bluuebunny/crossref_metadata_2025 huggingface dataset:
A parallel molecular dynamics strategy
Authors: Nguyen H. L. , Khanmohammadbaigi H. , Clementi E.
Published: December 2004

This article presents a strategy to perform molecular dynamics simulations using parallel processing techniques on a parallel‐distributed loosely coupled system consisting of IBM host computers (4341 and 4381) with attached scientific processors (FPS‐164). This substantially enhances our ability to perform fast and more realistic large scale many‐body trajectory simulations. A powerful extention of the computational range of molecular dynamics the parallel approach offers the opportunity to substantially reduce the simulation time to allow a longer simulation period to study more realistic models and larger systems. It is flexible and uses, for the most part, standard products and straightforward implementation with a broad range of applicability. The implementation of a simulation of water molecules with the inclusion of two‐ and three‐body interactions is discussed. Some considerations in the design and implementation of parallel programs on a loosely coupled system are also presented.
The through‐space transmission of 31P‐31P coupling constants
Authors: Diz A. C. , Contreras R. H. , Natiello M. A. , Gavarini H. O.
Published: December 2004

Inner projections of the polarization propagator (IPPP) are used to study several features of the throughspace transmission of 31P‐31P coupling constants. Cis‐1,2‐diphosphinoethylene is chosen as a model compound. INDO ground state wave functions are used, including two different second‐row parameterizations. Results obtained with a phosphorus spd basis set are also presented. It is found that the overlap of phosphorus lone‐pairs constitute an efficient coupling pathway. Results are discussed in terms of experimental values for similar compounds taken from the literature. Theoretical predictions are in line with experimental trends.
Interaction energy studies of pyrrolopyrimidine nucleoside antibiotics‐toyocamycin
Authors: Sanyal Nitish K. , Ojha Rajendra Prasad , Roychoudhury M.
Published: December 2004

The biological activity of toyocamycin has been examined on the basis of the model developed by Sanyal et al. for the incorporation of nucleoside analogs during transcription. Using the simplified formula of Claverie for intermolecular interactions, computations have been carried out on the pairing energy of toyocamycin base with the complimentary bases as well as on the interaction energy with nucleic acid base pairs. The results are compared with the results of similar computations with nucleic acids. On the basis of the model an attempt has been made to explain the mechanism of the biological action of toyocamycin.
An improved set of mndo parameters for sulfur
Authors: Dewar Michael J. S. , Reynolds Charles H.
Published: December 2004

The MNDO parameters for sulfur have been reoptimized. Calculations for a number of sulfur compounds indicate a very significant improvement. Inclusion of d AOs failed to correct the errors for compounds of sulfur in its higher valence states. Since d AOs are not included, the calculations are still confined to compounds of divalent sulfur.
Spatially constrained minimization of macromolecules
Authors: Bruccoleri Robert E. , Karplus Martin
Published: December 2004

A structural minimization procedure which converges rapidly and restricts the atomic shifts is outlined. It is implemented by adding a harmonic penalty term for the displacements of atomic positions and resetting the reference coordinates with respect to which the constraints are computed during the minimization. The resetting serves to reduce the constraint energy of the minimized structure to negligible levels.
Rates of reaction of allyl radicals: A reassessment
Authors: Throssell J. J.
Published: December 2004

Values of the rate constants for allyl‐radical abstraction from toluene and allyl‐radical recombination have been recalculated in the light of recent data on butene‐1 decomposition. The rate of recombination is in good agreement with that found by Van den Bergh and Callear [13] and the cross‐combination ratio for the allyl + methyl system has a “normal” value of almost 4. It is concluded that allyl radicals behave like alkyl radicals in respect of their rates of reaction with other radicals.
Carbon–nitrogen bond dissociation energy values in C‐nitrosocompounds
Authors: Carmichael P. J. , Gowenlock B. G. , Johnson C. A. F.
Published: December 2004

Measurements of the D(RNO) bond strength in some C‐nitrosocompounds have been made using an electron impact method. The appearance potential of the radical ion (R+) has been determined, the D(RNO) bond energy being obtained from the relation

The values obtained are: D(C6H5NO) = 41 kcal/mole, D(t‐C4H9NO) = 34 kcal/mole, D(t‐C5H11NO) = 36 kcal/mole and D(i‐C3H7NO) = 36.5 kcal/mole. These values are in good agreement with the numerous estimations of Benson and coworkers and confirm that the CN bond strength in C‐nitrosocompounds is very much less than in nitrocompounds or in amines.
Aquation of (N, Ndimethylformamide) pentaamminecobalt (III) perchlorate in aqueous perchlorate media
Authors: Reynolds Warren L. , Knoll Michael A.
Published: December 2004

The first‐order rate constants for aquation of Co(NH3)5(DMF)3+ were determined in aqueous perchlorate media. The rate constants were independent of hydrogen ion concentration and ionic strength, but decreased with increasing perchlorate ion concentration. Proton magnetic resonance studies showed that dimethylformamide was not hydrolyzed to formic acid and dimethylamine in the aquation step. Mass‐spectrometer studies showed that cobalt–oxygen bond breaking occurred in 98 percent, or more, of the aquation acts. Enthalpies and entropies of activation were determined. It was concluded that aquation occurred by an Id mechanism.
Shock tube studies of the N2O/Ar and N2O/H2/Ar systems
Authors: Dean Anthony M.
Published: December 2004

N2O decay has been monitored via infrared emission for a series of mixtures containing N2O/Ar and N2O/H2/Ar. These mixtures were studied behind reflected shock waves in the temperature interval of 1950–3075°K with total concentrations ranging from 1.2 to 2.5 × 1018 molec/cm3. In all cases the N2O decayed exponentially, and a rate constant kobs was obtained. Runs without added H2 could be described by the following Arrhenius parameters: log A = −9.72 ± 0.08 (in units of cm3/molec · sec) and EA = 203.5 ± 3.6 kJ/mole. Addition of 0.01% and 0.1% H2 was observed to increase the decay rate; the largest increase occurred between 2250 and 2500°K with 0.1% H2, where kobs doubled.

