnlich bei den Diäten 3 und 4. Die HDL-Fraktion betrug in den Diäten 1, 2, 3 und 4 je 13 %, 4 %, 53 % und 5 % des TC. Diese Ergebnisse zeigen, daß Diäten mit gebratenen Sardinen eine große Hemmwirkung auf den cholesterolerhöhenden Effekt des Cholesterols haben.
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    European journal of nutrition 34 (1995), S. 277-283 
    ISSN: 1436-6215
    Keywords: Selen ; Glutathion-Peroxidase ; Schilddrüsenhormone ; Thyroxin ; Triiodthyronin ; Typ-I-Deiodase ; Selenium ; glutathione peroxidase ; thyroid hormones ; thyroxine ; triiodothyronine ; type-I-deiodinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary In an experiment with 72 male weanling Sprague Dawley rats the effect of varying selenium intake on parameters of thyroid hormone metabolism was investigated. The animals were divided into 6 groups. One of the groups was fed a semi-synthetic diet based on casein which was poor in selenium (38 µg/kg). The other groups were fed the same diet supplemented with Na2SO3·5H2O to achieve a selenium concentration of 50, 100, 300, 600 and 3 000 µg/kg. The experiment lasted 40 days. Different selenium intake had no effect on food intake, weight gain, hematological and selected clinical-chemical parameters. Determination of glutathione peroxidase activity and selenium concentration of serum showed a selenium deficiency in animals fed the diet not supplemented with selenium. Serum T3 concentration and hepatic type-I-deiodinase activity were decreased in the group without selenium supplementation in contrast to the groups fed diets adequate in selenium (100, 300 µg/kg). A diet supplementation of 50 µg/kg already increased hepatic type-I-deiodinase activity to levels of the groups fed diets adequate in selenium. In groups supplemented with 600 and 3 000 µg/kg diet, serum T3 concentration was reduced by half of groups fed diets adequate in selenium. Supplementation with 3 000 µg Se/kg lowered the type-I-deiodinase activity in contrast to groups fed diets adequate in selenium, but not significantly. Serum concentrations of T4 and fT4 were not changed by various selenium intake. The results of this investigation show an alteration in thyroid hormone metabolism at low selenium intake as well as at high selenium intake.
    Notes: Zusammenfassung Die Auswirkungen einer unterschiedlichen Selenversorgung auf Parameter des Stoffwechsels der Schilddrüsenhormone sollten in einem Versuch mit 72 männlichen wachsenden Sprague Dawley Ratten untersucht werden. Die Tiere wurden in 6 Gruppen eingeteilt, wovon eine Gruppe eine selenarme halbsynthetische Diät auf Caseinbasis mit einem Se-Gehalt von 38 µg/kg erhielt. Die übrigen Gruppen erhielten die selbe Diät, die durch Zulage von Na2SO3·5H2O auf Selengehalte von 50, 100, 300, 600 und 3 000 µg/kg gebracht wurde. Die Versuchsdauer betrug 40 Tage. Die unterschiedliche Zufuhr von Selen hatte keinen Einfluß auf Futteraufnahme, Entwicklung der Lebendmasse, hämatologische und ausgewählte klinisch-chemische Parameter. Ein Selenmangel bei der Gruppe, die die nicht supplementierte Basisdiät erhalten hatte, konnte anhand der Aktivität der Glutathion-Peroxidase und der Selenkonzentration im Serum diagnostiziert werden. Beide Parameter stiegen ab einer Se-Zulage von 300 µg/kg noch an, allerdings geringfügig. Die Konzentration von T3 im Serum und die Aktivität der Typ-I-Deiodase in der Leber der Gruppe ohne Selenzulage war im Vergleich zu den bedarfsgerecht (100, 300 µg/kg) versorgten Gruppen vermindert. Bereits eine Selenzulage von 50 µg/kg Diät konnte die Aktivität der Typ-I-Deiodase auf die Werte der bedarfsgerecht versorgten Gruppen mit 100 und 300 µg Selenzulage anheben. Bei den Gruppen mit 600 und 3 000 µg/kg Diät Selenzulage war die Konzentration von T3 im Serum im Vergleich zu den bedarfsgerecht versorgten Gruppen auf etwa die Hälfte reduziert. Durch die Selenzulage von 3 000 µg/kg Diät war die Aktivität der Typ-I-Deiodase gegenüber den bedarfsgerecht versorgten Gruppen vermindert, die Verminderung war jedoch nicht statistisch signifikant. Die Konzentrationen von T4 und fT4 waren durch die unterschiedliche Selenzufuhr kaum verändert. Die Untersuchung zeigt insgesamt, daß sowohl unzureichende als auch über den Bedarf hinausgehende Selenzufuhr zu Veränderungen im Stoffwechsel der Schilddrüsenhormone führt.
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    European journal of nutrition 34 (1995), S. 1-1 
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    Source: Springer Online Journal Archives 1860-2000
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    European journal of nutrition 34 (1995), S. 30-31 
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    Source: Springer Online Journal Archives 1860-2000
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  • 67
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    European journal of nutrition 34 (1995), S. 113-117 
    ISSN: 1436-6215
    Keywords: Blei ; Cadmium ; Quecksilber ; Gewürze ; Gewürzzubereitungen ; Wurstwaren ; Lead ; cadmium ; mercury ; spices ; condiments ; meat products
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary The lead and cadmium contents of 50 spices and 19 condiments were investigated by means of flameless atomic absorption spectrophotometry. Mercury contents were determined by cold vapor atomic absorption method including amalgamation. The mean concentrations of lead, cadmium, and mercury were 0.470 mg/kg, 0.080 mg/kg, and 0.005 mg/kg, respectively. By using the detected levels of these three heavy metals in model calculations only a small carry-over of lead, cadmium, and mercury in meat products by spices and condiments can be assumed.
    Notes: Zusammenfassung 50 Gewürze und 19 Gewürzzubereitungen wurden mittels flammenloser Atomabsorptionsspektrometrie auf ihren Blei- und Cadmiumgehalt sowie mittels Kaltdampftechnik und nachfolgender Amalgamierung auf ihren Quecksilbergehalt untersucht. Im Mittel wurden hierbei 0,470 mg Blei, 0,080 mg Cadmium und 0,005 mg Quecksilber pro kg Würzmittel gefunden. Anhand von Modellrechnungen wurde ein nur geringer Blei-, Cadmium- und Quecksilbereintrag über Würzmittel in die Wurstsorten Fleischwurst, Leberwurst und Mettwurst aufgezeigt.
