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  • 1
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    Vickrey Auctions for Railway Tracks (2008)
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    Publikationsdatum: 2020-08-05
    Beschreibung: We consider an auction of slots to run trains through a railway network. In contrast to the classical setting for combinatorial auctions, there is not only competition for slots, but slots can mutually exclude each other, such that general conflict constraints on bids arise. This turns the winner determination problem associated with such an auction into a complex combinatorial optimization problem. It also raises a number of auction design questions, in particular, on incentive compatibilty. We propose a single-shot second price auction for railway slots, the Vickrey Track Auction (VTA). We show that this auction is incentive compatible, i.e., rational bidders are always motivated to bid their true valuation, and that it produces efficient allocations, even in the presence of constraints on allocations. These properties are, however, lost when rules on the submission of bids such as, e.g., lowest bids, are imposed. Our results carry over to generalized" Vickrey auctions with combinatorial constraints.
    Schlagwort(e): ddc:000
    Sprache: Englisch
    Materialart: reportzib , doc-type:preprint
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  • 2
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    Balancing Efficiency and Robustness – A Bi-criteria Optimization Approach to Railway Track Allocation (2008)
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    Publikationsdatum: 2020-08-05
    Beschreibung: Technical restrictions and challenging details let railway traffic become one of the most complex transportation systems. Routing trains in a conflict-free way through a track network is one of the basic scheduling problems for any railway company. This article focuses on a robust extension of this problem, also known as train timetabling problem (TTP), which consists in finding a schedule, a conflict free set of train routes, of maximum value for a given railway network. However, timetables are not only required to be profitable. Railway companies are also interested in reliable and robust solutions. Intuitively, we expect a more robust track allocation to be one where disruptions arising from delays are less likely to be propagated causing delays of subsequent trains. This trade-off between an efficient use of railway infrastructure and the prospects of recovery leads us to a bi-criteria optimization approach. On the one hand we want to maximize the profit of a schedule, that is more or less to maximize the number of feasible routed trains. On the other hand if two trains are scheduled as tight as possible after each other it is clear that a delay of the first one always affects the subsequent train. We present extensions of the integer programming formulation in [BorndoerferSchlechte2007] for solving (TTP). These models can incorporate both aspects, because of the additional track configuration variables. We discuss how these variables can directly be used to measure a certain type of robustness of a timetable. For these models which can be solved by column generation techniques, we propose so-called scalarization techniques, see [Ehrgott2005], to determine efficient solutions. Here, an efficient solution is one which does not allow any improvement in profit and robustness at the same time. We prove that the LP-relaxation of the (TTP) including an additional $\epsilon$-constraint remains solvable in polynomial time. Finally, we present some preliminary results on macroscopic real-world data of a part of the German long distance railway network.
    Schlagwort(e): ddc:000
    Sprache: Englisch
    Materialart: reportzib , doc-type:preprint
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  • 3
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    Simulations of QCD in the Era of Sustained Tflop/s Computing (2008)
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    Publikationsdatum: 2016-06-30
    Beschreibung: The latest machine generation installed at supercomputer centres in Germany offers a peak performance in the tens of Tflop/s range. We study performance and scaling of our quantum chromodynamics simulation programme BQCD that we obtained on two of these machines, an IBM Blue Gene/L and an SGI Altix 4700. We compare the performance of Fortran/MPI code with assembler code. The latter allows to exploit concurrency at more levels, in particular in overlapping communication and computation as well as prefetching data from main memory.
    Schlagwort(e): ddc:000
    Sprache: Englisch
    Materialart: reportzib , doc-type:preprint
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  • 4
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    The minimization of an L^{\infty}-functional subject to an elliptic PDE and state constraints (2008)
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    Publikationsdatum: 2016-06-09
    Beschreibung: We study the optimal control of a maximum-norm objective functional subject to an elliptic-type PDE and pointwise state constraints. The problem is transformed into a problem where the non-differentiable L^{\infty}-norm in the functional will be replaced by a scalar variable and additional state constraints. This problem is solved by barrier methods. We will show the existence and convergence of the central path for a class of barrier functions. Numerical experiments complete the presentation.
    Schlagwort(e): ddc:000
    Sprache: Englisch
    Materialart: reportzib , doc-type:preprint
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  • 5
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    Mehr Mathematik wagen in der Medizin (2008)
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    Publikationsdatum: 2020-11-16
    Beschreibung: Der Artikel gibt einen Einblick in das reiche Feld der Zusammenarbeit zwischen Mathematik und Medizin. Beispielhaft werden drei Erfolgsmodelle dargestellt: Medizinische Bildgebung, mathematische Modellierung und Biosignalverarbeitung im Bereich der Dynamik des Herzens sowie mathematische Modellierung und Simulation in der Krebstherapie Hyperthermie und der Mund-Kiefer-Gesichts-Chirurgie. In allen Fällen existiert ein Gleichklang der Interessen von Medizin und Mathematik: Beide Disziplinen wollen die Resultate schnell und zuverlässig. Für die Klinik heißt das, dass notwendige Rechnungen in möglichst kurzer Zeit, und zwar auf dem PC, ablaufen müssen und dass die Resultate so genau und belastbar sein müssen, dass medizinische Entscheidungen darauf aufbauen können. Für die Mathematik folgt daraus, dass höchste Anforderungen an die Effizienz der verwendeten Algorithmen und die darauf aufbauende Software in Numerik und Visualisierung zu stellen sind. Jedes Kapitel endet mit einer Darstellung der Perspektive des jeweiligen Gebietes. Abschließend werden mögliche Handlungsoptionen für Politik und Wirtschaft diskutiert.
    Schlagwort(e): ddc:000
    Sprache: Deutsch
    Materialart: reportzib , doc-type:preprint
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  • 6
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    Constraint Integer Programming: Techniques and Applications (2008)
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    Publikationsdatum: 2022-03-14
    Beschreibung: 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 for solving satisfiability problems. SCIP is available in source code and free for noncommercial use. We demonstrate the usefulness of CIP on three 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 demonstrate how to use CIP techniques to compute the number of optimal solutions of integer programs. Third, we employ the CIP framework to solve chip design verification problems, which involve some highly nonlinear 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 nonlinear constraints by employing constraint programming techniques.
    Schlagwort(e): ddc:000
    Sprache: Englisch
    Materialart: reportzib , doc-type:preprint
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  • 7
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    Weiterentwicklung und Ausbau des Internet-Informationsdienstes "Math&Industry" (2008)
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    Publikationsdatum: 2022-04-11
    Beschreibung: Mit dem Informationsdienst Math&Industry soll ein Prototyp eines dezentralen Informationssystems für Förderprogramme und Forschungsprojekte geschaffen werden, das sich auf andere Programme (bezüglich angewandter Mathematik, aber auch darüber hinaus) übertragen lässt. Das betrifft sowohl die Konzeption (Strukturierung der Informationen) als auch die Werkzeuge, die anderen BMBF-Förderprogrammen zur Verfügung gestellt werden können. Damit sollen diese in die Lage versetzt werden, die in Math&Industry entwickelten Konzepte und Werkzeuge an ihre spezifischen Bedürfnisse anzupassen.
    Schlagwort(e): ddc:000
    Sprache: Deutsch
    Materialart: reportzib , doc-type:preprint
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  • 8
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    Models for Railway Track Allocation (2007)
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    Publikationsdatum: 2020-08-05
    Beschreibung: This article is about the optimal track allocation problem (OPTRA) to find, in a given railway network, a conflict free set of train routes of maximum value. We study two types of integer programming formulations: a standard formulation that models block conflicts in terms of packing constraints, and a new extended formulation that is based on additional configuration' variables. We show that the packing constraints in the standard formulation stem from an interval graph, and that they can be separated in polynomial time. It follows that the LP relaxation of a strong version of this model, including all clique inequalities from block conflicts, can be solved in polynomial time. We prove that the extended formulation produces the same LP bound, and that it can also be computed with this model in polynomial time. Albeit the two formulations are in this sense equivalent, the extended formulation has advantages from a computational point of view, because it features a constant number of rows and is therefore amenable to standard column generation techniques. Results of an empirical model comparison on mesoscopic data for the Hannover-Fulda-Kassel region of the German long distance railway network are reported.
    Schlagwort(e): ddc:000
    Sprache: Englisch
    Materialart: reportzib , doc-type:preprint
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  • 9
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    Barrier Methods for Optimal Control Problems with State Constraints (2007)
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    Publikationsdatum: 2016-06-09
    Beschreibung: We study barrier methods for state constrained optimal control problems with PDEs. In the focus of our analysis is the path of minimizers of the barrier subproblems with the aim to provide a solid theoretical basis for function space oriented path-following algorithms. We establish results on existence, continuity and convergence of this path. Moreover, we consider the structure of barrier subdifferentials, which play the role of dual variables.