Mixtures with no added H2 were analyzed by numerical integration of the following reactions:
equation image

Quantitative agreement between calculations and observations were obtained with both high and low choices for k2 and k3.

The additional reactions
equation image

were included in the analysis of the mixtures containing H2. Here agreement was obtained only when low values were assigned to k2 and k3. The combinations of k1 ← k3 which agreed with all the data were k1 = 3.25 × 10−10 exp (−215 kJ/RT) and k2 = k3 = 1.91 × 10−11 exp (‐105 kJ/RT).
Kinetics and mechanism of the silane decomposition
Authors: Newman C. G. , O'neal H. E. , Ring M. A. , Leska F. , Shipley N.
Published: December 2004

The homogeneous gas‐phase decomposition kinetics of silane has been investigated using the single‐pulse shock tube comparative rate technique (T = 1035–1184˚K, Ptotal ≈︁ 4000 Torr). The initial reaction of the decomposition SiH4 \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm SiH}_{\rm 4} \mathop \to \limits^1 {\rm SiH}_{\rm 2} + {\rm H}_{\rm 2} $\end{document} SiH2 + H2 is a unimolecular process in its pressure fall‐off regime with experimental Arrhenius parameters of logk1 (sec−1) = 13.33 ± 0.28–52,700 ± 1400/2.303RT. The decomposition has also been studied at lower temperatures by conventional methods. The results confirm the total pressure effect, indicate a small but not negligible extent of induced reaction, and show that the decomposition is first order in silane at constant total pressures. RRKM‐pressure fall‐off calculations for four different transition‐state models are reported, and good agreement with all the data is obtained with a model whose high‐pressure parameters are logA1 (sec−1) = 15.5, E1(∞) = 56.9 kcal, and ΔE0±0(1) = 55.9 kcal. The mechanism of the decomposition is discussed, and it is concluded that hydrogen atoms are not involved. It is further suggested that silylene in the pure silane pyrolysis ultimately reacts with itself to give hydrogen: 2SiH2 → (Si2H4)* → (SiH3SiH)* → Si2H2 + H2. The mechanism of H ⟷ D exchange absorbed in the pyrolysis of SiD4‐hydrocarbon systems is also discussed.
The reaction of methoxy radicals with nitric oxide and nitrogen dioxide
Authors: Batt L. , Rattray G. N.
Published: December 2004

By allowing dimethyl peroxide (10−4M) to decompose in the presence of nitric oxide (4.5 × 10−5M), nitrogen dioxide (6.5 × 10−5M) and carbon tetrafluoride (500 Torr), it has been shown that the ratio k2/k2′ = 2.03 ± 0.47: CH3O + NO → CH3ONO (reaction 2) and CH3O + NO2 → CH3ONO2 (reaction 2′). Deviations from this value in this and previous work is ascribed to the pressure dependence of both these reactions and heterogeneity in reaction (2). In contrast no heterogeneous effects were found for reaction (2′) making it an ideal reference reaction for studying other reactions of the methoxy radical. We conclude that the ratio k2/k2′ is independent of temperature and from k1 = 1010.2±0.4M−1 sec−1 we calculate that k2′ = 109.9±0.4M−1 sec−1. Both k2 and k2′ are pressure dependent but have reached their limiting high‐pressure values in the presence of 500 Torr of carbon tetrafluoride. Preliminary results show that k4 = 10.9.0±0.6 10−4.5±1.1/ΘM−1 sec−1 (Θ = 2.303RT kcal mole−1) and by k4 = 108.6±0.6 10−2.4±1.1/ΘM−1 sec−1: CH3O + O2 → CH2O + HO2 (reaction 4) and CH3O + t‐BuH → CH3OH + (t‐Bu) (reaction 4′).
The kinetics of the reactions of C2F5 radicals with Br2 and HBr
Authors: Evans Brian S. , Whittle Eric
Published: December 2004

A mixture of Br2 + HBr + C2F5I was photolyzed in the vapor phase. The reaction

forms C2F5 radicals which are removed by
equation image

equation image
Competitive studies over the range of 74–146°C gave ratios of k10/k9, and these were combined with values obtained previously by different methods at higher temperatures upto 515°C to give

where θ = 2.303RT J/mol. A value is assigned to the activation energy E10, and this, with other data, leads to

at 25°C. This result is in excellent agreement with two previous independent determinations.
Kinetics of electrophilic brominations. Mechanistic significance of the third‐order term
Authors: Fukuzumi S. , Kochi J. K.
Published: December 2004

The rates of electrophilic bromination of various donors follow complex kinetics which include both first‐order and second‐order dependences on bromine, especially in the less polar solvents. The second‐order rate constant ks and the third‐order rate constant kt are evaluated for alkene bromination in carbon tetrachloride, and they are compared to those already listed for the electrophilic brominations of substituted styrenes, arenes, and metal carbonyls in the extant literature. Despite the varying magnitudes of the second– and third‐order rate constants for these diverse donors (and in different solvents), the ratio log(ks/kt) is remarkably invariant. The mechanistic implication of this unique observation is discussed in the context of charge transfer interactions which are common to the activated complexes in the electrophilic brominations of various donors.
Yields of O2(b1Σ) from reactions of HO2
Authors: Keyser L. F. , Choo K. Y. , Leu M. T.
Published: December 2004

