Friction of Teflon-S-coated Ti-6Al-4V under conditions of oscillatory relative motion

An extendable prosthesis for implantation in a human leg has been developed. The friction forces during extension of the prosthesis must be low, so a coating of Teflon-S was applied to the sliding surfaces. During walking, damage can occur as a result of oscillatory relative motion. Therefore experiments were performed with an apparatus which simulated this type of motion. It was found that the coefficient of friction reached a maximum value within one million movement cycles. This maximum value of the coefficient of friction increased with decreasing coating thickness. Even at an initial coating thickness of less than 1 μm, coating with Teflon-S was found to be very effective in reducing friction

Including copy number variation in association studies to predict genotypic values

The objective of this study was to investigate, both empirically and deterministically, the ability to explain genetic variation resulting from a copy number polymorphism (CNP) by including the CNP, either by its genotype or by a continuous derivation thereof, alone or together with a nearby single nucleotide polymorphism (SNP) in the model. This continuous measure of a CNP genotype could be a raw hybridization measurement, or a predicted CNP genotype. Results from simulations showed that the linkage disequilibrium (LD) between an SNP and CNP was lower than LD between two SNPs, due to the higher mutation rate at the CNP loci. The model R2 values from analysing the simulated data were very similar to the R2 values predicted with the deterministic formulae. Under the assumption that x copies at a CNP locus lead to the effect of x times the effect of 1 copy, including a continuous measure of a CNP locus in the model together with the genotype of a nearby SNP increased power to explain variation at the CNP locus, even when the continuous measure explained only 15% of the variation at the CNP locus

Hydrodynamic modelling of hydrostatic magnesium extrusion

Wilson’s hydrodynamic model of the hydrostatic extrusion process is extended to meet the geometry found on residual billets. The transition from inlet\ud to work zone of the process is not considered sharp as in the model of Wilson but as a rounded edge, modelled by a parabolic function. It is shown that\ud this rounded edge has a considerable influence on the predicted film thickness. Furthermore, it is shown that for hydrostatic extrusion of magnesium with castor oil as pressure medium, it is not possible to generate full film lubrication in the work zone of the hydrostatic extrusion process

Preparation and properties of a composite charged membrane

In order to develop a low pressure desalination membrane with fixed ionic charges, we made use of the normally unwanted crosslinking tendency in preparing the polyelectrolyte poly(styrenesulfonate) by sulfonation of polystyrene. After dipcoating a poly(sulfone) or poly(phenylene oxide) UF membrane with a dilute soluton of this polyelectrolyte in water in the presence of some free sulfuric acid and silversulfate, fixation and cross-linking of the coating polymer took place by a heat treatment.\ud \ud Different membrane properties could be obtained by varying the pore size of the supporting UF membranes, and by variation in the coating polymer (M.W., concentration) and sulfuric acid concentration. We found that fluxes sometimes decline drastically in comparison with the original pure water flux; salt rejection values (at 1.5 g/l NaCl concentration and 0.5 MPa) never are very high (≤60% for monovalent anions). The most important potential application for these membranes lies in their non-fouling properties

Temporal changes in carboxylate content of ryegrass with stepwise change in nutrition

A detailed scheme of carboxylate formation and retention by plant tissues as a result of ion uptake and utilization is given. By means of discontinuities in the supply with nutrient ions, carboxylate retention by the tissues of perennial ryegrass was followed as a function of growth. It was found that translocation of potassium nitrate to the shoot and subsequent nitrate metabolism was the only process capable of supplying the shoot with sufficient carboxylates and of removing the excess from the foliage to the root system with maintenance of the normal carboxylate content. Absorbed bicarbonate was a good source of carboxylates in the roots, but the rate of translocation to the plant tops was too slow relative to growth. Therefore, the carboxylate concentration in the foliage fell progressively to one half the normal value. Constancy of carboxylate concentration in the dry matter was related to the early establishment of the proportion of carboxylates to dry material in the new growth, making it independent of subsequent changes in water content of the tissues. Changes in carboxylate concentrations due to changes in the supply were continuous with time. Nitrate caused a depression in the roots during nitrate accumulation, but the nitrate metabolism in the follage made sufficient carboxylates available for replenishment and maintenance of their normal level in the whole plant

Optical anisotropy of Ge(001)

The surface induced optical anisotropy in the electronic structure of clean Ge(001) 2×1 was studied with an ellipsometer at normal incidence. The change in the reflection difference between light polarized parallel and perpendicular to the dimer bond at this surface upon either absorption of molecular oxygen or Ar+ ion bombardment was recorded. Both procedures were found to give the same results. It was possible to obtain a qualitative agreement of the optical spectrum recorded and the position and parity of the occupied and unoccupied surface states known on the clean surface