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  • 68
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    European journal of nutrition 34 (1995), S. 137-142 
    ISSN: 1436-6215
    Keywords: Taurine ; plasma ; whole blood ; depletion ; supplementation ; Taurin ; Plasma ; Gesamtblut ; Taurinmangel ; Supplementation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Die vorliegende Studie untersuchte die Beziehung zwischen der Taurinkonzentration in Plasma und Gesamtblut unter normalen physiologischen Bedingungen bei Menschen und bei Katzen sowie nach oraler Taurinsupplementierung beim Menschen und nach taurinfreier Fütterung bei Katzen. Beim Menschen betrug die durchschnittliche Taurinkonzentration im Plasma 44±8 µmol/L und im Gesamtblut 222±35 µmol/L. Unter diesen „physiologisch normalen“ Bedingungen bestand zwischen der Taurinkonzentration in Plasma und Gesamtblut keine Korrelation (r=0.092). Die Plasmataurinkonzentration stieg nach oraler Taurinsupplementierung beim Menschen rasch an bzw. fiel schnell nach taurinfreier Ernährung bei Katzen ab. Die Taurinkonzentration im Gesamtblut war dagegen mehr inert und änderte sich erst nach anhaltender Taurinzufuhr beim Menschen bzw. nach andauerndem Taurinmangel bei Katzen.
    Notes: Summary In the present study the relationship between plasma and whole blood taurine was examined under normal physiological circumstances in humans and cats. In addition, the effect of taurine supplementation on plasma and whole blood taurine was evaluated in humans and the depletion of taurine pools after a taurine-deprived diet was studied in cats. The normal plasma taurine concentration in humans was 44±8 µmol/L and the whole blood taurine concentration was 227±35 µmol/L. Under normal physiological conditions plasma and whole blood taurine were not correlated (r=0.092). Plasma taurine responded rapidly to dietary supplementation in humans or the taurine depletion in cats. In contrast, the whole blood taurine pool was more inert and varied only under extremes of depletion (cats) or sustained taurine supplementation.
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  • 69
    ISSN: 1436-6215
    Keywords: Strontium ; oraler Strontium-Test ; Calcium ; Absorption ; gesunde Probanden ; Strontium ; oral strontium test ; calcium ; absorption ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary Intestinal strontium absorption has been discussed recently as an indirect measure for calcium uptake. Prerequisite for the clinical use of an oral strontium test is the availability of a reliable procedure including controlled strontium supply, sample pretreatment and analysis as well as the assessment of normal values. In the present study, a group of young females (n=33; 24.0 ± 2.7 y; BMI 21.5 ± 1.9) received an oral dose of 2.27 mmol strontium in a standardized breakfast that contained 0.625 mmol calcium. Before and 220 min after the bolus serum strontium concentrations were determined by means of atomic absorption spectrophotometry (coefficient of variation: within day 4.8 %, n=10; day-to-day 9.5 %, n=8). The error of the method was 2.7 %. Calculation of the fractional strontium absorption rate considered the respective distribution volume (extracellular fluid; either estimated using body weight or determined by means of bioimpedance analysis [BIA]). Average absorption rates were 13.3 ± 3.1 % and, considering BIA measurement 13.6 ± 2.6 %, respectively. Smoking, exercise and, use of oral contraceptives showed no effects. Our oral strontium test is characterized by excellent reliability, easy handling and low costs and, thus, is suitable for routine use.
    Notes: Zusammenfassung Die Erfassung der Strontiumabsorption wird heute als indirektes Verfahren zur Beurteilung der intestinalen Calciumabsorption diskutiert. Voraussetzung für die klinische Anwendung ist ein vertrauenswürdiges Testverfahren inclusive kontrollierter Strontiumgabe, Probenaufarbeitung und -analyse sowie die Erfassung von Normalwerten. Für unsere Studien wurde ein Kollektiv junger Frauen (n=33, 24,0 ± 2,7 Jahre; BMI 21,5 ± 1,9) herangezogen. Die Probandinnen erhielten eine Bolusgabe von 2,27 mmol Strontium zusammen mit einem Standardfrühstück (ca. 0,625 mmol Calcium). Vor und 220 min nach der Bolusgabe erfolgte die Bestimmung des Serum-Strontiumgehaltes mittels Atomabsorptionsspektrometrie. Der Variationskoeffizient der Methode lag innerhalb eines Tages bei 4,8 % (n=10) und von Tag zu Tag 9,5 % (n=8). Der Fehler der Methode betrug 2,7 %. Die Berechnung der fraktionellen Strontiumabsorptionsrate erfolgte unter Berücksichtigung des entsprechenden Verteilungsraumes (Extrazellulärflüssigkeit; Schätzverfahren über Körpergewicht bzw. Bioimpedanz-Analyse [BIA]). Die Strontiumabsorptionsrate lag im Mittel bei 13,3 ± 3,1 %, unter Berücksichtigung der BIA-Werte bei 13,6 ± 2,6 %. Rauchen, sportliche Aktivität bzw. Einnahme oraler Kontrazeptiva zeigten keinen Einfluß. Das hier vorgestellte Testverfahren ist aufgrund seiner hohen Vertrauenswürdigkeit und relativ einfacher Handhabung für Routine-untersuchungen geeignet.
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    European journal of nutrition 34 (1995), S. 214-219 
    ISSN: 1436-6215
    Keywords: Amylin ; food intake ; vagotomy ; circadian effect ; rat ; Amylin ; Futteraufnahme ; Vagotomie ; zirkadiane Effekte ; Ratte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Das aus dem Pankreas stammende Peptid Amylin (1 µg/kg) reduzierte nach intraperitonealer (IP) Injektion die kumulative Futteraufnahme bei Ratten, denen vor der Injektion das Futter für 24 h entzogen worden war bzw. bei Ratten, denen Futter ad lib. zur Verfügung stand, für bis zu 4 h. Der Effekt trat zu verschiedenen Zeitpunkten des Tag/Nacht-Zyklus (Beginn der Dunkelphase, Mitte der Dunkelphase, Beginn der Hellphase) auf. Der verzehrsreduzierende Effekt von IP verabreichtem Amylin wurde zu keinem dieser Zeitpunkte durch subdiaphragmatische Vagotomie aufgehoben. Vagotomie führte eher zu einer Verstärkung des verzehrsreduzierenden Effekts von Amylin, und zwar nach einem 24stündigen Futterentzug bei Injektion zu Beginn der Hellphase oder in der Mitte der Dunkelphase. Im Unterschied zu früheren Untersuchungen mit älteren Ratten konnte ein verzehrsreduzierender Effekt von Amylin auch bei Ratten beobachtet werden, denen vor der Injektion das Futter nicht entzogen worden war. In Ergänzung früherer Befunde zeigen also die Ergebnisse, daß der verzehrsreduzierende Effekt von IP verabreichtem Amylin zu verschiedenen Tageszeiten ausgelöst und durch subdiaphragmatische Vagotomie nicht aufgehoben werden kann.