A discharge‐flow apparatus with resonance fluorescence and chemiluminescence detection has been used to monitor O2(b 1σ) production from several reactions of the HO2 radical at 300 K and 1‐torr total pressure. O2(b), HO2, and OH were observed when F atoms were added to H2O2 in the gas phase. Signal strengths of O2(b) were proportional to initial concentrations of H2O2 and HO2. These observations were analyzed by using a simple three step mechanism and a more complete computer simulation with 22 reaction steps. The results indicate that the F + HO2 reaction yields O2(b) with an efficiency of (3.6 ± 1.4) × 10−3. By monitoring [O2(b)] and [HO2] upon addition of an excess second reactant to HO2, O2(b) yields from the reactions of HO2 with O, Cl, D, H, and OH were found to be <1 × 10−2, <5 × 10−4, <2 × 10−3, <8 × 10−3, and <1 × 10−3, respectively. Yields of O2(b) from the HO2 ± HO2 reaction were found to be less than 3 × 10−2.
A kinetic study of the chlorination of tertiary alcoholamines in alkaline media
Authors: Antelo J. M. , Arce F. , Armesto J. L. , Garcia‐Verdugo A. , Penedo F. J. , Varela A.
Published: December 2004

The kinetics of the chlorination of various tertiary alcoholamines by hypochlorite have been studied in alkaline media. A reaction mechanism consistent with the experimental results is put forward, and a relationship is established between the rate constants and the polar parameter (Σσ*) of the substituents.
Bond dissociation energies and radical heats of formation in CH3Cl, CH2Cl2, CH3Br, CH2Br2, CH2FCl, and CHFCl2
Authors: Tschuikow‐Roux E. , Paddison S.
Published: December 2004

An analysis of thermochemical and kinetic data on the bromination of the halomethanes CH4–nXn (X = F, Cl, Br; n = 1–3), the two chlorofluoromethanes, CH2FCl and CHFCl2, and CH4, shows that the recently reported heats of formation of the radicals CH2Cl, CHCl2, CHBr2, and CFCl2, and the CH bond dissociation energies in the matching halomethanes are not compatible with the activation energies for the corresponding reverse reactions. From the observed trends in CH4 and the other halomethanes, the following revised ΔH°f,298 (R) values have been derived: ΔH°f(CH2Cl) = 29.1 ± 1.0, ΔH°f(CHCl2) = 23.5 ± 1.2, ΔHf(CH2Br) = 40.4 ± 1.0, ΔH°f(CHBr2) = 45.0 ± 2.2, and ΔH°f(CFCl2) = −21.3 ± 2.4 kcal mol−1. The previously unavailable radical heat of formation, ΔH°f(CHFCl) = −14.5 ± 2.4 kcal mol−1 has also been deduced. These values are used with the heats of formation of the parent compounds from the literature to evaluate CH and CX bond dissociation energies in CH3Cl, CH2Cl2, CH3Br, CH2Br2, CH2FCl, and CHFCl2.
Sensitivity analysis of the two kinetic states of the Belousov‐Zhabotinsky reaction
Authors: Györgyi L. , Deutsch T. , Kőrös E.
Published: December 2004

A recently published kinetic model of the Belousov‐Zhabotinsky reaction was studied by the feature sensitivity analysis of the slow bromide consumption and slow bromide production periods of the relaxing‐type oscillatory system. The computed sensitivities allowed us to reveal the kinetic importance of the 17 individual reactions during the two, “kinetically homogeneous” states of the oscillation. Similarities and differences in the relative kinetic importances of the reaction steps were carefully studied when changing the magnitude of the rate constants (high set and low set). Of the 17 reactions examined, the attack of Ce4+ on malonic acid proved to be an essential step of the mechanism. Using the low set, there emerge more reactions which significantly affect the length of the two kinetic states.
Fortschritte auf dem Gebiete der „Thermit”︁‐Schweißung
Authors: Ahlert Wilhelm
Published: December 2004

Die starke Affinität des Aluminiums zum Sauerstoff ermöglicht es, Schwermetalle, z. B. Eisen, aus ihren Oxyden zu reduzieren. Hieraus entwickelte Hans Goldschmidt die Aluminothermie und das „Thermit”︁‐Verfahren. Die chemischen und thermochemischen Grundlagen des Thermit‐Prozesses werden angegeben. Das auf aluminothermischem Wege aus seinen Oxyden gewonnene Eisen wird in statu nascendi durch Beigabe stahlbildender Zusätze zur Thermit‐Mischung veredelt. Für das „Thermit”︁‐Schweißverfahren ist neben der Ausführungstechnik die Metallurgie des Thermitstahles von größter Bedeutung. Man kann Thermitstähle von verschiedener Art und mit hohen Güteeigenschaften herstellen. Die Verschweißung von Straßenbahnschienen nach dem „thermit”︁‐Verfahren ist in der ganzen Welt üblich. Seit über 25 Jahren schweißen auch Eisenbahnen, allen voran die Deutsche Bundesbahn, ihre Schienen zu größeren Längen und teilweise lückenlos zusammen. Ein weiteres Anwendungsgebiet ist die konstruktive oder instandsetzende Schweißung großer Werkstücke aus gegossenem und geschmiedetem Stahl.
Bemerkungen zu reaktionsfähigen Grundier‐bzw. Rostschutzmitteln
Authors: Scheifele Bernhard F. H.
Published: December 2004

Reaktive Grundiermittel mit Gehalt an Säure reagieren mit dem metall unter Bildung einer unlöslichen komplexen Metallsalz‐Pigment‐Harzverbindung. Als Bindemittel weden außer Polyvinylbutyrat auch andere Mischpolymerisate bzw. Kunstharze herangezogen. Als reaktive Komponente dient i. allg. Phosphorsäure, als antikorrosives Pigment Zn‐chromat. Ein Zusatz an lamellaren Pigmenten (Al‐pulver, Glimmer, Talkum) verbessert die Haftfähigkeit und Undurchlässigkeit des Schutzfilmes. Die reaktiven grundiermittel werden in dünner Schicht aufgebracht und erfordern bei stärkerer Korrosionsbeanspruchung des Gesamtanstriches noch Abdeckung mit antikorrosiven Grundierfarben. Sie ergeben auf Fe, Al, Leichtmetallen, verzinktem Fe einen antikorrosiven Deckfilm u. einen haftfesten Verankerungsgrund für die nach‐folgenden Farbschichten.
Korrosionschemisches Repetitorium. Der Einfluß der Außen‐ und Elektrolytwiderstände auf die Arbeitsweise elektrochemischer Modellelemente mit einer leicht polarisierbaren Elektrode
Authors: Schwarz Wolfram
Published: December 2004

