Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 2005-2009  (51)
  • 1980-1984  (1,671)
  • 1955-1959
  • 1915-1919  (117)
  • 1890-1899  (27)
  • 2006  (51)
  • 1984  (1,671)
  • 1919  (117)
  • 1891  (27)
  • Life and Medical Sciences  (1,307)
  • Biochemistry and Biotechnology  (408)
  • Ultrastructure  (102)
  • ddc:000
Source
Material
Years
  • 2005-2009  (51)
  • 1980-1984  (1,671)
  • 1955-1959
  • 1915-1919  (117)
  • 1890-1899  (27)
Year
Keywords
Language
  • 1
    facet.materialart.
    Unknown
    Jahresbericht 2005 (2006)
    Details
    Publication Date: 2019-10-24
    Keywords: ddc:000
    Language: German
    Type: annualzib , doc-type:report
    Format: application/pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 2
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 3
    facet.materialart.
    Unknown
    A Complex Mathematical Model of the Human Menstrual Cycle (2006)
    Details
    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
    Format: application/pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 4
    facet.materialart.
    Unknown
    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
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 5
    facet.materialart.
    Unknown
    Nash Equilibria in Online Sequential Routing Games (2006)
    Details
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 6
    facet.materialart.
    Unknown
    Adaptive, Fast and Oblivious Convolution in Evolution Equations with Memory (2006)
    Details
    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
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 7
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 8
    facet.materialart.
    Unknown
    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
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 9
    facet.materialart.
    Unknown
    Orbitopal Fixing (2006)
    Details
    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
    Format: application/pdf
    Format: application/postscript
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 10
    facet.materialart.
    Unknown
    Approximability of Unsplittable Shortest Path Routing Problems (2006)
    Details
    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
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 11
    facet.materialart.
    Unknown
    Availability and Cost Based Evaluation of Demand-wise Shared Protection (2006)
    Details
    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
    Format: application/pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 12
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 13
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 14
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 15
    facet.materialart.
    Unknown
    Mathematik für den Volkssport (2006)
    Details
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 16
    facet.materialart.
    Unknown
    Mathematical Methods for Physical Layout of Printed Circuit Boards: An Overview (2006)
    Details
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 17
    facet.materialart.
    Unknown
    Competitive Online Multicommodity Routing (2006)
    Details
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 18
    facet.materialart.
    Unknown
    The extreme points of QSTAB(G) and its implications (2006)
    Details
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 19
    facet.materialart.
    Unknown
    On exact algorithms for treewidth (2006)
    Details
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 20
    facet.materialart.
    Unknown
    Coarse Grained Molecular Kinetics (2006)
    Details
    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
    Format: application/pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 21
    facet.materialart.
    Unknown
    RSWK/SWD und Faceted Browsing: neue Möglichkeiten einer inhaltlich-intuitiven Navigation (2006)
    Details
    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
    Format: application/pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 22
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 23
    facet.materialart.
    Unknown
    Primal Heuristics for Mixed Integer Programs (2006)
    Details
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 24
    facet.materialart.
    Unknown
    A cartesian grid finite volume method for the solution of the Poisson equation with variable coefficients and embedded interfaces (2006)
    Details
    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
    Format: application/pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 25
    facet.materialart.
    Unknown
    Efficient Sampling of the Stationary Distribution of Metastable Dynamical Systems (2006)
    Details
    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
    Format: application/pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 26
    facet.materialart.
    Unknown
    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
    Type: reportzib , doc-type:preprint
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 27
    facet.materialart.
    Unknown
    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
    Type: reportzib , doc-type:preprint
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 28
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 29
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 30
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 31
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 32
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 33
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 34
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 35
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 36
    facet.materialart.
    Unknown
    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
    Type: reportzib , doc-type:preprint
    Format: application/pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 37
    facet.materialart.
    Unknown
    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
    Type: reportzib , doc-type:preprint
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 38
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 39
    facet.materialart.
    Unknown
    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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 40
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 41
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 42
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 43
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 44
    facet.materialart.
    Unknown
    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
    Type: reportzib , doc-type:preprint
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 45
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 46
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 47
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 48
    facet.materialart.
    Unknown
    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
    Type: reportzib , doc-type:preprint
    Format: application/pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 49
    facet.materialart.
    Unknown
    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
    Type: reportzib , doc-type:preprint
    Format: application/pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 50
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 51
    facet.materialart.
    Unknown
    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
    Type: reportzib , doc-type:preprint
    Format: application/pdf
    Format: application/postscript
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
  • 52
    Electronic Resource
    Electronic Resource
    Glycerol effects on the transport of macromolecules in the lateral cochlear wall (1984)
    Springer
    European archives of oto-rhino-laryngology and head & neck 239 (1984), S. 49-59 
    Details
    ISSN: 1434-4726
    Keywords: Glycerol ; Inner ear ; Ultrastructure ; Cellular and paracellular transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect has been studied of intravenously administered glycerol on paracellular and cellular transport of macromolecular HRP tracer in the lateral cochlear wall. The findings indicate osmotically induced diffusion phenomena by the opening of shunt pathways through junctional complexes in the stria vascularis. Vesicular transport is accelerated, direction of transport however is not affected by the changed osmolality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00454262
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 53
    Electronic Resource
    Electronic Resource
    Esthesioneuroblastoma: Ultrastructural, immunohistological and biochemical investigation of one case (1984)
    Springer
    European archives of oto-rhino-laryngology and head & neck 239 (1984), S. 133-144 
    Details
    ISSN: 1434-4726
    Keywords: Esthesioneuroblastoma ; Intermediate filaments ; Secretory granules ; Ultrastructure ; Immunohistology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A case of esthesioneuroblastoma, the pathological diagnosis of which almost always causes great difficulties, was investigated ultrastructurally, biochemically, and immunohistologically, using antibodies against the five known types of intermediate filaments [keratin, vimentin, desmin, glial fibrillary acidic protein (GFAP) and neurofilaments]. The tumour cells did not react with antibodies against any of the five intermediate filament proteins. Ultrastructural investigations showed dense cored secretory granules in the cytoplasm and cell processes. Thus, immunohistology offers by “exclusion” a differential diagnosis to avoid often misdiagnosed tumours (undifferentiated carcinomas, embryonal rhabdomyosarcomas, and malignant lymphomas), since carcinomas react with antikeratin, embryonal rhabdomyosarcomas with antibodies to desmin and malignant lymphomas show immunofluorescence with antibodies to vimentin. The biological behaviour (age distribution, tendency to metastasize), the normal values of biochemical parameters, homovanillic acid and vanilmandelic acid (HVA, VMA), and the absence of neurofilaments distinguish this type of tumour from the peripheral sympathetic neuroblastoma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00463554
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 54
    Electronic Resource
    Electronic Resource
    Atypical germ cells of the testis (1984)
    Springer
    Virchows Archiv 402 (1984), S. 439-450 
    Details
    ISSN: 1432-2307