    Schlagwort(e): ddc:000
    Sprache: Englisch
    Materialart: reportzib , doc-type:preprint
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  • 10
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    Conformation-based transition state theory (2007)
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    Publikationsdatum: 2016-06-09
    Beschreibung: For the treatment of equilibrated molecular systems in a heat bath we propose a transition state theory that is based on conformation dynamics. In general, a set-based discretization of a Markov operator ${\cal P}^\tau$ does not preserve the Markov property. In this article, we propose a discretization method which is based on a Galerkin approach. This discretization method preserves the Markov property of the operator and can be interpreted as a decomposition of the state space into (fuzzy) sets. The conformation-based transition state theory presented here can be seen as a first step in conformation dynamics towards the computation of essential dynamical properties of molecular systems without time-consuming molecular dynamics simulations.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 11
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    P2P Routing of Range Queries in Skewed Multidimensional Data Sets (2007)
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    Publikationsdatum: 2021-01-22
    Beschreibung: We present a middleware to store multidimensional data sets on Internet-scale distributed systems and to efficiently perform range queries on them. Our structured overlay network \emph{SONAR (Structured Overlay Network with Arbitrary Range queries)} puts keys which are adjacent in the key space on logically adjacent nodes in the overlay and is thereby able to process multidimensional range queries with a single logarithmic data lookup and local forwarding. The specified ranges may have arbitrary shapes like rectangles, circles, spheres or polygons. Empirical results demonstrate the routing performance of SONAR on several data sets, ranging from real-world data to artificially constructed worst case distributions. We study the quality of SONAR's routing information which is based on local knowledge only and measure the indegree of the overlay nodes to find potential hot spots in the routing process. We show that SONAR's routing table is self-adjusting, even under extreme situations, keeping always a maximum of $\lceil \log N \rceil$ routing entries.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 12
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    Adaptive Discrete Galerkin Methods Applied to the Chemical Master Equation (2007)
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    Publikationsdatum: 2016-06-09
    Beschreibung: \begin{abstract} In systems biology, the stochastic description of biochemical reaction kinetics is increasingly being employed to model gene regulatory networks and signalling pathways. Mathematically speaking, such models require the numerical solution of the underlying evolution equat ion, also known as the chemical master equation (CME). Up to now, the CME has almost exclusively been treated by Monte-Carlo techniques, the most prominent of which is the simulation algorithm suggest ed by Gillespie in 1976. Since this algorithm requires an update for each single reaction event, realizations can be computationally very costly. As an alternative, we here propose a novel approach, which focuses on the discrete partial differential equation (PDE) structure of the CME and thus allows to adopt ideas from adaptive discrete Galerkin methods (as designed by two of the present authors in 1989), which have proven to be highly efficient in the mathematical modelling of polyreaction kinetics. Among the two different options of discretizing the CME as a discrete PDE, the method of lines approach (first space, then time) and the Rothe method (first time, then space), we select the latter one for clear theoretical and algorithmic reasons. First numeric al experiments at a challenging model problem illustrate the promising features of the proposed method and, at the same time, indicate lines of necessary further research. \end{abstract}
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 13
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    Algorithms to Separate {0,1/2}-Chvatal-Gomory Cuts (2007)
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    Publikationsdatum: 2014-02-26
    Beschreibung: Chvatal-Gomory cuts are among the most well-known classes of cutting planes for general integer linear programs (ILPs). In case the constraint multipliers are either 0 or $\frac{1}{2}$, such cuts are known as $\{0,\frac{1}{2}\}$-cuts. It has been proven by Caprara and Fischetti (1996) that separation of $\{0,\frac{1}{2}\}$-cuts is NP-hard. In this paper, we study ways to separate $\{0,\frac{1}{2}\}$-cuts effectively in practice. We propose a range of preprocessing rules to reduce the size of the separation problem. The core of the preprocessing builds a Gaussian elimination-like procedure. To separate the most violated $\{0,\frac{1}{2}\}$-cut, we formulate the (reduced) problem as integer linear program. Some simple heuristic separation routines complete the algorithmic framework. Computational experiments on benchmark instances show that the combination of preprocessing with exact and/or heuristic separation is a very vital idea to generate strong generic cutting planes for integer linear programs and to reduce the overall computation times of state-of-the-art ILP-solvers.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 14
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    Stability of a Cartesian Grid Projection Method for Zero Froude Number Shallow Water Flows (2007)
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    Publikationsdatum: 2014-02-26
    Beschreibung: In this paper a Godunov-type projection method for computing approximate solutions of the zero Froude number (incompressible) shallow water equations is presented. It is second-order accurate and locally conserves height (mass) and momentum. To enforce the underlying divergence constraint on the velocity field, the predicted numerical fluxes, computed with a standard second order method for hyperbolic conservation laws, are corrected in two steps. First, a MAC-type projection adjusts the advective velocity divergence. In a second projection step, additional momentum flux corrections are computed to obtain new time level cell-centered velocities, which satisfy another discrete version of the divergence constraint. The scheme features an exact and stable second projection. It is obtained by a Petrov-Galerkin finite element ansatz with piecewise bilinear trial functions for the unknown incompressible height and piecewise constant test functions. The stability of the projection is proved using the theory of generalized mixed finite elements, which goes back to Nicola{\"i}des (1982). In order to do so, the validity of three different inf-sup conditions has to be shown. Since the zero Froude number shallow water equations have the same mathematical structure as the incompressible Euler equations of isentropic gas dynamics, the method can be easily transfered to the computation of incompressible variable density flow problems.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 15
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    Jahresbericht 2006 (2007)
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    Publikationsdatum: 2019-10-24
    Schlagwort(e): ddc:000
    Sprache: Deutsch
    Materialart: annualzib , doc-type:report
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  • 16
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    SNDlib 1.0--Survivable Network Design Library (2007)
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    Publikationsdatum: 2020-12-15
    Beschreibung: We provide information on the Survivable Network Design Library (SNDlib), a data library for fixed telecommunication network design that can be accessed at http://sndlib.zib.de. In version 1.0, the library contains data related to 22 networks which, combined with a set of selected planning parameters, leads to 830 network planning problem instances. In this paper, we provide a mathematical model for each planning problem considered in the library and describe the data concepts of the SNDlib. Furthermore, we provide statistical information and details about the origin of the data sets.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 17
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    Solving Railway Track Allocation Problems (2007)
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    Publikationsdatum: 2020-08-05
    Beschreibung: The \emph{optimal track allocation problem} (\textsc{OPTRA}), also known as the train routing problem or the train timetabling problem, is to find, in a given railway network, a conflict-free set of train routes of maximum value. We propose a novel integer programming formulation for this problem that is based on additional configuration' variables. Its LP-relaxation can be solved in polynomial time. These results are the theoretical basis for a column generation algorithm to solve large-scale track allocation problems. Computational results for the Hanover-Kassel-Fulda area of the German long distance railway network involving up to 570 trains are reported.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 18
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    Online Multicommodity Routing with Time Windows (2007)
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    Publikationsdatum: 2020-12-15
    Beschreibung: We consider a multicommodity routing problem, where demands are released \emph{online} and have to be routed in a network during specified time windows. The objective is to minimize a time and load dependent convex cost function of the aggregate arc flow. First, we study the fractional routing variant. We present two online algorithms, called Seq and Seq$^2$. Our first main result states that, for cost functions defined by polynomial price functions with nonnegative coefficients and maximum degree~$d$, the competitive ratio of Seq and Seq$^2$ is at most $(d+1)^{d+1}$, which is tight. We also present lower bounds of $(0.265\,(d+1))^{d+1}$ for any online algorithm. In the case of a network with two nodes and parallel arcs, we prove a lower bound of $(2-\frac{1}{2} \sqrt{3})$ on the competitive ratio for Seq and Seq$^2$, even for affine linear price functions. Furthermore, we study resource augmentation, where the online algorithm has to route less demand than the offline adversary. Second, we consider unsplittable routings. For this setting, we present two online algorithms, called U-Seq and U-Seq$^2$. We prove that for polynomial price functions with nonnegative coefficients and maximum degree~$d$, the competitive ratio of U-Seq and U-Seq$^2$ is bounded by $O{1.77^d\,d^{d+1}}$. We present lower bounds of $(0.5307\,(d+1))^{d+1}$ for any online algorithm and $(d+1)^{d+1}$ for our algorithms. Third, we consider a special case of our framework: online load balancing in the $\ell_p$-norm. For the fractional and unsplittable variant of this problem, we show that our online algorithms are $p$ and $O{p}$ competitive, respectively. Such results where previously known only for scheduling jobs on restricted (un)related parallel machines.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 19
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    Zweieinhalb Jahre Open-Linking im KOBV-Portal: Ein Erfahrungsbericht (2007)
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    Publikationsdatum: 2014-02-26
    Beschreibung: Die Zentrale des Kooperativen Bibliotheksverbunds Berlin-Brandenburg (KOBV) betreibt seit Januar 2004 das KOBV-Portal, in dem u.a. vielfältige Open-Linking-Dienste eingebunden sind. Dieser Beitrag erläutert Open-Linking allgemein und stellt die KOBV spezifischen Dienste im Detail vor. Dabei wird auch die Zugriffsentwicklung auf die KOBV-Open-Linking-Dienste evaluiert. Ein Ergebnis ist, dass signifikante Steigerungen der Nutzung erst dann bewirkt werden, wenn Maßnahmen durchgeführt werden, die erstens die Open-Linking-Dienste stärker ins Bewusstsein der NutzerInnen rücken und zweitens den Weg dorthin im KOBV-Portal verkürzen. Vor allem muss ein schneller Weg zu den Open-Linking-Diensten gewährleistet sein, um die Nutzung deutlich zu steigern. Um zusätzlich den Bekanntheitsgrad der Open-Linking-Dienste bundesweit zu erhöhen, regt die KOBV-Zentrale andere Bibliotheken und Verbünde dazu an, analoge Open-Linking-Dienste einzurichten. Auf diese Weise wird die Handhabung von Open-Linking selbstverständlicher.
    Schlagwort(e): ddc:000
    Sprache: Deutsch
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  • 20
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    Bessel'scher Irrgarten (2007)
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    Publikationsdatum: 2014-02-26
    Beschreibung: Dieser Artikel berichtet über eine erfolgreiche Schüleraktivität, die seit Jahren am Zuse-Institut Berlin (ZIB) bei Besuchen von Schülergruppen erprobt und verfeinert worden ist. Das hier zusammengestellte Material ist gedacht als Basis für eine Unterrichtseinheit in Leistungskursen Mathematik an Gymnasien. Inhaltlich wird von einem zwar für Schüler (wie auch Lehrer) neuen, aber leicht fasslichen Gegenstand ausgegangen: der Drei-Term-Rekursion für Besselfunktionen. Die Struktur wird erklärt und in ein kleines Programm umgesetzt. Dazu teilen sich die Schüler selbstorganisierend in Gruppen ein, die mit unterschiedlichen Taschenrechnern "um die Wette" rechnen. Die Schüler und Schülerinnen erfahren unmittelbar die katastrophale Wirkung von an sich kleinen'' Rundungsfehlern, sie landen -- ebenso wie der Supercomputer des ZIB -- im Bessel'schen Irrgarten''. Die auftretenden Phänomene werden mathematisch elementar erklärt, wobei lediglich auf das Konzept der linearen Unabhängigkeit zurückgegriffen wird. Das dabei gewonnene vertiefte Verständnis fließt ein in die Konstruktion eines klassischen Algorithmus sowie eines wesentlich verbesserten Horner-artigen Algorithmus.
    Schlagwort(e): ddc:000
    Sprache: Deutsch
    Materialart: reportzib , doc-type:preprint
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  • 21
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    On the strength of cut-based inequalities for capacitated network design polyhedra (2007)
    Details
    Publikationsdatum: 2017-08-01
    Beschreibung: In this paper we study capacitated network design problems, differentiating directed, bidirected and undirected link capacity models. We complement existing polyhedral results for the three variants by new classes of facet-defining valid inequalities and unified lifting results. For this, we study the restriction of the problems to a cut of the network. First, we show that facets of the resulting cutset polyhedra translate into facets of the original network design polyhedra if the two subgraphs defined by the network cut are (strongly) connected. Second, we provide an analysis of the facial structure of cutset polyhedra, elaborating the differences caused by the three different types of capacity constraints. We present flow-cutset inequalities for all three models and show under which conditions these are facet-defining. We also state a new class of facets for the bidirected and undirected case and it is shown how to handle multiple capacity modules by Mixed Integer Rounding (MIR).
