bluuebunny/crossref_metadata_2025 huggingface dataset:
Functionalization of LDPE by Melt Grafting with Glycidyl Methacrylate and Reactive Blending with Polyamide‐6
Authors: Wei Qian , Chionna Donatella , Galoppini Elena , Pracella Mariano
Published: May 2003

Low‐density polyethylene (LDPE) was functionalized by melt radical grafting with glycidyl methacrylate (GMA) and employed for reactive blending with polyamide‐6 (PA6). The effect of the reaction procedure on the grafting degree of LDPE‐g‐GMA samples (0.5–12.5 wt.‐% GMA) was analyzed as a function of the concentration of GMA monomer, radical initiator (BTP), and addition of styrene as co‐monomer. Optimized grafting conditions were obtained when the amount of the monomer is below 10 wt.‐% and that of peroxide in the range 0.2–0.4 wt.‐%. Binary blends of PA6 with LDPE‐g‐GMA (3.5 wt.‐% GMA) and with LDPE at various compositions (80/20, 67/33, 50/50 wt.‐%) were prepared in an internal mixer and their properties were evaluated by torque, SEM and DSC analyses. Morphological examination by SEM showed a large improvement of phase dispersion and interfacial adhesion in PA6/LDPE‐g‐GMA blends as compared with PA6/LDPE blends. The average diameter of dispersed polyolefin particles was about 0.4 μm for LDPE‐g‐GMA contents < 50 wt.‐%. A marked increase of melt viscosity was observed for the compatibilized blends depending on the concentration of grafted polyolefin, and it was accounted for by the reaction between the epoxy groups of GMA and the carboxyl/amine end‐groups of PA6. The variation of torque was thus related to the molar ratio of reactive group concentration. The analysis of crystallization and melting behavior pointed out marked differences in the phase structure of the blends due to the presence of the functionalized polyolefin. Finally, the in situ formation of a graft copolymer between LDPE‐g‐GMA and PA6 was investigated by means of a selective dissolution method (Molau test) and by FT‐IR and DSC analyses.

SEM micrograph of fracture surface of PA6/LDPE‐g‐GMA 50/50 blend.

magnified image

SEM micrograph of fracture surface of PA6/LDPE‐g‐GMA 50/50 blend.
A splitting theorem for the Medvedev and Muchnik lattices
Authors: Binns Stephen
Published: May 2003

This is a contribution to the study of the Muchnik and Medvedev lattices of non‐empty Π01 subsets of 2ω. In both these lattices, any non‐minimum element can be split, i. e. it is the non‐trivial join of two other elements. In fact, in the Medvedev case, ifP > M Q, then P can be split above Q. Both of these facts are then generalised to the embedding of arbitrary finite distributive lattices. A consequence of this is that both lattices have decidible ∃‐theories.
Negation and BCK‐algebras
Authors: García Olmedo Francisco M. , Rodríguez Salas Antonio J.
Published: May 2003

In this paper we consider twelve classical laws of negation and study their relations in the context of BCK‐algebras. A classification of the laws of negation is established and some characterizations are obtained. For example, using the concept of translation we obtain some characterizations of Hilbert algebras and commutative BCK‐algebras with minimum. As a consequence we obtain a theorem relating those algebras to Boolean algebras.
Categorical abstract algebraic logic: The criterion for deductive equivalence
Authors: Voutsadakis George
Published: May 2003

Equivalent deductive systems were introduced in [4] with the goal of treating 1‐deductive systems and algebraic 2‐deductive systems in a uniform way. Results of [3], appropriately translated and strengthened, show that two deductive systems over the same language type are equivalent if and only if their lattices of theories are isomorphic via an isomorphism that commutes with substitutions. Deductive equivalence of π‐institutions [14, 15] generalizes the notion of equivalence of deductive systems. In [15, Theorem 10.26] this criterion for the equivalence of deductive systems was generalized to a criterion for the deductive equivalence of term π‐institutions, forming a subclass of all π‐institutions that contains those π‐institutions directly corresponding to deductive systems. This criterion is generalized here to cover the case of arbitrary π‐institutions.
Generic separations and leaf languages
Authors: Galota Matthias , Kosub Sven , Vollmer Heribert
Published: May 2003

In the early nineties of the previous century, leaf languages were introduced as a means for the uniform characterization of many complexity classes, mainly in the range between P (polynomial time) and PSPACE (polynomial space). It was shown that the separability of two complexity classes can be reduced to a combinatorial property of the corresponding defining leaf languages. In the present paper, it is shown that every separation obtained in this way holds for every generic oracle in the sense of Blum and Impagliazzo. We obtain several consequences of this result, regarding, e. g., universal oracles, simultaneous separations and type‐2 complexity.
Expanding the additive reduct of a model of Peano arithmetic
Authors: Murakami Masahiko , Tsuboi Akito
Published: May 2003

Let M be a model of first order Peano arithmetic (PA) and I an initial segment of M that is closed under multiplication. LetM0 be the {0, 1,+}‐reduct ofM. We show that there is another model N of PA that is also an expansion of M0 such that a · M a = a · N a if and only if a ∈ I for all a ∈ M.
Some weak forms of the Baire category theorem
Authors: Kermedis Kyriakos
Published: May 2003

We show that the statement (K12) “separable, countably compact, regular spaces are Baire” is deducible from a strictly weaker form than AC, namely, CAC(ℝ) (the axiom of choice for countable families of non‐empty subsets of the real line ℝ). We also find some characterizations of the axiom of dependent choices.
Characterizing strong compactness via strongness
Authors: Apter Arthur W.
Published: May 2003