    Keywords: Atypical germ cells ; Carcinoma in situ of the testis ; Normal germ cells ; Ultrastructure ; Differential diagnosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary It is uncertain whether the so called intratubular atypical germ cells (carcinoma in situ cells) demonstrable in the testicular tissue around different germ cell tumors and in testicular biopsies of patients with impaired fertility are identical with regard to their morphology and further development. Thus atypical germ cells of 18 patients with testicular germ cell tumors and of 3 patients with atypical germ cells in testicular biopsies without tumor were studied by electron microscopy and/or by immunohistochemistry. The atypical germ cells show characteristic alterations distinguishing them from normal germ cells, especially spermatogonia. However, there are no differences between atypical germ cells in the above mentioned groups. Immunohistochemical reactions are negative with anti-alpha-fetoprotein and anti-beta-human-chorionic-gonadotropin, but 6 of the 15 cases are positive with antiferritin. However, this positive reaction occurs in cases in different diagnostic groups. Atypical germ cells of the different groups cannot be distinguished by electron microscopy or immunohistochemical methods, but further investigations vestigations, including cell cultures, may provide more information.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00734640
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 55
    Electronic Resource
    Electronic Resource
    Ultrastructural aspects of the histogenesis of diffuse and localized mesothelioma (1984)
    Springer
    Virchows Archiv 402 (1984), S. 373-388 
    Details
    ISSN: 1432-2307
    Keywords: Mesothelioma ; Histogenesis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary During an ultrastructural review of 30 diffuse and 10 localized mesotheliomas, it was apparent that some micrographs showed various stages in the developmental processes involved in the formation of histological patterns in diffuse mesotheliomas and a histogenetic link between diffuse and localized mesotheliomas. Cells in the stromal or sarcomatous regions of diffuse mesothelioma often show varying degrees of mesothelial differentiation and a gradual transition to cells with typical mesothelial characteristics that organize into structures recapitulating the surface layer of serosal membranes. Tumor cells in localized mesotheliomas had many similarities to the “stromal” cells in the diffuse counterpart including intercellular junctions, rare microvilli and occasional foci of basal lamina. It is postulated that diffuse and localized mesotheliomas share a common histogenetic origin as a result of neoplastic induction of specialized submesothelial cells. In this concept, tumor cells in diffuse mesotheliomas reflect stages in the differentiation and organization of normal serosal membranes and localized mesotheliomas mirror the earliest phases of this process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00734635
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 56
    Electronic Resource
    Electronic Resource
    Carcinoid tumor of the uterine cervix (1984)
    Springer
    Virchows Archiv 402 (1984), S. 331-336 
    Details
    ISSN: 1432-2307
    Keywords: Carcinoid ; Uterine cervix ; Histopathology ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A case of carcinoid tumor of the uterine cervix is reported. The patient was a 76-year-old Japanese woman with a complaint of vaginal bleeding. She was clinically diagnosed as stage IVb carcinoma of the uterine cervix. Light microscopically, the tumor was characterized by formation of solid cell nests and, in limited areas, glandular structures. The tumor cells in solid cells nests showed positive argyrophil reaction but were negative for argentaffin reaction. At the ultrastructural level, the cytoplasm of the tumor cells contain numerous neurosecretory granules, microfilaments and well-developed Golgi complexes. On the bases of histochemical and electron microscopic features of tumor cells, the tumor was diagnosed as carcinoid tumor of the uterine cervix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00695086
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 57
    Electronic Resource
    Electronic Resource
    Ultrastructural analysis of human proximal tubules and cortical interstitium in chronic renal disease (Hydronephrosis) (1984)
    Springer
    Virchows Archiv 402 (1984), S. 209-237 
    Details
    ISSN: 1432-2307
    Keywords: Proximal tubule ; Atrophy ; Cortical interstitium ; Human nephropathy ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A systematic ultrastructural analysis of proximal tubule atrophy and cortical interstitial changes was carried out in human chronic nephropathy. The investigation was based on human hydronephrotic kidneys, which had been surgically removed and subsequently perfusion-fixed for light and electron microscopy. Normal kidney tissue, which was derived from nephrectomy specimens with pathological changes confined to part of the kidney or to the renal pelvis, was used for control material. A slight degree of proximal tubule atrophy was characterized by reduction of mitochondria and basolateral membranes, enlargement of large endocytic vacuoles and increased numbers of lysosomes containing lamellar material. In moderate atrophy these changes were further accentuated, and in addition there was an increasing loss of microvilli and a reduction of endocytic invaginations and small endocytic vacuoles. In severe atrophy all types of organelles were sparse and the architecture of the tubule cells greatly simplified. A distinctive feature of atrophic tubules was the presence in the tubule cells of large bundles of actin-like filaments, which were often associated with outpouchings of basal cell parts and basement membrane. The reduction of mitochondria and basolateral cell membranes and the changes of endocytic vacuoles and lysosomes indicate that proximal tubule atrophy also in early stages may be associated with impairment of tubular transport processes. Comparisons with previous observations in various types of experimentally induced tubule cell degeneration and with the ultrastructure of regenerating proximal tubule cells provide some evidence that degenerative changes as well as imperfect regeneration of tubule cells may contribute to the alterations of ultrastructure in tubular atrophy. It is suggested that changes of the cortical interstitium may be of pathogenic importance for the progression of tubular atrophy by altering the spatial relationships between tubules and capillaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00695077
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 58
    Electronic Resource
    Electronic Resource
    Mammosomatotroph hyperplasia associated with acromegaly and hyperprolactinemia in a patient with the McCune-Albright syndrome (1984)
    Springer
    Virchows Archiv 403 (1984), S. 77-86 
    Details
    ISSN: 1432-2307
    Keywords: Acromegaly ; hyperprolactinemia ; McCune-Albright syndrome ; pathology ; Pituitary ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An 11-year-old girl, with the McCune-Albright syndrome, exhibited fibrous dysplasia of several bones, skin pigmentation, precocious puberty, growth hormone hypersecretion, acromegaly and hyperprolactinemia. Histologic, immunocytologic and ultrastructural investigation of the surgically-removed pituitary showed massive mammosomatotroph hyperplasia. Since no adenoma was found, the abundance of these bihormonal cells, capable of producing both growth hormone and prolactin, was implicated in the causation of growth hormone and prolactin excess. Somatoliberin overproduction and/or somatostatin and dopamine deficiency could not account for the hypophysial abnormality, since changes in secretory rates of these hypothalamic hormones would lead to proliferation of mature somatotrophs and lactotrophs, rather than mammosomatotrophs. In our patient, a congenital hypothalamic malfunction might have been accompanied by hypersecretion of an unidentified releasing factor, resulting in pathologic differentiation of the pituitary and mammosomatotroph hyperplasia. Alternatively, mammosomatotroph hyperplasia may have been due to an inherent genetic or embryonic defect affecting primarily the pituitary. According to this interpretation, the pituitary lesion represented yet another developmental error in the setting of the McCune-Albright syndrome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00689340
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 59
    Electronic Resource
    Electronic Resource
    Ameloblastic fibrosarcoma in the maxilla, malignant transformation of ameloblastic fibroma (1984)
    Springer
    Virchows Archiv 404 (1984), S. 253-263 
    Details
    ISSN: 1432-2307
    Keywords: Ameloblastic fibrosarcoma ; Histogenesis ; Histopathology ; Ultrastructure ; Fatal case
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This report presents a fatal case of ameloblastic fibrosarcoma arising from an ameloblastic fibroma, originating in the maxilla of 19-year-old Japanese male. An analysis of previously reported fatal cases of ameloblastic fibrosarcoma is included. In the course of the disease, the mesenchymal component of ameloblastic fibroma showed a dramatic histopathological transformation into sarcoma following multiple recurrence and the patient died of uncontrollable local infiltration of the cranial base. Although many cases have seemed to show disappearance of the epithelial component as malignant transformation progressed, many benign appearing ameloblastoid epithelial masses were scattered throughout the sarcomatous area even in the fatal stage in the present case. No distant metastases were found at autopsy. During multiple recurrences of the lesion, a little dysplastic dentin which was closely associated with both epithelial and mesenchymal components was found, though it could not be observed in autopsy material. Ultrastructural findings in autopsy material showed that the mesenchymal component consisted of undifferentiated mesenchymal cells, fibroblastic and fibrocytic cells with marked cellular and nuclear pleomorphism and that the epithelial component closely resembled the enamel organ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694891
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 60
    Electronic Resource
    Electronic Resource
    A morphometric study on the ultrastructure of well-differentiated tumours and inflammatory mucosa of the human urinary bladder (1984)
    Springer
    Virchows Archiv 405 (1984), S. 25-39 
    Details
    ISSN: 1432-2307
