The Effect of Bacterial Infection on the Biomechanical Properties of Biological Mesh in a Rat Model

BACKGROUND: The use of biologic mesh to repair abdominal wall defects in contaminated surgical fields is becoming the standard of practice. However, failure rates and infections of these materials persist clinically. The purpose of this study was to determine the mechanical properties of biologic mesh in response to a bacterial encounter. METHODS: A rat model of Staphylococcus aureus colonization and infection of subcutaneously implanted biologic mesh was used. Samples of biologic meshes (acellular human dermis (ADM) and porcine small intestine submucosa (SIS)) were inoculated with various concentrations of methicillin-resistant Staphylococcus aureus [10(5), 10(9) colony-forming units] or saline (control) prior to wound closure (n = 6 per group). After 10 or 20 days, meshes were explanted, and cultured for bacteria. Histological changes and bacterial recovery together with biomechanical properties were assessed. Data were compared using a 1-way ANOVA or a Mann-Whitney test, with p<0.05. RESULTS: The overall rate of staphylococcal mesh colonization was 81% and was comparable in the ADM and SIS groups. Initially (day 0) both biologic meshes had similar biomechanical properties. However after implantation, the SIS control material was significantly weaker than ADM at 20 days (p = 0.03), but their corresponding modulus of elasticity were similar at this time point (p>0.05). After inoculation with MRSA, a time, dose and material dependent decrease in the ultimate tensile strength and modulus of elasticity of SIS and ADM were noted compared to control values. CONCLUSION: The biomechanical properties of biologic mesh significantly decline after colonization with MRSA. Surgeons selecting a repair material should be aware of its biomechanical fate relative to other biologic materials when placed in a contaminated environment

Multidimensional signals and analytic flexibility: Estimating degrees of freedom in human speech analyses

Recent empirical studies have highlighted the large degree of analytic flexibility in data analysis which can lead to substantially different conclusions based on the same data set. Thus, researchers have expressed their concerns that these researcher degrees of freedom might facilitate bias and can lead to claims that do not stand the test of time. Even greater flexibility is to be expected in fields in which the primary data lend themselves to a variety of possible operationalizations. The multidimensional, temporally extended nature of speech constitutes an ideal testing ground for assessing the variability in analytic approaches, which derives not only from aspects of statistical modeling, but also from decisions regarding the quantification of the measured behavior. In the present study, we gave the same speech production data set to 46 teams of researchers and asked them to answer the same research question, resulting insubstantial variability in reported effect sizes and their interpretation. Using Bayesian meta-analytic tools, we further find little to no evidence that the observed variability can be explained by analysts’ prior beliefs, expertise or the perceived quality of their analyses. In light of this idiosyncratic variability, we recommend that researchers more transparently share details of their analysis, strengthen the link between theoretical construct and quantitative system and calibrate their (un)certainty in their conclusions

Offshore sourcing research framework: hydrexia case

As markets become increasingly competitive, original equipment manufacturers (OEMs) are outsourcing larger parts of their supply chain to external suppliers. These suppliers are frequently offshore, providing the OEM with considerable benefits but also creating the risk of associated problems. This paper provides a case study of Hydrexia, a small Australian company that has developed an innovative technology and is now ready to set up manufacturing. The potential benefits, the risks, and ways to mitigate the risks of outsourcing significant portions of the supply chain offshore are evaluated in this context

Value proposition of energy storage options for wind power output smoothing

Energy Storage Systems (ESS) provide a solution allowing higher levels of Renewable Energy (RE) integration into electricity systems, as the intermittency of RE power output can be addressed with storage solutions. This paper evaluates the value propositions of commercially available ESS for wind farms in Australia, focusing on power applications as a relevant market segment of the energy storage industry. Specifically, the ESS application analyzed in this paper is wind farm power output smoothing. First, a general techno-economic model is developed which considers the technical, economic, and regulatory aspects pertaining to ESS and wind farm connections. This model is then used to compare five technological ESS alternatives for meeting technical requirements associated with the wind farm operation. The comparison is performed using an Australian wind farm as a case study. The analysis shows that along with the investment costs of an ESS technology, the regulatory framework is a pivotal factor governing the value proposition of an ESS

Systems based on hypo-eutectic Mg-Mg2Ni alloys for medium to large scale hydrogen storage and delivery

Magnesium based metal hydrides have a number of attractive properties for hydrogen storage, particularly the high storage density and the safety benefits of low pressure operation. A hypo-eutectic Mg-Mg-2-Ni alloy has been developed. The material can be produced at a much lower cost than ball-milled materials while achieving a reversible storage of 6.5-7 wt% hydrogen at a rate of reaction that is acceptable for existing industrial applications.This alloy has been employed in a series of increasingly large prototype systems, reaching commercial scale in 2010 with a system storing 22 kg of hydrogen, appropriate for industrial merchant applications. The technology is also under development for larger scale applications such as refueling infrastructure and energy storage. This paper will discuss the potential applications of these systems and their technical and economic comparison to traditional compressed gas hydrogen storage and delivery. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved