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  • 2005-2009  (31)
  • 1985-1989
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  • 2009  (31)
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  • ddc:510  (31)
  • Electron Microscopy  (24)
  • 1
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    Barrier methods for a control problem from hyperthermia treatment planning (2009)
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    Publication Date: 2019-01-29
    Description: We consider an optimal control problem from hyperthermia treatment planning and its barrier regularization. We derive basic results, which lay the groundwork for the computation of optimal solutions via an interior point path-following method. Further, we report on a numerical implementation of such a method and its performance at an example problem.
    Keywords: ddc:510
    Language: English
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  • 2
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    Transparent boundary conditions for Maxwell's equations: Numerical concepts beyond the PML method (2009)
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    Publication Date: 2016-06-09
    Description: Optical technologies are ubiquitously used in hi-tech devices. As a common feature of such devices one finds structures with dimensions in the order of the wavelength of the used light. To design and produce such devices, the wave nature of light must be taken into account. Accordingly, robust simulation tools are required which are based on rigorously solving Maxwell's equations, the governing equations of light propagation within macroscopic media. This thesis contributes to the modeling and the numerical computation of light scattering problems: Light scattering problems are typically posed on the entire space. The Perfectly-Matched -Layer method (PML) is widely used to restrict the simulation problem onto a bounded computational domain. We propose an adaptive PML method which exhibits a good convergence even for critical problems where standard PML implementations fail. Besides the computation of the near field, that is the electromagnetic field within the computational domain, it is of major interest to evaluate the electromagnetic field in the exterior domain and to compute the far field. So far, this was numerically only possible for simple geometries such as homogeneous exterior domains or layered media. To deal with more complicated devices, for example with waveguide inhomogeneities, we develop an evaluation formula based on the PML solution which allows for an exterior domain field evaluation in a half space above the device. Finally, we generalize the PML method to problems with multiply structured exterior domains. The term “multiply structured exterior domain” is defined in this thesis and means that the exterior domain exhibits several half-infinite structures. Mathematically, this gives rise to various complications. For example, no analytical solutions to Maxwell's equations for standard light sources are available in the exterior domain, which are needed to describe the incoming field in a light scattering problem. To tackle this we propose a new light scattering problem formulation which fits well into the PML method framework and which may be regarded as an extension of classical contributions by Sommerfeld, Wiener and Hopf. An exterior domain evaluation formula for multiply structured exterior domains with an extended illumination is derived as well.
    Keywords: ddc:510
    Language: English
    Type: doctoralthesis , doc-type:doctoralThesis
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  • 3
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    The Coolest Path Problem (2009)
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    Publication Date: 2020-08-05
    Description: We introduce the coolest path problem, which is a mixture of two well-known problems from distinct mathematical fields. One of them is the shortest path problem from combinatorial optimization. The other is the heat conduction problem from the field of partial differential equations. Together, they make up a control problem, where some geometrical object traverses a digraph in an optimal way, with constraints on intermediate or the final state. We discuss some properties of the problem and present numerical solution techniques. We demonstrate that the problem can be formulated as a linear mixed-integer program. Numerical solutions can thus be achieved within one hour for instances with up to 70 nodes in the graph.
    Keywords: ddc:510
    Language: English
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  • 4
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    The MCF-Separator -- Detecting and Exploiting Multi-Commodity Flow Structures in MIPs (2009)
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    Publication Date: 2021-08-05
    Description: Given a general mixed integer program (MIP), we automatically detect block structures in the constraint matrix together with the coupling by capacity constraints arising from multi-commodity-flow formulations. We identify the underlying graph and generate cutting planes based on cuts in the detected network. Our implementation adds a separator to the branch-and-cut libraries of SCIP and CPLEX. We make use of the complemented mixed integer rounding framework (cMIR) but provide a special purpose aggregation heuristic that exploits the network structure. Our separation scheme speeds-up the computation for a large set of MIPs coming from network design problems by a factor of two on average.
    Keywords: ddc:510
    Language: English
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  • 5
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    Nonlinear pseudo-Boolean optimization: relaxation or propagation? (2009)
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    Publication Date: 2022-03-14
    Description: Pseudo-Boolean problems lie on the border between satisfiability problems, constraint programming, and integer programming. In particular, nonlinear constraints in pseudo-Boolean optimization can be handled by methods arising in these different fields: One can either linearize them and work on a linear programming relaxation or one can treat them directly by propagation. In this paper, we investigate the individual strengths of these approaches and compare their computational performance. Furthermore, we integrate these techniques into a branch-and-cut-and-propagate framework, resulting in an efficient nonlinear pseudo-Boolean solver.
    Keywords: ddc:510
    Language: English
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  • 6
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    Planning Problems in Public Transit (2009)
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    Publication Date: 2020-08-05
    Description: Every day, millions of people are transported by buses, trains, and airplanes in Germany. Public transit (PT) is of major importance for the quality of life of individuals as well as the productivity of entire regions. Quality and efficiency of PT systems depend on the political framework (state-run, market oriented) and the suitability of the infrastructure (railway tracks, airport locations), the existing level of service (timetable, flight schedule), the use of adequate technologies (information, control, and booking systems), and the best possible deployment of equipment and resources (energy, vehicles, crews). The decision, planning, and optimization problems arising in this context are often gigantic and “scream” for mathematical support because of their complexity. This article sketches the state and the relevance of mathematics in planning and operating public transit, describes today’s challenges, and suggests a number of innovative actions. The current contribution of mathematics to public transit is — depending on the transportation mode — of varying depth. Air traffic is already well supported by mathematics. Bus traffic made significant advances in recent years, while rail traffic still bears significant opportunities for improvements. In all areas of public transit, the existing potentials are far from being exhausted. For some PT problems, such as vehicle and crew scheduling in bus and air traffic, excellent mathematical tools are not only available, but used in many places. In other areas, such as rolling stock rostering in rail traffic, the performance of the existing mathematical algorithms is not yet sufficient. Some topics are essentially untouched from a mathematical point of view; e.g., there are (except for air traffic) no network design or fare planning models of practical relevance. PT infrastructure construction is essentially devoid of mathematics, even though enormous capital investments are made in this area. These problems lead to questions that can only be tackled by engineers, economists, politicians, and mathematicians in a joint effort. Among other things, the authors propose to investigate two specific topics, which can be addressed at short notice, are of fundamental importance not only for the area of traffic planning, should lead to a significant improvement in the collaboration of all involved parties, and, if successful, will be of real value for companies and customers: • discrete optimal control: real-time re-planning of traffic systems in case of disruptions, • model integration: service design in bus and rail traffic. Work on these topics in interdisciplinary research projects could be funded by the German ministry of research and education (BMBF), the German ministry of economics (BMWi), or the German science foundation (DFG).
    Keywords: ddc:510
    Language: English
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  • 7
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    Solving Steel Mill Slab Problems with Branch and Price (2009)
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    Publication Date: 2020-08-05
    Description: The steel mill slab design problem from the CSPLib is a binpacking problem that is motivated by an application of the steel industry and that has been widely studied in the constraint programming community. Recently, several people proposed new models and methods to solve this problem. A steel mill slab library was created which contains 380 instances. A closely related binpacking problem called multiple knapsack problem with color constraints, originated from the same industrial problem, were discussed in the integer programming community. In particular, a simple integer programming for this problem has been given by Forrest et al. [3]. The aim of this paper is to bring these different studies together. Moreover, we adopt the model of [3] for the steel mill slab problem. Using a state of the art integer program solver, this model is capable to solve all instances of the steel mill slab library, mostly in less than one second, to optimality. We improved, thereby, the solution value of 76 instances.
    Keywords: ddc:510
    Language: English
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  • 8
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    On the Hardness of Finding Small Shortest Path Routing Conflicts (2009)
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    Publication Date: 2020-08-05
    Description: Nowadays most data networks use shortest path protocols such as OSPF or IS-IS to route traffic. Given administrative routing lengths for the links of a network, all data packets are sent along shortest paths with respect to these lengths from their source to their destination. One of the most fundamental problems in planning shortest path networks is to decide whether a given set of routing paths forms a valid routing and, if this is not the case, to find a small subset of the given paths that cannot be shortest paths simultaneously for any routing lengths. In this paper we show that it is NP-hard to approximate the size of the smallest shortest path conflict by a factor less than 7/6.
    Keywords: ddc:510
    Language: English
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  • 9
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    A Binary Quadratic Programming Approach to the Vehicle Positioning Problem (2009)
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    Publication Date: 2020-08-05
    Description: The Vehicle Positioning Problem (VPP) consists of the assignment of vehicles (buses, trams or trains) of a public transport or railway company to parking positions in a depot and to timetabled trips. Such companies have many different types of vehicles, and each trip can be performed only by vehicles of some of these types. These assignments are non-trivial due to the topology of depots. The parking positions are organized in tracks, which work as one- or two-sided stacks or queues. If a required type of vehicle is not available in the front of any track, shunting movements must be performed in order to change vehicles' positions, which is undesirable and should be avoided. In this text we present integer linear and non-linear programming formulations for some versions of the problem and compare them from a theoretical and a computational point of view.
    Keywords: ddc:510
    Language: English
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  • 10
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    Statistical Error Estimation and Grid-free Hierarchical Refinement in Conformation Dynamics (2009)
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    Publication Date: 2020-03-11
    Description: The understanding of geometric structures and dynamical properties of molecular conformations gives insight into molecular long-term behavior. The identification of metastable conformations together with their life times and transition patterns is the intention of conformation dynamics. Conformation dynamics is a multi-scale approach that leads to a reduced description of the dynamical system in terms of a stochastic transition probability matrix. The present thesis deals with the error analysis of computed matrices and the resulting matrix functions. Since conformational membership vectors, as they are computed by the Robust Perron Cluster Analysis (PCCA+), form an invariant subspace of the transition matrix, subspace-based error estimators are of particular interest. The decomposition of the state space into basis functions and the approximation of integrals by Monte-Carlo quadrature give rise to row-wise correlated random matrices, for which stochastic norms are computed. Together with an appropriate statistical model for the distribution of matrix rows, this allows for the calculation of error bounds and error distributions of the invariant subspace and other variables of interest. Equilibration of errors among the basis functions can be achieved by enhanced sampling in regions where the trajectories are mixing slowly. Hierarchical refinement of such basis functions systematically improves the clustering into metastable conformations by reducing the error in the corresponding invariant subspace. These techniques allow for an evaluation of simulation results and pave the way for the analysis of larger molecules. Moreover, the extension of PCCA+ to non-reversible Markov chains, verified by the corresponding perturbation theory, and the modification of the objective function for the case of soft membership vectors represent a further generalization of the clustering method, thus continuing the development from PCCA over PCCA+ to PCCA++. The methods developed in this thesis are useful for but not limited to conformation dynamics. In fact, they are applicable to a broader class of problems which combine domain decomposition with Monte-Carlo quadrature. Possible application areas may include the chemical master equation or quantum dynamical systems.
    Description: Das Verständnis von geometrischen Strukturen und dynamischen Eigenschaften molekularer Konformationen ist essentiell für die Vorhersage des Langzeitverhaltens von Molekülen. Die Identifikation metastabiler Konformationen sowie die Bestimmung von Übergangswahrscheinlichkeiten und Haltezeiten sind Bestandteil der Konformationdynamik. Dabei handelt es sich um eine Mehrskalenmethode, die auf eine reduzierte Beschreibung des Systems mittels einer stochastischen Übergangsmatrix führt. In der vorliegenden Dissertation wurde untersucht, wie man die Genauigkeit der Matrizen sowie der daraus berechneten Größen quantifizieren kann. Im Mittelpunkt stehen dabei Fehlerschätzer für den invarianten Unterraum, da die rechten Eigenvektoren als Grundlage der Robusten Perron Cluster Analyse (PCCA+) zur Identifizierung der metastabilen Konformationen dienen. Die Zerlegung des Zustandsraumes in Basisfunktionen sowie die Approximation der Matrixeinträge mittels Monte-Carlo-Quadratur führen zu zeilenweise korrelierten Zufallsmatrizen. Mit Hilfe einer stochastischen Norm sowie einem geeigneten statistischen Modell für die Verteilung der Matrixzeilen können u.a. Fehlerschranken und -verteilungen für den invarianten Unterraum brechnet werden. Eine Equilibrierung des Fehlers zwischen den Basisfunktionen kann durch erweitertes Sampling in solchen Regionen erreicht werden, in denen die Trajektorien nur langsam mischen.Eine hierarchische Zerlegung dieser Basisfunktionen verbessert systematisch die Zerlegung in metastabile Konformationen, indem sie den Fehler im invarianten Unterraum reduziert. Diese Techniken gestatten eine Evaluierung der Simulationsergebnisse und ebnen den Weg zur Behandlung komplexerer Moleküle. Desweiteren wurden Verallgemeinerungen der PCCA+ untersucht. Die Erweiterung der PCCA+ auf nicht-reversible Markov-Ketten sowie die Modifizierung der Zielfunktion für den Fall der weichen Clusterung setzen die Entwicklung von der PCCA über PCCA+ zu PCCA++ fort. Somit können neue Anwendungsfelder für dieses Cluster-Verfahren erschlossen werden. Die Methoden wurden zwar in Rahmen der Konformationsdynamik entwickelt, jedoch lassen sie sich auf eine weite Problemklasse anwenden, in der Gebietszerlegungsverfahren mit Monte-Carlo-Quadratur kombiniert werden. Mögliche Anwendungsgebiete umfassen die chemische Master-Gleichung oder quantenchemische Systeme.
