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  • 2020-2024
  • 2005-2009  (51)
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  • 1970-1974  (90)
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  • 1
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    Jahresbericht 2005 (2006)
    Details
    Publication Date: 2019-10-24
    Keywords: ddc:000
    Language: German
    Type: annualzib , doc-type:report
    Format: application/pdf
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  • 2
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    Convergence of the Control Reduced Interior Point Method for PDE Constrained Optimal Control with State Constraints (2006)
    Details
    Publication Date: 2014-02-26
    Description: We propose a variant of the control reduced interior point method for the solution of state constrained problems. We show convergence of the corresponding interior point pathfollowing algorithm in function space. Morever, we provide error bounds for the iterates.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 3
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    A Complex Mathematical Model of the Human Menstrual Cycle (2006)
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    Publication Date: 2014-02-26
    Description: This paper aims at presenting the complex coupled network of the human menstrual cycle to the interested community. Beyond the presently popular smaller models, where important network components arise only as extremely simplified source terms, we add: the GnRH pulse generator in the hypothalamus, receptor binding, and the biosynthesis in the ovaries. Simulation and parameter identification are left to a forthcoming paper.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 4
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    A continuity result for Nemyckii Operators and some applications in PDE constrained optimal control (2006)
    Details
    Publication Date: 2014-02-26
    Description: This work explores two applications of a classical result on the continuity of Nemyckii operators to optimal control with PDEs. First, we present an alternative approach to the analysis of Newton's method for function space problems involving semi-smooth Nemyckii operators. A concise proof for superlinear convergence is presented, and sharpened bounds on the rate of convergence are derived. Second, we derive second order sufficient conditions for problems, where the underlying PDE has poor regularity properties. We point out that the analytical structure in both topics is essentially the same.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
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  • 5
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    Nash Equilibria in Online Sequential Routing Games (2006)
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    Publication Date: 2014-02-26
    Description: In this paper, we study the efficiency of Nash equilibria for a sequence of nonatomic routing games. We assume that the games are played consecutively in time in an online fashion: by the time of playing game $i$, future games $i+1,\dots,n$ are not known, and, once players of game $i$ are in equilibrium, their corresponding strategies and costs remain fixed. Given a sequence of games, the cost for the sequence of Nash equilibria is defined as the sum of the cost of each game. We analyze the efficiency of a sequence of Nash equilibria in terms of competitive analysis arising in the online optimization field. Our main result states that the online algorithm $\sl {SeqNash}$ consisting of the sequence of Nash equilibria is $\frac{4n}{2+n}$-competitive for affine linear latency functions. For $n=1$, this result contains the bound on the price of anarchy of $\frac{4}{3}$ for affine linear latency functions of Roughgarden and Tardos [2002] as a special case. Furthermore, we analyze a problem variant with a modified cost function that reflects the total congestion cost, when all games have been played. In this case, we prove an upper bound of $\frac{4n}{2+n}$ on the competitive ratio of $\sl {SeqNash}$. We further prove a lower bound of $\frac{3n-2}{n}$ of $\sl {SeqNash}$ showing that for $n=2$ our upper bound is tight.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
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  • 6
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    Adaptive, Fast and Oblivious Convolution in Evolution Equations with Memory (2006)
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    Publication Date: 2016-06-09
    Description: To approximate convolutions which occur in evolution equations with memory terms, a variable-stepsize algorithm is presented for which advancing $N$ steps requires only $O(N\log N)$ operations and $O(\log N)$ active memory, in place of $O(N^2)$ operations and $O(N)$ memory for a direct implementation. A basic feature of the fast algorithm is the reduction, via contour integral representations, to differential equations which are solved numerically with adaptive step sizes. Rather than the kernel itself, its Laplace transform is used in the algorithm. The algorithm is illustrated on three examples: a blow-up example originating from a Schrödinger equation with concentrated nonlinearity, chemical reactions with inhibited diffusion, and viscoelasticity with a fractional order constitutive law.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
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  • 7
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    Two-layer Network Design by Branch-and-Cut featuring MIP-based Heuristics (2006)
    Details
    Publication Date: 2020-11-13
    Description: This paper deals with MIP-based primal heuristics to be used within a branch-and-cut approach for solving multi-layer telecommunication network design problems. Based on a mixed-integer programming formulation for two network layers, we present three heuristics for solving important subproblems, two of which solve a sub-MIP. On multi-layer planning instances with many parallel logical links, we show the effectiveness of our heuristics in finding good solutions early in the branch-and-cut search tree.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
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  • 8
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    Adaptive Finite Element Simulation of Ventricular Fibrillation Dynamics (2006)
    Details
    Publication Date: 2019-05-10
    Description: The dynamics of ventricular fibrillation caused by irregular excitation is simulated in the frame of the monodomain model with an action potential model due to Aliev-Panfilov for a human 3D geometry. The numerical solution of this multiscale reaction-diffusion problem is attacked by algorithms which are fully adaptive in both space and time (code library {\sc Kardos}). The obtained results clearly demonstrate an accurate resolution of the cardiac potential during the excitation and the plateau phases (in the regular cycle) as well as after a reentrant excitation (in the irregular cycle).
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
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  • 9
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    Orbitopal Fixing (2006)
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    Publication Date: 2020-12-15
    Description: The topic of this paper are integer programming models in which a subset of 0/1-variables encode a partitioning of a set of objects into disjoint subsets. Such models can be surprisingly hard to solve by branch-and-cut algorithms if the permutation of the subsets of the partition is irrelevant. This kind of symmetry unnecessarily blows up the branch-and-cut tree. We present a general tool, called orbitopal fixing, for enhancing the capabilities of branch-and-cut algorithms in solving this kind of symmetric integer programming models. We devise a linear time algorithm that, applied at each node of the branch-and-cut tree, removes redundant parts of the tree produced by the above mentioned permutations. The method relies on certain polyhedra, called orbitopes, which have been investigated in (Kaibel and Pfetsch (2006)). However, it does not add inequalities to the model, and thus, it does not increase the difficulty of solving the linear programming relaxations. We demonstrate the computational power of orbitopal fixing at the example of a graph partitioning problem motivated from frequency planning in mobile telecommunication networks.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
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  • 10
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    Approximability of Unsplittable Shortest Path Routing Problems (2006)
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    Publication Date: 2014-11-10
    Description: In this paper, we discuss the relation of unsplittable shortest path routing (USPR) to other routing schemes and study the approximability of three USPR network planning problems. Given a digraph $D=(V,A)$ and a set $K$ of directed commodities, an USPR is a set of flow paths $\Phi_{(s,t)}$, $(s,t)\in K$, such that there exists a metric $\lambda=(\lambda_a)\in \mathbb{Z}^A_+$ with respect to which each $\Phi_{(s,t)}$ is the unique shortest $(s,t)$-path. In the \textsc{Min-Con-USPR} problem, we seek for an USPR that minimizes the maximum congestion over all arcs. We show that this problem is hard to approximate within a factor of $\mathcal{O}(|V|^{1-\epsilon})$, but easily approximable within min$(|A|,|K|)$ in general and within $\mathcal{O}(1)$ if the underlying graph is an undirected cycle or a bidirected ring. We also construct examples where the minimum congestion that can be obtained by USPR is a factor of $\Omega(|V|^2)$ larger than that achievable by unsplittable flow routing or by shortest multi-path routing, and a factor of $\Omega(|V|)$ larger than by unsplittable source-invariant routing. In the CAP-USPR problem, we seek for a minimum cost installation of integer arc capacities that admit an USPR of the given commodities. We prove that this problem is $\mathcal{NP}$-hard to approximate within $2-\epsilon$ (even in the undirected case), and we devise approximation algorithms for various special cases. The fixed charge network design problem \textsc{Cap-USPR}, where the task is to find a minimum cost subgraph of $D$ whose fixed arc capacities admit an USPR of the commodities, is shown to be $\mathcal{NPO}$-complete. All three problems are of great practical interest in the planning of telecommunication networks that are based on shortest path routing protocols. Our results indicate that they are harder than the corresponding unsplittable flow or shortest multi-path routing problems.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
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  • 11
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    Availability and Cost Based Evaluation of Demand-wise Shared Protection (2006)
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    Publication Date: 2014-11-11
    Description: In this paper, we investigate the connection availabilities for the new protection scheme Demand-wise Shared Protection (DSP) and describe an appropriate approach for their computation. The exemplary case study on two realistic network scenarios shows that in most cases the availabilities for DSP are comparable with that for 1+1 path protection and better than in case of shared path protection.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 12
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    THESEUS - Protein Structure Prediction at ZIB (2006)
    Details
    Publication Date: 2016-06-30
    Description: THESEUS, the ZIB threading environment, is a parallel implementation of a protein threading based on a multi-queued branch-and-bound optimal search algorithm to find the best sequence-to-structure alignment through a library of template structures. THESEUS uses a template core model based on secondary structure definition and a scoring function based on knowledge-based potentials reflecting pairwise interactions and the chemical environment, as well as pseudo energies for homology detection, loop alignment, and secondary structure matching. The threading core is implemented in C++ as a SPMD parallization architecture using MPI for communication. The environment is designed for generic testing of different scoring functions, e.g. different secondary structure prediction terms, different scoring matrices and information derived from multiple sequence alignments. A validaton of the structure prediction results has been done on the basis of standard threading benchmark sets. THESEUS successfully participated in the 6th Critical Assessment of Techniques for Protein Structure Prediction (CASP) 2004.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 13
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    On the stability of the multi-queue multi-server processor sharing with limited service (2006)
    Details
    Publication Date: 2014-02-26
    Description: We consider a multi-queue multi-server system with $n$ servers (processors) and $m$ queues. At the system there arrives a stationary and ergodic stream of $m$ different types of requests with service requirements which are served according to the following $k$-limited head of the line processor sharing discipline: The first $k$ requests at the head of the $m$ queues are served in processor sharing by the $n$ processors, where each request may receive at most the capacity of one processor. By means of sample path analysis and Loynes' monotonicity method, a stationary and ergodic state process is constructed, and a necessary as well as a sufficient condition for the stability of the $m$ separate queues are given, which are tight within the class of all stationary ergodic inputs. These conditions lead to tight necessary and sufficient conditions for the whole system, also in case of permanent customers, generalizing an earlier result by the authors for the case of $n$=$k$=1.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 14
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    ConfJump : a fast biomolecular sampling method which drills tunnels through high mountains (2006)
    Details
    Publication Date: 2014-02-26
    Description: In order to compute the thermodynamic weights of the different metastable conformations of a molecule, we want to approximate the molecule's Boltzmann distribution in a reasonable time. This is an essential issue in computational drug design. The energy landscape of active biomolecules is generally very rough with a lot of high barriers and low regions. Many of the algorithms that perform such samplings (e.g. the hybrid Monte Carlo method) have difficulties with such landscapes. They are trapped in low-energy regions for a very long time and cannot overcome high barriers. Moving from one low-energy region to another is a very rare event. For these reasons, the distribution of the generated sampling points converges very slowly against the thermodynamically correct distribution of the molecule. The idea of ConfJump is to use $a~priori$ knowledge of the localization of low-energy regions to enhance the sampling with artificial jumps between these low-energy regions. The artificial jumps are combined with the hybrid Monte Carlo method. This allows the computation of some dynamical properties of the molecule. In ConfJump, the detailed balance condition is satisfied and the mathematically correct molecular distribution is sampled.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 15
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    Mathematik für den Volkssport (2006)
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    Publication Date: 2020-02-11
    Description: "`Volkssport Sudoku"' titelt der Stern in seiner Ausgabe vom 24. Mai2006. In der Tat traut sich derzeit kaum noch eine Zeitung, ohne Sudoku zu erscheinen. Die Begeisterung am Lösen dieser Zahlenrätsel offenbart eine unvermutete Freude am algorithmischen Arbeiten. Mathematisch kann man Sudokus als lineare diophantische Gleichungssysteme mit Nichtnegativitätsbedingungen formulieren. Solche ganzzahligen linearen Programme sind die wichtigsten Modellierungswerkzeuge in zahlreichen Anwendungsgebieten wie z.B. der Optimierung von Telekommunikations- und Verkehrsnetzen. Moderne Verfahren zur Lösung dieser Optimierungsprobleme sind durch Sudokus allerdings deutlich weniger zu beeindrucken als Zeitungsleser.