We construct a model in which the strongly compact cardinals can be non‐trivially characterized via the statement “κ is strongly compact iff κ is a measurable limit of strong cardinals”. If our ground model contains large enough cardinals, there will be supercompact cardinals in the universe containing this characterization of the strongly compact cardinals.
Arithmetical definability over finite structures
Authors: Lee Troy
Published: May 2003

Arithmetical definability has been extensively studied over the natural numbers. In this paper, we take up the study of arithmetical definability over finite structures, motivated by the correspondence between uniform AC0and FO(PLUS, TIMES). We prove finite analogs of three classic results in arithmetical definability, namely that < and TIMES can first‐order define PLUS, that < and DIVIDES can first‐order define TIMES, and that < and COPRIME can first‐order define TIMES. The first result sharpens the equivalence FO(PLUS, TIMES) =FO(BIT) to FO(<, TIMES) = FO(BIT), answering a question raised by Barrington et al. about the Crane Beach Conjecture. Together with previous results on the Crane Beach Conjecture, our results imply that FO(PLUS) is strictly less expressive than FO(<, TIMES) = FO(<, DIVIDES) = FO(<,COPRIME). In more colorful language, one could say that, for parallel computation, multiplication is harder than addition.
ω‐categorical weakly o‐minimal expansions of Boolean lattices
Authors: Leonesi Stefano , Toffalori Carlo
Published: May 2003

We study ω‐categorical weakly o‐minimal expansions of Boolean lattices. We show that a structure 𝒜 = (A,≤, ℐ) expanding a Boolean lattice (A,≤) by a finite sequence I of ideals of A closed under the usual Heyting algebra operations is weakly o‐minimal if and only if it is ω‐categorical, and hence if and only if A/I has only finitely many atoms for every I ∈ ℐ. We propose other related examples of weakly o‐minimal ω‐categorical models in this framework, and we examine the internal structure of these models.
On semilattice relevant logics
Authors: Kashima Ryo
Published: May 2003

The semilattice relevant logics ∪R, ∪T, ∪RW, and ∪TW (slightly different from the orthodox relevant logics R, T, RW, and TW) are defined by semilattice models in which conjunction and disjunction are interpreted in a natural way. For each of them, there is a cut‐free labelled sequent calculus with plural succedents (like LK). We prove that these systems are equivalent, with respect to provable formulas, to the restricted systems with single succedents (like LJ). Moreover, using this equivalence, we give a new Hilbert‐style axiomatizations for ∪R and ∪T and prove equivalence between two semantics (commutative monoid and distributive semilattice) for the contractionless logics ∪RW and ∪TW.
A probabilistic extension of intuitionistic logic
Authors: Marković Zoran , Ognjanović Zoran , Rašković Miodrag
Published: May 2003

We introduce a probabilistic extension of propositional intuitionistic logic. The logic allows making statements such as P≥sα, with the intended meaning “the probability of truthfulness of α is at least s”. We describe the corresponding class of models, which are Kripke models with a naturally arising notion of probability, and give a sound and complete infinitary axiomatic system. We prove that the logic is decidable.
On two questions about feasibly constructive arithmetic
Authors: Moniri Morteza
Published: May 2003

IPV is the intuitionistic theory axiomatized by Cook's equational theory PV plus PIND on NP‐formulas. Two extensions of IPV were introduced by Buss and by Cook and Urquhart by adding PIND for formulas of the form A(x) ∨ B, respectively ¬¬A(x), where A(x) is NP and x is not free in B. Cook and Urquhart posed the question of whether these extensions are proper. We show that in each of the two cases the extension is proper unless the polynomial hierarchy collapses.
The discrete parts of approximately decidable sets in Euclidean spaces
Authors: Hemmerling Armin
Published: May 2003

It is shown that the classes of discrete parts, A ∩ ℕk, of approximately resp. weakly decidable subsets of Euclidean spaces, A ⊆ ℝk, coincide and are equal to the class of ω‐r. e. sets which is well‐known as the first transfinite level in Ershov's hierarchy exhausting Δ02.
Biospecific Properties of Random Copolymers, 2
Authors: Bouzou Bérengère , Pflüger Fernando
Published: May 2003

Previous results obtained have shown that it was possible to create biospecific sites onto polymers through statistic modifications of polystyrene derivatives copolymer with given chemical groups or through synthesis of random methacrylate‐based copolymers. Such polymers show biological activities (anticoagulant, cell proliferation modulation …) dependent of the global composition and thus of the statistical distribution of the functional groups, and the number of biospecific sites is simply correlated to the observed biological activity. The study of the radical terpolymerization allows us to use a Monte Carlo based synthesis simulation and to determine the occurrence frequency of three to twenty monomers sequences as a function of the conversion rate and the global composition. The comparison of the sequences occurrence curves as a function of the global composition of the polymers with the experimental cell proliferation inhibition curve led us to extract a series of eight monomers sequences with similar structure properties representing a group of biospecific sites responsible for the observed biological activity.

Radical terpolymerization of MMA, MA, and NaSS in DMSO initiated by AIBN.

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Radical terpolymerization of MMA, MA, and NaSS in DMSO initiated by AIBN.
Mesophase Formation in Solutions of Diblock Copolymers Simulated Using the Bond Fluctuation Model
Authors: Freire Juan J. , McBride Carl
Published: May 2003

The behavior of symmetric diblock copolymer chains of two different lengths at different concentrations is simulated by means of the bond fluctuation model. Two alternative sets of energies between interacting neighbors are proposed. In one of the sets, attractions between monomers of the same type are considered. In the other set, repulsions between monomers of different types are considered. The collective scattering of the simulation boxes is computed for different values of the reduced energy interaction parameter and the total polymer volume fraction. The analysis of this property is used to locate the transition associated with the formation of mesophases (lamellae) as a function of these two variables. A comparison between the results corresponding to the two different models is performed. When the significant excluded volume corrections are introduced in the model with repulsive interactions, both sets of data agree, except for the most dilute samples. The agreement with the self‐consistent field theory is only fair, and important differences are observed in the intermediate concentration regime. These differences were expected, since the theoretical treatment is only rigorously valid for very long chains.