    Notes: Summary The pancreatic peptide amylin (1 µg/kg) injected intraperitoneally reduced cumulative food intake for up to 4 h in food-deprived (24 h) and non-deprived rats at various times of the day, i.e., at dark onset, in the middle of the dark phase, and at light onset. At none of these times did subdiaphragmatic vagotomy abolish the anorectic effect of amylin. Rather, vagotomy enhanced, by unknown mechanisms, amylin's anorectic effect in food-deprived rats at light onset and in the middle of the dark phase. In contrast to previous studies with older rats, amylin's anorectic effect was also observed when injected into nondeprived rats. The findings of the present study extend previous reports in that amylin's anorectic effect, not being abolished by abdominal vagotomy after intraperitoneal injection, can be elicited at different times of the day.
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    European journal of nutrition 34 (1995), S. 236-239 
    ISSN: 1436-6215
    Keywords: Verpflegungsplanung ; Krankenhausverpflegung ; Diabetesdiät ; Speisenauswahl ; wissensbasiertes System ; Menu planning ; hospital menu ; diabetes diet ; food selection ; knowledge-based system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary Menu planning in hospitals is a complex decision problem. Patients expect the menu plan to be healthful and in accordance with their nutritional habits. Furthermore, the menu plan must conform to capacity limits of the kitchen. In this paper we present an approach to computerized food selection and menu composition. The model is based on nutritional knowledge, which is represented in the computer and used for problem solving.
    Notes: Zusammenfassung Die Planung einer Krankenhausverpflegung stellt sich als komplexes Entscheidungsproblem dar. Die Verpflegung soll der Gesundheit der Patienten zuträglich sein, deren Ernährungsgewohnheiten entsprechen und im Rahmen der Küchenkapazität hergestellt werden können. In der vorliegenden Arbeit wird am Beispiel der Diätverpflegung für Diabetiker ein computerunterstütztes Modell vorgestellt, das den Entscheidungsträgern im Krankenhaus Hilfestellung bei der Auswahl der Speisen und deren Zusammenstellung zu Menüs bietet. Die Planung erfolgt auf der Basis ernährungs- und haushaltswissenschaftlichen Fachwissens, das im Computer abgebildet und zur Problemlösung genutzt wird.
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    European journal of nutrition 34 (1995), S. 32-33 
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  • 73
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    European journal of nutrition 34 (1995), S. 34-34 
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    European journal of nutrition 34 (1995), S. 95-112 
    ISSN: 1436-6215
    Keywords: Ernährungsgeschichte ; Nahrungsgewohnheiten ; Ernährungspolitk ; Lebensmittelverfälschungen ; Lebensmittelrecht ; Food history ; food habits ; food policy ; food adulterations ; food legislation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary During the last two decades, there has been an increasing movement in Germany to protect the natural environment from dangerous substances. This has renewed a growing common interest in government food control. This contribution ask the question of how this food legislation as a part of the general food and health policy in Germany came into being, and which promoting as well as inhibiting determinants in this scope could be observed. These statements are based partly on results of a project of the German National Research Council (Deutsche Forschungsgemeinschaft) in which the author investigates the change of food habits under the impact of industrialization and urbanization since the last century in a larger historical perspective and in a quantitative and qualitative manner with the help of current sources.
    Notes: Zusammenfassung Die in den letzten beiden Jahrzehnten in Deutschland angewachsene Bewegung zum Schutz der natürlichen Ressourcen und der verstärkten Reinerhaltung der Umwelt vor gefährlichen Schadstoffen hat auch die staatliche Lebensmittelüberwachung wieder stärker in den Brennpunkt des öffentlichen Interesses gerückt. Der Beitrag geht der bisher nur unzureichend behandelten Frage nach, wie diese gesetzliche Lebensmittelkontrolle als Bestandteil staatlicher Ernährungs- und Gesundheitspolitik in Deutschland entstanden ist und welche beschleunigenden und hemmenden Determinanten es dabei gegeben hat. Die Ausführungen basieren auf Teilergebnissen eines neuen Projekts der Deutschen Forschungsgemeinschaft, mit dem der Verfasser den Wandel der Nahrungsgewohnheiten unter dem Einfluß der Industrialisierung und Urbanisierung seit dem vorigen Jahrhundert erstmals im größeren historischen Zusammenhang anhand der überlieferten zeitgenössischen Quellen quantitativ wie qualitativ analysiert.
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    European journal of nutrition 34 (1995), S. 151-159 
    ISSN: 1436-6215
    Keywords: Fischöl ; Hyperlipoproteinämie ; Omega-3-Fettsäuren ; Triglyzeride ; Vitamin E ; Fish oil ; hyperlipoproteinemia ; omega-3 fatty acids ; triglycerides ; vitamin E
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary In 56 patients with HLP (40 with hypertriglyceridemia and mixed HLP respectively and 16 with hypercholesterolemia), changes in the lipid state and in the parameters of the antioxidative potential before and after a 4-week olive-oil phase, and after 8-, 20-and 32-week intakes of salmon-oil capsules were determined. The treatment with salmon-oil led to a decrease of triglycerides in patients with hypertriglyceridemia and mixed HLP respectively, on the other hand, it led to an increase of cholesterol in hypercholesterolemia. The increase of malondialdehyde as measure of lipid peroxidation in both patient groups underlines the necessity of a substitution of antioxidants. Further investigations are necessary before wide use of fishoil capsules can be recommended, expecially to avoid side-effects.
    Notes: Zusammenfassung Bei 56 Patienten mit HLP (40 Hypertriglyzeridämie bzw. mixed HLP und 16 mit Hypercholesterinämie) wurden Veränderungen im Lipidstatus und bei Parametern des antioxidativen Potentials vor und nach einer vierwöchigen Olivenölphase und nach 8, 20 und 32 Wochen Einnahme von Lachsölkapseln ermittelt. Die Behandlung mit Lachsöl führte bei Patienten mit Hypertriglyzeridämie/mixed HLP zu einer Senkung der Triglyzeride, dagegen bei Hypercholesterinämie zu einer Zunahme des Cholesterins. Die Erhöhung des Malondialdehyds als Maß für die Lipidperoxidation in beiden Patientengruppen unterstreicht die Notwendigkeit einer Substitution mit Antioxidantien. Vor einem breiten Einsatz von Fischölkapseln sind allerdings weitere Untersuchungen, nicht zuletzt zur Verringerung der Nebenwirkungen, erforderlich.
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    European journal of nutrition 34 (1995), S. 143-150 
    ISSN: 1436-6215
    Keywords: Fischöl ; Olivenöl ; Sauen ; Energiebilanz ; Thermogenese ; Gaswechsel ; Fish oil ; olive oil ; sows ; energy balance ; thermogenesis ; gaseous exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary An animal model experiment was conducted with nine adult sows to study the effect of olive oil and fish oil (40 % polyunsaturated fatty acids) on thermogenesis compared to wheat starch as control. The treatments were given to each animal according to a latin square design. The basal diet (20 g DM/kg W0.75) was mainly based on barley and soybean meal, and matched 60 % of the ME requirements with all the other nutrients meeting maintenance requirements. The isoenergetic supplements amounted to 176 kJ gross energy per kg W0.75 and day. During each experimental period a complete energy balance was recorded for each animal using indirect calorimetry technique (RQ-method) as well as the carbonnitrogen-balance technique. The treatments did not influence the digestibility of the rations. Digestibility of energy and of carbon averaged 83.4 % and 83.3 %, respectively. All three supplements were nearly completly digested as calculated by the difference method. Fish oil increased urine energy and decreased CH4 production, the shifts, however, were in absolute terms very small. The mean O2 consumption was 1 002 l/d showing no significant treatment effects. CO2 production was lowered with olive oil by 10 %, and with fish oil by 13 % compared to the starch diet. The daily heat production was 20.95, 20.72, and 20.04 MJ when starch, olive oil or fish oil was given. Corrected for equal energy retention the difference of thermogenesis between olive oil and starch was −0.4 MJ/d, and between fish oil and starch −1.2 MJ/d. These differences corresponded to a relation of starch:olive oil:fish oil=1:0.95:0.86. The relation between starch and olive oil reflected exactly the theoretical expectation, calculated from the ATP regeneration by oxidation of both nutrients. When fish oil was added, the daily heat production was lower than theoretically calculated, which might be interpreted as an effect on the metabolic rate in general rather than especially on the efficiency of ATP formation from fish oil oxidation. In any case, there was no hint of a facultative thermogenesis induced by the oils.
    Notes: Zusammenfassung Mit Hilfe der kalorimetrischen Bilanztechnik wurde an 9 Sauen nach dem Schema eines lateinischen Quadrates die Wirkung von Olivenöl und Fischöl im Vergleich zu Weizenquellstärke auf die Thermogenese im Erhaltungsstoffwechsel gemessen. Die zu prüfenden Nährstoffe wurden einer Basisration (20 g TM/kg W0,75) zugelegt, die auf 60 % des energetischen Erhaltungsbedarfs an umsetzbarer Energie ausgerichtet war. Die isoenergetischen Zulagen betrugen jeweils 176 kJ Bruttoenergie/kg W0,75. Von allen Tieren wurde in jeder Stoffwechselperiode eine vollständige Energiebilanz erfaßt. Die Versuchsbehandlung hatte keinen Einfluß auf die Verdaulichkeit der Rationen. Die mittleren VQ-Werte der Gesamtration betrugen 83,4 % für Energie und 83,3 % für Kohlenstoff. Die Energieverdaulichkeit der Zulagen betrug in allen Fällen um 100 %. Fischöl erhöhte signifikant die Harnenergie und verminderte die CH4-Bildung im Vergleich zu den beiden anderen Rationen. Allerdings waren diese Veränderungen absolut gesehen nur minimal. Der Sauerstoffverbrauch betrug im Mittel 1002 l/d und zeigte keine Behandlungsdifferenzen. Die CO2-Abgabe war bei Verabreichung von Olivenöl um 10 % und bei Fischöl um 13 % signifikant niedriger. Die tägliche Wärmebildung betrug 20,95, 20,72 bzw. 20,04 MJ bei Fütterung der Rationen mit Stärke, Olivenöl bzw. Fischöl. Auf der Basis gleicher Energieretention verglichen, betrug der Unterschied in der Thermogenese zwischen Olivenöldiät und Stärkediät −0,4 MJ/d, der zwischen Fischöldiät und Stärkediät −1,2 MJ/d. Dies entsprach einer Relation von Stärke:Olivenöl:Fischöl=1:0,95:0,86. Das Verhältnis zwischen Stärke:Olivenöl widerspiegelte genau die theoretische Erwartung aufgrund der ATP-Regenerierung durch Oxidation dieser beiden Nährstoffe. Fischöl (ca. 40 % mehrfach ungesättigte Fettsäuren) wies eine tendenziell niedrigere Thermogenese als theoretisch erwartet auf, was möglicherweise auf einer entsprechenden Absenkung des Erhaltungsumsatzes beruhte. Die Ergebnisse zeigen, daß die verwendeten Öle keine fakultative Thermogenese induzierten.
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    European journal of nutrition 34 (1995), S. 183-189 
    ISSN: 1436-6215
    Keywords: Validation ; 24-hour recall questionnaire ; dietary survey ; energy intake ; nutrient intake ; food intake ; Validierung ; 24-hour-recall-Fragebogen ; Ernährungserhebung ; Energieaufnahme ; Nährstoffaufnahme ; Nahrungsaufnahme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Ziel der Arbeit war, die relative Validität eines selbstgeführten 24-hour-recall-Fragebogens zu untersuchen, der in einer Ernährungserhebung mit 3 653 weiblichen und männlichen Erhebungsteilnehmern im Alter ab 7 Jahren eingesetzt wurde. Die Validierung wurde an einer Gruppe von 41 Männern durchgeführt. Ein 3-Tage-Protokoll diente als Referenzmethode. Der Vergleich des 24-hour-recall-Fragebogens mit dem 3-Tage-Protokoll erbrachte gute Übereinstimmung. Mittels des Wilcoxon matched-pairs ranked signs test (p〈0.05) konnten nur für die absoluten Energie- und Kohlenhydrataufnahmen sowie für die Protein-Nährstoffdichte signifikante Unterschiede nachgewiesen werden. Die prozentuale Verteilung der Energie auf die Hauptnährstoffe und Alkohol differierte um maximal 2,4 %. Der mediane prozentuale Unterschied in der absoluten Nährstoffaufnahme und der Nährstoffdichte lag zwischen −9 und 22 %. Die tägliche Nahrungsaufnahme war nur für 3 von 10 Lebensmittelgruppen signifikant verschieden. Die Spearman rank Korrelationskoeffizienten betrugen für alle Nährstoffdichten mehr als 0,35. Die höchsten Korrelationskoeffizienten um 0,60 wurden für die Alkoholund Nahrungsfaseraufnahme beobachtet. Die Ergebnisse zeigen, daß der 24-hour-recall-Fragebogen eine valide Methode zur Schätzung der medianen und mittleren Nahrungs-und Nährstoffaufnahme von großen Gruppen ist.