    Keywords: ddc:000
    Language: German
    Type: reportzib , doc-type:preprint
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  • 16
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    Mathematical Methods for Physical Layout of Printed Circuit Boards: An Overview (2006)
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    Publication Date: 2020-02-11
    Description: This article surveys mathematical models and methods used for physical PCB layout, i.e., component placement and wire routing. The main concepts are briefly described together with relevant references.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 17
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    Competitive Online Multicommodity Routing (2006)
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    Publication Date: 2020-12-15
    Description: We study online multicommodity minimum cost routing problems in networks, where commodities have to be routed sequentially. Arcs are equipped with load dependent price functions defining the routing weights. We discuss an online algorithm that routes each commodity by minimizing a convex cost function that depends on the demands that are previously routed. We present a competitive analysis of this algorithm showing that for affine linear price functions this algorithm is $4K/2+K$-competitive, where $K$ is the number of commodities. For the parallel arc case this algorithm is optimal. Without restrictions on the price functions and network, no algorithm is competitive. Finally, we investigate a variant in which the demands have to be routed unsplittably.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 18
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    The extreme points of QSTAB(G) and its implications (2006)
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    Publication Date: 2021-03-16
    Description: Perfect graphs constitute a well-studied graph class with a rich structure, reflected by many characterizations w.r.t different concepts. Perfect graphs are, e.g., characterized as precisely those graphs $G$ where the stable set polytope STAB$(G)$ coincides with the clique constraint stable set polytope QSTAB$(G)$. For all imperfect graphs STAB$(G) \subset$ QSTAB$(G)$ holds and, therefore, it is natural to measure imperfection in terms of the difference between STAB$(G)$ and QSTAB$(G)$. Several concepts have been developed in this direction, for instance the dilation ratio of STAB$(G)$ and QSTAB$(G)$ which is equivalent to the imperfection ratio imp$(G)$ of $G$. To determine imp$(G)$, both knowledge on the facets of STAB$(G)$ and the extreme points of QSTAB$(G)$ is required. The anti-blocking theory of polyhedra yields all {\em dominating} extreme points of QSTAB$(G)$, provided a complete description of the facets of STAB$(\overline G)$ is known. As this is typically not the case, we extend the result on anti-blocking polyhedra to a {\em complete} characterization of the extreme points of QSTAB$(G)$ by establishing a 1-1 correspondence to the facet-defining subgraphs of $\overline G$. We discuss several consequences, in particular, we give alternative proofs of several famous results.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 19
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    On exact algorithms for treewidth (2006)
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    Publication Date: 2014-11-10
    Description: We give experimental and theoretical results on the problem of computing the treewidth of a graph by exact exponential time algorithms using exponential space or using only polynomial space. We first report on an implementation of a dynamic programming algorithm for computing the treewidth of a graph with running time $O^\ast(2^n)$. This algorithm is based on the old dynamic programming method introduced by Held and Karp for the {\sc Tra veling Salesman} problem. We use some optimizations that do not affect the worst case running time but improve on the running time on actual instances and can be seen to be practical for small instances. However, our experiments show that the space use d by the algorithm is an important factor to what input sizes the algorithm is effective. For this purpose, we settle the problem of computing treewidth under the restriction that the space used is only polynomial. In this direction we give a simple $O^\ast(4^n)$ al gorithm that requires {\em polynomial} space. We also show that with a more complicated algorithm, using balanced separators, {\sc Treewidth} can be computed in $O^\ast(2.9512^n)$ time and polynomial space.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 20
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    Coarse Grained Molecular Kinetics (2006)
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    Publication Date: 2014-03-10
    Description: The dynamic behavior of molecules can often be described by Markov processes. From computational molecular simulations one can derive transition rates or transition probabilities between subsets of the discretized conformational space. On the basis of this dynamic information, the spatial subsets are combined into a small number of so-called metastable molecular conformations. This is done by clustering methods like the Robust Perron Cluster Analysis (PCCA+). Up to now it is an open question how this coarse graining in space can be transformed to a coarse graining of the Markov chain while preserving the essential dynamic information. In the following article we aim at a consistent coarse graining of transition probabilities or rates on the basis of metastable conformations such that important physical and mathematical relations are preserved. This approach is new because PCCA+ computes molecular conformations as linear combinations of the dominant eigenvectors of the transition matrix which does not hold for other clustering methods.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 21
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    RSWK/SWD und Faceted Browsing: neue Möglichkeiten einer inhaltlich-intuitiven Navigation (2006)
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    Publication Date: 2014-02-26
    Description: Das deutschsprachige Bibliothekswesen verfügt mit den \glqq Regeln für den Schlagwortkatalog \grqq (RSWK) unter Verwendung der \glqq Schlagwortnormdatei \grqq (SWD) über ein Instrumentarium, welches zusammen mit einem \glqq Faceted Browsing \grqq das bisher bestehende Angebot für ein Information Retrieval optimal ergänzen kann. Die Verbindung zwischen Standardvokabular (SWD) und Kettenbildung (RSWK) einerseits und eine nach Facetten-Eigenschaften gegliederte Navigation andererseits unterstützt bestmöglich eine inhaltlich bezogene Recherche. Die Stärken und Schwächen der RSWK/SWD werden erörtert und auch Klassifikationen (DDC und RVK) als mögliche Facetten diskutiert.
    Keywords: ddc:000
    Language: German
    Type: reportzib , doc-type:preprint
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  • 22
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    Accuracy, Stability, Convergence of Rigorous Thermodynamic Sampling Methods (2006)
    Details
    Publication Date: 2016-06-09
    Keywords: ddc:000
    Language: English
    Type: masterthesis , doc-type:masterThesis
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  • 23
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    Primal Heuristics for Mixed Integer Programs (2006)
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    Publication Date: 2022-03-14
    Description: A lot of problems arising in Combinatorial Optimization and Operations Research can be formulated as Mixed Integer Programs (MIP). Although MIP-solving is an NP-hard optimization problem, many practically relevant instances can be solved in reasonable time. In modern MIP-solvers like the branch-cut-and-price-framework SCIP, primal heuristics play a major role in finding and improving feasible solutions at the early steps of the solution process. This helps to reduce the overall computational effort, guides the remaining search process, and proves the feasibility of the MIP model. Furthermore, a heuristic solution with a small gap to optimality often is sufficient in practice. We investigate 16 different heuristics, all of which are available in SCIP. Four of them arise from the literature of the last decade, nine are specific implementations of general heuristic ideas, three have been newly developed. We present an improved version of the feasibility pump heuristic by Fischetti et al., which in experiments produced solutions with only a third of the optimality gap compared to the original version. Furthermore, we introduce two new Large Neighborhood Search (LNS) heuristics. Crossover is an LNS improvement heuristic making use of similarities of diverse MIP solutions to generate new incumbent solutions. RENS is an LNS rounding heuristic which evaluates the space of all possible roundings of a fractional LP-solution. This heuristic makes it possible to determine whether a point can be rounded to an integer solution and which is the best possible rounding. We conclude with a computational comparison of all described heuristics. It points out that a single heuristic on its own has only a slight impact on the overall performance of SCIP, but the combination of all of them reduces the running time by a factor of two compared to a version without any heuristics.
    Keywords: ddc:000
    Language: English
    Type: masterthesis , doc-type:masterThesis
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  • 24
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    A cartesian grid finite volume method for the solution of the Poisson equation with variable coefficients and embedded interfaces (2006)
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    Publication Date: 2014-02-26
    Description: We present a finite volume method for the solution of the two-dimensional Poisson equation $ \nabla\cdot( \beta( {\mbox{\boldmath $x$}}) \nabla u({\mbox{\boldmath $x$}})) = f(\mbox{\boldmath $x$}) $ with variable, discontinuous coefficients and solution discontinuities on irregular domains. The method uses bilinear ansatz functions on Cartesian grids for the solution $u({\mbox{\boldmath $x$})$ resulting in a compact nine-point stencil. The resulting linear problem has been solved with a standard multigrid solver. Singularities associated with vanishing partial volumes of intersected grid cells or the dual bilinear ansatz itself are removed by a two-step asymptotic approach. The method achieves second order of accuracy in the $L^\infty$ and $L^2$ norm.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 25
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    Efficient Sampling of the Stationary Distribution of Metastable Dynamical Systems (2006)
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    Publication Date: 2014-11-11
    Description: In this article we aim at an efficient sampling of the stationary distribution of dynamical systems in the presence of metastabilities. In the past decade many sophisticated algorithms have been inven ted in this field. We do not want to simply add a further one. We address the problem that one has applied a sampling algorithm for a dynamical system many times. This leads to different samplings which more or less represent the stationary distribution partially very well, but which are still far away from ergodicity or from the global stationary distribution. We will show how these samplings can be joined together in order to get one global sampling of the stationary distribution.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 26
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    Polynomial-Time Algorithms for Linear and Convex Optimization on Jump Systems (2006)
    Details
    Publication Date: 2014-02-26
    Description: The concept of jump system, introduced by Buchet and Cunningham (1995), is a set of integer points with a certain exchange property. In this paper, we discuss several linear and convex optimization problems on jump systems and show that these problems can be solved in polynomial time under the assumption that a membership oracle for a jump system is available. We firstly present a polynomial-time implementation of the greedy algorithm for the minimization of a linear function. We then consider the minimization of a separable-convex function on a jump system, and propose the first polynomial-time algorithm for this problem. The algorithm is based on the domain reduction approach developed in Shioura (1998). We finally consider the concept of M-convex functions on constant-parity jump systems which has been recently proposed by Murota (2006). It is shown that the minimization of an M-convex function can be solved in polynomial time by the domain reduction approach.
    Keywords: ddc:000
    Language: English
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    Packing and Partitioning Orbitopes (2006)
    Details
    Publication Date: 2020-12-15
    Description: We introduce orbitopes as the convex hulls of 0/1-matrices that are lexicographically maximal subject to a group acting on the columns. Special cases are packing and partitioning orbitopes, which arise from restrictions to matrices with at most or exactly one 1-entry in each row, respectively. The goal of investigating these polytopes is to gain insight into ways of breaking certain symmetries in integer programs by adding constraints, e.g., for a well-known formulation of the graph coloring problem. We provide a thorough polyhedral investigation of packing and partitioning orbitopes for the cases in which the group acting on the columns is the cyclic group or the symmetric group. Our main results are complete linear inequality descriptions of these polytopes by facet-defining inequalities. For the cyclic group case, the descriptions turn out to be totally unimodular, while for the symmetric group case, both the description and the proof are more involved. The associated separation problems can be solved in linear time.
    Keywords: ddc:000
    Language: English
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  • 28
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    LP-Based Local Approximation for Markov Decision Problems (2006)
    Details
    Publication Date: 2014-11-21
    Description: The standard computational methods for computing the optimal value functions of Markov Decision Problems (MDP) require the exploration of the entire state space. This is practically infeasible for applications with huge numbers of states as they arise, e.\,g., from modeling the decisions in online optimization problems by MDPs. Exploiting column generation techniques, we propose and apply an LP-based method to determine an $\varepsilon$-approximation of the optimal value function at a given state by inspecting only states in a small neighborhood. In the context of online optimization problems, we use these methods in order to evaluate the quality of concrete policies with respect to given initial states. Moreover, the tools can also be used to obtain evidence of the impact of single decisions. This way, they can be utilized in the design of policies.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 29
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    Ein gemischt-ganzzahliges lineares Optimierungsmodell für ein Laserschweißproblem im Karosseriebau (2006)
    Details
    Publication Date: 2014-11-21
    Description: Wir beschäftigen uns mit dem Problem der Betriebsplanung von Laserschweißrobotern im Karosseriebau. Gegeben ist eine Menge von Schweißnähten, die innerhalb einer Fertigungszelle an einem Karosserieteil gefertigt werden müssen. Die Schweißnähte werden durch mehrere parallel betriebene Roboter bearbeitet. Die Aufgabe besteht darin, für jeden Roboter eine Reihenfolge und eine zeitliche Koordinierung seiner Bewegungen zu finden, so dass alle Schweißnähte innerhalb der Taktzeit der Fertigungszelle bearbeitet werden und so wenig Laserquellen wie möglich eingesetzt werden. Dabei müssen einige Nebenbedingungen berücksichtigt werden. Für dieses spezielle Schweißproblem haben wir eine Formulierung als gemischt-ganzzahliges lineares Programm entwickelt, welches sich für die untersuchten praktischen Fälle sehr schnell lösen lässt.