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 22
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    Competitive Online Multicommodity Routing (2007)
    Details
    Publikationsdatum: 2020-12-15
    Beschreibung: In this paper we study online multicommodity routing problems in networks, in which commodities have to be routed sequentially. The flow of each commodity can be split on several paths. Arcs are equipped with load dependent price functions defining routing costs, which have to be minimized. We discuss a greedy online algorithm that routes each commodity by minimizing a convex cost function that only depends on the demands previously routed. We present a competitive analysis of this algorithm showing that for affine linear price functions this algorithm is 4K2 (1+K)2 -competitive, where K is the number of commodities. For the single-source single-destination 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.
    Schlagwort(e): ddc:000
    Sprache: Englisch
    Materialart: reportzib , doc-type:preprint
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  • 23
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    Exact and Approximate Sparse Solutions of Underdetermined Linear Equations (2007)
    Details
    Publikationsdatum: 2020-12-15
    Beschreibung: In this paper, we empirically investigate the NP-hard problem of finding sparse solutions to linear equation systems, i.e., solutions with as few nonzeros as possible. This problem has received considerable interest in the sparse approximation and signal processing literature, recently. We use a branch-and-cut approach via the maximum feasible subsystem problem to compute optimal solutions for small instances and investigate the uniqueness of the optimal solutions. We furthermore discuss five (modifications of) heuristics for this problem that appear in different parts of the literature. For small instances, the exact optimal solutions allow us to evaluate the quality of the heuristics, while for larger instances we compare their relative performance. One outcome is that the basis pursuit heuristic performs worse, compared to the other methods. Among the best heuristics are a method due to Mangasarian and a bilinear approach.
    Schlagwort(e): ddc:000
    Sprache: Englisch
    Materialart: reportzib , doc-type:preprint
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  • 24
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    Reconciling Theory and Practice: A Revised Pole Equation for W-CDMA Cell Powers (2007)
    Details
    Publikationsdatum: 2014-02-26
    Beschreibung: The performance evaluation of W-CDMA networks is intricate as cells are strongly coupled through interference. Pole equations have been developed as a simple tool to analyze cell capacity. Numerous scientific contributions have been made on their basis. In the established forms, the pole equations rely on strong assumptions such as homogeneous traffic, uniform users, and constant downlink orthogonality factor. These assumptions are not met in realistic scenarios. Hence, the pole equations are typically used during initial network dimensioning only. Actual network (fine-) planning requires a more faithful analysis of each individual cell's capacity. Complex analytical analysis or Monte-Carlo simulations are used for this purposes. In this paper, we generalize the pole equations to include inhomogeneous data. We show how the equations can be parametrized in a cell-specific way provided the transmit powers are known. This allows to carry over prior results to realistic settings. This is illustrated with an example: Based on the pole equation, we investigate the accuracy of average snapshot'' approximations for downlink transmit powers used in state-of-the-art network optimization schemes. We confirm that the analytical insights apply to practice-relevant settings on the basis of results from detailed Monte-Carlo simulation on realistic datasets.
    Schlagwort(e): ddc:000
    Sprache: Englisch
    Materialart: reportzib , doc-type:preprint
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  • 25
    facet.materialart.
    Unbekannt
    Capacitated network design using general flow-cutset inequalities (2007)
    Details
    Publikationsdatum: 2017-08-01
    Beschreibung: This paper deals with directed, bidirected, and undirected capacitated network design problems. Using mixed integer rounding (MIR), we generalize flow-cutset inequalities to these three link types and to an arbitrary modular link capacity structure, and propose a generic separation algorithm. In an extensive computational study on 54 instances from the Survivable Network Design Library (SNDlib), we show that the performance of cplex can significantly be enhanced by this class of cutting planes. The computations reveal the particular importance of the subclass of cutset-inequalities.
    Schlagwort(e): ddc:000
    Sprache: Englisch
    Materialart: reportzib , doc-type:preprint
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  • 26
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    Monte Carlo sampling of Wigner functions and surface hopping quantum dynamics (2007)
    Details
    Publikationsdatum: 2020-02-04
    Beschreibung: Wigner transformation provides a one-to-one correspondence between functions on position space (wave functions) and functions on phase space (Wigner functions). Weighted integrals of Wigner functions yield quadratic quantities of wave functions like position and momentum densities or expectation values. For molecular quantum systems, suitably modified classical transport of Wigner functions provides an asymptotic approximation of the dynamics in the high energy regime. The article addresses the computation of Wigner functions by Monte Carlo quadrature. An ad aption of the Metropolis algorithm for the approximation of signed measures with disconnected support is systematically tested in combination with a surface hopping algorithm for non-adiabatic quantum dynamics. The numerical experiments give expectation values and level populations with an error of two to three percent, which agrees with the theoretically expected accuracy.
    Schlagwort(e): ddc:000
    Sprache: Englisch
    Materialart: reportzib , doc-type:preprint
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  • 27
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    Single-layer Cuts for Multi-layer Network Design Problems (2007)
    Details
    Publikationsdatum: 2020-11-13
    Beschreibung: We study a planning problem arising in SDH/WDM multi-layer telecommunication network design. The goal is to find a minimum cost installation of link and node hardware of both network layers such that traffic demands can be realized via grooming and a survivable routing. We present a mixed-integer programming formulation that takes many practical side constraints into account, including node hardware, several bitrates, and survivability against single physical node or link failures. This model is solved using a branch-and-cut approach with problem-specific preprocessing and cutting planes based on either of the two layers. On several realistic two-layer planning scenarios, we show that these cutting planes are still useful in the multi-layer context, helping to increase the dual bound and to reduce the optimality gaps.
    Schlagwort(e): ddc:000
    Sprache: Englisch
    Materialart: reportzib , doc-type:preprint
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  • 28
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    Combinatorial Online Optimization: Elevators & Yellow Angels (2007)
    Details
    Publikationsdatum: 2020-08-05
    Beschreibung: In \emph{classical optimization} it is assumed that full information about the problem to be solved is given. This, in particular, includes that all data are at hand. The real world may not be so nice'' to optimizers. Some problem constraints may not be known, the data may be corrupted, or some data may not be available at the moments when decisions have to be made. The last issue is the subject of \emph{online optimization} which will be addressed here. We explain some theory that has been developed to cope with such situations and provide examples from practice where unavailable information is not the result of bad data handling but an inevitable phenomenon.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 29
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    Unbekannt
    Volltextserver der Verbünde – Integrierter Zugriff auf lizenzierte Zeitschriftenartikel und freie elektronische Dokumente unter Einsatz von Suchmaschinentechnologie (2007)
    Details
    Publikationsdatum: 2020-12-11
    Beschreibung: Die Intention ist der kooperative Aufbau einer Infrastruktur durch die Bibliotheksverbünde, um den Nutzern Volltext-Angebote dauerhaft und komfortabel zur Verfügung zu stellen: Zeitschriftenartikel und elektronische Dokumente werden mittels Suchmaschinentechnologie indexiert und unter Berücksichtigung von Zugriffsrechten zugänglich gemacht. Realisiert ist dies bereits im KOBV-Volltextserver, der seit Ende 2005 im Routinebetrieb läuft. Vorstellbar ist ein überregionales Netz von Volltextservern der Verbünde, die mittels Suchmaschinentechnologie indiziert und nahtlos in das regionale und lokale Literaturangebot integriert werden. Bei den lizenzierten Materialien sind insbesondere auch die Rechte der Verlage zu wahren und entsprechende Rechtemanagement-Verfahren einzusetzen. Es gilt, transparente Verfahren zu konzipieren und umzusetzen, um für die Verlage die notwendige Vertrauensbasis zu schaffen und gleichzeitig den Einrichtungen ihren berechtigten Zugriff auf die Volltexte zu sichern. Der vorliegende Text ist die schriftliche Fassung eines Vortrages auf dem 3. Leipziger Kongress für Information und Bibliothek "Information und Ethik", der vom 19.-22. März 2007 im Congress Center Leipzig stattfand.
    Schlagwort(e): ddc:000
    Sprache: Deutsch
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  • 30
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    Open Access – Aufbau, Pflege und Betrieb lokaler Publikationsserver in der KOBV-Zentrale (2007)
    Details
    Publikationsdatum: 2020-12-11
    Beschreibung: Zur Unterstützung der Bibliotheken bei ihren Open-Access-Aktivitäten betreibt die KOBV-Zentrale seit Anfang 2005 den Service "Opus- und Archivierungsdienste". Die KOBV-Zentrale agiert als Application Service Provider (ASP) für sämtliche technischen Komponenten des Publikationsprozesses, indem sie die gesamte technische Infrastruktur bereitstellt und betreibt – angefangen bei den lokalen Publikationsservern bis hin zu lokalen Repositories zur Archivierung der elektronischen Dokumente. Der vorliegende Text ist die schriftliche Fassung eines gleichnamigen Vortrages auf der 31. ASpB-Tagung "Kooperation versus Eigenprofil?" der Arbeitsgemeinschaft der Spezialbibliotheken, die vom 25.-28. September 2007 in der Technischen Universität Berlin stattfand.
    Schlagwort(e): ddc:000
    Sprache: Deutsch
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  • 31
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    Transparent boundary conditons for time-dependent problems (2007)
    Details
    Publikationsdatum: 2022-07-07
    Beschreibung: A new approach to derive transparent boundary conditions (TBCs) for wave, Schrödinger, heat and drift-diffusion equations is presented. It relies on the pole condition and distinguishes between physical reasonable and unreasonable solutions by the location of the singularities of the spatial Laplace transform of the exterior solution. To obtain a numerical algorithm, a Möbius transform is applied to map the Laplace transform onto the unit disc. In the transformed coordinate the solution is expanded into a power series. Finally, equations for the coefficients of the power series are derived. These are coupled to the equation in the interior, and yield transparent boundary conditions. Numerical results are presented in the last section, showing that the error introduced by the new approximate TBCs decays exponentially in the number of coefficients.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 32
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    Adaptive Remeshing of Non-Manifold Surfaces (2007)
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    Publikationsdatum: 2022-07-19
    Beschreibung: We present a unified approach for consistent remeshing of arbitrary non-manifold triangle meshes with additional user-defined feature lines, which together form a feature skeleton. Our method is based on local operations only and produces meshes of high regularity and triangle quality while preserving the geometry as well as topology of the feature skeleton and the input mesh.
