bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the application of an oxygen probe in chemical kinetics: The influence of the probe response on kinetic measurement
Authors: Connick Robert E. , Zhang Yi‐xue 
Published: January 2005

AbstractMembrance covered oxygen probes are frequently used to monitor the progress of chemical reactions involving dissolved oxygen. For reactions that are comparable in rate to the response of the oxygen probe it is difficult to obtain the correct kinetic constants directly from the probe signal with traditional kinetic data manipulation methods. In this article, we apply the method of impulse response function to describe the probe signal of an oxygen probe for three different types of simple chemical reactions. The impulse response function is obtained experimentally. Using the impulse response function we have obtained the relationships between the probe signal and the kinetic parameters of these reactions. The slow response of the probe has two effects on the kinetic curves of the reaction studied: a time‐lag and distortion of the shape of the kinetic curve throughout the reaction. The latter effect becomes significant when the reaction is fast. Procedures to obtain the correct kinetic information from the oxygen probe signal are described. © 1995 John Wiley & Sons, Inc.
The rate constant for aerial oxidation of NADH by methylene blue
Authors: Ševčík Peter , Dunford Brian 
Published: January 2005

AbstractThe second‐order rate constant for the oxidation of NADH by methylene blue at pH 9.0 and 25°C under aerobic conditions is 4.21 M−1 s−1. © 1995 John Wiley & Sons, Inc.
Rate constants for the gas‐phase reactions of cis‐3‐Hexen‐1‐ol, cis‐3‐Hexenylacetate, trans‐2‐Hexenal, and Linalool with OH and NO3 radicals and O3 at 296 ± 2 K, and OH radical formation yields from the O3 reactions
Authors: Atkinson Roger , Arey Janet , Aschmann Sara M. , Corchnoy Stephanie B. , Shu Yonghui 
Published: January 2005

AbstractRate constants for the gas‐phase reactions of the four oxygenated biogenic organic compounds cis‐3‐hexen‐1‐ol, cis‐3‐hexenylacetate, trans‐2‐hexenal, and linalool with OH radicals, NO3 radicals, and O3 have been determined at 296 ± 2 K and atmospheric pressure of air using relative rate methods. The rate constants obtained were (in cm3 molecule−1 s−1 units): cis‐3‐hexen‐1‐ol: (1.08 ± 0.22) × 10−10 for reaction with the OH radical; (2.72 ± 0.83) × 10−13 for reaction with the NO3 radical; and (6.4 ± 1.7) × 10−17 for reaction with O3; cis‐3‐hexenylacetate: (7.84 ± 1.64) × 10−11 for reaction with the OH radical; (2.46 ± 0.75) × 10−13 for reaction with the NO3 radical; and (5.4 ± 1.4) × 10−17 for reaction with O3; trans‐2‐hexenal: (4.41 ± 0.94) × 10−11 for reaction with the OH radical; (1.21 ± 0.44) × 10−14 for reaction with the NO3 radical; and (2.0 ± 1.0) × 10−18 for reaction with O3; and linalool: (1.59 ± 0.40) × 10−10 for reaction with the OH radical; (1.12 ± 0.40) × 10−11 for reaction with the NO3 radical; and (4.3 ± 1.6) × 10−16 for reaction with O3. Combining these rate constants with estimated ambient tropospheric concentrations of OH radicals, NO3 radicals, and O3 results in calculated tropospheric lifetimes of these oxygenated organic compounds of a few hours. © 1995 John Wiley & Sons, Inc.
Simultaneous laser absorption measurements of CN and OH in a shock tube study of HCN + OH → products
Authors: Wooldridge Steven T. , Hanson Ronald K. , Bowman Craig T. 
Published: January 2005