Comparison of the simulation data for the transition points with the prediction of the self‐consistent field theory (solid line).

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Comparison of the simulation data for the transition points with the prediction of the self‐consistent field theory (solid line).
Pseudostationary Pulsed Laser Polymerization: A Simple Method for the Direct Determination of Axial Dispersion as Occurring in Size Exclusion Chromatography
Authors: Kornherr Andreas , Olaj Oskar Friedrich , Schnöll‐Bitai Irene , Zifferer Gerhard
Published: May 2003

Theoretical distribution curves were calculated for several values of pulse separation t0 and concentrations of initiating radicals ρ formed by each pulse for both types of termination (disproportionation and combination). The absolute and relative peak widths of the additional peaks for the number, molar mass, and hyperdistribution were determined and compared. In all cases, the peak widths of these different distributions became the same with increasing values of C = ktρt0 and/or L0 = kp[M]t0, with [M] = monomer concentration and kt and kp are the rate constants of termination and propagation, respectively. This is similar to the behavior of Poisson distributions if only the degrees of polymerization are fairly high (P̄n ≥ 50). The analogy is further supported by the finding that under the same conditions the peak widths themselves approach the theoretical ones for Poisson distributions. Thus, the fulfilment of these two criteria suggests that the various peaks in multimodal distributions should be treated in the same formal way as Poissonian peaks although they clearly originate from a superposition of adjacent Poissonian peaks of different amplitude and, on the whole have a peak width somewhat in excess of the theoretical one of true Poisson peaks of the same P̄n. The point of inflection can be used as a measure of L0 without reservation only if the first criterion is not fulfilled. The influence of axial dispersion on the location of the extrema was calculated by use of standard deviations σad,k (0.05 and 0.025) to give “experimental curves” for which a pronounced increase in the absolute and relative peak widths was observed. Based on an assumed additivity of the peak variances, a simple procedure was tested for the direct determination of σad,k. The accuracy increased with increasing peak chain lengths and C values for those values determined from the first peak. The values determined from the second peak in the chain length region between 400–700 were closest to the input value.

The points of inflection on the low and high molecular weight side of the additional first three peaks are given as a function of the peak maximum. The lower and upper lines were calculated with Equation (11) and (12), respectively.

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The points of inflection on the low and high molecular weight side of the additional first three peaks are given as a function of the peak maximum. The lower and upper lines were calculated with Equation (11) and (12), respectively.
Die γ2‐Phase und ihre Effekte auf die Eigenschaften heterogener Mehrstoffaluminiumbronzen
Authors: Benkißer G. , Ladewig C. , Rühl I.
Published: May 2003

In diesem Bericht werden die Effekte der chemischen Zusammensetzung und der Herstellung und Verarbeitung auf das Gefüge und einige Eigenschaften heterogener Mehrstoffaluminiumbronzen dargestellt. Insbesondere werden die Entstehung und die Erscheinungsformen der γ2‐ Phase in den Gefügen und die Beziehungen zwischen den Gefügen und den Eigenschaften der Legierungen beschrieben.
Verschleißbeständige MMC mit in situ Karbiden
Authors: Wewers B. , Berns H.
Published: May 2003

Verschleißbeständige Hartverbundwerkstoffe bestehen aus einem Verbund von Hartpartikeln, die in einer weicheren Metallmatrix eingebettet sind. Die Hartpartikel tragen zur Erhöhung des Verschleißwiderstandes bei, die Matrix liefert die notwendige Unterstützung und Duktilität. Die Wirksamkeit der Hartpartikel hängt neben ihrer Verteilung und ihrem Volumengehalt in der Matrix von ihrer Härte und Größe ab. Die Auswahl an kommerziell erhältlichen wirksamen Hartpartikeln ist zum Einen begrenzt und zum Anderen ist ihr Preis im Vergleich zum Preis des Matrixpulvers um ein Vielfaches höher. Aus diesem Grund war es das Ziel der vorliegenden Arbeit, die Auswahl an kostengünstigen wirksamen Hartpartikeln zu erweitern.

Es wird ein neues pulvermetallurgisches Herstellungsverfahren vorgestellt, bei dem nicht Hartstoffpulver, sondern handelsübliche Ferrolegierungspulver mit und ohne Zugabe von Kohlenstoff mit verschiedenen härtbaren Stahlmatrixpulvern gemischt und anschließend heiß isostatisch gepresst (HIP) werden. Während des HIP‐Prozesses bildet sich durch die Diffusion von C in die Ferropartikel in situ ein Stahlmatrix‐ Karbid‐Verbundwerkstoff.