    Schlagwort(e): ddc:000
    Sprache: Englisch
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  • 33
    Buch
    Buch
    Lighting & Rendering : [3D-Grafiken meisterhaft beleuchten ; realistische Texturen entwickeln] (2007)
    München :Addison-Wesley,
    Details
    Titel: Lighting & Rendering : [3D-Grafiken meisterhaft beleuchten ; realistische Texturen entwickeln]
    Autor: Birn, Jeremy
    Originaltitel: Digital lighting and rendering 〈dt.〉
    Ausgabe: 2., komplett überarb. und erw. Ausg.
    Verlag: München :Addison-Wesley,
    Erscheinungsjahr: 2007
    Seiten: 413 S. : , zahlr. Ill., graph. Darst.
    Serie: DPI
    ISBN: 978-3-8273-2449-8 , 3-8273-2449-1
    Materialart: Buch
    Sprache: Deutsch
    Schlagwort(e): Dreidimensionale Computergraphik ; Realistische Computergraphik ; Dreidimensionale Computergraphik ; Realistische Computergraphik
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  • 34
    Digitale Medien
    Digitale Medien
    Theory of rolling plastics. II. Thermal effectsPublished by permission of the Chief Scientific Officer, Ministry of Supply, England. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 535-539 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: In the rolling of Plastic sheet the viscous work gives rise to heating of the plastic sheet. The maximum temperature reached in the interior of the sheet during shearing is of the interest, both in the theoretical calculation of roll pressure, and from the point of view of possible thermal decomposition effects. A calculation is given for a simple, some-what artificial, model, which leads to an upper value for this maximum temperature if a measurement of the average temperature of the emergent sheet is given. The model taken is that of an infinite sheet, of thickness 2δ, in which heat is continuously liberated at the rate of 4ηφ2 cal. cc. -1 sec. -1, where φ is the relevant value of the rate of compression (assumed constant across the sheet). The curve giving the temperature distribution across the sheet is calculated numerically for two cases; it is relatively flat, as would be expected on physical grounds, since the viscosity, η, decreases as the temperature rises. It is concluded that these thermal effects may be neglected in the calculation of roll pressure in Part 1.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010609
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  • 35
    Digitale Medien
    Digitale Medien
    Symbols for copolymerization (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 581-581 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010612
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  • 36
    Digitale Medien
    Digitale Medien
    Advances in colloid science. Volume II. Scientific progress in the field of rubber and synthetic elastomers. Edited by H. Mark and G. S. Whitby. Interscience, New York, 1946. xl and 433 pp. Author and subject indexes. Price $7.00 (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 582-582 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010613
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  • 37
    Digitale Medien
    Digitale Medien
    Polymerization of olefins and diolefins in suspension and emulsion. Part II (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 549-580 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: This and a previous article (p. 127) review the literature from 1910-1945 on polymerization of olefins and diolefins in suspension and emulsion, and present a number of new measurements not published to date. The subject is considered mainly from the point of view of scientific information on the mechanism of polymerization in aqueous suspensions and emulsions, but brief mention is also made of the more important disclosures in the patent literature. The new data presented in this article refer to (1) initial rates of polymerization of styrene, methyl methacrylate, vinyl acelate and acrylonitrile in aqueous suspensions and in soap emulsions as a function of catalyst concentration, temperature, and soap concentration; (2) influence of water-soluble activators, such as sodium bisulfite; (3) influence of initial size of monomer droplets on initial rates of monomer consumption; (4) study, with the aid of the electron microscope, of size of monomer droplets and polymer particles throughout polymerization; and (5) a few experiments on side reactions in the domain of higher conversions. No attempt is made in this paper to review and appraise the very large number of recent patents (from about 1930 on), which protect special procedures on the use of various promoting, regulating, or modifying ingredients. A complete digest of this practice does not exist at present, but reference may be made to the excellent chapter on emulsion polymerization in the book of Talalay and Magat, to the very valuable compilation of patents by Hoseh, and to the enumeration of a selected number of patents in the book of Scheiber.1
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010611
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  • 38
    Digitale Medien
    Digitale Medien
    A new approach to the theory of rubberlike elasticityCommunication No. 1015 from the Kodak Research Laboratories. Preliminary reports of this work have been presented at the Conference on Rubberlike Elasticity at the Polytechnic Institute of Brooklyn, April 3, 1943, at a meeting of the Society of Rheology in New York City, October 30, 1943, and at the Symposium on the Theory of Long-Range Elasticity at the Cleveland Meeting of the American Chemical Society, April 4, 1944. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 1-13 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Equations are derived for stress-strain curves for a hypothetical model substance containing a large number of like systems, each assumed to be in equilibrium between two states having different arrangements of the atoms. With this model one can study the dependence of the initial elastic modulus, the limiting strain (for infinite stress), and the over-all shape of the stress-strain curve on characteristics of the rearranging systems - their number, the initial energy difference between the two states, the shift of atomic positions, etc. Introduction of an assumed proportionality between the shift per rearrangement and the square of the relative length of the sample (in the direction of the shift) leads to stress-strain curves similar to those determined experimentally for natural rubber and other rubberlike materials.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010101
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  • 39
    Digitale Medien
    Digitale Medien
    Studies on nitrocellulose. Including the construction of an osmotic balance. By Ingvar Jullander. Arkiv kemi mineral. Geol., A21, 1 (1945) (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 146-146 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010208
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  • 40
    Digitale Medien
    Digitale Medien
    American association for the advancement of science - gibson island conferences. Frontiers in chemistry (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 147-147 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010209
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  • 41
    Digitale Medien
    Digitale Medien
    Comparison of ultraviolet absorption and chlorine analysis methods for composition of butadiene-p-chlorostyrene copolymersThis work was carried out under the sponsorship of the Office of Rubber Reserve, Reconstruction Finance Corporation, in connection with the Government Synthetic Rubber Program. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 247-248 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A comparison has been made of the ultraviolet spectrophotometric and chlorine analysis methods for the composition of copolymers of butadiene and p-chlorostyrene. The results of the two methods are in good agreement.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010404
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  • 42
    Digitale Medien
    Digitale Medien
    Use of density-gradient tube in the study of high polymers (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 249-258 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The density-gradient tube is a special glass vessel in which a vertical linear density gradient of almost any desired magnitude can be maintained in a stable condition for prolonged periods by using liquids or solutions of the proper density. This article describes the application of such a device to three typical problems appearing in the field of high polymers: crystallization-rate data, inhomogeneities in composition of copolymers, and rates of polymerization. Possible application to still other problems is indicated.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010405
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  • 43
    Digitale Medien
    Digitale Medien
    Technique of electron-microscope investigation of fiber surfacesPresented in part before the Electron Microscope Society at Princeton University, November 30 and December 1, 1945. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 259-265 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The technique of obtaining polystyrene silica replicas from surfaces and cross sections of fibers is described and electron micrographs obtained from replicas of several fibers are shown.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010406
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  • 44
    Digitale Medien
    Digitale Medien
    Silver dichroism of micellar systems with fibrous structures (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 266-274 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: By embedding submicroscopic silver rodlets in micellar systems with fibrous structures, unexpectedly strongly anisotropic rodlet compounds bodies are formed. The observed dichroism, indigo blue-straw yellow, suggests the possibility that a particular anisotropic modification of silver is being dealt with, instead of cubic silver. On applying Wiener's compound body formulas, it appears, however, that in the short-wave region the observed anisotropic effects (negative rodlet double refraction and dichroism) can be computed from the optical properties of isotropic silver. In the spectral region of the average and long waves, differences are found between the observed anisotropy and the value calculated by means of Wiener's formulas. These differences are, however, not of such a nature that it is necessary to assume an unknown allotropic modification of silver with particular optically anisotropic properties in order to explain them.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010407
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  • 45
    Digitale Medien
    Digitale Medien
    Preparation and properties of rubberlike high polymers. II. Polymerization of mixtures in bulkCommunication No. 54 from the Rubber Foundation. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 353-363 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Mixtures of butadiene and dimethylbutadiene with varying quantities of styrene and acrylonitrile have been copolymerized under various catalytic conditions at 100°C. The formation of cyclic dimers from dienes and vinyl compounds is, in some cases, much more pronounced than the dimerization of the dienes alone. Since the latter is also a kind of Diels-Alder reaction, a series with increasing dienophilic properties can be established from a comparison of the yields of cyclic dimers. From solubility and swelling experiments it is evident that the polymers prepared from butadiene and the vinyl compounds and those from dimethylbutadiene and acrylonitrile are true copolymers. The mechanical properties of the copolymers from butadiene and increasing amounts of a vinyl compound change gradually from those of a rubber to those of the polyvinyl compound. The copolymers from a mixture containing 30% styrene or acrylonitrile are very similar, respectively, to Buna S and Perbunan. Copolymers of the same composition from dimethylbutadiene and acrylonitrile, on the other hand, form a new class of thermoplastics with a much higher temperature of elasticity.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010503
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  • 46
    Digitale Medien
    Digitale Medien
    Preparation and properties of rubberlike high polymers. III. Polymerization of mixtures in emulsionCommunication No. 53 from the Rubber Foundation. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 364-379 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The copolymerization in emulsion of butadiene with varying amounts of styrene and acrylonitrile and of dimethylbutadiene with the latter vinyl compound has been studied on a laboratory scale. An essential difference between polymeric vinyl compounds and polydienes is the olefinic character of the latter, which leads to typical secondary changes in the polymers originally formed during the completion of the reaction. Such changes are of fundamental importance for the ultimate mechanical properties of polymers and copolymers based on dienes. After a brief discussion of the general theoretical line of thought serving as a base for our experiments, the influence of various factors on the rate of polymerization is pointed out and demonstrated by experiments. The changes in the nitrogen content of copolymers from acrylonitrile and the yields as a function of the reaction time have also been studied. From an investigation of some physical properties, such as solubility and swelling, the existence of true copolymers (of unknown irregularity) has been established. Copolymers from dimethylbutadiene and acrylonitrile represent a new class of olefinic thermoplastics resembling gutta-percha. Abbreviations used are BP (benzoyl peroxide) and DAB (diazoaminobenzene).
