Salmonella Typhimurium continues to be a leading cause of human gastroenteritis worldwide. This organism is a facultative intracellular pathogen, meaning that it is able grow and reproduce within the host cell it inhabits. S. Typhimurium has the ability to invade and replicate within human intestinal epithelial cells, which in turn causes induced cell death or apoptosis. The human intestinal epithelial cells, HCT-8, were challenged with live, heat inactivated, and electron beam inactivated S. Typhimurium for various time points. Infected cell monolayers were collected for RNA extractions, and Real-time PCR was performed on the samples to analyze differential gene expression. Genes of the host cell that were expected to be differentially expressed were shortlisted and Real-Time PCR analysis was performed. Internalized Salmonella within the host cell was unable to be successfully visualized using fluorescent light microscopy. However, differential gene expression for a common transcriptional regulator and inflammatory chemokine were observed to be expressed significantly higher in response to e-beam inactivated Salmonella infection. Genes coding for extracellular and intracellular pattern-recognition receptors of the host cells were shown to be up-regulated in response to e-beam inactivated Salmonella infection at 4 and 24 hours, but were not statistically significant. Additional studies must be conducted to definitively confirm e-beam irradiated Salmonella has the ability to invade human host cells.

Increase in consumption of fresh produce over the past decade has resulted in a rise in incidents of foodborne outbreaks due to pathogens. Chemical sanitizers have been extensively used in the industry for decontamination of fresh produce. However, they are ineffective in certain commodities and under certain processing conditions, necessitating the evaluation of alternative technologies. Electron beam irradiated sliced cantaloupe were tested for 21 days of storage for total aerobic bacterial counts, texture, color and sensory parameters as a function of irradiation doses 0, 0.7 and 1.4 kGy and the wash treatments, water and 200 mg/L chlorine applied to the melons before cutting. Melons washed only with water prior to cutting had total aerobic bacterial counts of 4.0, 2.0 and 0.8 log cfu/g on day 0 at irradiation doses of 0, 0.7 and 1.4 kGy respectively. On day 0, melons washed with chlorine prior to cutting had total aerobic bacterial counts of 2.7, and 0.7 log cfu/g at irradiation doses of 0 and 0.7 kGy and below detection limit at 1.4 kGy. Texture measured as compression force was lower only for cantaloupe irradiated at 1.4 kGy. Irradiation did not affect objective color and descriptive attribute flavor and texture sensory attributes of cantaloupe. Irradiation reduced Salmonella Poona by 1.1 log cfu/g at 0.7 kGy and 3.6 log cfu/g at 1.5 kGy. The D-value of S. Poona on irradiated sliced cantaloupe was found to be 0.211 kGy. Among the spoilage organisms, lactic acid bacteria and mold were reduced effectively by irradiation but there was no significant effect on reduction of yeasts. Our results show that electron beam irradiation in combination with chemical sanitizers is effective in decontamination of fresh-cut produce. Electron microscopy images provided valuable information on attachment sites of S. Poona on cantaloupe rind. The ineffectiveness of chemical sanitizers due to possible inaccessibility to pathogens in these attachment sites provides the basis for application of irradiation in decontamination of fresh produce.