Die durchgeführten Untersuchungen zeigen, dass in tribologisch hoch aber mechanisch, bzw. thermozyklisch gering beanspruchten Werkzeugen die Werkstoffneuentwicklung ein interessantes und kostengünstiges Potential bietet.
Improved fatigue resistance of pseudo‐elastic NiTi alloys by thermo‐mechanical treatment
Authors: Hornbogen E. , Heckmann A.
Published: May 2003

Shape memory alloys are susceptible to two types of fatigue in addition to classical fatigue: 1. Pseudo‐elastic fatigue leads to an increase in the slope of the pseudo‐elastic plateau and final loss of pseudo‐elasticity 2. A change in transformation temperature. Usually the martensite temperature is lowered with the number of cycles until final loss of transformability. This paper describes measures to improve stability against both types of fatigue. Such methods are simple ageing in order to achieve precipitation in austenite, and thermo‐mechanical treatments such as ausforming that introduce lattice defects into austenite, which transforms subsequently into martensite. Another method consists in the introduction of defects into martensite by marforming plus subsequent ageing. This ageing treatment has two purposes. It increases the classical strength and restores the β‐phase from residual martensite and consequently it recreates transformability. It is shown that the last mentioned method leads to the greatest effect in respect to stabilisation against both types of fatigue. An additional effect of these treatments is a transition of localised to more homogeneous strain. Its relevance for fatigue resistance is still under investigation.
Shear Creep Deformation of the Super Alloy Single Crystal CMSX‐4 at High Temperatures and Low Stresses
Authors: Kamaraj M. , Serin K. , Kolbe M. , Neuking K. , Eggeler G.
Published: May 2003

In the present paper we investigate the shear creep behavior of the single crystal super alloy CMSX‐4 at temperatures between 950 and 1100 °C and shear stresses ranging from 80 to 155 MPa. A double shear creep test technique is used to study the shear creep behavior of four specific macroscopic crystallographic shear systems defined by a specific crystallographic shear plane and a specific crystallographic shear direction (systems investigated: {001}<110>, {100}<010>, {011}<01‐1>, and {111}<01‐1>). The shear creep behavior is analyzed in terms of the shape of individual creep curves and in terms of the stress and the temperature dependence of the secondary shear creep rate. Individual creep curves are generally characterized by a pronounced primary creep range where creep rates decrease by up to three orders of magnitude. A sharp creep rate minimum is not observed. The secondary creep range starts at shear stresses of the order of 0.02 and is followed by a secondary creep range which extends over shear strain ranges of the order of 0.1. No pronounced increase of shear creep rate in the later stages of creep is observed. Norton plots yield power law stress exponents ranging from 5.5 to 9.7. The temperature dependence of the secondary creep rate is of an Arrhenius type and apparent activation energies between 549 and 690 kJ/mol were found. There is a clear influence of crystallography on shear creep rates, which vary between different macroscopic crystallographic shear systems; this effect decreases with increasing temperature. The shear creep results obtained in the present study are discussed in the light of results from uniaxial testing and in the light of underlying microscopic deformation processes.
Analysis of spray formed tool steels
Authors: Schulz A. , Matthaei‐Schulz E. , Spangel S. , Vetters H. , Mayr P.
Published: May 2003

The technique of atomising liquid metal and compacting the micro‐droplets to a billet on a rotating support combines advantages from cast, wrought and powder metallurgical materials. A production rate of several tons per hour requires precisely controlled processing routines. Important process parameters based on processing, manufacturing and application of spray formed material are now developed by fundamental investigations established in projects focused in a special co‐operative research program (SFB 372) at the University of Bremen which is funded by the Deutsche Forschungsgemeinschaft (DFG). By this method advanced alloys of high hardness can be formed without inhomogeneities like segregations and pores in the center of the ingot. By example of tool steels the influence of spray forming on microstructure and homogeneity of the elemental distribution is shown.
Deposition and heat treatment of CuAlNi shape memory thin films
Authors: Wu X. , Kutschej K. , Kneissl A. C.
Published: May 2003

CuAlNi thin films were fabricated by magnetron sputtering process. After heat treatment, the thin films presented a shape memory effect. Calowear method was used to measure the thickness of the thin films. SEM, XRD and TEM were used to characterize the thin films. The phase transformation in the thin films was examined by DSC. The deposition rate increased with increasing sputtering power and decreased with increasing Ar pressure. Compared to the composition of the target, both the content of Al and the content of Ni increased a little. The sputtering conditions had little influence on the content of Ni. The content of Al varied slightly with sputtering power, while decreased with increasing Ar pressure. The deposited thin films were columnar. The grain size was very fine. The phases were α‐Cu and α2. After heat treatment at 800 oC/ 60 min + 300 oC/ 60 min in vacuum, CuAlNi shape memory thin films were obtained. The phase in the heat‐treated thin films was β1’ martensite. Martensite transformation was observed and a two‐way shape memory effect could be shown.
Ein einfacher Festigkeitsversuch für Scheiben aus spröden Werkstoffen
Authors: Danzer R. , Börger A. , Supancic P. , Ruiz Villanueva M. A.
Published: May 2003

Der 4‐Kugel Versuch ist eine einfache Möglichkeit zur Festigkeitsprüfung von Scheiben aus spröden Werkstoffen. Eine scheibenförmige Probe wird an einer Deckfläche an drei Punkten gelagert und an der gegenüberliegenden Deckfläche mittig belastet. Die Lagerung und die Lasteinleitung wird durch kugelförmige Teile realisiert. Die Vorrichtung weist eine dreizählige Symmetrie auf. In dieser Arbeit wird die Vorrichtung zur Prüfung von Aluminiumoxidproben verwendet. Dabei wird die Größe der Proben, das Dicken zu Durchmesserverhältnis und die Auflagersituation der Proben systematisch verändert. Es war möglich, die numerischen Berechnungen zur Ermittlung der maximalen Spannung in den Scheiben durch Bruchexperimente zu bestätigen. Dabei mußte das Weibullverhalten der Keramik berücksichtigt werden.

