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  • 1
    Publication Date: 2020-08-05
    Description: Das heutige Leben ist durchdrungen von komplexen Technologien. Ohne Kommunikationsnetze, Internet, Mobilfunk, Logistik, Verkehrstechnik, medizinische Apparate, etc. könnte die moderne Gesellschaft nicht funktionieren. Fast alle dieser Technologien haben einen hohen Mathematikanteil. Der "normale Bürger"' weiss davon nichts, der Schulunterricht könnte dem ein wenig abhelfen. Einige mathematische Aspekte dieser Technologien sind einfach und sogar spielerisch intuitiv zugänglich. Solche Anwendungen, die zusätzlich noch der Lebensumwelt der Schüler zugehören, können dazu genutzt werden, die mathematische Modellierung, also die mathematische Herangehensweise an die Lösung praktischer Fragen, anschaulich zu erläutern. Gerade in der diskreten Mathematik können hier, quasi "nebenbei" mathematische Theorien erarbeitet und Teilaspekte (Definitionen, Fragestellungen, einfache Sachverhalte) durch eigenständiges Entdecken der Schüler entwickelt werden. Wir beginnen mit einigen Beispielen.
    Keywords: ddc:510
    Language: German
    Type: reportzib , doc-type:preprint
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  • 2
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    Publication Date: 2020-08-05
    Description: Den kürzesten Weg in einem Graphen zu finden ist ein klassisches Problem der Graphentheorie. Über einen Vortrag zu diesem Thema beim Tag der Mathematik 2007 von R. Borndörfer kam ich in Kontakt mit dem Konrad-Zuse-Zentrum (ZIB), das sich u.a. mit Wegeoptimierung beschäftigt. Ein Forschungsschwerpunkt dort ist im Rahmen eines Projekts zur Chipverifikation das Zählen von Lösungen, das, wie wir sehen werden, eng mit dem Zählen von Wegen zusammenhängt. Anhand von zwei Fragen aus der Graphentheorie soll diese Facharbeit unterschiedliche Lösungsmethoden untersuchen. Wie bestimmt man den kürzesten Weg zwischen zwei Knoten in einem Graphen und wie findet man alle möglichen Wege? Nach einer Einführung in die Graphentheorie und einer Konkretisierung der Probleme wird zunächst für beide eine Lösung mit auf Graphen basierenden Algorithmen vorgestellt. Während der Algorithmus von Dijkstra sehr bekannt ist, habe ich für das Zählen von Wegen einen eigenen Algorithmus auf der Basis der Tiefensuche entwickelt. Im zweiten Teil der Arbeit wird das Konzept der ganzzahligen Programmierung vorgestellt und die Lösungsmöglichkeiten für Wegeprobleme, die sich darüber ergeben. Schließlich wurden die vorgestellten Algorithmen am Beispiel des S- und U-Bahnnetzes von Berlin implementiert und mit Programmen, die die gleichen Fragen über ganzzahlige Programmierung lösen, verglichen.
    Keywords: ddc:510
    Language: German
    Type: reportzib , doc-type:preprint
    Format: application/pdf
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  • 3
    Publication Date: 2016-06-09
    Description: This paper is intended to be a first step towards the continuous dependence of dynamical contact problems on the initial data as well as the uniqueness of a solution. Moreover, it provides the basis for a proof of the convergence of popular time integration schemes as the Newmark method. We study a frictionless dynamical contact problem between both linearly elastic and viscoelastic bodies which is formulated via the Signorini contact conditions. For viscoelastic materials fulfilling the Kelvin-Voigt constitutive law, we find a characterization of the class of problems which satisfy a perturbation result in a non-trivial mix of norms in function space. This characterization is given in the form of a stability condition on the contact stresses at the contact boundaries. Furthermore, we present perturbation results for two well-established approximations of the classical Signorini condition: The Signorini condition formulated in velocities and the model of normal compliance, both satisfying even a sharper version of our stability condition.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 4
    Publication Date: 2020-08-05
    Description: Most data networks nowadays use shortest path protocols to route the traffic. Given administrative routing lengths for the links of the network, all data packets are sent along shortest paths with respect to these lengths from their source to their destination. In this paper, we present an integer programming algorithm for the minimum congestion unsplittable shortest path routing problem, which arises in the operational planning of such networks. Given a capacitated directed graph and a set of communication demands, the goal is to find routing lengths that define a unique shortest path for each demand and minimize the maximum congestion over all links in the resulting routing. We illustrate the general decomposition approach our algorithm is based on, present the integer and linear programming models used to solve the master and the client problem, and discuss the most important implementational aspects. Finally, we report computational results for various benchmark problems, which demonstrate the efficiency of our algorithm.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 5
    Publication Date: 2020-12-15
    Description: This paper introduces the "line connectivity problem", a generalization of the Steiner tree problem and a special case of the line planning problem. We study its complexity and give an IP formulation in terms of an exponential number of constraints associated with "line cut constraints". These inequalities can be separated in polynomial time. We also generalize the Steiner partition inequalities.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 6
    Publication Date: 2020-08-05
    Description: Testing is the process of stimulating a system with inputs in order to reveal hidden parts of the system state. In the case of non-deterministic systems, the difficulty arises that an input pattern can generate several possible outcomes. Some of these outcomes allow to distinguish between different hypotheses about the system state, while others do~not. In this paper, we present a novel approach to find, for non-deterministic systems modeled as constraints over variables, tests that allow to distinguish among the hypotheses as good as possible. The idea is to assess the quality of a test by determining the ratio of distinguishing (good) and not distinguishing (bad) outcomes. This measure refines previous notions proposed in the literature on model-based testing and can be computed using model counting techniques. We propose and analyze a greedy-type algorithm to solve this test optimization problem, using existing model counters as a building block. We give preliminary experimental results of our method, and discuss possible improvements.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 7
    Publication Date: 2021-08-05
    Description: Starting with the description of the Traveling Salesmen Problem formulation as given by van Vyve and Wolsey in the article Approximate extended formulations'', we investigate the effects of small variations onto the performance of contemporary mixed integer programming solvers. We will show that even minor changes in the formulation of the model can result in performance difference of more than a factor of 1000. As the results show it is not obvious which changes will result in performance improvements and which not.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 8
    Publication Date: 2022-03-14
    Description: Orbitopes can be used to handle symmetries which arise in integer programming formulations with an inherent assignment structure. We investigate the detection of symmetries appearing in this approach. We show that detecting so-called orbitopal symmetries is graph-isomorphism hard in general, but can be performed in linear time if the assignment structure is known.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 9
    Publication Date: 2019-01-29
    Description: Regional hyperthermia is a cancer therapy aiming at heating tumors using phased array applicators. This article provides an overview over current mathematical challenges of delivering individually optimal treatments. The focus is on therapy planning and identification of technical as well as physiological quantities from MR thermometry measurements.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 10
    Publication Date: 2019-05-10
    Description: Reasons for the failure of adaptive methods to deliver improved efficiency when integrating monodomain models for myocardiac excitation are discussed. Two closely related techniques for reducing the computational complexity of linearly implicit integrators, deliberate sparsing and splitting, are investigated with respect to their impact on computing time and accuracy.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 11
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    Publication Date: 2020-08-05
    Description: We investigate the computation of periodic timetables for public transport by mixed integer programming. After introducing the problem, we describe two mathematical models for periodic timetabling, the PERIODIC EVENT SCHEDULING PROBLEM (PESP) and the QUADRATIC SEMI-ASSIGNMENT PROBLEM. Specifically, we give an overview of existing integer programming (IP) formulations for both models. An important contribution of our work are new IP formulations for the PESP based on time discretization. We provide an analytical comparison of these formulations and describe different techniques that allow a more efficient solution by mixed integer programming. In a preliminary computational study, on the basis of standard IP solvers, we compare different formulations for computing periodic timetables. Our results justify a further investigation of the time discretization approach. Typically the timetable is optimized for the current traffic situation. The main difficulty with this approach is that after introducing the new timetable the passengers’ travel behavior may differ from that assumed for the computation. Motivated by this problem, we examine an iterative timetabling procedure that is a combination of timetable computation and passenger routing. We discuss the algorithmic issues of the passenger routing and study properties of the computed timetables. Finally, we confirm our theoretical results on the basis of an own implementation.