Mushrooms are one of the protein rich foods, however they have a short pro-harvest life (2 to 3 days) compared to most vegetables. The aim of this study was to evaluate whether applying an anti-browning solution using vacuum impregnation and then electron beam irradiation can be used to extend the shelf life of fresh-cut mushrooms (Agaricus bisporus). Solutions made with (a) 2% ascorbic acid + 1% calcium lactate, (b) 2% citric acid + 1% calcium lactate, (c) 1% chitosan + 1% calcium lactate, and (d) 1% calcium lactate were used to impregnate mushroom slices at different vacuum pressures, vacuum pressure times, and atmospheric restoration times. Mushrooms were also irradiated at a dose of 1 kGy using a 1.35 MeV e-beam accelerator and their quality was evaluated in terms of color, texture, and microbial growth during 15 days storage at 4 degrees C. The best vacuum impregnation treatment was the 2% ascorbic acid and 1% calcium lactate solution using a vacuum pressure of 50 mmHg for 5 minutes and an atmospheric restoration time of 5 minutes. The control (not treated) and impregnated samples lost their structure (softening) during storage. The irradiated samples lost their firmness by day 4 of storage. The addition of calcium lactate to the samples during the treatment helped to keep the product’s texture during the 15 days storage time. Color of the mushrooms changed during storage for all the control and impregnated samples and only the irradiated samples showed an acceptable color by the end of day 15. Aerobics and psychrotrophics counts were significantly reduced by irradiation; while yeast and molds population increased by day 9 and were not completely inactivated with a dose of 1 kGy. Sensory panelists preferred the treated samples over the controls. The best treatment was the combination of vacuum impregnation with irradiation according to the consumer studies.

The irradiation of high Tc superconducting thin films with a focused electron beam, such as that obtained in a scanning transmission electron microscope (STEM), can result in the formation of a Josephson junction. The conditions required for the formation of these Josephson junctions in YBa2Cu3O7-d and related compounds are discussed as well as the physical properties of the irradiated material. From electrical transport measurements of individual Josephson junctions it was found that these junctions have a Superconductor/Normal/Superconductor (SNS) nature. Low temperature anneal studies indicate that Josephson junctions with optimum properties can be obtained by a combination of a high electron dose and subsequent low temperature anneal. Extremely high electron doses resulted in the formation of a purely resistive region. The electrical transport in such regions with a dimension of 200 nm in the direction of current transport is shown to be compatible with variable range hopping (VRH). Barriers with the same length but a finite superconducting transition temperature showed a low bias resistance that is significantly lowered due to proximity coupling. Using purely resistive regions in combination with Josephson junctions, devices consisting of two closely spaced Josephson junctions with a third terminal connected to the shared electrode were fabricated and characterised (minimum separation 20 nm). The distinct behaviour of the Josephson critical current with applied magnetic field (Ic(B)) of these devices was found to be well described by a newly developed model, which incorporates the effect of the static redistribution current in the shared electrode on the phase distribution of the Josephson junctions. An important finding is that the behaviour of the high critical current with applied magnetic field of two closely spaced junctions was found to be consistent with a model system consisting of a closely spaced Josephson junction and a resistive barrier. A three terminal device with Josephson junctions at small separations was found to have a significantly increased trans resistance when compared with the individual resistance of the Josephson junctions it constituted of. A number of illustrative examples of device structures realised with the focused electron beam irradiation technique are also included.

Yes / We have synthesised osmium nanoparticles of defined size (1.5–50 nm) on a B- and S-doped turbostratic graphitic structure by electron-beam irradiation of an organometallic osmium complex encapsulated in self-spreading polymer micelles, and characterised them by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and atomic force microscopy (AFM) on the same grid. Oxidation of the osmium nanoparticles after exposure to air was detected by X-ray photoelectron spectroscopy (XPS). / We thank the Leverhulme Trust (Early Career Fellowship No. ECF-2013-414 to NPEB), the University of Warwick (Grant No. RD14102 to NPEB), the ERC (Grant No. 247450 to PJS), and the EPSRC (EP/F034210/1 to PJS). L.M.A.P., J.L., and G.C. acknowledge financial support from the EU through the ERC Consolidator Grant “VISUAL-MS”.

