Friction and Wear Properties of Metal/Metal Hip Joints

Insufficient understanding of tribological behaviour of total joint components is considered as one of the major reasons for premature prosthesis failure. In the previous years, wear modes and mechanisms of artificial hips have been intensively studied using testing machines applying continuous motion and load profiles. Human locomotion, however, is of erratic shape containing motion interruptions among other irregularities. These occurring resting phases could influence adhesive friction at the artificial articulation with possible effects on wear and loosening. Initial frictional behaviour after resting periods and subsequent wear of metal‐on‐metal hip components have been investigated. While the initial frictional moment of artificial hip components was found to increase significantly with increasing resting duration, wear was hardly affected. These results therefore rather point to an interlocking phenomenon than adhesion. Still, the results are of concern because the increase in friction is likely to occur under physiological conditions too and may cause tangential stress peaks at the bone/ implant interface accelerating fatigue failure. In particular, big head sizes should be used with caution because the frictional moment is a function of coefficient of friction and ball diameter.     

A Review on the Effects of Supercritical Carbon Dioxide on Enzyme Activity

Different types of enzymes such as lipases, several phosphatases, dehydrogenases, oxidases, amylases and others are well suited for the reactions in SC-CO₂. The stability and the activity of enzymes exposed to carbon dioxide under high pressure depend on enzyme species, water content in the solution and on the pressure and temperature of the reaction system. The three-dimensional structure of enzymes may be significantly altered under extreme conditions, causing their denaturation and consequent loss of activity. If the conditions are less adverse, the protein structure may be largely retained. Minor structural changes may induce an alternative active protein state with altered enzyme activity, specificity and stability.     

Hot topic: Bovine milk samples yielding negative or nonspecific results in bacterial culturing--the possible role of PCR-single strand conformation polymorphism in mastitis diagnosis

A large proportion of mastitis milk samples yield negative or nonspecific results (i.e., no mastitis pathogen can be identified) in bacterial culturing. Therefore, the culture-independent PCR-single strand conformation polymorphism method was applied to the investigation of bovine mastitis milk samples. In addition to the known mastitis pathogens, the method was suitable for the detection of fastidious bacteria such as Mycoplasma spp., which are often missed by conventional culturing methods. The detection of Helcococcus ovis in 4 samples might indicate an involvement of this species in pathogenesis of bovine mastitis. In conclusion, PCR-single-strand conformation polymorphism is a promising tool for gaining new insights into the bacteriological etiology of mastitis.     

Computational and experimental investigation of delamination in L-shaped laminated composite components

Formation of initial delaminations and growth of existing delaminations in L-shaped laminates made of plies of a unidirectional carbon fiber reinforced epoxy resin is investigated computationally and experimentally. For this purpose an experimental test is designed which allows to realize load states for which delamination is the dominant failure mechanism. Two types of test specimens, with and without initial delaminations, are investigated and good agreement is obtained between the computational predictions and the experimental results concerning delamination emergence, delamination growth, growth stability, the structural response, and the maximum principal strains.     

Erweiterung des Stadions Innsbruck “Tivoli Neu” für die Fußballeuropameisterschaft 2008

Stadium Innsbruck “Tivoli Neu” extended for the European Football Championship 2008. Austria and Switzerland are the hosts of the European Football Championship EURO 2008. Each of both countries needs four stadiums with at least 30000 spectator seats. Innsbruck had a facility with a capacity of nearly 15000 seats. This existing stadium “Tivoli Neu” has therefore to be extended. The community of Innsbruck requests, that after the Championship the stadium has to be reconstructed into the original state.     

Raumplanungskompetenzen in Angelegenheiten der Grundversorgung von Asylwerbern

Bisher wurde in Lehre und Rechtsprechung nur fragmentarisch er?rtert, wie Raumplanungskompetenzen in Bezug auf die Schaffung und Erhaltung einer Infrastruktur zur Versorgung und Betreuung hilfsbedürftiger Asylwerber von der Bundesverfassung verteilt werden. Die schwierige Standortfindung für die (im Regierungsprogramm zur XXIV. Gesetzgebungsperiode vorgesehene) "Erstaufnahmestelle-Süd" hat gezeigt, dass diese Frage nicht nur von hoher praktischer Relevanz ist, sondern auch politische Brisanz aufweist. Im vorliegenden Beitrag wird versucht, die einschl?gigen Gesetzgebungskompetenzen von Bund und L?ndern voneinander abzugrenzen sowie, auf Ebene der Vollziehung, das Verh?ltnis von ?rtlicher und über?rtlicher Raumplanung betreffend Asyl-Erstaufnahmestellen zu kl?ren.     

Woolrock—a material for technical use consisting of keratin

This article debates the production of mouldings made of keratin. It is demonstrated that the properties of keratin allow for being processed with heat and pressure to manufacture tough mouldings without chemical preprocessing of the used wool. This material thus has a high potential as a bioplastic, because it potentially can be used with conventional plastic manufacturing techniques. Additionally, it might also serve as an adhesive in various applications. The biobased material might become a sustainable source for mouldings.

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Computational materials design: A perspective for atomistic approaches

Summary Present theoretical and computational approaches, combined with the impressive advances in computer hardware and software, open the possibility for materials design from first principles. This article presents a perspective on the relevant developments in computational chemistry, solid state physics and statistical mechanics and it assesses the merits and limitations of Hartree-Fock, density functional, semiempirical and force field approaches in terms of six criteria: capability, generality, accuracy, accessible system size, accessible time scales and computational efficiency. Functional materials for microelectronic, optical and magnetic applications currently present better opportunities for first-principles approaches than structural materials, where atomistic approaches, despite some encouraging results, are still far from capturing the full complexity of the dynamics involved in mechanical, thermal, diffusive and corrosive behavior.