Es wird dargestellt, wie die Widerstände im äußeren Stromkreis und im Elektrolyten die Potentiallage der Kathode, die Klemmspannung und ähnliche Größen beeinflusst. Abschließend wird ein Weg zur Aufnahme von Strom‐Spannungskurven in Elektrolyten mit geringer Leitfähigkeit gegeben und auf eine Variation der Bedingungen zur Erzielung von Porportionalität zwischen Strom und zu bestimmenden Stoff hingewiesen, die die Elementanordnung gleichzeitig in weitem Maße von dem Salzgehalt der Lösung unabhängig macht.
Über das Korrosionsverhalten von Eisen in hochkonzentrierter Salpetersäure
Authors: Fitzer Erich , Hohn Hans , Sekal Johann
Published: December 2004

Über den passiven Zustand von Eisen in Salpetersäure – Standversuche von Eisen in hochkonzentrierter Salpetersäure – Interkristalliner Zerfall von handelsüblichem Eisenblech in Hoko mit über 96 Gew. %HNO3 – Einfluß der Prüfbedingungen sowie der Vorbehandlung und der Zusammensetzung des Werkstoffes auf den interkristallinen Zerfall – Das Verhalten von Reinsteisen und von aufgekohltem Eisen gegenüber Hoko – Untersuchungen über die gasförmigen, gelösten und festen Zerfallsprodukte beim interkristallinen An‐griff von Eisen durch Hoko.
Der Werkstück‐Oberflächenschutz im Fabrikationsablauf des Maschinenbaus
Authors: Van Der Bruggen Burchard
Published: December 2004

Ungeschützte Werkstückoberflächen setzen in der Regel Rost an und verunreinigen schnell, insbesondere dort, wo es sich um rauhe Gußoberflächen handelt. Die Reinigung ist dann meist schwierig und auch teuer. Wirklich saubere Oberflächen werden aber auch dann nur selten erzielt.

Mit dem Haftvermögen des ersten Farbauftrages steht oder fällt der Aufwand für die Lackierung. In den Fällen, in denen die mechanische Bearbeitung des Stückes bereits erfolgte, ist die Benutzung rationeller Farbauftrags‐Verfahren nur selten möglich. Ein frühzeitiger Oberflächenschutz des Gusses kann deshalb sehr vorteilhaft sein. Er senkt die Kosten für Oberflächenreinigung und erhöht die Haltbarkeit des Farbauftrages. Er verbessert außerdem die Arbeitshygiene und fördert die Sauberkeit im Betrieb.

An zwei Beispielen werden der Aufwand und die Vorteile des Grundanstrichs im Fabrikationsablauf des Maschinenbaus aufgezeigt.
Einfluß von Feuchtigkeit und Wärme auf das druckelastische Verhalten von rohem und ölimprägniertem Preßspan
Authors: Köhler Walther
Published: December 2004

Im Rahmen einer größeren Untersuchung wurde der Einfluß der verschiedensten herstellungstechnischen Faktoren, wie Aufbaustoffe, Oberflächenbeschaffenheit, Mahlungsgrad und Kalanderdruck sowie der verschiedensten verarbeitungstechnischen Faktoren, wie Wärme und Feuchtigkeit auf das druckelastische Verhalten von rohen und ölimprägnierten handelsüblichen sowie Spezial‐Cellulose‐Produkten geklärt.
Zur Anwendung der Schallemissionsanalyse beim Zugversuch an Nickel‐ und Nickeldispersionsschichten
Authors: Wagner E. , Broszeit E. , Schwalbe H. J.
Published: December 2004

Nickel‐Siliciumkarbid‐Dispersionsschichten werden durch galvanische Mitabscheidung feinster SiC‐Partikel in eine Nickelmatrix hergestellt und überwiegend für den Verschleißschutz eingesetzt. Zur Beurteilung des Verschleißverhaltens dieses Verbundwerkstoffs interessiert u. a., inwieweit Haftkräfte in der Grenzfläche zwischen beiden Phasen vorhanden sind, und wie sich die Haftung auf die Versagensmechanismen der Schicht bei kritischer mechanischer Beanspruchung auswirkt. Zur Beurteilung dieses Einflusses und des allgemeinen Einflusses von Dispersionsteilchen wurden einige Zugversuche mit begleitender SEA an Nickelschichten ohne und mit SiC‐Einlagerungen durchgeführt.
Chirulen® — ein Halbzeug aus ultrahochmolekularem Polyäthylen für Implantate
Authors: Berzen J. , Braun G. , Spengler H.
Published: December 2004

Es wird eine zusammenfassende Darstellung über die Entwicklung der Gelenkplastik – insbesondere unter Berücksichtigung von Chirulen®– gegeben. Bei diesem Material handelt es sich um ein Halbzeug aus ultrahochmolekularem Polyäthylen mit sehr hohem Reinheitsgrad, das nach dem Ziegler‐Verfahren hergestellt wird. Es hat sich nach biologischen Prüfungen und klinischen Befunden wegen seiner günstigen physikalischen Eigenschaften als Prothesenmaterial gut bewährt. Seine besonderen Vorzüge sind, daß es

während des physiologischen Gangablaufes, bei dem am Schenkelkopf eine Druckkraft von etwa dem 5fachen Körpergewicht auftritt, hervorragende Gleit‐ und Verschleißeigenschaften zeigt, und

bei der Sterilisation mit γ‐Strahlen keine merkliche Änderung in den physikalischen Eigenschaften aufweist.