AbstractSimultaneous, quantitative, narrow‐line laser absorption measurements of CN time‐histories at 388.444 nm and OH time‐histories at 306.687 nm have been made in incident and reflected shock wave experiments using dilute mixtures of nitiric acid (HNO3) and HCN in argon. The thermal decomposition of HNO3 serves as a rapid source of OH upon shock‐heating, and the OH subsequently reacts predominantly with the HCN in the test gas mixture. The rate coefficient for the reaction
equation image
was determined in the temperature range 1120–1960 K via detailed kinetics modeling of the simultaneously acquired CN and OH measurements. These data are in good agreement with lower temperature measurements of the rate of the reverse reaction (−1a) when recent values of the heats of formation of CN and HCN are used. The expression

valid for temperatures 500 to 2000 K, effectively represents the experimental measurements. The estimated uncertainty of the expression for k1a is ±30%, based on the experimental uncertainties of the individual rate coefficient studies. Analysis of the decay region of the experimental OH time‐histories yielded the total rate coefficient k1 (all product channels) for the reaction of HCN with OH for temperatures ranging from 1490 to 1950 K. These measurements are consistent with a previous theoretical analysis of the three primary addition‐isomerization‐dissociation processes for the HCN + OH reaction at combustion temperatures when the contribution to k1 from reaction (1a) is included. © 1995 John Wiley & Sons, Inc.
A kinetic model for pyrolysis of CF2HCl
Authors: Zhang Z. , Pollard R. 
Published: January 2005

AbstractThermal decomposition of CF2HCl has been modeled using 2,269 thermally activated reactions and 63 chemically activated processes. Thermochemical properties for the species involved are calculated using statistical mechanics and group contribution theory, and reaction rate constants are determined using transition state theory. The theoretical predictions, obtained without fitting any parameter values, afree closely with available experimental data. Also, the reactions that control the distribution of reaction products are identified, and this, in turn, permits simplification of the reaction set. Sensitivity studies show that uncertainties in the calculations do not alter the predicted trends in behavior or the main reaction pathways. © 1995 John Wiley & Sons, Inc.
Kinetics and modeling of the H2O2NOx system
Authors: Bromly J. H. , Barnes F. J. , Nelson P. F. , Haynes B. S. 
Published: January 2005

AbstractThe addition of NO (0 to 400ppm) to mixtures of H2 (ca. 1%) and O2 (0.7 to 22%) has been studied over the temperature range 700 to 825 K, in a flow reactor at atmospheric pressure. The overall effect of NO is to promote the oxidation of H2 but high concentrations of O2 actually inhibit the NO‐promoted oxidation of H2.A detailed kinetic mechanism has been constructed and found to describe the experimental observations. The promotion of the oxidation of H2 arises through the catalytic cycle
equation image
The ability of R.34 to reactivate chains normally terminated by the formation of HO2 is a key feature of this system.The predictions are highly sensitive to the rate of the reaction R.5 and the rate constants for this reaction is the only adjustable parameter required in the model. The value of k5,N2 found to describe all the results

has an absolute uncertainty <35%. The uncertainty relative to other important rate constants in the H2O2 system is less than 10%. © 1995 John Wiley & Sons, Inc.
Rod‐Coil Globular Structures – Simple Models for Proteins
Authors: Nowak Christian , Rostiashvili Vakhtang G. , Vilgis Thomas A. 
Published: December 2004

AbstractSummary: In this article, we discuss the phase behavior of rod‐coil copolymers with two main methods. First, a scaling theory on different conformations is presented, which shows how micelles form. The circumstances of their stability is discussed. In the second part, we have formulated the general self‐consistent field theory (SCFT) for the rod(or helix)‐coil multiblock copolymer globule. This model and both approaches provide a simple description of the interplay between the secondary and tertiary structures in a globule α‐helix proteins.Pictorial representation of a used series ratio: each bar, zigzag line and fat dot correspond to $\hat G_{{\rm rod}} ,\;\hat G_{{\rm coil}} ,$ and σ1/2, respectively.magnified imagePictorial representation of a used series ratio: each bar, zigzag line and fat dot correspond to $\hat G_{{\rm rod}} ,\;\hat G_{{\rm coil}} ,$ and σ1/2, respectively.
Clusters of Optimum Size Formed by Hydrophobically Associating Polyelectrolyte in Homogeneous Solutions and in Supernatant Phase in Equilibrium with Macroscopic Physical Gel
Authors: Zaroslov Yuri D. , Fytas Georgios , Pitsikalis Marinos , Hadjichristidis Nikos , Philippova Olga E. , Khokhlov Alexei R. 
Published: December 2004