    Notes: Summary This study investigated the relative validity of a self-administered 24-h recall questionnaire in a dietary survey on 3 653 men and women 7 years of age and older. The validation was carried out in a group of 41 men. An estimated dietary record kept over 3 days served as reference method. Comparison of the questionnaire and the estimated 3-day record showed good agreement. The Wilcoxon matchedpairs ranked signs test (p〈0.05) demonstrated that the only differences were the crude energy and carbohydrate intake and the estimated nutrient density of protein. The estimated proportion of calories from carbohydrate, fat, protein, and alcohol differed by no more than 2.4 %. The median percentage differences in crude nutrient intakes and nutrient densities between the two assessment techniques ranged from −9 % to 22 %. The daily food intake differed significantly in only three of ten food groups. Spearman's correlation coefficients were higher than 0,35 for all density measurements. The highest correlation coefficients of about 0.60 were observed for alcohol and dietary fiber intake. It is concluded that the self-administered 24-hour recall questionnaire is a valid method for estimating the median and mean dietary intake of large groups of subjects.
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    European journal of nutrition 34 (1995), S. 198-205 
    ISSN: 1436-6215
    Keywords: Forelle ; Tocopherol ; Phyllochinon ; Antioxidans ; Lipidstabilität ; Trout ; tocopherol ; phylloquinone ; antioxidant ; storage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary Rainbow trouts were fed a complete diet with 12 mg vitamin K3 and supplemented with 20, 200 or 2 000 mg all-rac-α-tocopheryl-acetate/kg for 18 weeks. The ratio of the vitamin E-supplementation was 1 : 10 : 100. Fillets were minced and stored at −18 °C. Concentrations of α-tocopherol and phylloquinone and parameters of lipid peroxidation were measured after 4, 6, and 8 months of storage. The effects of α-tocopherol incorporated into fillets on storage stability were assessed by measuring free fatty acids, peroxides, malondialdehyde and lipofuscin. Mean α-tocopherol-concentrations in fillets were 1.4, 2.7 and 16.3 mg/100 g, respectively representing ratios of 1 : 2 : 12. The increase in α-tocopherol concentration resulted in a significant improvement of storage stability. The phylloquinone concentration in fillet was reduced in treatments with ≥200 mg vitamin E/kg; however, this did not affect the prothrombin time. No peroxides were detectable at any time. The concentrations of malondialdehyde significantly decreased with increasing supplementation of vitamin E. Lipofuscin concentrations were higher with low than with high vitamin E supplementation. The dose-related inhibition of lipid peroxidation became apparent in decreased concentrations of the free fatty acids in the crude fat. These results confirm the effectiveness of α-tocopherol as antioxidant in fish flesh. In this study the incorporation of α-tocopherol from dietary supplementation improved the long-term storage quality of trout fillets due to the effective inhibition of the lipid peroxidation. A measurable improvement of the storage stability was achieved with a supplementation of 200 mg vitamin E/kg feed.
    Notes: Zusammenfassung Filet von Forellen, die 18 Wochen lang ein Futter mit 12 mg Menadion/kg und mit drei im Konzentrationsverhältnis von 1 : 10 : 100 gestaffelten Dosierungen von all-rac-α-Tocopherylacetat (20, 200 und 2 000 mg/kg) erhalten hatten, wurde homogenisiert und bei −18 °C gelagert. Nach Lagerung über 4, 6 und 8 Monaten wurden die Konzentrationen an α-Tocopherol und Phyllochinon sowie von freien Fettsäuren, Peroxiden, Malondialdehyd und Lipofuszin als Parameter der Lipidperoxidation analysiert. Die mittleren α-Tocopherolgehalte betrugen 1,4; 2,7 und 16,3 mg/100 g Filet, entsprechend einem Konzentrationsverhältnis von etwa 1 : 2 : 12. Der dosisabhängige Anstieg bewirkte eine deutliche Verbesserung der Lagerstabilität. Die hohen Dosen an Vitamin E führten zu abnehmenden Gehalten an Phyllochinon im Fischmuskel, die ohne Einfluß auf die Prothrombinzeit waren. Die dosisabhängige Hemmung der enzymatisch katalysierten Fettoxidation spiegelte sich in abfallenden Gehalten an freien Fettsäuren im Rohfett wider. Peroxide waren an keinem Untersuchungstermin nachweisbar. Die Gehalte an Malondialdehyd sanken mit zunehmender Supplementierung von Vitamin E signifikant ab. Derselbe Einfluß zeigte sich bei Lipofuszin. Die Anreicherung der Filets mit α-Tocopherol nach Supplementierung des Futters begünstigte eine längerfristige Qualität bei Gefrierlagerung infolge einer effektiven Hemmung der Lipidperoxidation. Bereits mit der Dosierung von 200 mg α-Tocopherylacetat/kg Futter konnte im Vergleich zur Dosierung von 20 mg/kg eine meßbare Verbesserung der Lagerstabilität erzielt werden.
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  • 79
    ISSN: 1436-6215
    Keywords: ω-3 Fettsäuren ; Kolonkarzinom ; Diät ; Fett ; Lipoproteine ; ω-3 fatty acids ; colonic neoplasms ; diet ; fat ; lipoproteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary Several studies indicated a protective effect of fish oil on colon carcionogenesis which might be due to alterations in prostaglandin E2 synthesis of the colonic mucosa. Additional effects on fecal bile acid excretion may also play a role since especially secondary bile acids are known to act as promotors in colon cancer development. In the present study possible influences on bile acid excretion were investigated in 12 healthy volunteers whose daily diet was supplemented for 4 weeks with 11 g of fish oil (FO) and corn oil (CO) per day, respectively. Fecal bile acids were analyzed by gas-liquid-chromatography. Fecal excretion of total bile acids was not different during the periods of FO and CO-supplementation (301.9 vs. 320.3 mg/day). However, a non-significant trend to a lower daily excretion of the secondary bile acid lithocholic acid was found after FO compared to CO-ingestion (99.6 vs. 109.4 mg/day; p=0.22). Since secondary bile acids are known promotors of colon carcinogenesis, these findings may implicate a favorable situation with respect to colon cancer prevention.
