bluuebunny/crossref_metadata_2025_split huggingface dataset:
Curing of epoxy resins. II. Curing of bisphenol a diglycidyl ether with diamines
Authors: Luňák S. , Dušek K. 
Published: June 2010

AbstractStructural parameters characterizing the course of curing bisphenol A diglycidyl ether with hexamethylenediamine and 4,4′‐diaminodiphenylmethane in the pre‐ and postgelation stages were determined. Conversion at the gel point, concentration of the tertiary amino groups, and number average molecular weights agree fairly well over a broad range of the stoichiometric ratios of functionalities with the values calculated according to the procedure described in Part I (Dušek, llavský, and Luňák, J. Polym. Sci.: Symp. 53, 29 (1975). A satisfactory agreement was also obtained for lightly crosslinked gel prepared with an excess of the amino component. The optimum values for the reactivity (rate constants) ratio of hydrogen on the secondary and primary amino groups are 0.6–0.7 for hexamethylenediamine and 0.35–0.45 for 4,4′‐diaminodiphenylmethane. The agreement between the course of reaction and the assumed model indicates that not far from the gel point, and at a reaction temperature above the glass transition temperature, the diffusion control does not play any major role and a nonhomogeneous course of the curing reactions is not likely. The authors are indebted to M. Mach, and J. Klaban for the mechanical and spectroscopic measurements.
Network characterization of “viton” ahv fluoroelastomer
Authors: Fogiel A. W. 
Published: June 2010

AbstractPolymer‐solvent interaction parameter, elastically effective crosslink density Ce, and crosslinking index γ (the number of crosslinked units per polymer chain) have been determined on several vulcanizates of “Viton” AHV fluoroelastomer by means of swelling equilibrium, swollen compression modulus, and sol‐gel analysis. The parameter decreases strongly with increasing Ce for “Viton” AHV/2‐butanone, which suggests that Ce in three‐dimensional expansion (swelling) may not necessarily be equivalent to Ce calculated from uniaxial compression. The relation between γ and Ce is linear and the intercept at Ce = 0 agrees fairly well with Flory's chain‐end correction. The agreement between the initial molecular weight μMn calculated from the slope of this relation is within 25% of μMn measured before crosslinking. In view of the complex cure system the agreement is adequate to conclude that Ce calculated from the swollen compression modulus represents essentially elastically effective crosslinks of chemical nature. For comparable concentrations of the crosslinking agents used, the highest attainable Ce decreases in the order: bisphenol > hydroquinone > diamine. The bisphenol‐cured system yields Ce values far in excess of the theoretical requirements for bisether crosslinks, which is indicative of a more complex crosslinking chemistry than assumed heretofore. The γ‐Ce relation has been applied successfully to distinguish scission in the crosslinks and in the polymer chain during aging at 250°C.
Presence of dual mechanism in poly(vinyl chloride) dehydrochlorination
Authors: Nolan K. P. , Shapiro J. S. 
Published: June 2010

AbstractThermal dehydrochlorination of poly(vinyl chloride) was demonstrated to be capable of being maximally inhibited by triphenylmethane. Arrhenius parameters observed under conditions of full inhibition are consistent with a unimolecular loss of hydrogen chloride occurring concurrently with a radical‐chain process. At 194°C, the rate of the molecular process is about 30% of the overall reaction, but at higher temperatures it becomes the predominant pathway.
Some unsolved problems concerned with radiation grafting to natural and synthetic polymers
Authors: Stannett V. , Memetea T. 
Published: June 2010

AbstractThe radiation grafting behavior of styrene to cellulose acetate, polyethylene terephthalate, and wool was examined in some detail. A combination of ESR and an analysis of the grafted products was used. Each system exhibited a certain feature which was difficult to explain. The preirradiation grafting of styrene to cellulose acetate gave a bimodal molecular weight distribution of the grafted side chains, the bulk consisting of an extremely narrow distribution high molecular weight polystyrene. Some possible explanations are presented. The yields of grafted side chains in the case of polyethylene terephthalate were considerably greater than the radical yields determined by ESR. Finally in the case of radiation grafting of styrene to wool, numerous low molecular weight branches were obtained. A backbiting type of chain transfer to polymer mechanism was postulated to explain these results and may also be present in the grafting of styrene to polyethylene terephthalate.
Molecular mechanisms in the formation of polydiacetylenes in the solid state
Authors: Lando J. B. , Day D. , Enkelmann V. 
Published: June 2010