Die Tendenz, auch andere schadhafte Gelenke, wie Knie‐, Schulter‐, Ellenbogen, Hand‐ und Fingergelenke, durch eine Prothese zu ersetzen, nimmt stetig zu. Auch bei diesen Konstruktionen bietet sich die Kombination Metall/ultrahochmolekulares Polyäthylen besonders an.
An investigation of Stress corrosion cracking in MgAZ61 alloy in 3.5% NaCl + 2% K2CrO4 aqueous solution at room temperature
Authors: Moccari A. , Shastry C. R.
Published: December 2004

Effect of specimen orientation, heat treatment and applied potential on the stress corrosion susceptibility of magnesium AZ61 (Mg‐6.3% Al‐0.5% Zn‐0.20% Mn) alloy in an aqueous 3.5% NaCl + 2% K2CrO4 solution at room temperature was investigated. Stress corrosion times to failure were measured at different values of initial stress intensities using single edge (pre) cracked sheet tensile specimens and a modified tensometer. It was observed that while the specimen orientation has a significant effect on the measured values of stress corrosion threshold stress intensity, KIscc, the effect of varying the quench rate during heat treatment was minimal. Polarization measurements both in stressed and unstressed conditions, failed to reveal any significant effect of the applied stress intensity on the anodic polarization behavior of the alloy. However, measurements made under four different potentiostatic conditions showed a considerable increase in stress corrosion times to failure of the alloy. The results, together with fractographic observations of fractured specimen are discussed in terms of the mechanisms of stress corrosion cracking, in magnesium alloys.
Das Zeitstandverhalten des Stahles X 10 NiCrAlTi 32 20 bei hohen Temperaturen und langen Zeiten
Authors: Büchsenschütz R. , Poweleit B. , Thiessen W.
Published: December 2004

Die Ansprüche an die Leistungsfähigkeit der Werkstoffe für Chemieanlagen wachsen ständig. So ist neben dem Übergang zu großen Einheiten nicht nur ein Ansteigen der Drücke und Temperaturen zu verzeichnen, sondern aus technischen und wirtschaftlichen Gründen auch ein optimale Ausnutzung der Werkstoffeigenschaften. Bei den durch Druck und Temperatur höchstbeanspruchten Bauteilen muß die Lebensdauer anhand von Zeitstandfestigkeitskennwerten berechnet werden.

An dem austenitischen Werkstoff × 10 NiCrAlTi 32 20 wird versucht, anhand von Zeitstandfestigkeitsuntersuchungen, die im eigenen Langzeitversuch ermittelt sind, eine Aussage über die zeitabhängige Gefügeausbildung zu machen und daraus Schlüsse für den Einsatz dieses Werkstoffes zu ziehen.
Laboratory evaluation of the processing characteristics of rigid PVC compounds
Authors: Bowerman H. H. , McKelvey J. M.
Published: December 2004

A small scale screw extruder designed for laboratory extrusion studies has been developed and its performance characteristics with powder‐blended rigid PVC Compounds have been investigated.

The use of the extruder in determining the susceptibility of rigid PVC compounds to various die‐induced viscoelastic phenomena (fracture, sharkskin, and swell) is described.

An investigation of the phenomenon of “nerve” in rigid PVC extrusions has been carried out. It is concluded that nerve is associated with instabilities in the fluxing process occurring in the transition section of the extruder screw design, the operating variables of the process, and the processing characteristics of the compound.
Thermomechanical studies of polymer deformation part I: A New deformation calorimeter
Authors: Duvdevani I. J. , Biesenberger J. A. , Gogos C. G.
Published: December 2004

The purpose of this paper is to describe a new deformation calorimeter, which is based on differential thermometry and uses a flowing gas stream as a heat transfer medium which allows it to operate under near‐isothermal conditions. Also presented are some preliminary test measurements with a crosslinked polyurethane elastomer and crystalline polybutene‐1.
1969 SPE international award paper. Rheo‐optics on two continents—an example of international cooperation in science
Authors: Stein R. S.
Published: December 2004

Rheo‐optical techniques for the study of crystalline polymers, developed primarily in the United States and Japan, include dynamic birefringence, X‐ray diffraction, dichroism, light scattering, and fluorescence. These permit the characterization of the rates of orientation of crystals, amorphous regions, and crystalline superstructures. The application of these methods has permitted the formulation of a model for the deformation of crystalline polymers.
Combined tension‐torsion creep experiments on polycarbonate in the nonlinear range
Authors: Lai J. S. Y. , Findley W. N.
Published: December 2004

Constant stress creep and recovery experiments were performed in the nonlinear range under combined tension and torsion on a tubular specimen of polycarbonate. Nonlinear viscoelasticity theory was employed to describe the test results. It was found that the first three orders of stress terms and a power function of time adequately described the experimental results. The modified superposition principle satisfactorily predicted the recovery following creep. Recovery was almost complete in several days following two hours of creep.
Mechanical and optical properties of block polymers I. Polyester‐urethanes
Authors: Estes G. M. , Seymour R. W. , Huh D. S. , Cooper S. L.
Published: December 2004

The extraordinary physical properties exhibited by block polymers have been ascribed to the presence of a multiphase microstructure in which the higher modulus phase acts as a quasi‐crosslink or filler particle. Recently, the optical examination of these materials combined with mechanical testing has given investigatiors new insight into this complex morphology. In this investigation, simultaneous stress, strain, and birefringence data have been collected on a block polyester urethane elastomer. Stress‐softening is observed in cyclic stress‐strain experiments, giving rise to significant hysteresis in the stressstrain and birefringence‐stress curves. In these tests, prestrain causes a large increase in the stress‐optical coefficient, but has little effect on the strain‐optical coeffcient. As the temperature is increased, the strain‐optical coefficent decreases while the stress‐optical coefficient increases with the latter exhibiting a larger temperature dependence than predicted by the kinetic theory of rubber elasticity. The good agreement between the mechanical‐optical response of polyester urethanes and that of other block polymer systems provides further evidence of their morphological similarity.
Graft copolymers prepared by anionic techniques–a review
Authors: Heller J.
Published: December 2004