AbstractSummary: The formation of finite‐sized microgel particles was revealed by photon correlation spectroscopy in aqueous solutions of hydrophobically associative polyelectrolyte polystyrene‐block‐poly(sodium methacrylate)‐block‐polystyrene. Starting from the lowest polymer concentration (1 × 10−6 g · L−1) up to 1 g · L−1 a single relaxation process dominates the spectrum of relaxation times of the polymer solutions. This dominant mode was attributed to the diffusive motion of supramolecular microgel particles with a size of about 100 nm. Above a polyelectrolyte concentration of 1.0 g · L−1, the size of the microgel grows up to ca. 300 nm. At a polymer concentration 20 g · L−1, macroscopic phase separation occurs: the liquid phase of the microgel‐cluster solution coexists with the phase of the macroscopic gel.Schematic representation of the formation of supramolecular structures in aqueous solutions of hydrophobically associative polyelectrolyte.magnified imageSchematic representation of the formation of supramolecular structures in aqueous solutions of hydrophobically associative polyelectrolyte.
Cover Picture: Macromol. Rapid Commun. 24/2004
Authors: Simon Carl G. , Eidelman Naomi , Deng Yan , Washburn Newell R. 
Published: December 2004

Cover: The upper left panel shows a polymer gradient solution being deposited from a syringe onto a glass slide. The colored panel (FTIR microspectroscopy) depicts the composition of the PLLA‐PDLLA composition gradients that were made (blue corresponds to PDDLA‐rich regions, orange to PLLA‐rich regions). The bottom panels are crossed polar images taken in 10 mm intervals across the gradients showing the change in spherulite morphology as the composition changes from PDLLA‐rich (amorphous) to PLLA‐rich (crystalline).Further details can be found in the Communication by C. G. Simon, Jr.,* N. Eidelman, Y. Deng, and N. R. Washburn on page 2003.
Die praxisnahe Ermittlung der Anfälligkeit hochlegierter Stähle für chloridinduzierte Spannungsrißkorrosion Neueste Erkenntnisse über die Aussagefähigkeit verschiedener Prüfverfahren
Authors: Krauß H. , Hirth F. W. , Speckhardt H. 
Published: December 2004

AbstractPrüfverfahren zur Ermittlung der Beständigkeit hochlegierter Cr‐Ni‐Stähle gegen Spannungsrißkorrosion – Vergleich der Aussagefähigkeit verschiedener Methoden – Übertragung auf die Praxis.
Ermittlung des Zeitstandverhaltens einer austenitischen Schweißverbindung
Authors: Kloos K. H. , Granacher J. , Schieblich W. 
Published: December 2004

AbstractDas Zeitstandverhalten einer Schweißverbindung aus dem Stahl X6CrNi1811 wurde an Proben unterschiedlicher Geometrie und Größe untersucht. Unterschiede im Zeitstandverhalten zwischen Schweißverbundproben und Proben aus den einzelnen Gefügezonen werden diskutiert. Das Plastizitäts‐ und Kriechverhalten der einzelnen Gefügezonen wird durch Gleichungen beschrieben.
Ausscheidung von Hollanditwhiskern in Aluminiumtitanatglaskeramiken
Authors: Peters G. , Jansen M. 
Published: December 2004