    Keywords: ddc:510
    Language: English
    Type: doctoralthesis , doc-type:doctoralThesis
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  • 11
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    A Set Partitioning Approach to Shunting (2009)
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    Publication Date: 2020-08-05
    Description: The Vehicle Positioning Problem (VPP) is a classical combinatorial optimization problem in public transport planning. A number of models and approaches have been suggested in the literature, which work for small problems, but not for large ones. We propose in this article a novel set partitioning model and an associated column generation solution approach for the VPP. The model provides a tight linear description of the problem. The pricing problem, and hence the LP relaxation itself, can be solved in polynomial resp. pseudo-polynomial time for some versions of the problems.
    Keywords: ddc:510
    Language: English
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  • 12
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    Solving Large-scale Open Pit Mining Production Scheduling Problems by Integer Programming (2009)
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    Publication Date: 2020-08-05
    Description: Since the initial application of mathematical optimisation methods to mine planning in 1965, the Lerchs-Grossmann algorithm for computing the ultimate pit limit, operations researchers have worked on a variety of challenging problems in the area of open pit mining. This thesis focuses on the open pit mining production scheduling problem: Given the discretisation of an orebody as a block model, determine the sequence in which the blocks should be removed from the pit, over the lifespan of the mine, such that the net present value of the mining operation is maximised. In practise, when some material has been removed from the pit, it must be processed further in order to extract the valuable elements contained therein. If the concentration of valuable elements is not sufficiently high, the material is discarded as waste or stockpiled. Realistically-sized block models can contain hundreds of thousands of blocks. A common approach to render these problem instances computationally tractable is the aggregation of blocks to larger scheduling units. The thrust of this thesis is the investigation of a new mixed-integer programming formulation for the open pit mining production scheduling problem, which allows for processing decisions to be made at block level, while the actual mining schedule is still computed at aggregate level. A drawback of this model in its full form is the large number of additional variables needed to model the processing decisions. One main result of this thesis shows how these processing variables can be aggregated efficiently to reduce the problem size significantly, while practically incurring no loss in net present value. The second focus is on the application of lagrangean relaxation to the resource constraints. Using a result of Möhring et al. (2003) for project scheduling, the lagrangean relaxation can be solved efficiently via minimum cut computations in a weighted digraph. Experiments with a bundle algorithm implementation by Helmberg showed how the lagrangean dual can be solved within a small fraction of the time required by standard linear programming algorithms, while yielding practically the same dual bound. Finally, several problem-specific heuristics are presented together with computational results: two greedy sub-MIP start heuristics and a large neighbourhood search heuristic. A combination of a lagrangean-based start heuristic followed by a large neighbourhood search proved to be effective in generating solutions with objective values within a 0.05% gap of the optimum.
    Keywords: ddc:510
    Language: English
    Type: masterthesis , doc-type:masterThesis
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  • 13
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    1D-Reduktion thermal signifikanter Aderstränge in der Hyperthermie-Modellierung (2009)
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    Publication Date: 2019-01-29
    Description: In dieser Arbeit wird ein neuer Ansatz zur Modellierung von thermal signifikanten Gefäßsträngen im Hyperthermie-Kontext betrachtet. Ausgehend von einer Konvektions-Diffusions-Gleichung wird durch Reskalierung des Massenflussterms eine Reduktion des Adergebietes auf eine 1D-Struktur erreicht. Nach numerischen Vorbetrachtungen wird die Grenzgleichung innerhalb einer verallgemeinerten Sobolev-Algebra formuliert. Die Untersuchung der Lösungsfamilie in klassischen Funktionenräumen zeigt, dass deren schwacher Grenzwert die Lösung der korrespondierenden Diffusions-Gleichung ist. Die Diskretisierung einer formalen Grenzgleichung mit Linienstromanteil stellt jedoch eine gute Approximation an die Diskretisierung des ursprünglichen Problems dar, wenn man die lokale Maschenweite an die Gefäßradien koppelt und bei erhöhtem Genauigkeitsbedarf auf ein vollständiges 3D-Modell umschaltet.
    Keywords: ddc:510
    Language: German
    Type: masterthesis , doc-type:masterThesis
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  • 14
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    Undercover – a primal heuristic for MINLP based on sub-MIPs generated by set covering (2009)
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    Publication Date: 2022-03-14
    Description: We present Undercover, a primal heuristic for mixed-integer nonlinear programming (MINLP). The heuristic constructs a mixed-integer linear subproblem (sub-MIP) of a given MINLP by fixing a subset of the variables. We solve a set covering problem to identify a minimal set of variables which need to be fixed in order to linearise each constraint. Subsequently, these variables are fixed to approximate values, e.g. obtained from a linear outer approximation. The resulting sub-MIP is solved by a mixed-integer linear programming solver. Each feasible solution of the sub-MIP corresponds to a feasible solution of the original problem. Although general in nature, the heuristic seems most promising for mixed-integer quadratically constrained programmes (MIQCPs). We present computational results on a general test set of MIQCPs selected from the MINLPLib.
    Keywords: ddc:510
    Language: English
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  • 15
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    On sojourn times in M/GI systems under state-dependent processor sharing (2009)
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    Publication Date: 2020-08-05
    Description: We consider a system with Poisson arrivals and i.i.d. service times. The requests are served according to the state-dependent processor sharing discipline, where each request receives a service capacity which depends on the actual number of requests in the system. The linear systems of PDEs describing the residual and attained sojourn times coincide for this system, which provides time reversibility including sojourn times for this system, and their minimal non negative solution gives the LST of the sojourn time $V(\tau)$ of a request with required service time $\tau$. For the case that the service time distribution is exponential in a neighborhood of zero, we derive a linear system of ODEs, whose minimal non negative solution gives the LST of $V(\tau)$, and which yields linear systems of ODEs for the moments of $V(\tau)$ in the considered neighborhood of zero. Numerical results are presented for the variance of $V(\tau)$. In case of an M/GI/2-PS system, the LST of $V(\tau)$ is given in terms of the solution of a convolution equation in the considered neighborhood of zero. For bounded from below service times, surprisingly simple expressions for the LST and variance of $V(\tau)$ in this neighborhood of zero are derived, which yield in particular the LST and variance of $V(\tau)$ in M/D/2-PS.
    Keywords: ddc:510
    Language: English
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  • 16
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    E-Learning and the Working Mathematician (2009)
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    Publication Date: 2020-12-11
    Description: Eigentlich war der erste Autor nur zu einem Grußwort zur Tagung „GML² 2009 - Grundfragen Multi¬medialen Lehrens und Lernens“ eingeladen. Daraus wurde ein E-Learning-bezogener Vortrag, der – basierend auf Erfahrungen im Fach Mathematik – einen kritischen Blick auf die E-Learning-Szene in Deutschland wirft und diese mit entsprechenden Aktivitäten weltweit vergleicht. Dies ist die in seinen mathematischen Teilen gekürzte, in den E-Learning-Anteilen ein wenig erweiterte schriftliche Fassung des Vortrags. Der Artikel stammt nicht von E-Learning-Spezialisten sondern von Personen, die sich seit fast zwanzig Jahren mit elektronischer Information und Kommunikation (kurz: IuK) – insbesondere in der Mathematik – beschäftigen. Nach einer Definition von Michael Kerres kennzeichnet der Begriff E-Learning (electronic learning – elektronisch unterstütztes Lernen) alle Formen von Lernen, bei denen digitale Medien für die Präsentation und Distribution von Lernmaterialien und/oder zur Unterstützung zwischenmenschlicher Kommunikation zum Einsatz kommen, siehe z.B. http://de.wikipedia.org/wiki/E-Learning. IuK und E-Learning haben nach dieser Begriffsbildung viele Berührungspunkte. Deswegen wagen wir es, unsere positiven und negativen Erfahrungen im Bereich IuK in diesem Eröffnungsvortrag zu berichten, einige Entwicklungslinien zu vergleichen und eine eigene Kurzversion der Definition von E-Learning (besser E-Teaching and -Learning) voranzustellen: „Lehren und Lernen mit Unterstützung elektronischer Hilfsmittel“.
    Keywords: ddc:510
    Language: German
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  • 17
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    Optimal Design of Survivable Multi-layer Telecommunication Networks (2009)
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    Publication Date: 2020-08-05
    Description: Telecommunication transport networks consist of a stack of technologically different subnetworks, so-called layers, which are strongly interdependent. For example, one layer may correspond to an Internet (IP) backbone network whose links are realized by lightpath connections in an underlying optical fiber layer. To ensure that the network can fulfill its task of routing all communication requests, the inter-layer dependencies have to be taken into account already in the planning phase of the network. This is particularly important with survivability constraints, where connections in one layer have to be protected against cable cuts or equipment failures in another layer. The traditional sequential planning approach where one layer is optimized after the other cannot properly take care of the inter-layer dependencies; this can only be achieved with an integrated planning of several network layers at the same time. This thesis provides mathematical models and algorithmic techniques for the integrated optimization of two network layers with survivability constraints. We describe a multi-layer network design problem which occurs in various technologies, and model it mathematically using mixed-integer programming (MIP) formulations. The presented models cover many important practical side constraints from different technological contexts. In contrast to previous models from the literature, they can be used to design large two-layer networks with survivability requirements. We discuss modeling alternatives for various aspects of a multi-layer network and compare different routing formulations under multi-layer survivability constraints. We solve our models using a branch-and-cut-and-price approach with various problemspecific enhancements. This includes a presolving technique based on linear programming to reduce the problem size, combinatorial and sub-MIP-based primal heuristics to compute feasible network configurations, cutting planes which take the multi-layer survivability constraints into account to improve the lower bound on the optimal network cost, and column generation to generate flow variables dynamically during the algorithm. We develop techniques to speed up computations in a Benders decomposition approach and compare this approach to the standard formulation with a single MIP. We use the developed techniques to design large survivable two-layer networks by means of linear and integer programming methods. On realistic test instances with up to 67 network nodes and survivability constraints, we investigate the algorithmic impact of our techniques and show how to use them to compute good network configurations with quality guarantees. Most of the smaller test instances with up to 17 nodes can be solved to near-optimality. Moreover, we can compute feasible solutions and dual bounds even for large networks with survivability constraints, which has not been possible before.
    Keywords: ddc:510
    Language: English
    Type: doctoralthesis , doc-type:doctoralThesis
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  • 18
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    On the Factorization of Simplex Basis Matrices (2009)
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    Publication Date: 2020-08-05
    Description: In the simplex algorithm, solving linear systems with the basis matrix and its transpose accounts for a large part of the total computation time. We investigate various methods from modern numerical linear algebra to improve the computation speed of the basis updates arising in LPs. The experiments are executed on a large real-world test set. The most widely used solution technique is sparse LU factorization, paired with an updating scheme that allows to use the factors over several iterations. Clearly, small number of fill-in elements in the LU factors is critical for the overall performance. Using a wide range of LPs we show numerically that after a simple permutation the non-triangular part of the basis matrix is so small, that the whole matrix can be factorized with (relative) fill-in close to the optimum. This permutation has been exploited by simplex practitioners for many years. But to our knowledge no systematic numerical study has been published that demonstrates the effective reduction to a surprisingly small non-triangular problem, even for large scale LPs. For the factorization of the non-triangular part most existing simplex codes use some variant of dynamic Markowitz pivoting, which originated in the late 1950s. We also show numerically that, in terms of fill-in and in the simplex context, dynamic Markowitz is quite consistently superior to other, more recently developed techniques.
