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  • 1
    Electronic Resource
    Electronic Resource
    Ergebnisse der selektiven proximalen Vagotomie mit Pyloroplastik an 464 Patienten (1976)
    Springer
    Langenbeck's archives of surgery 340 (1976), S. 179-190 
    Details
    ISSN: 1435-2451
    Keywords: Selective proximal vagotomy with pyloroplasty ; Clinical results
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Von den 464 Ulcus-duodeni- und Ulcus-ventriculi-Patienten, bei denen innerhalb von 5 Jahren eine SPV und Pyloroplastik durchgeführt wurde, wurden 438 ausgewertet. Bei 75 % der Patienten lag die Operation mehr als 2 Jahre zurück. Über 25% waren Notfalleingriffe. Intraoperative Komplikationen (Milzverletzung, Oesophagusperforation) ereigneten sich in 3,2%, postoperative Komplikationen (Nahtinsuffizienz der Pyloroplastik, Peritonitis, Nachblutung aus der Pyloroplastik, Bauchdekkenruptur) in 14,4 %. Die Gesamtletalität betrug 4,6 %, die elektive 1,6 %. Ulcusrezidive traten nach 1/2–2 1/4 Jahre auf, die Rezidivrate lag bei 3,2 %, von denen ber die Hälfte relaparotomiert werden mußten. In 5,3 % war eine Relaparotomie wegen Peritonitis, gastrointestinale Blutung, Blutung aus der kleinen Kurvatur, Ileus und Carcinom notwendig. Die stimulierte Säuresekretion im Pentagastrin-Test wurde konstant über 2 Jahre und mehr um 60 % reduziert. Nach dem Visick-Schema hatten je nach Nachbeobachtungszeit von 1–3 Jahren 61–65 % der Patienten ein gutes und 16–22 % ein schlechtes Ergebnis.
    Notes: Summary The results of selective proximal vagotomy and pyloroplasty for duodenal and gastric ulcer in 464 patients over the last 5 years were evaluated in 438 cases. More than 75 % of the patients were observed for 2 years after the operation. More than 25 % were emergency cases, the incidence of intraoperative complications like splenic lesions or perforation of the esophagus was 3.2%. Postoperative complications like leakage of the pyloroplasty, peritonitis, hemorrhage from the pyloroplasty or disruption of the laparotomy closure occurred in 14,4 %. The overall mortality was 4.6 %, the elective mortality 1.6 %. Recurrent ulcers were seen after 1/2–2 1/4 years with an overall rate of 3.2 %. Over half of these cases required relaparotomy. In 5.3 % relaparotomy had to be done for peritonitis, GI-bleeding, bleeding from the lesser curvature of the stomach, ileus or carcinoma. The Pentagastrin stimulated gastric secretion remained constantly reduced for more then 2 years in over 60 %. Following the Visick-grading system the results were good in 61–65 % of the patients and bad in 16–22 % depending on the time of observation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01254855
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Syntheses of α-Aminophosphonic Acids, VI. Synthesis of Diastereomerically Pure 1-Aminocyclopropylphosphonic Acids (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 427-431 
    Details
    ISSN: 0170-2041
    Keywords: α-Aminophosphonic acids ; Cyclopropanation, diastereoselective ; Isocyanides ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The lithium or potassium derivative of diethyl isocyanomethylphosphonate (1) reacts with epoxides in the presence of boron trifluoride-diethyl ether to provide the diethyl 3-hydroxy-1-isocyanoalkylphosphonates rac-3. The corresponding mesylates rac-4 undergo a base-mediated cyclization to the diethyl 1-isocyanocyclopropylphosphonates rac-5. Acidic hydrolysis affords the diethyl 1-aminocyanocyclopropylphosphonates rac-6, which upon treatment with trimethylsilyl iodide yield the 1-aminocyclopropylphosphonic acids rac-7. A base-mediated cycloalkylation of 1 with dibromoalkanes 10 gives the diethyl 1-isocyanocycloalkylphosphonates 11, which are suitable precursors for the achiral 1-aminocycloalkylphosphonic acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199319930169
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    Paper (German National Licenses)
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  • 3
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    Integrating Lipschitzian dynamical systems using piecewise algorithmic differentiation (2017)
    Details
    Publication Date: 2023-03-31
    Description: In this article we analyse a generalized trapezoidal rule for initial value problems with piecewise smooth right-hand side F : IR^n -〉 IR^n based on a generalization of algorithmic differentiation. When applied to such a problem, the classical trapezoidal rule suffers from a loss of accuracy if the solution trajectory intersects a nondifferentiability of F. The advantage of the proposed generalized trapezoidal rule is threefold: Firstly, we can achieve a higher convergence order than with the classical method. Moreover, the method is energy preserving for piecewise linear Hamiltonian systems. Finally, in analogy to the classical case we derive a third-order interpolation polynomial for the numerical trajectory. In the smooth case, the generalized rule reduces to the classical one. Hence, it is a proper extension of the classical theory. An error estimator is given and numerical results are presented.