    Notes: Zusammenfassung Verschiedene Studien weisen auf einen protektiven Effekt von Fischöl bei der Kolonkarzinomentstehung hin. Mögliche Einflüsse auf die muscosale Prostaglandin-E2-Synthese wurden hierbei als Wirkungsmechanismus beschrieben. Zusätzliche Effekte auf die fäkale Exkretion von Gallensäuren könnten ebenso von Bedeutung sein, da insbesondere sekundäre Gallensäuren als Promotoren bei der Kolontumorentstehung angesehen werden. In der vorliegenden Studie wurde bei 12 gesunden Probanden der Effekt einer täglichen Supplementierung mit 11 g Fischöl (FO) bzw. Maiskeimöl (MO) über jeweils 4 Wochen zusätzlich zu einer fettreduzierten Basiskost (30 % der Gesamtenergie als Fett) auf die fäkale Exkretion von Gallensäuren untersucht. Die Analyse des fäkalen Gallensäurenspektrums erfolgte gaschromatographisch. Die Gesamtausscheidung an Gallensäuren war unter FO nicht signifikant verschieden von derjenigen unter MO (301,9 vs. 320,3 mg/Tag). Unter FO ergab sich jedoch eine tendenziell niedrigere Exkretion der sekundären Gallensäure Lithocholsäure als unter MO (99,6 vs. 109,4 mg/Tag, p=0,22). Da sekundäre Gallensäuren als ein wesentlicher Promotor der Kolonkarzinogenese angesehen werden, sind diese Veränderungen positiv im Hinblick auf eine mögliche Kolonkarzinomprävention zu werten.
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    European journal of nutrition 34 (1995), S. 243-244 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
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    European journal of nutrition 34 (1995), S. 245-251 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
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  • 82
    ISSN: 1436-6215
    Keywords: Deep-fat frying ; sunflower oil ; column and HPSE chromatographies ; color index ; acid value ; UV absorption ; Ölbad-Fritierung ; Sonnenblumenöl ; Säulen- und HPSE-Chromatographie ; Farbindex ; Säurezahl ; Refraktionsindex ; UV-Absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Chemische und physikalische Standardkennzahlen, wie zum Beispiel der Refraktions-und Farbindex, die Säurezahl und der K270-Wert, wurden mit den Gehalten an polaren Verbindungen sowie spezifischen thermooxidativen und hydrolytischen Fettbestandteilen verglichen, die in einem Sonnenblumenöl, das 75 mal zum Fritieren von Kartoffeln benutzt worden war, entstanden sind. Der Farbindex, die Säurezahl, der K270-Wert und der Gehalt an polaren Verbindungen stiegen signifikant (p〈0,05) nach 30 Fritierungen. Anschließend stabilisierten sich die drei letztgenannten Indices. Der Inhalt an polymeren Verbindungen und Triglyceridendimeren stieg signifikant nach 30 Fritierungen an (p〈0,05), während die oxidierten Triglyceride keine signifikante Steigerung aufwiesen. Der Gehalt an Diglyceriden und freien Fettsäuren, als Maß der hydrolytischen Vorgänge, zeigte während des Fritierprozesses keine signifikante Veränderung. Die signifikanten Korrelationen zwischen der Säurezahl und dem Gehalt an polaren Verbindungen, den dimeren und polymeren Triglyceriden und den oxydierten Triglyceriden, zwischen dem Farbindex und dem Gehalt an polaren Verbindungen und polymeren Triglyceriden, oder zwischen dem K270-Wert und den polymeren Triglyceriden zeigen, daß diese einfachen Standard-Methoden benutzt werden können und genauso nützlich sind wie mehr spezifische Methoden zur Bewertung von Fritierprozessen, wenn man die Ausgangswerte aller dieser Indices kennt.
    Notes: Summary Standard chemical and physical indexes, such as color index, acid value, and K270 were compared with the polar content and the specific thermoxidative and hydrolytic compounds originated during 75 potato fryings with sun-flower oil. The color index, acid value, K270 and total polar content showed a significant increase (p〈0.05) after the first 30 fryings, followed by a tendency of the last three indexes to reach a near-steady state. Triglyceride polymers and triglyceride dimers showed a significant increase (p〈0.05) after 30 fryings, while the oxidized triglycerides were not increased significantly after 30 fryings. The amount of diglycerides and free fatty acids related to hydrolytic alteration did not change significantly throughout the frying operations. The significant correlations between acid value and total polar content, triglyceride dimers, triglycerides polymers and oxidized triglycerides, or between color index and polar content and triglyceride polymers or between K270 and triglyceride polymers indicate that these simple and standard methods can be applied and they are as useful as more specific methods of evaluation in the monitoring of frying operations, provided that initial values of all of these indexes are available.
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    Engineering with computers 11 (1995), S. 94-102 
    ISSN: 1435-5663
    Keywords: Rational cubic ; Bernstein-Bézier ; Shape control ; Tension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper is concerned with the problem of fitting curves and surfaces, for computer aided design (CAD), via an ordered set of control points, so that the result is satisfactory for the user's needs. Piecewise rational functions with cubic numerator and quadratic denominator are used in the construction of the scheme, in such a way that the descriptions of the parameters control the shape of the picture in the desired area. A general solution is obtained for points inN-space, although the scheme is only meaningful in the cases whereN=2 andN=3.
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    Engineering with computers 11 (1995), S. 145-156 
    ISSN: 1435-5663
    Keywords: Database ; Date fusson ; Date model ; Information architecture ; Information model ; Manufacturing ; Sensors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Data fusion is the integration and analysis of data from multiple sensors to develop a more accurate understanding of a situation and determine how to respond to it. Although data fusion can be applied in many situations, this paper focuses on its application to manufacturing and how it changes some of the more traditional, less adaptive information models that support the design and manufacturing functions. The paper consists of four parts. The first section explains what data fusion is and its impact on manufacturing. The second section describes what an information system architecture is and explains the natural language-based information modeling methodology used by this research project. The third section identifies the major design and manufacturing functions, reviews the information models required to support them, and then shows how these models must be extended to support data fusion. The fourth section discusses the future directions of this work.