    Keywords: ddc:510
    Language: English
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  • 19
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    Computing expectation values for molecular quantum dynamics (2009)
    Details
    Publication Date: 2020-03-11
    Description: We compute expectation values for the solution of the nuclear Schrödinger equation. The proposed particle method consists of three steps: sampling of the initial Wigner function, classical transport of the sampling points, weighted phase space summation for the final computation of the expectation values. The Egorov theorem guarantees that the algorithm is second order accurate with respect to the semiclassical parameter. We present numerical experiments for a two-dimensional torsional potential with three different sets of initial data and for a six-dimensional Henon-Heiles potential. By construction, the computing times scale linearly with the number of initial sampling points and range between three seconds and one hour.
    Keywords: ddc:510
    Language: English
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    Extending a CIP framework to solve MIQCPs (2009)
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    Publication Date: 2022-03-14
    Description: This paper discusses how to build a solver for mixed integer quadratically constrained programs (MIQCPs) by extending a framework for constraint integer programming (CIP). The advantage of this approach is that we can utilize the full power of advanced MIP and CP technologies. In particular, this addresses the linear relaxation and the discrete components of the problem. For relaxation, we use an outer approximation generated by linearization of convex constraints and linear underestimation of nonconvex constraints. Further, we give an overview of the reformulation, separation, and propagation techniques that are used to handle the quadratic constraints efficiently. We implemented these methods in the branch-cut-and-price framework SCIP. Computational experiments indicates the potential of the approach.
    Keywords: ddc:510
    Language: English
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  • 21
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    A Subspace Approach to Molecular Markov State Models via an Infinitesimal Generator (2009)
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    Publication Date: 2016-06-09
    Description: Supercomputers can simulate complex molecular systems. However, there is a very large gap between the fastest oscillations of covalent bonds of a molecule and the time-scale of the dominant processes. In order to extract the dominant time-scales and to identify the dominant processes, a clustering of information is needed. This thesis shows that only the subspace-based Robust Perron Cluster Analysis (PCCA+) can solve this problem correctly by the construction of a Markov State Model. PCCA+ allows for time-extrapolation in molecular kinetics. This thesis shows the difference between molecular dynamics and molecular kinetics. Only in the molecular kinetics framework a definition of transition rates is possible. In this context, the existence of an infinitesimal generator of the dynamical processes is discussed. If the existence is assumed, the Theorem of Gauß can be applied in order to compute transition rates efficiently. Molecular dynamics, however, is not able to provide a suitable statistical basis for the determination of the transition pattern.
    Keywords: ddc:510
    Language: English
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  • 22
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    Approximations for the second moments of sojourn times in M/GI systems under state-dependent processor sharing (2009)
    Details
    Publication Date: 2020-08-05
    Description: We consider a system with Poisson arrivals and general service times, where the requests are served according to the State-Dependent Processor Sharing (SDPS) discipline (Cohen's generalized processor sharing discipline), where each request receives a service capacity which depends on the actual number of requests in the system. For this system, denoted by $M/GI/SDPS$, we derive approximations for the squared coefficients of variation of the conditional sojourn time of a request given its service time and of the unconditional sojourn time by means of two-moment fittings of the service times. The approximations are given in terms of the squared coefficients of variation of the conditional and unconditional sojourn time in related $M/D/SDPS$ and $M/M/SDPS$ systems, respectively. The numerical results presented for $M/GI/m-PS$ systems illustrate that the proposed approximations work well.
    Keywords: ddc:510
    Language: English
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  • 23
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    Insensitivity bounds for the moments of the sojourn times in M/GI systems under state-dependent processor sharing (2009)
    Details
    Publication Date: 2020-08-05
    Description: We consider a system with Poisson arrivals and i.i.d. service times and where the requests are served according to the state-dependent (Cohen's generalized) processor sharing discipline, where each request in the system receives a service capacity which depends on the actual number of requests in the system. For this system we derive asymptotically tight upper bounds for the moments of the conditional sojourn time of a request with given required service time. The bounds generalize corresponding results, recently given for the single-server processor sharing system by Cheung et al. and for the state-dependent processor sharing system with exponential service times by the authors. Analogous results hold for the waiting times.
    Keywords: ddc:510
    Language: English
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  • 24
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    Randomized Online Algorithms for Dynamic Multi-Period Routing Problems (2009)
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    Publication Date: 2020-11-13
    Description: The Dynamic Multi-Period Routing Problem DMPRP introduced by Angelelli et al. gives a model for a two-stage online-offline routing problem. At the beginning of each time period a set of customers becomes known. The customers need to be served either in the current time period or in the following. Postponed customers have to be served in the next time period. The decision whether to postpone a customer has to be done online. At the end of each time period, an optimal tour for the customers assigned to this period has to be computed and this computation can be done offline. The objective of the problem is to minimize the distance traveled over all planning periods assuming optimal routes for the customers selected in each period. We provide the first randomized online algorithms for the DMPRP which beat the known lower bounds for deterministic algorithms. For the special case of two planning periods we provide lower bounds on the competitive ratio of any randomized online algorithm against the oblivious adversary. We identify a randomized algorithm that achieves the optimal competitive ratio of $\frac{1+\sqrt{2}}{2}$ for two time periods on the real line. For three time periods, we give a randomized algorithm that is strictly better than any deterministic algorithm.
    Keywords: ddc:510
    Language: English
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  • 25
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    Constraint Integer Programming (2009)
    Details
    Publication Date: 2021-08-05
    Description: This thesis introduces the novel paradigm of "constraint integer programming" (CIP), which integrates constraint programming (CP) and mixed integer programming (MIP) modeling and solving techniques. It is supplemented by the software SCIP, which is a solver and framework for constraint integer programming that also features SAT solving techniques. SCIP is freely available in source code for academic and non-commercial purposes. Our constraint integer programming approach is a generalization of MIP that allows for the inclusion of arbitrary constraints, as long as they turn into linear constraints on the continuous variables after all integer variables have been fixed. The constraints, may they be linear or more complex, are treated by any combination of CP and MIP techniques: the propagation of the domains by constraint specific algorithms, the generation of a linear relaxation and its solving by LP methods, and the strengthening of the LP by cutting plane separation. The current version of SCIP comes with all of the necessary components to solve mixed integer programs. In the thesis, we cover most of these ingredients and present extensive computational results to compare different variants for the individual building blocks of a MIP solver. We focus on the algorithms and their impact on the overall performance of the solver. In addition to mixed integer programming, the thesis deals with chip design verification, which is an important topic of electronic design automation. Chip manufacturers have to make sure that the logic design of a circuit conforms to the specification of the chip. Otherwise, the chip would show an erroneous behavior that may cause failures in the device where it is employed. An important subproblem of chip design verification is the property checking problem, which is to verify whether a circuit satisfies a specified property. We show how this problem can be modeled as constraint integer program and provide a number of problem-specific algorithms that exploit the structure of the individual constraints and the circuit as a whole. Another set of extensive computational benchmarks compares our CIP approach to the current state-of-the-art SAT methodology and documents the success of our method.
    Description: Diese Arbeit stellt einen integrierten Ansatz aus "Constraint Programming" (CP) und Gemischt-Ganzzahliger Programmierung ("Mixed Integer Programming", MIP) vor, den wir "Constraint Integer Programming" (CIP) nennen. Sowohl Modellierungs- als auch Lösungstechniken beider Felder fließen in den neuen integrierten Ansatz ein, um die unterschiedlichen Stärken der beiden Gebiete zu kombinieren. Als weiteren Beitrag stellen wir der wissenschaftlichen Gemeinschaft die Software SCIP zur Verfügung, die ein Framework für Constraint Integer Programming darstellt und zusätzlich Techniken des SAT-Lösens beinhaltet. SCIP ist im Source Code für akademische und nicht-kommerzielle Zwecke frei erhältlich. Unser Ansatz des Constraint Integer Programming ist eine Verallgemeinerung von MIP, die zusätzlich die Verwendung beliebiger Constraints erlaubt, solange sich diese durch lineare Bedingungen ausdrücken lassen falls alle ganzzahligen Variablen auf feste Werte eingestellt sind. Die Constraints werden von einer beliebigen Kombination aus CP- und MIP-Techniken behandelt. Dies beinhaltet insbesondere die "Domain Propagation", die Relaxierung der Constraints durch lineare Ungleichungen, sowie die Verstärkung der Relaxierung durch dynamisch generierte Schnittebenen. Die derzeitige Version von SCIP enthält alle Komponenten, die für das effiziente Lösen von Gemischt-Ganzzahligen Programmen benötigt werden. Die vorliegende Arbeit liefert eine ausführliche Beschreibung dieser Komponenten und bewertet verschiedene Varianten in Hinblick auf ihren Einfluß auf das Gesamt-Lösungsverhalten anhand von aufwendigen praktischen Experimenten. Dabei wird besonders auf die algorithmischen Aspekte eingegangen. Ein weiterer Hauptteil der Arbeit befasst sich mit der Chip-Design-Verifikation, die ein wichtiges Thema innerhalb des Fachgebiets der "Electronic Design Automation" darstellt. Chip-Hersteller müssen sicherstellen, dass der logische Entwurf einer Schaltung der gegebenen Spezifikation entspricht. Andernfalls würde der Chip fehlerhaftes Verhalten aufweisen, dass zu Fehlfunktionen innerhalb des Gerätes führen kann, in dem der Chip verwendet wird. Ein wichtiges Teilproblem in diesem Feld ist das Eigenschafts-Verifikations-Problem, bei dem geprüft wird, ob der gegebene Schaltkreisentwurf eine gewünschte Eigenschaft aufweist. Wir zeigen, wie dieses Problem als Constraint Integer Program modelliert werden kann und geben eine Reihe von problemspezifischen Algorithmen an, die die Struktur der einzelnen Constraints und der Gesamtschaltung ausnutzen. Testrechnungen auf Industrie-Beispielen vergleichen unseren Ansatz mit den bisher verwendeten SAT-Techniken und belegen den Erfolg unserer Methode.
    Keywords: ddc:510
    Language: English
    Type: doctoralthesis , doc-type:doctoralThesis
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    Fare Planning for Public Transport (2009)
    Details
    Publication Date: 2020-08-05
    Description: In this paper we investigate the fare planning model for public transport, which consists in designing a system of fares maximizing the revenue. We discuss a discrete choice model in which passengers choose between different travel alternatives to express the demand as a function of fares. Furthermore, we give a computational example for the city of Potsdam and discuss some theoretical aspects.
    Keywords: ddc:510
    Language: English
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  • 27
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    Improving the performance of elevator systems using exact reoptimization algorithms (2009)
    Details
    Publication Date: 2020-08-05
    Description: This extended abstract is about algorithms for controlling elevator systems employing destination hall calls, i.e. the passenger provides his destination floor when calling an elevator. We present the first exact algorithm for controlling a group of elevators and report on simulation results indicating that destination hall call systems outperform conventional systems.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 28
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    On goal-oriented adaptivity for elliptic optimal control problems (2009)
    Details
    Publication Date: 2019-01-29
    Description: The paper proposes goal-oriented error estimation and mesh refinement for optimal control problems with elliptic PDE constraints using the value of the reduced cost functional as quantity of interest. Error representation, hierarchical error estimators, and greedy-style error indicators are derived and compared to their counterparts when using the all-at-once cost functional as quantity of interest. Finally, the efficiency of the error estimator and generated meshes are demonstrated on numerical examples.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 29
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    Consistency Results for the Contact-Stabilized Newmark Method (2009)
    Details
    Publication Date: 2016-06-09
    Description: The paper considers the time integration of frictionless dynamical contact problems between viscoelastic bodies in the frame of the Signorini condition. Among the numerical integrators, interest focuses on the contact-stabilized Newmark method recently suggested by Deuflhard et al., which is compared to the classical Newmark method and an improved energy dissipative version due to Kane et al. In the absence of contact, any such variant is equivalent to the Störmer-Verlet scheme, which is well-known to have consistency order 2. In the presence of contact, however, the classical approach to discretization errors would not show consistency at all because of the discontinuity at the contact. Surprisingly, the question of consistency in the constrained situation has not been solved yet. The present paper fills this gap by means of a novel proof technique using specific norms based on earlier perturbation results due to the authors. The corresponding estimation of the local discretization error requires the bounded total variation of the solution. The results have consequences for the construction of an adaptive timestep control, which will be worked out subsequently in a forthcoming paper.