AbstractCrystals of poly(5, 7–dodecadiinediol‐1, 12–bisphenylurethane) are monoclinic, P2/1 a. The crystal structure has been determined and refined by full matrix least‐squares analysis of diffractometrically measured intensities. The final R index is 0.081 (719 observed reflections). Intramolecular hydrogen bonding, a strong contribution of electron delocalization in the polymer backbone, and unusual C—C bond lengths in the side chain are observed. Polymerized crystals of o,o′‐bisphenyl glutarate diacetylene crystallize in a C2/c monoclinic space group. The x‐ray refinement reveals a solid solution of the monomer and polymer. It was determined that the only movement that occurs during polymerization is in the diacetylene rod (a rotation of 33°) and in adjacent phenyl groups (a rotation of 19° and a swing of 6°) and all other atomic positions in the side group remain essentially the same. An infrared investigation and the final refined atomic coordinates with their standard deviations indicate the BPG crystal was polymerized to an extent of 35%. The final R index is 0.075 (902 observed reflections). Again a strong contribution of electron delocalization in the polymer backbone is observed.
Biological and biochemical activities of protobiopolymers
Authors: Simionescu C. I. , Dénes F. , Brandsch R. 
Published: June 2010

AbstractThe biological and biochemical activity of protobiopolymers and their macromolecular aggregates (microspheres) synthesized in simulative primeval Earth conditions has been investigated. In vitro and in vivo experiments were carried out on bovine albumine and Tubifex egg cells, respectively. The activity of trypsin encapsulated microspheres was studied also. Intense biological and biochemical activities of the protobiopolymers and the trypsin encapsulated microspheres have been observed. It is noteworthy that the development and the division of the egg cells are influenced dramatically.
Molecular degradation of polymers
Authors: Devries K. L. , Igarashi M. , Chao F. 
Published: June 2010

AbstractAn understanding of the transmittal of force or stress through the molecular (or atomic) network of a body should not only be helpful in predicting the load carrying capability of materials but might also provide information on how structure can be altered to enhance properties. A molecular understanding of mechanical properties is particularly difficult in polymers where such factors as molecular weight, tacticity, crystallinity, presence of networks, orientation, etc., may have an influence. In no class of materials are intricacies of physical structure more important than in polymers. Polymers with very similar chemical structures but differing physical structure can have physical properties differing by orders of magnitude. It would obviously be helpful to have means to probe molecular and atomic events and occur during the loading and destruction of the polymer structure. Instruments that have been used for this purpose include: (1) electron spin resonance (ESR) to monitor free radical production resulting from homolytic chain scission, (2) Fourier transform infrared spectroscopy (FTIR) to measure new end groups resulting from molecular chain rupture, and (3) intrinsic viscosity or gel permeation chromotography (GPC) to detect molecular weight changes (MWC) accompanying molecular degradation. This presentation will discuss and compare research results from these methods. Particular emphasis will be placed on recent studies in which computer modeling has been used to identify ESR spectra and a comparison of the results obtained by ESR, FTIR, and MWC for polystyrene.
Structure in dispersions of polymer particles
Authors: Ottewill R. H. 
Published: June 2010

AbstractIn concentrated polymer latex systems where strong repulsive forces, either electrostatic or steric, exist between the particles ordering of the particles occurs. The structure formed can be examined by small angle neutron scattering and experiments indicate that the arrangement of the particles is liquid‐like. Results are reported for a poly(‐styrene) latex in an aqueous electrolyte solution and for a poly(‐deuteromethyl methacrylate) latex, with the particles stabilised by poly‐12‐hydroxy stearic acid in dodecane.
Latex particle size distributions from steady‐state continuous stirred‐tank reactor systems
Authors: Poehlein Gary W. , Lee H. C. , Stubicar Nada 
Published: June 2010

AbstractThe particle size distribution (PSD) of latex produced in a continuous reactor depends on recipe ingredients and reactor design and operation. Alfrey and co‐workers developed theoretical models to predict PSDs for several cases. This work is briefly reviewed in the present paper, and more recent models are presented. The potential use of PSD data for the quantitative determination of kinetic parameters related to free radical desorption from latex particles is discussed.
The dimeric transmembrane domain of prolyl dipeptidase DPP‐IV contributes to its quaternary structure and enzymatic activities
Authors: Chung Kuei‐Min , Cheng Jai‐Hong , Suen Ching‐Shu , Huang Chih‐Hsiang , Tsai Cheng‐Han , Huang Li‐Hao , Chen Yi‐Rong , Wang Andrew H.‐J. , Jiaang Weir‐Torn , Hwang Ming‐Jing , Chen Xin 
Published: June 2010

