Rapid and sensitive detection techniques for foodborne pathogens are important to the food industry. However, traditional detection methods rely on bacterial culture in combination with biochemical tests, a process that typically takes 4 to 7 days to complete. Thus, this study was conducted to address the issue of time lag inherent in traditional methods by developing a novel PCR assay for each of five foodborne pathogenic bacteria. This new system consists of a simultaneous screening method using multiplex PCR in a single reaction tube for the rapid and sensitive detection of each of the five bacteria. Specific primers for multiplex PCR amplification of the Shiga-like toxin (verotoxin type II), femA (cytoplasmic protein), toxR (transmembrane DNA binding protein), iap (invasive associative protein), and invA (invasion protein A) genes were designed to allow simultaneous detection of Escherichia coli O157:H7, Staphylococcus aureus, Vibrio parahaemolyticus, Listeria monocytogenes, and Salmonella, respectively. To confirm the specificity of each primer pair for the respective target gene, three types of experiments were carried out using boiled cell lysates and their DNAs. In the multiplex PCR with mixed DNA samples, specific bands for corresponding genes were simultaneously detected from a single reaction. The detection of all five foodborne pathogenic bacteria could be completed in less than 24 h with this novel PCR method.

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Abstract. In this work, the radiation shielding analysis for a RTPV (Radioisotope Thermo-Photo-Voltaic) device using 238 PuO2 was performed to estimate the radiation dose distribution over source region and radiation doses in a specified tally zone. The radiation source intensities and spectra were evaluated with ORIGEN-S and the detailed shielding analyses were performed with MCNP6 and MONACO/MAVRIC (in SCALE 6.1). In particular, comparative shielding analysis using two different types of RTPV (cubic homogeneous source type and cylindrical heterogeneous source type) were performed to show their relative performances. The results show that the RTPV device using the heterogeneous cylindrical source type has lower dose values by 5~11% depending on the packing factor at the measurement cell than the one using the homogeneous cubic source type. The additional thermal analysis using COMSOL shows that the temperature distribution of the heterogeneous cylindrical source type is more flat than that of a homogeneous cubic source type.

Summary A radioisotope thermophotovoltaic (RTPV) system effectively converts the decay heat of radioisotopes into electricity via thermally radiated photons. In this work, a 500‐W thermal heat source unit including 238PuO2 radioisotope fuel, shielding material, and selective emitter is designed from the viewpoint of radiation safety, thermal performance, and overall conversion efficiency by considering various shielding materials, fuel configurations, and packing factor (PF), defined as the ratio of fuel region volume to total heat source enclosure volume including fuel cladding and shield. The design study starts with a reference cubic configuration and extends to the more complicated configurations having separate cylindrical fuels. The results of the study showed that the heat source unit design suggested here can reduce the total radiation dose, peak neutron fluence, and maximum temperature using separate cylindrical fuel rods. For example, a design having a separated 3 × 3 cylindrical fuel rod array of 30% PF increases the overall efficiency by ~39% with similar maximum temperature and radiation doses in comparison with the reference heat source unit with a single cubic module and a 10% PF. This demonstrates the importance of the proper design of the RTPV heat source unit.

Nafion has received great attention as a proton conductor that can block negative ions. Here, we report the effect of a Nafion coating on an anodic aluminium oxide (AAO) nanoporous membrane on its function of ion rejection and filtering depending on the electric field. In our experiments, Nafion, once coated, was used to repel the negative ions (anions) from the coated surface, and then selectively allowed positive ions (cations) to pass through the nanopores in the presence of an electric field. To demonstrate the proof-of-concept validation, we coated Nafion solution onto the surface of AAO membranes with 20 nm nanopores average diameter at different solution concentration levels. Vacuum filtration methods for Nafion coating were vertically applied to the plane of an AAO membrane. An electric field was then applied to the upper surface of the Nafion-coated AAO membrane to investigate if ion rejection and filtering was affected by the presence of the electric field. Both anions and cations could pass through the AAO nanopores without an electric field applied. However, only cations could well pass through the AAO nanopores under an electric field, thus effectively blocking anions from passing through the nanopores. This result shows that ion filtration of electrons has been selectively performed while the system also works as a vital catalyst in reactivating Nafion via electrolysis. A saturated viscosity ratio of Nafion solution for the coating was also determined. We believe that this approach is potentially beneficial for better understanding the fundamentals of selective ion filtration in nanostructures and for promoting the use of nanostructures in potential applications such as ion-based water purification and desalination system at the nanoscale in a massively electrically integrated format.