    Keywords: ddc:510
    Language: English
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  • 30
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    Discrete Optimization in Public Transportation (2009)
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    Publication Date: 2020-08-05
    Description: The mathematical treatment of planning problems in public transit has made significant advances in the last decade. Among others, the classical problems of vehicle and crew scheduling can nowadays be solved on a routine basis using combinatorial optimization methods. This is not yet the case for problems that pertain to the design of public transit networks, and for the problems of operations control that address the implementation of a schedule in the presence of disturbances. The article gives a sketch of the state and important developments in these areas, and it addresses important challenges. The vision is that mathematical tools of computer aided scheduling (CAS) will soon play a similar role in the design and operation of public transport systems as CAD systems in manufacturing.
    Description: Die mathematische Behandlung von Planungsproblemen im öffentlichen Verkehr hat im letzten Jahrzehnt große Fortschritte gemacht. Klassische Probleme wie die Umlauf- und die Dienstplanung können heutzutage routinemäßig mit kombinatorischen Optimierungsmethoden gelöst werden. Die Behandlung von Problemen der Angebotsplanung und der Betriebssteuerung sind dagegen noch nicht ganz auf diesem Stand. Dieser Artikel gibt einen Überblick über den Stand der Forschung, über wichtige Entwicklungen und einige Herausforderungen in diesem Gebiet. Die Vision ist, dass mathematische Planungswerkzeuge im öffentlichen Verkehr (Computer Aided Scheduling, CAS) in Zukunft eine ähnliche Rolle spielen werden wie CAD-Systeme in der industriellen Fertigung.
    Keywords: ddc:510
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  • 31
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    Variational and statistical shape modeling for 3D geometry reconstruction (2009)
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    Publication Date: 2022-07-19
    Description: The reconstruction of geometric shapes plays an important role in many biomedical applications. One example is the patient-specific, computer-aided planning of complex interventions, which requires the generation of explicitly represented geometric models of anatomical structures from medical image data. Only solutions that require minimal interaction by medical personnel are likely to enter clinical routine. Another example is the planning of surgical corrections of deformities where the target shape is unknown. Surgeons are often forced to resort to subjective criteria. These applications still pose highly challenging reconstruction problems, which are addressed in this thesis. The fundamental hypothesis, pursued in this thesis, is that the problems can be solved by incorporating a-priori knowledge about shape and other application-specific characteristics. Here, we focus mainly on the aspect of geometric shape analysis. The basic idea is to capture the most essential variations of a certain class of geometric objects via statistical shape models, which model typical features contained in a given population, and restrict the outcome of a reconstruction algorithm (more or less) to the space spanned by such models. A fundamental prerequisite for performing statistical shape analysis on a set of different objects is the identification of corresponding points on their associated surfaces. This problem is particularly difficult to solve if the shapes stem from different individuals. The reason lies in the basic difficulty of defining suitable measures of similarity. In this thesis, we divide the correspondence problem into feature and non-feature matching. The feature part depends on the application, while the non-feature part can be characterized by a purely geometric description. We propose two different approaches. The first approach has proved useful in many applications. Yet, it suffers from some practical limitations and does not yield a measure of similarity. Our second, variational, approach is designed to overcome these limitations. In it, we propose to minimize an invariant stretching measure, constrained by previously computed features. An important property, which sets our method apart from previous work, is that it does not require the computation of a global surface parameterization.
    Keywords: ddc:510
    Language: English
    Type: doctoralthesis , doc-type:doctoralThesis
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  • 32
    Electronic Resource
    Electronic Resource
    Electron microscopic observations in mice infected with Japanese encephalitis (1969)
    Springer
    Acta neuropathologica 13 (1969), S. 169-181 
    Details
    ISSN: 1432-0533
    Keywords: Japanese Encephalitis ; Experimental ; Electron Microscopy ; Virus Particles in Neurons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Groß- und Kleinhirnrinde, Plexus chorioideus und Rückenmark von Mäusen wurden nach intracerebraler Inoculation einer Hirnemulsion mit Virus der Encephalitis japonica (JEV) elektronenoptisch untersucht, um den Ort der JEV-Replikation zu bostimmen. 72 Std nach der Inoculation bei Beginn der encephalitischen Symptome enthielten 70 bis 80% aller Rindenneurone und Vorderhornzellen viele sphärische Partikel, die meist im zarten endoplasmatischen Reticulum (EPR) und vereinzelt im granulären EPR lokalisiert waren. Die Einzelpartikel zeigten eine gleichförmige Substruktur aus einem elektronendichten zentralen Hof von 25–30 mμ Durchmesser, einer äußeren, weniger elektronendichten Zone und einer äußersten Grenzmembran von 40 mμ Durchmesser. 96 Std nach der Inoculation zeigte das Cytoplasma der Rinden- und Vorderhornneurone sehr viele Vacuolen und Vesiceln. Partikel wurden weit verstreut in den Vacuolen und Vesiceln sowie erstmals im ERP der Sternzellen und Purkinjezellen angetroffen, allerdings in geringerer Zahl. Keine derartigen Partikel wurden in Kontrolltieren und normalen Mäusegruppen angetroffen. Sogenannte eosinophile intranucleäre Einschlüsse in Epithelzellen des Plexus chorioideus zeigten keine derartigen Partikel im Kern oder in den cytoplasmatischen Bläschen. Nachdem keine als JEV identifizierbaren Partikel in Glia- und Endothelzellen nachzuweisen waren, wird angenommen, daß das JEV echt neurotrop ist und sich im EPR der Nervenzellen repliziert.
    Notes: Summary Cerebral and cerebellar cortices, choroid plexus and spinal cord of mice, inoculated intracerebrally with a brain emulsion containing Japanese encephalitis virus (JEV), were studied electronmicroscopically to determine the cell type and the site of JEV replication. 72 hours after inoculation, when the mice began to show encephalitic symptoms, 70 to 80% of all cortical neurons and anterior horn cells contained many spherical particles mostly located in the smooth endoplasmic reticulum and a few in the granular endoplasmic reticulum. The individual particles demonstrated an uniform substructure consisting of an electron dense central core of 25–30 mμ diameter, an outer less electron dense zone and an outermost limiting membrane of 40 mμ diameter. 96 hours after inoculation, the cytoplasm of cortical neurons and anterior horn cells was observed to contain very many vacuoles and vesicles. Particles were found widely scattered throughout the vacuoles and vesicles, and were observed for the first time in the endoplasmic reticulum of the stellate neurons and in Purkinje cells, though fewer. No such particles were observed in control and normal mouse groups. So-called eosinophic intranuclear inclusions of epithelial cells of choroid plexus failed to show any particles in their nuclei or cytoplasmic vesicles. Considering that no particulate matter, identifiable as JEV, was identified within any of the glial cells or endothelium in this examination, it was concluded that JEV was really neurotropic and replicates in the endoplasmic reticulum of the neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00687029
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  • 33
    Electronic Resource
    Electronic Resource
    Granulomatous encephalitis in Whipple's disease (1969)
    Springer
    Acta neuropathologica 13 (1969), S. 1-11 
    Details
    ISSN: 1432-0533
    Keywords: Whipple's Disease ; Granulomatous Encephalitis ; Electron Microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Von 21 Fällen von Whipplescher Krankheit in der Sammlung des Armed Forces Institute of Pathology zeigten 4 Fälle neurologische Symptome mit besonders ausgeprägten Hirnläsionen. Lichtmikroskopisch bestanden die Herde aus knötchenförmigen Anhäufungen von Makrophagen, deren Cytoplasma mit Hämatoxylin-Eosin eine charakteristische schwachblaue und nach Durchführung der Perjodsäure-Schiff-Reaktion eine stark rote Färbung zeigte. Elektronenmikroskopisch fanden sich in den Hirnläsionen Bacillen, die morphologisch den im Darm beschriebenen glichen und die auch dieselben Degenerationserscheinungen aufwiesen. Die Perjodsäure-Schiff-Reaktion färbt Kapselmaterial und Zellwände,die auch nach Untergang der Bacillen noch nachweisbar sind. Diese Beobachtungen werden als weiterer Beweis für die infektiöse Ätiologie der Whippleschen Krankheit angeführt.
    Notes: Summary Among the 21 autopsied cases of Whipple's disease on file at the Armed Forces Institute of Pathology, 4 had neurological symptoms and prominent involvement of the central nervous system, By light microscopy the lesions were composed of nodular aggregates of macrophages having cytoplasm that stained a distinctive pale blue with hematoxylin-eosin and bright red with the periodic acid-Schiff technique. By electron microscopy the cerebral lesions revealed bacilli morphologically identical to and undergoing the same sequence of degenerative changes as those observed in the intestine. The periodic acid-Schiff reaction stains the walls and the capsular material that persists even after intact organisms disappear. These observations further support the infectious nature of Whipple's disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00686137
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    Electronic Resource
    Electronic Resource
    Ultrastructural and histochemical studies of cortical biopsies in subacute dementia (1969)
    Springer
    Acta neuropathologica 13 (1969), S. 43-55 
    Details
    ISSN: 1432-0533
    Keywords: Subacute Dementia ; Jakob-Creutzfeldt Disease ; Brain Biopsy ; Histochemistry ; Electron Microscopy ; Basement Membrane ; Astroglia Dilatation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die elektronenoptische und histochemische Untersuchung von Biopsiematerial bei zwei Fällen subakuter Demenz ergab Neurone mit reichlich Lipofuscin-Depots sowie erhöhter saurer Phosphatase-Aktivität. Obwohl diese Veränderungen eine Nervenzellerkrankung anzeigen dürften, werden sie wegen ihrer Ähnlichkeit sowie wegen des Vorliegens anderer, spezifischerer Zellveränderungen als Sekundärphänomene gedeutet. Im ersten Fall wird als primäre Läsion eine Verdickung der Basalmembran der Gefäße, im zweiten Fall eine Astrogliaschwellung angenommen. Da diese Strukturen wichtige Transportfunktionen haben dürften, könnten diese Anomalien leicht die neuronale Versorgung stören und dadurch die neuronalen Läsionen verursachen. Die Bedeutung des Glykogens in diesen Strukturen wird diskutiert.
    Notes: Summary The electron microscopic and histochemical findings in biopsies of two cases of subacute dementia have revealed neurons containing numerous lipofuscin bodies and increased acid phosphatase. Although these changes are considered to indicate neuron disease, they are believed to represent a secondary process because of their similarity and because other more distinctive cell alterations are present. In the first case, the primary abnormality is believed to be thickening of the vascular basement membrane, while in the second case, astroglial dilatation is considered a primary change. Since these structures appear to have important transport functions, these abnormalities could easily impair the nutrient supply to neurons and, in this way, produce the neuronal alteration. The significance of glycogen in these tissues is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00686140
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  • 35
    Electronic Resource
    Electronic Resource
    Ultrastructural study of a nerve biopsy from a case of early infantile chronic neuropathy (1969)
    Springer
    Acta neuropathologica 13 (1969), S. 131-142 
    Details
    ISSN: 1432-0533
    Keywords: Neuropathy, Chronical ; Hypertrophic Neuritis ; Schwann-Cell ; Onion Bulb ; Electron Microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die wesentlichen Veränderungen bei dem mitgeteilten Fall von chronischer frühinfantiler Neuropathie bestehen in einer Modifikation der Schwann-Zellen, die zur Bildung eines konzentrischen Netzwerkes von Lamellen führt. Dieses wird durch eine doppelkonturierte Hülle der Basalmembran um zahlreiche große bemarkte und unbemarkte Fasern gebildet. Die Anomalien der Markscheiden sowie die Häufigkeit von Desmosomen sind bemerkenswert. Diese Besonderheiten unterscheiden diesen Fall von anderen, bisher beschriebenen chronischen Neuropathien. Trotzdem erscheint es derzeit nicht möglich, eine Aussage über die Spezifität der ultrastrukturellen Befunde am untersuchten Nerven zu treffen.