As indústrias têxteis desempenham um importante papel na economia nacional e mundial. Entretanto, do ponto de vista ambiental, suas atividades são consideradas como potencialmente poluidoras e utilizadoras de recursos naturais. Os corantes azo reativos são os principais corantes utilizados no setor para o tingimento do algodão no Brasil e no mundo. Devido à sua baixa fixação à fibra e a variações no processo de produção, cerca de 30 % da concentração inicial utilizada nos banhos de tingimento são perdidos e vão compor o efluente final. Esses compostos apresentam uma baixa biodegradabilidade e elevada solubilidade em água e, por isso, não são completamente removidos pelos processos biológicos convencionais. Os corantes quando descartados sem tratamento adequado no corpo dágua receptor podem causar modificações estéticas, alterar a fotossíntese e a solubilidade dos gases, além de serem tóxicos e genotóxicos para a biota. Os principais objetivos do trabalho foram avaliar a toxicidade e genotoxicidade de dois diferentes corantes azo reativos (Remazol Preto B RPB e Remazol Alaranjado 3R R3AR) e a eficiência de redução da cor e toxicidade após o uso da radiação com feixe de elétrons. Também foi analisada a toxicidade dos corantes em diferentes formas químicas, que podem ser encontradas nos efluentes. Os ensaios de toxicidade aguda realizados com Vibrio fischeri, Daphnia similis e Biomphalaria glabrata evidenciaram diferentes padrões de resposta para os corantes. Os dois corantes em suas formas químicas foram levemente tóxicos para Vibrio fischeri, com exceção da forma vinilsulfona do corante RPB que foi tóxico (CE(I)5015min = 6,23 mg L-1). Nos ensaios com Daphnia similis, o corante RPB foi levemente tóxico na sua forma original, sulfatoetilsulfona (CE(I)5048h = 91,25 mg L-1) e não apresentou toxicidade nas demais formas químicas. Entretanto, o corante RA3R foi tóxico para o dafnídeo, sendo muito tóxico na forma vinilsulfona (CE(I)5048h = 0,54 mg L-1). Não foi observada toxicidade nos ensaios com o organismo Biomphalaria glabrata. A toxicidade crônica foi avaliada com o organismo Ceriodaphnia dubia e o corante RPB apresentou valores de CENO e CEO iguais a 12,5 e 25 mg L-1, respectivamente, para a forma sulfatoetilsulfona. Após a hidrólise do corante (vinilsulfona e hidroxietilsulfona) foi observado um aumento os valores obtidos de CENO e CEO. Não foi verificado efeito crônico para o corante R3AR e suas formas químicas. O teste do cometa adaptado para o caramujo Biomphalaria glabrata foi utilizado para avaliar a genotoxicidade dos corantes. O corante RPB apresentou genotoxicidade nas concentrações mais elevadas (1 e 2 g L-1), com valores de dano quantitativo de 117 e 112 e o R3AR não foi genotóxico. O uso da radiação com feixes de elétrons demonstrou eficácia na remoção da cor dos corantes. Com a dose de 10 kGy foi possível uma redução de 97,64 % para RPB e de 96,8 % para R3AR. Após irradiação do corante RPB com a dose de 10 kGy foi evidenciada uma redução de 59,52 % da toxicidade aguda avaliada com Vibrio fischeri. Nas demais doses não houve redução significativa, assim como na avaliação com Daphnia similis, onde os valores de CE(I)5048h obtidos foram menores que o corante não irradiado. O corante R3AR apresentou diminuição da toxicidade mais acentuada após a radiação quando comparado com o RPB, com reduções de 82,95 % (V. fischeri) e 71,26 % (D. similis) com 10 kGy. / The textile industries play an important role in national and global economy. But, their activities are considered potentially polluting. The use of large volumes of water and the production of colored wastewater with high organic matter are among the main issues raised, especially during the stage of dyeing and washing of the textile process. The reactive azo dyes are the main colors used in the industry for dyeing of cotton in Brazil and worldwide. Because of its low setting and variations in the fiber production process, about 30% of the initial concentration used in the dyeing baths are lost and will compose the final effluent. These compounds have a low biodegradability, are highly soluble in water and therefore are not