Tribo-corrosion properties of cobalt-based medical implant alloys in simulated biological environments

Tribological problems and corrosion degradation have been recognized as essential risks for total joint replacements, especially for all-metal arthroplasty. Few studies have focused on the interactions between tribology and corrosion (tribocorrosion) for implant materials. This paper addresses the importance of understanding tribocorrosion and the evaluation of such materials in simulated biological environments. Due to the complex effect of proteins on tribocorrosion, which has been demonstrated in previous studies, this study focuses towards understanding the effects of amino acids as aspects of material degradation. Dulbecco’s Modified Eagle’s Medium (DMEM) is a cell culture solution. It contains comparable amount and types of amino acids to normal synovial fluid in human joints. 0.36% NaCl solution was employed to isolate the biological species. Three materials were tested; High carbon (HC) CoCrMo (contains 0.19% carbon), low carbon (LC) CoCrMo (widely used materials for total joint replacement) and stainless steel UNS S31603 (316L). Integrated electrochemical tests supported by measurement of friction and near surface chemical analysis were carried out to enable their tribocorrosion behaviour to be fully characterized. As a general conclusion, amino acids were found to react with materials under tribological contacts and form complex organometallic/oxides which lubricate the metallic sample surface. Tribocorrosion plays a very important role in material degradation in the studied environments. HC CoCrMo shows superior wear, corrosion and tribocorrosion resistance – the material characteristics and their effect on the different tribocorrosion processes are discussed

Conversion of acetate to lipids and co2 by liver of rats exposed to acceleration stress

Acetate conversion to lipids and carbon dioxide by exposure of rat liver to acceleration stres

Computer system for monitoring radiorepirometry data

System monitors expired breath patterns simultaneously from four small animals after they have been injected with carbon-14 substrates. It has revealed significant quantitative differences in oxidation patterns of glucose following such mild treatments of rats as a change in diet or environment

Providing adhesion for a miniture mobile intra-abdominal device based on biomimetic principles

This paper investigates the surface adhesion characteristics required for a miniature mobile device to move around the abdominal cavity. Such a device must be capable of adhering to the tissue lining and move freely across the upper surface of the insufflated abdomen. Accordingly, the potential of utilising bioinspired solutions to facilitate wet adhesion is assessed

Plane waves in quantum gravity: breakdown of the classical spacetime

Starting with the Hamiltonian formulation for spacetimes with two commuting spacelike Killing vectors, we construct a midisuperspace model for linearly polarized plane waves in vacuum gravity. This model has no constraints and its degrees of freedom can be interpreted as an infinite and continuous set of annihilation and creation like variables. We also consider a simplified version of the model, in which the number of modes is restricted to a discrete set. In both cases, the quantization is achieved by introducing a Fock representation. We find regularized operators to represent the metric and discuss whether the coherent states of the quantum theory are peaked around classical spacetimes. It is shown that, although the expectation value of the metric on Killing orbits coincides with a classical solution, its relative fluctuations become significant when one approaches a region where null geodesics are focused. In that region, the spacetimes described by coherent states fail to admit an approximate classical description. This result applies as well to the vacuum of the theory.Comment: 11 pages, no figures, version accepted for publication in Phys. Rev.

Detailed error analysis for a fractional Adams method

This is a PDF version of a preprint submitted to Springer. The definitive version was published in the Numerical algorithms. The original publication is available at www.springerlink.comThis preprint discusses a method for a numerical solution of a nonlinear fractional differential equation, which can be seen as a generalisation of the Adams–Bashforth–Moulton scheme

The screen representation of vector coupling coefficients or Wigner 3j symbols: exact computation and illustration of the asymptotic behavior

The Wigner $3j$ symbols of the quantum angular momentum theory are related to the vector coupling or Clebsch-Gordan coefficients and to the Hahn and dual Hahn polynomials of the discrete orthogonal hyperspherical family, of use in discretization approximations. We point out the important role of the Regge symmetries for defining the screen where images of the coefficients are projected, and for discussing their asymptotic properties and semiclassical behavior. Recursion relationships are formulated as eigenvalue equations, and exploited both for computational purposes and for physical interpretations.Comment: 14 pages, 8 figures, presented at ICCSA 2014, 14th International Conference on Computational Science and Application

Deploying SiC BJTs in an 800-V switched-mode power supply for hybrid & electric vehicles

An SMPS for hybrid electric vehicle and electric vehicle applications is presented. The use of SiC BJTs in the primary-side switching circuitry is investigated. Practical deployment aspects are addressed. Particular attention is given to the design of the BJT base driver stage and a bespoke turn-on switching-aid circuit. Mathematical design calculations are not presented, but the proposed circuitry is demonstrated in a 1-kW isolated-output DC-DC converter operating from 800 V and supplying 48 V at a switching frequency of 60 kHz. Full-load efficiency was evaluated at 93.3% using a calorimeter

Projective Invariance and One-Loop Effective Action in Affine-Metric Gravity Interacting with Scalar Field

We investigate the influence of the projective invariance on the renormalization properties of the theory. One-loop counterterms are calculated in the most general case of interaction of gravity with scalar field.Comment: 10 pages, LATE