    Notes: Summary The principal lesion in this case of chronic early infantile neuropathy is a modification of the Schwann cell resulting in the formation of a concentric network of lamellae formed by a double-layered sheet of basement membrane around numerous, large myelinated and unmyelinated fibers. The abnormalities in the myelin sheaths and the frequency of desmosomes are noteworthy. These peculiarities distinguish this case from other chronic neuropathies described up to now. Nevertheless, it is impossible to say at present whether the ultrastructural aspect of the nerve studied here is in any way specific.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00687025
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  • 36
    Electronic Resource
    Electronic Resource
    Structural changes of the central nervous system in swayback (enzootic Ataxia) of lambs (1969)
    Springer
    Acta neuropathologica 12 (1969), S. 307-313 
    Details
    ISSN: 1432-0533
    Keywords: Swayback of Lambs ; Electron Microscopy ; Corpus Callosum ; Myelogenesis ; Axonal Changes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Elektronenmikroskopische Untersuchung des Corpus callosum normaler Lämmer und von solchen mit „Swayback” (enzootische Ataxia) ergab den morphologischen Nachweis normaler Myelinentwicklung in beiden Tiergruppen. Von zwei Zellfortsätzen umgebene Axone wurden häufig beobachtet. Reaktive Veränderungen wurden in Axonen der „Swayback”-Lämmer gefunden. Die Bedeutung dieser Befunde wird besprochen.
    Notes: Summary An electron microscopic study of the corpus callosum of normal and swayback lambs has revealed morphological evidence of normal myelinogenesis in both groups of animals. Axons wrapped by two cell processes were frequently encountered. Reactive changes were found in axons in the swayback lambs. The significance of these findings is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809127
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    Electron microscopic study of metachromatic leucodystrophy (1969)
    Springer
    Acta neuropathologica 13 (1969), S. 149-156 
    Details
    ISSN: 1432-0533
    Keywords: Electron Microscopy ; Leucodystrophy, Metachromatic ; Enzyme Histochemistry, Electronmicroscopical ; Lysosomes ; Neurochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Dans la leucodystrophie métachromatique, les lipides anormaux s'accumulent dans les lysosomes des cellules gliales et des phagocytes. Les inclusions lipidiques les moins organisées sont les plus riches en phosphatases acides. Celles dont l'ultrastructure est prismatique ont une activité enzymatique très faible et semblent plus proches de corps résiduels que de lysosomes actifs. Il semble que l'absence d'arylsulfatase lysosomiale induise la persistance des sulfatides accumulés dans les lysosomes alors que les autres lipides provenant de la dégénérescence myélinique, seraient normalement catabolisés. Un remaniement progressif de l'ultrastructure du contenu des lysosomes en est la conséquence.
    Notes: Summary In metachromatic leucodystrophy abnormal lipids are stored within the lysosomes of the glial cells and phagocytes. The lipid inclusions which are the less structured are the richest in acid phosphatases. Those of which the ultrastructure is prismatic show a very low enzymatic activity and are more similar to residual bodies than to active lysosomes. It appears that the lack in lysosomal arylsulfatase leads to an accumulation of the sulfatide moiety of the stored lipids while the other lipids originating from the myelin breakdown, would be normally catabolized. This leads to a progressive transformation of the ultrastructure of the lysosome contents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00687027
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    Electron histochemical demonstration of gangliosides in normal and Tay-Sachs brain tissue (1969)
    Springer
    Acta neuropathologica 13 (1969), S. 157-168 
    Details
    ISSN: 1432-0533
    Keywords: Gangliosides ; Tay-Sachs Disease ; Brain Subcellular Localization ; Hale Stain ; Electron Microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die Reaktion von kolloidalem Eisen mit Sialomucinen (Hale stain) wurde zur elektronenmikroskopischen Darstellung der neuraminsäurehaltigen Ganglioside in den subcellulären Fraktionen des Gehirns angewandt. Zunächst wurde mit Hilfe tritiummarkierter Ganglioside überprüft, ob bei der Gewinnung subzellulärer Fraktionen Ganglioside nicht unspezifisch subcellulär adsorbiert werden. Eine nennenswerte Adsorption konnte ausgeschlossen werden. Das Verfahren wurde zuerst auf die aus Meerschweinchengehirnen isolierten Fraktionen angewandt. Da Nervenendigungen, Mitochondrien und Synapsenbläschen Hale-positiv reagierten, dienten Enzyminkubationen mit Neuraminidase und Hyaluronidase zur Differenzierung von anderen Hale-positiven sauren Substanzen. Schließlich wurde die Methode auf die cytoplasmatischen multilamellären Körperchen (MCB) übertragen, die aus Gehirnen an Tay-Sachs'scher Krankheit Verstorbener isoliert wurden. Aus den Versuchen konnte abgeleitet werden, a) daß die Hale-Färbung auch Ganglioside anfärbt, b) daß Ganglioside auf der Oberfläche der Membran von den multilamellären Körperchen und mit hoher Wahrscheinlichkeit auch auf der Membran der Nervenendigungen lokalisiert sind, c) daß die Synapsenbläschen eine positive Reaktion ergeben, die jedoch nicht mit Sicherheit auf vorhandene Ganglioside zurückgeführt werden kann, d) daß die äußere Mitochondrienmembran Hale-positive Substanzen enthält, deren Natur unbekannt ist.
    Notes: Summary The reaction of colloidal ferric oxide with sialomucins (Hale stain) was applied to sialic acid-containing gangliosides in subcellular fractions of the brain, in order to investigate their localization by electron microscopy. Prior to all experiments, a check was made, by means of tritium-labeled ganglioside, to confirm that the ganglioside content in the subcellular particles was not the result of an unspecific adsorption during the isolating procedure. No considerable unspecific adsorption could be registered. Hale stain was first applied to subcellular fractions obtained from guinea-pig brains. Since nerve-endings, mitochondria and synaptic vesicles gave a positive staining reaction, incubations with neuraminidase and hyaluronidase were carried out in order to achieve a differentiation. Finally, the method was applied to the membranous cytoplasmic bodies (MCB) which were isolated from the brain of a patient with Tay-Sachs disease. It was concluded that: a) Hale stain stains gangliosides also, b) gangliosides are localized in the membrane of membranous cytoplasmic bodies and also very probably in the membrane of nerve-endings, c) synaptic vesicles give a Hale-positive reaction which cannot with certainty be attributed to gangliosides, d) the outer membrane of mitochondria contains Hale-positive substances, the nature of which is not known.
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    Electron microscope study of the rat brain with experimental sodium azide intoxication (1969)
    Springer
    Acta neuropathologica 14 (1969), S. 185-193 
    Details
    ISSN: 1432-0533
    Keywords: Hypoxia ; Sodium Azide ; Electron Microscopy ; Ferritin ; Capillary Permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Experimentelle histotoxische Hypoxämie wurde in Ratten durch Natriumacid-Vergiftung erzeugt. Die mikroskopische Untersuchung der Hirne ergab keine Veränderung, aber bei der elektronenmikroskopischen Untersuchung fanden sich als Frühveränderungen in der Hirnrinde und im Subcortex eine Erweiterung der intercellulären Räume und eine Anschwellung der pericapillären Astrocytenfortsätze. Ferritinalbumin-Mischung, die als Indicator des Eiweißtransportes benutzt wurde, zeigte keine Vermehrung der Capillarpermeabilität. Es wird vermutet, daß Natriumacid den Wasserstoffwechsel beeinträchtigt, wobei es eine osmotische Ausgleichstörung im Gehirn erzeugt.
    Notes: Summary Histotoxic hypoxia was experimentally produced in the rat brain by sodium azide intoxication. In spite of the absence of light microscopic alterations, electron micrographs showed the early changes in the cerebral cortex and subcortex which consisted of widening of the intercellular space and swelling of the pericapillary astrocytic end-feet. However, ferritin-albumin mixture, used for the tracer of protein transport, did not show any increase in the capillary permeability. Sodium azide was considered to disturb the water metabolism, producing osmotic unbalance in the brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00685298
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    Electron microscopic studies concerning the structural mechanism of the development of mental disturbance in experimental chronic methamphetamine poisoning (1969)
    Springer
    Acta neuropathologica 14 (1969), S. 215-225 
    Details
    ISSN: 1432-0533
    Keywords: Methamphetamine Poisoning (Artificial Psychosis) ; Synapses ; Nerve Conduction and Transmission ; Electron Microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Amphetaminchlorid in Mengen von 1 mg pro kg pro Tag wurde 8 männlichen Meerschweinchen ungefähr 1 Jahr lang täglich injiziert, um eine chronische Amphetaminvergiftung zu erzeugen. Bei jedem vergifteten Tier wurde die Feinstruktur des Gehirns elektronenmikroskopisch untersucht. Die Befunde waren folgende: 1. Verschmelzung der Membranen zwischen Axonen in den Nervenendigungen sowie zwischen Axonen und Dendriten wurden in der Großhirnrinde, im limbischen System, im Thalamus und Hypothalmus beobachtet; ferner wurde eine sich vom Cytoplasma bis zur Nervenendigung erstreckende Membranstruktur in diesen Hirnbereichen festgestellt. 2. Im Frontal-, Parietal-, Temporal- und Occipitalhirn sowie im limbischen System fanden sich vermehrt membranbegrenzte Vesikel im Cytoplasma der Nervenzellen und verdicktes und vermehrtes ER in den Nervenfasern. In Anbetracht klinischer Symptome der Patienten mit Amphetaminvergiftung wurde angenommen, daß die Verschmelzung von Membranen zwischen Nervenfortsätzen und das Auftreten der Membranstrukturen in allen Teilen des Nervenzellcytoplasmas vom Perikaryon bis zur Nervenendigung die wichtigsten Befunde sind, die darauf hindeuten, daß die Vergiftungsvorgänge einen wesentlichen Einfluß auf das Leitungssystem der Nerven ausüben können.
    Notes: Summary In 8 male albino strain guinea pigs, 1 mg/kg of methamphetamine HCl was injected daily for 7 months to 1 year to produce chronic methamphetamine intoxication and to study the fine structure of the brain electron microscopically. The following results were obtained: 1. Coalescence of membranes, between axons at the nerve endings and between axons and dendrites, was found in the cortex of the cerebrum and limbic system, in the thalamus and hypothalamus. Membranous structures were found in all portions of the cytoplasm of the nerve cells. 2. Within the cytoplasm of the nerve cell, coated vesicles were increased in number with hypertrophy and increase of endoplasmic reticulum within nerve fibres in the frontal, parietal, temporal and occipital regions, and in the limbic system. In view of these findings, as well as the clinical neurological symptoms in patients with methamphetamine poisoning, the coalescence of membranes between nerve processes and the appearance of membranous structures in all portions of nerve cell cytoplasm from body to nerve endings appear to represent the most important findings, they probably produce a profound disturbance in the system of nerve conduction and transmission.
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    URL: http://dx.doi.org/10.1007/BF00685301
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    Electronic Resource
    Bildung von markscheidenähnlichen Spiralstrukturen durch lamelläre Astrocytenausläufer innerhalb subpialer und perivasculärer Gliosen des Säugetiergehirns (1969)
    Springer
    Acta neuropathologica 12 (1969), S. 98-102 
    Details
    ISSN: 1432-0533
    Keywords: Marginal Siderosis ; Electron Microscopy ; Myelin-Sheath-Like Structures ; Plaques Fibromyéliniques ; Gliosis, Perivascular, Subpial
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei Kaninchen mit einer experimentell erzeugten Randzonensiderose des Zentralnervensystems konnten elektronenmikroskopisch in der Großhirnrinde eigentümliche Spiralstrukturen beobachtet werden. Diese Spiralen fanden sich vornehmlich im Bereich von subpialen und perivasculären Gliosen vor. Sie bestanden aus äußerst dünnen lamellären Astrocytenausläufern, welche um andere astrocytäre Zellfortsätze oder um Dendriten aufgewickelt waren. Die spiralisierten Astrocytenausläufer wiesen in ihrem Inneren feine Filamente mit einer ziemlich regelmäßigen Anordnung auf. In radiärer Richtung ließen die astrocytären Lamellenspiralen eine periodische Schichtung erkennen, welche etwas an die von echten Markscheiden erinnerte. Es wird in Betracht gezogen, daß sie das submikroskopische Äquivalent der sog. Plaques fibromyéliniques darstellen.
