Microeconomics of the materials and energents consumption in a simulated copper casting process

An analytical model for the optimization of the consumption of materials and energents in a typical coppercasting process based on a standard simulation procedure is presented. The proposed microeconomic analysisin correlation with the virtual manufacture of castings enabled a shortening of the time required to developa product, as well as the fabrication of high quality castings, which could be a crucial contributionto the achievement of increased engineering adequacy and economic competitiveness.In this sense, the article demonstrates the beneficial employment of mathematical programming withina systematic economic analysis. The analyzed casting process is a part of the metallurgical manufacturingoperations of the Copper Smelter and Refinery Bor, Serbia

Synthesis of ZrO2 Particles Reinforced ZA25 Alloy Composites by Compocasting Process

Microstructures and compressive properties of Zn25Al3Cu/ZrO2 particulate composites were studied. The composites were obtained by compocasting process through infiltration of 1 and 3 wt% ZrO2 particles of different size into the semi-solid melt of the base alloy. The influence of reinforcing particles size and quantity on microstructure and mechanical properties of the composites was examined. The composites have shown significant improvement of mechanical properties with respect to the base alloy. Increase in hardness and compressive yield strength of the composites was more expressed in the composites with coarse ZrO2 particles. (C) Koninklijke Brill NV, Leiden, 201

An in vitro biofilm model of Staphylococcus aureus infection of bone

Chronic osteomyelitis is difficult to treat, with biofilm growth and the diffusion barrier to antibiotics presented by bone contributory factors. The aim of this study was to develop and evaluate an invitro model of osteomyelitis. A bioluminescent strain of Staphylococcus aureus was grown in bone blocks made from bovine femur. Light output was insufficient for detection of bacterial cells within bone by 24h and viable counting of crushed bone blocks was used to determine bacterial survival. Challenge of 72h biofilms with gentamicin and daptomycin for 24h demonstrated that only concentrations of 10 times the clinical peak serum target levels (100mgl−1 gentamicin and 1000mg l−1 daptomycin) resulted in significant reductions in cell viability compared to controls. Once daily dosing over 7days resulted in ≥3 log reductions in cell numbers by 48h. Thereafter no significant reduction was achieved, although emergence of resistance was suppressed. Determination of antibiotic concentration in bone blocks over 7days indicated that neither agent was able to consistently reach levels in bone of >10% of the original dose. The model was, therefore, able to demonstrate the challenges posed by biofilm growth on and within bone. Significance and Impact of the Study: The majority of studies of antibiotic efficacy in the treatment of chronic osteomyelitis are carried out in animals. We developed an invitro model of Staphylococcus aureus infection of bone to evaluate the ability of antibiotics to eradicate mature biofilms on surfaces analogous to necrotic bone. The results demonstrated the difficulties which occur in osteomyelitis treatment, with only very high concentrations of antibiotic able to penetrate the bone sufficiently to reduce bacterial survival whilst still failing to eradicate biofilms. This model could be of use in initial screening of novel compounds intended for use in the treatment of osteomyelitis