    Description: Wir untersuchen die Berechnung von Taktfahrplänen für den öffentlichen Verkehr mit gemischt-ganzzahliger Programmierung (MIP). Im Anschluss an die Problembeschreibung, stellen wir zwei mathematische Modellierungen vor, das PERIODIC EVENT SCHEDULING PROBLEM (PESP) und das QUADRATIC SEMI-ASSIGNMENT PROBLEM. Wichtiger Bestandteil ist ein Überblick über existierende ganzzahlige Formulierungen beider Modelle. Wir entwickeln neue ganzzahlige Formulierungen für das PESP auf der Basis von Zeitdiskretisierung. Diese werden analytisch miteinander verglichen und wir beschreiben verschiedene Techniken, die eine effizientere Lösung der Formulierungen mit gemischt-ganzzahliger Programmierung ermöglichen. In einer ersten Rechenstudie, unter Verwendung gängiger MIP-Löser, vergleichen wir verschiedene ganzzahlige Formulierungen zur Berechnung von Taktfahrplänen. Unsere Ergebnisse rechtfertigen eine weitere Untersuchung des Zeitdiskretisierungsansatzes. In der Regel werden Fahrpläne mit Bezug auf die gegenwärtige Verkehrssituation optimiert. Dies birgt jedoch folgendes Problem. Wenn der neue Fahrplan eingeführt wird, ist es möglich, dass die Passagiere ein anderes Fahrverhalten zu Tage legen, als für die Berechnung des Fahrplans angenommen wurde. Vor diesem Hintergrund behandeln wir ein iteratives Verfahren zur Berechnung von Taktfahrplänen. Dieses ist eine Kombination aus Fahrplanberechnung und Passagierrouting. Neben den algorithmischen Details des Passagierroutings untersuchen wir Eigenschaften der berechneten Fahrpläne. Abschließend bestätigen wir unsere theoretischen Ergebnisse auf Grundlage einer eigenen Implementierung des Verfahrens.
    Keywords: ddc:510
    Language: English
    Type: masterthesis , doc-type:masterThesis
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  • 12
    Publication Date: 2020-08-05
    Description: This paper describes several experiments to explore the options for solving a class of mixed integer nonlinear programming problems that stem from a real-world mine production planning project. The only type of nonlinear constraints in these problems are bilinear equalities involving continuous variables, which enforce the ratios between elements in mixed material streams. A branch-and-bound algorithm to handle the integer variables has been tried in another project. However, this branch-and-bound algorithm is not effective for handling the nonlinear constraints. Therefore state-of-the-art nonlinear solvers are utilized to solve the resulting nonlinear subproblems in this work. The experiments were carried out using the NEOS server for optimization. After finding that current nonlinear programming solvers seem to lack suitable preprocessing capabilities, we preprocess the instances beforehand and use an heuristic approach to solve the nonlinear subproblems. In the appendix, we explain how to add a polynomial constraint handler that uses IPOPT as embedded nonlinear programming solver for the constraint programming framework SCIP. This is one of the crucial steps for implementing our algorithm in SCIP. We briefly described our approach and give an idea of the work involved.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 13
    Publication Date: 2020-08-05
    Description: Dieser kurze Aufsatz zur Algorithmengeschichte ist Eberhard Knobloch, meinem Lieblings-Mathematikhistoriker, zum 65. Geburtstag gewidmet. Eberhard Knobloch hat immer, wenn ich ihm eine historische Frage zur Mathematik stellte, eine Antwort gewusst – fast immer auch sofort. Erst als ich mich selbst ein wenig und dazu amateurhaft mit Mathematikgeschichte beschäftigte, wurde mir bewusst, wie schwierig dieses „Geschäft“ ist. Man muss nicht nur mehrere (alte) Sprachen beherrschen, sondern auch die wissenschaftliche Bedeutung von Begriffen und Symbolen in früheren Zeiten kennen. Man muss zusätzlich herausfinden, was zur Zeit der Entstehung der Texte „allgemeines Wissen“ war, insbesondere, was seinerzeit gültige Beweisideen und -schritte waren, und daher damals keiner präzisen Definition oder Einführung bedurfte. Es gibt aber noch eine Steigerung des historischen Schwierigkeitsgrades: Algorithmengeschichte. Dies möchte ich in diesem Artikel kurz darlegen in der Hoffnung, dass sich Wissenschaftshistoriker dieses Themas noch intensiver annehmen, als sie das bisher tun. Der Grund ist, dass heute Algorithmen viele Bereiche unserer Alltagswelt steuern und unser tägliches Leben oft von funktionierenden Algorithmen abhängt. Daher wäre eine bessere Kenntnis der Algorithmengeschichte von großem Interesse.
    Keywords: ddc:510
    Language: German
    Type: reportzib , doc-type:preprint
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  • 14
    Publication Date: 2016-06-09
    Description: We consider first order optimality conditions for state constrained optimal control problems. In particular we study the case where the state equation has not enough regularity to admit existence of a Slater point in function space. We overcome this difficulty by a special transformation. Under a density condition we show existence of Lagrange multipliers, which have a representation via measures and additional regularity properties.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 15
    Publication Date: 2016-06-09
    Description: The enormous time lag between fast atomic motion and complex pro- tein folding events makes it almost impossible to compute molecular dy- namics on a high resolution. A common way to tackle this problem is to model the system dynamics as a Markov process. Yet for large molec- ular systems the resulting Markov chains can hardly be handled due to the curse of dimensionality. Coarse graining methods can be used to re- duce the dimension of a Markov chain, but it is still unclear how far the coarse grained Markov chain resembles the original system. In order to answer this question, two different coarse-graining methods were analysed and compared: a classical set-based reduction method and an alternative subspace-based approach, which is based on membership vectors instead of sets. On the basis of a small toy system, it could be shown, that in con- trast to the subset-based approach, the subspace-based reduction method preserves the Markov property as well as the essential dynamics of the original system.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 16
    Publication Date: 2021-02-19
    Description: Line planning is an important step in the strategic planning process of a public transportation system. In this paper, we discuss an optimization model for this problem in order to minimize operation costs while guaranteeing a certain level of quality of service, in terms of available transport capacity. We analyze the problem for path and tree network topologies as well as several categories of line operation that are important for the Quito Trolebus system. It turns out that, from a computational complexity worst case point of view, the problem is hard in all but the most simple variants. In practice, however, instances based on real data from the Trolebus System in Quito can be solved quite well, and significant optimization potentials can be demonstrated.