    Keywords: Morphometry ; Human bladder tumour ; Human chronic cystitis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Transmission (TEM) and scanning electron microscopic (SEM) observations were performed on well-differentiated tumours and chronic cystitis in the human urinary bladder. SEM showed that the pleomorphic microvilli were present not only on the luminal surface of the tumour but also on the surface of inflammatory mucosa. The ultrastructure of six tumours and 5 cases of chronic cystitis was evaluated morphometrically. Bladder tumour and inflammatory mucosa were divided into several layers, namely outermost cells (S), subsurface cells just beneath these (S1), subsurface cells of 2 or 3 layers below (S23), intermediate cells of 2 or 3 layers above the basal cells (123), intermediate cells just above the basal cells (I1) and basal cells (Ba). Areas of nucleus, cytoplasm and cytoplasmic organelles, numbers of nucleoli, nuclear bodies, mitochondria and lysosomes together with irregularity of the cell and nucleus were estimated according to the methods of Weibel. A multi-variate analysis of variance on these variables showed that the above subdivision of layers was necessary for the comparison of tumour and inflammation. Discriminant analysis showed various differences between tumour and inflammatory mucosa. The results indicated that the Ba layer is the most effective site for differentiating the tumour from inflammation. Ba cells with large and irregular cytoplasm with an enlarged Golgi area, accompanied by many vacuolar structures, may be indicative of tumour rather than inflammation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694923
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 61
    Electronic Resource
    Electronic Resource
    Neurogenic sarcomas in patients with neurofibromatosis (von Recklinghausen's disease) (1984)
    Springer
    Virchows Archiv 403 (1984), S. 361-376 
    Details
    ISSN: 1432-2307
    Keywords: Neurofibrosarcomas ; Neurogenic sarcomas ; Von Recklinghausen's disease ; Malignant schwannomas ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Thirteen soft tissue neurogenic sarcomas from twelve patients with neurofibromatosis (Von Recklinghausen's disease) were ultrastructurally examined. Electron microscopic studies revealed a wide spectrum of morphological manifestations varying from schwannian to fibroblastic, histiocytic, fibrohistiocytic and relatively undifferentiated cellular proliferations. A similar variation on light microscopic appearances has been previously reported in these neurogenic sarcomas. Neurogenic sarcomas occurring in patients with neurofibromatosis (Von Recklinghausen's disease), represent a heterogenous group of neoplasms with various patterns of differentiation identified ultrastructurally. The morphologic expressions of these neurogenic neoplasms can be conceptualized as a disorderly growth of the various peripheral nerve cellular components, or, as has been previously suggested, as a result of the multipotential nature and metaplastic ability of Schwann cells. S-100 protein immunohistochemistry was only positive in those neoplasms ultrastructurally proven to represent schwannian cellular proliferations. This study serves to document the range of fine structure that may be found in neurogenic sarcomas, to correlate the ultrastructural findings with the light microscopic appearance of these tumors, to determine the specificity of the electron microscopic findings, and immunohistochemistry for S-100 protein and assess their possible value in differential diagnosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00737286
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 62
    Electronic Resource
    Electronic Resource
    Ultrastructural observations on the histogenesis of localized fibrous tumours of the pleura (benign mesothehoma) (1984)
    Springer
    Virchows Archiv 403 (1984), S. 413-424 
    Details
    ISSN: 1432-2307
    Keywords: Localized fibrous tumour of the pleura ; Benign mesothelioma ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Five localized fibrous tumours of the pleura (benign mesothelioma) were studied ultrastructurally in order to elucidate their histogenesis. The histological subtypes of this benign fibrous lesion of the visceral pleura, i.e. the cellular, the collagenous, and the hyaline, were separately analysed. The tumours are composed of undifferentiated mesenchymal cells, intermediate and differentiated fibroblasts as well as collagenous interstitial tissue. The varying distribution of these cell elements account for the various histological subtypes. Morphological similarities between the mesenchymal tumour cells and the superficial mesothelial cells, which are always separated from the true tumour tissue by an intact basement membrane, were not observed. The different cellular elements can be regarded as parts of a continuous spectrum of cytodifferentiation, in which the mature fibroblasts are derived via intermediate forms from the undifferentiated cells. It is concluded that the localized fibrous tumours of the pleura arise from immature mesenchymal stem cells, which seems to be normally found in the submesothelial layer of the visceral pleura.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00737290
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 63
    Electronic Resource
    Electronic Resource
    Herpes oesophagitis (1984)
    Springer
    Virchows Archiv 404 (1984), S. 177-185 
    Details
    ISSN: 1432-2307
    Keywords: Oesophagitis ; Herpetic cell change ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ultra-thin sections obtained from routine biopsy specimens and cytological smears of 3 cases, together with one autopsy case suggestive of herpes oesophagitis, clearly demonstrate herpes viruses. The infected epithelial cells reveal different stages of virus replication and propagation. Cowdry A type inclusion bodies, however, representing early alterations in the course of infection are less frequent. Ground-glass looking nuclei of light microscopical balloon cells and infected multinuclear giant cells of epithelial origin are characteristic changes of the late ulcerative stage of herpes oesophagitis usually seen at the time of detection. These typical virus induced cell changes are mostly to be found at the ulcers edge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00704062
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 64
    Electronic Resource
    Electronic Resource
    Palmar fibromatosis (Dupuytren's contracture) (1984)
    Springer
    Virchows Archiv 405 (1984), S. 41-53 
    Details
    ISSN: 1432-2307
    Keywords: Fibromatosis ; Dupuytren's contracture ; Myofibroblast ; Ultrastructure ; Histochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Forty three cases of palmar fibromatosis were studied by light and electron microscopy, enzyme histochemistry, and ultrastructural immunohistochemistry. By electron microscopy most of the cells composing the nodules in both the proliferative and the involutional stages were identical to myofibroblasts. The myofibroblasts in the involutional nodules often possessed microfilament aggregates probably representing contraction of micro(actin)fllaments in the cytoplasm. The proliferative nodules revealed small perivascular haemorrhages and haemosiderin deposits accompanied by accumulation of macrophages and some lymphocytes; these inflammatory cells possibly secrete a certain growth factor inducing proliferation of genetically abnormal fibroblasts and myofibroblasts. Diaminopeptidase IV was detected in myofibroblasts and fibroblasts by enzyme histochemistry and ultrastructural immunohistochemistry; the enzyme may play a role in the metabolism of intercellular substances. Some perivascular mesenchymal cells, interpreted as variants of myofibroblasts, had moderate activity of alkaline phosphatase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694924
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 65
    Electronic Resource
    Electronic Resource
    Effect of gossypol on bull spermatozoa in vitro (1984)
    Springer
    Urological research 12 (1984), S. 187-192 
    Details
    ISSN: 1434-0879
    Keywords: Gossypol ; Bull spermatozoa ; Motility ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Gossypol acetic acid in a concentration of 1,000 μg/ml solvent is able to immobilize 1 ml of native bull semen (sperm concentration: 8.5×108/ml; motility rate: 87.4%) within 30 min. After GAA treatment the spermatozoa show severe morphological damage on the membrane system, on the acrosomal complex and on the tubular complex of the end piece. The working mechanism of GAA can be assumed to be inactivation of enzyme activities or in direct reactions with plasma membrane material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00255921
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 66
    Electronic Resource
    Electronic Resource
    Ultrastructure of the wall of the Dandy-Walker cyst (1984)
    Springer
    Acta neuropathologica 62 (1984), S. 225-229 
    Details
    ISSN: 1432-0533
    Keywords: Dandy-Walker syndrome ; Dandy-Walker cyst ; Ependymal cell ; Ultrastructure ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ultrastructure of the wall of the Dandy-Walker cyst has been described rarely. A boy aged 2 years was confirmed clinically, neuroradiologically, and operatively as having a Dandy-Walker cyst in the posterior fossa. The cyst wall obtained during surgery consisted of an outer arachnoid cell layer, intermediate interwoven neuroglial strands, and an inner layer of cells which lacked the characteristic appearance of ependyma. An unusual finding was a small, buried island of ependymal cells in the intermediate layer of the neuroglial tissue. Ultrastructural study of the cyst wall provides a better understanding of the pathogenesis of the Dandy-Walker syndrome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00691856
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 67
    Electronic Resource
    Electronic Resource
    Cytoplasmic tubular inclusion in ganglioneuroma (1984)
    Springer
    Acta neuropathologica 64 (1984), S. 81-84 
    Details
    ISSN: 1432-0533
    Keywords: Ganglioneuroma ; Cytoplasmic tubular inclusion ; Smooth endoplasmic reticulum ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Unusual tubular inclusions were observed in the cytoplasm of ganglion cells of a mediastinal ganglioneuroma in a boy of 7 years. The inclusions consisted of an aggregation of about 100-nm-sized tubular structures resembling ‘honeycomb-like’ tubular structures in the axoplasm of rats and mice and suggested to be derived from dilated rough endoplasmic reticulum. These structures differ from profiles reported in normal and pathologic conditions and seem to be related to the neoplastic character of the ganglion cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00695612
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 68
    Electronic Resource
    Electronic Resource
    Ultrastructure of cerebellar capillary hemangioblastoma (1984)
    Springer
    Acta neuropathologica 64 (1984), S. 308-318 
    Details
    ISSN: 1432-0533
