A new sterilization technique of bovine pericardial biomaterial using microwave radiation

Bioprosthetic valves created from chemically treated natural tissues such as bovine pericardial biomaterial are used as heart valve scaffolds. Methods currently available for sterilization of biomaterial for transplantation include the application of gamma radiation and chemical sterilants. These techniques, however, can be problematic because they can be expensive and lead to a reduction in tissue integrity. Therefore, improved techniques are needed that are cost effective and do not disrupt the physical properties, functionality, and lifespan of the valvular leaflets. This study examined a novel technique using nonthermalmicrowave radiation that could lead to the inactivation of bacteria in bovine pericardial biomaterial without compromising valve durability. Two common pathogenic species of bacteria, Escherichia coli and Staphylococcus aureus, were used as test microorganisms. Optimized microwave parameters were used to determine whether inactivation of pathogenic bacteria from bovine pericardium could be achieved. In addition, the effect of microwave sterilization on tissue integrity was examined. The mechanical properties (assessed using dynamic mechanical analysis) and tensile strength testing (using a Universal Tensile Tester) as well as thermal analysis (using thermogravimetric analysis and differential scanning calorimetry) indicated that microwave sterilization did not compromise the functionality of bovine pericardial biomaterial. Scanning electron microscopy imaging and cytotoxicity testing also confirmed that the structure and biocompatibility of transplant biomaterial remained unaltered after the sterilization process. Results from the application of this newmicrowave (MW) sterilization technique to bovine pericardium showed that nearcomplete inactivation of the contaminant bacteria was achieved. It is concluded that nonthermal inactivation of pathogenic bacteria from bovine pericardial biomaterial could be achieved using microwave radiation

Determination of the enthalpy of solid phase transition for isotactic polypropylene using a modified DSC technique

This paper investigates the enthalpy of solid phase transition of isotactic polypropylene from the mesomorphic phase to the monoclinic crystal form using DSC. iPP fibres with either monoclinic crystal form or mesomorphic phase were obtained by varying the conditions of melt spinning. XRD and mechanical tests were used to confirm the crystal forms. It is found that conventional DSC techniques fail to detect the transition enthalpy; a technique using silicon oil as the thermal medium was then employed to determine the transition enthalpy, which is of 3% the melting enthalpy for crystallites with monoclinic form, or 6.1 J/g on 100% crystallinity basis

Enthalpy of Solid Phase Transition of Isotactic Polypropylene

Abstract not available

Design and fabrication of polymer microfluidic chip for ESI-MS

Abstract not reproduced here by request of the publisher. The text is available from: http://dx.doi.org/10.1117/12.768447

Ultrasonic inspection of adhesive bonds

This paper describes work undertaken as a collaboration between the Industrial Research Institute Swinburne and the School of Engineering Science at Swinburne University of Technology. The objective of the research program was to study the nature of adhesive bonds and to determine the feasibility of developing a non-destructive testing approach for the identification of 'good' and 'bad' bonds. This paper provides an overview of the types of non-destructive evaluation techniques that have been identified thus far, and their suitability for the purpose of detecting various bonding flaws

Mechanical response of poly(lactic acid)-based packaging under liquid exposure

The objective of this study was to examine the mechanical behavior of poly(lactic acid)-based packaging, which was subjected to an external load while undergoing dimensional and material property changes due to the diffusion of liquid through its thickness. We defined the characteristics of the material response by taking into account the changes in the properties due to liquid sorption. The material properties at any given location and time were dependent on the liquid content. In this article, we present the evolution of the mechanical behavior using a numerical stress model that accounts for the effects of the time, liquid content, temperature, and swelling-induced strain. We assumed that the deformation depended on the liquid concentration, but the liquid concentration could be obtained without the knowledge of the stress or strain

Electrospray from hot embossed polymer microfluidic chips formed using laser machined and electroformed tools

Abstract not reproduced here by request of the publisher. The text is available from: http://dx.doi.org/10.1117/12.810722

Recycling of engineering thermoplastics used in consumer electrical and electronic equipment

Diminishing land fill capacity and increased volume of waste electrical and electronic equipment (WEEE) are the main drivers for the recycling of engineering thermoplastics. WEEE can be recycled in bulk or as separated components of a disassembled machine. Bulk recycling is the economically preferred option, however the blending of incompatible plastics without modification often limits the end use of the recycled plastics. The decision to apply expensive sorting techniques at the end of a products life should be based on mechanical properties and processability of the engineering thermoplastics contaminated by other polymeric materials. This paper investigates properties of various recycled thermoplastic blends to determine the degree of sorting required. Focusing on Acrylonitrile-Butadiene-Styrene (ABS) as the main component, six ABS/PP (polypropylene) blends, three ABS/Nylon and three ABS/HIPS (high impact polystyrene) blends were prepared on a single screw extruder. Mechanical and thermal properties were analyzed by comparison with pure virgin and recycled materials, as well as selected virgin blends. The results show that generally, these thermoplastics should be separated prior to processing to optimize the properties of the recycled plastics. However, some particular blends have sufficient mechanical properties such that they can be used for various applications where the use of sorting techniques is not economically viable