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010504
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  • 47
    Digitale Medien
    Digitale Medien
    Dependence of the average transversal on the longitudinal dimensions of statistical coils formed by chain molecules (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 380-388 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The transversal dimension of the statistical coil formed by a long-chain molecule in solution or in bulk rubber is independent of the longitudinal dimension, h1, of the coil as long as h1 is small compared with the length of the stretched molecule. On the other hand, the lateral dimension of a coil whose longitudinal vector, h1, is oriented in the direction of stretch undergoes a forced contraction during the deformation of bulk rubber. The forced contraction of the transversal dimension is therefore supplying an extra contribution to the entropy change. Its amount has been estimated in earlier work and it influences the numerical factor occurring in the formula connecting the strain-stretch relation for rubber with the molecular weight of the net fragments.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010505
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  • 48
    Digitale Medien
    Digitale Medien
    Deformation mechanism of cellulose gels. I. Present status of the problemCommunication No. 31 from the Laboratory for Cellulose Research, Utrecht. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 389-392 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A brief outline is given of the present status of research on the problem of the deformation mechanism of cellulose gels. Emphasis is placed on the prevailing idea of a molecular network structure and recognition of the existence of an intimate relationship between the phenomena of deformation and those of swelling. In these respects the problems involved in cellulose research seem to show a marked convergence with those which emerge from recent developments in rubber research. The principle of Kratky's theory of “affined transformation” and the experiments carried out by this author in order to verify his theory are discussed briefly.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010506
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  • 49
    Digitale Medien
    Digitale Medien
    Nature of the carbonyl groups in polyvinyl alcohol (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 419-428 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Measurements of the viscosity of polyvinyl alcohol solutions may be correlated with the chemical nature of the polymer. In particular it is shown that polyvinyl alcohol contains carbonyl groups in the polymer chain, which are to some extent present as ketols. The presence of these keto groups has been demonstrated by a combination of spectrophotometric and chemical techniques. The carbonyl groups appear to be randomly distributed along the polymer chain and also seem to be independent of chain length. The presence of keto groups along the chain allows an explanation for the behavior of aqueous polyvinyl alcohol solutions with acid or alkali.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010509
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  • 50
    Digitale Medien
    Digitale Medien
    Deformation mechanism of cellulose gels. II. Course of crystallite orientation compared to that required by Kratky's theoryCommunication No. 32 from the Laboratory for Cellulose Research, Utrecht. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 393-406 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The paper offers a verification by x-ray experiments of Kratky's theory of affined transformation (affine Raumverzerrung), aiming at an explanation of the mechanism of deformation of swollen cellulose gels upon stretching. Isotropic model filaments of various degrees of swelling were stretched to various extents and x-ray photographs were then taken. Following Kratky, the intensity distribution along the sickles of two paratropic planes of the ribbon-shaped crystallites, the lamellar plane, A0 and the A3 plane (perpendicular to the latter) were measured and the average orientation, expressed in terms of the orientation factor, fx, was calculated. The superposition of the (021) interference on that of the A3 sickle, which had been neglected by Kratky, was accounted for. The experimental results are in conformity with certain characteristic features of the theory; (a) the orientation of the A0 planes advances more rapidly than that of the A3 planes; (b) regardless of the initial degree of swelling of the isotropic filament, the average orientation is actually a univocal function of the elongation, va. On the other hand, the rate of orientation appears to be much greater than that required by theory; the average orientation, expressed in terms of the orientation factor, increases almost twice as rapidly. It is shown, moreover, that, apart from low degrees of orientation, Kratky's theory fails to explain the velocity function of the relative rotation of the crystallites, as derived from the experimental data according to a procedure proposed by Kratky. It is concluded that further work is required to elucidate the mechanism of deformation.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010507
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  • 51
    Digitale Medien
    Digitale Medien
    Determination of polystyrene in GR-S rubberThis investigation was carried out under the sponsorship of the Office of Rubber Reserve, Reconstruction Finance Corporation, in connection with the Government Synthetic Rubber Program. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 429-433 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A convenient procedure for the determination of polystyrene in GR-S is given. The method depends upon degradation of the GR-S by tert-butyl hydroperoxide in the presence of a trace of osmium tetroxide. Polystyrene is not attacked and is separated by precipitation with ethanol.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010510
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  • 52
    Digitale Medien
    Digitale Medien
    Application of the density-gradient tube in fiber research (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 437-439 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010512
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  • 53
    Digitale Medien
    Digitale Medien
    The Baker-Philippoff equation for cellulose acetate solutions (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 434-436 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: By suitable alteration of the exponent the fit of viscosity-concentration data by a Philippoff type equation may be substantially improved. For a series of cellulose acetate solutions the exponent of best fit appears to be related to the physical properties and chemical type of the solvent.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010511
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  • 54
    Digitale Medien
    Digitale Medien
    New method for determination of the activation energy for the gelation of silicic acid solutions (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 441-444 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A new method for the determination of the activation energy for the setting of silicic acid solutions is described. Experimental results point to the conclusion that setting to a gel occurs at a definite stoichiometric point which is independent of temperature.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010601
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  • 55
    Digitale Medien
    Digitale Medien
    Advancing fronts in chemistry. Volume I. High polymers. Edited by Sumner B. Twiss, Department of Chemistry, Wayne University, Detroit, Michigan. Reinhold, New York, 1945. 196 pp. 15 × 23 cm. Price $4.00 (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 440-440 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010513
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  • 56
    Digitale Medien
    Digitale Medien
    Molecular weight averages obtained from sedimentation velocity and diffusion measurementsPresented before a joint meeting of the American Physical Society and the Society of Rheology at Polytechnic Institute of Brooklyn, June, 1945. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 445-454 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: In using the velocity ultracentrifuge in conjunction with free diffusion measurements for the determination of molecular weights of polymolecular systems, it is desirable to know what average molecular weights are obtainable. These average values are not simple moments of the molecular weight frequency curve, but depend on the methods of experimental observation, and on the hydrodynamic character of the molecules in solution. Most often, however, the average molecular weight falls between the number and weight-average values.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010602
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  • 57
    Digitale Medien
    Digitale Medien
    Polymerization of methyl methacrylate in aqueous emulsions (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 466-474 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The kinetics of the polymerization of methyl methacrylate in emulsions has been examined. The initial rate of polymerization is independent of the amount of discontinuous monomer phase present and it is concluded that initiation occurs in the aqueous phase. Monomer is observed to disappear from the discontinuous phase more quickly than it polymerizes, and probably forms a monomer-polymer mixture with the polymer produced. An increase in the subsequent rate of polymerization is attributed to the fact that propagation of the growing polymer chains occurs in this monomer-polymer mixture and this entails a decrease in the velocity of termination due to the high viscosity of such mixtures.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010604
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  • 58
    Digitale Medien
    Digitale Medien
    Dependence of solvation on particle shape (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 475-483 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The relationships which exist between the solvation and shape of colloid particles, as well as between solvation and viscosity, are discussed. From the most important experiments on these subjects the following conclusions may be drawn. Solvation is dependent on the size and shape of the particles and on the chemical relationship of the dispersion medium to the dispersed portion. True or chemical solvation is generally very small and there is no reason to speak of a thick and tightly bound solvent layer. The solvation of compactly formed particles of spherocolloids is greater, the smaller the particles (all other conditions being equal). Solvation is greater, the more loosely the particles are formed (for dispersion mediums having similar chemical properties and for similar dispersed or dissolved substances). Solvation increases when a corpuscular particle is transformed into a rodlike or threadlike particle; the viscosity also increases; if the threads are further broken down into smaller fragments, then the viscosity decreases, but a further increase in the chemical solvationis supposed to occur. The stability of many lyophilic sols, especially the proteins, depends very little on the solvation; it is mainly dependent on the chemical characteristics of the atomic groups which are found on the surfaces of the particles; the least stability is found for surfaces which contain heteropolar groups - that is, surfaces which have the same number of positive and negative ions.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010605
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  • 59
    Digitale Medien
    Digitale Medien
    Polymerization of olefins and diolefins in suspension and emulsion. Part I. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 127-145 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: This and a following article review the literature from 1910-1945 on polymerization of olefins and diolefins in suspension and emulsion, and present a number of new measurements not published to date. The subject is considered mainly from the point of view of scientific information on the mechanism of polymerization in aqueous suspensions and emulsions, but brief mention is also made of the more important disclosures in the patent literature. The new data presented in this article refer to (1) initial rates of polymerization of styrene, methyl methacrylate, vinyl acetate and acrylonitrile in aqueous suspensions and in soap emulsions as a function of catalyst concentration, temperature, and soap concentration; (2) influence of water-soluble activators, such as sodium bisulfite; (3) influence of initial size of monomer droplets on initial rates of monomer consumption; (4) study, with the aid of the electron microscope, of size of monomer droplets and polymer particles throughout polymerization; and (5) a few experiments on side reactions in the domain of higher conversions. No attempt is made in this paper to review and appraise the very large number of recent patents (from about 1930 on), which protect special procedures on the use of various promoting, regulating, or modifying ingredients. A complete digest of this practice does not exist at present, but reference may be made to the excellent chapter on emulsion polymerization in the book of Talalay and Magat (55), to the very valuable compilation of patents by Hosch in “India Rubber World” (27), and to the enumeration of a selected number of patents in the book of Scheiber (50) on pages 210-213.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010207
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  • 60
    Digitale Medien
    Digitale Medien