completely removed by conventional biological processes. In addition, other processes do not promote degradation but the tranference to solid environment. The dyes discarded without treatment in the water body can cause aesthetic modifications, alter photosynthesis and gas solubility, as well as being toxic and genotoxic. The main objectives of this study were to evaluate the toxicity and genotoxicity of two reactive azo dyes (Remazol Black B - RPB and Remazol Orange 3R R3AR) and the percentage of color and toxicity reduction after the use of electron beam radiation. The acute toxicity assays performed with Vibrio fischeri, Daphnia similis and Biomphalaria glabrata showed different response patterns for dyes. The different chemical forms of dyes were slightly toxic to Vibrio fischeri and only the RPB dye (vinylsulphone) was toxic (EC5015min = 6,23 mg L-1). In tests with Daphnia similis, the dye RPB was slightly toxic in its patern form, sulphatoethylsulphone, (CE5048h = 91,25 mg L-1) and showed no toxicity in other chemical forms. However, the RA3R dye was toxic to the dafnids and the vinylsulphone form very toxic (EC5048h = 0,54 mg L-1). No toxicity was observed in Biomphalaria glabrata assays. Chronic toxicity was assessed with the organism Ceriodaphnia dubia and the NOEC and OEC values of RPB dye (sulphatoethylsulphone) were 12.5 and 25 mg L-1, respectively. After hydrolysis of the dye (vinylsulphone and hydroxyethylsulphone) was shown to increase the values obtained from the NOEC ans OEC. There was no chronic effect for the R3AR dye and its chemical forms to C. dubia. The comet assay adapted to hemocytes of Biomphalaria glabrata was used to assess the genotoxicity of the dyes. The RPB dye was genotoxic at highest concentrations (1 and 2 g L-1), with quantitative values of DNA damage equal to 117 and 112 and the R3AR dye was not genotoxic. The use of radiation with electron beams have proven effective in removing the color dyes. With a dose of 10 kGy a reduction of 97.64% and 96.8% for R3AR and RPB, respectively, was achievied. Possibly, the color removal was mainly due to the interaction of reactive species such as hydroxyl radicals generated in the radiolysis of water after the radiation beam of electrons. After radiation of the RPB dye a dose of 10 kGy reduced 59.52 % of the acute toxicity measured with Vibrio fischeri. For the other doses there was no significant reduction, as well as with Daphnia similis, where the values of EC5048h obtained were smaller than the non-irradiated dye. The R3AR dye showed better decreased toxicity after radiation when compared with the RPB, with reductions of 82.95% (V. fischeri) and 71.26% (D. similis) with 10 kGy.

As indústrias têxteis desempenham um importante papel na economia nacional e mundial. Entretanto, do ponto de vista ambiental, suas atividades são consideradas como potencialmente poluidoras e utilizadoras de recursos naturais. Os corantes azo reativos são os principais corantes utilizados no setor para o tingimento do algodão no Brasil e no mundo. Devido à sua baixa fixação à fibra e a variações no processo de produção, cerca de 30 % da concentração inicial utilizada nos banhos de tingimento são perdidos e vão compor o efluente final. Esses compostos apresentam uma baixa biodegradabilidade e elevada solubilidade em água e, por isso, não são completamente removidos pelos processos biológicos convencionais. Os corantes quando descartados sem tratamento adequado no corpo dágua receptor podem causar modificações estéticas, alterar a fotossíntese e a solubilidade dos gases, além de serem tóxicos e genotóxicos para a biota. Os principais objetivos do trabalho foram avaliar a toxicidade e genotoxicidade de dois diferentes corantes azo reativos (Remazol Preto B RPB e Remazol Alaranjado 3R R3AR) e a eficiência de redução da cor e toxicidade após o uso da radiação com feixe de elétrons. Também foi analisada a toxicidade dos corantes em diferentes formas químicas, que podem ser encontradas nos efluentes. Os ensaios de toxicidade aguda realizados com Vibrio fischeri, Daphnia similis e Biomphalaria glabrata evidenciaram diferentes padrões de