AbstractDie präparativ‐chemischen Voraussetzungen für eine Verstärkung von Aluminiumtitanatkeramiken durch innere Ausscheidung Whiskerförmiger Fremdphasen werden erarbeitet. Der Schwerpunkt der Untersuchunghen liegt bei dem nichtsilicatischen System Ba‐Al‐Ti‐O. Hierin existiert die Hollanditphase Ba1,23Al2,46Ti5,54O16. Solche Hollanditkristalle stellen potentielle neue keramische whisker zum Zwecke der Verstärkung von Keramiken dar. Im Falle von Tialitkeramiken gelingt die Darstellung dieser Whisker „in situ”︁ auf dem Wege eines glaskeramischen Prozesses, dessen abschließender Schritt in der Kristallisation der Tialitmatrix besteht. Man erhält ein dichtes, whiskerdurchdrungenes Gefüge.
Plastographische Werkstoff‐ und Schadensuntersuchung an Kunstststoffbauteilen
Authors: Schwarz M. , Münster R. 
Published: December 2004

AbstractLicht‐ und rasterelektronenmikroskopische Untersuchungen, energiedispersive Röntgenmikroanalysen an Anschliffen und Dünnschliffen sowie Mikrohärte‐ und DSC‐Messungen ermöglichen die Gefügedarstellung und Werkstoffbeurteilung an Polymerwerkstoffen. Herstellungs‐ und Fertigungsfehler sowie Schädigungen durch Betriebsmedien an Bauteilen aus glasfaserverstärkten Kunststoffen (GFK) und Polypropylen werden dargestellt.
Schwingfestigkeitseigenschaften von Schweißverbindungen hochfester, schweißgeeigneter Baustähle
Authors: Prior F. , Maurer K. L. 
Published: December 2004

AbstractDie hoch‐ und höchstfesten Baustähle sind vor allem im Falle von Schweißverbindungen, unter ungünstigen Randbedingungen, einem normalfesten Baustahl kaum überlegen. Im Rahmen dieser Untersuchungen soll gezeigt werden, ob durch eine Optimeirung der Schweißnahtgeometrie und durch eine nachträgliche mechanische Behandlung durch Strahlen mit Keramikkugeln bzw. mit Stahlsplitt die Schwingfestigkeitseigenschaften von Stumpfstoß‐und Kreuzstoß‐Proben verbessert werden und welche Schwierigkeiten dabei auftreten können. Die praktischen Versuche werden durch theoretische Berechnung mittels FE‐Methode unterstützt und ergänzt. Ein abschließender Vergleich mit den Regelwerken soll die Schwierigkeiten bei der Festlegung von zulässigen Schwingfestigkeitswerten bei solchen Schweißverbindungen verdeutlichen.
Charakterisierung des Ermüdungszustandes in zyklisch beanspruchten Schweißverbindungen durch röntgenographische und mikromagnetische Kenngrößen
Authors: Lachmann C. , Nitschke‐Pagel Th. , Wohlfahrt H. 
Published: December 2004

AbstractDas Ermüdungsverhalten von Schweißnähten wird durch den Werkstoffzustand, die Gefüge‐und Mikrostruktur und Eigenspannungen beeinflußt. Mit Hilfe des mikromagnetischen Meßverfahrens in Verbindung mit röntgenographischen Verfahren wurde das Werkstoffverhalten von zyklisch beanspruchten Schweißnähten des Baustahls S355 mit der Absicht einer Restlebensdauervorhersage untersucht. Die Vorliegenden Ergebnisse bestätigen die Auffassung, daß hierbei Makro‐ und Mikroeigenspannungen, magnetische Kennwerte und Dehnungskennwerte eng miteinander verknüpft sind. Die bei zyklischer Beanspruchung mit hinreichen großen Spannungsamplituden in Naht, WEZ und Grundwerkstoff eintretenden mikostrukturellen Veränderungen kamen einerseits in starken Veränderungen der Makroeigenspannungen zum Ausdruck und in Bereichen stärkerer Plastizierungen auch in Veränderungen der Mikroeigenspannungen, die sich aus der Röntgeninterferenzlinien‐Profilanalyse ergaben. Andererseits waren die Mikrostrukturänderungen schon frühzeitig im Verlauf der zyklischen Beanspruchungen anhand z.T. sehr ausgeprägter Veränderungen der mikromagnetischen Kennwerte nachweisbar. Diese Ergebnisse lassen erwarten, daß sich die mit den mikrostrukturellen Werkstoffveränderungen verknüpfte fortschreitende Schädigung bis zur Entstehung von Makrorissen mit Hilfe des mikromagnetischen Meßverfahrens nachweisen läßt und so Aussagen über den Ermüdungszustand schwingbeanspruchter Bauteile möglich werden.
Thermoplastic aromatic polyimide composites
Authors: Johnson Robert O. , Teutsch Eric O. 
Published: December 2004