    Language: English
    Type: article , doc-type:article
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    OPUS
  • 4
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    Piecewise linear secant approximation via algorithmic piecewise differentiation (2017)
    Details
    Publication Date: 2023-03-31
    Description: It is shown how piecewise differentiable functions F : IR^n -〉 IR^m that are defined by evaluation programmes can be approximated locally by a piecewise linear model based on a pair of sample points \check x and \hat x. We show that the discrepancy between function and model at any point x is of the bilinear order O(||x - \check x||*||x - \hat x||). As an application of the piecewise linearization procedure we devise a generalized Newton's method based on successive piecewise linearization and prove for it sufficient conditions for convergence and convergence rates equalling those of semismooth Newton. We conclude with the derivation of formulas for the numerically stable implementation of the aforedeveloped piecewise linearization methods.
    Language: English
    Type: article , doc-type:article
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    OPUS
  • 5
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    An Open Newton Method for Piecewise Smooth Systems (2018)
    Details
    Publication Date: 2023-03-31
    Description: Recent research has shown that piecewise smooth (PS) functions can be approximated by piecewise linear functions with second order error in the distance to a given reference point. A semismooth Newton type algorithm based on successive application of these piecewise linearizations was subsequently developed for the solution of PS equation systems. For local bijectivity of the linearization at a root, a radius of quadratic convergence was explicitly calculated in terms of local Lipschitz constants of the underlying PS function. In the present work we relax the criterium of local bijectivity of the linearization to local openness. For this purpose a weak implicit function theorem is proved via local mapping degree theory. It is shown that there exist PS functions f:IR^2 --〉 IR^2 satisfying the weaker criterium where every neighborhood of the root of f contains a point x such that all elements of the Clarke Jacobian at x are singular. In such neighborhoods the steps of classical semismooth Newton are not defined, which establishes the new method as an independent algorithm. To further clarify the relation between a PS function and its piecewise linearization, several statements about structure correspondences between the two are proved. Moreover, the influence of the specific representation of the local piecewise linear models on the robustness of our method is studied. An example application from cardiovascular mathematics is given.
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
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    OPUS
  • 6
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    Computational aspects of the Generalized Trapezoidal Rule (2018)
    Details
    Publication Date: 2023-03-31
    Description: In this article we analyze a generalized trapezoidal rule for initial value problems with piecewise smooth right hand side F:IR^n -〉 IR^n. When applied to such a problem, the classical trapezoidal rule suffers from a loss of accuracy if the solution trajectory intersects a non-differentiability of F. In such a situation the investigated generalized trapezoidal rule achieves a higher convergence order than the classical method. While the asymptotic behavior of the generalized method was investigated in a previous work, in the present article we develop the algorithmic structure for efficient implementation strategies and estimate the actual computational cost of the latter. Moreover, energy preservation of the generalized trapezoidal rule is proved for Hamiltonian systems with piecewise linear right hand side.
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
    Library Location Call Number Volume/Issue/Year Availability
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    OPUS
  • 7
    facet.materialart.
    Unknown
    Integrating Lipschitzian Dynamical Systems using Piecewise Algorithmic Differentiation (2017)
    Details
    Publication Date: 2023-03-31
    Description: In this article we analyze a generalized trapezoidal rule for initial value problems with piecewise smooth right hand side \(F:R^n \to R^n\) based on a generalization of algorithmic differentiation. When applied to such a problem, the classical trapezoidal rule suffers from a loss of accuracy if the solution trajectory intersects a nondifferentiability of \(F\). The advantage of the proposed generalized trapezoidal rule is threefold: Firstly, we can achieve a higher convergence order than with the classical method. Moreover, the method is energy preserving for piecewise linear Hamiltonian systems. Finally, in analogy to the classical case we derive a third order interpolation polynomial for the numerical trajectory. In the smooth case the generalized rule reduces to the classical one. Hence, it is a proper extension of the classical theory. An error estimator is given and numerical results are presented.
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
    Library Location Call Number Volume/Issue/Year Availability
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    OPUS
  • 8
    facet.materialart.
    Unknown
    Piecewise linear secant approximation via Algorithmic Piecewise Differentiation (2016)
    Details
    Publication Date: 2023-03-31
    Description: It is shown how piecewise differentiable functions \(F: R^n → R^m\) that are defined by evaluation programs can be approximated locally by a piecewise linear model based on a pair of sample points x̌ and x̂. We show that the discrepancy between function and model at any point x is of the bilinear order O(||x − x̌|| ||x − x̂||). This is a little surprising since x ∈ R^n may vary over the whole Euclidean space, and we utilize only two function samples F̌ = F(x̌) and F̂ = F(x̂), as well as the intermediates computed during their evaluation. As an application of the piecewise linearization procedure we devise a generalized Newton’s method based on successive piecewise linearization and prove for it sufficient conditions for convergence and convergence rates equaling those of semismooth Newton. We conclude with the derivation of formulas for the numerically stable implementation of the aforedeveloped piecewise linearization methods.
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
    Library Location Call Number Volume/Issue/Year Availability
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    OPUS
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