    Keywords: ddc:000
    Language: German
    Type: reportzib , doc-type:preprint
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  • 30
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    Software for Teaching Modeling of Integer Programming Problems (2006)
    Details
    Publication Date: 2021-08-05
    Description: Modern applications of mathematical programming must take into account a multitude of technical details, business demands, and legal requirements. Teaching the mathematical modeling of such issues and their interrelations requires real-world examples that are well beyond the toy sizes that can be tackled with the student editions of most commercial software packages. We present a new tool, which is freely available for academic use including complete source code. It consists of an algebraic modeling language and a linear mixed integer programming solver. The performance and features of the tool are in the range of current state-of-the-art commercial tools, though not in all aspects as good as the best ones. Our tool does allow the execution and analysis of large real-world instances in the classroom and can therefore enhance the teaching of problem solving issues. Teaching experience has been gathered and practical usability was tested in classes at several universities and a two week intensive block course at TU Berlin. The feedback from students and teachers has been very positive.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 31
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    On the Bottleneck Shortest Path Problem (2006)
    Details
    Publication Date: 2014-11-21
    Description: The Bottleneck Shortest Path Problem is a basic problem in network optimization. The goal is to determine the limiting capacity of any path between two specified vertices of the network. This is equivalent to determining the unsplittable maximum flow between the two vertices. In this note we analyze the complexity of the problem, its relation to the Shortest Path Problem, and the impact of the underlying machine/computation model.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 32
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    Graph Coloring Manifolds (2006)
    Details
    Publication Date: 2014-02-26
    Description: We introduce a new and rich class of graph coloring manifolds via the Hom complex construction of Lov\´{a}sz. The class comprises examples of Stiefel manifolds, series of spheres and products of spheres, cubical surfaces, as well as examples of Seifert manifolds. Asymptotically, graph coloring manifolds provide examples of highly connected, highly symmetric manifolds.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 33
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    Polyhedra of Genus 3 with 10 Vertices and Minimal Coordinates (2006)
    Details
    Publication Date: 2014-02-26
    Description: We give coordinate-minimal geometric realizations in general position for 17 of the 20 vertex-minimal triangulations of the orientable surface of genus 3 in the 5x5x5-cube.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 34
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    ConFlow? A new space-based Application for complete Conformational Analysis of Molecules (2006)
    Details
    Publication Date: 2014-02-26
    Description: Biochemical interactions are determined by the 3D-structure of the involved components - thus the identification of conformations is a key for many applications in rational drug design. {\sf ConFlow} is a new multilevel approach to conformational analysis with main focus on completeness in investigation of conformational space. In contrast to known conformational analysis, the starting point for design is a space-based description of conformational areas. A tight integration of sampling and analysis leads to an identification of conformational areas simultaneously during sampling. An incremental decomposition of high-dimensional conformational space is used to guide the analysis. A new concept for the description of conformations and their path connected components based on convex hulls and {\em Hypercubes}is developed. The first results of the {\sf ConFlow} application constitute a 'proof of concept' and are further more highly encouraging. In comparison to conventional industrial applications, {\sf ConFlow} achieves higher accuracy and a specified degree of completeness with comparable effort.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 35
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    Iteratively Solving Linear Inverse Problems under General Convex Contraints (2006)
    Details
    Publication Date: 2014-02-26
    Description: We consider linear inverse problems where the solution is assumed to fulfill some general homogeneous convex constraint. We develop an algorithm that amounts to a projected Landweber iteration and that provides and iterative approach to the solution of this inverse problem. For relatively moderate assumptions on the constraint we can always prove weak convergence of the iterative scheme. In certain cases, i.e. for special families of convex constraints, weak convergence implies norm convergence. The presented approach covers a wide range of problems, e.g. Besov- or BV-restoration for which we present also numerical experiments in the context of image processing.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 36
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    Stable computation of probability densities for metastable dynamical systems (2006)
    Details
    Publication Date: 2014-03-10
    Description: Whenever the invariant stationary density of metastable dynamical systems decomposes into almost invariant partial densities, its computation as eigenvector of some transition probability matrix is an ill-conditioned problem. In order to avoid this computational difficulty, we suggest to apply an aggregation/disaggregation method which only addresses wellconditioned sub-problems and thus results in a stable algorithm. In contrast to existing methods, the aggregation step is done via a sampling algorithm which covers only small patches of the sampling space. Finally, the theoretical analysis is illustrated by two biomolecular examples.
    Keywords: ddc:000
    Language: English
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  • 37
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    Facets of the (s,t)-p-path polytope (2006)
    Details
    Publication Date: 2016-02-29
    Description: \noindent We give a partial description of the $(s,t)-p$-path polytope of a directed graph $D$ which is the convex hull of the incidence vectors of simple directed $(s,t)$-paths in $D$ of length $p$. First, we point out how the $(s,t)-p$-path polytope is located in the family of path and cycle polyhedra. Next, we give some classes of valid inequalities which are very similar to inequalities which are valid for the $p$-cycle polytope, that is, the convex hull of the incidence vectors of simple cycles of length $p$ in $D$. We give necessary and sufficient conditions for these inequalities to be facet defining. Furthermore, we consider a class of inequalities that has been identifie d to be valid for $(s,t)$-paths of cardinality at most $p$. Finally, we transfer the results to related polytopes, in particular, the undirected counterpart of the $(s,t)-p$-path polytope.
    Keywords: ddc:000
    Language: English
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  • 38
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    A Contact-Stabilized Newmark Method for Dynamical Contact Problems (2006)
    Details
    Publication Date: 2020-11-13
    Description: The numerical integration of dynamical contact problems often leads to instabilities at contact boundaries caused by the non-penetration condition between bodies in contact. Even a recent energy dissipative modification due to Kane et al. (1999), which discretizes the non-penetration constraints implicitly, is not able to circumvent artificial oscillations. For this reason, the present paper suggests a contact stabilization which avoids artificial oscillations at contact interfaces and is also energy dissipative. The key idea of this contact stabilization is an additional $L^2$-projection at contact interfaces, which can easily be added to any existing time integration scheme. In case of a lumped mass matrix, this projection can be carried out completely locally, thus creating only negligible additional numerical cost. For the new scheme, an elementary analysis is given, which is confirmed by numerical findings in an illustrative test example (Hertzian two body contact).
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 39
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    Implementation eines Resourcebrokers im Kontext eines Grid-Datenmanagement-Systems (2006)
    Details
    Publication Date: 2016-06-30
    Keywords: ddc:000
    Language: German
    Type: masterthesis , doc-type:masterThesis
    Format: application/pdf
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  • 40
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    Enumeration and Random Realization of Triangulated Surfaces (2006)
    Details
    Publication Date: 2014-02-26
    Description: We discuss different approaches for the enumeration of triangulated surfaces. In particular, we enumerate all triangulated surfaces with 9 and 10 vertices. We also show how geometric realizations of orientable surfaces with few vertices can be obtained by choosing coordinates randomly.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 41
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    Note on L#-convex Function Minimization Algorithms: Comparison of Murota's and Kolmogorov's Algorithms (2006)
    Details
    Publication Date: 2014-02-26
    Description: The concept of L##-convexity is introduced by Fujishige--Murota (2000) as a discrete convexity for functions defined over the integer lattice. The main aim of this note is to understand the difference of the two algorithms for L##-convex function minimization: Murota's steepest descent algorithm (2003) and Kolmogorov's primal algorithm (2005).
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 42
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    Triangulated Manifolds with Few Vertices: Combinatorial Manifolds (2006)
    Details
    Publication Date: 2014-02-26
    Description: In this survey on combinatorial properties of triangulated manifolds we discuss various lower bounds on the number of vertices of simplicial and combinatorial manifolds. Moreover, we give a list of all known examples of vertex-minimal triangulations.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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    Optimizing the Landside Operation of a Container Terminal (2006)
    Details
    Publication Date: 2020-02-11
    Description: This paper concerns the problem of operating a landside container exchange area that is serviced by multiple semi-automated rail mounted gantry cranes (RMGs) that are moving on a single bi-directional traveling lane. Such a facility is being built by Patrick Corporation at the Port Botany terminal in Sydney. The gantry cranes are a scarce resource and handle the bulk of container movements. Thus, they require a sophisticated analysis to achieve near optimal utilization. We present a three stage algorithm to manage the container exchange facility, including the scheduling of cranes, the control of associated short-term container stacking, and the allocation of delivery locations for trucks and other container transporters. The key components of our approach are a time scale decomposition, whereby an integer program controls decisions across a long time horizon to produce a balanced plan that is fed to a series of short time scale online subproblems, and a highly efficient space-time divisioning of short term storage areas. A computational evaluation shows that our heuristic can find effective solutions for the planning problem; on real-world data it yields a solution at most~8\% above a lower bound on optimal RMG utilization.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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    Triangulated Manifolds with Few Vertices: Vertex-Transitive Triangulations I (2006)
    Details
    Publication Date: 2014-02-26
    Description: We describe an algorithm for the enumeration of (candidates of) vertex-transitive combinatorial $d$-manifolds. With an implementation of our algorithm, we determine, up to combinatorial equivalence, all combinatorial manifolds with a vertex-transitive automorphism group on $n\leq 13$ vertices. With the exception of actions of groups of small order, the enumeration is extended to 14 and 15 vertices.
    Keywords: ddc:000
    Language: English
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  • 45
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    Polyhedra of Genus 2 with 10 Vertices and Minimal Coordinates (2006)
    Details
    Publication Date: 2014-02-26
    Description: We give coordinate-minimal geometric realizations in general position of all 865 vertex-minimal triangulations of the orientable surface of genus 2 in the 4x4x4-cube.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 46
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    Combinatorial 3-Manifolds with 10 Vertices (2006)
    Details
    Publication Date: 2014-02-26
    Description: We give a complete enumeration of combinatorial 3-manifolds with 10 vertices: There are precisely 247882 triangulated 3-spheres with 10 vertices as well as 518 vertex-minimal triangulations of the sphere product $S^2 x S^1$ and 615 triangulations of the twisted sphere product $S^2 \underline{x} S^1$. An analysis of the 3-spheres with up to 10 vertices shows that all these spheres are shellable, but that there are 29 vertex-minimal non-shellable 3-balls with 9 vertices.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 47
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    Adaptive Linearly Implicit Methods for Linear Poroelastic Equations (2006)
    Details
    Publication Date: 2019-05-10
    Description: Adaptive numerical methods in time and space are introduced and studied for linear poroelastic models in two and three space dimensions. We present equivalent models for linear poroelasticity and choose both the {\em displacement--pressure} and the {\em stress--pressure} formulation for our computations. Their discretizations are provided by means of linearly implicit schemes in time and linear finite elements in space. Our concept of adaptivity opens a way to a fast and reliable simulation of different loading cases defined by corresponding boundary conditions. We present some examples using our code {\sf Kardos} and show that the method works efficiently. In particular, it could be used in the simulation of some bone healing models.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 48
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    A computational approach to microRNA detection (2006)
    Details
    Publication Date: 2016-06-30
    Description: During the last few years more and more functionalities of RNA have been discovered that were previously thought of being carried out by proteins alone. One of the most striking discoveries was the de tection of microRNAs, a class of noncoding RNAs that play an important role in post-transcriptional gene regulation. Large-scale analyses are needed for the still increasingly growing amount of sequen ce data derived from new experimental technologies. In this paper we present a framework for the detection of the distinctive precursor structure of microRNAS that is based on the well-known Smith-Wat erman algorithm and various filtering steps. We conducted experiments on real genomic data and we found several new putative hits for microRNA precursor structures.
    Keywords: ddc:000
    Language: English
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    Neustart für Bibliotheken ins Informationszeitalter (2006)
    Details
    Publication Date: 2014-02-26
    Description: Wir erleben zu Beginn des aufkommenden Informationszeitalters mit dem Siegeszug von Google und anderen Internet-Technologien einen Wandel im Verhalten von Wissenschaftlern und Studenten, der mit dem Einsatz von {\sl Google Scholar} und {\sl Google Book Search} einen Paradigmenwechsel für Bibliotheken und Informationsversorger gleichkommt. Der Artikel untersucht die technischen Hintergründe für den Erfolg dieser besonderen Art des Information Retrievals: Fulltext Indexing und Citation Ranking als besondere Form des Information Minig. Er diskutiert Stärken und auch Schwächen des Google-Ansatzes. Der Autor stellt sich auch der Frage, unter welchen Bedingungen es möglich ist, ein zu {\sl Google Scholar} und der {\sl Google Book Search} konkurrenzfähiges Retrieval in der Landschaft der Bibliotheken und Bibliotheksverbünde zu entrichten. Die These ist, dass dieses unter Einsatz des {\sl Open Source} Indexierers {\sl Lucene} und des Web-Robots {\sl Nutch} möglich ist. Bibliotheken können durch gezielten Einsatz solcher Internet-Technologien dem Nutzer die Leistungen, welche Google uns mit seinen Tools im {\sl Visible Web} und mit Referenzen auf {\sl Citations} in der Welt der Literatur zur Verfügung stellt, in vergleichbarer Art auch für ihre eigenen durch Lizenzen geschützten digitalen Journale und ihre speziellen lokal verfügbaren Ressourcen, auf die Internet-Suchmaschinen keine Zugriff haben, anbieten. Es besteht die Hoffnung, dass Nutzer dann nicht - wie in einer kürzlichen Studie des OCLC konstatiert - überwiegend im Internet verbleiben, sondern bei ihrer Suche auch den Weg zu den Angeboten der örtlichen Bibliothek attraktiv finden.