AbstractULTEM® polyetherimide resin is characterized by a combination of high performance mechanical, thermal, flammability, and electrical properties. The exceptional mechanical properties are typified by a 15,000 psi tensile strength and 480,000 psi flexural modulus. Because of its amorphous structure and outstanding adhesion to glass, ULTEM® proves to be a very desirable matrix material for glass fiber reinforcement. Addition of fiber glass enhances most mechanical properties and provides a readily processible reinforced thermoplastic.
Macrocomposites made by injection molding
Authors: Hecht James L. 
Published: December 2004

AbstractMacrocomposites can be prepared by injection molding an engineering resin into a mold which contains an insert of a different engineering resin. Using 3/8‐inch beams and 1/4‐inch disks as model systems, we have shown that macrocomposites give parts with combinations of stiffness and toughness far superior than can be made by conventional injection molding of a single material. The key to making macrocomposites with good properties is to have the insert sufficiently hot so that the surface is melted during the second molding step. The toughness of a macrocomposite can be derived not only from proper positioning of a tough material and a stiff material, but also from more effective orientation of glass fibers resulting from the alteration of the mold cavity caused by the insert. Before macrocomposites can be commercialized, significant technical obstacles with respect to both molding equipment and part design procedures must be overcome.
Thermoplastic matrix sheet composites
Authors: Bigg D. M. , Hiscock D. F. , Preston J. R. , Bradbury E. J. 
Published: December 2004

AbstractUntil recently, most high performance composites have been made with low‐viscosity thermosetting polymers. These polymers are ideally suited for producing composites in low production quantities because a wide variety of custom shapes can be manufactured without a high degree of mechanization. As the demand for composites increases, there is a need to develop high‐volume production techniques. Thermoplastic polymer‐based composites are better suited to high‐volume production than thermoset‐based composites because only heat and pressure are needed to form parts; no chemical reaction is required. Thermoplastic matrix composites are not well suited for low‐volume production runs because the need to handle high temperatures and pressures demands equipment that is best utilized for large production runs. In addition to processing advantages, thermoplastic matrix composites exhibit improved impact strength and chemical resistance over most thermoset‐based composites. In the course of this work, composites reinforced with long and continuous glass fibers were produced that had tensile strengths as high as 270 MPa, tensile moduli of 16.2 GPa, and notched Izod impact strengths of 11.1 J/cm.
Thermal expansion of polyurethane reinforced with continuous glass fibers
Authors: Kia Hamid G. 
Published: December 2004

AbstractThis paper is concerned with the study of the thermal expansion properties of polyurethanes which are reinforced with randomly oriented continuous glass fibers. The thermal expansion of reinforced polymers is of prime importance since it has a significiant effect on the overall dimensional stability of molded products. In this work the coefficient of linear thermal expansion (CLTE) is measured for both soft and rigid polyurethane containing various amounts of glass fibers. The experimental results show that: (1) there exists a maximum in the CLTE‐temperature curves, the position of which depends on the type of resin and not on the glass content; (2) over the range of 0 to +70°C for rigid polyurethane, and –30 to +70°C for soft polyurethane, the CLTE decreases with temperature. The existence of a maximum in the above findings is confirmed with computations from a theoretical expression which was modified by the introduction of an efficiency factor. In applying this expression, parameters such as the Poison's ratios, elastic moduli, and the CLTe's of the resins had to be evaluated at various temperatures. Based on these results, the CLTE‐temperature curves were obtained and found to be in agreement with the experimental observations.
Some remarks on acoustic emission measurements and the single‐fiber‐composite test
Authors: Netravali A. N. , Sachse Wolfgang 
Published: December 2004

