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  • 2000-2004  (57)
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  • 1
    Publikationsdatum: 2020-03-23
    Beschreibung: Die harmonische Integration der Navigation und Suche in lizenzierten Journalen und gleichzeitig in freien digitalen Dokumenten unter einer einheitlichen konsistenten Nutzeroberflache ist eines der ungelösten F&E-Probleme der Fachinformation. Hierfür sollen Elemente des Invisible Web und des Visible Web unter Berücksichtigung offener Standards nahtlos #I miteinander verbunden werden. Dem Projekt liegt ein Modell mit Internet-Index, Metasuche und Open Linking über verteilten heterogenen Speichern #I zu Grunde: Verschiedenste Server, digitale Referenzen in Artikeln und Dokumenten, Links in Datenbanken und auf Bestelldienste sollen unter Berücksichtigung von Standort-, Studien- und Lernbedingungen kooperativ miteinander vernetzt werden. Die Leistungsfähigkeit des Modells soll in Pilotimplementierungen getestet und für eine breite Anwendung vorbereitet werden. Auf dieser Basis soll das Vorhaben Verteilter Zeitschriftenserver der AG der Verbundsysteme in eigenen Teilprojekten kooperativ initiiert werden, das jetzt in das Vorhaben Verteilter Dokumentenserver von vascoda integriert ist.
    Schlagwort(e): ddc:000
    Sprache: Deutsch
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  • 2
    Publikationsdatum: 2014-02-26
    Beschreibung: The mathematical modeling of a special modular catalytic reactor kit leads to a system of partial differential equation in two space dimensions. As customary, this model contains unconfident physical parameters, which may be adapted to fit experimental data. To solve this nonlinear least squares problem we apply a damped Gauss-Newton method. A method of lines approach is used to evaluate the associated model equations. By an a priori spatial discretization a large DAE system is derived and integrated with an adaptive, linearly-implicit extrapolation method. For sensitivity evaluation we apply an internal numerical differentiation technique, which reuses linear algebra information from the model integration. In order not to interfere the control of the Gauss-Newton iteration these computations are done usually very accurately and, therefore, very costly. To overcome this difficulty, we discuss several accuracy adaptation strategies, e.g., a master-slave mode. Finally, we present some numerical experiments.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 3
    Publikationsdatum: 2020-03-06
    Beschreibung: Many real world problems can be mapped onto graphs and solved with well-established efficient algorithms studied in graph theory. One such problem is to find large sets of points satisfying some mutual relationship. This problem can be transformed to the problem of finding all cliques of an undirected graph by mapping each point onto a vertex of the graph and connecting any two vertices by an edge whose corresponding points satisfy our desired relationship. Clique detection has been widely studied and there exist efficient algorithms. In this paper we study a related problem, where all points have a set of binary attributes, each of which is either 0 or 1. This is only a small limitation, since all discrete properties can be mapped onto binary attributes. In our case, we want to find large sets of points not only satisfying some mutual relationship; but, in addition, all points of a set also need to have at least one common attribute with value 1. The problem we described can be mapped onto a set of induced subgraphs, where each subgraph represents a single attribute. For attribute $i$, its associated subgraph contains those vertices corresponding to the points with attribute $i$ set to 1. We introduce the notion of a maximal clique of a family, $\mathcal{G}$, of induced subgraphs of an undirected graph, and show that determining all maximal cliques of $\mathcal{G}$ solves our problem. Furthermore, we present an efficient algorithm to compute all maximal cliques of $\mathcal{G}$. The algorithm we propose is an extension of the widely used Bron-Kerbosch algorithm.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 4
    Publikationsdatum: 2014-02-26
    Beschreibung: We present an integer linear programming model for the design of multi-layer telecommunication networks. The formulation integrates hardware, capacity, routing, and grooming decisions in \emph{any} n umber of network layers. Practical hardware restrictions and cost can accurately be taken into account for technologies based on connection-oriented routing protocols.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 5
    Publikationsdatum: 2014-02-26
    Beschreibung: We introduce FreeLence, a lossless single-rate connectivity compression algorithm for triangle surface meshes. Based upon a geometry-driven traversal scheme we present two novel and simple concepts: free-valence connectivity encoding and entropy coding based on geometric context. Together these techniques yield significantly smaller rates for connectivity compression than current state of the art approaches - valence-based algorithms and Angle- Analyzer, with an average of $36\%$ improvement over the former and an average of $18\%$ over the latter on benchmark 3D models, combined with the ability to well adapt to the regularity of meshes. We also prove that our algorithm exhibits a smaller worst case entropy for a class of "'well-behaved"' triangle meshes than valence-driven connectivity encoding approaches.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 6
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    Publikationsdatum: 2019-10-24
    Schlagwort(e): ddc:000
    Sprache: Deutsch
    Materialart: annualzib , doc-type:report
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  • 7
    Publikationsdatum: 2020-02-11
    Beschreibung: In this article, we present a mathematical model and an algorithm to support one of the central strategic planning decisions of network operators: How to organize a large number of locations into a hierarchical network? We propose a solution approach that is based on mixed-integer programming and Lagrangian relaxation techniques. As major advantage, our approach provides not only solutions but also worst-case quality guarantees. Real-world scenarios with more than 750 locations have been solved within 30 minutes to less than 1\% off optimality.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 8
    Publikationsdatum: 2020-02-11
    Beschreibung: This paper is concerned with UMTS radio network design. Our task is to reconfigure antennas and the related cells as to improve network quality. In contrast to second generation GSM networks, \emph{interference} plays a paramount role when designing third generation radio networks. A known compact formulation for assessing the interference characteristics of a radio network as coupling relations between cells based on user snapshots is generalized to statistical average load. This enables us to overcome the notorious difficulties of snapshot-based network optimization approaches. We recall a mixed-integer programming model for the network design problem that is based on user snapshots and contrast it with a new network design model based on the average coupling formulation. Exemplarily focusing on the important problem of optimizing antenna tilts, we give computational results for a fast local search algorithm and the application of a MIP solver to both models. These results demonstrate that our new average-based approaches outperform state-of-the-art snapshot models for UMTS radio network optimization.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 9
    Publikationsdatum: 2021-08-05
    Beschreibung: Constraint Programs and Mixed Integer Programs are closely related optimization problems originating from different scientific areas. Today's state-of-the-art algorithms of both fields have several strategies in common, in particular the branch-and-bound process to recursively divide the problem into smaller sub problems. On the other hand, the main techniques to process each sub problem are different, and it was observed that they have complementary strenghts. We propose a programming framework {\sffamily SCIP} that integrates techniques from both fields in order to exploit the strenghts of both, Constraint Programming and Mixed Integer Programming. In contrast to other proposals of recent years to combine both fields, {\sffamily SCIP} does not focus on easy implementation and rapid prototyping, but is tailored towards expert users in need of full, in-depth control and high performance.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 10
    Publikationsdatum: 2018-12-06
    Beschreibung: In this paper we describe the semantic analysis of differential equations given in the ubiquitous semi-structured formats MathML and OpenMath. The analysis is integrated in a deployed Web indexing framework. Starting from basic classifications for differential equations the proposed system architecture is amenable to extensions for further reconstruction of mathematical content on the Web. The syntactic analysis of mathematical formulae given in the considered formats must overcome ambiguities that stem from the fact that formula particles may have different encodings, which are in principle completely arbitrary. However, it turns out that the syntactic analysis can be done straightforward given some natural heuristic assumptions.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 11
    Publikationsdatum: 2014-02-26
    Beschreibung: A new method for noise removal of arbitrary surfaces meshes is presented which focuses on the preservation and sharpening of non-linear geometric features such as curved surface regions and feature lines. Our method uses a prescribed mean curvature flow (PMC) for simplicial surfaces which is based on three new contributions: 1. the definition and efficient calculation of a discrete shape operator and principal curvature properties on simplicial surfaces that is fully consistent with the well-known discrete mean curvature formula, 2. an anisotropic discrete mean curvature vector that combines the advantages of the mean curvature normal with the special anisotropic behaviour along feature lines of a surface, and 3. an anisotropic prescribed mean curvature flow which converges to surfaces with an estimated mean curvature distribution and with preserved non-linear features. Additionally, the PMC flow prevents boundary shrinkage at constrained and free boundary segments.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 12
    Publikationsdatum: 2019-01-29
    Beschreibung: A primal-dual interior point method for optimal control problems with PDE constraints is considered. The algorithm is directly applied to the infinite dimensional problem. Existence and convergence of the central path are analyzed. Numerical results from an inexact continuation method applied to a model problem are shown.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 13
    Publikationsdatum: 2014-02-26
    Beschreibung: Die in der Arbeitsgemeinschaft der Verbundsysteme zusammengeschlossenen deutschen Verbundsysteme kooperieren zur Realisierung eines die Länder und Verbundregionen übergreifenden offenen Netzwerkes einer offenen digitalen Bibliothek, dem Verteilten Dokumentenserver (VDS). Wesentliche Bestandteile des VDS sind die in den lokalen Bibliotheken und Verbundsystemen verteilten Dokumentenspeicher. Beim Aufbau des VDS verfolgen die deutschen Verbundsysteme für ihre digitalen Ressourcen, Zeitschriften und Dokumente, folgende Ziele [AGV03]: \begin{itemize} \item{Erhalt und dauerhafte Sicherung einmal erworbener Rechte} \item{Bessere Erschließung und Integration in das eigene Angebot} \item{Nahtlose Navigation in lokalen Zeitschriften- und Dokumentenservern und zwischen digitalen Artikeln und Zeitschriften, Dokumenten und Servern} \item{Dauerhafte Sicherung des Zugriffs und perspektivisch Langzeitverfügbarkeit} \end{itemize} Die Verbundsysteme streben an, die Speicherung, Erschließung und das Angebot ihrer digitalen Materialien in einer nationalen Kooperation durchzuführen. Sie entwickeln und betreiben zu diesem Zweck Portal- und Querschnittstechnologien zur Integration ihrer dezentral gespeicherten digitalen Ressourcen mittels Internet-Technologien.
    Schlagwort(e): ddc:000
    Sprache: Deutsch
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  • 14
    Publikationsdatum: 2014-02-26
    Beschreibung: In this paper, we present a novel approach to the congestion control and resource allocation problem of elastic and real-time traffic in telecommunication networks. With the concept of utility functions, where each source uses a utility function to evaluate the benefit from achieving a transmission rate, we interpret the resource allocation problem as a global optimization problem. The solution to this problem is characterized by a new fairness criterion, \e{utility proportional fairness}. We argue that it is an application level performance measure, i.e. the utility that should be shared fairly among users. As a result of our analysis, we obtain congestion control laws at links and sources that are globally stable and provide a utility proportional fair resource allocation in equilibrium. We show that a utility proportional fair resource allocation also ensures utility max-min fairness for all users sharing a single path in the network. As a special case of our framework, we incorporate utility max-min fairness for the entire network. To implement our approach, neither per-flow state at the routers nor explicit feedback beside ECN (Explicit Congestion Notification) from the routers to the end-systems is required.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 15
    Publikationsdatum: 2014-02-26
    Beschreibung: Wie findet man den optimalen Weg im U-Bahnnetz? Das Problem wird als Graph modelliert und dann eine Breitensuche durchgeführt. Will man Weglängen oder Fahrzeiten mitberücksichtigen, so braucht man den Algorithmus von Dijkstra für gewichtige Graphen. Beim Nachdenken über diese Algorithmen werden auch Fragestellungen der Graphentheorie berührt. In einem zweiten Abschnitt werden methodische Hinweise für den Unterricht in der Sekundarstufe I und II gegeben, insbesondere, wie man Lernende dazu bringen kann, ihre Ideen für Algorithmen präzise zu analysieren und zu Papier zu bringen.
