A novel iterative solution of the three dimensional electric field integral equation

A novel forward backward iterative scheme for solving the three-dimensional (3-D) electric field integral equation is presented. This communication details how a naive extension of a 2-D forward backward algorithm to 3-D problems results in convergence difficulties due to spurious edge effects. The method proposed in this communication postulates the use of local "buffer regions" to suppress these unwanted effects and ensure stability. Results are presented illustrating the convergence of the algorithm when applied to scattering by a 15λ square metallic plate with an aperture and a metallic right-angled wedge

Inactivation Efficacy of Atmospheric Air Plasma and Airborne Acoustic Ultrasound Against Bacterial Bioflms

Bioflms are complex microbial communities that present serious contamination risks to our environment and health. In this study, atmospheric air plasma and airborne acoustic ultrasound technology were applied to inactivate Escherichia coli and Listeria innocua bioflms. Both technologies were efcient in controlling, or completely inactivating, the target bacterial bioflms. Viability and metabolic assays, along with microscopy analysis, revealed that atmospheric air plasma and airborne acoustic ultrasound damaged both the bacterial bioflm cells and its structural integrity. Scanning electron microscopy images highlighted the disruption of the bioflms and pore formation in bacterial cells exposed to both the plasma and acoustic treatments. Elevated reactive oxygen and nitrogen species in bacterial cells treated with atmospheric air plasma, demonstrated their primary role in the observed bacterial inactivation process. Our fndings provide potential antimicrobial strategies to combat bacterial bioflms in the food and healthcare sectors

Assessment of the disinfection capacity and eco-toxicological impact of atmospheric cold plasma for treatment of food industry effluents

Generation of wastewater is one of the main environmental sustainability issues across food sector industries. The constituents of food process effluents are often complex and require high energy and processing for regulatory compliance. Wastewater streams are the subject of microbiological and chemical criteria, and can have a significant eco-toxicological impact on the aquatic life. Thus, innovative treatment approaches are required to mitigate environmental impact in an energy efficient manner. Here, dielectric barrier discharge atmospheric cold plasma (ACP) was evaluated for control of key microbial indicators encountered in food industry effluent. This study also investigated the eco-toxicological impact of cold plasma treatment of the effluents using a range of aquatic bioassays. Continuous ACP treatment was applied to synthetic dairy and meat effluents. Microbial inactivation showed treatment time dependence with significant reduction in microbial populations within 120 s, and to undetectable levels after 300 s. Post treatment retention time emerged as critical control parameter which promoted ACP bacterial inactivation efficiency. Moreover, ACP treatment for 20 min achieved significant reduction (≥2 Log10) in Bacillus megaterium endospores in wastewater effluent. Acute aquatic toxicity was assessed using two fish cell lines (PLHC-1 and RTG-2) and a crustacean model (Daphnia magna). Untreated effluents were toxic to the aquatic models, however, plasma treatment limited the toxic effects. Differing sensitivities were observed to ACP treated effluents across the different test bio-assays in the following order: PLHC-1 \u3e RTG-2 ≥ D. magna; with greater sensitivity retained to plasma treated meat effluent than dairy effluent. The toxic effects were dependent on concentration and treatment time of the ACP treated effluent; with 30% cytotoxicity in D. magna and fish cells observed after 24 h of exposure to ACP treated effluent for concentrations up to 5%. The findings suggest the need to employ wider variety of aquatic organisms for better understanding and complete toxicity evaluation of long-term effects. The study demonstrates the potential to tailor ACP system parameters to control pertinent microbial targets (mono/poly-microbial, vegetative or spore form) found in complex and nutritious wastewater effluents whilst maintaining a safe eco-toxicity profile for aquatic species

Diagnostics of a Large Volume Pin-to-Plate Atmospheric Plasma Source for the Study of Plasma Species Interactions with Cancer Cell Cultures

A large gap pin-to-plate, atmospheric pressure plasma reactor is demonstrated as means of in vitro study of plasma species interactions with cell cultures. By employing optical emission and optical absorption spectroscopy, we report that the pin-to-pate plasma array had an optimal discharge frequency for cell death of 1000 Hz in ambient air for the target cancer cell line; human glioblastoma multiform (U-251MG). The detected plasma chemistry contained reactive oxygen and nitrogen species including OH, N2, N2+, and O3. We show that, by varying the plasma discharge frequency, the plasma chemistry can be tailored to contain up to 8.85 times higher levels of reactive oxygen species as well as a factor increase of up to 2.86 for levels of reactive nitrogen species. At higher frequencies, reactive oxygen species are more dominant than reactive nitrogen species which allows for a more dynamic and controlled environment for sample study without modifying the inducer gas conditions. When used for treatment of culture media and cell cultures, variation of the plasma discharge frequency over the range 1000-2500 Hz demonstrated a clear dependence of the responses with the highest cytotoxic responses observed for 1000 Hz. We propose that the reactor offers a means of studying plasma-cell interactions and possible co-factors such as pro-drugs and nano particles for a large volume of samples and conditions due to the use of well plates