AbstractWe compare two methods for carrying out single‐fiber‐composite tests in which acoustic emission (AE) data are used to monitor the progression of fiber fracture. The AE measurements include event count or arrival‐time data. While the former is more easily instrumented, the latter provides additional information related to the location of fiber flaws and the progression of the fiber fracture process.
Mechanical properties of nickel‐powder–filled polypropylene composites
Authors: Maiti S. N. , Mahapatro P. K. 
Published: December 2004

AbstractMechanical properties such as tensile and flexural properties as well as impact behavior of nickel‐powder–filled isotactic polypropylene composites were investigated in the composite composition range 0–3.5 volume % Ni. Tensile modulus, strength, and elongation‐at‐break decreased with increase in Ni content, which is attributed to the introduction of discontinuity in the structure. Analysis of tensile strength data indicated the introduction of stress concentration consequent upon addition of Ni into polypropylene. Izod impact strength at first increased up to a critical Ni content beyond which the value decreased inappreciably while flexural modulus and strength increased with filler concentration.
Aging behavior of optically transparent poly (methyl methacrylate) composites
Authors: Lin Hongy , Day Delbert E. , Stoffer James O. 
Published: December 2004

AbstractThe thermal aging between 25 and 115°C of hot pressed glass fiber reinforced poly (methy1 methacrylate)(PMMA) transparent composites was studied as a function of the temperature and time of hot pressing. Thermal aging at near the Tg of the PMMA matrix caused dimensional changes and a reduction in optical transmission and clarity. The reduction in transmission was attributed to gas bubbles that formed in the matrix, which may be due to the evaporation of residual MMA monomer or low Tg (∼ 75°C) polymer in the composites during aging. Thermal cycling between 25 and 100°C by eliminating low Tg of the PMMA matrix establishes the upper temperature limit to which the composite can be exposed without seriously damaging its optical properties.
Consolidation of advanced composites having volatile generation
Authors: Upadhyay Ram K. , Liang Erwin W. 
Published: December 2004

AbstractProcessing polyimide‐based thermosetting matrix composites is complicated because of gaseous volatiles produced during the polymerization and crosslinking reactions. This process involves complex interactions between part geometry, temperature and force cycles, and matrix/fiber properties. A simple model for the consolidation process that treats these composites as a three‐phase system consisting of fiber, resin, and volatile has been developed. This model has been applied to compression molding process for constant thickness laminates and the predictions agree well with experiments. Further extension to handle three‐dimensional parts and the required numerical techniques have also been developed.
Imidazole and chromium acetylacetonate as additives for the cure and fracture toughness of epoxy resins and their composites
Authors: Lin King‐Fu , Wang Wen‐Hsien 
Published: December 2004

AbstractThe effects of additives such as 2‐undecyl‐imidazole (C11Z) and chromium acetylacetonate (Cr(acac)3) were examined on the curing behavior and fracture toughness of tetraglycidyldiaminodiphenyl methane/diaminodiphenyl sulphone (TGDDM/DDS) epoxy resins and their composites. The C11Z additive alone reacted with TGDDM epoxy resins at about 127°C and increased the resin viscosity, resulting in an acceptable resin content for composite processing. Further addition of Cr(acac)3 to TGDDM/DDS/C11Z formulation increased the fracture toughness 5.7 times compared to the typical TGDDM/DDS/BF3MEA epoxy formulation used for the preparation of laminates. The interlaminar fracture toughness of the laminates prepared by TGDDM/DDS/C11Z/Cr(acac)3 formulation was only twice as much as that prepared by typical TGDDM/DDS/BF3MEA. This was due to the fiber bridging contribution to the interlaminar fracture toughness. Based on the experiment, this fiber bridging contribution was only dependent on the fiber content. Thus, the interlaminar fracture toughness is approximated by the sum of the fracture toughness of epoxy matrix and the estimated fiber bridging contribution.