resposta para os corantes. Os dois corantes em suas formas químicas foram levemente tóxicos para Vibrio fischeri, com exceção da forma vinilsulfona do corante RPB que foi tóxico (CE(I)5015min = 6,23 mg L-1). Nos ensaios com Daphnia similis, o corante RPB foi levemente tóxico na sua forma original, sulfatoetilsulfona (CE(I)5048h = 91,25 mg L-1) e não apresentou toxicidade nas demais formas químicas. Entretanto, o corante RA3R foi tóxico para o dafnídeo, sendo muito tóxico na forma vinilsulfona (CE(I)5048h = 0,54 mg L-1). Não foi observada toxicidade nos ensaios com o organismo Biomphalaria glabrata. A toxicidade crônica foi avaliada com o organismo Ceriodaphnia dubia e o corante RPB apresentou valores de CENO e CEO iguais a 12,5 e 25 mg L-1, respectivamente, para a forma sulfatoetilsulfona. Após a hidrólise do corante (vinilsulfona e hidroxietilsulfona) foi observado um aumento os valores obtidos de CENO e CEO. Não foi verificado efeito crônico para o corante R3AR e suas formas químicas. O teste do cometa adaptado para o caramujo Biomphalaria glabrata foi utilizado para avaliar a genotoxicidade dos corantes. O corante RPB apresentou genotoxicidade nas concentrações mais elevadas (1 e 2 g L-1), com valores de dano quantitativo de 117 e 112 e o R3AR não foi genotóxico. O uso da radiação com feixes de elétrons demonstrou eficácia na remoção da cor dos corantes. Com a dose de 10 kGy foi possível uma redução de 97,64 % para RPB e de 96,8 % para R3AR. Após irradiação do corante RPB com a dose de 10 kGy foi evidenciada uma redução de 59,52 % da toxicidade aguda avaliada com Vibrio fischeri. Nas demais doses não houve redução significativa, assim como na avaliação com Daphnia similis, onde os valores de CE(I)5048h obtidos foram menores que o corante não irradiado. O corante R3AR apresentou diminuição da toxicidade mais acentuada após a radiação quando comparado com o RPB, com reduções de 82,95 % (V. fischeri) e 71,26 % (D. similis) com 10 kGy. / The textile industries play an important role in national and global economy. But, their activities are considered potentially polluting. The use of large volumes of water and the production of colored wastewater with high organic matter are among the main issues raised, especially during the stage of dyeing and washing of the textile process. The reactive azo dyes are the main colors used in the industry for dyeing of cotton in Brazil and worldwide. Because of its low setting and variations in the fiber production process, about 30% of the initial concentration used in the dyeing baths are lost and will compose the final effluent. These compounds have a low biodegradability, are highly soluble in water and therefore are not completely removed by conventional biological processes. In addition, other processes do not promote degradation but the tranference to solid environment. The dyes discarded without treatment in the water body can cause aesthetic modifications, alter photosynthesis and gas solubility, as well as being toxic and genotoxic. The main objectives of this study were to evaluate the toxicity and genotoxicity of two reactive azo dyes (Remazol Black B - RPB and Remazol Orange 3R R3AR) and the percentage of color and toxicity reduction after the use of electron beam radiation. The acute toxicity assays performed with Vibrio fischeri, Daphnia similis and Biomphalaria glabrata showed different response patterns for dyes. The different chemical forms of dyes were slightly toxic to Vibrio fischeri and only the RPB dye (vinylsulphone) was toxic (EC5015min = 6,23 mg L-1). In tests with Daphnia similis, the dye RPB was slightly toxic in its patern form, sulphatoethylsulphone, (CE5048h = 91,25 mg L-1) and showed no toxicity in other chemical forms. However, the RA3R dye was toxic to the dafnids and the vinylsulphone form very toxic (EC5048h = 0,54 mg L-1). No toxicity was observed in Biomphalaria glabrata assays. Chronic toxicity was assessed with the organism Ceriodaphnia dubia and the NOEC and OEC values of RPB dye (sulphatoethylsulphone) were 12.5 and 25 mg L-1, respectively. After hydrolysis of the dye (vinylsulphone and hydroxyethylsulphone) was shown