    Keywords: ddc:510
    Language: English
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  • 17
    Publication Date: 2020-08-05
    Description: It is well known that competitive analysis yields too pessimistic results when applied to the paging problem and it also cannot make a distinction between many paging strategies. Many deterministic paging algorithms achieve the same competitive ratio, ranging from inefficient strategies as flush-when-full to the good performing least-recently-used (LRU). In this paper, we study this fundamental online problem from the viewpoint of stochastic dominance. We show that when sequences are drawn from distributions modelling locality of reference, LRU is stochastically better than any other online paging algorithm.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 18
    Publication Date: 2020-12-15
    Description: Die Angebotsplanung im öffentlichen Nahverkehr umfasst die Aufgaben der Netz-, Linien-,Fahr- und Preisplanung. Wir stellen zwei mathematische Optimierungsmodelle zur Linien- und Preisplanung vor. Wir zeigen anhand von Berechnungen für die Verkehrsbetriebe in Potsdam(ViP), dass sich damit komplexe Zusammenhänge quantitativ analysieren lassen. Auf diese Weise untersuchen wir die Auswirkungen von Freiheitsgraden auf die Konstruktion von Linien und die Wahl von Reisewegen der Passagiere, Abhängigkeiten zwischen Kosten und Reisezeiten sowie den Einfluss verschiedener Preissysteme auf Nachfrage und Kostendeckung.
    Keywords: ddc:510
    Language: German
    Type: reportzib , doc-type:preprint
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  • 19
    Publication Date: 2022-03-14
    Description: This article introduces constraint integer programming (CIP), which is a novel way to combine constraint programming (CP) and mixed integer programming (MIP) methodologies. CIP is a generalization of MIP that supports the notion of general constraints as in CP. This approach is supported by the CIP framework SCIP, which also integrates techniques from SAT solving. SCIP is available in source code and free for non-commercial use. We demonstrate the usefulness of CIP on two tasks. First, we apply the constraint integer programming approach to pure mixed integer programs. Computational experiments show that SCIP is almost competitive to current state-of-the-art commercial MIP solvers. Second, we employ the CIP framework to solve chip design verification problems, which involve some highly non-linear constraint types that are very hard to handle by pure MIP solvers. The CIP approach is very effective here: it can apply the full sophisticated MIP machinery to the linear part of the problem, while dealing with the non-linear constraints by employing constraint programming techniques.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 20
    Publication Date: 2016-06-09
    Description: An extended mathematical framework for barrier methods for state constrained optimal control compared to [Schiela, ZIB-Report 07-07] is considered. This allows to apply the results derived there to more general classes of optimal control problems, in particular to boundary control and finite dimensional control.
    Keywords: ddc:510
    Language: English
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  • 21
    Publication Date: 2021-08-05
    Description: In the recent years there has been tremendous progress in the development of algorithms to find optimal solutions for integer programs. In many applications it is, however, desirable (or even necessary) to generate all feasible solutions. Examples arise in the areas of hardware and software verification and discrete geometry. In this paper, we investigate how to extend branch-and-cut integer programming frameworks to support the generation of all solutions. We propose a method to detect so-called unrestricted subtrees, which allows us to prune the integer program search tree and to collect several solutions simultaneously. We present computational results of this branch-and-count paradigm which show the potential of the unrestricted subtree detection.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 22
    Publication Date: 2020-08-05
    Description: Edmonds showed that the so-called rank inequalities and the nonnegativity constraints provide a complete linear description of the matroid polytope. By essentially adding Grötschel's cardinality forcing inequalities, we obtain a complete linear description of the cardinality constrained matroid polytope which is the convex hull of the incidence vectors of those independent sets that have a feasible cardinality. Moreover, we show how the separation problem for the cardinality forcing inequalities can be reduced to that for the rank inequalities. We also give necessary and sufficient conditions for a cardinality forcing inequality to be facet defining.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 23
    Publication Date: 2020-08-05
    Description: The paper describes a method for solution of very large overdetermined algebraic polynomial systems on an example that appears from a classification of all integrable 3-dimensional scalar discrete quasilinear equations $Q_3=0$ on an elementary cubic cell of the lattice ${\mathbb Z}^3$. The overdetermined polynomial algebraic system that has to be solved is far too large to be formulated. A probing' technique which replaces independent variables by random integers or zero allows to formulate subsets of this system. An automatic alteration of equation formulating steps and equation solving steps leads to an iteration process that solves the computational problem.
    Keywords: ddc:510
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  • 24
    Publication Date: 2020-08-05
    Description: An algorithmic method using conservation law multipliers is introduced that yields necessary and sufficient conditions to find invertible mappings of a given nonlinear PDE to some linear PDE and to construct such a mapping when it exists. Previous methods yielded such conditions from admitted point or contact symmetries of the nonlinear PDE. Through examples, these two linearization approaches are contrasted.
    Keywords: ddc:510
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  • 25
    Publication Date: 2021-02-26
    Description: We classify all integrable 3-dimensional scalar discrete affine linear equations $Q_3=0$ on an elementary cubic cell of the lattice ${\mathbb Z}^3$. An equation $Q_3=0$ %of such form is called integrable if it may be consistently imposed on all $3$-dimensional elementary faces of the lattice ${\mathbb Z}^4$. Under the natural requirement of invariance of the equation under the action of the complete group of symmetries of the cube we prove that the only ontrivial(non-linearizable) integrable equation from this class is the well-known dBKP-system.
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  • 26
    Publication Date: 2020-12-11
    Description: The article describes the online mathematics test {\tt http://lie.math.brocku.ca/mathtest}, its typical applications and experiences gathered.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 27
    Publication Date: 2020-08-05
    Description: We introduce (TTPlib), a data library for train timetabling problems that can be accessed at http://ttplib.zib.de. In version 1.0, the library contains data related to 50 scenarios. Most instances result from the combination of macroscopic railway networks and several train request sets for the German long distance area containing Hannover, Kassel and Fulda, short denoted by Ha-Ka-Fu. In this paper, we introduce the data concepts of TTPlib, describe the scenarios included in the library and provide a free visualization tool TraVis.
    Keywords: ddc:510
    Language: English
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  • 28
    Publication Date: 2020-08-05
    Description: The purpose of this paper is twofold. An immediate practical use of the presented algorithm is its applicability to the parametric solution of underdetermined linear ordinary differential equations (ODEs) with coefficients that are arbitrary analytic functions in the independent variable. A second conceptual aim is to present an algorithm that is in some sense dual to the fundamental Euclids algorithm, and thus an alternative to the special case of a Gr\"{o}bner basis algorithm as it is used for solving linear ODE-systems. In the paper Euclids algorithm and the new dual version' are compared and their complementary strengths are analysed on the task of solving underdetermined ODEs. An implementation of the described algorithm is interactively accessible at http://lie.math.brocku.ca/crack/uode.
    Keywords: ddc:510
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  • 29
    Publication Date: 2020-08-05
    Description: This paper proposes a new method for probabilistic analysis of online algorithms that is based on the notion of stochastic dominance. We develop the method for the Online Bin Coloring problem introduced by Krumke et al. Using methods for the stochastic comparison of Markov chains we establish the strong result that the performance of the online algorithm GreedyFit is stochastically dominated by the performance of the algorithm OneBin for any number of items processed. This result gives a more realistic picture than competitive analysis and explains the behavior observed in simulations.