    Notes: Summary Peculiar spiral structures could be observed by electron microscopy in the cerebral cortex of rabbits with an experimentally produced marginal siderosis of the central nervous system. These spirals were found predominantly within areas of subpial and perivascular gliosis. They consisted of extremely thin lamellar astrocyte extensions winding around other astroglial processes or dendrites. The spirally coiled astrocyte extensions exhibited within their interior fine filaments having a rather regular arrangement. In the radial direction, the astrocytic lamellae spirals showed a periodic stratification somewhat resembling that of true myelin-sheaths. They were considered to represent the submicroscopic equivalent of the socalled plaques fibromyéliniques.
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    URL: http://dx.doi.org/10.1007/BF00685315
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    Electronic Resource
    Changes at the nodes of ranvier during wallerian degeneration: an electron microscope study (1969)
    Springer
    Acta neuropathologica 14 (1969), S. 237-249 
    Details
    ISSN: 1432-0533
    Keywords: Electron Microscopy ; Wallerian Degeneration ; Nodal Changes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Es wird über ultrastrukturelle Veränderungen in den Ranvierschen Knoten des N.suralis der Ratte im Laufe der Wallerschen Degeneration berichtet. Die Untersuchungen erfolgten 12 und 120 Std nach einer örtlichen Quetschungsverletzung. Die ersten bemerkbaren Veränderungen finden sich im Axon. Nodale und paranodale Anhäufungen von Mitochondrien, multivesikulären und lamellären Körpern, wie auch kleinen blasen- und röhrenartigen Bildungen sind teilweise in den Knoten sichtbar und am deutlichsten nach 24–36 Std erkennbar. Gleichzeitig erfolgt eine Aufsplitterung der Neurofilamente und Neurotubuli, die ihre Liniengestaltung verlieren und sich zusammenballen. Die Zone der erhöhten Dichte gerade unterhalb des nodalen Axolemmas bleibt erhalten. Veränderungen im Myelin beginnen etwas später und bestehen in einem vesikulären Verfall der Endomyelinlamellen und einer Trennung der Endomyelinschlaufen vom Axolemma durch Schwannzellenfortsätze. Dieser Vorgang schien mit einem Zurückziehen des Myelins vom Knoten im Zusammenhang zu stehen. Schwannzellenfortsätze erstrecken sich auch so weit, daß sie das nodale Axon bedecken, wobei sie die nodalen Schwannzellenfortsätze vom Axolemma trennen. Das Endstadium ist die Unterbrechung des nodalen Axons und die Verschmelzung der Myelinenden als Teil der Ovoidbildung.
    Notes: Summary Observations are reported on the ultrastructural alterations at the nodes of Ranvier in the rat sural nerve during the course of Wallerian degeneration. These were examined between 12 and 120 hours after a localized crush injury. The earliest detectable changes are in the axon. Nodal and paranodal accumulations of mitochondria, multivesicular bodies, lamellar bodies and small vesicular and tubular profiles are seen at a proportion of the nodes and are most evident at 24–36 hours. Concomitantly with this, the neurofilaments and neurotubulus fragment, lose their alignment and clump together. The zone of increased density just beneath the nodal axolemma is preserved. Changes in the myelin begin slightly later and consist of vesicular breakdown of the terminal myelin lamellae, and separation of the terminal myelin loops from the axolemma by Schwann cell processes. The latter event appeared to be associated with retraction of the myelin from the node. Schwann cell processes also extend to cover the nodal axon, separating the Schwann cell nodal processes from the axolemma. The final stage is the interruption of the nodal axon and the fusion of the ends of the myelin as part of ovoid formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00685303
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    Electronic Resource
    Intranucleäre stabförmige Gebilde bei einem Oligodendrogliom (1969)
    Springer
    Acta neuropathologica 13 (1969), S. 289-293 
    Details
    ISSN: 1432-0533
    Keywords: Oligodendroglioma ; Nuclear Inclusions ; Electron Microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Es wird die Ultrastruktur von intranucleären stabförmigen Gebilden bei einem Oligodendrogliom beschrieben.
    Notes: Summary Ultrastructure of intranuclear rodlets in an oligodendroglioma is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00690649
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    Electronic Resource
    Familial spongy degeneration of the central nervous system (Van Bogaert-Bertrand disease) (1969)
    Springer
    Acta neuropathologica 12 (1969), S. 103-115 
    Details
    ISSN: 1432-0533
    Keywords: Spongy Degeneration of the CNS ; Van Bogaert-Bertrand-Disease ; Electron Microscopy ; Astrocytic Mitochondria ; Abnormal Cerebral Edema
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Es wird über licht- und elektronenoptische Untersuchungen an Muskel-und Hirnbiopsien eines Falles von spongiöser Degeneration des ZNS berichtet. Die in der grauen und weißen Hirnsubstanz enthaltenen Vacuolen entsprechen a) Spalten in den Markscheiden infolge Aufsplitterung an der intraperiodischen Linie und b) geschwollenen Astrocytenperikaryen und-fortsätzen. Ungewöhnliche Mitochondrien mit Gehalt an kristallinem Material fanden sich nur in Astrocyten. Die ultrastrukturellen Befunde entsprechen denen des Hirnödems. Es wird angenommen, daß die Astroglia eine primäre Rolle in der Flüssigkeitsansammlung spielt, während die Markscheidenschwellung als eine Sekundärläsion aufgefaßt wird. Die mögliche Bedeutung abnormer Astrocyten-Mitochondrien wird diskutiert.
    Notes: Summary Light and electron microscopy study of skeletal muscle and cerebral biopsies from a case of spongy degeneration of central nervous system is reported. The multiple vacuoles present in cerebral gray and white matter correspond to (a) clefts within myelin sheaths resulting from splitting at the intraperiod line and (b) swollen astrocytic perikarya and processes. Unusual mitochondria containing crystalline-like material were observed only in astrocytes. The ultrastructural findings are consistent with cerebral edema. It is suggested that the astrocytes play a primary role in the fluid accumulation while the myelin swelling is a secondary lesion. The possible role of the abnormal astrocytic mitochondria is discussed.
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    URL: http://dx.doi.org/10.1007/BF00692500
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    Electronic Resource
    Abnormal sarcolemmal nuclei encountered in several cases of dystrophia myotonica (1969)
    Springer
    Acta neuropathologica 12 (1969), S. 183-188 
    Details
    ISSN: 1432-0533
    Keywords: Dystrophia myotonica ; Electron Microscopy ; Sarcolemmal Nuclei ; Myofibrillar Material
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung In fünf Fällen von Dystrophia myotonica zeigte die elektronenoptische Untersuchung von bioptisch entnommenem Material zentrale und subsarkolemmale Kerne, die komplexe vacuoläre Areale um myofibrilläres Material enthalten. Diese bisher nicht beobachtete Veränderung könnte durch Verlagerung von myofibrillärem Material in den Kern während seiner Wanderung in das Faserzentrum durch Invagination, aber nicht Durchbrechung der Kernmembran bedingt sein.
    Notes: Summary In five cases of dystrophia myotonica electron microscope preparations of muscle taken at biopsy showed both centrally placed and subsarcolemmal nuclei containing complex vacuolar areas enclosing myofibrillar material. It is suggested that this appearence, which has not been seen in any other condition, may be due to the forcing of myofibrillar material into the nucleus during its migration to the centre of the fibre invaginating but not breaching its membrane.
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    URL: http://dx.doi.org/10.1007/BF00692505
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  • 46
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    Electronic Resource
    Electron microscopic studies on the cerebral lesions of rats in experimental carbon monoxide poisoning (1969)
    Springer
    Acta neuropathologica 14 (1969), S. 118-125 
    Details
    ISSN: 1432-0533
    Keywords: Carbon Monoxide Poisoning ; Electron Microscopy ; Myelin Disintegration ; Cerebral Anoxia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Nach experimenteller CO-Vergiftung fanden sich schwerere und ausgedehntere Läsionen in der weißen als in der grauen Hirnsubstanz. Zwischen akuter und chronischer CO-Vergiftung ergaben sich keine wesentlichen qualitativen Unterschiede der Hirnveränderungen. Die Läsionen nach chronischer Intoxikation waren jedoch schwerer als nach akuter Vergiftung. Die Nervenzellen zeigten leicht dilatiertes oder fragmentiertes EPR und Golgi-Komplexe, doch boten die Mitochondrien meist keine pathologischen Veränderungen. Bei chronischen Fällen fand sich gelegentlich eine deutliche Schwellung des EPR von Oligodendrogliazellen. Die Capillaren blieben intakt und die perivasalen Astrogliaendfüßchen waren nicht geschwollen. Im Mark kam es zu teilweisem Ausfall der normalen Markscheidenbestandteile. Die Marklamellen zeigten mäßige Exfoliation sowie eine Umwandlung in homogene oder strukturlose Substanz. Bemarkte Axone waren teilweise kontrahiert und zeigten auf Querschnitten unregelmäßige Form. Gelegentlich fand sich eine Vergrößerung der axonalen Mitochondrien und Zerstörung ihrer inneren Parallelstrukturen. Als Hauptfaktoren in der Pathogenese der Hirnveränderungen nach experimenteller CO_Vergiftung werden zerebrale Anoxie infolge CO-Hämoglobinbildung, cytotoxische Wirkung von CO auf das Hirngewebe und eine Störung der Blutzirkulation angenommen.
    Notes: Summary In experimental carbon monoxide poisoning, more marked and widespread pathological changes in the brain were seen in the white matter as compared with the gray matter. No essential difference, in the appearance of cerebral alterations, was detected between acute and chronic carbon monoxide poisoning. It was confirmed that the changes resulting from chronic poisoning showed a higher degree of severity as compared with those resulting from acute poisoning. Nerve cells with slightly dilated or fragmented endoplasmic reticulum and Golgi complex in the gray matter were found infrequently. However, most mitochondria did not show any kind of abnormality in such cells. A remarkable dilatation of the endoplasmic reticulum of oligodendrocytes was sometimes seen in chronic cases. Capillaries remained intact and astrocytic perivascular foot-plates were not swollen. In the white matter, the normal constituents of the myelin sheath were partially lost and the myelin lamellae showed moderate exfoliation, or a change into homogenous or structureless substance. Myelinated axons were partially contracted and showed an irregularity in shape in transverse sections. Enlargement of occasional axonal mitochondria and the destruction of their internal parallel structures were observed. Cerebral anoxia caused by carboxyhaemoglobin, together with the cytotoxic action of carbon monoxide on the brain tissue and the disturbance of blood circulation in the brain are suggested as the chief factors in the pathogenesis of the cerebral alterations induced by experimental carbon monoxide poisoning.
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    URL: http://dx.doi.org/10.1007/BF00686348
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    Electron microscopic alterations in the vicinity of epileptogenic cobalt-gelatine necrosis in the cerebral cortex of the rat (1969)
    Springer
    Acta neuropathologica 14 (1969), S. 201-214 
    Details
    ISSN: 1432-0533
    Keywords: Electron Microscopy ; Epilepsy, Experimental ; Focus ; Cobalt Gelatine ; Plasmatic Infiltration ; Brain Edema
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei 25 erwachsenen Ratten wurde ein epileptogener Kobaltgelatineherd in einer Standardregion der Hirnrinde erzeugt. Die Tiere wurden am 1., 3., 5., 8., 14. 21. und 28. Tag nach der Operation getötet. Das Gebiet des epileptogenen Herdes wurde elektronenmikroskopisch untersucht. Die frühesten Veränderungen bestanden in ödem. Später traten Veränderungen der Astrocytenfortsätze auf, die sich an die Basalmembranen der Capillaren anlegten; die Intercellularräume erweiterten sich, füllten sich mit elektronenoptisch dichten Massen und entwickelten ein “plasmatisches Infiltrat”. Allmählich breitete sich dieses Exsudat weiter um die Capillaren aus; es trat an Orten auf, wo die Astrocytenfortsätze und die Dendriten schwer geschädigt waren und erfüllte die weiteren Intercellularräume des Neuropils. Die Nervenzellen zeigten eine auffallende Widerstandsfähigkeit gegenüber diesem pathologischen Prozeß. Manchmal waren sie umschlossen von Exsudatmassen und zum Teil oder ganz der zarten neuralen und Astrocytenfortsätze beraubt, von denen sie normalerweise umgeben sind. Unsere Befunde werden als das ultrastrukturelle Korrelat der Schols'schen “plasmatischen Infiltration” interpretiert.