    Schlagwort(e): ddc:000
    Sprache: Deutsch
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  • 16
    Publikationsdatum: 2014-02-26
    Beschreibung: The problem of clustering data can be formulated as a graph partitioning problem. Spectral methods for obtaining optimal solutions have reveceived a lot of attention recently. We describe Perron Cluster Cluster Analysis (PCCA) and, for the first time, establish a connection to spectral graph partitioning. We show that in our approach a clustering can be efficiently computed using a simple linear map of the eigenvector data. To deal with the prevalent problem of noisy and possibly overlapping data we introduce the min Chi indicator which helps in selecting the number of clusters and confirming the existence of a partition of the data. This gives a non-probabilistic alternative to statistical mixture-models. We close with showing favorable results on the analysis of gene expressi on data for two different cancer types.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 17
    Publikationsdatum: 2014-02-26
    Beschreibung: In this paper, we study the conflict-free assignment of wavelengths to lightpaths in an optical network with the opportunity to place wavelength converters. To benchmark heuristics for the problem, we develop integer programming formulations and study their properties. Moreover, we study the computational performance of the column generation algorithm for solving the linear relaxation of the most promising formulation. In many cases, a non-zero lower bound on the number of required converters is generated this way. For several instances, we in fact prove optimality since the lower bound equals the best known solution value.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 18
    Publikationsdatum: 2021-02-01
    Beschreibung: Operative planning in gas distribution networks leads to large-scale mixed-integer optimization problems involving a hyperbolic PDE defined on a graph. We consider the NLP obtained under prescribed combinatorial decisions---or as relaxation in a branch and bound framework, addressing in particular the KKT systems arising in primal-dual interior methods. We propose a custom solution algorithm using sparse local projections, based on the KKT systems' structual properties induced by the discretized gas flow equations in combination with the underlying network topology. The numerical efficiency and accuracy of the algorithm are investigated, and detailed computational comparisons with a control space method and with the multifrontal solver MA27 are provided.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 19
    Publikationsdatum: 2021-02-01
    Beschreibung: The topic of this paper is minimum cost operative planning of pressurized water supply networks over a finite horizon and under reliable demand forecast. Since this is a very hard problem, it is desirable to employ sophisticated mathematical algorithms, which in turn calls for carefully designed models with suitable properties. The paper develops a nonlinear mixed integer model and a nonlinear programming model with favorable properties for gradient-based optimization methods, based on smooth component models for the network elements. In combination with further nonlinear programming techniques (to be reported elsewhere), practically satisfactory near-optimum solutions even for large networks can be generated in acceptable time using standard optimization software on a PC workstation. Such an optimization system is in operation at Berliner Wasserbetriebe.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 20
    Publikationsdatum: 2014-02-26
    Beschreibung: Im Rahmen von Problemstellungen der kombinatorischen Optimierung können Schülerinnen und Schüler lernen, Algorithmen selber zu entwickeln. Gleichzeitig lernen sie dabei moderne Mathematik in ihren Anwendungen kennen und erleben die Mathematik als lebendige Wissenschaft.
    Schlagwort(e): ddc:000
    Sprache: Deutsch
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  • 21
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    Publikationsdatum: 2020-12-15
    Beschreibung: Morse matchings capture the essential structural information of discrete Morse functions. We show that computing optimal Morse matchings is NP-hard and give an integer programming formulation for the problem. Then we present polyhedral results for the corresponding polytope and report on computational results.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 22
    Publikationsdatum: 2014-02-26
    Beschreibung: In this paper, we study the minimum converter wavelength assignment problem in optical networks. To benchmark the quality of solutions obtained by heuristics, we derive an integer programming formula tion by generalizing the formulation of Mehrotra and Trick (1996) for the vertex coloring problem. To handle the exponential number of variables, we propose a column generation approach. Computational experiments show that the value of the linear relaxation states a good lower bound and can often prove optimality of the best solution generated heuristically.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 23
    Publikationsdatum: 2014-11-10
    Beschreibung: The parameter contraction degeneracy -- the maximum minimum degree over all minors of a graph -- is a treewidth lower bound and was first defined in (Bodlaender, Koster, Wolle, 2004). In experiments it was shown that this lower bound improves upon other treewidth lower bounds. In this note, we examine some relationships between the contraction degeneracy and connected components of a graph, block s of a graph and the genus of a graph. We also look at chordal graphs, and we study an upper bound on the contraction degeneracy and another lower bound for treewidth. A data structure that can be used for algorithms computing the degeneracy and similar parameters, is also described.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 24
    Publikationsdatum: 2014-11-10
    Beschreibung: The Maximum Cardinality Search algorithm visits the vertices of a graph in some order, such that at each step, an unvisited vertex that has the largest number of visited neighbors becomes visited. An MCS-ordering of a graph is an ordering of the vertices that can be generated by the Maximum Cardinality Search algorithm. The visited degree of a vertex $v$ in an MCS-ordering is the number of neighbors of $v$ that are before $v$ in the ordering. The visited degree of an MCS-ordering $\psi$ of $G$ is the maximum visited degree over all vertices $v$ in $\psi$. The maximum visited degree over all MCS-orderings of graph $G$ is called its {\em maximum visited degree}. Lucena (2003) showed that the treewidth of a graph $G$ is at least its maximum visited degree. We show that the maximum visited degree is of size $O(\log n)$ for planar graphs, and give examples of planar graphs $G$ with maximum visited degree $k$ with $O(k!)$ vertices, for all $k\in \Bbb{N}$. Given a graph $G$, it is NP-complete to determine if its maximum visited degree is at least $k$, for any fixed $k\geq 7$. Also, this problem does not have a polynomial time approximation algorithm with constant ratio, unless P=NP. Variants of the problem are also shown to be NP-complete. We also propose and experimentally analyses some heuristics for the problem. Several tiebreakers for the MCS algorithm are proposed and evaluated. We also give heuristics that give upper bounds on the value of the maximum visited degree of a graph, which appear to give results close to optimal on many graphs from real life applications.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 25
    Publikationsdatum: 2014-02-26
    Beschreibung: A new and time efficient model to evaluate the free energy of solvation has been developed. The solvation free energy is separated into an electrostatic term, a hydrogen bond term, and a rest-term, combining both entropic and van der Waals effects. The electrostatic contribution is evaluated with a simplified boundary element method using the partial charges of the MMFF94 force field. The number of hydrogen bonds and the solvent excluded surface area over the surface atoms are used in a linear model to estimate the non-electrostatic contribution. This model is applied to a set of 213 small and mostly organic molecules, yielding an rmsd of 0.87kcal/mol and a correlation with experimental data of r=0.951. The model is applied as a supplementary component of the free energy of binding to estimate binding constants of protein ligand complexes. The intermolecular interaction energy is evaluated by using the MMFF94 force field.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 26
    Publikationsdatum: 2020-03-06
    Beschreibung: In this paper we describe a new algorithm for multiple semi-flexible superpositioning of drug-sized molecules. The algorithm identifies structural similarities of two or more molecules. When comparing a set of molecules on the basis of their three-dimensional structures, one is faced with two main problems. (1) Molecular structures are not fixed but flexible, i.e., a molecule adopts different forms. To address this problem, we consider a set of conformers per molecule. As conformers we use representatives of conformational ensembles, generated by the program ZIBMol. (2) The degree of similarity may vary considerably among the molecules. This problem is addressed by searching for similar substructures present in arbitrary subsets of the given set of molecules. The algorithm requires to preselect a reference molecule. All molecules are compared to this reference molecule. For this pairwise comparison we use a two-step approach. Clique detection on the correspondence graph of the molecular structures is used to generate start transformations, which are then iteratively improved to compute large common substructures. The results of the pairwise comparisons are efficiently merged using binary matching trees. All common substructures that were found, whether they are common to all or only a few molecules, are ranked according to different criteria, such as number of molecules containing the substructure, size of substructure, and geometric fit. For evaluating the geometric fit, we extend a known scoring function by introducing weights which allow to favor potential pharmacophore points. Despite considering the full atomic information for identifying multiple structural similarities, our algorithm is quite fast. Thus it is well suited as an interactive tool for the exploration of structural similarities of drug-sized molecules.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 27
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    Unbekannt
    Publikationsdatum: 2014-02-26
    Beschreibung: Molecular dynamics simulations of possible ligands for proteins yield large amounts of data in the form of trajectories which are further processed in order to find metastable conformations. These conformations can then be used for docking between ligand and protein. Around this core computation procedure lots of other data have to be managed. It should also be possible for external users not involved in program development to perform computations. As a paradigm for other fields where a similar constitution of program usage and data processing is found we present a software architecture for data generation, access and management. Requirements for this system include: Ease of use, graphical user interface, persistent storage of data concerning molecules, users, programs, program parameters, metadata, and results. A mere storage in the file system would render a quick overview of data more or less impossible. On the other hand, storing large amounts of binary data in a database doesn't yield any advantage concerning speed of access. Therefore, a hybrid approach combining file system and database is appropriate. The system should be easily extensible by inserting new applications which can be controlled and whose results can be collected and stored. The software system described here consists of different components, the presentation layer (graphical user interface), the business logic, the persistence layer (relational database plus file system), and an interface to the compute cluster (batch system for parallel processing). We will discuss the alternatives and take a closer look at the components.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 28
    Publikationsdatum: 2020-03-09
    Beschreibung: We propose an approach for transforming the sampling of a molecular conformation distribution into an analytical model based on Hidden Markov Models. The model describes the sampled shape density as a mixture of multivariate unimodal densities. Thus, it delivers an interpretation of the sampled density as a set of typical shapes that appear with different probabilities and are characterized by their geometry, their variability and transition probabilities between the shapes. The gained model is used to identify atom groups of constant shape that are connected by metastable torsion angles. Based on this description an alignment for the original sampling is computed. As it takes into account the different shapes contained in the sampled set, this alignment allows to compute reasonable average shapes and meaningful shape density plots. Furthermore, it enables us to visualize typical conformations.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 29
    Publikationsdatum: 2020-02-11
    Beschreibung: We present publicly available data sets related to research on wireless networks. The scenarios contain a wide range of data and are detailed in all aspects. To our knowledge, this is the most realistic, comprehensive, and detailed \emph{public} data collection on mobile networking. We indicate example uses of this data collection in applications related tu UMTS.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 30
    Publikationsdatum: 2020-12-15
    Beschreibung: The \emph{line planning problem} is one of the fundamental problems in strategic planning of public and rail transport. It consists of finding lines and corresponding frequencies in a public transport network such that a given travel demand can be satisfied. There are (at least) two objectives. The transport company wishes to minimize its operating cost; the passengers request short travel times. We propose two new multi-commodity flow models for line planning. Their main features, in comparison to existing models, are that the passenger paths can be freely routed and that the lines are generated dynamically.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 31
    Publikationsdatum: 2014-02-26
    Beschreibung: The aim of this paper is to give a survey of the known results concerning centrally symmetric polytopes, spheres, and manifolds. We further enumerate nearly neighborly centrally symmetric spheres and centrally symmetric products of spheres with dihedral or cyclic symmetry on few vertices, and we present an infinite series of vertex-transitive nearly neighborly centrally symmetric 3-spheres.
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    Sprache: Englisch
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  • 32
    Publikationsdatum: 2019-05-10
    Beschreibung: We focus on the role of anisotropic elasticity in the simulation of the load distribution in a human mandible due to a lateral bite on the leftmost premolar. Based on experimental evidence, we adopt ``local''" orthotropy of the elastic properties of the bone tissue. Since the trajectories of anisotropic elasticity are not accessible from Computer Tomographic (CT) data, they will be reconstructed from (i) the organ's geometry and (ii) from coherent structures which can be recognized from the spatial distribution of the CT values. A sensitivity analysis comprising various 3D FE simulations reveals the relevance of elastic anisotropy for the load carrying behavior of a human mandible: Comparison of the load distributions in isotropic and anisotropic simulations indicates that anisotropy seems to ``spare''" the mandible from loading. Moreover, a maximum degree of anisotropy leads to kind of an load minimization of the mandible, expressed by a minimum of different norms of local strain, evaluated throughout the organ. Thus, we may suggest that anisotropy is not only relevant, but also in some sense ``optimal''.
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    Sprache: Englisch
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  • 33
    Publikationsdatum: 2019-05-10
    Beschreibung: The paper extends affine conjugate Newton methods from convex to nonconvex minimization, with particular emphasis on PDE problems originating from compressible hyperelasticity. Based on well-known schemes from finite dimensional nonlinear optimization, three different algorithmic variants are worked out in a function space setting, which permits an adaptive multilevel finite element implementation. These algorithms are tested on two well-known 3D test problems and a real-life example from surgical operation planning.