    Keywords: Angiogenesis ; Cerebellar hemangioblastoma ; Degranulation ; Heparin ; Mast cell ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The topographic distribution, population density, and ultrastructural features of mast cells were studied in six cases of cerebellar capillary hemangioblastoma. The vascular area of tumor tissue contained large numbers of mast cells (6.3 cells/high power field, ×400) in comparison with hyalinized area (0.3 cell) and adjacent cerebellar tissue (〈0.1 cell). Close association of mast cells with endothelial cells and stromal cells was found. The morphology of mast cell granules and their degranulation through dissolution of granule contents and exocytosis were illustrated. The findings suggest that an increased number of mast cells may represent one of the characteristic histological features of capillary hemangioblastoma, and continuous degranulation of mast cell granules with release of heparin may play an important pathophysiologic role in the vascular proliferation and expansion of the tumor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00690396
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 69
    Electronic Resource
    Electronic Resource
    The response of the uterine surface to ovarian hormones in the aged rat (1984)
    Springer
    Anatomy and embryology 169 (1984), S. 205-208 
    Details
    ISSN: 1432-0568
    Keywords: Rat uterus ; Epithelium ; Aging ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary By scanning electron microscopy uterine luminal epithelium of the rat was studied to determine whether aging alters ovarian hormone stimulated ultrastructural changes in that portion of the endometrial surface into which implantation takes place in the younger animal. Results show that in the aged rat this surface differentiates in response to ovarian hormones in a manner qualitatively similar to that which occurs in the young animal. Epithelial cells of ovariectomized rats, both young and aged, were polygonal in outline, flattened, or even somewhat concave, and had short microvilli. Following estrogen treatment cells of both groups were round or oval and bulged into the lumen. Cells of young rats were covered with long microvilli. Most cells of aged rats had microvilli of equal or greater length; a small number of epithelial cells had fewer and shorter microvilli. Cells of progesterone-treated young and aged animals both were covered with short microvilli and bore membrane protrusions. The protrusions varied in size, shape and numbers both within and between age groups. These findings suggest that differences in the surface ultrastructure of the aged uterus reflect age-related changes in hormone levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00303150
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 70
    Electronic Resource
    Electronic Resource
    X-ray microanalysis of monoaminergic terminals in the nucleus tegmentalis dorsalis of the chicken (1984)
    Springer
    Anatomy and embryology 170 (1984), S. 87-91 
    Details
    ISSN: 1432-0568
    Keywords: Monoamine ; X-ray microanalysis ; Ultrastructure ; Brain stem ; Chicken
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary X-ray microanalysis after aldehyde-chromatedichromate treatment served to confirm the presence of monoaminergic terminals in the nucleus tegmentalis dorsalis (NTD) of the chicken. The monoaminergic terminals were represented as neuronal elements with electron-dense vesicles (EDVs) of several different shapes as seen in Eponembedded semi-thin sections. Conventional electron microscopic observations of the adjacent ultra-thin sections showed the EDVs to be comprised of spherical medium-sized (about 80 nm in diameter), large dense-cored (about 120 nm) and elongated granular vesicles (100–220 nm) in the same nerve varicosities. It is probable that the NTD, being a center of catecholaminergic efferent projections, may also receive direct monoaminergic inputs from an unknown area of the brain and/or from recurrent collaterals of the same catecholamine-containing neurons in the NTD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319462
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 71
    Electronic Resource
    Electronic Resource
    Ultrastructure of the cumulus cell mass surrounding a human egg in the pronuclear stage (1984)
    Springer
    Anatomy and embryology 170 (1984), S. 107-112 
    Details
    ISSN: 1432-0568
    Keywords: Ultrastructure ; Cumulus ; Oocyte complex ; Human egg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cumulus cell mass enclosing a penetrated human egg was studied. The egg, recovered from the Fallopian tube approximately 80 h after luteinizing hormone peak and 35 h after insemination, was surrounded by a large, expanded and dissociated cumulus. Dispersions of the outermost cumulus cell layers occurred during processing, the innermost cell layers remained attached enclosing the egg. The photomicrographs showed that the follicular cells were embedded in an intercellular matrix and contact via gap-junction-like structures between neighboring cells existed. Cumulus cell processes traversing the zona pellucida were not found. Two types of follicular cells coexisted within the cumulus, light and dark cells. These cellular types, were different in morphology and size. Light cells displayed cytoplasmic organelles normally associated with protein synthesis and steroidogenesis. Dark cells with long cytoplasmic processes were involved in sperm phagocytosis. It is suggested from the characteristics of the cytoplasmic organclles that dark cells seem to be modified light follicular cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319465
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 72
    Electronic Resource
    Electronic Resource
    Serotonin nerve fibers in the primary visual cortex of the monkey (1984)
    Springer
    Anatomy and embryology 169 (1984), S. 1-8 
    Details
    ISSN: 1432-0568
    Keywords: Serotonin ; Primary visual cortex ; Monkey ; Ultrastructure ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A quantitative and immunoelectronmicroscopical analysis of serotonin nerve fibers in the primary visual cortex of the monkey (Macaca fuscata) was made using a sensitive immunoperoxidase method for serotonin. The overall numerical density of serotonin-containing varicosities in the primate striate cortex was approximately 770,000/mm3 and the highest concentration of immunore-active varicosities (ca. 1,400,000/mm3) was observed in the upper portion of layer IVc, the next highest concentration being in layer IVb (ca. 1,180,000/mm3). At the ultrastructural level, the electron dense immunoreactive products were observed in the small granules (10–65 nm in diameter). The varicosities were usually small (0.5–1.0 μm in diameter) and made contact with both stellate and pyramidal cells. Serotonin fibers were often in close apposition to the poorly myelinated axons in layers IVb, V, and VI, and they rarely formed distinct synaptic structures with unlabelled neuronal elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00300581
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 73
    Electronic Resource
    Electronic Resource
    Induction of the morphologic changes of both acute and chronic experimental myasthenia by monoclonal antibody directed against acetylcholine receptor (1984)
    Springer
    Acta neuropathologica 63 (1984), S. 131-143 
    Details
    ISSN: 1432-0533
    Keywords: Anti-acetylcholine receptor antibody ; Experimental autoimmune myasthenia gravis ; Monoclonal antibody ; Myasthenia gravis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To investigate pathogenic mechanisms in experimental autoimmune myasthenia gravis (EAMG) and myasthenia gravis (MG), we studied the acute and chronic effects in rats of injection of rat monoclonal antibodies (MCABs) directed against the acetylcholine receptor (AChR). Animals were severely weak 12 h after a single injection, at which time macrophages were found invading endplate regions of muscle and cholinesterase-stained regions were separted from the underlying muscle fibers. Ultrastructural studies showed findings identical to the acute phase of EAMG: degenerating postsynaptic membranes and invasion and phagocytosis of endplate regions by macrophages. Animals receiving sublethal doses of MCAB recovered clinically by 4–5 days after injection. Recovery was accompanied by a progressive decrease in the number of macrophages associated with endplates and reapposition to the myofibers of the cholinesterasestained regions. Animals injected once, or repeatedly over several months, remained clinically and electromyographically normal after recovery from the initial episode of weakness, but their endplate ultrastructure was highly simplified with blunted or absent synaptic folds and shallow or absent secondary synaptic clefts. These studies demonstrate that anti-AChR MCABs can induce the changes of both acute and chronic EAMG. There is good correlation between the inflammatory changes and the acute clinical disease but poor correlation between morphological and clinical parameters in the chronic syndrome. The latter observation suggests that severe ultrastructural changes, similar to those seen in chronic EAMG and MG, cannot account, at least in rats, for the clinical and electrophysiologic abnormalities of MG.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00697195
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 74
    Electronic Resource
    Electronic Resource
    Neurofibromatosis tumor and skin cells in culture (1984)
    Springer
    Acta neuropathologica 63 (1984), S. 269-275 
    Details
    ISSN: 1432-0533
    Keywords: Neurofibromatosis ; Cell culture ; Cell surface ; Cytoskeleton ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Structural proteins of cultured neurofibromatosis (NF) tumor and skin cells were studied with reference to control skin fibroblasts. In polyacrylamide gel electrophoresis (PAGE)/fluorography the banding patterns of the cell lysates were markedly similar. NF tumor cells, however, produced a 60 kD band with a stronger and a 48 kD band with a lighter protein staining and metabolic labeling intensity. Furthermore, skin cells were also characterized by a 26 kD protein and the tumor cells by a 22 kD protein with high metabolic labeling intensity. Neuraminidase/galactose oxidase/NaB3H4-labeled NF skin and control skin cells possessed a 220 kD protein that was less intensively labeled in the tumor cells. The banding pattern of the skin cells was also characterized by a protein with slightly lower molecular weight (86 kD) than that of the tumor cell lysates (90 kD). In all cell lines studied indirect immunofluorescence stainings revealed bright arrays of vimentin type intermediary filaments but no desmin, cytokeratin, glial fibrillary acidic protein (GFAP), or neurofilament proteins. NF skin and control skin cells possessed well developed actin-containing bundles of microfilaments, while those of the tumor cells lacked a typical stress-fiber organization. The general morphology of the tumor cell cultures was also irregular. Transmission electron microscopy revealed no basic differences in the structure of intermediary filaments or microfilaments. The present data provide basic knowledge of neurofibromatosis skin and tumor cells and demonstrate that cultured cells originating from neurofibromas are defective in both their intracellular and extracellular organization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00687332