AbstractDipeptidyl peptidase IV (DPP‐IV) is a drug target in the treatment of human type II diabetes. It is a type II membrane protein with a single transmembrane domain (TMD) anchoring the extracellular catalytic domain to the membrane. DPP‐IV is active as a dimer, with two dimer interacting surfaces located extracellularly. In this study, we demonstrate that the TM of DPP‐IV promotes DPP‐IV dimerization and rescues monomeric DPP‐IV mutants into partial dimers, which is specific and irreplaceable by TMs of other type II membrane proteins. By bioluminescence resonance energy transfer (BRET) and peptide electrophoresis, we found that the TM domain of DPP‐IV is dimerized in mammalian cells and in vitro. The TM dimer interaction is very stable, based on our results with TM site‐directed mutagenesis. None of the mutations, including the introduction of two prolines, resulted in their complete disruption to monomers. However, these TM proline mutations result in a significant reduction of DPP‐IV enzymatic activity, comparable to what is found with mutations near the active site. A systematic analysis of TM structures deposited in the Protein Data Bank showed that prolines in the TM generally produce much bigger kinking angles than occur in nonproline‐containing TMs. Thus, the proline‐dependent reduction in enzyme activity may result from propagated conformational changes from the TM to the extracellular active site. Our results demonstrate that TM dimerization and conformation contribute significantly to the structure and activity of DPP‐IV. Optimal enzymatic activity of DPP‐IV requires an optimal interaction of all three dimer interfaces, including its TM.
Characterization of conantokinRl‐A: molecular phylogeny as structure/function study
Authors: Gowd Konkallu H. , Watkins Maren , Twede Vernon D. , Bulaj Grzegorz W. , Olivera Baldomero M. 
Published: June 2010

AbstractA multidisciplinary strategy for discovery of newConusvenom peptides combines molecular genetics and phylogenetics with peptide chemistry and neuropharmacology. Here we describe application of this approach to the conantokin family of conopeptides targeting NMDA receptors. A new conantokin fromConus rolani, ConRl‐A, was identified using molecular phylogeny and subsequently synthesized and functionally characterized. ConRl‐A is a 24‐residue peptide containing three γ‐carboxyglutamic acid residues with a number of unique sequence features compared to conantokins previously characterized. The HPLC elution of ConRl‐A suggested that this peptide exists as two distinct, slowly exchanging conformers. ConRl‐A is predominantly helical (estimated helicity of 50%), both in the presence and absence of Ca++. The order of potency for blocking the four NMDA receptor subtypes by ConRl‐A was NR2B > NR2D > NR2A > NR2C. This peptide has a greater discrimination between NR2B and NR2C than any other ligand reported so far. In summary, ConRl‐A is a new member of the conantokin family that expands our understanding of structure/function of this group of peptidic ligands targeted to NMDA receptors. Thus, incorporating phylogeny in the discovery of novel ligands for the given family of ion channels or receptors is an efficient means of exploring the megadiverse group of peptides from the genusConus. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.
Adsorbate‐induced modification of the surface electric field of GaAs (001)‐c(4 × 4) measured via the linear electro‐optic effect
Authors: Bruhn T. , Passmann R. , Fimland B. O. , Kneissl M. , Esser N. , Vogt P. 
Published: June 2010

AbstractWe have investigated the modification of the surface electric field (SEF) of the GaAs (001)‐c(4 × 4) surface during the adsorption of cyclopentene and 1,4‐cyclohexadiene molecules by reflectance anisotropy spectroscopy (RAS) in the spectral range from 1.5 to 5.0 eV. At around 3 eV the RAS line shape originates from the so‐called linear electro‐optic effect (LEO). The amplitude of the LEO oscillation scales linearly with the SEF within the RAS penetration depth and is thus a measure for it. For the separation of the LEO from the RAS spectra several different methods are described in the literature. Here, we present a modified method which allows the LEO separation in particular for interfaces between GaAs and organic molecules. The results obtained this way show a significant increase of the LEO effect upon molecule adsorption indicating a higher SEF. The observed changes of the surface electronic properties are probably related to a modification of surface strain upon molecule adsorption.
Hydrogenated amorphous silicon based surface passivation of c‐Si at high deposition temperature and rate
Authors: Illiberi A. , Creatore M. , Kessels W. M. M. , van de Sanden M. C. M. 
Published: June 2010