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  • 34
    Publikationsdatum: 2014-02-26
    Beschreibung: We present formulae for the corner points of the multidimensional Hausdorff and Dale Polytopes and show how these results can be used to improve linear programming models for computing e.\,g.\ moments of exit distribution of diffusion processes. Specifically, we compute the mean exit time of twodimensional Brownian motion from the unit square and the unit triangle, as well as higher moments of the exit time of time space Brownian motion from a triangle.
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    Sprache: Englisch
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  • 35
    facet.materialart.
    Unbekannt
    Publikationsdatum: 2014-11-10
    Beschreibung: Normal graphs are defined in terms of cross-intersecting set families: a graph is normal if it admits a clique cover $\cal Q$ and a stable set cover $\cal S$ s.t.~every clique in $\cal Q$ intersects every stable set in $\cal S$. Normal graphs can be considered as closure of perfect graphs by means of co-normal products (Körner 1973) and graph entropy (Czisz\'ar et al. 1990). Perfect graphs have been recently characterized as those graphs without odd holes and odd antiholes as induced subgraphs (Strong Perfect Graph Theorem, Chudnovsky et al. 2002). Körner and de Simone observed that $C_5$, $C_7$, and $\overline C_7$ are minimal not normal and conjectured, as generalization of the Strong Perfect Graph Theorem, that every $C_5$, $C_7$, $\overline C_7$- free graph is normal (Normal Graph Conjecture, Körner and de Simone 1999). We prove this conjecture for a first class of graphs that generalize both odd holes and odd antiholes, the circulants, by characterizing all the normal circulants.
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    Sprache: Englisch
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  • 36
    Publikationsdatum: 2014-02-26
    Beschreibung: It is known that the suspension of a simplicial complex can be realized with only one additional point. Suitable iterations of this construction generate highly symmetric simplicial complexes with a various interesting combinatorial and topological properties. In particular, infinitely many non-PL spheres as well as contactible simplicial complexes with a vertex-transitive group of automorphisms cab be contained in this way.
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    Sprache: Englisch
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  • 37
    Publikationsdatum: 2020-03-10
    Beschreibung: This paper presents an automatic approach for segmentation of the liver from computer tomography (CT) images based on a 3D statistical shape model. Segmentation of the liver is an important prerequisite in liver surgery planning. One of the major challenges in building a 3D shape model from a training set of segmented instances of an object is the determination of the correspondence between different surfaces. We propose to use a geometric approach that is based on minimizing the distortion of the correspondence mapping between two different surfaces. For the adaption of the shape model to the image data a profile model based on the grey value appearance of the liver and its surrounding tissues in contrast enhanced CT data was developed. The robustness of this method results from a previous nonlinear diffusion filtering of the image data. Special focus is turned to the quantitative evaluation of the segmentation process. Several different error measures are discussed and implemented in a study involving more than 30 livers.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 38
    Publikationsdatum: 2021-08-05
    Beschreibung: Mixed integer programs are commonly solved with linear programming based branch-and-bound algorithms. The success of the algorithm strongly depends on the strategy used to select the variable to branch on. We present a new generalization called {\sl reliability branching} of today's state-of-the-art {\sl strong branching} and {\sl pseudocost branching} strategies for linear programming based branch-and-bound algorithms. After reviewing commonly used branching strategies and performing extensive computational studies we compare different parameter settings and show the superiority of our proposed newstrategy.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 39
    Publikationsdatum: 2020-03-09
    Beschreibung: This article proposes a Lagrangean relaxation approach to solve integrated duty and vehicle scheduling problems arising in public transport. The approach is based on the proximal bundle method for the solution of concave decomposable functions, which is adapted for the approximate evaluation of the vehicle and duty scheduling components. The primal and dual information generated by the bundle method is used to guide a branch-and-bound type algorithm. Computational results for large-scale real-world integrated vehicle and duty scheduling problems with up to 1,500 timetabled trips are reported. Compared with the results of a classical sequential approach and with reference solutions, integrated scheduling offers remarkable potentials in savings and drivers' satisfaction.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 40
    Publikationsdatum: 2019-05-10
    Beschreibung: Structural mechanics simulation of bony organs is of general medical and biomechanical interest, because of the interdependence of the inner architecture of bone and its functional loading already stated by Wolff in 1892. This work is part of a detailed research project concerning the human mandible. By adaptive finite element techniques, stress/strain profiles occurring in the bony structure under biting were simulated. Estimates of the discretization errors, local grid refinement, and multilevel techniques guarantee the reliability and efficiency of the method. In general, our simulation requires a representation of the organ's geometry, an appropriate material description, and the load case due to teeth, muscle, or joint forces. In this paper, we want to focus on the influence of the masticatory system. Our goal is to capture the physiological situation as far as possible. By means of visualization techniques developed by the group, we are able to extract individual muscle fibres from computed tomography data. By a special algorithm, the fibres are expanded to fanlike (esp. for the musc. temporalis) coherent vector fields similar to the anatomical reality. The activity of the fibres can be adapted according to compartmentalisation of the muscles as measured by electromyological experiments. A refined sensitivity analysis proved remarkable impact of the presented approach on the simulation results.
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    Sprache: Englisch
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  • 41
    Publikationsdatum: 2021-02-01
    Beschreibung: Operative planning in gas networks with prescribed binary decisions yields large scale nonlinear programs defined on graphs. We study the structure of the KKT systems arising in interior methods and present a customized direct solution algorithm. Computational results indicate that the algorithm is suitable for optimization in small and medium-sized gas networks.
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    Sprache: Englisch
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  • 42
    Publikationsdatum: 2021-02-05
    Beschreibung: Der Kooperative Bibliotheksverbund Berlin-Brandenburg (KOBV) verzichtet auf eine einheitliche zentrale Verbunddatenbank zugunsten einer dezentralen, verteilten Struktur. In dieser Architektur erhält die Art der Indexierung der angesprochenen Online-Kataloge eine besondere Bedeutung. So werden sowohl Bibliotheksmitarbeiter als auch Bibliotheksbenutzer immer wieder mit der Recherche in fremden Katalogen konfrontiert, in denen unterschiedliche Indexierungsverfahren realisiert sein können. Ein abgestimmtes Indexierungskonzept verfolgt zwei grundsätzliche Ziele. Einerseits soll durch eine vereinheitlichte Indexierung die Qualität und Zuverlässigkeit der Rechercheergebnisse in der parallelen Suche in mehreren Katalogen über die KOBV-Suchmaschine erhöht werden. Gleichzeitig soll durch eine vereinheitlichte Indexierung die Akzeptanz von Suchen in entfernten Katalogen prinzipiell gesteigert und damit die Bedingungen für die gegenseitige Übernahme von Titeldaten erleichtert werden. Für die Indexierung muss zunächst die Art und der Umfang der im OPAC aufzubauenden Indices festgelegt werden. Aus Sicht des Nutzers entspricht diese Definition den möglichen Sucheinstiegen. Hat man dann entschieden, welche Indexterme aus welchen Feldern in die jeweiligen Indices einfließen sollen, muss bestimmt werden, nach welchen Regeln die Terme behandelt werden. Hier stellt sich insbesondere das Problem der Sonderzeichen wie Bindestriche, Apostrophe und Punkte oder Ziffern in Zeichenketten. Das vorliegende Konzept entstand in Zusammenarbeit der großen Universitätsbibliotheken in Berlin (der Freien Universität, der Humboldt-Universität, der Technischen Universität, der Universität der Künste) mit der KOBV-Verbundzentrale am ZIB.
    Schlagwort(e): ddc:000
    Sprache: Deutsch
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  • 43
    Publikationsdatum: 2014-02-26
    Beschreibung: We investigate a special class of quadratic Hamiltonians on $so(4)$ and $so(3,1)$ and describe Hamiltonians that have additional polynomial integrals. One of the main results is a new integrable case with an integral of sixth degree.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 44
    Publikationsdatum: 2020-11-16
    Beschreibung: We present a graph theoretical model for scheduling trains on a single unidirectional track between two stations. The set of departures of all possible train types at all possible (discrete) points of time is turned into an undirected graph $\Gneu$ by joining two nodes if the corresponding departures are in conflict. This graph $\Gneu$ has no odd antiholes and no $k$-holes for any integer $k\geq 5$. In particular, any finite, node induced subgraph of $\Gneu$ is perfect. For any integer $r\geq 2$ we construct minimal headways for $r$ train types so that the resulting graph $\Gneu$ has $2r$-antiholes and $4$-holes at the same time. Hence, $\Gneu$ is neither a chordal graph nor the complement of a chordal graph, in general. At the end we analyse the maximal cliques in $G$.
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    Sprache: Englisch
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  • 45
    Publikationsdatum: 2021-02-01
    Beschreibung: Unnecessarily conservative behavior of standard process control techniques can be avoided by stochastic programming models when the distribution of random disturbances is known. In an earlier study we have investigated such an approach for tank level constraints of a distillation process. Here we address techniques that have accelerated the numerical solution of the large and expensive stochastic programs by a factor of six, and then present a refined optimization model for the same application.
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    Sprache: Englisch
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  • 46
    Publikationsdatum: 2014-02-26
    Beschreibung: We investigate the impact of hop-limited routing paths on the total cost of a telecommunication network. For different survivability settings (dedicated protection, link and path restoration), the optimal network cost without restrictions on the admissible path set is compared to the results obtained with two strategies to impose hop limits on routing paths. In a thorough computational study on optimal solutions for nine real-world based problem instances, we show that hop limits should be avoided if the technology allows it and network cost is a major planning issue. In this case, column generation should be employed to deal with all routing paths. If hop-limits are required, these should be defined for each demand individually and as large as possible.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 47
    Publikationsdatum: 2020-11-13
    Beschreibung: Under high load, the automated dispatching of service vehicles for the German Automobile Association (ADAC) must reoptimize a dispatch for 100--150 vehicles and 400 requests in about ten seconds to near optimality. In the presence of service contractors, this can be achieved by the column generation algorithm ZIBDIP. In metropolitan areas, however, service contractors cannot be dispatched automatically because they may decline. The problem: a model without contractors yields larger optimality gaps within ten seconds. One way-out are simplified reoptimization models. These compute a short-term dispatch containing only some of the requests: unknown future requests will influence future service anyway. The simpler the models the better the gaps, but also the larger the model error. What is more significant: reoptimization gap or reoptimization model error? We answer this question in simulations on real-world ADAC data: only the new model ZIBDIP{\footnotesize dummy} can keep up with ZIBDIP.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 48
    Publikationsdatum: 2020-11-13
    Beschreibung: Edge contraction is shown to be a useful mechanism to improve lower bound heuristics for treewidth. A successful lower bound for treewidth is the degeneracy: the maximum over all subgraphs of the minimum degree. The degeneracy is polynomial time computable. We introduce the notion of contraction degeneracy: the maximum over all minors of the minimum degree. We show that the contraction degeneracy problem is NP-complete, even for bipartite graphs, but for fixed $k$, it is polynomial time decidable if a given graph $G$ has contraction degeneracy at least $k$. Heuristics for computing the contraction degeneracy are proposed and evaluated. It is shown that these can lead in practice to considerable improvements of the lower bound for treewidth, but can perform arbitrarily bad on some examples. A study is also made for the combination of contraction with Lucena's lower bound based on Maximum Cardinality Search (Lucena, 2003). Finally, heuristics for the treewidth are proposed and! evaluated that combine contraction with a treewidth lower bound technique by Clautiaux et al (2003).