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 75
    Electronic Resource
    Electronic Resource
    Ultrastructural and histophysiological studies on the blood-nerve barrier and perineurial barrier in leprosy neuropathy (1984)
    Springer
    Acta neuropathologica 64 (1984), S. 282-296 
    Details
    ISSN: 1432-0533
    Keywords: Blood-nerve Barrier ; Perineurial barrier ; Leprosy neuropathy ; Ultrastructure ; Ferritin ; Ageing ; Drug treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Onset and nature of ultrastructural changes in endoneurial vasa nervorum during the pathogenesis of leprosy neuropathy and possibly associated alterations in the “blood-nerve barrier” were investigated, together with perineurial barrier functioning, in mice infected 20–28 months previously withMycobacterium leprae and in (ageing) non-infected mice. Barriers were tested by i.v. administration of markers (Trypan blue and ferritin) 1–4 days before killing the mice. Twenty-eight months after infection, histopathology of sciatic nerves was comparable to that seen in sensory nerves in clinically early human (borderline-) lepromatous leprosy. Schwann cells and endoneurial macrophages were bacillated, endothelia of endoneurial vessels not, and the perineurium rarely. Many infected mice and all (ageing) controls possessed ultrastructurally and functionally normal endoneurial vessels. Their continuous endothelium with close junctions had prevented marker passage, even when surrounding endoneurial tissue cells were quite heavily bacillated. The perineurium was also normal. By contrast, in infected mice showing hind limb paralysis serious histopathologic involvement and large globi of bacilli intrafascicularly in sciatic nerves, endoneurial blood vessels were abnormal. Open endothelial junctions, extreme attenuation, fenestrations, and luminal protrusions were all features comparable to neural microangiopathy encountered in leprosy patients (Boddingius 1977a, b). The “blood-nerve barrier” clearly had become defective allowing excessive exudation of Trypan blue and ferritin, via four pathways from the vessel lumen, deep into surrounding endoneurial tissues but halted by a normal perineurial barrier. Markers in such “blue” nerves were not found in bacillated or non-bacillated Schwann cells, thus denying significant phagocytotic and lysosomal activities of Schwann cells at this stage of neuropathy. Possible implications of barrier performances for anti-leprosy drug treatment of patients are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00690394
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 76
    Electronic Resource
    Electronic Resource
    Epidermoid metaplasia in apocrine cystadenoma of the penis (1984)
    Springer
    Archives of dermatological research 276 (1984), S. 170-177 
    Details
    ISSN: 1432-069X
    Keywords: Penile apocrine cystadenoma ; Ultrastructure ; Filamentous fuzzy coat ; Epidermoid metaplasia ; Peridermlike cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two cystadenomas occurring near the frenulum of the penis revealed a predominantly secretory pseudostratified columnar epithelium with PAS-reactive dome-shaped cytoplasmic protrusions at the luminal cellular parts. The content of secretory vacuoles was discharged into the cyst lumen by an exocytotic (eccrine) and ballooning type of extrusion. There were no indications of a real apocrine extrusion mechanism. No histogenetic derivation of these penile cystadenomas from apocrine sweat glands could be proved. An antennalike filamentous fuzzy coat on the luminal cytoplasmic membrane was most remarkable. Regionally, an epidermoid differentiation had developed. Morphologically, this process had begun just above the basal cell layer which had remained unchanged and led to the establishment of a stratified epithelium.Hyalin lamellarlike flattened cells at the luminal part displayed necrobiotic features and resembled periderm cells. There was no keratin pattern. Luminal cells of epidermoid differentiation still revealed a filamentous fuzzy coat which indicated that the undifferentiated cuboidal basal cells basically had a prospective secretory meaning and probably represented the target cells in the process of metaplasia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00414015
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 77
    Electronic Resource
    Electronic Resource
    Ultrastructure of heart muscle in short-term diabetic rats: influence of insulin treatment (1984)
    Springer
    Diabetologia 27 (1984), S. 397-402 
    Details
    ISSN: 1432-0428
    Keywords: Ultrastructure ; heart muscle ; streptozotocin ; short-term diabetes ; insulin treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ultrastructure of myocardium was examined in short-term diabetic rats. Morphometric analysis showed the volume of myocytic mitochondria, sarcoplasmic reticulum and lipid droplets to be significantly increased compared with those of control animals. Further measurements of mitochondria and sarcoplasmic reticulum indicated that the augmentation of these compartments was accountable by the enlargement of pre-existing mitochondria, which were swollen, and of pre-existing tubules of sarcoplasmic reticulum, the lumen of which was dilated. After insulin treatment the morphological changes were returned to normal which indicates that they were not due to the toxic effect of streptozotocin but were caused by the diabetic state per se. This suggestion is further supported by the finding that experimentally induced metabolic acidosis without diabetes did not cause any morphologically detectable changes in the heart muscle. It is concluded that short-term diabetes in the rat causes mitochondrial swelling, dilatation of sarcoplasmic reticulum and accumulation of lipid in cardiac myocytes, and that these changes are preventable with insulin treatment. We suggest that insulin may have an important role in the maintenance of metabolism in heart muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00304857
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 78
    Electronic Resource
    Electronic Resource
    Paired twisted filaments a new ultrastructural marker of human pinealomas? (1984)
    Springer
    Acta neuropathologica 65 (1984), S. 163-165 
    Details
    ISSN: 1432-0533
    Keywords: Human pinealomas ; Ultrastructure ; Paired twisted filaments ; Paired helical filaments ; Cytoskeleton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Paired twisted filaments (PTF) forming helices are described in tumor cells of three human pine-alomas. Each filament was 8.11±1.55 nm wide. The maximal width of the helix was 16.62±2.62 nm. The periodicity of the constrictions was 26.63±4.49 nm. These characteristics appeared original, suggesting protein, filaments possibly specific of pinealocytes. The similarities and discrepancies between PTF and Alzheimer's paired helical filaments (PHF) are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00690471
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 79
    Electronic Resource
    Electronic Resource
    Ultrastructural observation on a colloid cyst of the third ventricle (1984)
    Springer
    Acta neuropathologica 65 (1984), S. 41-45 
    Details
    ISSN: 1432-0533
    Keywords: Colloid cyst ; Third ventricle ; Ultrastructure ; Pathogenesis ; Rathke's cyst
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The case involves a colloid cyst of the third ventricle in a 20-year-old man. The lining epithelia of the cyst were composed of two different types of epithelial cells; stratified squamous cells and mucincontaining columnar cells. The presence of both squamous and glandular cells in the cyst wall supports the contention that the colloid cyst in the present case derived from an non-neuroepithelial source. The clinico-pathology of this cystic tumor is compared here with other epithelial cysts of the central nervous system (CNS), especially Rathke's cyst.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00689826
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 80
    Electronic Resource
    Electronic Resource
    Length and shape of enamel crystals (1984)
    Springer
    Calcified tissue international 36 (1984), S. 550-555 
    Details
    ISSN: 1432-0827
    Keywords: Enamel crystals ; Length ; Shape ; Apatite ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary An original method for fractionating and preparing isolated crystals of homogeneous size was developed. It was demonstrated that enamel apatite crystals are at least 100 µm long. The flexibility of the very long crystallites was demonstrated. Crystal curvatures, accounting for the irregular course of the prisms through the enamel thickness, were visualized and measured. It was shown that in the deep forming enamel layer, lateral branches may grow out of the crystals and crystal fusing often occurs, inducing the crystallites to assume pyramidal shapes with their wide bases pointing toward the dentino-enamel junction and one or two tops toward Tomes' processes. During the maturation process, the two tops of the still immature crystals also fuse so that the mature crystals acquire a rodlike aspect, with parallel faces and steplike graduations along thec axis, allowing a close contact between the crystals. These results support the hypothesis that the crystallites would be continuous from the dentino-enamel junction to the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405364
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 81
    Electronic Resource
    Electronic Resource
    4-Ammopyridine-induced ultrastructural alterations of pinched-off nerve terminals from rat cerebral cortex (1984)
    Springer
    Experimental brain research 54 (1984), S. 385-389 
    Details
    ISSN: 1432-1106
    Keywords: Synaptosome ; 4-Aminopyridine ; Ultrastructure ; Exocytosis ; Recycling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Pinched-off nerve terminals (synaptosomes) from rat cerebral cortex were depolarized with 60 mM KCl and treated with 20 mM 4-aminopyridine in order to evaluate ultrastructural alterations. The empty presynaptic terminals were counted and their number was given as a percentage of the normal terminals. The proportion of empty terminals increased from 10.47±1.56% to 32.45±1.88% (P 〈 0.001) following treatment with 20 mM 4-aminopyridine. This effect of 4-aminopyridine depended on the presence of Ca++ in the incubation medium. The results are discussed in terms of facilitation by 4-aminopyridine of exocytotic transmitter release. We think that the increase of the empty synaptosomes was due to the exhaustion or inhibition of the synaptic vesicle recycling mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236242
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 82
    Electronic Resource
    Electronic Resource