to increase the values obtained from the NOEC ans OEC. There was no chronic effect for the R3AR dye and its chemical forms to C. dubia. The comet assay adapted to hemocytes of Biomphalaria glabrata was used to assess the genotoxicity of the dyes. The RPB dye was genotoxic at highest concentrations (1 and 2 g L-1), with quantitative values of DNA damage equal to 117 and 112 and the R3AR dye was not genotoxic. The use of radiation with electron beams have proven effective in removing the color dyes. With a dose of 10 kGy a reduction of 97.64% and 96.8% for R3AR and RPB, respectively, was achievied. Possibly, the color removal was mainly due to the interaction of reactive species such as hydroxyl radicals generated in the radiolysis of water after the radiation beam of electrons. After radiation of the RPB dye a dose of 10 kGy reduced 59.52 % of the acute toxicity measured with Vibrio fischeri. For the other doses there was no significant reduction, as well as with Daphnia similis, where the values of EC5048h obtained were smaller than the non-irradiated dye. The R3AR dye showed better decreased toxicity after radiation when compared with the RPB, with reductions of 82.95% (V. fischeri) and 71.26% (D. similis) with 10 kGy.

Increase in consumption of fresh cut produce over the past decade has resulted in a rise in incidents of food borne outbreaks due to pathogens. Conventional techniques of sanitizing washes may not be effective since the organic matter released from the fresh produce use up the free chlorine thus reducing the sanitizing potential of wash water just when it is needed most and a heat treatment step to kill pathogens cannot be applied if the purpose is to consume fresh produce. Electron beam (e-beam) irradiation was used to treat cut cantaloupe, cut roma tomatoes, baby spinach, romaine lettuce which were surface inoculated with a cocktail of Salmonella and E. coli O157:H7. Results showed that irradiation reduced Salmonella and E. coli O157:H7 significantly with increasing doses at 0.2, 0.4, 0.6, 0.8, and 1.0 kGy. The D10-value for Salmonella on irradiated cut cantaloupe, cut roma tomatoes, baby spinach, and romaine lettuce was found to be 0.71 kGy, 0.64 kGy, 0.19 kGy, and 0.23 kGy respectively. The D10-value for E. coli O157:H7 on the produce listed above was found to be 0.73 kGy, 0.54 kGy, 0.18 kGy, and 0.20 kGy respectively. Low dose e-beam irradiation was found to be an excellent tool for ensuring the reduction of spoilage organisms and extending shelf life in cut cantaloupe, cut roma tomatoes, baby spinach, romaine lettuce, strawberries, and green onion. The produce were tested for 12 days of storage for aerobic plate count, yeast and mold, lactic bacteria, color, texture, and respiration rate as a function of irradiation doses 0, 1, 3, and 5 kGy. Aerobic plate counts, yeast counts, and lactic acid bacteria were reduced appreciably at all doses tested on all commodities. Molds did not grow on any samples including control for cut cantaloupe, cut tomatoes, and green onion but for the other commodities, mold was reduced at the same rate as yeasts and vegetative bacteria. Lactic acid bacteria were reduced at all doses while the reduction was highest with 5 kGy in all commodities. When irradiated with 5 kGy, during storage, strawberries, spinach, and green onion displayed wet, soggy and mushy appearance, romaine lettuce leaves were wilted, had a translucent midrib and brown pigmentation. E-beam irradiation increased respiration rate for all samples on day 0 compared to non-irradiated control irrespective of the commodity type and the effect was dose dependent. Firmness reduced appreciably for cut roma tomatoes, baby spinach, strawberries, romaine lettuce, and green onion with increasing doses. Cut cantaloupe was low in firmness but the effect was not dose dependent. Irradiation at low doses is a promising tool to reduce pathogens and enhance keeping quality of cut cantaloupe, cut tomatoes, baby spinach, romaine lettuce, strawberries, and green onion. Irradiation is to be implemented as part of an overall HACCP plan and is not meant to replace existing control measures.

