Background: Salmonella is one of the most common food-borne pathogens that can cause illness. In this study, the sensitivity and the specificity of Aptamer-MAGNETIC BEAD Separation-Polymerase Chain Reaction (AMS-PCR) method were determined for Salmonella spp. detection. Methods: Different concentrations of Salmonella enterica were mixed with streptavidinMAGNETIC BEADs coated with biotinylated DNA aptamer. The bound bacteria were eluted and tested with PCR targeting the invA gene of Salmonella. Ten different serovars of Salmonella enterica and four non-Salmonella were tested to determine the specificity of the DNA aptamer. For field application, 14 different food samples were tested and compared with the culture method. Results: The limit of detection of AMS-PCR method was 102 CFU/ml which was 10 times more sensitive than conventional PCR without AMS (103 CFU/ml). The AMS-PCR assay showed high specificity as it detected ten different serovars of Salmonella enterica with no cross-reactivity with other food-borne pathogens. AMS-PCR reduced the analytical duration from 6 to 7 h instead of 4 days by the culture method. Conclusion: In comparison with the culture method, AMS helped to improve the upstream sample preparation in reducing the pre-enrichment and enrichment times. So, it seems that combining AMS with PCR is cost-effective and time-saving. In addition, it is highly specific for monitoring of Salmonella spp. in food chain.

This article investigates the effect of MAGNETIC field on the performance of a special shell-and-tube heat exchanger using FERRO-nanofluid. The heat exchanger comprises seven twisted oval tubes with triangular array mounted on a hexagonal cross section. Water/iron oxide nanofluid with a volume ratio of 4% is used as hot fluid in tubes and water is employed as cooling fluid in the shell. The flow regime is laminar and calculations are performed at different Reynolds numbers and various MAGNETIC fields. The governing equations include continuum, momentum, energy, and MAGNETIC field equations that are solved using a finite volume method. It is demonstrated that the wall temperature of the tubes at the output is lower when the MAGNETIC field is present compared to the case in which the MAGNETIC field is not applied. Applying the MAGNETIC field to the FERRO-nanofluid leads to an increase in the Nusselt Number by about two times, leading to an increase in thermal efficiency of the heat exchanger. Also, the effect of the MAGNETIC field was quite different with respect to the geometry and position of the tubes relative to the flow field. The effect of increasing the Nu in the first half of the twisting of the tube is approximately equal to the rate of reduction in the second half of the tube, resulting in a reduction in the impact of the MAGNETIC field intensity.

Pulsed Current MICRO Plasma Arc Welding (PCMPAW) is one of the most widely used welding processes in sheet metal manufacturing industry. In any fusion arc welding process, the weld BEAD geometry plays an important role in determining the mechanical properties of the weld, which helps to improve the weld quality. Moreover, the geometry of weld BEAD involves several simultaneous quality characteristics, such as front width, back width, front height and back height, which must closely be monitored, controlled and optimized. This paper presents the optimization of the PCMPAW process by using the grey relational analysis considering the aforementioned quality characteristics, which are of maximum front width and back width, also minimum front height and back height.In relation to this, experiments were performed under different welding conditions such as peak current, back current, pulse rate and pulse width using AISI 304L stainless steel sheets of 0.25mm thickness using Response Surface Method (RSM) based on Central Composite Design (CCD) experimental design. It was observed that optimal welding parameters were determined by the grey relational grade from the grey relational analysis and they were also verified through confirmation experiments.