    Keywords: ddc:510
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  • 30
    Publication Date: 2020-12-15
    Description: The optimization of fare systems in public transit allows to pursue objectives such as the maximization of demand, revenue, profit, or social welfare. We propose a non-linear optimization approach to fare planning that is based on a detailed discrete choice model of user behavior. The approach allows to analyze different fare structures, optimization objectives, and operational scenarios involving, e.g., subsidies. We use the resulting models to compute optimized fare systems for the city of Potsdam, Germany.
    Keywords: ddc:510
    Language: English
    Type: reportzib , doc-type:preprint
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  • 31
    Publication Date: 2022-03-14
    Description: Pseudo-Boolean problems generalize SAT problems by allowing linear constraints and a linear objective function. Different solvers, mainly having their roots in the SAT domain, have been proposed and compared,for instance, in Pseudo-Boolean evaluations. One can also formulate Pseudo-Boolean models as integer programming models. That is,Pseudo-Boolean problems lie on the border between the SAT domain and the integer programming field. In this paper, we approach Pseudo-Boolean problems from the integer programming side. We introduce the framework SCIP that implements constraint integer programming techniques. It integrates methods from constraint programming, integer programming, and SAT-solving: the solution of linear programming relaxations, propagation of linear as well as nonlinear constraints, and conflict analysis. We argue that this approach is suitable for Pseudo-Boolean instances containing general linear constraints, while it is less efficient for pure SAT problems. We present extensive computational experiments on the test set used for the Pseudo-Boolean evaluation 2007. We show that our approach is very efficient for optimization instances and competitive for feasibility problems. For the nonlinear parts, we also investigate the influence of linear programming relaxations and propagation methods on the performance. It turns out that both techniques are helpful for obtaining an efficient solution method.
    Keywords: ddc:510
    Language: English
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  • 32
    Publication Date: 2020-08-05
    Description: Millionen von Menschen werden allein in Deutschland täglich von Bussen, Bahnen und Flugzeugen transportiert. Der öffentliche Personenverkehr (ÖV) ist von großer Bedeutung für die Lebensqualität einzelner aber auch für die Leistungsfähigkeit ganzer Regionen. Qualität und Effizienz von ÖV-Systemen hängen ab von politischen Rahmenbedingungen (staatlich geplant, wettbewerblich organisiert) und der Eignung der Infrastruktur (Schienensysteme, Flughafenstandorte), vom vorhandenen Verkehrsangebot (Fahr- und Flugplan), von der Verwendung angemessener Technologien (Informations-, Kontroll- und Buchungssysteme) und dem bestmöglichen Einsatz der Betriebsmittel (Energie, Fahrzeuge und Personal). Die hierbei auftretenden Entscheidungs-, Planungs- und Optimierungsprobleme sind z.T. gigantisch und "schreien" aufgrund ihrer hohen Komplexität nach Unterstützung durch Mathematik. Dieser Artikel skizziert den Stand und die Bedeutung des Einsatzes von Mathematik bei der Planung und Durchführung von öffentlichem Personenverkehr, beschreibt die bestehenden Herausforderungen und regt zukunftsweisende Maßnahmen an.
    Keywords: ddc:510
    Language: German
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  • 33
    Publication Date: 2019-05-10
    Description: Pulse thermography of concrete structures is used in civil engineering for detecting voids, honeycombing and delamination. The physical situation is readily modeled by Fourier's law. Despite the simplicity of the PDE structure, quantitatively realistic numerical 3D simulation faces two major obstacles. First, the short heating pulse induces a thin boundary layer at the heated surface which encapsulates all information and therefore has to be resolved faithfully. Even with adaptive mesh refinement techniques, obtaining useful accuracies requires an unsatisfactorily fine discretization. Second, bulk material parameters and boundary conditions are barely known exactly. We address both issues by a semi-analytic reformulation of the heat transport problem and by parameter identification. Numerical results are compared with measurements of test specimens.
    Keywords: ddc:510
    Language: English
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  • 34
    Publication Date: 2016-06-09
    Description: In this paper we are concerned with the application of interior point methods in function space to gradient constrained optimal control problems, governed by partial differential equations. We will derive existence of solutions together with first order optimality conditions. Afterwards we show continuity of the central path, together with convergence rates depending on the interior point parameter.
    Keywords: ddc:510
    Language: English
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  • 35
    Publication Date: 2016-06-09
    Description: We consider an interior point method in function space for PDE constrained optimal control problems with state constraints. Our emphasis is on the construction and analysis of an algorithm that integrates a Newton path-following method with adaptive grid refinement. This is done in the framework of inexact Newton methods in function space, where the discretization error of each Newton step is controlled by adaptive grid refinement in the innermost loop. This allows to perform most of the required Newton steps on coarse grids, such that the overall computational time is dominated by the last few steps. For this purpose we propose an a-posteriori error estimator for a problem suited norm.
    Keywords: ddc:510
    Language: English
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  • 36
    Publication Date: 2020-08-05
    Description: Ticket pricing in public transport usually takes a welfare or mnemonics maximization point of view. These approaches do not consider fairness in the sense that users of a shared infrastructure should pay for the costs that they generate. We propose an ansatz to determine fair ticket prices that combines concepts from cooperative game theory and integer programming. An application to pricing railway tickets for the intercity network of the Netherlands demonstrates that, in this sense, prices that are much fairer than standard ones can be computed in this way.
    Keywords: ddc:510
    Language: English
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  • 37
    Publication Date: 2014-02-26
    Description: We present a second order sharp interface finite volume method for the solution of the three-dimensional poisson equation with variable coefficients on Cartesian grids. In particular, we focus on interface problems with discontinuities in the coefficient, the source term, the solution, and the fluxes across the interface. The method uses standard piecewiese trilinear finite elements for normal cells and a double piecewise trilinear ansatz for the solution on cells intersected by the interface resulting always in a compact 27-point stencil. Singularities associated with vanishing partial volumes of intersected grid cells are removed by a two-term asymptotic approach. In contrast to the 2D method presented by two of the authors in [M.~Oevermann, R.~Klein: A Cartesian grid finite volume method for elliptic equations with variable coefficients and embedded interfaces, J.~Comp.~Phys.~219 (2006)] we use a minimization technique to determine the unknown coefficients of the double trilinear ansatz. This simplifies the treatment of the different cut-cell types and avoids additional special operations for degenerated interface topologies. The resulting set of linear equations has been solved with a BiCGSTAB solver preconditioned with an algebraic multigrid. In various testcases -- including large coefficient ratios and non-smooth interfaces -- the method achieves second order of accuracy in the L_inf and L_2 norm.
    Keywords: ddc:510
    Language: English
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  • 38
    Publication Date: 2020-08-05
    Description: Given a combinatorial optimization problem and a subset $N$ of natural numbers, we obtain a cardinality constrained version of this problem by permitting only those feasible solutions whose cardinalities are elements of $N$. In this paper we briefly touch on questions that addresses common grounds and differences of the complexity of a combinatorial optimization problem and its cardinality constrained version. Afterwards we focus on polytopes associated with cardinality constrained combinatorial optimization problems. Given an integer programming formulation for a combinatorial optimization problem, by essentially adding Grötschel's cardinality forcing inequalities, we obtain an integer programming formulation for its cardinality restricted version. Since the cardinality forcing inequalities in their original form are mostly not facet defining for the associated polyhedra, we discuss possibilities to strengthen them.