Effects of Cold Plasma on Surface, Thermal and Antimicrobial Release Properties of Chitosan Film

This work aims to analyze the effects of cold atmospheric air plasma treatment of antimicrobial chitosan film with different levels of thymol. Optical characterization of the dielectric barrier discharge showed the generation of reactive nitrogen and oxygen species by the system. A significant increase in the surface roughness was observed after cold plasma treatment of the films. No significant difference was observed in the thermal profile of the plasma-treated films. A significant increase in the thymol diffusion coefficient was observed after the plasma treatment for all the active films

Surface, Thermal and Antimicrobial Release Properties of Plasma-Treated Zein Films

The effects of dielectric barrier discharge plasma treatment on zein film containing thymol as an active ingredient were evaluated. The plasma discharge was optically characterized to identify the reactive species. A significant increase in the film roughness (p 0.05) was observed for the thermal properties of the antimicrobial films after DBD plasma treatment

Characterization of polylactic acid films for food packaging as affected by dielectric barrier discharge atmospheric plasma

Dielectric barrier discharge (DBD) air plasma is a novel technique for in-package decontamination of food, but it has not been yet applied to the packaging material. Characterization of commercial polylactic acid (PLA) films was done after in-package DBD plasma treatment at different voltages and treatment times to evaluate its suitability as food packaging material. DBD plasma increased the roughness of PLA film mainly at the site in contact with high voltage electrode at both the voltage levels of 70 and 80 kV. DBD plasma treatments did not induce any change in the glass transition temperature, but significant increase in the initial degradation temperature and maximum degradation temperature was observed. DBD plasma treatment did not adversely affect the oxygen and water vapor permeability of PLA. A very limited overall migration was observed in different food simulants and was much below the regulatory limits. Industrial relevance: In-package DBD plasma is a novel and innovative approach for the decontamination of foods with potential industrial application. This paper assesses the suitability of PLA as food packaging material for cold plasma treatment. It characterizes the effect of DBD plasma on the packaging material when used for in-package decontamination of food. The work described in this research offers a promising alternative to classical methods used in fruit and vegetable industries where in-package DBD plasma can serve as an effective decontamination process and avoids any post-process recontamination or hazards from the package itself

Reconfiguration and regulation of supply chains and HRM in times of economic crisis

This chapter reviews existing evidence on the reconfiguration and regulation of supply chains and employment relations during times of economic crisis. On the one hand, literature has highlighted pressures towards a degradation of standards as firms seek short-term cost advantages. This view is informed by various perspectives from organization studies to political economy but is united by the idea that structural changes in global capitalism drive how firms relate to their suppliers. On the other hand, it has been argued that counter-pressures range from consumer backlashes to the extension of formal and informal regulation across national boundaries. This undeniably heterogeneous literature has common themes suggesting that global forces may be mediated by existing embedded institutional arrangements at transnational, national and local level, and that there are still open-ended possibilities for social action. This chapter synthesizes and evaluates these two streams and identifies agendas for future research

Effects of dielectric barrier discharge (DBD) generated plasma on microbial reduction and quality parameters of fresh mackerel (Scomber scombrus) fillets

peer-reviewedThe effect of atmospheric cold plasma generated by a novel in-package dielectric barrier discharge (DBD) on microbial and quality parameters of mackerel fillets was investigated. DBD voltage (70 kV and 80 kV) and treatment time (1, 3 and 5 min) were studied. Within 24 h of DBD treatment, spoilage bacteria (total aerobic psychrotrophic, Pseudomonas and lactic acid bacteria) were significantly reduced. However, significant effects on lipid oxidation parameters (PV, Dienes) were observed for the treated samples. Both studied treatment factors, treatment voltage and time, significantly affected anti-microbial efficacy and lipid oxidation. Nevertheless, no changes in pH or colour (except for L*) were observed. These results suggest atmospheric cold plasma generated by DBD could be implemented as technology for fish processing, retaining product quality over its shelf life. However, further investigations are needed in order to implement this technology and to control and mitigate its limitations, mainly associated to increased oxidation

Quantification of rubidium as a trace element in beef using laser induced breakdown spectroscopy

This study evaluates the potential of laser induced breakdown spectroscopy (LIBS) coupled with chemometrics to develop a quantification model for rubidium (Rb) in minced beef. A LIBSCAN 150 system was used to collect LIBS spectra of minced beef samples. Beef liver was used to spike the Rb levels in minced beef. All samples were dried, powdered and pelleted using a hydraulic press. Measurements were conducted by scanning 100 different locations with an automated XYZ sample chamber. Partial least squares regression (PLSR) was used to develop the calibration model, yielding a calibration coefficient of determination (Rc2) of 0.99 and a root mean square error of calibration (RMSEC) of 0.05ppm. The model also showed good results with leave-one-out cross validation, yielding a cross-validation coefficient of determination (Rcv2) of 0.90 and a root mean square error of cross-validation (RMSECV) of 0.22ppm. The current study shows the potential of LIBS as a rapid analysis tool for the meat processing industry