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    Engineering with computers 11 (1995), S. 167-172 
    ISSN: 1435-5663
    Keywords: Concurrent engineering ; Configuration management ; Data model ; Design Process ; Engineering data management ; Product data management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract In order to make the traditional product structure tree representation amenable to concurrent engineering relationships likeperspective-of anddependent-on have to be added to the essentialpart-of relationship. Complex data can be held in proprietary formats, while simple data will be in a common representation for direct access by diverse disciplines. Coordination among team members in a project can be carried out using such a model. Besides, a virtually unified view of all the data is possible, though they may lie in distributed and heterogeneous data bases. A very necessary characteristic of such a model is that its time evolution should be easy to represent in order to reflect the dynamic nature of product development, where the model itself, and not merely the data values change. Managing versions is also facilitated by the comprehensive structure of the Unified Product Data Model (UPDM).
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    Engineering with computers 11 (1995), S. 227-245 
    ISSN: 1435-5663
    Keywords: Conceptual design ; Design process ; Design studies ; Engineering information systems ; Product data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper identifies requirements for an engineering design information management system. Future CAD systems must support a wide range of activities — such as definition, manipulation and analyses of complex product information models. These models represent not only conventional data associated with current CAD applications, but also design information characterizing the correlations between the requirements, functions, behaviors and physical form of the product. Such functionality is important for both the individual designer and the design organization, as the need to manage information as a corporate asset is becoming a critical component of business strategy. This paper explores these needs using two design studies. The first study illustrates some major concepts relative to non-routine design activities, while the second study focuses on the routine design activities relative to organization interactions. These studies were used to elicit high level requirements which serve as the basis for the development of prototype software systems. These prototypes are briefly introduced here.
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    Engineering with computers 11 (1995), S. 213-226 
    ISSN: 1435-5663
    Keywords: Communication channel ; Communication path ; Data attribute ; Design object ; Method group ; Object-oriented ; Receiving interface ; Relationship ; Relationship attribute ; Sending method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Object-oriented principles have introduced several useful concepts for developing complex software systems. As a result, several methodologies have been suggested for the overall design of software systems based on these concepts. Methodologies and frameworks for designing objects that are to be part of the software systems are currently lacking. This paper proposes anobject design framework andmethodology, which utilizes the object-oriented concepts, for planning, organizing and designing structural engineering design objects. Design objects in an integrated structural engineering system are complex and often related to each other in various different ways. The paper also identifies several important relationships among structural engineering design objects. These relationships serve as communication channels through wich design objects send messages to and receive responses from each other. Several examples, drawn from reinforced concrete structures, will be presented to demonstrate the object design methodology and to illustrate how the framework is effective in reducing the complexity of design objects in an integrated structural engineering system.
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    AI & society 9 (1995), S. 18-28 
    ISSN: 1435-5655
    Keywords: Ethics ; Science ; Technology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In the paper, three propositions are put forward. First, that intellectual structures of wide scope commonly lead to conclusions which are ethically unacceptable; secondly that the ethically unacceptable consequences of science arise from one particular presupposition which it adopts, namely that of causality; thirdly, that causality is no essential part of science.
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    AI & society 9 (1995), S. 29-42 
    ISSN: 1435-5655
    Keywords: Skills ; Deskilling ; Communication ; Control ; Privacy ; Identity ; Ethical neutrality ; Discourse ; Responsibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper first illustrates what kind of ethical issues arise from the new information, communication and automation technology. It then argues that we may embrace the popular idea that technology is ethically neutral or even ambivalent without having to close our eyes to those issues and in fact, that the ethical neutrality of technology makes them all the more urgent. Finally, it suggests that the widely ignored fact of normal responsible behaviour offers a new and fruitful starting point for any future thinking about such issues.
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    AI & society 9 (1995), S. 80-90 
    ISSN: 1435-5655
    Keywords: Computing ; Ethics ; Feminism ; Healthcare
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Value in the British National Health Service have shifted away from patient care towards financial control. However, in the quest for “efficiency”, huge amounts of NHS money have been wasted on computer system which failed. In this paper, I draw on a case study to explore some of the ethical issues which underlie this kind of waste of resources. Issues include the gap between public pronouncements and personal experience, the chaos of which lies behind the facade of rationality, and the systematic silencing of people, usually women, who question the viability of computer systems which are created for private gain rather than public service.
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  • 91
    ISSN: 1435-5655
    Keywords: User-centred design ; Allocation of function ; Expert systems ; Iteration ; Prototype
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A case study is presented of the development of computer-based support tools for power engineers in the electricity supply industry. The objective was to develop an expert system to support witching schedule production. A user-centred approach was followed which led the user community to conclude that a switching schedule production assistant (SSPA) was required which would leave control with the power engineer. Prototype systems were developed and evaluated in user trials which revealed that a significant and more general purpose tool would be a computer generated electricity network display that the engineers could manipulate. The paper concludes that the process of enabling users to evaluate alternative forms of technology can facilitate the development systems that are useful, acceptable and usable.
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  • 92
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    AI & society 9 (1995), S. 115-115 
    ISSN: 1435-5655
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    Topics: Computer Science
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  • 93
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    AI & society 9 (1995), S. 258-272 
    ISSN: 1435-5655
    Keywords: Action ; Design ; Discourse ; Innovation ; Language ; Methodology ; Tacit knowledge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This contribution to design methodology reflects upon the barriers to effectiveness imposed by our tendency to gravitate towards the over-formal in human affairs. We see a correspondingly cleaned-up description of the process of design, a failure to consider its jagged elements and to take proper account of the non-formal in knowledge (e.g. tacit knowledge) and communication. Discipline in methodology is accordingly wrongly equated with formality. The failure of design to be effective is more likely for innovative design rather than routine design. It is suggested by way of explanation that design methodology especially in the field of information technology is infused with the ghost of positivism, manifest in an unconditional belief in the value of rationality and an implied naive realist conviction about the fixed, singular and transparent nature of the environment for which design is undertaken. We need to be able to work with uncertainty rather than try for its entire elimination. A breadth of approach in carrying out the activity of design is threatened by lack of attention to the variety of forms which knowledge and corresponding forms of discourse can take. We undertake the disciplined reduction from the messy real work to metaphors tidy enough to work with, or models as they are usually misnamed. The notion of “language of struggle” is invoked as a suitable metaphor for the non-formal discourse particularly relevant to innovative design. A complementary exploration is offered of socio-linguistic space which is the common context for design. In view of the concern with social space necessary to effective design, it may be enlightening to consider the designer as applied anthropologist.