Vorzüge des 4‐Kugelversuchs liegen vor allem in der großen Toleranz des Verfahrens gegenüber kleinen Abweichungen der tatsächlichen von der idealen Testgeometrie, der Möglichkeit, leicht verbogene Scheiben und damit auch unbearbeitete Sinterkörper zu testen, der geringen Reibung und dem großen Potential, auch besonders kleine Proben zu prüfen. Als Nachteil ist im Vergleich zur herkömmlichen Biegeprüfung von Balken vor allem die aufwendigere Auswertung der Ergebnisse anzuführen.
Auswirkungen von statischen Langzeitglühungen auf Gefüge und mechanische Eigenschaften einer γ‐TiAl Basislegierung
Authors: Beschliesser M. , Jeglitsch F. , Kestler H. , Clemens H.
Published: May 2003

In dieser Arbeit werden die Ergebnisse von statischen Langzeitglühungen (700 °C bzw. 800 °C bis zu 10.000 Stunden an Luft) anhand eines volllamellaren Gefüges (Designed Fully Lamellar, DFL) der pulvermetallurgisch hergestellten Ti‐46.5Al‐4(Cr,Nb,Ta,B) Legierung dargestellt. Das Ziel dieser Arbeit ist es, mögliche Gefügeveränderungen und deren Auswirkungen auf die mechanischen Eigenschaften der γ‐TiAl Basislegierung als Funktion der Auslagerungstemperatur und ‐zeit zu beschreiben und mit thermodynamischen Berechnungen zu vergleichen. Mit Hilfe der thermodynamischen Berechnungen mittels der Software ThermoCalc ist es möglich, für eine gegebene Legierung Phasenanteile und Zusammensetzung der konstituierenden Phasen im Gleichgewicht zu berechnen. Nach sehr langen Auslagerungszeiten kann davon ausgegangen werden, dass Menge und Art der konstituierenden Phasen der untersuchten Legierung einen Gleichgewichtswert angenommen haben. Daneben wurden, ebenfalls in Abhängigkeit der Auslagerungstemperatur und ‐zeit, die mechanischen Eigenschaften im Zugversuch bei Raumtemperatur und bei 700 °C in Vakuum ermittelt.
Microstructural characterization of INCOLOY alloy MA 956
Authors: Hupalo M. F. , Terada M. , Kliauga A. M. , Padilha A. F.
Published: May 2003

Oxide dispersion strengthened (ODS) ferritic materials obtained by mechanical alloying (MA) display particular microstructure and texture. In this paper a microstructural characterization of an INCOLOY MA 956 alloy in the recrystallized (zone annealed) condition is presented. The alloy exhibits a highly anisotropic microstructure, consisting of elongated grains with a high grain aspect ratio (GAR). The alloy also exhibited strong crystallographic texture. The crystallographic direction <111> was approximately parallel to the extrusion direction of the material. The yttria particles, added to the starting powders, react with aluminum and oxygen present in the system during thermomechanical processing and form mixed (Y,Al) oxides. The analysis of extracted particles showed that the majority of yttrium‐aluminum oxides were tetragonal (Y3Al5O12) and orthorhombic (AlYO3). Quantitative analysis using TEM micrographs showed two classes of dispersoid sizes.
Tribokorrosionsverhalten von mehrphasigen Bronzen
Authors: Tikana L. , Dago L. G. , Heßing C.
Published: May 2003

Die Tribokorrosion ist bei erosionsgefährdeten Bauteilen eine Erscheinung, die dann auftreten kann, wenn das Zwischen‐ bzw. Umgebungsmedium chemisch reaktiv ist. Das ist insbesondere der Fall, wenn der Werkstoff in den entsprechenden Medien passiviert. Die vom Werkstoff gebildete Passivschicht, die einen Korrosionsschutz gewährt, wird bei der tribologischen Beanspruchung abgetragen und nach erneuter Bildung immer wieder zerstört.

Mehrphasige Bronzen des Typs Cu‐Al‐Ni‐Fe werden im Bereich der Meerestechnik, der Offshoretechnik und der chemischen Industrie eingesetzt. Sie können als Schiffspropeller‐, Turbinenschaufel‐ und Strömungsleitungswerkstoff der Erosion ausgesetzt sein.

In der vorliegenden Arbeit wird das Tribokorrosionsverhalten dieser mehrphasigen Bronzen am Beispiel der Legierung CuAl10Ni5Fe5 untersucht. Das allgemeine Korrosionsverhalten des gewählten Werkstoffes in Laugen und Meerwasser ist in der Regel gut. Ist aber der Korrosionsbeanspruchung eine tribologische überlagert, so kann es zu Tribokorrosion kommen. Die Legierung wurde in den o.g. Medien einer Kavitationsbeanspruchung unterzogen und die auftretenden Mechanismen untersucht. Dabei zeigte sich, dass je besser das Passivierungsverhalten war, um so tribokorrosionsanfälliger war der Werkstoff.
Kerbformoptimierung ohne FEM: Ein einfacher Weg, um Kerbspannungen abzubauen
Authors: Mattheck C. , Scherrer M. , Tesari I. , Kraft O.
Published: May 2003

Eine analytische Vorgehensweise zur Bauteiloptimierung wird vorgestellt, die ohne FEM‐Einsatz auskommt. Es ergeben sich deutliche Kerbspannungsreduktionen bei minimalem Aufwand.
Prescription and non‐prescription analgesic use among the US adult population: results from the third National Health and Nutrition Examination Survey (NHANES III)
Authors: Paulose‐Ram Ryne , Hirsch Rosemarie , Dillon Charles , Losonczy Katalin , Cooper Michael , Ostchega Yechiam
Published: May 2003

Purpose

To estimate prescription and non‐prescription analgesic use in a nationally representative sample of US adults.

Methods

Data collected during the third National Health and Nutrition Examination Survey (1988–1994), for persons 17 years and older were analyzed (n = 20 050). During the household interview, respondents reported use, in the last month, of prescription and non‐prescription analgesics.

Results

An estimated 147 million adults reported monthly analgesic use, Prescription analgesic use was 9% while non‐prescription use was 76%. Females were more likely than males to use prescription (11 vs. 7%, p < 0.001) and non‐prescription (81 vs. 71%, p < 0.001) analgesics. Across race–ethnicity groups, males (∼8%) and females (11–13%) had similar age‐adjusted prescription analgesic use. Non‐prescription analgesic use was higher among non‐Hispanic whites than non‐Hispanic blacks and Mexican–Americans for males (76 vs. 53% (p < 0.001) and 59% (p < 0.001), respectively) and females (85 vs. 68% (p < 0.001) and 71% (p < 0.001), respectively). With increasing age, prescription analgesic use increased whereas non‐prescription use decreased. Approximately 30% of adults used multiple analgesics during a 1‐month period. This was more common among females (35%) than males (25%, p < 0.001) and among younger (17–44 years, 33%) rather than older age groups (45+ years, 26%, p < 0.001).

Conclusions

Analgesic use among US adults is extremely high, specifically of non‐prescription analgesics. Given this, health care providers and consumers should be aware of potential adverse effects and monitor use closely. Published in 2002 by John Wiley & Sons, Ltd.
Trends in prescribing for heart failure in Dutch primary care from 1996 to 2000
Authors: Pont Lisa G. , Sturkenboom Miriam C. J. M. , van Gilst Wiek H. , Denig Petra , Haaijer‐Ruskamp Flora M.
Published: May 2003

Purpose

The aim of this study is to explore trends in primary care prescribing for chronic heart failure (CHF) over a 5‐year period (1996–2000).

Methods

This study consisted of repeated cross‐sectional surveys in a dynamic cohort from the Integrated Primary Care Information (IPCI) primary care database. The cohort comprised all patients aged ≥55 years with a CHF diagnosis and prescribed a cardiovascular medication during the study period. The point prevalence per calendar year was determined for each of the main drug groups used to treat CHF.

Results

The study population consisted of 3121 CHF patients. Small increases were seen in the percentage of CHF patients prescribed spironolactone (4.6%, 95% CI: 2.3–6.9%), β‐blockers (6.1%, 95% CI: 2.6–9.5%) and angiotensin II antagonists (6.8%, 95% CI: 5.1–8.6%) during the study period, while the prescribing of digoxin decreased (−4.4%, 95% CI: −8.2 to −0.7). Prescribing of diuretics (difference: −0.7% 95% CI: −2.7–4.2) and ACE inhibitors (difference: 4.0% 95% CI: −0.1–8.2%) remained unchanged.

Conclusions

Prescription of some drug groups for CHF increased. However, given the new scientific evidence that has emerged in past 15 years regarding CHF pharmacotherapy, the changes observed were less than expected. Copyright © 2003 John Wiley & Sons, Ltd.
Impact of cisapride label changes on codispensing of contraindicated medications
Authors: Guo Jeff Jianfei , Curkendall Suellen , Jones Judith K. , Fife Daniel , Goehring Earl , She Dewei
Published: May 2003

Objective

To quantify the impact of the first three label changes and ‘Dear Doctor’ letters as sole interventions, sent to prescribers and pharmacists, on the prescribing and dispensing of cisapride and contraindicated drugs.

Methods

Using a managed care claims database, a total of 38 757 patients with cisapride prescriptions (July 1993– December 1998) were selected. An interrupted time series analysis and an exponentially weighted moving average analysis (EWMA) were conducted to determine whether there were changes in the proportion of contraindicated codispensings following each intervention.

Results

3.6% of cisapride dispensings overlapped with contraindicated drug dispensings. Beginning in 1994, the overlapped proportions declined slowly from 4.5% ending at 3.2% in 1998. The interrupted time series analysis showed that there was a statistically significant abrupt permanent decrease in the proportion of contraindicated dispensing following the June 1998 label change (coefficient −1.0094, p = 0.045), meaning that the proportion of contraindicated dispensing dropped nearly one percentage point after the third intervention. The 1995 label changes did not have statistically significant effects. The EWMA analysis showed that the proportion of contraindicated dispensings was lower than 3 standard deviations below average during the period after the June 1998 intervention, with no significant effects following the two earlier interventions.

Conclusions

The June 1998 cisapride label change and accompanying ‘Dear Doctor’ letter had a downward impact on the proportion of dispensing of contraindicated drugs with cisapride. The other two label changes did not have independent significant impacts. Copyright © 2003 John Wiley & Sons, Ltd.
Liver function testing in patients on HMG‐CoA reductase inhibitors
Authors: Andrade Susan E. , Donahue James G. , Chan K. Arnold , Watson Douglas J. , Platt Richard
Published: May 2003

Purpose

The Food and Drug Administration currently requires the labeling of HMG‐CoA reductase inhibitors to recommend liver function tests (LFTs) before the start of therapy and at various intervals during therapy, depending on the specific agent. We sought to determine the frequency and patterns of LFT screening in patients receiving HMG‐CoA reductase inhibitors.

Methods

A retrospective study was conducted at a staff‐model health maintenance organization among 4178 new users of HMG‐CoA reductase inhibitors during the period 1 January 1991 through 31 December 1996. The number and proportions of HMG‐CoA reductase inhibitor therapy courses with baseline LFTs (within 180 days prior to dispensing), follow‐up LFTs and LFT abnormalities were calculated.

Results

For the initial HMG‐CoA reductase inhibitor dispensed, 1947 patients (47%) had at least one screening LFT at baseline and 3063 (73%) had at least one follow‐up LFT. Twenty‐seven (0.9%) patients with at least one follow‐up LFT performed had a level greater than 3 times the upper limit of normal. In a random sample of 100 discontinued patients, none discontinued due to elevated LFTs or liver disease.