The synthesis of graft copolymers by anionic polymerization techniques is reviewed. Two basic procedures are described. In one a polymer having a reactive end‐group is prepared and allowed to react with another polymer having suitable functional groups. In the second procedure, anions are generated on a preformed polymer backbone and used to initiate the polymerization of subsequently added monomers.
Mathematics of linear‐temperature programmed, first order kinetics in peroxide catalyzed polymerizations
Authors: Willard P. E. , Alvarez M. , Cha L. C.
Published: December 2004

A mathematical solution for the Arrhenius temperature dependency for the first‐order decomposition of organic peroxide catalysts has been used to prepare computer‐generated data for concentration vs time when a linearly rising temperature program is used. The resulting plots, of a double exponential nature, are used to show the effects of heating rates and type of organic peroxide on peroxide concentration and polymerization reactions.
Dynamic mechanical properties of polyurethane block polymers
Authors: Huh Dong S. , Cooper Stuart L.
Published: December 2004

The dynamic mechanical properties of polyester and polyether urethane block polymers have been investigated at four frequencies (3.5, 11, 35 and 110 Hz) in the temperature range of — 150 to 200°C. The existence of a two phase structure was demonstrated in these systems by the observation of two major transition regions corresponding to (1) the glass transition temperature (Tg) of the ester or ether soft segments, and to (2) the softening temperature of the aromatic‐urethane hard segments. Several secondary relaxations were observed in addition to the two major relaxations. It was possible to assign molecular mechanisms to each of these relaxations. All relaxation phenomena were greatly influenced by the molecular weight of the prepolymer, weight percent of hard segments, and thermal history. An increase in the molecular weight of the prepolymer above 1,000 at constant hard segment content resulted in a semi‐crystalline material, which possessed a lower Tg for the macroglycol segments. Annealing to enhance crystallinity increased the Tg of the soft segments, consistent with the usual observation in semicrystalline homopolymers. These findings suggest that the relaxation mechanisms of polyurethane block polymers are not only influenced by the degree of crystallinity, but also by the nature of the domain structure.
Some observations on the flow behavior of polyvinyl chloride melts
Authors: Collins E. A. , Metzger A. P.
Published: December 2004

Melt studies on PVC systems at elevated temperature or long times are difficult. One consequence is that measurements may be possible only in the non‐Newtonian region. The results indicate that even in this case the melt viscosity can be related exponentially with the weight average molecular weight by the 3.4 power. Since literature data are scarce, attempts were made to extend the range by mixing polymers. This led to the complication of dispersity both on a molecular scale and on a macroscopic level. The latter point is particularly important for PVC studies since the polymers are frequently blended with materials having different viscosities.
Vibration etching, a method of evaluation of photoresist characteristics
Authors: Kolf G. , Laessig W.
Published: December 2004

A new method of etching is described, the principle of which is the vibration of the sample being etched within the etchant. Because only small samples can be used this method is not suitable for commercial etching. As a test procedure however it has several advantages: a small volume of etchant (about 100 cc) is sufficient, the pressure of etchant attack can be varied and measured continuously, and the temperature can easily be controlled. Examples are given to demonstrate that vibration etching can be applied for characterization as well as for control of photoresist giving data of etch resistance, etch factor, adhesion, flexibility. Also the characteristics of different etchants and the etch behavior of different metal substrates can easily be compared.
Low temperature dynamic mechanical properties of polyurethane‐polyether block copolymers
Authors: Illinger J. L. , Schneider N. S. , Karasz F. E.
Published: December 2004

Dynamical mechanical relaxation spectra of a number of polyurethane‐polyether block copolymers have been studied as a function of composition, temperature and frequency. At low temperatures these copolymers are characterized by a high glass‐like modulus which decreases to a much lower typically elastomeric value in a narrow temperature range. The latter is a function in certain cases of the composition of the polymer. The rubbery plateau is maintained up to at least 140°C. In addition, a secondary relaxation is observed around −130°C. These observations can be interpreted in terms of an overall structure consisting of a polyether matrix containing segregated polyurethane domains, the latter serving as physical crosslinks in the system at ambient temperatures and above.
Breaking energies of a nylon series subjected to high‐speed transverse impact
Authors: Wilde A. F. , Ricca J. J. , Rogers J. M. , Cole L. M.
Published: December 2004

In a study of the transient behavior of a series of nylon 6/6 yarns differing systematically in mechanical properties, the effects of high‐speed, transverse missile impact upon yarn specimens were observed by high‐speed photography. The loss in missile kinetic energy was determined directly from the reduction in missile velocity and was studied as a function of yarn tenacity and missile impact velocity. The shape of the missile energy loss curves was due to the partition of missile energy into yarn kinetic energy and yarn strain energy. The missile energy losses and yarn dynamic breaking strains were compared to static breaking energies and breaking strains for these yarns. The observed trends are discussed in terms of the differing yarn tenacities and test rates.
Effect of olefin structure on the vapor‐development of poly (olefin sulfones) under electron irradiation
Authors: Bowden M. J. , Thompson L. F.
Published: December 2004

The rate of vapor‐development of poly(olefin sulfones) subjected to electron beam irradiation is markedly, dependent upon the olefin structure. At room temperature, poly(butene‐1sulfone) and poly(cyclopentene sulfone) vapor‐develop at rates several orders of magnitude lower than, for example, poly(2‐methyl pentene‐1 sulfone). Differences in vapor development rate for the various sulfones are shown to be related to differing rates of depolymerization which, in turn, are related to differences in ceiling temperatures for polymer formation. Kinetic analysis indicates that the mechanism involves random scission followed by depropagation and bimolecular termination.
Porous fabric membranes for soil stabilization and drainage
Authors: Miano Ralph R.
Published: December 2004

