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  • 1
    Electronic Resource
    Electronic Resource
    Videolaparoscopic cholecystectomy induces a hemostasis activation of lower grade than does open surgery (2000)
    Springer
    Surgical endoscopy and other interventional techniques 14 (2000), S. 170-174 
    Details
    ISSN: 1432-2218
    Keywords: Key words: Blood clotting activation — Open and videolaparoscopic cholecystectomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Tissue injury after trauma and surgery may induce alterations in blood coagulation and fibrinolysis, and the hypercoagulable state observed after surgery can be associated with the risk of postoperative thromboembolic complications. Recently, videolaparoscopic (VLPS) cholecystectomy has been introduced, and its advantages over the open procedure seem related to the reduced surgical trauma. The aim of this study was to investigate hemostatic system alterations in patients who undergo open and VLPS cholecystectomy. Methods: Fibrinogen, prothrombin fragment F1+2, D-dimer, and plasminogen activator inhibitor type-1 (PAI-1) activity was determined in 10 patients who underwent open (group A) and 10 patients who underwent VLPS cholecystectomy (group B), respectively. Blood samples were obtained the day of surgery in the morning (B1), after anesthesia (A1), 1 hour after the start of surgery (S1), then 30 min (E.05) and 24 h (E.24) after the surgery. Results: No significant differences were observed in baseline values between groups A and B for the parameters investigated. At 24 h after surgery, fibrinogen increased significantly (p 〈 0.05) in group A and also was significantly higher than in group B (p 〈 0.05). In group A, a marked increase in F1+2 levels (p 〈 0.01) was observed in all the samples, with the maximum values on the first day after surgery (3.7 nmol/l; 1.2–6.0 nmol/l), whereas in group B, a slight but significant increase in F1+2 levels (2.1 nmol/l; 1.1–3.9 nmol/l; p 〈 0.01) was observed only 30 min after the end of surgery. In both groups A and B, D-dimer markedly increased after surgery, without statistical significant differences between the two groups at any time. The PAI-1 activity plasma levels remained in the normal range during and after surgery in both groups. Conclusions: These results indicate that VLPS surgery induces an activation of the clotting system that, although of low degree and short duration, can lead to a transient prothrombotic state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004649900093
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  • 2
    Electronic Resource
    Electronic Resource
    Space-time finite elements for the wave propagation problem (1975)
    Springer
    Meccanica 10 (1975), S. 168-170 
    Details
    ISSN: 1572-9648
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The wave propagation problem has been traditionally approximated by finite differences, or by the Galerkin method. The latter, in a finite element contest, implies the approximation across the space variables by finite elements, and the integration of the resulting sistem of differential equations on time by finite differences. The weak, variational formulation is used only for lowering the space derivatives. The present work attempts at discretising and solving a weak formulation on space and time due to Lions [1]. The finite elements extend simultaneously on space and time. The resulting set of linear equations, however, usually outgrows by an order of magnitude in matrix size and bandwidth, the corresponding dimensions with a Galerkin method. That consideration has led to an early dismissal of the space-time approach. Assuming constant time step, the matrix takes a recursive structure, which allows for reduction of the solution of a set of linear equations of Galerkin size. A simple example of one dimensional wave propagation is solved by space-time finite elements and the results are compared with finite differences and with the Galerkin method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02149028
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  • 3
    Electronic Resource
    Electronic Resource
    A system for generalized finite elements (1972)
    Springer
    Meccanica 7 (1972), S. 41-41 
    Details
    ISSN: 1572-9648
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02128843
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  • 4
    Electronic Resource
    Electronic Resource
    Spline-blended approximation of Hartmann's flow (1974)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 8 (1974), S. 529-536 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The steady state flow problem known in magnetohydrodynamics as Hartmann's flow is converted into variational formulation and is given an approximate solution by means of the spline blended interpolation technique. The equations of motion consist of two coupled potential flow problems with homogeneous boundary conditions. The spline blended interpolation method is reduced here, because of the shape of the domain, to a cartesian product of cardinal splines with trigonometric or ordinary polynomials. ‘Exact’ boundary conditions are presented by the blending technique. The numerical results indicate that high accuracy is possible with relatively few unknowns.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620080309
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  • 5
    Electronic Resource
    Electronic Resource
    Space-time elements for the shock wave propagation problem (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1475-1488 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A space-time finite element procedure is presented that integrates on time the equations of nonlinear dynamics. When a shock occurs and subsequently propagates, the space-time procedure gives accurate and stable numerical results, without after-shock wiggling, at relatively low costs of computation.The procedure is implicit. The good performance is to be attributed to the capability of the space-time elements to cope with discontinuities in the velocity by the simple use of reduced numerical integration.The numerical solution of the Fermi-Pasta-Ulam problem is discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620151005
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  • 6
    Electronic Resource
    Electronic Resource
    Spline interpolation techniques for variational methods (1973)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 6 (1973), S. 565-576 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Interpolation techniques are reviewed in the context of the approximation of the solution of boundary value problems. From the variational formulation, the approximation error norm is related to the interpolation error norm.Among global interpolation techniques, bicubic splines and spline-blended are reviewed; among local, Hermite's and ‘serendipity’ polynomials. The corresponding interpolation error norms are computed numerically on two test functions. The methods are compared for accuracy and for number of operations required in the solution of boundary value problems. The conclusion is that spline interpolation is most convenient for regular hyper-elements, while high precision finite elements become convenient for very fine or irregular partition.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620060412
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    Paper (German National Licenses)
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