    Keywords: ddc:000
    Language: German
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  • 50
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    Waiting times for M/M systems under generalized processor sharing (2006)
    Details
    Publication Date: 2014-02-26
    Description: We consider a system where the arrivals form a Poisson process and the required service times of the requests are exponentially distributed. According to the generalized processor sharing discipline, each request in the system receives a fraction of the capacity of one processor which depends on the actual number of requests in the system. We derive systems of ordinary differential equations for the LST and for the moments of the conditional waiting time of a request with given required service time as well as a stable and fast recursive algorithm for the LST of the second moment of the conditional waiting time, which in particular yields the second moment of the unconditional waiting time. Moreover, asymptotically tight upper bounds for the moments of the conditional waiting time are given. The presented numerical results for the first two moments of the sojourn times in the $M/M/m-PS$ system show that the proposed algorithms work well.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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    Domain Decomposition Method for Maxwell's Equations: Scattering off Periodic Structures (2006)
    Details
    Publication Date: 2022-07-07
    Description: We present a domain decomposition approach for the computation of the electromagnetic field within periodic structures. We use a Schwarz method with transparent boundary conditions at the interfaces of the domains. Transparent boundary conditions are approximated by the perfectly matched layer method (PML). To cope with Wood anomalies appearing in periodic structures an adaptive strategy to determine optimal PML parameters is developed. We focus on the application to typical EUV lithography line masks. Light propagation within the multi-layer stack of the EUV mask is treated analytically. This results in a drastic reduction of the computational costs and allows for the simulation of next generation lithography masks on a standard personal computer.
    Keywords: ddc:000
    Language: English
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  • 52
    Electronic Resource
    Electronic Resource
    Chondrogenesis in the external ear of the rat (1970)
    Springer
    Anatomy and embryology 131 (1970), S. 236-242 
    Details
    ISSN: 1432-0568
    Keywords: Cartilage ; Ear, external ; Differentiation ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The differentiation of cartilage in the external ear of the rat proceeds in four steps. Each of them is characterized by a specific biosynthetic activity of the chondroblast resulting in the appearance of a new structural component of the tissue: collagen fibrils, elastin fibers, cartilage ground substance and intracellular fat droplets. As a structurally and developmentally well-defined “subspecies” of cartilage, this tissue might serve as a suitable object for the experimental approach to some essential problems in histodifferentiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00520966
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    Electronic Resource
    Electronic Resource
    Elektronenmikroskopische Untersuchungen zum Problem des Stoffaustausches zwischen Mutter und Keim bei Rattenembryonen des Tages 7–10 (1970)
    Springer
    Anatomy and embryology 131 (1970), S. 325-346 
    Details
    ISSN: 1432-0568
    Keywords: Rat ; Early development ; Jolk-sac entoderm ; Reichert's membrane ; Trophoblast-cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Rattenkeime des Schwangerschaftstages 7–10 wurden elektronenmikroskopisch untersucht. Das viscerale einschichtige Dottersackentoderm zeichnet sich durch eine ausgeprägte endocytotische Aktivität aus. Die Zellen des parietalen Blattes dagegen liegen isoliert der Reichertschen Membran innen an und enthalten vorwiegend rauhes endoplasmatisches Reticulum. Die Reichertsche Membran besteht aus einem lockeren Maschengitter feiner Filamente. Im antimesometrialen und lateralen Bereich haften nur wenige Trophoblastenzellen dieser Membran von außen an, dazwischen befinden sich weite Lücken. Zum mütterlichen Gewebe hin wird der Keim mit Ausnahme des mesometrialen Poles von einem bis zu 50 μ breiten periembryonalen Sinus umgeben, der mütterliches Blut enthält. Nach außen wird dieser Raum durch Trophoblasten- und Deciduazellen abgedichtet. Aus diesen Befunden wird geschlossen: 1. Die Reichertsche Membran wird vom parietalen Dottersack-Entoderm gebildet. 2. Mütterliches Blutplasma kann frei das viscerale Dottersack-Entoderm erreichen, da als einzige kontinuierliche Schicht zwischen Blut und Träger nur die weitmaschige Reichertsche Membran vorhanden ist. 3. Durch das endocytotische und lysosomale System des visceralen Dottersackentoderms wird das anströmende mütterliche Plasma aufgenommen, abgebaut und für den wachsenden Keim nutzbar gemacht. 4. Immunbiologisch betrachtet können Antikörper der Mutter den Keim erreichen. 5. Embryonale Antigene dagegen erreichen durch die Errichtung einer Deciduabarriere nicht den mütterlichen Kreislauf. 6. Der periembryonale Sinus stellt einen Blindsack dar, in den zwar mütterliches Blut einströmen kann, ein Ausstrom aber nicht mehr möglich ist.
    Notes: Summary Electron microscope studies of rat embryos were performed from the 7th to 10th days of pregnancy. The single-layered visceral yolk entoderm is characterized by a marked endocytotic activity. The cells of the parietal layer lie separately adjacent to the Reichert's membrane and they contain mainly rough endoplasmic reticulum. The Reichert's membrane consists of a loose network of fine filaments. In the antimesometrial and lateral sites only few trophoblast cells are seen to be attached to the membrane. Between them we find large gaps. With the exception of the mesometrial pole, the embryo is surrounded by a periembryonal sinus, 10–50 μ wide, which contains maternal blood. This sinus space is sealed tightly (zonulae occludentes) by trophoblast and decidual cells. From these findings it was concluded: 1. Reichert's membrane is formed from the parietal jolk sac entoderm. 2. The porous Reichert's membrane permits the maternal plasma to reach freely the visceral jolk sac entoderm. This membrane is the only continuous layer between blood and egg cylinder. 3. By the endocytotic and lysosomal system, the visceral jolk sac entoderm absorbs the plasma coming from the mother. This plasma is degraded and used for the growing embryo. 4. From the immunobiological point of view the antibodies from the mother can reach the embryo freely, 5. The embryonal antigens cannot reach the maternal circulation because of the presence of a decidual barrier, 6. The perimebryonal sinuses are blind sacs into which the maternal blood can flood but it cannot return.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00519974
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    Über Faltungen der Kernmembranen (Kernschrumpfung) des Ependyms im III. Ventrikel der Ratte nach langdauernder intraperitonealer Narkose mit Natrium-5-(β-Methylthioäthyl)-5-(2′-pentyl)-thiobarbitursäure („Thiogenal”) (1970)
    Springer
    Acta neuropathologica 16 (1970), S. 44-53 
    Details
    ISSN: 1432-0533
    Keywords: Ependyma ; Thiobarbiturate ; Rat ; Hypothalamus ; III. Ventricle ; Narcosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung An 14 männlichen Ratten wurde nach langdauernder intraperitonealer Narkose mit Thiobarbiturat Veränderungen des Ependyms im III. Ventrikel festgestellt. In der Gegend über dem Nucleus ventromedialis und Nucleus dorsomedialis hypothalami lassen sich zwei Formen des Ependyms unterschieden: 1. ein einschichtiges hohes Ependym mit runden großen Zellkernen, 2. ein mehrreihiges flaches Ependym mit schmalen, ovalen Zellkernen. Das flache Ependym zeigt folgende Veränderungen: Farbdichte und die Menge des färbbaren Materials im Kern nehmen zu, die Kernmembran ist gefaltet, der Kern zeigt Zeichen der Schrumpfung und Pyknose. Die Kontrollgruppe wurde mit Curare behandelt. Eine statistische Sicherung erbrachte einen signifikanten Unterschied mit einer Irrtumswahrscheinlichkeit von 0,5‰.
    Notes: Summary Alterations in the ependyma of the third ventricle were caused by continuous intraperitoneal thiobarbiturate narcosis in14 male rats. In the region of the nucleus dorsomedialis and ventromedialis hypothalami two kinds of ependyma can be distinguished, 1. a simple cuboidal ependyma with a large rounded nucleus, and 2. a stratified squamous ependyma with a slender oval nucleus. The squamous ependyma shows the following changes. The depth of staining and the chromatin material of the nucleus increases, the membrane of the nucleus is folded, the nucleus shows the signs of shrinkage and pyknosos. The control group was treatened with Curare. The significant difference of the results encloses 0.5‰ probability of error.
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    URL: http://dx.doi.org/10.1007/BF00686963
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    Acoustically evoked potentials in the rat during sleep and waking (1970)
    Springer
    Experimental brain research 11 (1970), S. 93-110 
    Details
    ISSN: 1432-1106
    Keywords: Auditory evoked potentials ; Sleep ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Click-evoked potentials were recorded from the rat's auditory cortex (AC), medial geniculate body (MGB), reticular formation (RF), and hippocampus (HIPP) during natural sleep and waking. Various amplitude measurements made on sliding averages by a computer provided essentially continuous measurement of evoked responses in long experiments. Changes in AC responses were simplest in potentials recorded from a depth of 1.0–1.5 mm, all components of the average waveform being larger during slow-wave sleep (SS) than in waking (W) and low-voltage fast sleep (LVFS). More complex changes in cortical surface responses included increases in the first positive wave, in a second positive deflection, and in a late negative wave during drowsiness (D) and SS. The second positive wave remained large during LVFS, while the late negativity changed form and peaked earlier. Early components of both surface and deep responses were not consistently different in W and LVFS. The only clear change in MGB responses was a reduction in amplitude during LVFS. Late positive waves in RF and HIPP responses were large during SS and small during W and LVFS. In general, increases in the very late components of responses at all sites distinguished periods of cortical synchrony from periods of cortical activation. The first negative deflection and a succeeding positive wave in the HIPP response were markedly increased during arousal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234203
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    The identification of fractions enriched in nonmyelinated axons from rat whole brain (1970)
    Springer
    Experimental brain research 11 (1970), S. 392-410 
    Details
    ISSN: 1432-1106
    Keywords: Subcellular fractionation ; Axons ; Synaptosomes ; Whole brain ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Subfractionation of a standard “synaptosome” fraction from whole brain has yielded two lighter layers rich in axonal segments devoid of synaptosomes similar to those obtained from cerebellar homogenates. The heavier layers were found to contain both synaptosomes and axonal segments plus a significant population of synaptosomes with axons attached. Quantitative studies of the percent perimeter of external membrane contributed by the various elements within the subfractions showed that the major constituents in decreasing order were axonal segments, synaptosomes, membranes of undetermined origin and free mitochondria. These findings have revealed that “synaptosome” preparations are more heterogeneous than previously reported and at the same time have indicated the possibility of future studies on axonal preparations from whole brain. Correlated biochemical data strongly suggest chemical differences in fractions rich in axonal segments in contrast to those enriched in synaptosomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237913
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    Der Einflu\ der Durchblutung auf die Wasser- und Salzresorption im Jejunum der Ratte (1970)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 265 (1970), S. 425-441 
    Details
    ISSN: 1432-1912
    Keywords: Intestinal Blood Flow ; Water Absorption ; Solute Absorption ; Jejunum ; Rat ; Darmdurchblutung ; Wasserresorption ; Salzresorption ; Jejunum ; Ratte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The lumen of jejunal loops in rats anaesthetised with urethane were perfused with hypo-, iso- and hypertonic ringer, mannitol or glucose ringer solution. The blood flow (venous outflow), water, solute and glucose net flux were measured in the loop. 2. Lowering the blood flow from 1 ml/min/g wet tissue to 0.2–0.3 ml/min/g caused the solute and glucose net flux to decrease; the water net flux (positive or negative) was also decreased if non-isotonie solutions were used, but remained unchanged when isotonic solutions were perfused. 3. When the blood flow was raised from 0.2–0.3 ml/min/g to 1 ml/min/g the net flux of glucose, solute and water usually remained low. Using hypotonic solutions the water net flux changed to negative values, that is, fluid was passing into the lumen. 4. The influenee of intestinal blood flow on water, solute and glueose absorption can be referred to 3 factors: a) drainage by blood, b) inhibition of active transport mechanisms by anoxia during low blood flow, and c) damage to the villi as a result of insufficient blood flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00997078
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    A note on the effect of trifluoroacetate on the growth of rat liver (1970)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 265 (1970), S. 474-475 
    Details
    ISSN: 1432-1912
    Keywords: Trifluoroacetic Acid ; Trifluoroacetate ; Rat ; Liver Weight ; TrifluoressigsÄure ; Trifluoroacetat ; Ratte ; Lebergewicht
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The influence of trifluoroacetic acid (TFAA) and sodium trifluoroacetate (TFA) on the liver weight to body weight ratio was measured in rats by two methods. When TFA or TFAA were added to the drinking water at a concentrate of 1 Normal, rats became dehydrated and a slight increase in the ratio was noted after ten days. However, when these substances were administered to rats (1 ml per day) by gastric intubation no change in the ratio was noted after eight days.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00997081
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    The effects of noradrenaline on rat's behaviour (1970)
    Springer
    Psychopharmacology 16 (1970), S. 369-374 
    Details
    ISSN: 1432-2072
    Keywords: Noradrenaline ; Intraventricular Injection ; Rat ; Behaviour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The behavioural effects of NA injected without narcosis into the lateral brain ventricle of the rats were studied with two different techniques. Rats were classified according their normal level of exploratory activity into three groups: high, medium and low. It was shown that NA in a dose of 10 μg increased locomotor activity only in animals of low activity; a dose of 50 μg increased locomotor activity in all the animals; and a dose of 200 μg induced a complete abolition of locomotor activity and a stuporose syndrome lasting 2 hours. The evidence that NA in some experimental conditions increases locomotor activity of rats supports the hypothesis that NA regulates processes in the central nervous system which stimulate behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00404847
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    Psychopharmacological action of nicotinamide adenine dinucleotide (1970)
    Springer
    Psychopharmacology 17 (1970), S. 198-202 
    Details
    ISSN: 1432-2072
    Keywords: Nicotinamide Adenine Dinucleotide ; Variable Interval Schedule ; Sidman Avoidance ; Sedative Effects ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of nicotinamide adenine dinucleotide (NAD) upon the response rates in variable interval and Sidman Avoidance schedules was studied in rats. Bar pressing on the variable interval reinforcement schedule was significantly reduced during the 15 min following the administration of 10 mg/kg i.p. and during the 60 min following the administration of 30 mg/kg NAD. Response rates on the Sidman Avoidance schedule were significantly reduced during the 60 min following the administration of 100 mg/kg NAD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00402710
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    Differential effects of nicotine and tobacco smoke alkaloids on swimming endurance in the rat (1970)
    Springer
    Psychopharmacology 18 (1970), S. 300-304 
    Details
    ISSN: 1432-2072
    Keywords: Rat ; Swimming Endurance ; Nicotine ; Tobacco Alkaloids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The swimming endurance of rats in a water tub was measured until the animals submerged for two seconds under the water surface. The total alkaloid fraction extracted from cigarette smoke produced deterioration of performance in doses of 0.05 to 0.2 mg/kg, whereas pure nicotine (0.1 and 0.2 mg/kg), as well as nicotine pretreated analogously to the extraction process of the total alkaloids produced performance improvements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00412675
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    Light microscopic observations on the possible retinohypothalamic projection in the rat (1970)
    Springer
    Experimental brain research 11 (1970), S. 515-527 
    Details
    ISSN: 1432-1106
    Keywords: Visual pathway ; Hypothalamus ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Following unilateral retinal destruction in rats the existence of a direct retinohypothalamic pathway was investigated using the Nauta and the Fink-Heimer methods. Critical analysis of the Fink-Heimer stained sections of the experimental animals suggests that fibres leaving the optic pathway pass to various hypothalamic nuclei: 1. Fibres from the dorsorostral part of the chiasm pass through the lamina terminalis and appear to end in the preoptic and anterior hypothalamic nuclei. 2. Fibres leaving the ventrocaudal border of the chiasm and optic tract pass to the arcuate and ventromedial hypothalamic nuclei. 3. From the dorsocaudal part of the chiasm fibres pass to the suprachiasmatic and ventromedial hypothalamic nuclei. 4. From the caudal part of the inferior bundle of the accessory optic tract fibres pass to the premamillary ventral nucleus. The amount of apparently terminal degeneration in the preoptic, anterior hypothalamic, suprachiasmatic and premamillary nuclei was small. Heavier terminal degeneration appears to be present in the arcuate and ventromedial hypothalamic nuclei.