This paper briefly reviews the technological status of civil engineering fabrics used for ground stabilization and drainage applications. The theory of how such fabrics work is used to illustrate the advantages of fabric‐containing designs over conventional construction techniques. A drainage project which could not have been completed except at an exorbitant cost without the use of a properly designed filter fabric is detailed, and the economic benefits of using fabrics under ordinary circumstances are also documented. Because fabrics work and because they save money, the outlook for civil engineering fabrics is extremely bright.
Degradation action of water on S‐glass
Authors: Hsu Andrew C. T. , Jemian W. A. , Wilcox R. C.
Published: December 2004

Glass fiber reinforced composites have been used to an increasing extent as structural components because of their high strength at relatively low densities. They are more resistant to moisture and weathering than most other structural materials. However, under environments of high humidity and temperature, glass fiber composites with an epoxy or polyester matrix lose a considerable fraction of their.strength‐ after a relatively short time. For high strength glass reinforced composites, the glass filaments are mostly of the S‐glass and E‐glass types. This investigation reports the solvent effect of water on S‐glass rovings (filament strands) and powders. S‐glass is the strongest silicate glass developed in the past decade, the composition of which in weight percent is: A12O3/MgO/SiO2 = 25/10/65. In the temperature range covered (30 to 50°C), analyses of aluminum, magnesium, and silicon in water after different time periods indicate that magnesium is preferentially leached out of S‐glass, either as filaments or as powders, by water. The concentrations of magnesium and silicon in the water reached 2 mg/litre or more depending on the temperature and length of contact time, while the aluminum concentration reached no more than 0.2 mg/litre. Decomposition products of the ingredients present in a composite, including the coupling and curing agents, could further complicate the degradation process. Rate relations are proposed and discussed based on the dissolution data.
Relationship between electron sensitivity and chemical structures of polymers as EB resists: Poly(lactam thioether) as new positive EB resists
Authors: Oguchi Kiyoshi , Yoneyama Sachiko , Sanui Kohei , Ogata Naoya , Takahashi Yoichi , Nakada Tomihiro
Published: December 2004

Poly(lactam thioether) was synthesized from tetrahydro‐1,4‐thiazepine‐5(4H)‐one by a ring opening reaction under various conditions and was evaluated as positive electron beam(EB) resist. It was found that poly(lactam thioether) was easily decomposed by EB irradiation. The decomposition by EB exposure may be attributed to cleavage of CS bonds in the polymer chains. The sensitivity of poly(lactam thioether) was influenced by prebake temperature, molecular weight, and developer, a high sensitivity of 5.3 × 10−6 coulomb/cm2 was observed with a good resolution of less than 1 μm. Poly(lactam thioether) showed a high sensitivity and a high resolution, and is suitable as a positive EB resist.
Free radical polymerization models for simulating reactive processing
Authors: Stevenson James K.
Published: December 2004

The generally accepted kinetic mechanism for free radical copolymerization was simplified by various assumptions and restrictions to give several realistic and easily evaluated models for the simulation of industrial molding. Six assumptions, including conversion‐dependent rate coefficients and constant comonomer concentration ratios, were used to obtain a simplified model. Special cases of this simplified model were obtained by the following additional constraints: (1) Restriction C, consecutive inhibition and radical generation reactions; (2) Restriction I, constant initiator decomposition rate; (3) Restriction Z, zero termination rate for free radicals; and (4) Restriction K or P, all rate coefficients independent of conversion or only polymerization rate coefficient dependent on conversion. For various combinations of these restrictions, the time and concentration variables in the simplified model are separated and solved; the separate solutions are then combined in various ways to give models capable of predicting a wide variety of behavior. Many of these models have analytical solutions that greatly facilitate the evaluation of rate constants. Models based on restrictions KCI, PCI, and PCZ are shown to give good agreement with isothermal DSC data plotted as reaction rate versus time and, in a more sensitive test, as reaction rate divided by monomer concentration versus fractional conversion. Because of their predictive ability and ease of evaluating constants. Models PCI and PCZ are recommended for simulating industrial processing; they are particularly well suited for simulating compression molding of sheet molding compound.
Effect of bulk structure of amino silane primer on the strength and durability of aluminum/epoxy joints
Authors: Kaul A. , Sung N. H. , Chin I. J. , Sung C. S. P.
Published: December 2004

The strength and durability in wet environment of aluminum/epoxy/aluminum joints are investigated as a function of structural changes of γ aminopropyltriethoxy silane (γ‐APS) primer at the interface. Both dry and wet strengths exhibit strong dependencies on both the thickness and the extent of drying of γ‐APS prior to joint formation. Generally, dry strength decreases with increasing thickness of γ‐APS primer, and increases with dehydration of γ‐APS at any given thickness. Strength retention of the joints after exposure to water at 55°C also improves dramatically when the adsorbed γ‐APS is extensively dried. These results are analogous to earlier observations with α‐Al2O3/polyethylene joint system. In aluminum joints, porous oxide substrate facilitates the mechanical interlocking mechanism, and its interplay with both the thickness and the extent of cure of γ‐APS is analyzed by characterizing the fractured surfaces using scanning electron microscopy (SEM) electron spectroscopy for chemical analysis (ESCA).
Analysis of dispersion of carbon black in polymeric melts and its effect on compound properties
Authors: Rwei Syang‐Peng , Manas‐Zloczower Ica , Feke Donald L.
Published: December 2004