    Notes: Summary In 25 adult rats an epileptogenic cobalt-gelatine focus was produced in a standard region of the cerebral cortex. The animals were killed successively on the 1st, 3rd, 5th, 8th, 14th, 21st and 28th day after operation and the region of the epileptogenic focus was examined electron microscopically. The earliest changes were those of oedema. Later there occurred disturbances of the astrocytic processes which cling to the basement membranes of the capillaries; the intercellular spaces widened and filled with rather E. M. dense masses and a “plasmatic infiltrate” developed. Gradually this exudative substance spread even further from the capillaries. It appeared in places where the astrocytic processes were severely demaged and the dendrites were partly dissipated and it filled out the wide intercellular spaces of the neuropil. The nerve cells showed a striking resistance toward this pathological process. Sometimes they floated in the exudative masses but were partly or totally deprived of the fine neural and astrocytic processes which normally surround them. Our findings are interpreted as the ultrastructural correlate of Scholz's “plasmatic infiltration”.
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    URL: http://dx.doi.org/10.1007/BF00685300
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    Étude d'une nouvelle observation de «Nemaline Myopathy» (1969)
    Springer
    Acta neuropathologica 13 (1969), S. 250-266 
    Details
    ISSN: 1432-0533
    Keywords: Electron Microscopy ; Congenital Myopathy ; Nemaline Myopathy ; Z-band Structure ; Sarcoplasmic Masses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé L'étude ultrastructurale d'une observation de «Nemaline-Myopathy» a été centrée sur les rapports structurels entre bâtonnets et stries Z normales dans différentes conditions de fixation. L'aspect des stries Z, en section transversale, varie en effet avec la fixation: réseau de ponts «obliques» (par rapport à l'alignement quadratique régulier des terminaisons des filaments fins) après fixation osmiée, réseau de ponts «transversaux», isolé ou superposé au premier réseau, après fixation aldéhydique initiale. L'aspect des bâtonnets en section transversale varie également avec la fixation; la disposition quadratique des filaments constitutifs des bâtonnets est visible après l'une et l'autre fixation, mais un réseau quadratique régulier, de 75 Å de côté, n'est clairement apparent qu'après fixation aldéhydique. Le point important est que ce dernier aspect diffère complètement du réseau «oblique» des stries Z normales, et peut être rapproché au contraire du réseau «transversal» de la strie Z obtenu après fixation aldéhydique; l'hypothèse est ainsi soulevée de la constitution des ponts dans les bâtonnets aux dépens d'un seul des deux constituants morphologiques de la strie Z. La topographie des bâtonnets a été également étudiée: tantôt périphérique, au sein de masses sarcoplasmiques latérales, tantôt centrale, au sein de petits foyers de désintégration myofibrillaire. La structure des plaques motrices visibles dans les préparations était normale. La spécificité de la lésion élémentaire et l'autonomie de ce type de myopathie sont ensuite discutées.
    Notes: Summary Ultrastructural study of an observation of “Nemaline Myopathy” has been focused on structural relationships between rods and normal Z-bands in different conditions of fixation. The Z-band structure studied in transversal section, varies with the fixation: network of “oblique” (relative to the regular quadratic pattern of the thin filament endings) bridges after osmic fixation; network of “transversal” bridges, alone or associated to the first network, after aldehydic fixation. The rod structure, in transversal section, is also varying with the fixation: a quadratic disposal of the filamentary content is visible after both fixations, but a regular quadratic network, 75–85 Å side, is clearly appearent only after aldehydic fixation. This last network differs from the “oblique” network of the normal Z-band; it can be compared to the “transversal” one obtained in the Z-band after aldehydic fixation. The hypothesis that bridges in the rods are formed only by one of the two normal morphological components of the Z-band, is raised. Topography of the rods in muscle fibers has been studied: either in peripheral sarcoplasmic masses, or in small central-located foci of myofibrillar disintegration. The end-plates structure was normal. Specificity of the elementary lesion, and autonomy of that type of myopathy is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00690645
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  • 49
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    Electronic Resource
    Sodium demonstration in rat cerebrum following perfusion with hydroxyadipaldehyde-antimonate (1969)
    Springer
    Acta neuropathologica 12 (1969), S. 173-182 
    Details
    ISSN: 1432-0533
    Keywords: Sodium Deposits ; Electron Microscopy ; Perfusion with Hydroxyadipaldehyde-Antimonate ; Extracellular Space
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Eine Modifikation der Methode zur ultrastrukturellen Darstellung von Natrium wird beschrieben, die eine Perfusion mit leicht alkalischer Mischung von Hydroxydipaldehyd, Phosphatpuffer und Kalium-Pyro-Antimonat verwendet. Im normalen Gehirn werden keine Natrium-Deposite angetroffen. Das spricht dafür, daß im Gehirn keine intraoder extracelluläre Konzentration über 150 mM vorliegt. Bei Vorliegen hoher NaCl-Konzentration sieht man ein großes, dichtes Präcipitat, das nach direkter Injektion in den extracellulären Räumen, Neuronen und Astrocyten lokalisiert werden kann. Im Mark der vergifteten Ratten findet sich ähnlich wie nach direkter Natrium-Injektion ein diskretes, gleichfalls als Natrium aufgefaßtes Präcipitat an der Oberfläche von Oligodendrogliazellen, aber nicht innerhalb dieser Zellen. Ein elektronendichtes Deposit unklarer Herkunft findet sich in den Myelinspalten, die nach akuter TET-Vergiftung auftreten. Der Wechsel in Charakter und Lokalisation dieser elektronendichten Partikel mahnt zur Vorsicht in ihrer Interpretation bei histochemischen Untersuchungsmethoden.
    Notes: Summary A modification of the technique for the ultrastructural demonstration of sodium is described which involves a perfusion with a slightly alkaline mixture of hydroxyadipaldehyde, phosphate buffer and potassium pyroantimonate. No sodium deposits are found in normal brain indicating that no intra or extracellular concentration exceeding 150 mM is present in the brain. In the presence of high concentration of NaCl, a large dense precipitate can be seen which after a direct injection can be localized to extracellular spaces, neurons and astrocytes. In the white matter of tin poisoned rats, as well as after the direct injection of sodium, a discrete precipitate, also believed to represent sodium, is noted at the surface of oligodendrocytes but not within these cells. An electron dense deposit of dubious origin is present in the myelin clefts which occur as a result of acute triethyltin intoxication. The variations in the character and localization of these electron dense particles emphasize the caution which is required in their interpretation following histochemical procedures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00692504
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  • 50
    Electronic Resource
    Electronic Resource
    Züchtung und Vermehrung von Herpes simplex-Virus in Zellkulturen vom Nervensystem (1969)
    Springer
    Acta neuropathologica 12 (1969), S. 276-299 
    Details
    ISSN: 1432-0533
    Keywords: Herpes simplex Virus ; CNS Tissue Culture ; Multiplication in vitro ; Cytopathic Alterations ; Electron Microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die häufig diskutierte, (Mit)beteiligung von Herpes simplex-Virus (HSV) bei bestimmten Alterationen im ZNS sowie der hohe Neutropismus des HSV führte zur Frage, inwieweit sich HSV auch in in vitro gezüchteten, spezifischen Zellen vom Nerven-system vermehren und züchten läßt, und ob sich hierbei licht-und elektronenmikroskopisch charakteristische Alterationen nachweisen lassen. Es zeigte sich, daß sich das HSV in allen verschiedenen angezüchteten spezifischen Zellen (von Plexus chorioideus des Rhesusaffen, Kaninchenspinalganglien, menschlichen Oligodendrogliomen, Meningeomen sowie fibrillären und protoplasmatischen Astrocytomen) kultivieren und vermehren läßt. Hierbei kommt es in den spezifischen Zellen nicht nur lichtmikroskopisch zu charakteristischen cytopathischen Veränderungen, sondern auch biologisch zu einer signifikanten Vermehrung des Virus in diesen Zellen. Auch elektronenmikroskopisch lassen sich viele der charakteristischen Bildungs-, Reifungs- und Ausschleusungsstadien des Virus in den Kernen und im Cytoplasma der Zellen beobachten. Die Besonderheiten der elektronenmikroskopisch erhobenen ultrastrukturellen Befunde werden ausführlich beschrieben, und die sich daraus abzuleitenden Möglichkeiten werden im Hinblick auf die biologischen Eigenheiten des HSV bei in vivo-Infektionen, aber auch im Hinblick auf die Deutung lichtmikroskopisch histochemischer und immunhistologischer Befunde nach in vivo-Infektionen mit diesem Virus ausführlich diskutiert.
    Notes: Summary The participation of herpes simplex virus (HSV) in certain alterations of the CNS has been partially questioned and frequently discussed. Therefore, the question arose whether HSV can also be cultivated and multiplied in vitro in CNS specific cells, and if so, whether characteristic alterations and structures can be observed by means of light and electron-microscopic examinations. Our data demonstrate that HSV multiplies in all different specific cells originating from plexus chorioideus of rhesus monkeys, from spinal ganglia of rabbit, from human oligodendroglioma, meningeoma as well as from fibrillar and protoplasmatic astrocytoma. Characteristic cytopathic alterations of these specific cells and significant multiplication of the virus in these cells are to be found. Many of the characteristic forms of formation, maturation and release of HSV can be seen by electronmicroscopic examinations. The particular ultrastructural data observed by electron microscopy are described in detail and the resulting possibilities are broadly discussed not only with regard to the biologic particularity of HSV in in vivo infection but also in view of the interpretations, deriving from histochemical and immunohistological data obtained by light microscopy after in vivo infection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00687650
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  • 51
    Electronic Resource
    Electronic Resource
    An electron microscopic study of meningiomas (1969)
    Springer
    Acta neuropathologica 13 (1969), S. 301-323 
    Details
    ISSN: 1432-0533
    Keywords: Meningiomas ; Electron Microscopy ; Endotheliomatous, Fibromatous Type ; Light Cells ; Dark Cells ; Histogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung 17 chirurgisch entfernte Meningiome vom endotheliomatösen und 5 vom fibromatösen Typ wurden elektronenmikroskopisch untersucht. Unterschiede im Entwicklungsgrad der cytoplasmatischen Fortsätze und der Beziehungen zwischen den Plasmamembranen der Tumorzellen wurden in den endotheliomatösen Meningeomen beobachtet. In 4 fibromatösen Tumoren sind die zelligen Areale von bindegewebigen Räumen umgeben. Auch wenn die meisten Tumorzellen helle Zellen sind und sich nicht wesentlich von den Tumorzellen der endotheliomatösen Meningiome unterscheiden, ist die histologische Anordnung der fibromatösen klar von derjenigen der endotheliomatösen Meningeome zu trennen. Ausschlaggebend dafür ist die starke Entwicklung des Bindegewebes. Die Dunkelzellen lassen sich in zwei Typen gliedern: Typ I wird in vier Tumoren mit stark ausgebildetem Bindegewebe angetroffen. Die Analyse der inneren Zellstruktur sowie das Vorliegen von Übergängen zwischen hellen und dunklen Zellen machen es wahrscheinlich, daß diese nur verschiedene Typen einer einzigen Ursprungszelle darstellen. Die Bedeutung dieser verschiedenen Erscheinungsformen der Meningiomzellen wird diskutiert. Die Ultrastruktur der Tumorzellen ähnelt derjenigen der normalen arachnoidalen Zellen. Rückschlüsse auf die blastodermale Herkunft der normalen und tumoralen meninigalen Zellen auf Grund ihrer ultrastrukturellen Merkmale erscheinen verfrüht.