    Density of cellulose fibers. I. Introduction and experiments on the penetration of liquids into dry celluloseCommunication No. 27 from the Laboratory for Cellulose Research. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 149-155 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: In this paper it is emphasized that density is a typically macroscopic concept which cannot be transferred to small particles or bodies with small pores. This fact has not been duly accounted for in earlier work on the density of cellulose fibers. The usual interpretation of density determinations in various media is criticized and the point of view that cellulose fibers should be considered as porous bodies is dropped. The pore system occurring in native fibers is coarse enough not to interfere with density determinations in indifferent organic liquids.It is shown experimentally that even substances like water and glycerol penetrate very slowly into dry cellulose and that indifferent organic liquids do not penetrate at all. In the experiments with water vapor a new phenomenon, the heterogeneous course of absorption, is observed, giving rise to sharp microscopically visible boundary lines between the wet and the dry portion of the fiber.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010301
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  • 61
    Digitale Medien
    Digitale Medien
    Density of cellulose fibers. II. Density and refractivity of model filamentsCommunication No. 28 from the Laboratory for Cellulose Research. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 156-161 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Accurate determinations of the density and refractive power of various types of model filaments prepared from viscose in the bone-dry state were made. The molecular refraction, according to the formula of Gladstone and Dale, was calculated and shown to correspond within three parts per thousand with the refraction calculated from atomic refractions. It is concluded that the liquid used for the density determinations (mixtures of carbon tetrachloride and nitrobenzene) does not penetrate into the fiber substance. The technique of the experiments is described in detail. The immersion liquids used in the optical measurements were standardized mixtures of butyl stearate and tricresyl phosphate; contamination with moisture during the measurements was definitely excluded.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010302
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  • 62
    Digitale Medien
    Digitale Medien
    Cellulose acetate esters containing amino nitrogen (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 121-126 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Nitrogen was introduced into cellulose acetate by the incorporation of amino acid groups. Some of the mixed esters were soluble in organic solvents. Cast films were examined for dyeing properties with wool-type dyes. Many of the mixed esters containing above 1% nitrogen dyed well with xylene brilliant blue, a typical wool-type dye, Mixed cellulose acetate esters were synthesized containing glycine, dl-α-alanine, β-alanine, and α-isoaminobutyric, d-glutamic, and p-aminobenzoic acids. The amino groups were protected by acetylation prior to use. The N-acetyl amino acids were treated with cellulose diacetate in dioxane solution containing chloroacetic anhydride and magnesium perchlorate as impellor and catalyst, respectively. Cellulose acetate metanilate was prepared by use of the aminosulfo acid chloride. An attempt was made to prepare 6-aminocellulose by the reaction of aqueous ammonia, and also sodamide in liquid ammonia on 6-iodotosylcellulose acetate. Only traces of nitrogen were introduced by this procedure and the recovered products showed signs of extreme degradation.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010206
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  • 63
    Digitale Medien
    Digitale Medien
    Density of cellulose fibers. III. Density and refractivity of natural fibers and rayonCommunication No. 29 from the Laboratory for Cellulose Research. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 162-171 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A micromethod is described for density determinations of artificial cellulose fibers by the floating method, in carbon tetrachloride in a dry and air-free atmosphere, permitting an accuracy of one part per thousand. The density is derived from the temperature at which the samples neither sink nor float. This temperature varies, with the kind of fiber, between 45° and 65°C. Measurements of the refractive power were carried out simultaneously. The refractivity calculated according to Gladstone and Dale yields slightly lower figures than those found for model fibers in the preceding communication (Part II). The average difference amounts to seven parts per thousand and is ascribed to a systematic error in the density determinations, due to a slight absorption of carbon tetrachloride by the fibers at elevated temperatures. This explanation is supported by experiments. The density of native ramie, of contracted and reoriented ramie, and of several series of rayon fibers spun with increasing stretch, is given. The conclusion is reached that the density is a measure of the percentage of crystalline substances in the fiber and it is shown that there is a correlation between density and sorptive capacity toward water vapor. The percentage of crystalline matter is estimated to be 55-60% in native ramie and 20-25% in rayon.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010303
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  • 64
    Digitale Medien
    Digitale Medien
    Submicroscopic structure of cellulose gels (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 172-174 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: In the following paper the crystallization of submicroscopic cellular strands from multimolecular, cellulose films is illustrated by electron micrographs.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010304
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  • 65
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    Digitale Medien
    Spectrophotometric determination of the styrene content of butadiene-styrene copolymers (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 175-182 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The ultraviolet absorption of polystyrene, with maximum absorption at 262 mμ, is due to the presence of phenyl residues in the polymer. The specific extinction coefficient is constant, i.e., independent of the molecular weight of the polymer. This shows that the extinction of the phenyl residues is additive. On the basis of this fact, it is shown that the styrene content of a butadiene-styrene copolymer (such as GR-S rubber) can be determined by ultraviolet spectrophotometry. The relative precision of the determination is about 1%, the probable relative accuracy is about 3%.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010305
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  • 66
    Digitale Medien
    Digitale Medien
    The photochemical decomposition of cellulose acetate-butyrateCommunication No. 1018 from the Kodak Research Laboratories. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 217-224 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The chief result of irradiation of cellulose acetate-butyrate with ultraviolet light is cleavage of the cellulose chains so that the average molecular weight is lowered. The exposed material dissolves more slowly in common solvents than the unexposed. The acyl content and carbon and hydrogen contents are not altered appreciably. The rate of the reaction is independent of the type of common mineral impurities, the concentration of expected decomposition products, such as acetic and butyric acids, and the molecular weight of the cellulose ester. Ultraviolet light is necessary for appreciable reaction. Wave lengths shorter than 3500 Å. are most effective; longer wave lenghts are much less active.
    Zusätzliches Material: 6 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010308
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  • 67
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    Digitale Medien
    Preparation and properties of rubberlike high polymers. I. Polymerization of dienes and vinyl compounds in bulkCommunication No. 53 from the Rubber Foundation. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 200-216 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The polymerization of dienes under the influence of heat, of diazoaminobenzene, and of benzoyl peroxide, has been studied. Diazoaminobenzene probably acts as a slow, but continuous, source of free radicals giving quantitative yields of methyl rubber of good quality from dimethylbutadiene after a few days to a few weeks at 100-125°C. The effect of diazoaminobenzene on butadiene is the same, but the rate of the uncatalyzed dimerization of butadiene at 100°C. is as fast as that of dimethylbutadiene at 150°C. and, therefore, dimerization interferes much more strongly with the polymerization of butadiene. Only 60% of polybutadiene has been obtained. A few experiments with isoprene showed its position between the two other dienes. The effect of benzoyl peroxide on the polymerization of the dienes appeared to be much smaller than was expected from its known catalytic action on the polymerization of vinyl compounds, e.g., styrene, for in this case its activity is about 100-1000 times greater than that of diazoaminobenzene. It is assumed that a larger number of radicals, produced by the fast decomposition of benzoyl peroxide, causes this difference. Diazoaminobenzene has about the same effect on the polymerization of styrene and acrylonitrile as on that of the dienes. The catalytic effect of benzoyl peroxide on the polymerization of the dienes is, on the contrary, 10,000-100,000 times smaller than on that of the vinyl compounds. This difference can be understood by the assumption that the catalyst is quickly used up by oxidizing the dienes and their polymers. While methyl rubber and the polyisoprene resemble raw natural rubber, polybutadiene, prepared under comparable conditions, is hard, swells moderately, and has a tendency to become brittle as a result of oxidation (aging). Abbreviations used are DAB (= diazoaminobenzene) and BP (= benzoyl peroxide).
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010307
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  • 68
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    Digitale Medien
    Statistical behavior of the single chain molecule and its relation to the statistical behavior of assemblies consisting of many chain molecules (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 183-199 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The molecules of high-molecular substances, for instance, those present in rubber, can be treated statistically in two ways. On the one hand, these molecules are such complicated structures that it is possible to attribute a separate entropy and free energy to each giant molecule. On the other hand, solutions of high-molecular substances represent systems in which the single chain molecule is the elementary particle, and to which statistical considerations and concepts such as entropy and free energy can be applied. Depending upon the parameter considered, the same chain molecule must sometimes be treated as a complicated system and at other times as an elementary particle. The problems originating from the simultaneous existence of two stages in the statistical treatment are examined. It is shown that the entropy of an assembly of many chain molecules is not simply equal to the sum of the entropies of the separate chain molecules. This becomes apparent particularly when determining the distribution function with respect to a particular parameter (e.g., distance between the two end points of a molecule) from a statistical consideration of the single molecule on the one hand, and from a consideration of an assembly of identical molecules on the other hand. The relations between entropy and free energy of the individual particle and the a priori probabilities on which the treatment of an assembly is to be based are explained. It is further shown that the same particle can give rise to a macroscopic phenomenon in two ways and to approximately the same extent: first, as a complicated system, and second, as an element in a large assembly of identical particles. This applies in particular to the elastic retractive force and to the strain birefringence in rubber and related substances.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010306
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  • 69
    Digitale Medien
    Digitale Medien
    Determination of catalyst fragments in polymers by absorption in the ultraviolet (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 229-230 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010310
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  • 70
    Digitale Medien
    Digitale Medien
    Polymerization of allyl methacrylate by means of ultraviolet radiation (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 230-231 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010311
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  • 71
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    Digitale Medien
    Sodium-catalyzed copolymerization of 1,3-butadiene and styreneThis investigation was carried out under the sponsorship of the Office of Rubber Reserve, Reconstruction Finance Corporation, in connection with the Government Synthetic Rubber Program. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 275-288 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Butadiene and styrene have been copolymerized by the use of sodium sand as a catalyst. The copolymers containing 75 parts of butadiene and 25 parts of styrene and made at 30° and 50° are soluble in benzene and have intrinsic viscosities ranging from 2.5 to 7.5. The copolymers has a very nearly constant composition throughout the course of the polymerization. The amount of butadiene which has entered the chain by 1,2 addition is greater than in the case of the emulsion copolymer.