    Keywords: ddc:510
    Language: English
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  • 39
    Publication Date: 2020-08-05
    Description: This survey concerns optimization problems arising in the design of survivable communication networks. It turns out that such problems can be modeled in a natural way as non-compact linear programming formulations based on multicommodity flow network models. These non-compact formulations involve an exponential number of path flow variables, and therefore require column generation to be solved to optimality. We consider several path-based survivability mechanisms and present results, both known and new, on the complexity of the corresponding column generation problems (called the pricing problems). We discuss results for the case of the single link (or node) failures scenarios, and extend the considerations to multiple link failures. Further, we classify the design problems corresponding to different survivability mechanisms according to the structure of their pricing problem. Finally, we show that almost all encountered pricing problems are hard to solve for scenarios admitting multiple failures.
    Keywords: ddc:510
    Language: English
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  • 40
    Publication Date: 2021-02-19
    Description: We introduce an optimization model for the line planning problem in a public transportation system that aims at minimizing operational costs while ensuring a given level of quality of service in terms of available transport capacity. We discuss the computational complexity of the model for tree network topologies and line structures that arise in a real-world application at the Trolebus Integrated System in Quito. Computational results for this system are reported.
    Keywords: ddc:510
    Language: English
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  • 41
    Publication Date: 2021-02-19
    Description: Line planning is an important step in the strategic planning process of a public transportation system. In this paper, we discuss an optimization model for this problem in order to minimize operation costs while guaranteeing a certain level of quality of service, in terms of available transport capacity. We analyze the problem for path and tree network topologies as well as several categories of line operation that are important for the Quito Trolebus system. It turns out that, from a computational complexity worst case point of view, the problem is hard in all but the most simple variants. In practice, however, instances based on real data from the Trolebus System in Quito can be solved quite well, and significant optimization potentials can be demonstrated.
    Keywords: ddc:510
    Language: English
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  • 42
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 6-8 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 43
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 10-13 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 44
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 435-443 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many antimicrobial agents are available for commercial use, but only a few are truly sporicidal and can be used as chemosterilizers. The action of ethylene oxide, propylene oxide, and β-propiolactone is well documented. Strong acids, e.g., hydrochloric acid, or alkalis may be used as chemosterilizers but their use is extremely limited. The synthetic phenolics accompanied by boiling were recommended, but heat cannot always be employed. Chlorine and iodine have been used in higher concentrations. The use of 8% formaldehyde or 20% formalin was suggested by Spaulding.17 Other aldehydes possess antimicrobial potency. According to work performed in our laboratories, the sporicidal activity of certain alcoholic, saturated dialdehyde solutions equalled or surpassed that of formaldehyde. These included glyoxal, succinaldehyde, and glutaraldehyde. Aqueous alkaline glutaraldehyde solutions killed the most resistant bacterial spores, e.g., B. subtilis and Cl. tetani, within a few hours (Borick1,2). Glutaraldehyde, a 5-carbon dialdehyde, was shown to be a chemosterilizer when tested by various methods, destroying bacteria, including M. tuberculosis, fungi, and viruses. Acid glutaraldehyde solutions stored at room temperature are highly stable, whereas alkaline solutions show a significant change in pH and a diminution of glutaraldehyde concentration on alkalinization. For this reason, fresh (not over 2 weeks old) alkaline glutaraldehyde solutions can be used as chemosterilizers.
    Additional Material: 1 Ill.
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  • 45
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 3-6 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 46
    Electronic Resource
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 54-58 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 47
    Electronic Resource
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 245-268 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to find effective methods to isolate microorganisms that excrete large amounts of amino acids, a number of mutants of Escherichia coli ATCC 4157 were prepared and characterized. The majority were isolated for resistance to amino acid analogs. The penicillin method was also employed to select potential producer strains devoid of a biosynthetic enzyme in one case and a catabolic enzyme (tryptophanase) in another. Both of these enzymes were suspected of reducing the yield of an excerted amino acid. The identification of amino acid excreting colonies was aided by the use of pigmented auxotrophic test bacteria.Amino acid analog resistance was frequently found to increase amino acid production. In particular, excretion of valine and glutamic acid could be achieved with comparative ease. Conditions of culture were of extreme importance for the amount and kind of amino acid produced. Under certain conditions a norvaline-resistant strain and even better a leucine-requiring derivative of it excreted more than 2 mg./ml. of valine into the culture medium. The acetolactate-forming enzyme of this strain was not repressible by leucine in contrast to the same enzyme in the wild type. Reversal of the growth inhibitory effects of amino acid analogs by amino acids was studied on agar plates. This method gave too complex results to be a simple guide in the selection of analogs suitable for the isolation of a particular type of production mutant.
    Additional Material: 8 Tab.
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  • 48
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 129-132 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A procedure for sterilization of microbiological media with β-propiolactone has been developed. Special attention was paid to the maintenance of mild conditions to enable the treatment of media sensitive to high temperature or low pH. The maximum temperature allowed was 40°C. and automatic neutralization of acid produced during hydrolysis was effected by the use of titration unit. The apparatus could be used for several successive sterilization cycles without disconnection.
    Additional Material: 1 Ill.
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  • 49
    Electronic Resource
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965) 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 50
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 8-10 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 51
    Electronic Resource
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 13-16 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 52
    Electronic Resource
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 21-29 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 53
    Electronic Resource
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 335-342 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A laboratory process for the isolation of acid soluble nucleotides from bacteria has been scaled-up. Escherichia coli was grown in 220-l. batches, harvested by centrifugation, and extracted with cold trichloracetic acid. The nucleotides in the extract were separated by adsorption onto a Dowex-1 ion exchange resin column followed by elution with dilute hydrochloric acid and lithium chloride. After concentration of the effluent, the lithium chloride was removed by extraction with organic solvents. The overall yield of nucleotides was 75-80%. This elution system has also been used for the separation of nucleotides from bakers' yeast extracts.
    Additional Material: 2 Ill.
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  • 54
    Electronic Resource
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 387-404 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Evidence for generation of the plateau in oxygen uptake during exertion of carbonaceous BOD by pure cultures was sought by making long term Warburg studies using glucose and phthalic acid as substrates. One organism, tentatively identified as Escherichia intermedia, of the 57 tested, exhibited a plateau. Detailed studies on this organism indicated that generation of the plateau depended upon the type of substrate and to some extent upon the initial cell concentration employed, but not upon substrate concentration. Oxygen utilization during the second stage was accompanied by metabolism of secondary extracellular carbon source(s) produced by the cells during metabolism of the original extracellular carbon source (glucose) in the first phase of O2 uptake. The secondary substrate was registered as volatile acids. Selective inhibition of protein synthesis at various times during oxygen uptake led to the conclusion that the plateau occurred because of the need for an induction period before the secondary substrate could be metabolized. Using this organism, it was also found that a plateau could be generated during endogenous respiration. This secondary O2 utilization was accompained by uptake of organic materials excreted into the medium by the cells during metabolism of endogenous carbon sources.
    Additional Material: 7 Ill.