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    Sprache: Englisch
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  • 49
    Publikationsdatum: 2020-11-13
    Beschreibung: \documentclass[12pt]{article} \usepackage{german} \parindent=0pt \begin{document} Der Kooperative Bibliotheksverbund Berlin-Brandenburg (KOBV) hat in den Jahren 2001 bis 2003 im Rahmen des Entwicklungsprojektes ''KOBV-Informationsportal`` ein regionales Portal aufgebaut, in dem integrierte Informationsdienste fr die regionalen Bibliotheken zur Verfügung gestellt werden. Das ''KOBV-Portal - Digitale Bibliothek Berlin-Brandenburg`` wurde im Dezember 2003 in Betrieb genommen. Das KOBV-Portal bietet in seiner ersten Ausbaustufe den Nachweis über die in den großen Bibliotheken lizenzierten Ressourcen und elektronischen Zeitschriften, zudem die nahtlose Navigation mittels des Reference-Linking-Werkzeuges SFX zu verschiedenen Diensten wie Fernleihe, Subito und freien Volltexten im Internet sowie zu frei zugänglichen elektronischen Zeitschriften. Realisiert wurden ferner die Remote-Authentifizierung, mit der sich ein Nutzer, der online eine Fernleih-Bestellung aufgeben möchte, über das Internet in seiner Heimatbibliothek authentifizieren kann. Des weiteren ist der Zugriff auf lizenzierte Bestände im Campus einer Hochschule mittels IP-Checking möglich. Als weiteren wesentlichen Bestandteil des KOBV-Portals hat die KOBV-Zentrale mit den Bibliotheken einen Workflow für ein Metadata-Sharing abgestimmt und für die Adaption und Normalisierung lokaler Metadaten aus lokalen Bibliothekssystemen und -Portalen den KOBV-Metadaten-Austausch-Parser (KMA-Parser) entwickelt. Damit Bibliotheken, deren Metadaten bislang lediglich in unstrukturierter Form vorliegen, strukturierte Metadaten anlegen, liefern und nachnutzen können, hat die KOBV-Zentrale das mit einer Web-Katalogisierungsschnittstelle ausgestattete ''Metadata-Tool`` entwickelt. Die für das Metadata-Sharing entwickelten Komponenten und Module sollen den Bibliotheken die Mehrfacherfassung ersparen und ihnen die Möglichkeit der wechselseitigen Nachnutzung der Metadaten eröffnen. Der vorliegende Projekt-Abschlussbericht gibt einen Überblick über die während der Projektlaufzeit realisierten Dienste des KOBV-Portals. \end{document}
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  • 50
    Publikationsdatum: 2014-02-26
    Beschreibung: Kürzeste Wege tauchen fast überall im Alltag auf. Daher eignet sich dieses Optimierungsproblem gut für den Unterricht. Modellierung und heuristische Vorgehensweisen werden geübt, um schließlich die klassischen kürzesten Wege-Algorithmen selbst zu erfinden. In diesem Artikel werden die Inhalte vorgestellt und konkrete Hinweise zum Unterricht in der Schule gegeben.
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    Sprache: Deutsch
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  • 51
    Publikationsdatum: 2019-01-29
    Beschreibung: A primal interior point method for control constrained optimal control problems with PDE constraints is considered. Pointwise elimination of the control leads to a homotopy in the remaining state and dual variables, which is addressed by a short step pathfollowing method. The algorithm is applied to the continuous, infinite dimensional problem, where discretization is performed only in the innermost loop when solving linear equations. The a priori elimination of the least regular control permits to obtain the required accuracy with comparable coarse meshes. Convergence of the method and discretization errors are studied, and the method is illustrated at two numerical examples.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 52
    Publikationsdatum: 2020-02-11
    Beschreibung: In this article, strategical infrastructure planning problems in the design of large-scale telecommunication networks are discussed based on experiences from three projects with industrial partners: The access network planning of the German Gigabit-Wissenschaftsnetz (G-WiN) for DFN (Verein zur Förderung eines Deutschen Forschungsnetzes e.V.), the mobile network switching center location planning project for E-Plus Mobilfunk, and the fixed network switching center location planning project for TELEKOM AUSTRIA. We introduce a mathematical model for a hierarchical multi-commodity capacitated facility location problem, present adaptions of this basic model to the specific requirements within the different projects and discuss the individual peculiarities and model decisions made. Eventually, we present and discuss computational results of three associated case studies, illustrating '"how we did the job`` with mathematical methods.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 53
    Publikationsdatum: 2014-11-10
    Beschreibung: Every lower bound for treewidth can be extended by taking the maximum of the lower bound over all subgraphs or minors. This extension is shown to be a very vital idea for improving treewidth lower bounds. In this paper, we investigate a total of nine graph parameters, providing lower bounds for treewidth. The parameters have in common that they all are the vertex-degree of some vertex in a subgra ph or minor of the input graph. We show relations between these graph parameters and study their computational complexity. To allow a practical comparison of the bounds, we developed heuristic algorithms for those parameters that are NP-hard to compute. Computational experiments show that combining the treewidth lower bounds with minors can considerably improve the lower bounds.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 54
    Publikationsdatum: 2019-01-29
    Beschreibung: The paper addresses primal interior point method for state constrained PDE optimal control problems. By a Lavrentiev regularization, the state constraint is transformed to a mixed control-state constraint with bounded Lagrange multiplier. Existence and convergence of the central path are established, and linear convergence of a short-step pathfollowing method is shown. The behaviour of the regularizations are demonstrated by numerical examples.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 55
    facet.materialart.
    Unbekannt
    Publikationsdatum: 2014-02-26
    Beschreibung: In [7,8,12] homogenization techniques are applied to derive an anisotropic variant of the bio-heat transfer equation as asymptotic result of boundary value problems providing a microscopic description for microvascular tissue. In view of a future application on treatment planning in hyperthermia, we investigate here the homogenization limit for a coupling model, which takes additionally into account the influence of convective heat transfer in medium size blood vessels. This leads to second order elliptic boundary value problems with nonlocal boundary conditions on parts of the boundary. Moreover, we present asymptotic estimates for first order correctors.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 56
    Publikationsdatum: 2014-02-26
    Beschreibung: Our main result is that every $n$-dimensional polytope can be described by at most $2n-1$ polynomial inequalities and, moreover, these polynomials can explicitly be constructed. For an $n$-dimensional pointed polyhedral cone we prove the bound $2n-2$ and for arbitrary polyhedra we get a constructible representation by $2n$ polynomial inequalities.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 57
    Publikationsdatum: 2023-10-05
    Beschreibung: Das KOBV-Metadaten-Schema ist von der KOBV-Zentrale entwickelt worden, um Ressourcen im Sinn von Informationskollektionen wie Datenbanken oder Fachportale zu beschreiben. Es ist ein wichtiger Bestandteil des KOBV-Portals, das die in der Region verf"ugbaren Ressourcen nachweist. Das KOBV-Metadaten-Schema dient den Bibliotheken zur Handreichung, um dem KOBV-Portal die Ressourcen mit den standardisierten und individuellen Angaben zu melden, so dass die Ressourcebeschreibungen einem austauschbaren Format entsprechen. Auf diese Weise k"onnen Ressourcebeschreibungen von anderen Bibliotheken mitgenutzt werden und ein Metadata-Sharing in der Region Berlin-Brandenburg praktiziert werden, um in diesem Bereich doppelte Arbeiten zu sparen.
    Schlagwort(e): ddc:000
    Sprache: Deutsch
    Materialart: reportzib , doc-type:preprint
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  • 58
    Digitale Medien
    Digitale Medien
    Springer
    Archives of gynecology and obstetrics 231 (1982), S. 177-184 
    ISSN: 1432-0711
    Schlagwort(e): Steroid receptor ; Ultrastructure ; Breast cancer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Receptor assay results were compared with the ultrastructure of 127 breast cancers (112 primary tumors, six recurrent lesions, nine metastases). Tumors were considered to be receptor positive if the receptor levels were ⩾ 15 fmol/mg of soluble tissue protein. Most breast cancer had heterogenous cells with different grades of ultrastructural differentiation. A prevalence of well-differentiated cancer cells and an abundance of intracytoplasmic vacuoles had a significant correlation with a positive estrogen receptor status. The correlation was better than between malignancy grades and receptor content. The type of breast cancer and the menopausal status bore no relation to receptor content. Progesterone receptors were found in well-differentiated tumors of low malignancy.
    Materialart: Digitale Medien
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  • 59
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular medicine 60 (1982), S. 213-227 
    ISSN: 1432-1440
    Schlagwort(e): Gastrointestinal hormones ; Gastrointestinal neoplasms ; APUD cells ; Cytology ; Ultrastructure ; gastrointestinale Hormone ; gastrointestinale Tumoren ; APUD-Zellen ; Zytologie ; Ultrastruktur
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Endokrine Zellen kommen im Verdauungsapparat in Form von Mikro-Organen (Langerhans'sche Inseln) und als „diffuses endokrines epitheliales Organ“ (Feyrter), das heißt als im Epithelverband der Magendarmschleimhaut gelegene Einzelezellen vor. Diese gastro-entero-pankreatischen (GEP-) endokrinen Zellen synthetisieren neben Serotonin zahlreiche Polypeptidhormone, die zum einen systemisch wirken (Kohlenhydrat-Stoffwechsel) und zum andern der Regulierung der Verdauungstätigkeit dienen. Die vorliegende Übersicht befaßt sich vornehmlich mit der Zytologie und Zytochemie der GEP-endokrinen Zellen. Die bis heute bekannten 19 endokrinen Zelltypen werden entsprechend ihrem Verteilungsmuster nach der neuesten Nomenklatur synoptisch zusammengestellt. Außerdem werden morphologischfunktionelle Aspekte der Biologie, Pathologie und Zytogenese dieser Zellen sowie ihre Stellung innerhalb übergeordneter Systeme (APUD-Zellen, Paraneurone) diskutiert.
    Notizen: Summary Endocrine cells occur in the digestive system as micro-organs (islets of Langerhans) or scattered throughout the epithelium of the gastrointestinal tract (“diffuse endocrine epithelial organ” of Feyrter). These gastro-entero-pancreatic (GEP) endocrine cells synthesize — in addition to serotonin — a great variety of polypeptide hormones, which regulate both carbohydrate metabolism and digestive processes. The present review deals mainly with cytology and cytochemistry of GEP endocrine cells. A synopsis is presented of the 19 endocrine cell types identified to date, which includes their update nomenclature and their anatomical distribution pattern. Morphological-functional aspects of cell biology, pathology, and cytogenesis of these cells and their position within superimposed systems (APUD cells, paraneurons) are discussed.
    Materialart: Digitale Medien
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  • 60
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 398 (1982), S. 75-86 
    ISSN: 1432-2307
    Schlagwort(e): Bone neoplasms ; Adamantinoma ; Ultrastructure ; Immunoenzyme ; Tibia/fibula ; Keratin ; Blood group antigens ; Factor VIII-related antigen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Adamantinoma of bone is a rare tumor, and fine structural analysis has been done in only a few cases. We report four cases studied by electron microscopy and immunohistochemical methods. Ultrastructural evaluation revealed a characteristic constellation of features, including intracellular bundles of type I microfilaments, moderate numbers of evenly dispersed mitochondria, scattered profiles of rough endoplasmic reticulum, occasional Golgi bodies and lysosomes, and scattered glycogen particles. Microvillous processes and desmosomes were identified in all tumors. Well-formed basement membranes enveloped cell clusters but did not surround individual cells. Intercellular basement membrane-like material also was found focally in pools. Ultrastructural features of endothelial differentiation, including Weibel-Palade bodies, micropinocytotic vesicles, and tight junctions, were not identified. Immunoperoxidase stains for coagulation factor VIII (von Willebrand factor) and blood group antigens were negative, whereas similar stains for keratin were positive. Our findings strongly suggest that adamantinoma is a neoplasm expressing definite epithelial, rather than endothelial, characteristics.