    Synaptology of the hypoglossal nucleus in the rat (1984)
    Springer
    Experimental brain research 57 (1984), S. 22-32 
    Details
    ISSN: 1432-1106
    Keywords: Ultrastructure ; Synaptology ; Hypoglossal nucleus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The purpose of this study was to define the types and distribution of synaptic terminals in the hypoglossal nucleus (XII) of the rat. Based on differences in bouton and vesicle size and shape, synaptic specializations and association with postsynaptic organelles, five types of terminals were identified in XII. In order of decreasing frequency they were: 1) S-boutons (spherical vesicles with an asymmetrical synapse); 2) F-boutons (flattened vesicles with a symmetrical synapse); 3) P-boutons (pleomorphic admixture of flattened and spherical vesicles with a symmetrical synapse); 4) C-boutons (pleomorphic vesicles with a subsynaptic cistern); and 5) Tboutons (spherical vesicles with an asymmetrical synapse and subsynaptic dense bodies). S-boutons were the predominant type found on dendrites, while boutons containing flattened vesicles were more prevalent on motoneuron somata. C-boutons were restricted exclusively to cell bodies and large dendrites, and T-boutons were seen primarily on smaller dendritic profiles. These results are, in general, comparable to those previously described in the ventral horn and cranial nerve motor nuclei in several species. However, differences were noted. Specifically, large M-boutons and axo-axonic synapses were not observed in the present study. The functional significance of these findings are discussed in relation to oro-lingual behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231128
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 83
    Electronic Resource
    Electronic Resource
    Ultrastructural changes in rat Clara cells induced by a single dose of O,S,S-trimethyl phosphorodithioate (1984)
    Springer
    Archives of toxicology 56 (1984), S. 59-65 
    Details
    ISSN: 1432-0738
    Keywords: Trialkylphosphorothioates ; Rat ; Lung ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The oral administration of an LD50 dose (25 mg/kg) of O,S,S-trimethyl phosphorodithioate to rats induced immediate, cholinergic symptoms. A delayed respiratory crisis followed, 3–4 days later, involving a pronounced increase in lung weight and extensive injury to the alveolar epithelium. This compound also induced the immediate liberation of secretory granules from the Clara cells. Minor changes in the surface appearance of these cells were also observed but no signs of injury were found in any cells of the bronchiolar epithelium. The complement of secretory granules was monitored, by the morphometric analysis of ultrathin sections. Clara cells from control animals were found to contain 9.55±1.16 (SEM) granules per cell profile. The Clara cells from dosed animals were largely devoid of granules until the 3rd day after administration. Many of these agranular cells were arranged in clusters and often showed signs of mitotic division. In surviving animals the subsequent replacement of granules resulted in a large increase in the numbers present and many exhibited abnormal morphology. Over twice the normal complement of granules, 22.45±0.42 (SEM) per cell profile, was found 6 days after dosing. The complement of granules subsequently returned to normal levels and the clusters of Clara cells were resolved within 14 days of dosing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00316355
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 84
    Electronic Resource
    Electronic Resource
    Isolation and characterization of a new coccoid methanogen, Methanogenium tatii spec. nov. from a solfataric field on Mount Tatio (1984)
    Springer
    Archives of microbiology 137 (1984), S. 308-315 
    Details
    ISSN: 1432-072X
    Keywords: Methanogenium tatii ; Ultrastructure ; Physiology ; Glycoproteins ; DNA-DNA Homology ; Taxonomy ; Archaebacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new coccoid methanogen, Methanogenium tatii, was isolated and characterized. The mesophilic isolate can grow on and produce methane from H2:CO2 and formate. For growth acetate is strictly required. The cell shape, the G+C content of 54 mol% and DNA-DNA homology data suggest it to be a Methanogenium species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00410727
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 85
    Electronic Resource
    Electronic Resource
    Fine structure of the knobby spore type of Streptomyces torulosus (1984)
    Springer
    Archives of microbiology 138 (1984), S. 229-232 
    Details
    ISSN: 1432-072X
    Keywords: Actinomycetes ; Streptomyces torulosus ; Morphology ; Ultrastructure ; Verrucate spores ; Knobby ornamentation ; Sheath
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The type strain of Streptomyces torulosus Lyons and Pridham (1971) was studied by scanning- and transmission electron microscope. Spore chains were formed in spirals by aerial mycelium. The spores were connected by nozzles in which small channels could be observed. The knobby ornamentations of the spores arised on a thin fibrous sheath, enveloping the spore chains. These irregular blunt projections, called knobs, had varying diameters of 100 to 250 nm. The base of the knob, consisting of globose to flattened electron dense material, was sitting directly on the sheath. It was covered by several small vesicles of the same material. Each hollow vesicle beared a thin bowlshaped shell of electron transparent material. In general, the cupular bowls and their supporting vesicles became easily depressed on their base, but not detached from the surface of the spores. This type of knobby spore ornamentation was suggested to be designated as a verrucate spore type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00402126
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 86
    Electronic Resource
    Electronic Resource
    Membrane-bound nitrite oxidoreductase of Nitrobacter: evidence for a nitrate reductase system (1984)
    Springer
    Archives of microbiology 140 (1984), S. 153-158 
    Details
    ISSN: 1432-072X
    Keywords: Nitrobacter hamburgensis ; Nitrite oxidoreductase ; Nitrate reductase ; Molybdenum iron-sulfur protein ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrite oxidoreductase, the essential enzyme complex of nitrite oxidizing membranes, was isolated from cells of the nitrifying bacterium Nitrobacter hamburgensis. The enzyme system was solubilized and purified in the presence of 0.25% sodium deoxycholate. Nitrite oxidoreductase oxidized nitrite to nitrate in the presence of ferricyanide. The pH optimum was 8.0, and the apparent K m value for nitrite amounted to 3.6 mM. With reduced methyl-and benzylviologen nitrite oxidoreductase exhibited nitrate reductase activity with an apparent K m value of 0.9 mM for nitrate. NADH was also a suitable electron donor for nitrate reduction. The pH optimum was 7.0. Treatment with SDS resulted in the dissociation into 3 subunits of 116,000, 65,000 and 32,000. The enzyme complex contained iron, molydbenum, sulfur and copper. A c-type cytochrome was present. Isolated nitrite oxidoreductase is a particle of 95±30 Å in diameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00454918
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 87
    Electronic Resource
    Electronic Resource
    Ultrastructural morphometry of collagen from lamina propria during experimental oral carcinogenesis and chronic inflammation (1984)
    Springer
    Journal of cancer research and clinical oncology 107 (1984), S. 183-194 
    Details
    ISSN: 1432-1335
    Keywords: Collagen ; Stereology ; Oral carcinogenesis ; Inflammation ; Ultrastructure ; Lamina propria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Stereological point-counting methods were used to determine the volumetric alterations in collagen from the lamina propria immediately beneath the epithelial-connective tissue junction in hamster check-pouch mucosa treated with the chemical carcinogen DMBA. In addition, a non-neoplastic inflammatory control was evaluated in which a delayed hypersensitivity reaction was induced by the contact-sensitising agent DNCB. DMBA-treated tissues were assigned to histopathologically defined hyperplasia, dysplasia and carcinoma stages. The volume densities of collagen present in unit volume of extracellular lamina propria were found to decrease progressively and significantly in DMBA-treated tissues when compared with values obtained from normal untreated mucosa. Values from the inflammatory control were comparable with those from the dysplasia stage of carcinogenesis. The mechanisms responsible for these decreases in collagen volume density are unknown, but contributory factors might include collagen destruction by enzymes originating in either the epithelium or the cells of the inflammatory infiltrate, dilution of collagen produced by inflammatory oedema or alterations in the synthetic capabilities of fibroblasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01032605
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 88
    Electronic Resource
    Electronic Resource
    Ultrastructure of gill epithelial cells of Diopatra neapolitana (Annelida, Polychaeta) (1984)
    Springer
    Zoomorphology 104 (1984), S. 304-309 
    Details
    ISSN: 1432-234X
    Keywords: Ultrastructure ; Gills ; Epithelial cells ; Polychaeta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of gill epidermal cells of Diopatra neapolitana and their relationship with blood spaces are described. The existence of a basal infolding complex, related to the blood spaces, is also reported. A possible involvement of these cells in osmoregulation and ion interchange, apart from their well-known role in respiration, is suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312012
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 89
    Electronic Resource
    Electronic Resource
    The ultrastructure of experimental arthrosis in dogs (1984)
    Springer
    International orthopaedics 7 (1984), S. 215-221 
    Details
    ISSN: 1432-5195
    Keywords: Experimental arthrosis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Les auteurs ont réalisé une arthrose expérimentale chez le chien en injectant dans une articulation le liquide obtenu par ponction d'une autre articulation du même animal, dont le cartilage a été préalablement scarifié de façon aseptique. L'examen des surfaces articulaires en microscopie électronique montre des altérations dégénératives progressives au niveau de la matrice extra-cellulaire, des chondrocytes et de la membrane péri-cellulaire. Ces modifications augmentent après des injections répétées de liquide synovial. Dans une autre série d'animaux, on a injecté soit le culot de centrifugation, soit le surnageant et on a comparé les effets obtenus vis-à-vis des structures cellulaires et extra-cellulaires.