The dispersion of carbon black agglomerates within melts of polystyrene and high density polyethylene has been investigated. Analysis of the evolution of the fragment size distribution indicates that a coarse rupturing of the agglomerates occurs during the early stages of the dispersion. This is followed by a more gradual erosion of small aggregates from larger fragments. These observations compare quantitatively with results of dispersion studies performed in fluid media having a viscosity two orders of magnitude smaller than that of the polymeric melts. The influence of dispersion quality on certain physical properties of the resulting polymeric compounds, namely UV absorption characteristics and tensile strength properties, is also quantified.
A novel chemically amplified positive deep UV photoresist with significantly reduced sensitivity to environmental contamination
Authors: Chatterjee Subhankar , Jain Sangya , Lu Ping H. , Khanna Dinesh N. , Potvin Robert E. , McCaulley James A. , Rafalko Joseph
Published: December 2004

t‐Boc protected Deep‐UV transparent polymers with photoacid generators have been widely investigated as potential positive deep‐UV resist systems. However, utility of these systems is seriously handicapped by environmental contaminants leading to an insoluble “surface skin” formation. Only with a specially controlled environment or by use of an “overcoat” material is the performance of these systems acceptable. We have investigated a series of t‐Boc protected poly(styrene‐maleimide) copolymers and poly(hydroxy styrene) polymers with onium‐salts. Upon incorporation of a special class of organic additive, the surface effects inherent to these positive deep‐UV systems are significantly reduced thereby avoiding any extraneous precaution of protecting the resist surface from a typical manufacturing environment. We evaluated these t‐Boc polymer/onium‐salt systems with different additives under a varied set of processing conditions. In addition, plausible structure‐activity relationship of these additives in controlling the surface effects is presented.
The thermal deprotection process in an e‐beam exposed phenolic‐based polymer
Authors: Long Treva , Obendorf S. Kay , Rodriguez Ferdinand
Published: December 2004

In our current work, we have examined the e‐beam sensitivity and thermal processing behavior of pure PBOCST [poly(tert‐butoxycarbonyloxystyrene)]. An alkali soluble latent image can be generated in the PBOCST by e‐beam exposure followed by a post‐exposure bake (PEB) at relatively high temperatures (140 to 150°C). Pattern wet development operates on the same basis as a PBOCST/acid generator two component system. Deprotection, accelerated by the exposure, yields alkali soluble areas, while unexposed areas remain insoluble. Sensitivities of 5 to 10°C/cm2 and contrasts of 6 to 10 have been measured. Complete TBOC deprotection results in a film thickness loss of 35 to 40% as CO2 and isobutene are evolved. A laser interferometer/hotplate setup was used to track film thickness with time during the thermal deprotection process. IR analysis confirmed the correlation between conversion and thickness. It was found that a slow initial conversion rate was followed an exponentially steep rise in rate after 50% conversion. Activation energies were on the order of 30 kcal/mol. It was concluded that thermolysis in both exposed and unexposed resist occurred during the PEB, but that the difference in extent of conversion on exposure was sufficient to generate a pattern.
Ueber alkylirte Toluidinsulfonsäuren
Authors: Schmidt R.
Published: December 2004

1. Durch Einwirkung von Bromäthyl auf p‐toluidin‐o‐ und m‐sulfonsaures Kalium entstehen zwei isomere Körper von der Zusammensetzung einer Diäthyltoluidinsulfonsäure. Von diesen erwies sich das Derivat der Orthosäure als eine charakteristische, nicht schmelzbare Säure, welche im Stande war, sowohl mit Alkalien, als alkalischen Erden Salze zu bilden. Der Abkömmling der Metasäure hingegen schmilzt und besitzt nur schwach saure Eigenschaften; er liefert nur ein Kaliumsalz, während Salze von alkalischen Erden nicht aus ihm erhalten werden konnten.
Über die Benzylmalimide von Giustiniani
Authors: Lutz O.
Published: December 2004

Beim Erhitzen von saurem äpfelsauren Benzylamin entsteht nur ein linksdrehendes Imid im Gemenge mit seinem racemischen Isomeren. Das „α‐Imid”︁ von Giustiniani existiert nicht.

Aus dem Imidgemenge läßt sich durch fraktionierte Kristallisation aus Wasser ein reines aktives Imid nicht gewinnen. Das Imid von Ladenburg und Herz vom Schmelzpunkt 102° ist kein Individuum, sondern ein Gemisch aus 1‐ und r‐Benzylmalimid.

Die optisch‐isomeren Benzylmalimide lassen sich in reiner Form aus den entsprechenden Benzylmalamidsäuren leicht darstellen.
Über Beziehungen zwischen Konstitution, Farbe und Absorptionsspektrum bei Triphenylmethanfarbstoffen
Authors: Reitzenstein Fritz , Schwerdt Walther
Published: December 2004

I. In einfachen Triphenylmethanfarbstoffen, deren eine Komponente

(A)Tetramethyldiamidobenzhydrol ist, übt die

Nitrogruppe bei gleichzeitiger Anwesenheit einer Amido‐ und Methylgruppe folgenden Einfluß aus:

in Orthostellung findet Schwächung der Farbe statt

in Metastellung wird der Farbton verstärkt

Chlor

in Orthostellung: die Farbe wird reiner und intensiver,

in Metastellung wird der Farbton verstärkt

in Parastellung: der Farbton wird tiefer und klarer.

die Sulfogruppe:

in Orthostellung: Schwächung des Farbtons mit Hinüberziehen nach Grün,

in Metastellung wird der Farbton verstärkt

in Parastellung: der Farbton wird tiefer und klarer.
Beiträge zur Kenntnis der Metall‐Silicate. II. Über die Umsetzungen zwischen Natriumsilicat und Metallsalzlösungen
Authors: Jordis Eduard , Hennis W.
Published: December 2004

Die Umsetzungen zwischen CuSO4 FeSO4 FeCl3 und Na2SiO3 in wäßrigen Lösungen verlaufen nicht im Sinne der Gleichungen, die man dafür aufstellen kann.
Zur Kenntnis der Cyanverbindungen der Platinmetalle. III. Über die Cyanverbindungen des Osmiums
Authors: Krauss F. , Schrader G.
Published: December 2004

1. In Bestätigung der älteren Literaturangaben wird festgestellt, daß die Doppelcyanide des Osmiums sich von der Säure H4[Os(CN)6] ableiten, das Osmium in diesen Verbindungen also zweiwertig ist.