    Materialart: Digitale Medien
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  • 61
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 399 (1982), S. 49-59 
    ISSN: 1432-2307
    Schlagwort(e): Pituitary ; Pars tuberalis ; Gonadotrophs ; Squamous nests ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Forty autopsy pituitaries were studied to elucidate the histology, immunocytology and ultrastructure of pars tuberalis in subjects with normal and abnormal endocrine homeostasis. Pars tuberalis consisted mainly of gonadotrophs interspersed with few corticotrophs and thyrotrophs, histologically resembling those of pars distalis. Somatotrophs and lactotrophs were not identified. There were no histologic differences attributable to age or sex. In cases of glucocorticoid excess, pars tuberalis corticotrophs showed Crooke's hyalinization. Following castration or hypophysectomy, pars tuberalis gonadotrophs exhibited more intense immunostaining for FSH1 and LH than did normals. Ultrastructural analysis revealed gonadotrophs and corticotrophs showing no evidence of active secretion; immunoelectron microscopy demonstrated FSH, LH and ACTH in secretory granules. By light microscopy, squamous nests, often identified in pars tuberalis, were positive for immunoreactive keratin; cells at their periphery contained FSH, LH or ACTH, indicating derivation of nests by squamous metaplasia from gonadotrophs and corticotrophs. By electron microscopy, clusters of epithelial cells containing desmosomes and tonofilaments were surrounded by granulated gonadotrophs. Human pars tuberalis cells represent mainly a subpopulation of gonadotrophs possessing all organelles required for synthesis and storage of hormones but showing ultrastructural features of functional inactivity; the reasons for this inactivity and for the formation of squamous nests remain unexplained.
    Materialart: Digitale Medien
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  • 62
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 394 (1982), S. 195-205 
    ISSN: 1432-2307
    Schlagwort(e): Hurler syndrome ; Myocardium ; Histochemistry ; Ultrastructure ; Storage of gangliosides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Cardiac tissues obtained at post mortem examination of eight patients with the Hurler syndrome, who ranged in age from 5 to 23 years, were examined by histochemical methods and electron microscopy. Extensive myocardiocytic vacuolization and increased interstitial fibrous tissue were noted by light microscopy in all hearts. The cytoplasmic (perinuclear) vacuoles contained Luxol-fast-blue-positive substance. At the ultrastructural level, abnormal cytoplasmic organelles were present within the myocardiocytes in all patients. These organelles were of three types: zebra bodies (ZB), membranous cytoplasmic bodies (MCB) and granulomembranous bodies (GMB). As ZB and MCB are believed to represent the morphological counterpart of accumulated gangliosides, these substances rather than glycosaminoglycans appear to be stored within myocardiocytes of patients with the Hurler syndrome. The accumulation of gangliosides and the consequent damage to the myocardial substratum probably contributes to the clinically evident cardiac disease, so often observed in the patients with this disorder.
    Materialart: Digitale Medien
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  • 63
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 394 (1982), S. 255-267 
    ISSN: 1432-2307
    Schlagwort(e): Pituitary ; Adenoma ; TSH ; Ultrastructure ; Immunocytochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In a collection of 564 surgically removed pituitary adenomas, 4 cases were found to have had elevated TSH plasma levels. One of these tumors (case 1) could be classified as a highly differentiated mucoid TSH cell adenoma presenting histochemical reactions typical of, as well as electron microscopical features identical to, normal TSH cells. Immunoenzymatic studies failed to demonstrate TSH in the tumor cells. Two further adenomas (case 2 and 3) were similarly structured in many areas, but showed regions of poorer differentiation in which cells with distinct pleomorphism, irregular secretory granules, increased numbers of ribosomes and a well developed rough endoplasmic reticulum were present. In 10% of the tumor cells GH could be demonstrated immunoenzymatically, but there was no TSH. The fourth adenoma was an undifferentiated acidophilic adenoma showing pleomorphic cells having slight acidophil and partly mucoid granulations. The ultrastructure showed convoluted nuclei, increased numbers of free ribosomes as well as abundant rough endoplasmic reticulum and secretory granules which were different in size and number but distinctly of the TSH cell type. Immunoenzymatically, TSH was found in some cells, with GH in more cells. Endocrinologically, elevated levels of GH were measured in cases 2, 3 and 4 with LH being increased in case 1. Clinical and morphological correlations are discussed.
    Materialart: Digitale Medien
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  • 64
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 395 (1982), S. 169-179 
    ISSN: 1432-2307
    Schlagwort(e): Aneurysmal bone cyst ; Malignant transformation ; Osteosarcoma ; Irradiation ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Four cases of aneurysmal bone cyst, of which one became malignant 7 years after irradiation, were studied by electron microscopy. The aneurysmal bone cyst was composed of four different types of stromal cells — fibroblasts, myofibroblasts, osteoblasts, and histiocytes — and osteo-clastlike multinucleated giant cells. The surface of blood spaces was devoid of specialized endothelium, which may explain the presence of large quantities of extravasated erythrocytes. Some histiocytes contained siderosomes. The malignant lesion consisted of two main types of stromal cells, of which one had electron lucent and the other electron dense cytoplasm. The stromal cells produced osteoid and the tumour was regarded as an osteosarcoma. The multinucleated giant cells resembled those observed in aneurysmal bone cysts, but the nuclei seemed to be more often spherical. It is concluded that irradiation of the aneurysmal bone cyst may cause sarcomatous transformation in a cell capable of producing osteoid.
    Materialart: Digitale Medien
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  • 65
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 396 (1982), S. 127-140 
    ISSN: 1432-2307
    Schlagwort(e): Elastin ; Elastofibroma ; Histochemistry ; Soft tissue tumor ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Four cases of elastofibroma located in the subscapular region of 3 men aged 66, 74, and 83 years, and a woman 70 years old are reported. A correlated light and electron microscopic study including ultrastructural examination of Verhoeff's iron-hematoxylin (VIH)-stained sections was performed. Light microscopically, the elastofibromas were characterized by connective tissue built up by collagen fibers and sclerotic masses mingled with numerous fibers and globules of elastin material. In one micron thick Epon sections these elastin fibers often revealed a central axis surrounded by a mantle composed of periodic segments giving them a necklace-like appearance. The ultrastructural findings of these elastin structures, stained with VIH, and the appearance of the stroma cells and their relation to the elastin indicate that elastofibroma is a non-neoplastic reactive lesion in which elastin material is synthesized by the stromal cells and predominantly laid down around preexisting elastic fibers.
    Materialart: Digitale Medien
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  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 396 (1982), S. 197-211 
    ISSN: 1432-2307
    Schlagwort(e): Chondrosarcoma ; Mesenchymal ; Myxoid ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Five cases of conventional chondrosarcomas (CS.) of graded malignancy, 3 cases of myxoid CS. and 2 cases of mesenchymal CS. were studied by electron-microscopy. The chondrocyte like tumor cells of conventional CS. were characterized by: an ovoid shape, eccentric nucleus, abundant endoplasmic reticulum with dilated cisternae of RER; cytoplasmic glycogen, lipid droplets, and filaments plus numerous thin cytoplasmic projections. The histologically high grade tumors showed fewer cytoplasmic organelles, bizarre nuclei and more prominent nucleoli than the better differentiated ones. The tumor cells of myxoid CS. were chiefly fusiform. The cells frequently presented a pattern of rows with good cellular cohesion, and scanty cytoplasmic projections. The most prominent cytoplasmic feature was a conspicuous RER. Abundant cytoplasmic filaments and cytoplasmic glycogen were also observed. The undifferentiated areas of the mesenchymal CS. showed primitive mesenchymal cells with rounded nuclei, and scanty cytoplasm which was poor in organelles and glycogen. The cytoplasmic membranes were very cohesive and cytoplasmic projections were not present. Scanty cytoplasmic filaments and conspicuous desmosome like junctions were observed. The intercellular matrix of conventional and myxoid CS. consisted of fibrils, glycosaminoglycan granules and collagen fibers. In the undifferentiated zones of the mesenchymal CS. the intercellular matrix was very scanty and did not contain collagen fibrils. The more immature cells correspond to the small undifferentiated cells of mesenchymal chondrosarcoma.
    Materialart: Digitale Medien
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 396 (1982), S. 231-238 
    ISSN: 1432-2307
    Schlagwort(e): Mesothelioma ; Testis ; Ultrastructure ; Clear cell
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Ultrastructural features of a papillary mesothelioma arising in a hydrocele-sack are reported. The tumour cells presented numerous microvilli, desmosomes, basement membranes and abundant bundles of microfilaments, which all are hallmarks of mesotheliomas. The predominant cell type was the “clear epithelial cell”, but transitional cells and degenerative forms (foamy cells) were also found. The morphology and differential diagnosis of mesothelial tumours arising in the tunica vaginalis propria testis are discussed.
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  • 68
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 397 (1982), S. 109-119 
    ISSN: 1432-2307
    Schlagwort(e): Epithelioid sarcoma ; Ultrastructure ; 5′-nucleotidase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A case of epithelioid sarcoma was studied by electron microscopy and by light and electron microscopic enzyme histochemistry comparing with several control soft tissues. In addition to previously reported ultrastructural features, such as abundant 10 nm cytoplasmic filaments, desmosome-like cell junctions and small cystic spaces surrounded by filopodia or microvilli of the tumor cells, we encountered 10 nm cytoplasmic filaments showing electron dense condensation with a concentrically oriented or whorled pattern and a finger-print-like arrangement and 5′-nucleotidase activity of tumor cell membrane. Among the control soft tissues, 5′-nucleotidase activity was found only in synovial and endothelial cells. Both tumor and synovial cells showed no activity of adenosine triphosphatase, while marked activity of the enzyme was found in endothelial cells. These results support the concept that epithelioid sarcoma is derived from mesenchymal cells undergoing differentiation toward synovial cells during neoplastic transformation.
    Materialart: Digitale Medien
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  • 69
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 397 (1982), S. 131-147 
    ISSN: 1432-2307
    Schlagwort(e): Colonic neoplasm ; Microcirculation ; Ultrastructure ; Pathology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The ultrastructure of the microvasculature in human colorectal adenomas and carcinomas was studied, and compared with that of normal tissue. Blood vessels in adenomas were generally of normal structure, whereas carcinoma vessels displayed a variety of structural alterations. Endothelial proliferation was frequently observed in all the eleven carcinomas examined, which confirms the reports of new vessel formation in experimental malignant tumors. The presence of fenestrations in obviously abnormal endothelium was tentatively attributed to hypoxia, vascular regression or immaturity of the cells, in spite of the fact that normal capillaries in colonic mucosa are fenestrated. Some vessels showed multilayered basement membranes, various types of activated cells containing numerous lysosomal granules, and thickened perivascular tissue. These features may be a vascular response to repeated damage or a manifestation of vascular remodelling. Dilated thin-walled vessels, which were usually found at the periphery of carcinomas, were identified as venules. Small vessels located between the closely apposed carcinoma tubules were not obviously abnormal. They were nevertheless considered to be tumor-induced vessels which had undergone differentiation. The differences in vascular morphology between adenomas and carcinomas were considered to be due to their different growth patterns, growth rates and degrees of maturity.
    Materialart: Digitale Medien
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  • 70
    Digitale Medien
    Digitale Medien
    Springer
    Urological research 10 (1982), S. 123-130 
    ISSN: 1434-0879
    Schlagwort(e): Prostate ; Cadmium ; Ultrastructure ; Testosterone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The effects of cadmium and nickel chloride, administered in drinking water at 5 and 50 ppm, on the rat prostate are described. Zinc concentrations in the two lobes of the gland were unaffected by the metals and no consistent changes were observed at the subcellular level by X-ray microanalysis. The ultrastructural appearance of the prostate gland in rats of varying ages was unaltered following cadmium administration at those levels, while plasma testosterone concentrations did not differ significantly in cadmium treated animals. Low levels of cadmium (5 ppm) were accumulated by the ventral lobe of the prostate, although the metal was not detectable subcellularly. The results are discussed in relation to human prostatic carcinoma.
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  • 71
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 164 (1982), S. 343-347 
    ISSN: 1432-0568
    Schlagwort(e): Preimplantation embryos ; Ultrastructure ; Effect of Li+
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary We have recently shown that LiCl in the culture medium retards cleavage of mouse preimplantation embryos without delaying their blastulation and causes the formation of blastocysts with few large cells and a reduced or absent inner cell mass (Izquierdo and Becker 1982). In this study we compare the ultrastructure of major cellular organelles of Li+-treated and control embryos. No subcellular alterations were found that correlate with the altered morphology of the blastocysts. On the basis of these results we submit that the malformation of blastocysts developed in a Li+-containing medium is the morphogenetic consequence of a retardation of cleavage coupled with a normal timing in the establishment of zonular tight junctions around the peripheral cells of the morula.