AbstractLow substrate temperature during deposition of a‐Si:H is considered a necessary condition to reach excellent surface passivation of c‐Si wafers, such as a hydrogen‐rich and atomically abrupt a‐Si:H/c‐Si interface forms. From a comparison between surface passivation levels achieved by different deposition methods, delivering a broad range of a‐Si:H growth rates, we show that a high a‐Si:H deposition rate (∼3 nm/s) is crucial in achieving an excellent level of surface passivation at high deposition temperatures (>425 °C) compatible with emerging post‐deposition thermal treatments of solar cells. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adaptive discrete neural observer design for nonlinear systems with unknown time‐delay
Authors: Na Jing , Herrmann Guido , Ren Xuemei , Barber Phil 
Published: June 2010

AbstractThis paper focuses on the adaptive observer design for nonlinear discrete‐time MIMO systems with unknown time‐delay and nonlinear dynamics. The delayed states involved in the system are arguments of a nonlinear function and only the estimated delay is utilized. By constructing an appropriate Lyapunov–Krasovskii function, the delay estimation error is considered in the observer parameter design. The proposed method is then extended to the system with a nonlinear output measurement equation and the delayed dynamics. With the help of a high‐order neural network (HONN), the requirement for a precise system model, the linear‐in‐the‐parameters (LIP) assumption of the delayed states, the Lipschitz or norm‐boundedness assumption of unknown nonlinearities are removed. A novel converse Lyapunov technical lemma is also developed and used to prove the uniform ultimate boundedness of the proposed observer. The effectiveness of the proposed results is verified by simulations. Copyright © 2010 John Wiley & Sons, Ltd.
Robust consensus of multiple inertial agents with coupling delays and variable topologies
Authors: Chen Gang , Lewis Frank L. 
Published: June 2010

AbstractIn this paper, we consider the exponential second‐order consensus problem of a network of inertial agents with time‐varying coupling delays and variable balanced topologies. The passive decomposition approach is employed to incorporate the agents' inertial effect into the distributed control design. The sufficient conditions for the exponential second‐order consensus are provided, both when the topology is switched arbitrarily (without dwell time between consecutive switches) and when it is switched with average dwell time. The results present conditions that must be satisfied by the controller design parameters and performance requirements. Furthermore, an approach to the design of consensus protocol is presented, which is robust to the time delays and the dynamically changing interaction topologies. Numerical examples are given to illustrate our theoretical results. Copyright © 2010 John Wiley & Sons, Ltd.
Robust stability of nonlinear time‐delay systems with interval time‐varying delay
Authors: Orihuela L. , Millan P. , Vivas C. , Rubio F. R. 
Published: June 2010

AbstractThis paper deals with the problem of obtaining delay‐dependent stability conditions and L2‐gain analysis for a class of nonlinear time‐delay systems with norm‐bounded and possibly time‐varying uncertainties. No restrictions on the derivative of the time‐varying delay are imposed, though lower and upper bounds of the delay interval are assumed to be known. A Lyapunov–Krasovskii functional approach is proposed to derive novel delay‐dependent stability conditions which are expressed in terms of linear matrix inequalities (LMIs). To reduce conservatism, the work exploits the idea of splitting the delay interval in multiple regions, so that specific conditions can be imposed to a unique functional in the different regions. This improves the computed bounds for certain delay‐dependent integral terms, providing less conservative LMI conditions. Examples are provided to demonstrate the reduced conservatism with respect to the available results in the literature. Copyright © 2010 John Wiley & Sons, Ltd.
ℒ︁2gain analysis of linear systems with a single switching
Authors: Sebe Noboru , Suyama Koichi 
Published: June 2010

AbstractFor analysis and design of fault‐tolerant control systems, it is very important to evaluate the effects of failures, especially the transient responses caused by failures. This paper considers the ℒ︁2gain analysis of linear systems with a single switching, and gives necessary and sufficient conditions for the analysis. Also, the worst disturbance corresponding to the switching ℒ︁2gain is explicitly characterized. Copyright © 2010 John Wiley & Sons, Ltd.
Auswirkungen der Vorspannung auf das Tragverhalten von SL‐Verbindungen
Authors: Lange Jörg , Friede Roland 
Published: June 2010