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  • 94
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    AI & society 9 (1995), S. 373-388 
    ISSN: 1435-5655
    Keywords: Hypermedia ; CSCW design ; CSCW analysis ; Synchronous ; Asynchronous ; Remote ; Co-located
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The paper presents a general critique of the use of conceptual frameworks in design, illustrated by the well known synchronous/asynchronous, co-located/non-co-located framework. It argues that while frameworks are a necessary and inevitable starting point for design, the business of tailoring and adapting them to specific situations need not be ad hoc.Triggering artefacts are a way of systematically challenging both designers' preunderstandings and the conservatism of work practice. Experiences from the Great Belt tunnel and bridge project are used to illustrate howtriggering artefacts change themodality of designing for change.
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  • 95
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    AI & society 9 (1995), S. 389-395 
    ISSN: 1435-5655
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The question whether or not computers can think was first asked in print by Alan Turing in his seminal 1950 article. In order to avoid defining what a computer is or what thinking is, Turing resorts to “the imitation game” which is a test that allows us to determine whether or not a machine can think. That is, if an interrogator is unable to tell whether responses to his questions come from a human being or from a machine, the machine is imitating a human being so well that it has to be acknowledged that these responses result from its thinking. However, then as now, it is not an indisputable claim that machines could think, and an unceasing stream of papers discussing the validity of the test proves this point. There are many arguments in favour of, as well as against, the claims borne by the test, and Turing himself discusses some of them. In his view, there are mice possible objections to the concept of a thinking machine, which he eventually dismisses as weak, irrelevant, or plain false. However, as he admits, he can present “no very convincing arguments of a positive nature to support my views. If I had I should not have taken such pains to point out the fallacies in contrary views”.
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  • 96
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    AI & society 9 (1995), S. 396-401 
    ISSN: 1435-5655
    Keywords: Software crisis ; AI software engineering ; Human-centred software design ; Kantian philosophy ; Constructivism ; Human thinking models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this article I deal with the question “How could we renew and enrich computer technology with Kant's help?”. By this I would like to invite computer scientists and engineers to initiate or intensify their cooperation with Kant experts. What I am looking for is a better “method of definition” for software systems, particularly for the development of object-oriented and knowledge-based systems. After a description of the “software crisis”, I deal first with the question why this crisis could not yet be overcome. A way out of this software crisis can be expected from systems which are adapted to the human faculty of thinking. I show which foundation is in my opinion necessary and sketch the principles according to which a “human-centred” method of definition for sych systems could be developed on that foundation with Kant's help.
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  • 97
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    Lasers in medical science 10 (1995), S. 37-42 
    ISSN: 1435-604X
    Keywords: Enamel ; Etch ; Laser ; Acid ; Nd-YAG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Acid etching is regarded as one of the main means of providing additional retention in aesthetic dentistry. Alternative methods of achieving bonding to tooth tissue which have been proposed include laser etching. Conflicting results on bond strength to enamel have been reported for laser etching. Here the tensile bond strength of composite resin to acid- and laser-etched enamel was measured and the topographical differences between the surfaces were evaluated using the scanning electron microscope. The laser used was a pulsed Nd-YAG laser at 10 pulses per second with a pulse length of 150μs, 80mJ pulse−1, 1.064μm wavelength. The results obtained indicate that the bond strength of laser-etched enamel was significantly lower than that of acid-etched enamel. In this study the difference may be attributable to the chromophore used. Variations in the rate of traverse of the laser tip across the surface did not appear to produce significant alterations in the bond strength.
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  • 98
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    Lasers in medical science 10 (1995), S. 31-36 
    ISSN: 1435-604X
    Keywords: Embryonal carcinoma ; F9 cells ; Laser ; Hyperthermia ; Nigericin ; Acidosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The aim of this study was to investigate how acidosis affects the sensitivity of F9 embryonal carcinoma cells to conventionally induced hyperthermia and Nd-YAG laser-induced laserthermia. Nigericin, a polyether ionophore, was used to reduce the intracellular pH to 6.8, while the control cells were maintained at a physiological pH of 7.4. Acidosis increased the heat sensitivity significantly. After the water bath only 75% of the acidotic F9S1 cells were viable, whereas all of the control cells at pH 7.4 survived. When the laser was used, the difference was even more pronounced. Only 9% of the acidotic cells were viable after a 2-min treatment and 0.2% after a 4-min treatment. At physiological pH a 2-min treatment left 41% of the cells viable and a 4-min treatment 2%. This study showed that laserthermia is significantly more effective in killing cells with low intracellular pH than it is in killing cells with normal intracellular pH. The core of a tumour is often acidotic and thus radioresistant. It is suggested that laserthermia could be a good choice when treating acidotic radioresistant cancer cells, and its effect as an adjuvant to radiation therapy should be investigated.
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  • 99
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    Lasers in medical science 10 (1995), S. 157-163 
    ISSN: 1435-604X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Diode lasers are now capable of delivering up to 60 W of power down thin optical fibres, and their medical applications have increased considerably over the past 5 years. Most of the recent experimental and clinical work has been performed using the 805 nm diode laser wavelength, which is more heavily absorbed and is less penetrating than the 1064 nm Nd-YAG wavelength in most tissues. In contact and non-contact mode, the overall tissue effects from the diode laser are similar to the Nd-YAG laser, but with interstitial therapy the 805 nm wavelength produces significantly greater necrosis than the 1064 nm wavelength. Experimental work has established the effectiveness of the diode laser and clinical work has confirmed its suitability for a wide variety of procedures. Diode lasers have the major advantages of being small, compact, portable, efficient, easy to use and virtually maintenance free; they are likely to replace more cumbersome lasers for many medical applications.
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  • 100
    ISSN: 1435-604X
    Keywords: Transmyocardial revascularization ; Lasers ; Coronary artery disease ; Ischaemia ; Tissue hibernation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Transmyocardial revascularization (TMR) is a puncture technique proposed as a solution for patients with coronary artery disease who cannot be efficiently treated with the standard revascularization procedures such as bypass surgery or percutaneous transluminal coronary angioplasty (PTCA). The studies presented in this review have investigated the use of lasers to revascularize ischaemic myocardium. Needle puncture methods are also briefly described. The results from experimental studies are not conclusive but the encouraging clinical reports raise further questions about the mechanism of angina relief.
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