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  • 72
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 164 (1982), S. 379-385 
    ISSN: 1432-0568
    Schlagwort(e): Muscle ; Growth and Development ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Scanning electron microscopy was used to study prenatal muscle development in mouse fetuses ranging from 12 days to 18 days gestation. Some transmission electron micrographs were also used for comparison. At 12 days no myofibres were evident although at 13 days long fibres surrounded by many mononucleated cells could be seen. At 14 days bundles of primary myofibres were observed with new myofibres forming in crevices between adjacent fibres. At 16 days the primary myofibres had separated but smaller secondary myofibres could be seen forming along their surfaces. The myofibres were very compact at 18 days and often appeared fused but this was due to the basal lamina ensheathing clusters of primary myofibres with their secondaries. The scanning electron micrographs appeared to illustrate the theories of muscle development which have arisen out of the various studies employing sectioning techniques.
    Materialart: Digitale Medien
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  • 73
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 165 (1982), S. 51-61 
    ISSN: 1432-0568
    Schlagwort(e): Anterior pituitary cells ; Mitosis ; Rat ; Immunohistochemistry ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Mitotic rates of the six types of immunohistochemically identifiable adenohypophysial cells were histometrically calculated in colchicine-pretrated male rats 5, 17, 30 and 70 days old. Sections were stained with the antisera against rLH, rFSH, rTSH, oGH, rPRL and pACTH1–39. The mitotic growth rate of the anterior pituitary gland at 30 days of age was much higher than at other times. Mitotic growth rates of GH and PRL cells increased with advancing age, while those of ACTH-, TSH- and immunonegative cells decreased with advancing age. LH/FSH cells showed no variation in mitotic growth rate with age. Mitotic cells can be classified into six cell types based on their fine structural properties: (1) agranular cells associated with the folliculo-stellate cells; (2) ambiguous cells with scanty minute secretory granules (50–150 nm in diameter); (3) basophils with a number of small secretory granules (130–200 nm); (4) immature acidophils whose large secretory granules (130–300 nm) are sporadically scattered; (5) acidophils with numerous spherical larger secretory granules (200–300 nm); and (6) prolactin cells with large polymorphic granules. At day 5 there was a high mitotic rate of the agranular and ambiguous cells [types (1) and (2)]; at day 70 a high mitotic rate was found in immature and mature acidophils [types (4) and (5)]. The mitotic rate of basophils (type 3) was high only at day 17 and low at all other times. The mitotic rate of prolactin cells (type 6) showed a slight increment with advancing age. It is concluded that the mitotic rates of the six cell types are age-dependent.
    Materialart: Digitale Medien
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  • 74
    ISSN: 1432-0568
    Schlagwort(e): Ultrastructure ; Sympathetic neurons ; Immobilization ; Perichromatin granules ; Nematosomes ; Concentric lamellar bodies
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Perichromatin granules, nematosomes (threadlike bodies), or concentric lamellar bodies were rarely observed in profiles of principal ganglionic neurons in the untreated rat superior cervical ganglion. They were more frequenlty encountered in these neurons following long-term activation of the sympathetic nervous system by intermittent immobilization (6 to 18 12-h periods). The increased number of the described nuclear and cytoplasmic structures following immobilization is documented by morphometric data and discussed in relation to specific chronic neuronal hyperactivity.
    Materialart: Digitale Medien
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  • 75
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 56 (1982), S. 194-200 
    ISSN: 1432-0533
    Schlagwort(e): Xeroderma pigmentosum ; de Sanctis-Cacchione syndrome ; Peripheral neuropathy ; Morphometry ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Histological, ultrastructural, and morphometric studies were performed on nerve and muscle biopsies from three patients with de Sanctis-Cacchione syndrome. Sural nerves showed marked loss of the myelinated fibers, in proportion to decrease in nerve conduction velocities and in inverse proportion to the severity of the clinical symptoms, which were related to the survival length. The larger fibers were involved earlier and more markedly than the smaller. The unmyelinated fibers were also decreased in number. Electron-microscopic studies showed the presence of primary degeneration of myelin sheaths or Schwann cells. Muscle biopsies showed grouping of type I and type II fibers in all three patients. Therefore, peripheral nerve involvement in de Sanctis-Cacchione syndrome was suggested to result from chronic degeneration of the neuronal cells and Schwann cells.
    Materialart: Digitale Medien
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  • 76
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 57 (1982), S. 1-6 
    ISSN: 1432-0533
    Schlagwort(e): Rat ; Malnutrition ; Protein deprivation ; Peripheral nervous system ; Ultrastructure ; Degeneration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In a previous study the occurrence of nerve fibre degeneration with a distribution as in dying-back neuropathies was described in young rats subjected to severe protein deprivation (Oldfors 1981). In this study the ultrastructural appearance of the degeneration of the nerve fibres at different levels of the longitudinal tail nerves in severely protein-deprived rats has been investigated. Various structural changes were noted, the most common being bands of Büngner indistinguishable from those seen in Wallerian degeneration. In nerve fibres which were less severely affected the most common finding was shrinkage of the axon with concomitant folding of the myelin sheath. Other structural changes included axonal accumulation of 10 nm filaments or mitochondria and other cell organelles, areas of demyelination, and projections of axolemma and Schwann cell membrane into the axon. Signs of axonal regeneration occurred but were infrequent. The degenerative changes seen at various levels of the nerves support the view that the neuropathy is of distal axonal type, but the structural appearance differs from several of the toxic dying-back neuropathies.
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  • 77
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 57 (1982), S. 51-58 
    ISSN: 1432-0533
    Schlagwort(e): Ependymoma ; Rat ; Ethylnitrosourea ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Tumors of the central nervous system (CNS) in Sprague-Dawley and Lewis rats were induced transplacentally by a single intraperitoneal (IP) injection of 10–25 mg/kg ethylnitrosourea (ENU) on days 16–20 of gestation. Light-microscopic examination revealed that 22% of these tumors could be diagnosed as ependymomas, anaplastic ependymomas (ependymoblastomas), or mixed tumors revealing both oligodendroglioma and anaplastic ependymoma tissues if the criteria of accepted classifications were followed. Electron-microscopic examination, however, demonstrated that the ependymoma and the anaplastic ependymoma-like tissue in ENU-induced tumors lacked ependymal features, such as basal bodies, cilia, complicated junctional complexes, microvilli, etc. This tissue type was repetitious, always being composed of cells arranged in groups, cords, and rosette-like (pseudorosette) formations. In the pseudorosettes, the cell nuclei were polarized at the periphery and the cytoplasm contained numerous polyribosomes, occasional short microtubules and usually a few small dense-core vesicles. The center of the pseudorosettes showed numerous slender interdigitating processes interconnected by maculae adherens. The tips of these processes showed vesicular degeneration. The cells arranged in groups or cords and perivascular rosettes revealed identical ultrastructure, but they were not polarized. The present findings indicate that the socalled ENU-induced ependymomas and anaplastic ependymomas are not true ependymal tumors, but rather primitive neuroepithelial neoplasms with some features of oligodendroglioma.
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  • 78
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 58 (1982), S. 39-47 
    ISSN: 1432-0533
    Schlagwort(e): BB-Wistar rat ; Diabetic distal symmetric neuropathy ; Axonal degeneration ; Teased fibers ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The distal, symmetric polyneuropathy of the spontaneously diabetic BB-Wistar rat was studied ultrastructurally and by means of teased fiber preparations. Ultrastructural findings consisted of malorientation of the axonal cytoskeleton, followed by axonal atrophy, secondary myelin breakdown and distal Wallerian degeneration. This sequence of structural changes could be confirmed by scoring of pathological abnormalities and morphometric evaluation of teased fibers. Distal sensory nerve fibers were affected earlier and more severely than motor fibers.
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  • 79
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 164 (1982), S. 303-313 
    ISSN: 1432-0568
    Schlagwort(e): Catecholamine ; Histofluorescence ; Ultrastructure ; Brain stem ; Chicken
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The nucleus tegmentalis dorsalis (NTD) which may be homologous with the mammalian locus coeruleus was investigated in the chicken by means of light, fluorescence and electron microscopy. Results are summarized as follows: 1) Numerous neurons emitting green fluorescence by the Falck-Hillarp method were observed in the NTD of the chicken. By consecutive light and fluorescence microscopy of the same section it was established that these catecholamine(CA)-containing neurons clearly coincided with the cell group named nucleus tegmentalis dorsalis by Jungherr (1945). This procedure further showed that there were also non-fluorescent neurons in the NTD. 2) On the basis of electron microscopic observation, two types of neurons were recognized in the NTD: medium-(15–25 μm) and small-sized (10–15 μm) neurons. Medium-sized neurons had a round to oval nucleus with several deep infoldings and abundant organelles. From combined fluorescence and electron microscopic examination, they obviously corresponded with CA-containing neurons demonstrated by the Falck-Hillarp method. Small-sized neurons had a round nucleus surrounded by pale cytoplasm. They corresponded with non-CA-containing neurons. 3) From morphometric analysis, it was clear that CA-containing neurons contained a well-developed rough-surfaced endoplasmic reticulum and many lysosome-like dense bodies, unlike non-CA-containing neurons. This study was undertaken as the basis of a research program to elucidate the catecholaminergic projections from the NTD.
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  • 80
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 165 (1982), S. 97-111 
    ISSN: 1432-0568
    Schlagwort(e): Cecum ; Guinea pig ; Anatomy ; Ultrastructure ; Bacteria (microvilli)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The anatomy of the cecum of the domesticated guinea pig (Cavia apera f. procellus) was investigated at the macroscopic and microscopic levels. In situ observations, injections of the blood vascular system and the preparation of dried specimens were made to elucidate the macroscopic anatomy of the cecum. The complex mesenterial situation in the abdomen was also investigated. The guinea-pig intestinal tract is particularized by the presence of the voluminous teniated cecum, which lacks an appendix vermiformis. The stomach is relative small and simple; the large intestine does not possess teniae. Seen with the scanning electron microscope the surface topography of the cecal wall shows a pattern of irregular mounds and crevasses. The former are made up of raised ridges, often in circular or looped profiles. Correlated light microscopic observation revealed an irregularity of the mucosal surface consisting of protrusions into the cecal lumen, the circular and looped configurations of the scanning microscope image representing the entry into crypts at the light-microscopic level. The close association of bacteria to the mucosal surface is striking. Observed with the transmission electron microscope this close association takes the form of an intermicrovillar location of the bacteria. The present observations are compared to those made on other rodents and with respect to the dietary habit of the guinea pig.
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  • 81
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 165 (1982), S. 329-344 
    ISSN: 1432-0568
    Schlagwort(e): Lateral reticular nucleus ; Ultrastructure ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A systematic study of the normal synaptic patterns within the lateral reticular nucleus (LRN) of the rat revealed various synaptic relationships. Two types of axon terminals were identified according to the morphology of the synaptic vesicles contained within them. Axon terminals with round vesicles established asymmetrical synaptic contacts with the somata and all areas of the dendritic trees including somatic and dendritic appendages. Pleomorphic-vesicle terminals established symmetrical synaptic contacts on somata and their appendages and on all sizes of dendrites and their appendages. Both round and pleomorphicvesicle terminals were infrequently seen to synapse upon the somata and proximal dendrites. The round-vesicle terminals outnumbered the pleomorphic-vesicle terminals on the dendritic trees. Terminals of the en passant type were also common throughout the LRN. Both round and pleomorphic-vesicle terminals were observed simultaneously contacting the soma and one or more dendritic profiles, or two different dendritic profiles. Synaptic configurations (glomeruli) were also observed in all three divisions of the nucleus. They consisted of a large, central, round-vesicle terminal contacting a number of small-calibre dendritic processes. This arrangement was surrounded by one or more sheets of glial lamellae. Puncta adherentia were observed on the apposed membranes of adjacent cells, adjacent dendrites and adjacent axon terminals.