    Zusätzliches Material: 14 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010408
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  • 72
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    Digitale Medien
    β-Aminoethoxyl- and β-cyanoethoxylcellulose acetatesHoffman-LaRoche, Inc., Nutley, N. J. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 289-292 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Mixed cellulose acetate-ethers were prepared which contain basic-type nitrogen groups whose films were dyed by xylene brilliant blue. β-Aminoethoxylcellulose acetate was prepared from cellulose diacetate and yarn-type cellulose acetate-propionate using ethyleneimine. β-Cyanoethoxylcellulose acetate was prepared from β-cyanoethoxylcellulose and from cellulose acetate using acrylonitrile with an organic base as catalyst. The solubilities of the mixed ether-esters containing basic type nitrogen groups were less than those of cellulose esters and ethers of comparable degrees of substitution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010409
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  • 73
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    Digitale Medien
    Modern views on the chemistry of vulcanization changes. I. Nature of the reaction between sulfur and olefinsThe work described in this series of papers forms part of a program of fundamental research undertaken by the Board of the British Rubber Producers' Research Association. The experimental details will be published formally at a later date. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 293-304 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Whatever additional factors may be concerned in the production of good vulcanizates from natural rubber by the action of sulfur, there is no doubt that the action of sulfur on olefinic materials in general at the ordinary vulcanization temperature is a chemical one, the primary course of which is determined largely by the constitution of the olefin, and hence may be profitably studied by experimentation with olefins of different unsaturation patterns. Unaccelerated reaction between sulfur and simple monoolefins leads almost exclusively to cross linking of the separate olefin molecules, mostly in pairs, by groups of sulfur atoms. When, however, two or more olefinic units occur in the same molecule, as in the disoprenic hydrocarbons, intramolecular cross linking, i.e., cyclization, at once becomes possible, and the result of sulfur action consists partly in the cross linking of separate molecules as with the monoolefins, but largely in cyclization of the individual olefinic chains, thereby forming sulfur-containing rings. These changes entail a certain loss of unsaturation, from which deductions can be made as to the mechanism of the reaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010410
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  • 74
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    Digitale Medien
    Modern views on the chemistry of vulcanization changes. II. Role of hydrogen sulfideThe work described in this series of papers forms part of a program of fundamental research undertaken by the Board of the British Rubber Producers' Research Association. The experimental details will be published formally at a later date. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 305-311 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Hydrogen sulfide has often been thought to play an important role in the sulfur vulcanization of natural rubber. A study has therefore been made of the reaction of hydrogen sulfide with olefins, including polyisoprenes, with special reference to the capacity of the reagent to react with olefins in the presence of free sulfur. Comparison of the products so obtained with those derived (a) by light-catalyzed reaction of hydrogen sulfide and (b) by reaction of free sulfur with polyisoprenes has greatly assisted the understanding of the course of sulfur reaction in vulcanization processes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010411
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  • 75
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    Digitale Medien
    Elastic properties of textile yarns, represented with the aid of a mechanical model (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 329-339 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A series of experiments on the elastic behavior of various textile materials was carried out. All results are described with the aid of a mechanical model. For this purpose it is necessary to introduce the possibility of a blockade of a part of the model. The elastic properties are characterized by the values of seven independent fundamental constants of the model. The value of one of these constants associated with the blockade can be determined experimentally in a direct way; it is found to be independent of the moisture content. The most important properties of the model correspond with the molecular image of Hermans.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010501
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  • 76
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    Digitale Medien
    Composition of butadiene-styrene copolymers prepared by emulsion polymerizationThis work was carried out on a contract with the Office of Rubber Reserve, Reconstruction Finance Corporation, in connection with the Government Synthetic Rubber Program. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 318-328 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Experimental data are presented on the monomer composition of copolymers of butadiene and styrene prepared by emulsion polymerization at 50°C. The composition of the copolymers is shown to be unaffected by variations in the amount of emulsifier, of mercaptan, and of the nature of the water-soluble polymerization catalyst. The composition of the copolymers formed from a charge containing 25% styrene (by wt.) can be represented accurately over the entire conversion range by the approximate theory according to which each monomer disappears by a first order reaction with the growing chain of the polymer, without taking into account the fact that the end of the growing chain to which the monomer adds may be a radical derived from either of the two monomer molecules. If the ratio of monomers in the charge is varied within wide limits, however, it is found that the simple theory is not adequate and it is necessary to consider that the chain may end with different radicals. The analysis of the experimental data shows that a butadiene molecule adds more rapidly than a styrene molecule to a radical derived either from a butadience or a styrene molecule.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010413
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  • 77
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    Digitale Medien
    Modern views on the chemistry of vulcanization changes. III. Reaction of sulfur with squalene and with rubberThe work described in this series of papers forms part of a program of fundamental research undertaken by the Board of the British Rubber Producers' Research Association. The experimental details will be published formally at a later date. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 312-317 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Squalene containing six isoprene units is more free of end-group effects and less limited in the range of space-distributional contortions of its carbon chain than mono- and diolefins. Hence it is more comparable with rubber than the latter group where matters of chemical reactivity are concerned. Nevertheless, in its reaction with sulfur, squalene pursues a course very similar to that followed by the diisoprene, dihydromyrcene, in that intramolecular sulfide linkages as well as intermolecular polysulfide linkages are formed. Taking into consideration the amount of sulfur which would suffice for the establishment of some given number of the simplest possible intermolecular linkages (i.e., monosulfide linkages), the efficiency of sulfur as a cross-linking reagent during the vulcanization of squalene is seen to be of a rather low order; this condition might be expected to hold for rubber in the absence of auxiliary mechanisms. So far as can be determined by direct experiment the action of sulfur in forming cross links is not essentially different from that encountered with squalene, since there are indications that both intra- and intermolecular sulfide linkages are formed - the latter being of both dialkenyl and dialkyl sulfide type, and, possibly also of alkenyl alkyl type. Under the influence of small amounts of zinc oxide or of various nitrogen-containing organic accelerators, sulfur reacts with the thiol groups of organic mercaptans forming di- and polysulfides, together with hydrogen sulfide. In the presence of rubber the same reaction occurs without actual liberation of hydrogen sulfide and it thus appears that if any thiol groups are formed as intermediates in vulcanization reactions, they will undergo ready conversion into intermolecular di- and polysulfide linkages. This may well represent an important auxiliary mechanism of cross linking.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010412
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  • 78
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    Digitale Medien
    Determination of persulfate in emulsion polymerization laticesThis investigation was carried out under the sponsorship of the Office of Rubber Reserve, Reconstruction Finance Corporation, in connection with the Government Synthetic Rubber Program. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 340-352 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: In the emulsion polymerization of butadiene, styrene, or both, potassium persulfate is often used as the catalyst. A convenient concentration of potassium persulfate in the aqueous layer of the charge is 0.10-0.2%; the method of analysis should therefore be suitable for very small persulfate concentrations. Three methods have been investigated. In the volumetric method the persulfate is allowed to react in an acid medium with an excess of standard ferrous iron, the excess being back-titrated after a given period of time with standard ceric cerium solution. The recommended procedure was found accurate and precise within 0.5%, even at such small concentrations as 5 mg. of potassium persulfate per 100 ml. When latex is analyzed by this method, the polymer is first removed by coagulation with sulfuric acid and the persulfate determined in the filtrate. In order to obtain reliable results the reaction between the persulfate and ferrous iron in the filtrate must be carried out in the absence of oxygen, although this is not necessary in solutions of pure persulfate. The interference by oxygen is attributed to substances of peroxidic character in the fatty acid soaps used as emulsifiers in the emulsion polymerization. The colorimetric method (“Becco” method) is based upon the oxidation of the leuco base of commercial wool green BSMA to a green dye by the persulfate and (colorimetric) measurement of the dye formed. The various factors affecting the accuracy and precision of this method have been investigated and a procedure is given for the analysis of latex. For several reasons, the volumetric and polarographic methods are superior to the colorimetric method. Persulfate in a latex can be determined accurately by polarographic analysis of the latex filtrate after removal of the polymer with sulfuric acid. The polarographic determination can be carried out, in the presence of oxygen, with simple equipment. The method is rapid and precise.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010502
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  • 79
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    Digitale Medien
    Theory of rolling plastics. I. Calculation of roll pressurePublished by permission of the Chief Scientific Officer, Ministry of Supply, England. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 529-534 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: An elementary theory is given for the rolling of polymeric materials, for the case in which the deformation is largely an irreversible flow of the viscous type. The theory treats the rolling process as the homogeneous deformation of volume elements over the arc of contact and neglects frictional forces that may exist at the roll surface. A numerical example is given of the calculation of roll pressure, which agrees with available data to a factor of two or better. A more complete test will require parallel measurements of viscosity and roll pressure on the same material.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010608
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  • 80
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    Digitale Medien
    Investigation of potato proteins (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 484-494 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: By treating potato juice with acid it was found that potato globulin is converted to albumin and an insoluble casein-like protein. Potato albumin, salted out with ammonium sulfate and purified by dialysis, is very similar to ovalbumin; it is reconverted into a globulin-like protein by alkali. Solutions of potato albumin in water, as well as in acids and alkali, have a very low viscosity. Alkaline solutions of globulin have a greater viscosity than those of albumin; the viscosity numbers of the difficulty soluble protein are even greater. On the basis of the viscosity data, it was concluded that the albumin particles are corpuscular, the globulin molecules are longitudinal, and that the dissymetry is greatest for the difficulty soluble protein particles. On the basis of the different solubilities of all three proteins (which apparently have approximately the same chemical composition), it was concluded that the albumin molecule was the smallest and the difficulty soluble protein molecule the largest. An aqueous solution of potato albumin is denatured when heated to 50-60°, the viscosity thereby increasing more than 100-fold. The solutions become only slightly turbid, but do not flocculate. This unusual viscosity rise can be explained by the transformation of globular albumin molecules into fibrous, elongated particles. Only a slight viscosity increase is observed when alkaline solutions of albumin are heated. Albumin, in the presence of small amounts of salt, is precipitated at 50-60°; the salts also lower the turbidity point. However, very small concentrations of calcium chloride have a stabilizing effect. Albumin is not coagulated at room temperature by 1-2 N salt solutions. The experiments on the effect of cold on potato albumin showed that albumin, after congealing and thawing out, was more easily precipitated than the control solution. The viscosity of the cold-damaged albumin was somewhat less than that of the control solution. It was ascertained that the deaminated product of potato albumin was very similar to deaminated ovalbumin (solutions of high viscosity; linear colloid).
    Zusätzliches Material: 10 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010606
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  • 81
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    Digitale Medien
    Water-soluble alkoxyacetals of polyvinyl alcoholContribution from the Research Laboratories. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 540-548 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Polyvinyl alcohol may be reacted with methoxyacetaldehyde, 2-methoxyethoxyacetaldehyde, 2-methoxyethoxyacetaldehyde, 2-n-propoxyethoxyacetaldehyde, tetrahydrofurfuryloxyacetaldehyde, or 3-methoxypropionaldehyde, or with mixtures of these aldehydes, to yield thermoplastic resins which are soluble in cold water below specific temperatures peculiar to each resin, and which are soluble in most organic solvents except aliphatic hydrocarbons.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010610
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  • 82
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    Digitale Medien
    Reactivity of monomers in copolymerization (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 455-465 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: An investigation of the copolymerization of many monomer pairs induced by benzoyl peroxide has shown that an order of monomer reactivity with radicals exists. By utilizing the data available, it was possible to make a semiquantitative arrangement of many monomers according to their relative rates of reaction with radicals. A symmetrical selectivity factor is assumed to account for deviations from the order in copolymerization reactions. This selectivity may be attributed to (1) complex formation between monomers or to (2) dipole, steric, or other factors which are independent of concentration. Copolymerization equations have been derived for each case and application of them to styrene-methyl methacrylate mixtures has indicated that selectivity due to (2) is most important in this system. The equation for case (2) has been applied to other copolymer systems.
    Zusätzliches Material: 11 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010603
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  • 83
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    Heat polymerization of nonconjugated vegetable oilsPresented in part before the Division of Paint, Varnish, and Plastics Chemistry at the 108th Meeting of the American Chemical Society, New York, N. Y., September, 1944. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 495-528 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A general theory is proposed to account quantitatively for the heat polymerization and gelation of the nonconjugated vegetable oils. This is based on a direct approach to polyfunctionality as developed from quantitative considerations of partial random distribution of the fatty acid components in the triglyceride molecules. The differing polymerization rates of linseed and soybean oils are accounted for on the basis of the assumed influence of certain cis-trans geometric isomers. The theory accounts for the anomalous extensive linear polymerization and nongelation of olive oil. Calculations from the theory agree substantially with experimental results on average molecular weight, iodine value, and the percentage of insoluble, infusible cross-linked polymers.