Conclusions

A large proportion of patients dispensed HMG‐CoA reductase inhibitors in this managed care setting did not have baseline and follow‐up LFTs performed. Modest LFT abnormalities were common among users of HMG‐CoA reductase inhibitors; however, in this population, serious abnormalities were rare. Copyright © 2003 John Wiley & Sons, Ltd.
Biases affecting the proportional reporting ratio (PRR) in spontaneous reports pharmacovigilance databases: the example of sertindole
Authors: Moore Nicholas , Hall Gillian , Sturkenboom Miriam , Mann Ron , Lagnaoui Rajaa , Begaud Bernard
Published: May 2003

Background

Automated measures of reporting disproportionality in databases of spontaneous reports of adverse drug reactions are an emerging tool to identify drug‐related alerts. Sertindole, a new atypical neuroleptic known to prolong the QT interval, was suspended in November 1998 because the proportion of reports of fatal reactions suggesting arrhythmia among all reports with sertindole was almost ten times higher than that for other atypical neuroleptics in the UK. This excess risk was not predicted in preclinical data and had not been found in premarketing trials.

Method

Reporting patterns over time were analysed. Prescription Event Monitoring (PEM) studies and a large retrospective cohort allowed for the comparison of actual death rates with atypical neuroleptics, and to assess which proportion of the deaths that occurred were reported.

Results

There were indications of possible skewing of reporting related to notoriety, surveillance and market size effects. Death rates in PEM studies were essentially similar between sertindole and other neuroleptics. Cardiac deaths had been two to three times more often reported than other causes of death.

Conclusion

Proportional reporting ratios indicate differential reporting of possible reactions, not necessarily differential occurrence. There was no indication of an actual increase of risk of all causes or cardiac deaths during sertindole treatment, but only an increased risk of its being reported. The suspension of sertindole was rescinded by Committee on Proprietary Medicinal Products (CPMP) in October 2001. Copyright © 2003 John Wiley & Sons, Ltd.
Effect of colloidal self‐assemblies on the basic hydrolysis of 2‐(4‐bromophenoxy)quinoxaline
Authors: Cuenca Angela
Published: May 2003

In the presence of cationic surfactants (C16H33NR3Cl; R = Me, n‐Pr, n‐Bu), the shape of rate versus surfactant concentration profiles for the basic hydrolysis of 2‐(4‐bromophenoxy)quinoxaline depends on substrate concentration. At low substrate concentration there is a single rate maximum and with a 10‐fold substrate concentration increase a double rate maximum is observed. The first rate maximum is ascribed to reaction occurring in premicellar aggregates and the second to reaction in micelles. At low substrate concentration the effect of surfactant head group size was examined. Second‐order rate constants in the micellar pseudophase increase with increasing head group size. Copyright © 2003 John Wiley & Sons, Ltd.
Rate‐limiting step and micellar catalysis of the non‐classical nitro group nucleophilic substitution by thiols in 4‐nitro‐N‐n‐butyl‐1,8‐naphthalimide
Authors: Triboni E. R. , Politi M. J. , Cuccovia I. M. , Chaimovich H. , Berci Filho P.
Published: May 2003

Nitronaphthalimides are a particularly interesting group of nitroaromatics used for staining cells in hypoxia and in photodynamic therapy. The kinetics of the aromatic nucleophilic substitution of the nitro‐group of 4‐nitro‐N‐n‐butyl‐1,8‐naphthalimide (4‐NBN) by n‐heptanethiol (RSH), thiophenol (ArSH) and 2‐hydroxy‐1‐ethanethiol (HESH) in aqueous solutions containing micelles and in water–methanol mixtures were analyzed. The substitution of the nitro group by aromatic or aliphatic thiols led to fluorescent substitution products. Hexadecyltrimethylammonium chloride micelles (CTAC) increased the rate of thiolysis of 4‐NBN by 1 × 105 (RSH) and 4 × 105 (ArSH) fold. For the reaction of ArSH with 4‐NBN the calculated second‐order rate constant in the micellar phase, k2m, is 1.4 times higher than that in the aqueous phase, k2w. For the reaction of ArSH with 4‐NBN, k2m/k2w = 0.05. Both k2w and k2m decreased with increasing pKa of the thiol, suggesting that thiolate attack is not rate limiting in either the aqueous phase or micellar pseudophase. The high micellar rate acceleration is therefore largely due to concentration of the reagents in the micellar phase and effects on the thiol acid–base equilibrium. Copyright © 2003 John Wiley & Sons, Ltd.
Theoretical studies on empirical structure–reactivity relationship: the Yukawa–Tsuno equation
Authors: Nakata Kazuhide , Fujio Mizue , Nishimoto Kichisuke , Tsuno Yuho
Published: May 2003

The substituent‐dependent stabilization energies (δXΔE) of a series of α,α‐R1R2 benzyl cations were determined by means of ab initio calculation at the MP2/6–31G*//RHF/6–31G* + ZPE (scaled 0.8929) level, based on the isodesmic hydride transfer reactions between ring X‐substituted and unsubstituted R1R2 benzyl cations. Substituent stabilities (δXΔE) of α,α‐dimethylbenzyl cations were determined in the same way, to define a reference set of the ab initio σ+ values. The (δXΔE) of α,α‐dimethylbenzyl cations of which the cation center is set orthogonal to the benzene π‐system were correlated linearly with σ0 (solution). Based on this correlation, a set of ab initio σ0 constants [(σ0)
ab] was determined. The ab initio resonance substituent constants $(\Delta \overline{\sigma}_{\rm R}^{+})_{ab}$ were defined as (σ+)
ab − (σ0)
ab. Employing the present ab initio set of (σ0)
ab and $(\Delta \overline{\sigma}_{\rm R}^{+})_{ab}$ constants, the ab initio Yukawa–Tsuno (Y–T) equation was applied to 18 sets of cation stabilities δXΔE associated with hydride transfer reaction systems. Successful applications of the ab initio Y–T equation confirm the theoretical validity of the empirical Y–T relationship; in practice, the Y–T equation makes it possible to divide the electronic substituent effect into the non‐resonance and resonance contributions. Copyright © 2003 John Wiley & Sons, Ltd.
Selective acylation of a sterically hindered hydroxyl group of unsymmetrical diols containing a primary hydroxyl group such as 1,5‐hexanediol in the presence of silica gel with acetyl chloride
Authors: Ogawa Haruo , Ide Yuko , Honda Ryoichi , Chihara Teiji
Published: May 2003