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  • 82
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 165 (1982), S. 425-435 
    ISSN: 1432-0568
    Schlagwort(e): Sertoli cells ; Development ; Ultrastructure ; Prenatal irradiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Is the presence of germinal cells necessary for the Sertoli cells to acquire normal features? To respond to this question we have studied the development of the Sertoli cells in rats irradiated at the end of the foetal life. In the prenatal irradiated rats, the lumen of the seminiferous tubules appears later than in the control rats. The Sertoli cells show numerous flexuous apical processes, with central microtubule bundles. These processes regress progressively after the 40th day of life when the tubular lumen appears; numerous junctional complexes differentiate with the same structure as those of control animals. There are important dilatations of the intercellular spaces. The cytoplasmic organelles show a normal development up to the 40th day of life. After this period, the rough endoplasmic reticulum and the Golgi apparatus clearly regress while important dilatations appear in the smooth endoplasmic reticulum and persist in the adult animal. From the 35th day on, the basal lamina of the seminiferous tubules is irregular and multilayered. The differentiation of the Sertoli cells seems to be independent of the presence of germinal cells until the 40th day of life and presents several particularities; thereafter the Sertoli cells show signs of regression.
    Materialart: Digitale Medien
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  • 83
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 56 (1982), S. 245-249 
    ISSN: 1432-0533
    Schlagwort(e): Pituitary adenoma ; Cell culture ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A pituitary adenoma from an acromegalic female patient has been studied in cell cultures. Two populations of parenchymal cells, i.e., elongated shapes and big pale forms with irregular outlines, were distinguished light-microscopically. Ultrastructurally, three types of cells were found. Two of them contained secretory granules in varying numbers and sizes. Based on the proportion of the various cellular elements these cells were considered as counterparts of the elongated shapes being responsible for the GH secretion at different rates. The third cell type with very few secretory granules was identified with the big pale forms. Presumably, they could be exhausted GH-secreting cells. Besides fine structural characterisation, cultured cells of endocrinologically active human pituitary adenomas offer suitable models for studying some phases of exocytosis and membrane retrieval.
    Materialart: Digitale Medien
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  • 84
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 56 (1982), S. 307-310 
    ISSN: 1432-0533
    Schlagwort(e): Primary rhabdomyosarcoma ; Brain tumor ; Ultrastructure ; Basal ganglia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Primary intracranial rhabdomyosarcoma is extremely rare. A case of primary rhabdomyosarcoma in the left basal ganglia is described in a 2-year-old boy. The investigations revealed no primary lesion elsewhere except in the brain. At the electron-microscopic level, the majority of the cells contained specific microfilamentous bundles, which were either distributed at random or organized in myofibrils identified by their cross striations with primitive Z band formation.
    Materialart: Digitale Medien
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  • 85
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 58 (1982), S. 87-94 
    ISSN: 1432-0533
    Schlagwort(e): Hypercapnia ; Rat brain ; Ultrastructure ; Cerebral edema
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary It is presently debated how much cellular acidosis contributes to brain cell damage during ischemia and hypoxia. To study the influence of acidosis occurring in the absence of energy failure, extreme hypercapnia was produced in anesthetized, artificially ventilated, and well oxygenated rats by increasing the inspired CO2 concentration until arterialPCO2 reached 150 or 300 mm Hg. At these CO2 tensions intracellular pH falls from a control value of about 7.05 to about 6.85 and 6.65, respectively. After 45 min the brains were fixed in perfusion and processed for light and electron microscopy. AtPaCO2 150 mm Hg no clear neuronal abnormality was detected, but atPaCO2 300 mm Hg some neuronal changes were observed. Notably, the nuclei showed slightly coarser chromatin than normally. In a few nerve cells mild swelling of mitochondria and dispersion of polysomes as well as detachment of ribosomes from the endoplasmic reticulum appeared. In both groups, slight to moderate astrocytic edema developed. Thus, even extreme hypercapnia, with its acompanying marked tissue acidosis, alters ultrastructure in the brain only to such a moderate extent that irreversible cell damage is unlikely. We conclude, therefore, that acidosis occurring during ischemia or hypoxia is detrimental only if pH is further lowered and/or if it occurs in conjunction with cerebral energy failure.
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  • 86
    Digitale Medien
    Digitale Medien
    Springer
    Archives of dermatological research 273 (1982), S. 307-318 
    ISSN: 1432-069X
    Schlagwort(e): Morphometry ; Oral mucosa ; Keratinocytes ; Cell and nuclear volume ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The aim of this investigation was to determine whether volumetric changes occurred in differentiating layers of stratified squamous epithelium. Samples of cheek pouch mucosa from 5 hamsters were obtained, prepared for electron microscopy using carefully controlled methods, and electron micrographs obtained from defined basal, spinous and granular layers of the epithelium. Stereological point counting procedures were used to determine the ratio of nucleus to cytoplasm for each of the defined cell layers. From direct measurement of nuclear profiles, major and minor axes were transformed to diameters of circles of equivalent area and it was thus possible to obtain an estimate of nuclear volume. Using the previously determined nuclear-cytoplasmic ratios the volume of cytoplasm and hence cell volume, could be estimated for the cell layers. Between basal and granular layers, nuclear-cytoplasmic ratios decreased from 0.42 to 0.08, whereas cytoplasmic and cellular volumes increased progressively from 248 to 1052 μm3 and from 352 to 1144 μm3, respectively. Nuclear axial ratios were highest in the granular layers. These methods can be used in a variety of comparative ultrastructural studies of epithelia, and will also prove valuable in generating additional biological information from more conventionally presented stereological data.
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  • 87
    Digitale Medien
    Digitale Medien
    Springer
    Surgical and radiologic anatomy 4 (1982), S. 197-204 
    ISSN: 1279-8517
    Schlagwort(e): Finite element method ; Engineering ; Mandible ; Stress ; Honeycomb
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Résumé Nous avons, dans le précédent travail, attiré l'attention sur le fait que l'application des méthodes modernes utilisées en engineering pour la création et la vérification des structures mécaniques complexes à la recherche en anatomie semblait d'avérer une voie de recherche nouvelle et fructueuse, précisant bien que cette méthodologie n'était appliquable qu'à certains types de recherche bien définis et que son domaine de choix était l'ostéologie fonctionnelle. Nous avons donc procédé à une ≪modélisation≫ de la mandibule et à une expérimentation sur le modèle ainsi obtenu à l'aide de la ≪méthode des éléments finis≫ parce que l'étude de celle-ci nous semblait un moyen commode de tester notre méthodologie et sa fiabilité (la traumatologie de la mandibule est en effet bien connue), mais aussi et surtout parce que les conceptions généralement admises, relatives à la structure de la mandibule, ne nous semblaient pas pleinement satisfaisantes eu égard aux progrès actuels des connaissances en résistance des matériaux.
    Notizen: Summary In a previous article we drew attention to the application of modern methods used in engineering to the development and verification of complex mechanical structures in anatomical research. This approach was new and appeared to be fruitful, showing clearly that this technique was only applicable to certain types of well-defined research, in particular functional osteology. We therefore developed a model of the mandible and performed a series of experiments using the concepts of finite structures which provided a convenient means of testing our approach and its validity. More particularly, however, there are a number of widely held ideas regarding the structure of the mandible which strike us as not altogether consistent with current developments in the knowledge of resistance in materials.
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  • 88
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 34 (1982), S. 273-279 
    ISSN: 1432-0827
    Schlagwort(e): Odontogenesis ; Ultrastructure ; Alkaline phosphatase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The ultrastructural localization and gradient of activity of alkaline phosphatase were studied with respect to cell differentiation, matrix synthesis, and matrix mineralization in the incisor and molar teeth of 4-day-old Sprague-Dawley rats. The animals were perfused intracardially at room temperature with 2.5% glutaraldehyde in 0.1M sodium cacodylate (pH 7.4) with 3–4% sucrose. The jaws were dissected, immersion-fixed for 24 h, and the incisor and molar tooth germs removed. These were demineralized in 10% EDTA in NaOH (pH 7.4) with 7% sucrose. After reactivation of the enzyme with 0.1M MgCl in Tris-maleate buffer (pH 7.4) at 4°C, the teeth were incubated for alkaline phosphatase in a medium consisting of 6 ml 3% sodiumβ-glycerophosphate, 4 ml 0.2M Tris-HCl buffer (pH 9.2), 3 ml 1.6% MgSO4, 12 ml 0.5% lead citrate (pH⋍12), and 2.1 g sucrose. The pH was adjusted to 9.2 with 0.2M HCl, the volume made up to 30 ml, and the solution centrifuged for 10 min at 5000 rpm. Control teeth were incubated in medium minus the substrate. Finally, the specimens were routinely post-fixed and embedded for sectioning and examination with a Philips 300 electron microscope. A gradient of alkaline phosphatase activity was mapped along the developing teeth in the cells of the stratum intermedium, the proximal borders of the ameloblasts, the early dentine matrix, the predentine-dentine border, matrix vesicles, and the plasma membranes of odontoblasts and subodontoblast cells. The gradient of alkaline phosphatase activity was evident in the forming tooth from the cervical loop to the crown apex and was related to the cellular events, matrix synthesis, and matrix mineralization occurring during odontogenesis.
    Materialart: Digitale Medien
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  • 89
    ISSN: 1432-0827
    Schlagwort(e): Bacterial amphophile ; Purification ; Chemistry ; Resorption ; Ca influx ; Cyclic AMP
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The bone resorptive factor and amphipathic antigen (AcA) previously identified by us in preparations fromActinomyces viscosus have been partially purified, characterized chemically, and compared. They elute at the same location on chromatography with Ac 22. The fatty acid composition of AcA and the bone resorptive factor is the same. Some differences in carbohydrate composition are observed. TheActinomyces factor does not affect calcium influx or cyclic AMP in isolated bone cells. Therefore it is concluded that AcA stimulates resorption either by gaining entrance into bone cells or by way of a yet undetermined second messenger.
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  • 90
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 34 (1982), S. 382-390 
    ISSN: 1432-0827
    Schlagwort(e): Avian osteopetrosis ; Avian oncornavirus ; Ultrastructure ; Calcification ; Bone cells
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Diaphyseal tibial bone of 12.5 – 13-day and 19-day-old embryos and 20-day-old hatched chicks infected with retrovirus MAV.2-O were examined by transmission electron microscopy. The viruses were associated with lining osteoblasts and osteocytes. Whereas the infection of the osteoblast layer seemed to be a transient stage, virus association with osteocytes was a constant and main ultrastructural feature. The viruses were found either in the osteoid or in the periosteocytic space of the bone lacunae. They arose from dense cytoplasmic areas located near the cell plasmalemma via a budding process. The newly budded virus particles often had a large tail or a fine stalk-like process lost in the extracellular space. The viruses underwent calcification by deposition of inorganic material and were incorporated in the bone trabeculae. No production of virus was observed in typical osteoclasts with well-differentiated ruffled borders. The viral-induced avian osteopetrosis seemed to result from increased bone deposition through stimulation of osteoblast and osteocyte activities, whereas osteoclastic bone resorption seemed to be undisturbed.
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  • 91
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 48 (1982), S. 137-143 
    ISSN: 1432-1106
    Schlagwort(e): GABA uptake ; Radioautography ; Ultrastructure ; Oculomotor nucleus ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The uptake of tritiated γ-aminobutyric acid (3H-GABA) in the oculomotor nucleus of the cat was studied, using light and electron microscopic examination of radioautograms after intracerebral in vivo administration of the amino-acid. A glial uptake by oligodendrocytes was seen together with a neuronal uptake of the tracer in a certain type of axon terminals found in synaptic contact with both dendrites and soma, some of them exhibiting all the ultrastructural features of motoneurons. Previous neurochemical, electrophysiological and immunocytochemical studies indicate that GABA might well be the inhibitory neurotransmitter in the vestibuloocular reflex arc. The present results show that a morphological substrate exists for the presumed postsynaptic GABAergic inhibition of ocular motoneurons, at least in the oculomotor nucleus of the cat.