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  • 55
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A procedure described for the partial purification of suspensions of the organisms of psittacosis utilizes tryptic digestion, calcium chloridedextran sulfate precipitation, and centrifugation through a sucrose barrier. More than 40% of the organisms in the original suspension are recovered in 80% of the original volume, with approximately 95% of the lipids and 85% of the proteins removed. This method is suggested as a preliminary purification procedure in laboratories desiring relatively large amounts of purified agent for studies on metabolism, physical properties, or antigenicity of the organism. Significant aspects of the investigations leading to the selection of the procedures are included.
    Additional Material: 3 Tab.
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  • 56
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    Biotechnology and Bioengineering 7 (1965), S. 455-470 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The response of heterogeneous populations to shockloading was studied under a variety of operational conditions using synthetic wastes consisting of glycerol, glucose, and a mixture of glucose and glycerol. In all experiments, the cells were acclimated to glycerol. The addition of glucose as a shockloading at various times during the aeration period caused an immediate cessation of glycerol metabolism, and glycerol was not again actively metabolized until all glucose had been assimilated. Experiments conducted at various initial sludge concentrations showed that this effect was not dependent upon biological solids level. Glycerol metabolism was also blocked when glucose was applied as a shockloading to a system operating under severe nitrogen deficiency, further reenforcing the conclusion that there is a blockage mechanism for catabolic pathways which operates to suppress enzyme function rather than enzyme synthesis. It was also found that considerable amounts of metabolic intermediates or end products were released during glucose metabolism regardless of the presence or absence of glycerol. In systems containing a source of nitrogen, these products were metabolized after dissimilation of glucose. In resting cell suspensions, the metabolic intermediates were not subsequently removed, indicating that their metabolism depended upon the synthesis of new enzymes. Using old cell sludge, concurrent rather than sequential removal of glycerol and glucose was observed. The results using two component (C6—C3) carbon sources were in general the same as for C6—C6 synthetic wastes. The results provide further evidence for the generality of sequential substrate removal, and suggest that the metabolite suppressing catabolism of glycerol lies below the triose level.
    Additional Material: 7 Ill.
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  • 57
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 529-553 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A 1-l. fermentor was designed and tested for use as a tissue-culture vessel. It features a temperature control device, impeller agitation without the necessity of a shaft seal, and a means of measuring, recording, and controlling both pH and oxidation-reduction potential (ORP). Tests have shown the ORP to change fairly rapidly with impeller speed variations under conditions of a continuous carbon dioxide-air overlay. Working with strain L mouse fibroblasts (Earle), cell counts of more than 1.25 ×106 ml., without centrifugation and medium renewal, were achieved, and cell counts were maintained above 1 ×106 for more than 30 hr. With the vessel studied, pH control was ±0.05, the ORP control was ±10 mV. Controlled environments for tissue-cell metabolic studies are entirely feasible with this system.
    Additional Material: 7 Ill.
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  • 58
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    Biotechnology and Bioengineering 7 (1965), S. 343-354 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The oxygen demand of Penicillium chrysogenum culture was supplied by an automatic aeration control system on the basis of the actual respiration of the cells. The simultaneous use of the automatic aeration apparatus and a turbomixer of great shear stress revealed that some effects of agitation are independent of aeration. These effects of agitation are manifested in two ways: (1) in the increased break down of the cell clumps, thus assuring large free cell surfaces for contact with the substrates; and (2) in the increased mixing effect, which assures a continuous mass transfer towardes the free cell surfaces. These effects of the agitation can improve the yield when the O2 level is maintained near to the saturation value. By means of an automatic aeration control system, the influence of carbon dioxide on the metabolism of hyphae and the production of penicillin was found to be demonstrably inhibitory when the dissolved oxygen was above the critical concentration in the culture liquid. This result is supporting evidence for the assumption that aeration is necessary to biosynthetic processes in two equally important ways: (1) to maintain the oxygen level above the critical value; and (2) to assure ventilation, by which the carbon dioxide level may be kept below its inhibitory critical value.
    Additional Material: 4 Ill.
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  • 59
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 405-415 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The formation of gibberellic acid in single-stage continuous cultures was studied. Stirred fermenters of 3 and 20-l. working volumes were used. Maximum output of gibberellic acid was obtained at a holding time of 200 hr. The rate of formation, calculated on the basis of mycelial nitrogen, was comparable with the highest values reported for batch cultures.
    Additional Material: 3 Ill.
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  • 60
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new type of mixer that utilizes the Bernoulli effect has been found highly useful for providing gentle agitation in suspension cultures of fragile mammalian cells in culture volumes up to 6 l.
    Additional Material: 3 Ill.
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  • 61
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    Biotechnology and Bioengineering 7 (1965), S. 327-334 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A process has been developed whereby arginine decarboxy-oxidase (ADO) can be produced by growing Streptomyces griseus in submerged form in 20-l. and 200-l. tank fermentors. A medium containing salts, corn steep, glucose, or starch is used. With addition of 0.02% arginine and with limited aeration, a high yield has been obtained.
    Additional Material: 2 Ill.
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  • 62
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An exploratory study is described on the use of a biphasic culture technique for production of toxin by C. tetani. The biphasic system used was a combination of dextran and poly(ethylene glycol) (PEG) in the presence of a protein-free medium. The system supported good growth and gave a favorable phase ratio (top/bottom) of 15:1. The majority of the bacterial cells were in the bottom dextran phase, while the greater part of the toxin was in the upper PEG-medium phase. Toxin yields from a typical experiment were 109 mouse IP MLD/ml. of upper phase filtrate. The biphasic culture system was also adaptable to continuous culture, with approximately similar toxin levels found in the upper phase. The appearance of the clostridial cells in older cultures suggested the possibility of protoplast formation, perhaps stabilized by the polymers present. In vitro toxin titration (Lf) was inhibited by the presence of the polymers. Bacillus anthracis also grew well in the biphasic system and elaborated protective antigen, primarily into the upper phase.
    Additional Material: 6 Ill.
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  • 63
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    Biotechnology and Bioengineering 7 (1965) 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 64
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    Biotechnology and Bioengineering 7 (1965), S. 471-490 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The growth of Thiobacillus Thiooxidans, utilizing sulfur in three media, was studied by observing changes in halfcell emf, bacterial cell count, and acid production, all as a function of time. A comparison of the biological halfcell emf with comparable control halfcells reveals that T. thiooxidans makes an electrochemical contribution to halfcell voltage. A change from the more complex medium of Skerman's mineral salts to ATCC allowed a clearer delineation of the ability of T. thiooxidans to make an electrochemical contribution. Reproducible biological halfcell emf's were obtained when the ferrous sulfate was removed from the ATCC medium. One halfcell, consisting of T. thiooxidans utilizing sulfur in ATCC, was observed over a 111-day period. During this time, the initial halfcell voltage of -0.35 V. decreased to a value of -0.64 V. (hydrogen emf series). T. thiooxidans, in utilizing sulfur, produces only sulfate ion, thereby simplifying the identification of an electrochemical contribution during growth.
