Tribological assessment of a flexible carbon-fibre-reinforced poly(ether-ether-ketone) acetabular cup articulating against an alumina femoral head

New material combinations have been introduced as the bearing surfaces of hip prostheses in an attempt to prolong their life by overcoming the problems of failure due to wear-particle-induced osteolysis. This will hopefully reduce the need for revision surgery. The study detailed here used a hip simulator to assess the volumetric wear rates of large-diameter carbon-fibre-reinforced pitch-based poly(ether-ether-ketone) (CFR-PEEK) acetabular cups articulating against alumina femoral heads. The joints were tested for 25 x 10(6) cycles. Friction tests were also performed on these joints to determine the lubrication regime under which they operate. The average volumetric wear rate of the CFR-PEEK acetabular component of 54 mm diameter was 1.16 mm(3)/10(6) cycles, compared with 38.6 mm(3)/10(6) cycles for an ultra-high-molecular-weight polyethylene acetabular component of 28 mm diameter worn against a ceramic head. This extremely low wear rate was sustained over 25 x 10(6) cycles (the equivalent of up to approximately 25 years in vivo). The frictional studies showed that the joints worked under the mixed-boundary lubrication regime. The low wear produced by these joints showed that this novel joint couple offers low wear rates and therefore may be an alternative material choice for the reduction of osteolysis.     

Experimental verification of intelligent fault detection in rotor blades

The common idea of examining damage in mechanical structures through vibrational methods is analysed from a practical point of view. The method presented is based on a straightforward time domain approach and utilizes response signals in their purest form. Error magnification related to computational manipulations, e.g. FFT, or similar procedures, is avoided. The fact that the proposed method is straightforward and involves a minimum of signal processing, renders the approach attractive for use in practice, as an intelligent fault detection system. The method was applied to a clamped section of a helicopter rotor blade. Damage was induced by a mass increase (locally added weight) and a mass reduction (holes drilled into the structure), respectively. The experiments show that minimal effects on fundamental eigenfrequencies are reliably detectable without any a priori knowledge of the structure. A series of measurements with damage locations changed successively demonstrates nicely the effects on natural frequencies. In obtaining this result it became apparent that every case study exhibited its own individual vibrational signature which is very desirable in a health-monitoring environment.     

Electrochemical behaviour of manganese in the aluminium electrorefining bath

The study of the mechanism of the electrode reaction Mn(II)/Mn in the aluminium electrorefining bath free of aluminium fluoride (1·48 NaF-1·05 BaCl₂) has been carried out by chronopotentiometry with an inert graphite electrode, a manganese electrode and a platinum electrode; this study was supplemented by utilizing anodic chronopotentiometry with current reversal from a stationary state. The tests carried out at 800° C show that the exchange mechanism of Mn(II)/Mn is reversible, involves the exchange of two electrons and that the diffusion coefficient D_Mn(II)=(1·9±0·5)×10^–5 cm² s^–1.     

Attribute Aggregation in Federated Identity Management

Most federated identity management systems are limited by users' ability to choose only one identity provider per service session. A proposed linking service lets users securely link their various identity provider (IdP) accounts, enabling the system to aggregate attributes from multiple authoritative sources automatically without requiring users to authenticate separately to each IdP.     

Synthesis and biological properties of novel pyridinioalkanoyl thiolesters (PATE) as anti-HIV-1 agents that target the viral nucleocapsid protein zinc fingers

Nucleocapsid p7 protein (NCp7) zinc finger domains of the human immunodeficiency virus type 1 (HIV-1) are being developed as antiviral targets due to their key roles in viral replication and their mutationally nonpermissive nature. On the basis of our experience with symmetrical disulfide benzamides (DIBAs; Rice et al. Science 1995, 270, 1194-1197), we synthesized and evaluated variants of these dimers, including sets of 4,4'- and 3,3'-disubstituted diphenyl sulfones and their monomeric benzisothiazolone derivatives (BITA). BITAs generally exhibited diminished antiviral potency when compared to their disulfide precursors. Novel, monomeric structures were created by linking haloalkanoyl groups to the benzamide ring through -NH-C(=O)- (amide) or -S-C(=O)- (thiolester) bridges. Amide-linked compounds generally lacked antiviral activity, while haloalkanoyl thiolesters and non-halogen-bearing analogues frequently exhibited acceptable antiviral potency, thus establishing thiolester benzamides per se as a new anti-HIV chemotype. Pyridinioalkanoyl thiolesters (PATEs) exhibited superior anti-HIV-1 activity with minimal cellular toxicity and appreciable water solubility. PATEs were shown to preferentially target the NCp7 Zn finger when tested against other molecular targets, thus identifying thiolester benzamides, and PATEs in particular, as novel NCp7 Zn finger inhibitors for in vivo studies.     

An electroanalytical study of the composition of molten sodium metaphosphate

Phosphate glasses are known to be mixtures of chain phosphates. The presence of the lower polymers has been confirmed by electrochemical techniques and the proportions of the orthophosphate monomer in sodium metaphosphate melts have been estimated at temperatures between 660–810°C. The orthophosphate had not been detected in phosphate glasses using paper chromatography, but it is considered that quenching tends to increase polymerization and thus causes loss of the monomer.