    Zusätzliches Material: 24 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010607
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  • 84
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    Digitale Medien
    Mechanism of vinyl polymerizations. VIII.1 Introduction of foreign end groups (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 44-48 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Results are reported of experiments designed to delineate more clearly the action of retarders and chain transfer agents and to place different labeled end groups at either end of polystyrene molecules.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010105
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  • 85
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    Digitale Medien
    Physicochemical characterization of dispersed chicken feather keratin (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 22-36 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Reduced chicken feather keratin forms a soluble complex in neutral aqueous sodium alkylbenzenesulfonate (average: dodecylbenzenesulfonate). The chemical composition, specific refractive increment, partial specific volume, electrophoretic mobility, osmotic pressure, diffusion constants, and ultracentrifugal sedimentation of the complex have been studied. The complex is heterogeneous but similar to egg albumin-sodium alkylbenzenesulfonate mixtures previously studied in general properties, including fiber-forming properties, the average molecular weight of the dispersed protein units, and the relative symmetry of the dispersed units in dilute solution.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010103
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  • 86
    Digitale Medien
    Digitale Medien
    Molecular processes during deformation of rubberlike elastic bodies (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 49-57 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010106
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  • 87
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    Digitale Medien
    The mechanism of reinforcement. II (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 58-62 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Further experimental evidence is given which indicates that, when a dilute solution of GR-S is mixed with carbon black, certain fractions of the rubber are preferentially adsorbed by the black. After removal of the carbon black and the adsorbed fractions by centrifuging, the “treated” GR-S is obtained by precipitation from the solution. Samples compounded as GR-S gum stock show increasing modulus with increasing amounts of carbon black used for adsorption treatment. However, when the GR-S thus treated is compounded with carbon black, then the effect is reversed. The more black used in the treatment and the higher the modulus of the gum stock, the lower the modulus of loaded stock.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010107
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  • 88
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    Digitale Medien
    Characterization of cellulose derivatives by solution properties: Plasticizers as solventsPresented before the “Symposium on Cellulose and Cellulose Plastics” held under the joint auspices of the Division of Cellulose Chemistry and the Division of Paint, Varnish, and Plastics Chemistry at the fall meeting of the American Chemical Society in New York, N. Y., 1944. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 63-74 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The dimensional stability of molded thermoplastic articles is a function of the extent to which stresses are frozen into them on molding. The kind and amount of plasticizer included in the material to be molded may be varied to minimize the amount of these stresses. Methods of obtaining fundamental information about polymer-plasticizer systems from simple measurements of viscosity and osmotic pressure are suggested in this paper, and some results for cellulose derivatives are given.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010201
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  • 89
    Digitale Medien
    Digitale Medien
    Intramolecular reactions in vinyl polymers as a means of investigation of the propagation step (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 75-82 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The Flory-Wall expressions for the fraction of substituents remaining on a vinyl copolymer, when substituents are removed at random from adjacent 1,3 positions, are extended to the case of nonrandom copolymerization. A copolymer composition equation is derived for the case in which the type of monomer preceding the active freeradical chain end affects the propagation reaction. The distribution of lengths of sequences in copolymers is discussed.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010202
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  • 90
    Digitale Medien
    Digitale Medien
    Mechanism of vinyl polymerizations. IX.For the preceding paper, see C. C. Price and D. H. Read, J. Polymer Science, 1, 44 (1946). Some factors affecting copolymerization (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 83-89 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The influence on polymerization and copolymerization of various structural factors, especially polarity at the double bond of the monomer, is discussed. The effect of substituents in donating or withdrawing electrons appears to be an important regulating factor in copolymerization.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010203
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  • 91
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    Digitale Medien
    Preparation, purification, and polymerization of diethyl silicon dichloridePortion of thesis by Francis J. Honn for the degree of Master of Science, Polytechnic Institute of Brooklyn, 1946. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 102-120 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Diethyl silicon dichloride was prepared by a Grignard synthesis and purified highly. The material in various stages of purification was hydrolyzed and then polymerized. The properties of the hydrolyzate and of the final polymer depended markedly upon the degree of purification of the dichloride. The reaction of diethylsilicanediol with phosphorous pentoxide was also studied; the predominating reaction appears to involve entrance of the pentoxide into the polymeric structure, rather than a simple acceleration of the polycondensation reaction by the removal of water.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010205
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  • 92
    Digitale Medien
    Digitale Medien
    Determination of polymer-liquid interaction by swelling measurementsPresented before the High Polymer Division of the American Physical Society, New York, N. Y., January 25, 1946. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 90-101 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The interaction of polymers and liquids can be fairly well characterized by the value of the quantity μ, commonly used in thermodynamics of polymer solutions and usually evaluated from osmotic pressure measurements. The Flory-Rehner theory of swelling relates the amount of swelling of a slightly cross-linked polymer in a liquid to μ and a parameter Mc, the average molecular weight between cross links. Mc, may be determined for a cross-linked polymer from its swelling volume in a solvent in which osmotic pressure measurements with the noncross-linked polymer have given the value of μ. The cross-linked polymer, thus calibrated, can be used to obtain the μ value for other liquids by measuring its swelling volume in them. This procedure has been carried out on polyvinyl chloride which can be cross linked by heating. Calibration in three different liquids gave comparable values of Mc, thus checking the Flory-Rehner theory. The quantity μ was determined at two different temperatures for fifty liquids. The value of μ and its temperature dependence correlate well with the observed properties of the binary systems. Variation of μ with molecular weight in an homologous series is demonstrated.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010204
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  • 93
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    Digitale Medien
    The reaction of benzoyl peroxide with cyclohexane and cyclohexene. Contribution to the mechanism of the catalyzing action of peroxides in the polymerization of vinyl derivatives (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 407-418 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The course of the reactions of benzoyl peroxide with cyclohexane and cyclohexene may be accounted for by a mechanism involving free radicals and radical chain reactions. With cyclohexane, the average length of the chain hardly exceeds one step and one mole of hydrocarbon reacts with one mole of peroxide. With cyclohexene, chains of two and three steps also occur and about two and one-half moles of hydrocarbon per mole of peroxide take part in the reaction. It is shown that this is due to the one-sided addition of the primary radicals (originating from the peroxide) to the double bond, yielding a new radical without a double bond which can in turn react in the same way with another unsaturated molecule, thus giving rise to polycyclic compounds (chain formation). This polymerization reaction is, however, soon halted by a competitive side reaction involving substitution of the α- (or β)-methylene group, which leaves the double bond intact. In polymerizable vinyl derivatives in which no reactive α-methylene group is present, the competitive reaction cannot occur and the radical chain reaction continues to form a growing chain of interlinked monomeric molecules with annihilation of the double bonds. The two terminal groups of the macromolecules of the final polymerizate are radicals originating from the peroxide used as a catalyst. If a solvent is used, radicals of the latter may also appear occasionally as terminal groups of the polymer. The mechanism of the catalytic action of diacyl peroxides in the polymerization of vinyl derivatives is thus clarified. The molecule linking reaction induced by free radicals in unsaturated compounds also provides an explanation of the action of benzoyl peroxide as a rubber vulcanizer; the peroxide radicals are found as substituents in the rubber molecule.
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010508
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  • 94
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    Digitale Medien
    Mechanism of peroxide-initiated styrene polymerization. Infrared absorption of some polymer samplesTaken in part from a thesis submitted by Harry F. Pfann in partial fulfillment of the requirements for the degree of Master of Science in Chemistry, Polytechnic Institute of Brooklyn, June, 1942. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 14-21 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Previous observations make it probable that one or both ends of a longchain molecule produced by catalyzed vinyl polymerization contain fragments of the initiator. If one uses acid peroxides as initiators, these fragments can contain a carbonyl group. It is the purpose of this paper to investigate whether these carbonyl groups which are present only in a very small amount can be detected by infrared absorption. It seems that in the case of polystyrene initiated with benzoyl peroxide, infrared absorption spectra reveal the presence of a small amount of some carbonyl groups in the polymer. Their amount appears to be in agreement with chemical measurements and with the molecular weight of the material.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010102
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  • 95
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    Digitale Medien
    Experimental study of copolymerizationPortion of thesis by E. Merz for the degree of Master of Science, Polytechnic Institute of Brooklyn, June, 1945. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 37-43 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Using the copolymer composition equation, the critical constants α and β are determined for the systems styrene-2,5-dichlorostyrene, styrene-methyl acrylate, styrene-diethyl maleate, and styrene-diethyl chloromaleate.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010104
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  • 96
    Digitale Medien
    Digitale Medien
    Elastic deformation and molecular weight in polyisobutylene (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 225-228 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A rapid procedure is described for estimating the average molecular weights of polyisobutylenes from deformation-rate measurements.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010309
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  • 97
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    Digitale Medien
    On the structure of the protein molecule. A chemical investigation. By N. TROENSEGAARD. Munksgaard, Copenhagen; Oxford University Press, London. 2nd edition, 1944. 126 pp. In English. 14.00 Danish kroner (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 232-232 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010312
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  • 98
    Digitale Medien
    Digitale Medien
    Sedimentation and diffusion of cellulose moleculesCommunication No. 30 from the Institute for Cellulose Research. (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 233-236 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: It is shown that the sedimentation and diffusion constants of cellulose at infinite dilution conform with a formula derived on the assumption of randomly coiled structures. The principle is introduced that the sedimentation velocity of closely packed particles moving through a liquid exerts an influence on their motion, according to known hydrodynamic laws.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010401
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  • 99
    Digitale Medien
    Digitale Medien
    Use of a stopcock device for sampling latex (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 245-246 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A device is described which permits rapid sampling of systems under pressure.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010403
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  • 100
    Digitale Medien
    Digitale Medien
    Relation between molecular weight and intrinsic viscosity for polymethyl methacrylate (1946)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 237-244 
    Details
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The chain lengths of polymethyl methacrylates prepared with ferrous ion-hydrogen peroxide as the initiating system are consistent with the scheme advanced for the mechanism of the polymerization. The relation between intrinsic viscosity in benzene and molecular weight for fractionated polymethyl methacrylate has been determined and leads to the equation: n = 2.81 × 103 [η]C6H61.32. This equation agrees very well with the data of Schulz, provided that the correct method of extrapolating the osmotic pressures to zero concentration is used. Using the relationship between [η]C6H6 and [η]CHCl3 obtained experimentally, the relation between n and [η]CHCl3 (at 20°C.) is: n = 1.81 l3 × 103[η]CHCl31.22.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1946.120010402
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