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    URL: http://dx.doi.org/10.1007/BF00233972
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    Electron microscopic observations on the possible retinohypothalamic projection in the rat (1970)
    Springer
    Experimental brain research 11 (1970), S. 528-538 
    Details
    ISSN: 1432-1106
    Keywords: Visual pathway ; Hypothalamus ; Arcuate nucleus ; Rat ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Degenerating nerve fibres and boutons were searched with the aid of the electron microscope in the arcuate nucleus of rats 2–7 days after bilateral destruction of the retina. In the arcuate nucleus of the control animals as well as in the operated animals, 4 types of boutons were distinguished on the basis of vesicular contents and glial ensheathment. In the operated animals changes interpreted as degenerating were found in small myelinated axons and boutons of type II (boutons containing both synaptic and granular vesicles). The changes were similar to those described in the literature as the “dark” type of degeneration in experimentally interrupted axons and boutons. Similar changes were not found in the unoperated animals. The conclusion is reached, that a small number of fibres of the optic tract reach the arcuate nucleus to terminate here.
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    URL: http://dx.doi.org/10.1007/BF00233973
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    Über die enterale Resorption von metallischem Quecksilber (1970)
    Springer
    Archives of toxicology 26 (1970), S. 203-209 
    Details
    ISSN: 1432-0738
    Keywords: Mercury ; Enteral Absorption ; Neutron Activation Analysis ; Rat ; Quecksilber ; enterale Resorption ; Neutronenaktivierungs analyse ; Ratte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Durch Neutronenaktivierungsanalyse wird nachgewiesen, daß bei der Eatte von symptomlos vertragenem metallischem Quecksilber, oral zugeführt, ein geringer Anteil resorbiert wird, welcher zu einer Erhöhung der Queeksilberwerte in Blut und Niere auf reichlich das 10fache der Norm führt.
    Notes: Summary It was demonstrated by means of neutron activation analysis that a small portion of orally administered metallic mercury is absorbed by rats. The animals tolerated this without visible symptoms, yet it resulted in a 10-fold or greater increase above normal values of mercury in blood and kidneys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00578041
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    Reninabgabe aus Nierenschnitten in Abhängigkeit von der Elektrolytzusammensetzung des Mediums (1970)
    Springer
    Pflügers Archiv 321 (1970), S. 67-82 
    Details
    ISSN: 1432-2013
    Keywords: Renin ; Angiotensin ; Electrolytes ; Kidney Slices ; Rat ; Renin ; Angiotensin ; Elektrolyte ; Nierenschnitte ; Ratte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Nierenschnitte von Wistarratten wurden in NaCl-Lösungen oder in Ringer-Bicarbonat(bzw. Phosphat-)-Puffern mit 0,1 g Glucose/l für 2 Std bei 37° C aerob inkubiert. 0,1 ml Medium wurde mit 1,9 ml Rinder-Reninsubstratlösung in Anwesenheit von Diisopropylfluorophosphat und EDTA bei pH 5,7 und 37° C für 2 Std inkubiert. Der Angiotensingehalt des Inkubates wurde im Blutdrucktest der Ratte bestimmt. In verschieden konzentrierten NaCl-Lösungen nimmt die Reninabgabe von 150–67 m Val/l (Na+) kontinuierlich ab. Auch in Ringer-Lösungen mit abnehmender NaCl-Konzentration und konstanter Konzentration der übrigen Elektrolyte findet sich zwischen 120 und 50 m Val/l (Na+) ein steiler Abfall der Reninabgabe. Bei Konstanterhaltung der Osmolarität durch zunehmenden Ersatz des NaCl durch Cholinchlorid oder Mannit vermindert sich die Steilheit der (Na+)-Abhängigkeit der Reninabgabe. Ersatz des NaCl im Bicarbonatpuffer durch verschiedene Konzentrationen von NaBr ergibt die gleichen Befunde wie mit NaCl. Bei vollständigem Ersatz des NaCl im Puffer durch verschiedene Konzentrationen von Chlolinchorid oder Mannit ist die Konzentrationsabhängigkeit der Reninabgabe weniger deutlich, bei Ersatz durch KCl nicht mehr signifikant. Die (Na+)-Abhängigkeit der Reninabgabe aus Nierenschnitten scheint nicht vom aeroben Stoffwechsel abhängig zu sein.
    Notes: Summary Rat kidney slices were incubated in saline solutions or in Ringer-bicarbonate (resp. phosphate-)-buffers containing 0.1 g/l glucose for 2 hrs at 37° C. Subsequently, 0.1 ml of the medium was incubated with 1.9 ml of ox renin-substrate solution, pH 5.7, for 2 hrs at 37° C in the presence of diisopropylfluorophosphate and EDTA. The angiotensin formed was measured by rat blood pressure assay. Renin release from kidney slices decreases markedly in NaCl-solutions between Na+-concentrations of 150 meq/l and 67 meq/l. Renin release decreases likewise in modified Ringer-solutions containing decreasing amounts of NaCl or NaBr (between 120 meq/l and 50 meq/l Na+), when the concentrations of other electrolytes are held constant. The (Na+)-dependence of renin release is less marked when the osmolarity of the medium is held constant by stepwise substitution of NaCl cholinchloride. Complete substitution of NaCl by different concentrations of cholin-chloride or mannitol diminishes the dependence of renin release on the osmolarity of the medium. Variation of KCl-concentration in the absence of NaCl does not influence renin release significantly. The (Na+)-dependence of renin release does not seem to depend on aerobic conditions.
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    Studies on adrenergic mechanisms in the action of desmethyl imipramine (DMI) (1970)
    Springer
    Psychopharmacology 17 (1970), S. 234-241 
    Details
    ISSN: 1432-2072
    Keywords: Specific Inhibition of Amine Synthesis ; Brain ; DMI and RO 4-1284 Antagonism ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The influence of α-methyl tyrosine and diethyldithiocarbamate which specifically inhibit noradrenaline synthesis and the influence of p-chlorophenylalanine which inhibits 5-hydroxytryptamine synthesis in the brain on the antagonism between desmethylimipramine and RO 4-1284 was studied. It was shown that both substances which inhibit noradrenaline synthesis abolish the behavioural antagonism between DMI and RO 4-1284, and p-chlorophenylalanine is without effect on this antagonism. The evidence shows that DMI antagonises the action of a benzoquinolizine derivative by the participation of adrenergic mechanisms.
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    URL: http://dx.doi.org/10.1007/BF00402083
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    Effect of hippocampal and neocortical ablation on scopolamine-induced activity in the rat (1970)
    Springer
    Psychopharmacology 17 (1970), S. 289-301 
    Details
    ISSN: 1432-2072
    Keywords: Scopolamine ; Hippocampus ; Activity ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To test the hypothesis that the hippocampus may be an important site of action for anticholinergic drugs, scopolamine was administered to rats with hippocampal lesions produced by aspiration and to appropriate control groups, and their activity measured. The experimental design was a four-way analysis of variance with three lesion groups, three drug levels, eight measurements in a two-hour session, and four weeks. At the two higher drug doses (0.20 and 1.0 mg/kg), rats with hippocampal or cortical lesions had significantly greater activity than the sham operates (p〈0.01 and p〈0.05, respectively). A group of Ss with electrolytic hippocampal lesions tested at 0.20 mg/kg scopolamine had transitory activity increases. Therefore the hippocampus is not necessary for the motor activating effects of the drug nor is its ablation unique in producing increases in drug-induced activity.
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    URL: http://dx.doi.org/10.1007/BF00404234
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    The effect of nicotine and total alkaloids extracted from cigarette smoke on avoidance behavior in rats under extinction procedure (1970)
    Springer
    Psychopharmacology 18 (1970), S. 305-313 
    Details
    ISSN: 1432-2072
    Keywords: Rat ; Avoidance ; Extinction ; Nicotine ; Tobacco Alkaloids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of nicotine and total alkaloids extracted from smoke on the avoidance behavior of rats under extinction procedure has been measured in an experiment extended over a period of three months. There was no significant difference between the two substances, with both inhibiting the extinction of avoidance response to approximately the same degree. Significance against the control was achieved with all treatments, the effect being significantly greater with the dose of 0.2 mg/kg than with the two doses of 0.1 or 0.05 mg/kg.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00412676
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    A new method for studying the effect of drugs on the testes of rats (1970)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 266 (1970), S. 195-198 
    Details
    ISSN: 1432-1912
    Keywords: Rat ; Testis ; Semen ; Ejaculation ; Pharmacological Tests
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Each of 12 rats was eleetroejaculated 15 times. The semen plug was liquefied in 1% alpha-chymotrypsin, enabling the spermatozoa to be counted. Spermatozoa counts averaged 7,700,000 per ejaculate with a wide range. In 5 of the animals the coagulating glands and the seminal vesicles were surgically removed. After the removal of the glands the rats were electroejaculated 10 times. The still partly coagulated semen was dissolved in 1% alpha-chymotrypsin. The total ejaculate now showed a mean count of 18,600,000 spermatozoa with only a small range. By counting and comparing the number of spermatozoa in the ejaculate in treated and untreated rats with seminal vesicles and coagulating glands removed the effect of drugs on the testes can be examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00997652
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    Zwei elektronenmikroskopisch unterscheidbare Formen sekundärer sensorischer Endigungen in einer Muskelspindel der Ratte (1970)
    Springer
    Cell & tissue research 110 (1970), S. 97-107 
    Details
    ISSN: 1432-0878
    Keywords: Muscle Spindles ; Different types of sensory endings ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung In einer Muskelspindel der Ratte, die an einer Serie alternierender Semidünn- und Ultradünnquerschnitte untersucht wurde, wurden zwei benachbart an „nuclear chain“-Fasern gelegene Nervenendformationen unterschiedlicher Bauweise festgestellt. Die beiden Endformationen sind mit ein und derselben Nervenfaser der Gruppe II verbunden und daher als Bestandteile einer sekundären sensorischen Endigung zu betrachten. Die Nervenendformation an einer der beiden „nuclear chain“-Fasern hat anulo-spirale Form. Die Nervenendformation an der anderen „nuclear chain“-Faser weist am Querschnittsbild eine Anzahl von Axonen auf, die zwischen Plasmalemm und Basalmembran der intrafusalen Muskelfaser eng aneinanderliegen. Nicht alle Axonquerschnitte stehen in direktem Kontakt mit der intrafusalen Faser. Das terminale Axon scheint sieh nach Eintritt unter die Basalmembran der intrafusalen Faser mehrfach in relativ dünne Äste unregelmäßigen Verlaufs zu teilen. Diese Form der Endigung könnte ein Korrelat der sog. „flower spray“-Endigung im Sinne Ruffinis (1898) darstellen. Die beiden morphologisch unterschiedlichen Endformationen innerhalb der sekundären Endigung gleichen einander und den Endformationen der primären Endigung bezüglich folgender Ultrastrukturmerkmale: 1. Es besteht synaptischer Kontakt zwischen Axon und intrafusaler Muskelfaser (synaptischer Spalt durchschnittlich 200 Å) ohne Zwischenlagerung von Basalmembranmaterial; 2. die terminalen Axonabschnitte liegen direkt unter der Basalmembran der intrafusalen Muskelfaser und sind nicht von Schwannschen Zellen bedeckt; 3. Mangel an synaptischen Bläschen; 4. desmosomenartige Verhaftungen zwischen Zellmembranen von Axon und intrafusaler Faser; 5. dyadenartige Anlagerungen des sarkoplasmatischen Retikulums an die Zellmembran der intrafusalen Faser im Bereich des synaptischen Spaltes. Nach unseren derzeitigen Vorstellungen sprechen diese Ultrastrukturmerkmale für eine rezeptorische Natur der beschriebenen Nervenendigungen.