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  • 65
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    Biotechnology and Bioengineering 7 (1965), S. 491-506 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The electrochemical activity of the individual chemicals in the nutrient medium for growth of Thiobacillus thiooxidans was studied along with the effect of the gases in equilibrium with their solutions. Several chemicals were active individually; however, the magnitudes, as measured by changes in half-cell potential, were less than that observed when T. thiooxidans was present in their composite mixture. Sterilized Skerman's mineral salts and the American Type Culture Collection (without ferrous sulfate) media were not sensitive electrochemically to changes from pure oxygen to nitrogen atmospheres. When T. thiooxidans was present in these media, the biological half-cell emf became sensitive to changes in the oxygen content of the atmosphere in equilibrium with the organism and nutrient. The ability of T. thiooxidans to make an electrochemical contribution, as registered by a platinum electrode, is substantiated further by these investigations.
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  • 66
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    Biotechnology and Bioengineering 7 (1965), S. 72-74 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 67
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    Biotechnology and Bioengineering 7 (1965), S. 74-75 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 68
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    Biotechnology and Bioengineering 7 (1965), S. 70-72 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 69
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    Biotechnology and Bioengineering 7 (1965), S. 29-51 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 70
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    Biotechnology and Bioengineering 7 (1965), S. 60-65 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 71
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    Biotechnology and Bioengineering 7 (1965), S. 171-175 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method is described for the isolation of bacterial polysaccharide B-1459 from aqueous dispersion as a calcium hydroxide complex. The polysaccharide is liberated in fibrous form from the complex by means of hydrochloric acid in methanol solution. Overall recovery of the polysaccharide from aqueous dispersion is 85%. Direct conversion of the insoluble calcium hydroxide complex to aqueous polysaccharide solution appears to be a low-cost procedure for preparing viscous solutions for industrial use.
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  • 72
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    Biotechnology and Bioengineering 7 (1965), S. 215-227 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of operating temperature upon relative stripping of a two component (ethanol-water) mixture by dry air, with the aid of a previously derived equation,1 is considered. The variations encountered in the relative humidity of air sparged to fermentors are discussed. A general equation is developed for the stripping of a more volatile component from a solution in water by wet air. The theoretical results derived from this equation are tested experimentally at one particular level of prehumidity of the air sparged to an ethanol-water system.
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  • 73
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    Biotechnology and Bioengineering 7 (1965), S. 279-283 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Continuous cultures of some heterotrophic Spirilli (Sp. serpens, Sp. curvatum, Sp. sp.) exhibit threshold concentrations of lactate, the growth limiting carbon and energy source, around 15 mg./l. This value corresponds to a threshold population density of 0.92 mg. dry weight/l. at a dilution rate of D = 0.185 hr.-1 (= 0.5 maximum growth rate). The minimum population density, which is regarded as equivalent to the starter population in batch culture, was dependent on the growth rate and the redox potential. The existence of minimum populations and the pronounced effect of population density on growth at low nutrient levels seem to be widespread phenomena closely related to growth under suboptimal conditions.
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  • 74
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    Biotechnology and Bioengineering 7 (1965), S. 322-325 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 75
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    Biotechnology and Bioengineering 7 (1965), S. 309-319 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pseudomonas aeruginosa NCTC 5940 was grown in an aerated mineral salts medium with pure octadecane as sole carbon source, both in batch and continuous culture experiments. Carbon and nitrogen balances were made under different conditions. It was found that the only significant products were fresh cell tissue and carbon dioxide, although traces of several fatty acids were detected.
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  • 76
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    Biotechnology and Bioengineering 7 (1965), S. 321-322 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 77
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    Biotechnology and Bioengineering 7 (1965) 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 78
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    Biotechnology and Bioengineering 7 (1965), S. 16-19 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 79
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    Biotechnology and Bioengineering 7 (1965), S. 51-54 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 80
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    Biotechnology and Bioengineering 7 (1965), S. 65-69 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 81
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    Biotechnology and Bioengineering 7 (1965), S. 161-169 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method to make purified polysaccharide synthesized exocellularly from cereal carbohydrates by the bacterium Xanthomonas campestris NRRL B-1459 and a characterization of its properties have been reported previously by this Laboratory. Because of increasing commercial interest in a less purified polymer, we have extended our work to include production of a lower cost industrial-grade product. Fermentation of media containing 2.25% corn sugar, seeded with 5% inoculum of X. campestris NRRL B-1459 and cultured aerobically at 82°F., is complete in 96 hr. The viscous fermented broth contains about 1.5% polymer. A tan product containing approximately 60% polymer and having good viscosity characteristics is obtained by drum drying the fermented broth at steam pressures below 40 p.s.i.g, 287°F. Drying at higher temperatures adversely affects viscosity. A good product is also obtained by spray drying. Cost estimates indicate that 5 million lb./yr. of dried crude solids could be produced for 37 cents/lb. by drum drying or for 41 cents a pound by spray drying.
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  • 82
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    Biotechnology and Bioengineering 7 (1965), S. 199-214 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A theoretical approach to the prediction of stripping or accumulation of minor components in solution with water by a sparged stream of dry air bubbles is developed and tested experimentally for two model systems, containing 1 mole-% respectively, of ethanol, to represent situations where the minor component is more volatile than water, and of acetic acid, to represent the reverse. Close agreement between theory and practice is achieved in the former case, where an overall reduction in the liquid phase concentration of the minor component occurs, while in the latter, where overall accumulation occurs, there is some discrepancy. Considerations for an extension of the study are included.
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  • 83
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    Biotechnology and Bioengineering 7 (1965), S. 269-278 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The addition of potassium ferrocyanide to the molasses substrate (mash) used in the citric acid fermentation had little or no effect on the total carbon, nitrogen, or phosphorus content of the substrate but reduced the ash content by 1-4% depending on the type and crop year of molasses. Eighteen of the 21 metals identified in beet molasses by spectrographic analysis were precipitated in part by the treatment. The metals known to interfere with citric acid production, particularly manganese and iron, were those most efficiently precipitated. At mash temperatures of 80°C. and approximately 100°C., precipitation was completed within 15 min. after ferrocyanide addition and the reductions in the soluble mineral content in each case were similar. At 25°C. the precipitation reactions occurred but required more than 50 hr. to complete. Significantly more total mineral and more iron, calcium, and copper were precipitated at pHs 4 and 6 than at pH 8; manganese precipitation, however, was not affected by these pH changes.
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  • 84
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    Biotechnology and Bioengineering 7 (1965), S. 101-128 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bei der kontinuierlichen Züchtung von Mikroorganismen ist die zuverlässige Aufrechterhaltung des stationären Zustandes die Grundbedingung für die erfolgreiche Untersuchung der biologischen Probleme. Auftretende Instabilitäten können apparativen oder biologischen Ursprunges sein; eine einwanddfrei funktionierende Ausrüstung ist daher bei der Einführung der Kontinuität primäres Erfordernis. Es wird auf die wichtigsten Ursachen, welche zu Instabilitäten führen können, eingegangen und eine Laborapparatur beschrieben, welche eine Basisausrüstung umfasst, die speziell für hohe Betriebssicherheit und Einfachheit der Bedienung ausgelegt wurde. Besondere Aufmerksamkeit wurde der Konstanz des Zuflusses f des Mediums, und des arbeitenden Volumens v, sowie der sicheren Ausschaltung von Infektionen durch Verwendung sterilisierbarer pH-Elektroden und eines Membranverschlusses geschenkt.