This study evaluated the potential use of an antimicrobial packaging system in combination with electron beam irradiation to enhance quality of fresh produce. Irradiated romaine lettuce up to 3.2 kGy showed negligible (p > 0.05) changes in color, but texture and sensory attributes were less acceptable with increased dose. We established the antimicrobial effectiveness of various active compounds incorporated into the low-density polyethylene (LDPE)/polyamide films to increase radiation sensitivity of surrogate bacteria (Listeria innocua and Escherichia coli). All films showed inhibition zones in an agar diffusion test. In the liquid culture test, the active compounds reduced the specific growth rate and decreased final cell concentration of strains. Films incorporated with active compounds increased the radiation sensitivity of the tested strains, demonstrating their potential to reduce the dose required to control microbial contamination using electron beam technology. The active compounds maintained their antimicrobial activity by exposure to ionizing radiation up to 3 kGy. Antimicrobial activity of LDPE/polyamide films incorporated with transcinnamaldehyde was tested with fresh-cut romaine lettuce. Total aerobic plate counts (APC) and yeast and mold counts (YMC) were determined as a function of dose (0, 0.5, and 1.0 kGy) for 14 days of storage at 4°C. Irradiation exposure significantly lowered APCs of lettuce samples by 1-log CFU/g compared to the non-irradiated controls; however, it only slightly reduced YMCs. The effectiveness of using irradiation with antimicrobial films was enhanced with increased radiation dose and transcinnamaldehyde concentration. Electron beam irradiation up to 20 kGy did not affect the tensile strength and toughness of the polymeric films. The film’s flexibility and barrier properties were significantly improved by exposure to 20 kGy. The addition of an active compound did not affect the tensile strength and barrier properties of the films, but decreased the percent elongation-at-break and toughness, making them slightly more brittle. Ionizing radiation affected the release kinetics of the antimicrobial agent from the packaging material into a model food system. Irradiated films exhibited slower release rates than non-irradiated film by 69%. In addition, release rate was lower at 4ºC by 62.6% than at 21-35ºC. The pH of the simulant solution affected release rate with pH 4 yielding higher rates than pH 7 and 10.

Commercial sterilization of medical devices may be performed using electron beam irradiators, which operate at various electron energies. The potential for activating components of the devices has been discussed, with current standards stating that an electron energy greater than 10 MeV requires assessment of potential induced radioactivity. There does not appear to be a literature citation for this energy limit, but it is the accepted default assumption within the industry. This research was directed at evaluating potential activation in medical products sterilized in electron beam as a function of the electron maximum energy. Monte Carlo simulation of a surrogate medical device was used to calculate photon and neutron fields resulting from electron irradiation, which were used to calculate concentrations for several radionuclides. The predominant mechanism for inducing radioactivity is photoneutron production in metal elements. Other mechanisms, including photoneutron production in deuterium with subsequent neutron capture, neutron capture of the photoneutrons produced in metal elements, and isomeric excitation, are all possible means of inducing radioactivity in similar conditions, but none made a perceptible contribution to activation in these experiments. The experiments confirmed that 10 MeV is a conservative assumption that any lower energy does not create significant activation. However, in the absence of a limited number of elements, the amount of induced radioactivity at 11 MeV and 12 MeV could also be considered insignificant. When based on an estimate of the amount of metal present in a medical device, the sum-of-fractions comparison to the US Nuclear Regulatory Commission exempt concentration limits is less than unity for all energies below 12.1 MeV, which suggests that there is minimal probability of significant induced activity at energies above the generally-accepted standard 10 MeV upper energy limit. / text