AbstractDer Tragsicherheitsnachweis für Schrauben mit Zug‐ und Querbelastung erfolgt nach DIN 18800‐1 (810) durch die quadratische Interaktion. Dabei stellt sich die Frage, ob bei reiner Querbeanspruchung eine Vorspannkraft als Zuganteil berücksichtigt werden muss. Um diese Frage zu klären, wurden am Fachgebiet Stahlbau der TU Darmstadt Abscherversuche an Schrauben mit unterschiedlichen Vorspanngraden durchgeführt. In diesem Beitrag werden die Versuche vorgestellt und Empfehlungen zur Behandlung der Vorspannkraft ausgesprochen.Influence of the preload on the resistance of bearing‐type connections. The design resistance of bolts under tension and shear is given in DIN 18800‐1 (810) by a quadratic interaction. The question is, whether the tension due to a preload has to be taken into account. The workgroup steel construction of the Technische Universität Darmstadt, Germany, has run tests to assess the influence of the preload in bearing‐type connections. In this paper the tests are presented and recommendations to take the preload into account are given.
Die Edelstahlrampen im Haus der Musiker der Stiftung Insel Hombroich – Konstruktion und Ausführung
Authors: Kappauf Horst 
Published: June 2010

AbstractDas Haus der Musiker am westlichen Rand der Insel Hombroich bei Neuss wurde von dem New Yorker Architekten Raimund Abraham entworfen. Der Entwurf wurde erstmals 1996 auf der Architektur‐Biennale in Venedig vorgestellt. Nach einem langen Reifungsprozess wurde 2006 mit dem Bau der Studier‐ und Begegnungsstätte für junge Künstler begonnen. 2010 wurden die Rampen, Bühnen und Wendeltreppen, mit denen das Obergeschoss erschlossen wird, fertiggestellt. Mit seinen klaren Formen und seinen klaren Funktionen ist es ist ein typischer Abraham‐Bau.Dieser Aufsatz ist meinem Freund Raimund Abraham gewidmet, einem großen Architekten, der am 4. März 2010 in Los Angeles nach einem Vortrag am Southern California Institut of Architecture bei einem Autounfall um Leben kam und damit die Fertigstellung des Hauses nicht mehr erleben kann. Für den Bauherrn und Kunstsammler Karl‐Heinrich Müller, der 2007 verstorben ist, und auch für den Architekten sowie für den Statiker war es eine große Herausforderung und Ehre Raimund Abrahams Ideen umzusetzen zu dürfen. Raimund Abraham wird auch in diesem Haus weiterleben.The stainless‐steel ramps inside the Haus der Musiker of the Foundation Insel Hombroich – Structure and Execution. The Haus der Musiker (House of Musicians) near Neuss, Germany, has been designed by the New York Architect Raimund Abraham. The design was presented for the first time in 1996 at the architecture‐biennale at Venice. After a longer period of reflection the construction of the building started in 2006, the ramps, the steel platforms and the screw‐stairs – necessary to enter the upper living rooms – were completed in 2010. The house shall be a studying place and a meeting center for young artists.
Arbitrage‐free implementation of implied volatility binomial trees
Authors: Bušić Boris 
Published: June 2010

AbstractWe examine the long‐standing issue of arbitrage violations in implementations of implied volatility binomial trees believed to be the consequence of the inherent limitations imposed by the requirement that such trees be recombining and/or arbitrage violations embedded in the underlying implied volatility function. We disprove the latter on general grounds by demonstrating the possibility of arbitrage violations when implied volatility functions are arbitrage‐free, and the former by formulating an implementation which is arbitrage‐free within the limits imposed by the numerical constraints. Copyright © 2010 Wilmott Magazine Ltd.
Swaptions in Libor Market Model with local volatility
Authors: Henrard Marc 
Published: June 2010

AbstractThe Libor Market Model (LMM) describes the evolution of a yield curve through equations for a discrete set of forward rates. In the original version, the rate dynamic was log‐normal. The rate dynamic has been extended. The main result presented here is a generic approximation that provides an explicit European swaptions price for local volatilities LMM. The approximation is based on an initial freeze approximation very efficient in the Bond Market Model and an original corrector‐type approach. The approximation is strike dependent, allowing a smile calibration. The approximation efficiency is analyzed in details in the displaced diffusion case by comparison to precise Monte Carlo simulations. Copyright © 2010 Wilmott Magazine Ltd.