The more hindered monoacetates were selectively formed in the presence of silica gel with acetyl chloride by refluxing a suspension of unsymmetrical diols containing a primary hydroxyl group such as 1,5‐hexanediol preadsorbed on silica gel. Such regioselectivity was observed through preferential adsorption via a primary hydroxyl group of the diols. Copyright © 2003 John Wiley & Sons, Ltd.
Prediction of tautomeric preferences and pKa values for oxyluciferin and its constituent heterocycles
Authors: Dahlke Erin E. , Cramer Christopher J.
Published: May 2003

Well converged electronic structure calculations are employed to predict the relative energies of tautomers of thiazol‐5(4H)‐one/5‐hydroxythiazole. Benchmarks established for this system are then employed to correct less complete levels of theory applied to the prediction of relative tautomer energies in substituted cases, including oxyluciferin. In the gas phase and aqueous solution, weak preferences for hydroxy and keto tautomers, respectively, are generally observed, but the magnitude is such that mixtures containing significant quantities of minor tautomers are predicted in most instances. The first pKa value for oxyluciferin is predicted to be 6.5, with phenolate tautomers dominating the anionic equilibrium. Copyright © 2003 John Wiley & Sons, Ltd.
Computational study of maleamic acid cyclodehydration
Authors: Ivanov Daniela , Constantinescu Mircea
Published: May 2003

The mechanism of cyclodehydration of alkyl (Bu) and aryl (Ph) substituted maleamic acids to the corresponding maleimides and isomaleimides using N,N′‐dicyclohexylcarbodiimide as dehydration agent in CH2Cl2 as the solvent was investigated by PM3/AMSOL semiempirical calculations. An addition intermediate between the dehydrating agent and the maleamic acid carboxyl group was considered to be formed at the very beginning of the reaction. Two mechanisms reported in the literature were considered, one involving initial formation of a cyclic anion intermediate and the other proposing an acyclic amide anion. Our computational results supported the latter mechanism and a new reaction step was proposed that could also explain the ratio between the maleimide and isomaleimide formation depending on the amide substituent (alkyl or aryl type). The computational data are in good agreement with reported experimental results. Copyright © 2003 John Wiley & Sons, Ltd.
Enhanced gauge symmetry from ‘toric’ G2 cones
Authors: Anguelova L. , Lazaroiu C.I.
Published: May 2003

We discuss the construction of M‐theory compactifications on ‘toric’ G2 cones, a class of models which generalize those recently considered by Acharya and Witten. We explain our criteria for identifying the gauge group content of such theories and briefly discuss the associated metrics.
Time asymmetric quantum theory – I. Modifying an axiom of quantum physics
Authors: Bohm A.R. , Loewe M. , Van de Ven B.
Published: May 2003

A slight modification of one axiom of quantum theory changes a reversible theory into a time asymmetric theory. Whereas the standard Hilbert space axiom does not distinguish mathematically between the space of states (in‐states of scattering theory) and the space of observables (out‐“states” of scattering theory) the new axiom associates states and observables to two different Hardy subspaces which are dense in the same Hilbert space and analytic in the lower and upper complex energy plane, respectively. As a consequence of this new axiom the dynamical equations (Schrödinger or Heisenberg) integrate to a semigroup evolution. Extending this new Hardy space axiom to a relativistic theory provides a relativistic theory of resonance scattering and decay with Born probablilities that fulfill Einstein causality and the exponential decay law.
Time asymmetric quantum theory – II. Relativistic resonances from S‐matrix poles
Authors: Bohm A. , Kaldass H. , Wickramasekara S.
Published: May 2003

Relativistic resonances and decaying states are described by representations of Poincaré transformations, similar to Wigner's definition of stable particles. To associate decaying state vectors to resonance poles of the S‐matrix, the conventional Hilbert space assumption (or asymptotic completeness) is replaced by a new hypothesis that associates different dense Hardy subspaces to the in‐ and out‐scattering states. Then one can separate the scattering amplitude into a background amplitude and one or several “relativistic Breit‐Wigner” amplitudes, which represent the resonances per se. These Breit‐Wigner amplitudes have a precisely defined lineshape and are associated to exponentially decaying Gamow vectors which furnish the irreducible representation spaces of causal Poincaré transformations into the forward light cone.
Time asymmetric quantum theory – III. Decaying states and the causal Poincaré semigroup
Authors: Bohm A. , Kaldass H. , Wickramasekara S.
Published: May 2003

These Gamow kets span an irreducible representation space for Poincaré transformations which, similar to the Wigner representations for stable particles, are characterized by spin (angular momentum of the partial wave amplitude) and complex mass (position of the resonance pole). The Poincaré transformations of the Gamow kets, as well as of the Lippmann‐Schwinger plane wave scattering states, form only a semigroup of Poincaré transformations into the forward light cone. Their transformation properties are derived. From these one obtains an unambiguous definition of resonance mass and width for relativistic resonances. The physical interpretation of these transformations for the Born probabilities and the problem of causality in relativistic quantum physics is discussed.