    Notes: Summary In a rat muscle spindle transversally cut into a series of alternating semithin and ultrathin sections, two different forms of nerve terminations were found on two neighbouring nuclear chain fibres. The two nerve terminations were connected to the same group II nerve fibre and are consequently constituents of one particular secondary sensory ending. The nerve termination on one of the two nuclear chain fibres is of the anulo-spiral type. The nerve termination on the second nuclear chain fibre shows a number of axons lying closely together between plasma membrane and basement membrane of the intrafusal muscle fibre. Not all of these axons are in direct contact with the intrafusal fibre. The terminating nerve fibre seems to be divided into several branches of rather small diameters and irregular courses. It is suggested that this kind of termination could be a correlate of the so-called “flower spray” type of sensory endings in muscle spindles. The two morphologically different nerve terminations in the secondary ending have the following ultrastructural characteristics in common with those of the primary ending: 1) Synaptic contact between axon and intrafusal muscle fibre (synaptic gap about 200 Å) without interposition of basement membrane material; 2) terminal axons located beneath the basement membrane layer of intrafusal muscle fibres without covering by Schwann cells; 3) lack of synaptic vesicles; 4) desmosome-like structures between plasma membranes of axon and intrafusal muscle fibre, and 5) dyads of the sarcoplasmic reticulum adjacent to the synaptic cleft. According to present knowledge these features indicate that all of these endings are sensory ones.
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    Ultrastructure du lobe postérieur de l'hypophyse du rat et ses modifications au cours de l'excrétion de vasopressine (1970)
    Springer
    Cell & tissue research 108 (1970), S. 357-379 
    Details
    ISSN: 1432-0878
    Keywords: Neurohypophysis ; Rat ; Vasopressin release ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Résumé Le lobe postérieur de l'hypophyse a été examiné sur coupes ultrafines chez 45 rats (24 normaux, 17 déshydratés respectivement 1, 2 et 4 jours, et 4 anesthésiés à l'éther), après fixation au glutaraldéhyde ou selon la méthode de Karnovsky, post-fixation osmiée et double contraste à l'acétate d'uranyle et au citrate de plomb. Des fibres neurosécrétoires sombres et claires sont reconnaissables, mais les données manquent encore pour interpréter cette différence. Des densifications juxta-membranaires sont observées dans les terminaisons neurosécrétoires là où se trouvent des amas de microvésicules. Des fibres neurosécrétoires traversent parfois des pituicytes; il est aussi souvent observé des fibres, chargées de granules, libres dans un espace péricapillaire. Les espaces péricapillaires, ramifiés en tous sens loin des vaisseaux, développent une large surface de contact avec les extrémités nerveuses et les prolongements de pituicytes. Dans des conditions techniques bien contrôlées, la déshydratation n'entraîne pas de modifications appréciables des granules de neurosécrétat après 24 h. Ensuite les granules sont diminués en nombre, de façon très considérable le 4e jour; mais les granules restants ont un contenu dense normal; jamais il n'a été observé d'aspects de ≪granules vides ≫. Après anesthésie prolongée à l'éther, il n'y a aucune modification visible ni du nombre, ni de la densité des granules. Ces observations sont discutées quant au mécanisme de l'excrétion de vasopressine; elles sont en faveur de l'existence de deux pools hormonaux, l'un libre et rapidement disponible, l'autre plus fortement lié et certainement contenu dans les granules jouant le rôle de réserve. Toutefois un mécanisme d'exocytose granulaire ne peut être formellement exclu.
    Notes: Summary Hypophysial neural lobes of 45 rats (24 controls, 17 dehydrated resp. 1, 2 and 4 days, and 4 ether anesthetized) were fixed either with glutaraldehyde or according to Karnovsky and post-fixed in osmium tetroxyde; ultrathin sections were stained by uranyl acetate and lead citrate. Dark and clear neurosecretory fibres were observed, but sufficient data are still lacking for a valuable interpretation of these aspects. Juxta-membraneous densifications are visible in limited areas of neurosecretory terminals where clusters of microvesicles are present. Neurosecretory fibres happen to be completely encircled by pituioyte cytoplasm; fibres loaded with elementary granules are frequently encountered running free in a pericapillary space. Pericapillary spaces stretch out branching far away from vessels, resulting in a widespread contact with nerve terminals and pituicyte processes. In accurately controlled technical conditions, dehydratation does not result in any noticeable change of neurosecretory granules after 24 h. A decrease of the number of granules follows and is extremely conspicuous after 4 days; though, remaining granules keep a normal dense content, and aspects of “empty granules” have never been observed. After prolonged ether anesthesia, no visible change either in number or electron density of granules was observed. These findings are discussed in consideration of the mechanism of vasopressin release; they support the hypothesis of two hormonal pools, one of which would be free and rapidly available for release, the other being more tightly bound and certainly located in granules representing a storage site. Though granular exocytosis cannot be absolutely excluded.
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    Quantitativ-morphologische Untersuchungen an Herzmuskelzellen von normalen und hypoxischen Ratten (1970)
    Springer
    Cell & tissue research 109 (1970), S. 384-397 
    Details
    ISSN: 1432-0878
    Keywords: Heart muscle cells ; Electron microscopy ; Quantitative ; Asphyxia ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Normale und hypoxische Herzmuskelzellen aus der Wand des linken Ventrikels der Ratte wurden quantitativ-morphologisch anhand von elektronenmikroskopischen Längsschnitten nach Perfusionsfixierung untersucht. In normalen Zellen waren alle Myofibrillen relaxiert, die mittlere Sarcomerlänge betrug 2,2 μm. Die Schnittfläche wurde zu 55% von Myofibrillen, zu 27% von Mitochondrien und zu 18% von Grundplasma und Reticulum eingenommen. Die zwischen den Myofibrillen liegenden Mitochondrien waren längsoval und im Mittel 2,3mal so lang wie breit. Es bestand kein Unterschied zwischen subendokardial und subepikardial gelegenen Zellen. 10 min nach Erstickung der Tiere waren in den sonst unauffälligen Muskelzellen die Glycogengranula vermindert. Nach 20 min führte die Hypoxie zu einer Zunahme der relativen Schnittfläche der Mitochondrien um etwa 16% und zu einer beginnenden Kontraktur der Myofibrillen (Sarcomerlänge 2,0 μm). 20 min Hypoxie in Hypothermie (25–30°C intrathorakal) veränderte die normale Zellstruktur dagegen kaum. Wenn die Herzen während der 20 min dauernden Hypoxie in Normothermie mit einer procainhaltigen sauerstoff- und glucosefreien Blutersatzlösung durchspült wurden, waren die Myofibrillen relaxiert, die Schwellung der Mitochondrien dagegen wurde nicht reduziert. 30 min nach Erstickung wurde die Kontraktur stärker (Sarcomerlänge 1,7 μm). Nach 60 min bildeten sich Superkontraktionsknoten, einzelne Myofibrillen waren in Höhe der I-Bänder unterbrochen. Die Cristae der Mitochondrien wichen auseinander, die Schnittfläche der Mitochondrien hatte um 27% zugenommen. Während in Normotherapie eine Asphyxie des Tieres bereits nach 10 min die Herzmuskelzellen funktionell schwer schädigt, ist die Schädigung morphologisch erst nach 20 min eindeutig. Das bedeutet, daß für die elektronenmikroskopische Präparation eine Hypoxie von unter 10 min bedeutungslos ist. Hinsichtlich der morphologischen Manifestationszeit für die Unterbrechung der Sauerstoffversorgung stimmen unsere Befunde an Herzmuskelzellen gut mit vergleichbaren Angaben an Leberzellen überein.
    Notes: Summary In heart muscle cells of the left ventricle of rats the distribution of cell organelles and their reaction to hypoxia were investigated by electron microscopy. In normal hearts fixed by perfusion with aldehydes, the mean sarcomere length was 2.2 μm. 27% of the longitudinal sectional area was occupied by mitochondria, 55% by myofibrils and 18% by sarcoplasmic reticulum and ground plasm. The mitochondria situated in rows between the fibrils were oval and measured 2.3 times more in length than in width. There was no difference between cells from subendocardial and subepicardial regions. 10 min hypoxia (complete occlusion of the trachea) did not affect the appearance of muscle cells but diminished the number of glycogen granules. After 20 minutes the area occupied by mitochondria was increased by 16%, the mitochondria between the myofibrils were more spherical and only 1.5 times longer than wide. The sarcomeres shortened to 2.0 μm. With hypothermia (25–30°C) hypoxia of 20 minutes duration did not affect the cell structure. Perfusion of the heart by a saline solution, which contained procaine but neither oxygen nor glucose, for 20 minutes prevented shortening of the sarcomeres but not swelling of the mitochondria. 30 minutes after occlusion of the trachea the myofibrils shortened to a sarcomere length of 1.7 μm. After 60 minutes irregularly and excessively contracted myofibrils appeared and some sarcomeres were interrupted at the level of the I-bands. In some of the swollen mitochondria the cristae were widely separated. The increase of the area occupied by mitochondria was 27%. Asphyxia affects heart muscle cells severely with respect to function within 10 min, but morphologically it takes 20 min before a definite effect can be noticed. As to the time after which lack of oxygen is manifested morphologically, our results are consistent with findings in liver cells.
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    Morphology of superficial postnatal cerebral cortex with special reference to synapses (1970)
    Springer
    Cell & tissue research 110 (1970), S. 540-558 
    Details
    ISSN: 1432-0878
    Keywords: Cerebral cortex ; Synapses ; Rat ; Postnatal differentiation ; Morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure of layers I and II of the motor cerebral cortex of rat brain has been studied at birth, 4, 7 and 14 days postnatal and in the adult. Compared with the adult, neonatal rat motor cortex exhibited a large extracellular space which decreases with increasing age. At all stages studied the neurons were seen to contain the organelles usually found in adult neurons. Growth cones were present in decreasing numbers up to 14 days old. Synapses were detectable at birth and there was an obvious increase in their number throughout the postnatal development. At the earliest stages studied there was a lack of specialization characteristic of the adult. Many synapses were either avesicular or relatively so and lacked the high degree of modification of adult pre- and postsynaptic membranes. By 7 days after birth many synapses existed which in all morphological respects resembled those of the adult, and by 14 days, the majority were of the adult type. These findings, particularly with reference to the postnatal development of synapses, have been discussed in relation to the known electrophysiological findings.
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    URL: http://dx.doi.org/10.1007/BF00330103
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    Origine embryonnaire et différenciation sécrétoire des cellules à calcitonine (cellules C) dans la thyroïde foetale du rat (1970)
    Springer
    Cell & tissue research 106 (1970), S. 251-268 
    Details
    ISSN: 1432-0878
    Keywords: C cells ; Thyroid ; Rat ; Ultimobranchial origin ; Differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Résumé Nos observations confirment l'origine ultimobranchiale des cellules C de la thyroïde du rat. L'évolution des corps ultimobranchiaux (C.U.B.) a été étudiée à partir du 16ème jour de gestation, stade où ils fusionnent avec l'ébauche thyroïdienne. Dès le 17ème jour, les premières cellules C se différencient dans le C.U.B. inclus dans la thyroïde. Au 18ème jour, elles sont plus nombreuses et commencent à se disperser dans les cordons thyroïdiens. La migration des cellules C est particulièrement importante au 19ème jour. A partir du 20ème jour, les signes d'activité sécrétoire s'intensifient très nettement. A la fin de la vie foetale, les cellules C sont comparables aux cellules C adultes. La differenciation des cellules parathyroïdiennes précède nettement celle des cellules C.