    Notes: Summary Experimental arthrosis was induced in previously healthy joints in a group of dogs by injection of fluid aspirated from another joint of the same animal previously damaged by trauma under sterile conditions. Using electron microscopy progressive degenerative changes were observed at the surface of the joint, in the extracellular matrix, in the chondrocytes and in the pericellular band. The changes increased following serial injections of the joint fluid. In another series, the joints were injected either with the centrifuged concentrate or the supernatant fluid and a comparison made of the contrasting effects upon the cellular and extracellular structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00266830
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 90
    Electronic Resource
    Electronic Resource
    Stromal cells of the fibroadenoma of the human breast (1984)
    Springer
    Virchows Archiv 404 (1984), S. 7-16 
    Details
    ISSN: 1432-2307
    Keywords: Fibroadenoma ; Stromal cells ; Actin ; Ultrastructure ; Myofibroblast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Fourteen fibroadenomas of the human breast were examined by light and electron microscopy, and by immunohistochemistry for actin. They were classified into 3 groups according to their stromal patterns; myxoid, fibrous-cellular and sclerotic. Actin immunohistochemistry revealed that the stromal areas were strongly positive in the fibrous-cellular group and weakly positive in the myxoid and sclerotic groups. By electron microscopy the stromal cells in most cases of the myxoid and fibrous-cellular groups were fibroblasts, containing varying amounts of microfilaments, 5–7 nm in diameter (actin type filaments). However, a dense body was not usually present suggesting these stromal cells were variants of myofibroblasts. The amount of microfilaments in fibroblasts was greater in the fibrous-cellular group than in the myxoid group. This was consistent with the results of actin immunohistochemistry. In 3 cases of the fibrous-cellular group peculiar structures simulating Z-lines of striated muscles were noted in some stromal cells. Since no myosin filaments were detected, they were regarded as intermediate structures between Z-lines of striated muscles and dense bodies of smooth muscles. In the sclerotic group, stromal fibroblasts were sparse and had fewer organelles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00704246
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 91
    Electronic Resource
    Electronic Resource
    Unequal distribution of plastids during generative cell formation in Impatiens (1984)
    Springer
    Theoretical and applied genetics 68 (1984), S. 305-309 
    Details
    ISSN: 1432-2242
    Keywords: Impatiens ; Microspore mitosis ; Plastid distribution ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This paper describes the unequal distribution of plastids in the developing microspores of Impatiens walleriana and Impatiens glandulifera which leads to the exclusion of plastids from the generative cell. During the development from young microspore to the onset of mitosis a change in the organization of the cytoplasm and distribution of organelles is gradually established. This includes the formation of vacuoles at the poles of the elongate-shaped microspores, the movement of the nucleus to a position near the microspore wall in the central part of the cell, and the accumulation of the plastids to a position near the wall at the opposite side of the cell. In Impatiens walleriana, the accumulated plastids are separated from each other by ER cisterns, and some mitochondria are also accumulated. In both Impatiens species, the portion of the microspore in which the generative cell will be formed is completely devoid of plastids at the time mitosis starts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00267882
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 92
    Electronic Resource
    Electronic Resource
    Degenerative regression of the digestive tract in the colonial ascidian Botryllus schlossen (Pallas) (1984)
    Springer
    Cell & tissue research 235 (1984), S. 309-318 
    Details
    ISSN: 1432-0878
    Keywords: Ascidian ; Gut ; Cell involution ; Ultrastructure ; Phagocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Degenerative changes in the digestive tract of zooids of Botryllus schlosseri were studied by light and electron microscopy. Three main processes occurred in the tissues: contraction, involution and phagocytosis. The contraction of epidermis and peribranchial epithelium in which cytoplasmic microfilaments probably participate, seemed to have a special role in compressing the underlying organs. During contraction most of the body cavities collapsed, the branchial walls disintegrated and the fragments were rapidly taken up by large phagocytes. The gut epithelium retained its apparent continuity longer, though isolated phagocytes infiltrated it to eliminate single cells. Cell degeneration came about chiefly either through swelling and lysis of cells or through loss of water and condensation of cytoplasm and nucleus. The fate of all regressed tissues was to be engulfed and digested by wandering phagocytes. However, it was also observed that numerous cells of different epithelia could act as fixed phagocytes by engulfing cell debris and entire cells into heterophagic vacuoles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217855
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 93
    Electronic Resource
    Electronic Resource
    The pig blastocyst: Its ultrastructure and the uptake of protein macromolecules (1984)
    Springer
    Cell & tissue research 235 (1984), S. 347-356 
    Details
    ISSN: 1432-0878
    Keywords: Blastocyst ; Ultrastructure ; Pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Between days 8 and 11 of pregnancy spherical blastocysts from 0.3 to 10 mm in diameter were flushed from the uterine horns of Dutch Landrace pigs. A description of their ultrastructure is given, and the uptake of horseradish peroxidase and ferritin is demonstrated. The ultrastructure of the trophoblast was similar at all ages studied. The trophoblast which has many apical microvilli is able to take up and digest the macromolecules which were offered in the in vitro incubation medium. The hypoblast consists of flattened cells. In blastocysts 2 mm and larger, compact cells bearing microvilli are found below the embryoblast. Cell organelles indicating protein synthesis are found within hypoblast cells of such blastocysts. In the embryoblast, local concentrations of cell organelles are visible, indicating that differentiation has started. After the disappearance of Rauber's layer, which takes place when the blastocyst reaches a diameter of about 2 mm, superficial embryoblast cells develop short microvilli. The cells do not absorb ferritin or peroxidase but are dependent on the trophoblast for their food requirements. All cell layers in the blastocyst contain mitochondria that have characteristics of those found in steroidproducing cells. The significance of the uptake and digestion of macromolecules by trophoblast cells, the synthesis of protein by hypoblast cells and the possible synthesis of steroids is discussed with respect to the relationship between the cell layers of the blastocyst and in the context of conceptomaternal relationships.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217859
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 94
    Electronic Resource
    Electronic Resource
    Changes in human skeletal muscle induced by long-term eccentric exercise (1984)
    Springer
    Cell & tissue research 236 (1984), S. 365-372 
    Details
    ISSN: 1432-0878
    Keywords: Skeletal muscles ; Myofibrils ; Ultrastructure ; Exertion ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of muscle fibres from m. vastus lateralis of nine healthy males (mean age 26 years) was investigated. Four individuals constituted non-exercised controls while five subjects participated in a two-months eccentric muscular training program. Specimens from the controls showed a well-preserved, regular myofibrillar band pattern while changes in the myofibrillar architecture were constantly found in specimens taken after the training program. These changes consisted of Z-band alterations, Z-bands being out of register, extra sarcomeres, Z-band extensions and bisected Z-bands. Between the separated Z-band halves, thin and thick myofilaments as well as abundant glycogen particles and/or ribosomes, were observed. Type-2 (fast-twitch) fibres were predominantly affected. Contrary to the controls the trained individuals constantly showed a greater variation in sarcomere lengths in Type-2 fibres than in Type-1 fibres. It is concluded that muscular work of high tension can induce fine-structural alterations. When repeated over a long period of time, extreme tension demands seem to initiate reorganization in the muscle fibres, predominantly in the, ultrastructurally defined, Type-2 fibres. This adaptation probably results in a better stretchability of the muscle fibres, reduces the risk for mechanical damage and brings about an optimal overlap between actin and myosin filaments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00214240
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 95
    Electronic Resource
    Electronic Resource
    Ultrastructure and morphometry of the stomach muscle of Amphiuma tridactylum (1984)
    Springer
    Cell & tissue research 236 (1984), S. 393-397 
    Details
    ISSN: 1432-0878