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  • 92
    Digitale Medien
    Digitale Medien
    Springer
    Archives of toxicology 51 (1982), S. 79-89 
    ISSN: 1432-0738
    Schlagwort(e): Trialkylphosphorothioates ; Rat ; Lung ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Various trialkylphosphorothioates occur as impurities in many organophosphorus pesticides. In addition to the immediate, cholinergic symptoms usually associated with the toxicity of organophosphorus compounds an oral LD50 dose of O,S,S-trimethyl phosphorodithioate or O,O,S-triethyl phosphorothioate to rats, resulted in the delayed development of lung lesions and often death within 4 days. This study attributes the late crisis to impaired lung function resulting from massive alveolar oedema and cellular responses to the selective destruction of type I pneumocytes. Proliferation of type II pneumocytes produced an epithelium of very large cells which resulted in a thick blood/alveolus barrier and also occluded much of the alveolar lumen. Debris from the type I pneumocytes was liberated into the alveolar lumen resulting in leukocytic infiltration of the interstitial tissue and an increase in the number of alveolar macrophages. The lung morphology of animals surviving the crisis period returned to normal within a further 4 days with the transformation of many hypertrophic type II pneumocytes into type I alveolar lining cells.
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  • 93
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 133 (1982), S. 11-19 
    ISSN: 1432-072X
    Schlagwort(e): Cyanobacteria ; Ultrastructure ; Mastigocladus laminosus ; Fischerella ; True branching
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The morphology and ultrastructure of the thermophilic cyanobacteriumMastigocladus laminosus were examined by scanning and transmission electron microscopy. Mature cultures consisted of relatively old, wide filaments that branched frequently to form younger, thinner filaments. The cells of the younger filaments had a consistently cylindrical morphology, while those of older filaments were rounded and pleomorphic. The internal ultrastructure of the cells depended somewhat on their age. As young cells became larger and wider, their thylakoids underwent slight rearrangement and spread out toward the center of the cytoplasm. Polyphosphate bodies, carboxysomes (polyhedral bodies), and lipid-body-like structures increased in number as the cells aged, but ribosomes and cyanophycin granules were depleted. Cell division involved septum formation followed by ingrowth of the outer membrane and sheath. Cells in older filaments were separated from each other by a complete layer of sheath material. Septum formation in older cells was also seen to occur parallel to the long axis of the filament, thereby confirming that true branching took place.
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  • 94
    Digitale Medien
    Digitale Medien
    Springer
    European archives of psychiatry and clinical neuroscience 232 (1982), S. 407-426 
    ISSN: 1433-8491
    Schlagwort(e): Fetal neurolipidosis ; Ultrastructure ; Prenatal diagnosis ; Fetale Neurolipidose ; Ultrastruktur ; Pränatale Diagnose
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Nach positiver enzymatischer Pränataldiagnose aus der Amnionzellkultur lieferte die morphologische Untersuchung von 10 Feten (19.–25. Schwangerschaftswoche) mit sechs verschiedenen Neurolipidosen (Sphingolipid-Speicherkrankheiten) bei 9 Feten ein positives Ergebnis, wobei der nicht immer optimale Erhaltungszustand der fetalen Gewebe nach therapeutischer Abruptio in Kauf genommen werden mußte. Die Ultrastruktur der quantitativ meist noch geringen Lipidspeicherprozesse in Gehirn oder viszeralen Organen glich qualitativ jener der postnatalen Speicherprozesse: GM2-Gangliosidose Type 2; Nachweis von „menbranous cytoplasmic bodies“ lysosomalen Ursprungs in Fortsätzen von Nervenzellen des Groß-hirns. Morbus Krabbe; Auftreten von einkernigen und mehrkernigen Speicherzellen, z. T. mit Gefäßbeziehung, im Rückenmark. In den Speicherzellen traf man auf spieß- oder lamellenförmige, teils auch fädig strukturierte Einschlußkörper. GM1-Gangliosidose Typ 1; in Nervenzellen des Hirnstamms Vorkommen intrazytoplasmatischer lysosomaler Speicherkörper vom „Zebra“-Typ, in der Milz fanden sich durch zahlreiche, kaum strukturierte Vakuolen geblähte Speicherzellen. Metachromatische Leukodystrophie; im Gegensatz zu Literatur-Befunden waren keine Speicherprozesse im fetalen Hirn und Rückenmark, jedoch starke Speicherungen in den Nierentubuli in Form multilamellärer (zirkulär, parallel oder unregelmäßig geschichteter) Speicherkörper, teils mit Prävalenz in den Zellen mit Mikrovilli, nachweisbar. Fluoreszenzmikroskopisch war metachromatisches Material in Nierentubuli und Sammelrohren, ferner auch in der Leber (Grenze der Glissonschen Dreiecke zum Parenchym) darstellbar. Morbus Niemann-Pick Typ C; große Nervenzellen des Rückenmarks und der Stammganglien enthielten zahlreiche Myelinfiguren-artige Einschlußkörper, die den postnatalen lysosomalen Speicherkörpern in Nervenzellen bei dieser Erkrankung ähneln. Morbus Gaucher; der erst 19 Wochen alte Fet zeigte trotz biochemisch eindeutigen Defekts der Glucocerebrosidase-Aktivität noch keine Speicherphänomene. Die bereits pränatal oft deutliche morphologische Manifestation der Speicherprozesse bei Neurolipidosen zeigt, daß die postnatale Latenz der klinischen Erscheinungen während mehrerer Monate (bisweilen 1–2 Jahre) einem hohen Grad an zellulärer Kompensationsfähigkeit entspricht.
    Notizen: Summary After positive prenatal enzymic diagnosis of different neurolipidoses therapeutic abortion was carried out in the 19th to 25th week of pregnancy. Ten delivered fetuses were studied ultrastructurally and in nine of them positive results were obtained, although in some cases one had to accept relatively poor structural conservation of fetal tissues. The ultrastructure of the quantitatively small lipid storage effects qualitatively resembled that of the postnatal stages with some exceptions of localization. In fetal GM2-gangliosidosis type 2 (variant 0) concentric menbranous cytoplasmic bodies were detected in the brain cortex. In Krabbe's disease the myelinated regions of the spinal cord showed scattered storage (globoid) cells, sometimes closely related to blood vessels, which contained isolated or stranded tubular or spicular inclusions. In GM1-gangliosidosis type 1 neurons of the brain stem showed lamellar inclusions structured as zebra bodies, and splenic histiocytes exhibited numerous almost clear cytoplasmic vacuoles. In fetal metachromatic leukodystrophy the CNS including myelinated regions was essentially free of morphologic lipid storage effects. However, many kidney tubules cells contained great numbers of irregular or roughly parallel stacks of membranes. These inclusions may be equivalent to “tuffstone” bodies. In one fetus the bodies were restricted to tubular cells bearing microvilli. Fluorescent microscopy of arcus of the kidney tubule showed excess amounts of metachromatic material. Less of this material was demonstrable in the envelope layer of hepatic Glisson triangles. In the fetus with Niemann-Pick disease type C large neurons of the basal ganglia and the spinal cord were filled with membranous inclusions that were similar to myelin-shaped bodies rather than to solid membranous bodies. The 19-weeks-old fetus with enzymically proven Gaucher disease was free of ultrastructural lipid storage effects. Most but not all of the morphological findings in the fetuses with neurolipidoses were in accordance with published results.
    Materialart: Digitale Medien
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  • 95
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 398 (1982), S. 101-108 
    ISSN: 1432-2307
    Schlagwort(e): Rhabdoid tumor ; Histology ; Ultrastructure ; Prognosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Clinical and histopathological features of two cases of malignant rhabdoid tumor of the kidney are presented. One of these cases was also studied by electron microscopy. Histologically, both tumors consisted of an admixture of undifferentiated polygonal or elongated cells and cells with abundant eosinophilic cytoplasm frequently containing hyaline globular structures. Ultrastructurally, these cytoplasmic inclusions were composed of large masses of actin-size and intermediate-size filaments. The poor prognosis of this type of tumor is emphasized and histological criteria for differential diagnosis from other malignant renal tumors of childhood and adolescence are discussed.
    Materialart: Digitale Medien
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  • 96
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 113 (1982), S. 144-149 
    ISSN: 1615-6102
    Schlagwort(e): Anemia phyllitidis ; Chloroplast ; Gametophyte ; Metronidazole ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Metronidazole inhibits cell division in gametophytes of the fernAnemia phyllitidis without changing morphogenetic patterns. Simultaneously the sensitivity of the prothallia against gibberellins which substitute for the natural sexual pheromone “antheridiogen A”, is increased. The inhibition of cell division is accompanied by a loss of chlorophyll and by severe changes in the ultra-structure of the chloroplasts.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 97
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 113 (1982), S. 189-192 
    ISSN: 1615-6102
    Schlagwort(e): Brassica napus ; Membrane ; Nucleolus ; Nucleus ; Ultrastructure ; Vacuole
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Vacuole-like structures were found in the nuclei of root tip cells ofBrassica napus. The cells containing the unusual nuclear inclusions were found to be adjacent to zones of degenerating cells. Such groups of cells occurred irregularly in the meristematic regions of the young root tips. The possibility that they represent changes which have occurred in old seeds is discussed. The “vacuole-like” structures seen in the cells adjacent to the degenerating zones were bounded by a membranous layer 12 nm thick. This is thicker than most cellular membranes. The “vacuoles” frequently contained inclusions and showed similarities to protein bodies reported elsewhere. The structures are thought to represent rearrangements of cell products which may have accumulated through an imbalance of metabolism in consequence of the imminent cell degeneration.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 98
    ISSN: 1615-6102
    Schlagwort(e): Aspergillus nidulans ; Aspergillus giganteus ; Hyphal apex ; Ultrastructure ; Woronin body
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The hyphal tip ultrastructure ofAspergillus nidulans andAspergillus giganteus indicates that their apical organization is very similar to that found in other filamentous fungi. Both species have an area immediately behind the hyphal apex free of all large organelles and containing a high concentration of vesicles. InA. giganteus only one size class of vesicle is clearly evident, with a mean diameter of 72 nm. InA. nidulans two size classes of vesicle were found, with mean diameters of 75 nm and 31 nm. A Spitzenkörper is evident inA. nidulans as an area very close to the tip containing only the smaller vesicles. InA. giganteus one or more apparently mature Woronin bodies were found within the first 1 μm of some hyphal apices. The possible significance of their presence is discussed.
    Materialart: Digitale Medien
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  • 99
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 110 (1982), S. 23-33 
    ISSN: 1615-6102
    Schlagwort(e): Meiosis ; Microtubules ; Polarity ; Ultrastructure ; Mosses
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary An extensive system of microtubules develops during meiotic prophase in the mossRhynchostegium serrulatum (Hedw.)Jaeg. &Sauerb. Development of the cytoskeleton can be traced to early prophase when the nucleus is acentric and the single plastid divides into four plastids. The cytoskeletal microtubules are associated with equidistant positioning of the four plastids at the distal tetrad poles and with migration of the nucleus to a central position in the sporocyte. The cytoskeleton, which interconnects plastids and encloses the nucleus, contributes to the establishment of moss sporocyte polarity. Just prior to metaphase I evidence of the prophase cytoskeleton is lost as the bipolar metaphase I spindle develops in association with discrete polar organizers located in opposite cleavage furrows between plastids.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 113 (1982), S. 10-22 
    ISSN: 1615-6102
    Schlagwort(e): Diatom ; Motility ; Mucopolysaccharide ; Secretion ; Staining ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Generation of movement in benthic diatoms is thought to be intimately associated with secretion at the raphe, a slit in the silica cell wall. The presence and distribution of extracellular substances and their source was investigated cytochemically by transmission electron microscopy. Extracellular material, possibly-acid mucopolysaccharide, was observed consistently within the entire length of the raphe of both valves and also as a sheath enveloping the silica frustule. Such quantities of extracellular material are absent in conventionally fixed motile diatoms. Numerous cytoplasmic vesicles, with fibrillar contents, distributed peripherally but concentrated along the raphe and at the cell poles, react strongly with a polysaccharide specific stain; their distribution in the cell and polysaccharide content suggest these may be the source of raphe and sheath material. Results support the most recent theories on the mechanism of locomotion in outline only; the details cannot be clarified. Localization procedures using alcian blue and silver staining of peroxidised sections are discussed briefly.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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