    Notes: Summary Our observations confirm the ultimobranchial origin of the C cells of the rat thyroid. We studied the development of the ultimobranchial body from the 16th day of pregnancy, when there is fusion with the thyroidian anlage, onwards. As early as the 17th day, the first C cells differentiate in the ultimobranchial body which is included into the thyroid. On the 18th day, they are more numerous and start to scatter throughout the thyroidian cords. The migration of the C cells is especially obvious on the 19th day. From the 20th day onwards, there is marked increase in secretory activity. At the end of the foetal life, the C cells resemble those of the adult. The differentiation of the parathyroid cells significantly precedes that of the C cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335742
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    Fine structure of trypsin-dissociated rat adrenal cells (1970)
    Springer
    Cell & tissue research 107 (1970), S. 447-453 
    Details
    ISSN: 1432-0878
    Keywords: Adrenal cortex ; Rat ; Trypsin-dissociation ; ACTH stimulation ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Electron micrographs of trypsin-dissociated rat adrenal showed predominantly intact rounded cells without internal damage. The population contained cells from the glomerular, intermediary and fascicular zones with cells from the zona fasciculata predominant. The presence or absence of cells from the reticular zone could not be determined. Cells from the medullary zone were absent. The addition of adrenocorticotropic hormone (ACTH) to the cellular suspension for 2 hours produced corticosterone. However, these stimulated cells did not display any significant ultrastructural change.
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    URL: http://dx.doi.org/10.1007/BF00335433
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    On the epithelium of the rat pituitary residual lumen (1970)
    Springer
    Cell & tissue research 108 (1970), S. 487-500 
    Details
    ISSN: 1432-0878
    Keywords: Pituitary gland ; Residual lumen ; Epithelial cells ; Fine structure ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Histology, enzyme histochemistry, and electron microscopy of the epithelium covering the rat pituitary residual lumen was studied. The anterior and posterior epithelium have similar histological and histochemical appearance, although the posterior epithelium shows stronger enzyme reactions for an esterase and many dehydrogenases. Electron microscopic studies reveal that both epithelia form a continuous lining. Anterior epithelium is in immediate contact with the interstitial spaces of the anterior lobe, while the posterior epithelium is separated from the intermediate lobe by a continuous basement lamina. The cytological features of both epithelia are also remarkably similar with scanty rough-surfaced endoplasmic reticulum, inconspicuous Golgi apparatus, round or oval mitochondria, and moderate number of lysosomal bodies. The apical surface of these cells is covered by microvilli and in some, especially posterior epithelial cells, by numerous cilia. Anterior epithelial cells and the apical portions of the posterior epithelial cells contain a number of large vacuoles with material possibly related to the colloid within the residual lumen. Electron microscopic findings suggest that both epithelia are possibly active in transfer and/or disposal of the colloid material rather than being secretory themselves. Enzyme histochemical findings support the hypothesis of an active role of these cells in metabolic processes related to phagocytosis. Based on these observations the colloid seems to be the product of the anterior lobe function.
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    Quantitative studies of postnatal changes in synapses in rat superficial motor cerebral cortex (1970)
    Springer
    Cell & tissue research 110 (1970), S. 559-568 
    Details
    ISSN: 1432-0878
    Keywords: Cerebral cortex ; Rat ; Synapses ; Postnatal ; Quantitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Quantitation of synapses at different postnatal ages has been undertaken in the cerebral cortex of the rat. In this study axial ratios of presynaptic bags, proportion of cortex occupied by presynaptic bags and numbers of synapses per unit volume of cortex have been estimated. Observations on synaptic vesicle packing densities have also been made. Synaptic bags become increasingly spherical up to 7 days of age and become more elongated thereafter. The proportion of cortex occupied by presynaptic bags increases rapidly up to 7 days of age and then at a decelerated rate up to maturity. The number of synapses per unit volume increases slowly over the first four days after which there is a rapid increase to 14 days, followed by a decelerated rate. The average presynaptic bag shows marked changes in volume with increasing age which indicate the probability of two stages of synaptic development. This two stage development is further reflected in the estimates on vesicle packing densities. The implications of the results are discussed in relationship to changes in functional activity of the cortex during postnatal development.
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    URL: http://dx.doi.org/10.1007/BF00330104
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    Elektronenmikroskopische Untersuchungen zur Inselregeneration im Rattenpankreas nach subtotaler Pankreatektomie (1970)
    Springer
    Cell & tissue research 110 (1970), S. 569-587 
    Details
    ISSN: 1432-0878
    Keywords: Subtotal Pancreatectomy ; Rat ; Islet Regeneration ; Excretory Duct System
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Männliche Ratten wurden bei einem Gewicht von 80–100 g subtotal pankreatektomiert (5% Rest) und zu verschiedenen Zeitpunkten nach der Operation abgetötet. Bei diesen wie bei unbehandelten Kontrolltieren wurde die Neubildung von Inselgewebe aus dem exkretorischen Gangsystem elektronenmikroskopisch untersucht. — Es konnte gezeigt werden, daß die Inselneubildung von Gangzellen ausgeht, welche ein auffallend helles Zytoplasma besitzen und samt ihren Kernen größer und abgerundeter sind als ihre Nachbarzellen. Diese Zellen wandern vom Lumen ab, wobei die entstehende Lücke zum Lumen zu jeweils durch eine seitliche Ausdehnung des Zytoplasmas benachbarter Gangzellen geschlossen wird. Die abgewanderten hellen Zellen, die mit den lichtmikroskopisch beschriebenen „trüben Zellen“ identisch sein dürften, haben die Fähigkeit, sich zu Alpha-oder Beta-Zellen zu differenzieren. Dabei werden sie größer und das Zytoplasma dunkler. Sie behalten aber gleichzeitig einige Besonderheiten, die auf ihre Herkunft hinweisen. Die Regeneration des Inselgewebes, die vorwiegend von den zentroacinären Zellen ausgeht, setzt bald nach der Operation stark ein, schwächt sich dann aber kontinuierlich ab. In den immer ineffektiver werdenden Regenerationsvorgang werden zunehmend größere Gangabschnitte einbezogen. Die weitgehende Erschöpfung der Regenerationsfähigkeit fällt mit dem Auftreten eines manifesten Diabetes zwischen dem 40. und 60. Tag p.op. zusammen.
    Notes: Summary Male rats were subtotally pancreatectomized at a weight of 80–100 g according to the method of Foglia (5% of the total pancreas remaining). The animals were killed at different intervals after. In these rats, as well as in healthy controls, the new formation of islets out of the excretory duct system was studied by electron microscopy. Obviously the new formation of islets takes origin from certain cells of the ductular system which show a light cytoplasm and are larger and rounder than their neighbouring cells. The latter goes for their nuclei, too, even to a larger degree. These light cells migrate away from the ductular lumen and the gaps resulting from this are closed by long and thin processes of the cytoplasm of their neighbouring duct cells coming in contact with each other. The cells having migrated away seem to have an ability to differentiate into alphaor beta-cells. Most probably they are identical with the “trübe Zellen” described by light-microscopists. The higher the degree of differentiation in these cells is, the darker becomes their cytoplasm. But they still keep for some time morphological aspects indicating their origin from ductular cells. An intense regeneration of islet tissue starts soon after the operation from the centroacinar cells but it decreases continuously after. As the process of islet regeneration becomes more and more ineffective, an increasing number of larger excretory ducts are involved in it. The exhaustion of the ability for regeneration is correlated exactly in time with the onset of a manifest diabetes between the 40 th and 60 th day after operation.
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    Electron microscopic studies on the oocyte maturation in cultures of juvenile rat ovaries (1970)
    Springer
    Cell & tissue research 111 (1970), S. 364-378 
    Details
    ISSN: 1432-0878
    Keywords: Rat ; Oocyte maturation ; in vitro studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary After cultivation in a modified Trowell-system (organ ciilture) oocytes of 12- to 40-day-old rats were studied under the light and electron microscope. The cultivation period was 72 hrs. Egg cells from primary and early secondary follicles which are characterized by the lack of a zona pellucida and by one or at most two very large Golgi's complexes located near the nucleus do not show any alterations. The other egg cells are characterized by membrane packages which can otherwise only be observed in mature egg cells right before or after the ovulation. Meiotic processes or the formation of polar bodies are only seldom to be seen. These egg cells are surrounded by a thick zona pellucida. From these findings the following conclusions can be drawn: 1. In organ cultures meiotic processes are prevented by the inhibitory influence of follicle cells (Foote and Thibault, 1969). 2. A cytoplasmic maturation proceeds independently. 3. In-vivo an inhibitory factor influences the cytoplasmic maturation. This inhibition is not observed in the organ culture. Thus we can be sure that it develops outside the ovary. 4. The synthesis of the zona pellucida continues in-vitro.
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    URL: http://dx.doi.org/10.1007/BF00342488
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    Cellular localization of 3H-oestradiol in the hypothalamus (1970)
    Springer
    Cell & tissue research 104 (1970), S. 572-581 
    Details
    ISSN: 1432-0878
    Keywords: Hypothalamus ; Rat ; Cellular Localization of 3H-Oestradiol ; Autoradiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The hypothalamus of male and female rats, given 0.3 μg/100 g body weight of 6.7-3H-oestradiol-17β and killed 1 hour after the injection, was examined by autoradiography in order to 1) localize the areas and the cells involved in the uptake of the hormone, and 2) study the intracellular localization of the labelled material. Only nerve cells contained radioactive material while glial and ependymal cells were not significantly labelled. In the anterior hypothalamus, labelled nerve cells were concentrated in areas corresponding to nucleus preopticus medialis and nucleus preopticus, pars suprachiasmatica. The nucleus supraopticus was unlabelled. In the medial basal hypothalamus, neurons corresponding to the nucleus arcuatus and the lateral part of the nucleus ventromedialis showed marked labelling. No significant labelling was observed in the nucleus paraventricularis, pars magnocellularis. Although the individual nerve cells varied in their extent of labelling, the major proportion of the silver grains were consistently concentrated over the nuclei. Castration was not found to influence the results. The findings were essentially the same in male and female rats and appear to suggest that oestradiol exerts a direct effect on nerve cells in certain hypothalamic areas.
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    URL: http://dx.doi.org/10.1007/BF00335379
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    The uptake of 3H-oestradiol by the anterior hypophysis and hypothalamus of male and female rats (1970)
    Springer
    Cell & tissue research 104 (1970), S. 582-596 
    Details
    ISSN: 1432-0878
    Keywords: Anterior hypophysis ; Hypothalamus ; Rat ; Uptake of 3H-Oestradiol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The anterior hypophysis and hypothalamus of male and female rats given 3H-oestradiol were examined with regard to 1) the kinetics of the uptake of the radioactive material, 2) the chemical nature of the labelled material, and 3) the influence of non-labelled oestradiol-17β, oestradiol-17α and testosterone on the uptake of 3H-oestradiol. The anterior hypophysis was found to concentrate and retain oestradiol in basically the same manner in male and female rats. The pattern of the uptake was similar to that of the uterus and vagina, with a concentration peak 2 hours after the injection. Non-target tissues such as cerebral cortex, liver and blood attained their maximum uptake already 15 minutes after the injection. Thereafter the concentration gradually decreased. The ratio between the concentration of labelled material in the anterior hypophysis and brain cortex gradually increased until a peak was reached at 8 hours in both sexes. In the female, the concentration of labelled material in the anterior hypophysis was then 106.3 times greater than in the brain cortex, while in the male the ratio was 63.2. In the hypothalamus the uptake followed a pattern similar to that of the brain cortex. However, in the former the concentration of labelled material was consistently greater than in the latter. At maximum uptake, registered 4 hours after the injection, the concentration was about two times greater in the hypothalamus than in the cerebral cortex. The neurohypophysis contained, on an average, 1/6 of the amount of radioactive material registered in the anterior lobe one hour after the injection, but it was about two times greater than in the brain cortex. Isolation and identification of the radioactive material in the anterior hypophysis and hypothalamus showed that in both sexes nearly all of it was chemically unchanged oestradiol. Graded doses of non-labelled oestradiol-17β were found to decrease the uptake of 3H-oestradiol in the anterior hypophysis and hypothalamus almost linearly, while the concentration of labelled material in the brain was unaltered. Oestradiol-17α and testosterone were without significant effect on both the pituitary and hypothalamic accumulation of 3H-oestradiol. Therefore, a limited number of binding sites, with a high degree of specificity for oestradiol, appear to exist in both tissues. The results were essentially the same in male and female rats.
