Microstructural characterisation of a nickel alloy processed via blown powder direct laser deposition (DLD)

A three dimensional structure of varying wall thickness has been manufactured from an alloy similar to 718 and subjected to metallographic characterisation. The technique is evaluated as a process capable of generating complex geometries. This can be used to add features or as a free form fabrication method. However, in order to allow for comparison to structures developed through more traditional techniques, detailed microstructural characterisation has been undertaken to attempt to understand the potential effect of variation on resultant mechanical properties.Samples were extracted from six locations with different wall thicknesses, intricate features and intersecting ligament geometry. A γ″ linearly arrayed structure within a γ matrix was consistent throughout the component. Micro-porosity was restricted to isolated, spherical pores < 1 μm in diameter. Electron back-scatter diffraction and X-ray computed microtomography quantitative microstructural analysis techniques have been utilized to assess the influence of layering upon microporosity, patternation and grain structure.A detailed comparison is also made between blown powder Direct Layer Deposition (DLD) and a similar deposition technique, shaped metal deposition (SMD). Blown powder DLD produces a smaller weld pool and results in a more consistent microstructure than SMD, with less evidence of unfavourable phases brought about by prolonged exposure to high temperatures. The improved microstructure, however, must be measured against the different process economics of the blown powder DLD technique

Metabolic investigation of host/pathogen interaction using MS2-infected Escherichia coli

<p>Abstract</p> <p>Background</p> <p>RNA viruses are responsible for a variety of illnesses among people, including but not limited to the common cold, the flu, HIV, and ebola. Developing new drugs and new strategies for treating diseases caused by these viruses can be an expensive and time-consuming process. Mathematical modeling may be used to elucidate host-pathogen interactions and highlight potential targets for drug development, as well providing the basis for optimizing patient treatment strategies. The purpose of this work was to determine whether a genome-scale modeling approach could be used to understand how metabolism is impacted by the host-pathogen interaction during a viral infection. <it>Escherichia coli</it>/MS2 was used as the host-pathogen model system as MS2 is easy to work with, harmless to humans, but shares many features with eukaryotic viruses. In addition, the genome-scale metabolic model of <it>E. coli </it>is the most comprehensive model at this time.</p> <p>Results</p> <p>Employing a metabolic modeling strategy known as "flux balance analysis" coupled with experimental studies, we were able to predict how viral infection would alter bacterial metabolism. Based on our simulations, we predicted that cell growth and biosynthesis of the cell wall would be halted. Furthermore, we predicted a substantial increase in metabolic activity of the pentose phosphate pathway as a means to enhance viral biosynthesis, while a break down in the citric acid cycle was predicted. Also, no changes were predicted in the glycolytic pathway.</p> <p>Conclusions</p> <p>Through our approach, we have developed a technique of modeling virus-infected host metabolism and have investigated the metabolic effects of viral infection. These studies may provide insight into how to design better drugs. They also illustrate the potential of extending such metabolic analysis to higher order organisms, including humans.</p

Efficient homologous prime-boost strategies for T cell vaccination based on virus-like particles

Induction of high frequencies of specific T cells by vaccination requires prime-boost regimens. To reach optimal immune responses, it is necessary to use different vectors for priming and boosting as e.g. DNA vaccination followed by boosting with a recombinant viral vector. Here, we show that vaccines based on virus-like particles (VLP) displaying peptide epitopes are equally effective to induce CTL responses if used in a homologous or heterologous prime-boost setting. Strikingly, high frequencies (&gt;20% of CD8(+) cells) of protective CTL could be induced and maintained by weekly injection of VLP. Thus, the use of VLP may avoid the requirement for complicated heterologous prime-boost regimens, facilitating the development of effective T cell-based vaccines