    Keywords: Smooth muscle ; Salamander, Amphiuma ; Ultrastructure ; Stereology ; Volume: surface area ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An ultrastructural and stereological examination was performed on stomach smooth muscle of the salamander Amphiuma. This tissue has very large cells, ranging up to 12×1500 μm when relaxed. The extracellular space is 31% of the tissue volume, and the tissue contains 84.6% water. These values are similar to those of other amphibian and mammalian gastrointestinal smooth muscle. The cells possess the usual smooth muscle organelles. Thick, thin and intermediate filaments are present, along with membrane-associated and cytoplasmic dense regions. There is a well-developed sarcoplasmic reticulum and many microtubules. Caveolae are found in rows along the cellular surface; the caveolae increase the cellular surface area by about 70%. The ratio mean volume: surface area of the cells is 1.26 μm. This tissue appears to be typical of gastrointestinal smooth muscle, with the exception of the very large size of the cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00214243
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 96
    Electronic Resource
    Electronic Resource
    Reproduction and sexual development in a freshwater gastrotrich (1984)
    Springer
    Cell & tissue research 236 (1984), S. 619-628 
    Details
    ISSN: 1432-0878
    Keywords: Gastrotricha, freshwater ; Sperm, reduced ; Ultrastructure ; Spermatogenesis ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Spermatogenesis and spermiogenesis in Lepidodermella squammata are confined to the postparthenogenic phase of the life cycle and coincide with developmental changes in the bilateral female gonads. Male stages are bilateral but asynchronous, in the lateral abdomen anterior to the female gonads. Maximum observed sperm production is two packets per side, or 64 sperm. Sperm formation occurs more rapidly at 27° C than at 20° C (p〈0.001), requiring as little as 1 day. Two spermatogonial mitotic divisions produce a clone of four primary spermatocytes connected by bridges (stage 1). Centrioles are absent. Development occurs within a cyst. Meiotic divisions produce 16 spermatids (stage 2), each containing a dense, elongate, tapered nucleus. Cytoplasmic membranes enclose one end of the nuclear rod, excluding all other organelles. Completion of this process results in stage 3, a packet of 16 sperm associated with one dense sphere, a modified ‘residual body’ containing cytoplasmic debris. The residual body then disappears, leaving the sperm packet of stage 4. Each mature sperm is a dense nuclear rod with surrounding membranes, lacking acrosome, mitochondrion, centrioles, and flagellum. Function of sperm has not been demonstrated. The spermatozoa are of a reduced type not previously described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217231
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 97
    Electronic Resource
    Electronic Resource
    Reproduction and sexual development in a freshwater gastrotrich (1984)
    Springer
    Cell & tissue research 236 (1984), S. 629-636 
    Details
    ISSN: 1432-0878
    Keywords: Oocytes, primary ; Gastrotricha, freshwater ; Ultrastructure ; Synaptonemal complex ; X-body
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Six small cells are present in each of the bilateral gonads of parthenogenically reproductive Lepidodermella squammata. Early in the extended postparthenogenic phase of the life history, these cells undergo limited proliferation followed by differentiation. Primary oocytes of three types are present 0.3 days after deposition of the final parthenogenic egg: small oocytes with presynaptic nuclei; intermediate oocytes with nuclei containing synaptonemal complexes; and larger oocytes with a germinal vesicle. Oocytes persist without further development at least until day four of the postparthenogenic phase. Older isolated animals may contain and even deposit an enlarged egg, but successful progeny does not result. Oocytes are located at the anterior pole of each of the bilateral gonads, adjacent to developing male tissues producing sperm. More posterior cells in the gonad are initially undifferentated in the postparthenogenic phase. Dorsal and central cells first show specialization for secretory activity, and by day four contain peripheral layers of RER and central accumulations of polymorphic secretion droplets. The posterior and ventral cells produce secretion droplets that aggregate into an enlarging bilobed structure called the X-body. Two or three cells in each gonad contribute secretions to the X-body, which is intracellular in a secondary syncytium formed by the contributing cells. Functions for the postparthenogenic gametes and for the X-body are not yet demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217232
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 98
    Electronic Resource
    Electronic Resource
    Arachnoid mater of the bullfrog, Rana catesbeiana (1984)
    Springer
    Cell & tissue research 236 (1984), S. 693-697 
    Details
    ISSN: 1432-0878
    Keywords: Intermediate filaments ; Microtubules ; Caveolae ; Bullfrog ; Arachnoid mater ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the bullfrog, the meninges surrounding the central nervous system include an arachnoid mater that contains layers of cells with abundant intermediate filaments (IFs) having unique organizational characteristics. This membrane contains an inner lamina of cells that resemble fibroblasts and an outer lamina of flattened cells that are almost filled with IFs. The IFs of the outer arachnoid are arranged in compact, arching bundles that lie parallel to the outer surface of the central nervous system. Thus, sections cut tangentially to the membrane reveal bending of filament bundles, whereas transverse sections do not. In some cells bordering the subdural space, bundles of filaments are organized into highly-ordered spiral arrays. Attachments to the numerous desmosomes and, apparently, to the nuclear envelope suggest anchoring of cytoplasmic structures by the IF system. Microtubules occur primarily near the plasma membrane and the nucleus. Numerous caveolae also are associated with the plasma membrane. The unusual abundance, organization, and cytoplasmic relations of IFs in the bullfrog arachnoid suggest that this membrane may serve as an important model for study of fundamental cytoskeletal relations and function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217240
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 99
    Electronic Resource
    Electronic Resource
    Ultrastructure and innervation of the swimbladder of Tetractenos glaber (Tetraodontidae) (1984)
    Springer
    Cell & tissue research 237 (1984), S. 277-284 
    Details
    ISSN: 1432-0878
    Keywords: Swimbladder ; Teleost ; Cholinergic nerves ; Adrenergic nerves ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The general structure, ultrastructure and innervation of the swimbladder of the smooth toadfish, Tetractenos glaber, were examined with light-microscopic, fluorescence-histochemical, and transmission electron-microscopic techniques. The structure of the swimbladder is similar to that of other euphysoclists. Fluorescence histochemistry showed adrenergic fibres in both the secretory and resorptive areas of the swimbladder. Transmission electron microscopy revealed two morphologically distinct axon profiles type-I profiles containing many small, flattened vesicles; type-II profiles containing both large, granular vesicles and rounded, small clear vesicles in varying proportions. The gas-gland cells and surrounding muscularis mucosae are innervated by both type-I and type-II fibres. Type-I fibres also innervate pre-rete arteries. The rete- and gas-gland capillaries do not appear to be innervated. Arteries running to the resorptive area are innervated by type-I fibres. Both type-I and type-II profiles make contact with the muscularis mucosae in the resorptive area. Only type-I fibres innervate the radial dilator muscle in the oval sphincter region, whereas only type II fibres innervate the circular muscle of the oval sphincter. Type-I fibres took up α-methyl-noradrenaline, and could not be found after pre-treatment with 6-hydroxydopamine. They are, therefore, assumed to be adrenergic. Type-II fibres were tentatively identified, by exclusion, as cholinergic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217146
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 100
    Electronic Resource
    Electronic Resource
    Fine structure of regenerating scales and their associated cells in the cichlid Hemichromis bimaculatus (Gill) (1984)
    Springer
    Cell & tissue research 237 (1984), S. 537-547 
    Details
    ISSN: 1432-0878
    Keywords: Scale ; Regeneration ; Ultrastructure ; Cichlid ; Hemichromis bimaculatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Scale regeneration has been studied in Hemichromis bimaculatus. The removed scale, which serves as a control, is covered by its surrounding scleroblasts as can be seen with scanning electron microscopy. Subsequently, during regeneration, a population of scleroblasts arises in the empty dermal pocket as shown with transmission electron microscopy. At first, an elongated papilla of regeneration forms, probably from the differentiation of dermal fibroblasts. A scale anlage composed of the osseous layer appears in the middle of the papilla, which becomes a regenerating bag. All the surrounding large scleroblasts are involved in scale formation, although later three populations of scleroblasts specialize according to their location around the scale. Superficial scleroblasts flatten when the final thickness of the osseous layer of the scale is attained; the deep scleroblasts are responsible for the formation of the basal plate whereas marginal scleroblasts increase the diameter of the osseous layer of the scale. During scale regeneration, scleroblasts are more numerous and larger than during scale ontogenesis. In particular, deep scleroblasts form a columnar epithelium when the basal plate is laid down, a feature which is not found during scale ontogenesis. Moreover, the regenerated basal plate exhibits an orthogonal “plywood” arrangement that is never seen in the embryonic scale where the “plywood” is of the intermediate type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228438
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...