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    Ultrastructural changes in the median eminence of the rat following deafferentation of the basal hypothalamus (1970)
    Springer
    Cell & tissue research 105 (1970), S. 1-32 
    Details
    ISSN: 1432-0878
    Keywords: Median eminence ; Rat ; Deafferentation ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary This report concerns a light and electron microscopic investigation of the median eminence and dorsal infundibular stem of the rat following surgical isolation (deafferentation). Using a modification of the Halász technique, the basal hypothalamus, including the arcuate nucleus and median eminence were surgically isolated from surrounding structures. Special attention was directed to the contact (external) zone of the median eminence and rostral infundibulum where tuberohypophyseal axons as well as ependymal cell processes abut upon the abluminal basement membrane of the portal perivascular space. The results of this study to date suggest that 9, 20, and 40 days following surgical isolation, there is a distinct increase in the population of tuberohypophyseal dense core vesicles. It is suggested that deafferentation abolishes inhibitory and excitatory input that serves to modify the cellular dynamics of tuberohypophyseal neurosecretory elements. Comments are also made on the presence of cistern-like structures in the lateral median eminence; the presence of vesicle-like inclusions in terminal ependymal processes is discussed in relationship to the role that ependyma may play in linking the third ventricle with the adenohypophysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00340562
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  • 83
    Electronic Resource
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    Cellular localization of 3H-oestradiol in the hypophysis (1970)
    Springer
    Cell & tissue research 104 (1970), S. 597-614 
    Details
    ISSN: 1432-0878
    Keywords: Hypophysis ; Rat ; Localization of 3H-Oestradiol ; Autoradiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pituitaries of male and female rats given 0.3 μg of 6.7-3H-oestradiol-17β per 100 g body weight were examined by autoradiography in order to 1) identify the cells responsible for the uptake of the hormone, 2) determine the intracellular distribution of the hormone and quantify the proportions localized within the cytoplasm and nucleus by silver grain counting, and 3) see if sex differences existed in the cellular and intracellular distribution of the hormone. The animals were killed at intervals varying from 1 minute to 8 hours following intravenous or intramuscular injection. A large proportion of pituitary cells having the morphologic characteristics of acidophils, basophils and chromophobes contained radioactive material. Castration cells and acidophils of gonadectomized and lactating rats showed marked labelling. In male and female rats killed 10 minutes after intravenous injection, 84.4 and 83.6 per cent of the cells were labelled. One hour after intramuscular injection, 86.6 and 76.1 per cent of the cells were labelled in males and females, respectively. Thus, a small proportion of the cells remained unlabelled. Labelled cells showed silver grains both in the cytoplasm and over the cell nuclei, but the major proportion of the radioactive material was invariably associated with the cell nuclei in all cell types and at all time intervals. About 65 per cent of the radioactive material was associated with the cell nuclei in animals killed five minutes or one hour after intravenous or intramuscular injection of the hormone. The silver grains appeared to be randomly distributed in both the cytoplasm and over the cell nuclei. In the intermediate lobe and the neurohypophysis, only sparse labelling with random distribution was observed. At the border between the intermediate lobe and the neurohypophysis, labelling of single cells or clusters of cells similar to those in the adenohypophysis was found. The results, which were essentially the same in male and female rats, appear to indicate a direct effect of oestradiol at the pituitary level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335381
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  • 84
    Electronic Resource
    Electronic Resource
    Monoamine fluorescence in the median eminence of foetal, neonatal and adult rats (1970)
    Springer
    Cell & tissue research 104 (1970), S. 541-556 
    Details
    ISSN: 1432-0878
    Keywords: Median eminence ; Rat ; Monoamine fluorescence ; Output of pars distalis hormones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution of monoamines in the median eminence of foetal, neonatal and adult rats has been studied with the Falck-Hillarp fluorescence histochemical technique in preparations in which the hypothalamus and pituitary gland were in continuity. In adult rats monoamine fluorescence is present throughout the median eminence, including the anatomical stem. In foetal rats a few sagittally-directed varicose fluorescent fibres are seen in the median eminence. In neonatal rats palisade layer fluorescence in appreciable amounts is first seen on the fourth day in the region of the anatomical stem. By the eighth day it has spread throughout the palisade layer of the entire median eminence, and by the end of the third week it has attained adult intensity. The appearance of monoamines in the median eminence, the development of a functional hypophysial portal system, and a changing pattern of development of function in both the hypothalamo-pituitary-adrenal and hypothalamo-pituitary-thyroid axes thus all appear to be contemporaneous events. It is suggested that the monoamines of the median eminence represent part of a neural system influencing the output of pars distalis hormones, in particular of ACTH and TSH secretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335377
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  • 85
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    Altersabhängige Veränderungen im histochemischen Reaktionsmuster des Thymus bei Wistar-Ratten (1970)
    Springer
    Cell & tissue research 104 (1970), S. 138-148 
    Details
    ISSN: 1432-0878
    Keywords: Thymus ; Rat ; Involution ; Histochemical pattern
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Makrophagen und entodermale Retikulumzellen samt Ausläufern lassen sich im Thymus der Wistar-Ratte durch den histochemischen Nachweis der sauren Phosphatase und der unspezifischen Esterase selektiv darstellen, während die Lymphozyten nicht reagieren. Häufigkeit und Verteilung der Retikulumzellen und Makrophagen lassen altersabhängige Unterschiede erkennen: Auf Kosten der Retikulumzellen nimmt die Zahl der Makrophagen mit fortschreitendem Lebensalter zu. Bei geschlechtsreifen Tieren bilden sie einen Wall an der Mark-Rinden-Grenze. Die Bedeutung der sauren Phosphatase in entodermalen Retikulumzellen wird unter der Annahme diskutiert, daß es sich um lysosomengebundenes Ferment handelt. Lysosomen sind im involvierenden Thymus wahrscheinlich an autolytischen oder phagozytotischen Prozessen beteiligt. Es stellt sich die Frage, ob Lysosomen in entodermalen Retikulumzellen des Thymus neugeborener Tiere in die Abgabe einer humoral wirksamen Substanz eingreifen können.
    Notes: Summary Macrophages and entodermal reticulum cells in the thymus of Wistar rats contrast by their rich contents of acid phosphatase and unspecific esterase activity with the negativ reacting lymphocytes. Frequency and distribution of the cells vary according to different stages of age: at cost of the entodermal reticular cells the number of macrophages increases with progressive age. In sexually mature animals they form a typical layer at the corticomedullary junction. The functional meaning of acid phosphatase in the entodermal reticulum cells is discussed under the assumption that this enzyme is lysosomebound. In the involuting thymus lysosomes are involved in autolytic or phagocytic processes. The question arises wether lysosomes in entodermal reticulum cells in the thymus of newborn animals can take part in the control of an humoral function of the thymus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00340055
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  • 86
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    Electronic Resource
    Masthead (1970)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970) 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620020101
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  • 87
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    Editorial (1970)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 3-3 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620020103
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  • 88
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    Announcement (1970)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 2-2 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620020102
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  • 89
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    A frontal solution program for finite element analysis (1970)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 5-32 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The program given here assembles and solves symmetric positive-definite equations as met in finite element applications. The technique is more involved than the standard band-matrix algorithms, but it is more efficient in the important case when two-dimensional or three-dimensional elements have other than corner nodes. Artifices are included to improve efficiency when there are many right hand sides, as in automated design. The organization of the program is described with reference to diagrams, full notation, specimen input data and supplementary comments on the ASA FORTRAN print-out.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620020104
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  • 90
    Electronic Resource
    Electronic Resource
    Automatic design of guyed masts subject to deflection constraints (1970)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 33-43 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the design of a guyed mast the design specification often imposes limits on the allowable deflection of the mast under wind and other lateral loads. While the deflected form of a mast depends on many different design parameters, the guy erection tensions form one of the simplest means of controlling the lateral displacements. The paper describes a procedure for calculating these tensions in the case of a mast required to have a specified set of displacements under a given set of lateral loads. It also discusses the case where specified deflections are not to be exceeded under a number of different loading conditions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620020105
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  • 91
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    Electronic Resource
    Thermomechanical analysis of viscoelastic solids (1970)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 45-59 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper is concerned with the development of a computational algorithm for the solution of the uncoupled, quasi-static boundary value problem for a linear viscoelastic solid undergoing thermal and mechanical deformation. The method evolves from a finite element discretization of a stationary value problem, leading to the solution of a system of linear integral equations determining the motion of the solid. An illustrative example is included.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620020106
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  • 92
    Electronic Resource
    Electronic Resource
    Transient field problems: Two-dimensional and three-dimensional analysis by isoparametric finite elements (1970)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 61-71 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The transient field problem of the type encountered in heat conduction problems is formulated in terms of the finite element process using the Galerkin approach. Curved two-dimensional and three-dimensional, isoparametric elements are used in a time-stepping solution and their advantages illustrated by means of several examples.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620020107
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  • 93
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    New displacement hybrid finite element models for solid continuaThis work was supported by the Office of Scientific Research of the United States Air Force under Contract No. F44620-67-C-0019.The author wishes to express his appreciation to Professor T. H. H. Pian for his useful comments and suggestions. (1970)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 73-83 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The proposed finite element model is based on separate assumptions of interior and interelement displacements and on the assumed boundary tractions of each individual element. The associated variational functional for this model is presented. This method has the same merits of the assumed stress method (References 3 and 4) in that a compatible displacement function at the interelement boundary can be easily constructed, while it can easily be used for shells with distributed loads.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620020108
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  • 94
    Electronic Resource
    Electronic Resource
    A direct numerical method for the solution of field problems (1970)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 117-131 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A numerical method for the analysis of field problems is described. The algorithm is based upon the generalized Betti-Maxwell theorem. Using a set of known solutions to problems with similar boundary conditions produces a set of ‘integral’ equations for the required solution. Using any convenient numerical integration formula reduces the problem to the solution of a set of simultaneous algebraic equations. The accuracy of the solution depends upon the accuracy of the integration formula as applied to the problem under consideration and is independent of the known auxiliary solutions. The method is described in detail as applied to harmonic problems.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620020111
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  • 95
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    A finite element application of the modified Rayleigh-Ritz methodCrown Copyright, reproduced with the permission of the Controller, Her Majesty's Stationery Office. (1970)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 85-98 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Considerable attention has been devoted in the literature on numerical methods towards securing energy convergence of solutions for, say, linearly elastic plate bending problems. Although energy convergence is necessary it by no means follows that the derived bending moments and shearing forces converge uniformly at a given point and it is this kind of feature which the engineer is really seeking.This question is examined in the context of a problem which is of particular interest to the civil engineering field and concerns the bending of a square plate under uniformly distributed load; the plate has simply supported edges and contains a central square hole with free edges. The solution to this multiply connected and mixed boundary value problem is obtained through a recently developed modification to the Rayleigh-Ritz method which has very general application and renders the solution mathematically valid up to the internal corner points where the bending moments are singular. Use is made of triangular equilibrium finite elements in conjunction with continuous eigenfunctions. Although it is already known that the order (i.e. the eigenvalue) of the singularity at the internal corners is available by inspection, it is an interesting feature of the present solution that a good approximation to the amplitude is also obtained by an inspection of the finite element results.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620020109
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  • 96
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    Convergence studies of eigenvalue solutions using two finite plate bending elements (1970)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 99-116 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The convergence rates of eigenvalue solutions using two finite plate bending elements are studied. The elements considered are the well-known 12 degree of freedom, non-conforming rectangular element and the 16 degree of freedom, conforming rectangular element. Three problems are analysed, a square plate simply supported on two opposite sides with the other two sides clamped, simply supported, or free. Closed form, finite element solutions for these problems are obtained by using shifting E-operators.With few exceptions, eigenvalue solutions found with the non-conforming element converge from below the exact answers at an asymptotic rate of n-2, where n is the number of elements on a side. However, since the array size needed for such convergence is very large, little can be said about the convergence rates for practical arrays. The conforming element solutions converge from above at an asymptotic rate of n-4. A comparison of the errors involved in using these two elements shows that the conforming element is far superior to the non-conforming element.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620020110
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  • 97
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    Letters to editor (1970)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 145-146 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620020113
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  • 98
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    Masthead (1970)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970) 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620020201
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  • 99
    Electronic Resource
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    Replies to letters to editor (1970)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 146-147 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620020114
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  • 100
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    Two-dimensional automatic mesh generation for structural analysis (1970)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 133-144 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents a labour-saving method of discretizing irregular and inhomogeneous two-dimensional continua into triangular elements. The method uses a magnetic pen to record node point data and a computer program to generate element data. This technique eliminates the tedium in the manual generation of data and the delay due to mistakes which would otherwise arise frequently for a complex mesh.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620020112
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