Effect of the design parameters on the in vitro wear performance of total shoulder arthroplasties

The loosening of the glenoid component is the main reason for the failure of a total shoulder arthoplasty. It may be caused either by high tensile stresses or by osteolysis of the surrounding bone in response to the presence of particle debris. This failure might be associated with the wear of the implant as occurs with replacement hip and knee joints.The paper reports the findings of a study of the in vitro performance of the currently used total shoulder prostheses to determine the effects of implant geometry on the wear of the polyethylene components and the friction conditions operating within the shoulder prosthesis.The wear performance of the implants was evaluated using a self-developed tribotester, simulating the physiological conditions of a shoulder joint. This study revealed that significantly different wear occurred with conforming and non-conforming articulation and revealed the influence of the thickness of the polyethylene glenoid on the wear and friction occurring in the joint. In this preliminary study significant wear of the polyethylene glenoid component occurred, estimated to be up to 19 mm³/year, which is similar to that found in retrieved implants. The conforming implants demonstrated significantly greater wear than the non-conforming implants (p < 0.05). A significantly lower friction factor, about 0.05 ± 0.01 (p < 0.05), was obtained for the less conforming implants.     

Monolithic ZnTe-based pillar microcavities containing CdTe quantum dots

Micropillars of different diameters have been prepared by focused ion beam milling out of a planar ZnTe-based cavity. The monolithic epitaxial structure, deposited on a GaAs substrate, contains CdTe quantum dots embedded in a ZnTe λ-cavity delimited by two distributed Bragg reflectors (DBRs). The high refractive index material of the DBR structure is ZnTe, while for the low index material a short-period triple MgTe/ZnTe/MgSe superlattice is used. The CdTe quantum dots are formed by a novel Zn-induced formation process and are investigated by scanning transmission electron microscopy. Micro-photoluminescence measurements show discrete optical modes for the pillars, in good agreement with calculations based on a vectorial transfer matrix method. The measured quality factor reaches a value of 3100.     

Ortho‐ vs Bay‐Functionalization: A Comparative Study on Tetracyano‐Terrylenediimides

In this paper n‐type semiconductors synthesized via selective fourfold cyanation of the ortho‐ and bay‐positions (2,5,10,13‐ and 1,6,9,14‐positions respectively) of teyrrylenediimides are reported. A detailed study about the impact of the diverse functionalization topologies on the optoelectronic properties, self‐organization from solution, solid‐state packing, and charge carrier transport in field‐effect transistors is presented. The ortho‐substitution preserves the planarity of the core and favors high order in solution processed films. However, the strong intermolecular interactions lead to a microstructure with large aggregates and pronounced grain boundaries which lower the charge carrier transport in transistors. In contrast, the well‐soluble bay‐functionalized terrylenediimide forms only disordered films which surprisingly result in n‐type average mobilities of 0.17 cm²/Vs after drop‐casting with similar values in air. Processing by solvent vapor diffusion enhances the transport to 0.65 cm²/Vs by slight improvement of the order and surface arrangement of the molecules. This mobility is comparable to highest n‐type conductivities measured for solution processed PDI derivatives demonstrating the high potential of TDI‐based semiconductors.     

Werner-type metal complexes of potato starch

It was shown that potato starch formed Werner‐type complexes. In these complexes a metal atom is ligated by the lone electron pairs of hydroxyl groups from d ‐glucose units and phosphate groups in starch. Acetate, chloride and nitrate were counter‐ions to the transition metal atoms. The metal cations bound preferentially to the phosphoric acid moiety of amylopectin, but secondarily they were co‐ordinated by the hydroxyl groups of the d ‐glucose units. This resulted in the formation of clathrate cages in which a significant number of the water molecules were trapped. Such structures were able to co‐ordinate further metal cations. Only Mn(II) and Co(II) ions, with acetate counter‐ions, neither formed clathrate cages nor were co‐ordinated by the hydroxyl groups of the d ‐glucose of starch.     

Studies of oxygen uptake on O2 scavengers ­prepared from different iron‐containing ­parent substances

Temperature‐programmed reduction (TPR) measurements were performed for iron oxalates, iron(III) hydroxide (both pure and with additives) and iron(II, III) oxide. On the ground of TPR curves, reduction temperatures of the iron‐containing parent substances were chosen followed by oxygen uptake determination. Comparison of oxygen uptakes points to the use of Fe(OH)₃ and Fe₃O₄ as more advantageous than that of iron oxalates. Co‐precipitation from a mixed solution of iron and manganese salts results in a product which is more resistant to particle agglomeration at elevated temperatures than that obtained by­precipitation from solution of iron salt alone. Copyright © 2002 John­Wiley & Sons, Ltd.     

Integrated instrumental analysis of soft brown coals

A method for the simultaneous determination of calorific value Q^r, ash yieldA^r and total water content W^r_t of soft brown coals is described. The method involves instrumental analysis of brown coal samples using neutron thermalization and gamma back-scattering techniques. Over 80 coal samples (1.1 kg) were analysed, having Q^rvalues up to 15.5 MJ kg^?1,A^r ranging from 3.6 to 76.1 wt% and W^r_t ranging from 11.4 to 61.7 wt%. A comparison of the results from the instrumental method with those of standard laboratory analyses is given, followed by a discussion of the accuracy of the method and of possible ways for improving it.     

Study of the thermal stability of phases in the Mg-Al system

A part of the Al-Mg phase diagram was studied in the range of composition between 48 and 61 at.% Al by DSC and SEM/EDS methods. The temperature ranges of stability of the β, γ, and ɛ phases were considered. It was found that the congruent melting temperature of the β phase was 450±1 °C. The Al content in that phase was determined to be 61±1 at.% Al at 420 °C. The upper temperature limit of the stability of the ɛ phase was established to be 427±1 °C. The Al content changed from 54 at.% at 390 °C to 56 at.% at 420 °C. The lower temperature limit of the ɛ phase formation was not determined, as a result of a slow ɛ=β+γ reaction. The hypothetical λ or ζ phases were not found, but it was observed that decomposition of oxides might produce extra thermal effects.     

Determination of the ash yield and the mineral matter content of brown coals by density measurements

A method of measuring the density of bed-moist brown coals based on their plastic properties is described and the feasibility of using the method for determination of the ash yield of the coal is evaluated.     

Finite rotations in the description of continuum deformation

Finite rotations in continuum mechanics are described by means of either a proper orthogonal tensor or finite rotation vectors. Some algebraic relations concerning the finite rotations are reviewed. Formulae expressing them in terms of displacements are given. Along each of the curvilinear coordinate lines the finite rotations are shown to satisfy some systems of the linear first-order differential equations. Each system of the equations is presented in four different but equivalent forms associated with an intermediate stretched basis or with an intermediate rotated basis. Integrability conditions of the system of equations provide various alternative forms of compatibility conditions in continuum mechanics. The displacement field is expressed through the stretch and rotation fields in the form of three successive line integrals. The formula describes the displacements to within a constant finite translation and a constant finite rotation. The procedure proposed here generalizes the formula derived by Cesàro (1906) within the classical linear theory of elasticity.