    Notes: Summary Seventeen surgically removed meningiomas of the endotheliomatous and five of the fibromatous type were investigated with an electron microscope. Differences of the development of cytoplasmic processes and the relations between plasma membranes of blastomatous cells were observed in endotheliomatous meningiomas. In four of the fibromatous tumors the cell groups were surrounded by spaces of connective tissue. Although most of the tumor cells were light cells and are not essentially different from the tumor cells of the endotheliomatous meningiomas, the histological structure of fibromatous meningiomas is clearly distinguished from the endotheliomatous type, because of the greater amount of connective tissue. The dark cells may be divided into two types: the first was found in those four tumors, where the connective tissue is well developed, while the second one only occurred in one of the tumors. The analysis of the inner cell structure as well as the presence of interstages between dark and light cells makes it probable that dark and light cells are different types of one original cell. The cause of this different appearance of the menigioma cells is discussed. The fine structure of the tumor cells showed a great similarity with that of normal arachnoidal cells. Conclusions on the blastodermic origin of normal and blastomatous meningial cells on the basis of ultrastructural characteristics, however, seem to be premature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00686120
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  • 52
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    Electronic Resource
    Étude ultrastructurale de quatre cas de leuco-encéphalite sclérosante subaiguë (1969)
    Springer
    Acta neuropathologica 14 (1969), S. 1-13 
    Details
    ISSN: 1432-0533
    Keywords: Subacute Sclerosing Leucoencephalitis ; Electron Microscopy ; Tubular Inclusions ; Inclusion Bodies (Cristalline Rods, Fibrillar Bundles, Nuclear Bodies, Osmiophilic Particles)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Les auteurs rapportent 4 observations caractéristiques de LESS: L'analyse ultra-structurale montre: 10 — des inclusions tubulaires intra-nucléaires neuronales ou gliales et intra-axonales de morphologie superposable à celle des nucléocapsides des myxo-virus, de la rougeole en particulier. 20 — des formations non spécifiques: corps nucléaires, faisceaux cristallins et fibrillaires traduisant un trouble métabolique nucléaire, particules osmiophiles liées à une hyperactivité cellulaire. Les inclusions tubulaires virales sont présentes quelque soit la durée de la maladie (3 mois à 5 ans) indiquant l'absence d'autostérilisation virale dans le S.N.C. La LESS apparaît liée au virus rougeoleux mais le mécanisme indirect immunitaire ou métabolique de cette action est inconnu.
    Notes: Summary Four cases of S.S.L.E are reported. The electron microscopy findings show: 1. Tubulary inclusion bodies: They appear in three cases out of four, either in neuronal and glial nucleus or in axis cylinders. Their morphological features are similar to the nucleocapsides of myxoviruses and particularly measles-virus. 2. Other different types of nonspecific inclusions: nuclear bodies, cristalline-like rods and fibrillar bundles which may be considered as the result of a nuclear metabolic disorder, osmiophilic particles which may be seen as the result of a cellular intracytoplasmic hyperactivity. The tubules are found whatever the duration of the disease (3 months up to 5 years) may be. This might indicate that there is no autosterilization of the virus in the C.N.S. during the course of S.S.L.E. According to the most recent papers, such a disease might be interpreted as an infection indirectly induced by measles-virus with an unknown immunologic or metabolic mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00687698
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  • 53
    Electronic Resource
    Electronic Resource
    The normal sural nerve in man (1969)
    Springer
    Acta neuropathologica 13 (1969), S. 197-216 
    Details
    ISSN: 1432-0533
    Keywords: Peripheral Nerves ; Axons ; Myelin Sheaths ; Schwann Cells ; Electron Microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Eine kombinierte licht- und elektronenmikroskopische Untersuchung am normalen N. suralis von 7 Menschen im Alter von 15–59 Jahren wurde vorgenommen. Qualitative und quantitative Beobachtungen an Schwann-Zellen und Fibroblasten, markhaltigen und marklosen Fasern wurden an isolierten Faszikeln durchgeführt. Schwannzellen überwiegen gegenüber Fibroblasten im Verhältnis von etwa 9:1. Die meisten Schwannzellen (etwa 80%) liegen an marklosen Fasern. Die Faktoren, welche die Dichte dieser Zellen pro Querschnittsareal beeinflußen, werden diskutiert. Einige ultrastrukturelle Befunde an bemarkten Fasern werden beschrieben und ihre Zahl pro mm2 sowie die Häufigkeitsverteilung ihrer Dicke wird angegeben. Eine indirekte Methode zur Bestimmung der mittleren Internodienlänge für jede der Markfasergrößenpopulationen an Querschnitten von Faszikeln normaler Nerven durch Bestimmung des Verhältnisses der markhaltigen Fasersegmente zu ihrer Kernzahl wird vorgeschlagen. Die Ultrastruktur der marklosen Nervenfaern wird beschrieben und die Identifizierung dieser Axone mit extremen Durchmessern diskutiert. Ihre Dichte und Größenfrequenzhistogramme sind die ersten, die am Menschen durch systematische elektronenoptische Untersuchungen veröffentlicht werden. Das mittlere Verhältnis von marklosen zu bemarkten Fasern ist etwa 3,7:1 und schwankt in den Faszikeln der Einzelindividuen.
    Notes: Summary A combined light and electron microscope study of the normal sural nerve in 7 people aged 15–59 years is reported. Qualitative and quantitative studies of the Schwann cells and fibroblasts, myelinated and unmyelinated fibres are made in isolated fascicles. Schwann cells predominate over fibroblasts in the ratio of about 9-1. Most Schwann cells, almost 80%, are attached to unmyelinated fibres. Factors influencing the densities of these cells per cross sectional area are discussed. Some ultrastructural features of the myelinated fibres are described and their numbers per sq.mm and frequency distribution of their sizes are produced. An indirect method is proposed for assessing the mean internodal length for earch of the myelinated fibre size populations in cross sections of fascicles of normal nerves by estimating the proportion of myelinated segments cut through their nucleus. The ultrastructure of unmyelinated fibres is described and the identification of axons of extreme diameter is discussed. Their densities and size frequency histograms are the first to be reported in man by systematic electron microscope studies. The average ratio of unmyelinated to myelinated fibre density is about 3.7:1 though it varies in the fascicles of the different individuals. The implications of axonal diameter in the presence of myelin are commented on.
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    URL: http://dx.doi.org/10.1007/BF00690642
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  • 54
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    Electronic Resource
    Light and electron microscopic study of the muscles in hypokalemic periodic paralysis (1969)
    Springer
    Acta neuropathologica 12 (1969), S. 329-338 
    Details
    ISSN: 1432-0533
    Keywords: Hypokalemic Periodic Paralysis ; Electron Microscopy ; Myopathy ; Sarcoplasmic Reticulum ; Glycogen, Muscular
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Licht- und elektronenoptische Untersuchungen wurden an Muskelbiopsien von 4 Fällen hypokaliämischer periodischer Paralyse durchgeführt. Die frühesten Veränderungen betreffen nach Meinung der Verfasser das sarkoplasmatische Reticulum: Vacuolisierung des Längssystems und vermutlich Multiplikation des Quersystems. Es wird vermutet, daß die Vacuolenbildung die Folge einer Fusion der Vesikeln des Quersystems darstellt. Destruktion von Myofibrillen und Vergrößerung der, interfibrillären Räume treten erst in späteren Phasen des Krankheitsprozesses auf. Ausdehnung und Intensität dieser Veränderungen bedingen das typische histologische Bild myogener Läsionen bei Fällen m klinisch fixierten Symptomen der Myopathie.
    Notes: Summary Light and electron-microscopic studies were performed on the muscles taken from 4 cases with hypokalemic periodic paralysis. The authors conclude that the earliest changes concern the sarcoplasmic reticulum: vacuolisation of the longitudinal system and probably, multiplication of the transverse system. It is suggested, that vacuoles are formed as a result of fusion of the vesicles of the transverse system. Destruction of myofibrilles and enlargement of the interfibrillar spaces appear at a later period of the disease process. Extensive and intensive changes of that kind present a typical appearance of myogenic changes in histological study observed in the cases with clinically fixed symptomes of myopathy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809129
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  • 55
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    Electronic Resource
    The inhibition of calcium hydroxyapatite crystal growth by polyphosphonates and polyphosphates (1969)
    Springer
    Calcified tissue international 3 (1969), S. 151-162 
    Details
    ISSN: 1432-0827
    Keywords: Calcification ; Physiologic ; Phosphonic Acids ; Phosphates ; Crystallization ; Electron Microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé On a étudié la formation de l'hydroxyapatite de calcium cristallin à partir de solutions d'ions de calcium et de phosphate et l'inhibition de la croissance de cristaux de l'hydroxyapatite de calcium au moyen de polyphosphonates et de polyphosphates. Les polyphosphonates, éthane hydroxy-1-diphosphonate-1,1 de disodium et dichlorométhanediphosphonate de disodium, sont inhibiteurs efficaces contre la croissance de cristaux de l'hydroxyapatite de calcium. Les polyphosphates sont aussi inhibiteurs efficaces contre la croissance de cristaux de l'hydroxyapatite de calcium tant que le niveau exigé de polyphosphate intact est présent dans le système. Cependant, à cause de leur instabilité hydrolytique, qui est soulignée par une température élevée, valeur de pH basse, et certaines enzymes, la concentration du polyphosphate diminue avec le tempsin vitro, et son activité comme inhibiteur est perdue. Au contraire aux polyphosphates, les polyphosphonates sont hydrolytiquement stables. Les polyphosphonates sont chimiosorbés sur la surface des microcristallites de l'hydroxyapatite de calcium, ainsi empêchant l'occurrence d'autre croissance de cristaux semblable à l'action d'autres poisons connus de croissance de cristaux. On propose l'extension de cette action sur la formation de l'apatite et cette stabilité des polyphosphonates aux applications médicales et dentaires concernant le metabolisme pathologique de calcium et de phosphate.
    Abstract: Zusammenfassung Die Bildung des kristallinen Calciumhydroxyapatit aus Lösungen, welche Calcium- und Phosphationen enthalten, und die Hemmung der Bildung von kristallinen Calciumhydroxyapatit durch Polyphosphonate und Polyphosphate wurden untersucht. Polyphosphonate, Dinatriumäthan-1-hydroxyl-1,1-diphosphonat und Dinatriumdichloromethandiphosphonate verhindern das Kristallwachstum des Calciumhydroxyapatits. Die Polyphosphate verhindern ebenfalls das Kristallwachstum des Calciumhydroxyapatits, solange die notwendige Konzentration des nicht hydrolysierten Polyphosphats vorhanden ist. Wegen ihrer hydrolytischen Unbeständigkeit, die durch hohe Temperatur, niedrige pH und bestimmte Enzyme erhöht wird, vermindert sich jedoch die Konzentration des Polyphosphats allmählichin vitro, und ihre Hemmungsaktivität geht verloren. Im Gegensatz zu den Polyphosphaten sind die Polyphosphonate hydrolytisch beständig. Die Polyphosphonate werden an der Oberfläche der Mikrokristallite des Calciumhydroxyapatits chemisorbiert und verhindern, wie andere bekannte Kristallwachstumsgifte, auf diese Weise weiteres Kristallwachstum. Die Beständigkeit der Polyphosphonate und ihre Chemisorption an dem Apatit empfehlen ihren Gebrauch in der ärztlichen und zahnärztlichen Praxis, soweit sie den pathologischen Calcium- und Phosphatstoffwechsel betreffen.
    Notes: Abstract The formation of crystalline calcium hydroxyapatite from solutions of calcium and phosphate ions and the inhibition of calcium hydroxyapatite crystal growth by polyphosphonates and polyphosphates have been studied. The polyphosphonates, disodium ethane-1-hydroxy-1,1-diphosphonate and disodium dichloromethane diphosphonate, are effective inhibitors of calcium hydroxyapatite crystal growth. The polyphosphates are also effective inhibitors of calcium hydroxyapatite crystal growth as long as the required level of intact polyphosphate is present in the system. However, because of their hydrolytic instability, which is enhanced by high temperature, low pH, and certain enzymes, the concentration of the polyphosphate decreases with timein vitro, and its activity as an inhibitor is lost. In contrast to the polyphosphates, the polyphosphonates are hydrolytically stable. The polyphosphonates are chemisorbed on the surface of the microcrystallites of calcium hydroxyapatite and, in the manner of other known crystal growth poisons, thus prevent further crystal growth. The stability of the polyphosphonates and their chemisorption on apatite suggest their use in medical and dental applications involving pathological calcium and phosphate metabolism.
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    URL: http://dx.doi.org/10.1007/BF02058658
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