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  • 85
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    Biotechnology and Bioengineering 7 (1965), S. 555-558 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 86
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    Biotechnology and Bioengineering 7 (1965), S. 59-60 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 87
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    Biotechnology and Bioengineering 7 (1965), S. 139-159 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A small fraction, about 0.05%, of the microorganisms in milk are resistant to pressure to at least 150,000 p.s.i. The pressure-resistant microorganisms were shown to be mainly bacterial spores. Some of the pressure-resistant organisms were identified. The lethal effect of pressure is more pronounced in the solid phase than in the liquid phase of water. B. subtilis was found to be capable of surviving solid-phase transitions from Ice II, III, and V to Ice I. The lethal effect of high pressure in the liquid phase of water was found not to be counteracted by an increase in temperature. The pressure resistance of B. subtilis was found to be maximum around neutral or slightly basic pH. The damaging effect of low and high pH are counteracted by sodium chloride and glucose. It is suggested that the primary mechanism of protein denaturation by pressures above 30,000 p.s.i. is ionization and formation of ionic bonds between charged groups on proteins, altering their solubility.
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  • 88
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    Biotechnology and Bioengineering 7 (1965), S. 177-198 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Steam corrosion and steam corrosion inhibition of dental and surgical instrument materials during autoclave sterilization have been investigated. The corrosion tests were performed on carbon steel test samples and on round dental burrs. Cyclohexylamine or decylamine were used as corrosion inhibitors, added to the “feed water,” i.e., deionized water, to a concentration of 0.1%. Before the corrosion experiment the surfaces of the test materials were standardized and calibrated by means of ultrasonic treatment. After the experiment the corrosion products were removed from the test samples or burrs using the same ultrasonic cleaning. Deionized water was used as cleaning liquid, and was then analyzed for the amount of Fe dissolved. The amount of corrosion was expressed as μg. Fe/cm.2 sample surface area or μg. Fe/burr. The results show that considerable corrosion occurs when carbon steels are exposed to steam during autoclaving, but if cyclohexylamine or decylamine is added to the steam under the otherwise unchanged experimental conditions the total corrosion was reduced by 96-99%. No cytotoxic effect on HeLa cells could be detected with surface products possibly containing traces of amine and/or amine salts - nor with corrosion products alone - when these products were removed from the test materials by means of ultrasonic cleaning.
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  • 89
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    Biotechnology and Bioengineering 7 (1965), S. 517-528 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A substrain of Bacillus cereus 569/H produced above 10,000 units of penicillinase/ ml. when grown in a pilot-plant fermentor using a medium containing Casamino acids techn. (Difco) or N-Z-Amine type B (Sheffield), and salts. Simplified purification and concentration procedures give an overall yield of 50-65% enzyme. The freeze-dried enzyme preparation had a good storage stability in vacuumsealed ampules kept at 4, 30, and 37°C. In vials containing air in the head space, partial inactivation occurred in two months at 30 and 37°C. The freezedried preparation showed satisfactory performance in the production of yoghurt fermented milk.
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    Biotechnology and Bioengineering 7 (1965), S. 76-85 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 91
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    Biotechnology and Bioengineering 7 (1965), S. 85-90 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 92
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    Biotechnology and Bioengineering 7 (1965), S. 91-100 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An automatic aeration controller was constructed to assure the optimal amount of oxygen for aerobic biosynthetic processes. A platinum electrode and a KCl bridge for the calomel electrode were inserted hermetically into the fermentor and were sterilized with the culture medium. The electrode potential developed at the surface of the Pt electrode continuously indicated the actual oxygen concentration of the medium. This served as the controlled variable of the system. The concentration of dissolved oxygen resulted from the actual demand and supply of the microorganism. The electrode potential, which was the measured variable of the process, operated a closed-loop automatic aeration system. The controller activated an air inlet valve in order to balance the controlled variable. The automatic controller operated in fermentors of industrial scale for long periods in a satisfactory manner.
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  • 93
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    Biotechnology and Bioengineering 7 (1965), S. 133-137 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In a study of fermentation methods of producing amphotericin B-14C, a variety of C-14 labeled precursors were added to cultures of the amphotericin-B producing streptomycete growing in a glucose-cottonseed meal medium. Acetate-14C and propionate-14C were efficiently incorporated into the amphotericin-B while formate-14C, glucose-U-14C and methionine-14CH3 were not.
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    Biotechnology and Bioengineering 7 (1965) 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 95
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    Biotechnology and Bioengineering 7 (1965), S. 229-243 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of the gluconic acid fermentation have been studied at pH 5.8 Pseudomonas ovalis B-1486 was used as the fermenting organism. D-Gluconolactone was found as an intermediate in the fermentation and accumulated at times in large amounts. When this occurred, hydrolysis of the lactone was found to be the rate limiting reaction. This can be, under certain conditions, a poor fermentation in which to study oxygen transfer limiting conditions. Further, it is impossible to relate batch and continuous kinetic data for this fermentation unless the lactone hydrolysis reaction is taken into account.
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  • 96
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    Biotechnology and Bioengineering 7 (1965), S. 285-293 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: With a view to preparing substitutes for liver or other animal protein hydrolysates used in the treatment of protein malnutrition, a process has been developed based on sesame and mustard cakes as the starting materials. The laboratory process has been successfully scaled up to pilot plant production to compute tentative costing schedule. Essentially the process consists in defatting the cake, isolating the protein by peptization and isoelectric precipitation, enzymatically digesting the protein isolate by papain, and concentrating the digest under reduced pressure. The final product is a light brown fluffy powder, rich in almost all the essential amino acids. Growth experiments with rats have indicated that the product is comparable to commercial casein although supplementation with lysine could further enhance its biological value.
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  • 97
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    Biotechnology and Bioengineering 7 (1965), S. 295-308 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Large cultures of microscopic, unicellular algae have been proposed as a means of maintaining a life-supporting atmosphere in a closed, manned system. To achieve vigorous growth of the algal culture it is necessary to subject individual algae alternately to short periods of high intensity light and darkness. One of the means suggested for obtaining a favorable light-dark sequence for photosynthesis is to cause turbulence in a closed channel on which light is incident. Since light is rapidly attenuated in a dense suspension, there will be illuminated regions adjacent to the channel walls and a dark central core. The random motions of turbulence normal to the direction of flow would move the algae alternately from the illuminated regions to the dark region and back again. This paper indicates a method for analyzing the motion of algae into and out of the illuminated region of a channel formed by flat, parallel, transparent plates, with light incident on the plates. Matching of a probability model with a diffusion model makes it possible to estimate the light-dark sequence which could be achieved by turbulence. The results indicate that favorable sequences by this mechanism are unlikely.
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    Biotechnology and Bioengineering 7 (1965), S. 367-386 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The construction of a “Porton type” chemostat of 8-l. working volume, based on the New Brunswick Scientific Co., Inc., Model F-14 Fermentor, is detailed. Instrumentation for temperature, pH, and foam control, and for medium supply are described and operational problems discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 99
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 445-446 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 100
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 417-434 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper describes the design and operation of an industrial type culture system for the submerged growth of BHK 21 cells at a volume of 30 l. Using a modified Eagle's medium and with the culture controlled at pH 7.4 ± 0.05 and at a temperature of 35 ± 0.25°C., the cells grew from 0.5 × 106 to about 2.5 × 106 viable cells/ml. in 50 hr. at stirrer speeds of 330 and 460 rpm. The significance of certain aspects of design and operation of a culture system of this type is discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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