We consider the problem of decontaminating a network where all nodes are infected by a virus. The decontamination strategy is performed using a Cellular Automata (CA) model in which each node of the network is represented by the automata cell and thus, the network host status is also mapped to the CA state (contaminated, decontaminating, decontaminated). All hosts are assumed to be initially contaminated and the status of each cell is synchronously updated according to a set of local rules, based on the state of its neighbourhood. Our goal is to find the set of local rules that will accomplish the decontamination in an optimal way. The metrics used to define optimality is the minimization of three metrics: the maximum number of decontaminating cells at each step, the required value of the immunity time of each cell and the number of steps to complete the sanitization algorithm. In our research, we explore the designing of these local decontamination rules by refining the concept of the neighbourhood radius of CA with the addition of two new dimensions: Visibility Hop and Contamination Distance. Additionally, a research tool that help us manage our study have been developed.

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M.Sc. (Chemistry) / Zero-valent nanoscale metal, especially iron nanoparticles have attracted significant attention with regards to remediation of organochlorinated compounds in drinking water. For a more rapid and complete dechlorination, a second and usually electronegative element is often added, resulting in the formationof bimetallic nanoparticles. However, in the absence of surfactants,the bimetallic nanoparticles easily aggregate into large particles (if they are not anchored on solid supports) with wide size distributions, thus losing their reactivity. This work reports an in-situ synthesis method of bimetallic nanoparticles immobilized on L-lysine functionalized microfiltration membranes by chemical reduction of metal ions chelated by amine and hydroxyl functional groups of L-lysine on the composite. The immobilization of the nanoparticles on membranes offers many advantages: reduction of particle loss, prevention of particle agglomeration and application under convective flow. The objective of this research wasto produce catalytic filtration membranes for dechlorination of organic compound, PCB-77. This was achieved first by (i) the modification of commercial PVDF to introduce functional groups that render the membrane more hydrophilic and have the ability to capture metal ions through chelation, and secondly (ii) the controlled introduction of catalytic nanoparticles onto the composite membrane surface, anchored through chelation to the surface functional groups. This approach was selected with aview to produce uniform surface distribution of monodispersed bimetallic nanoparticles that are resistant to leaching during the reduction reactions. The modification of the PVDF membrane was achieved by firstly performing an in situ polymerization of acrylic acid followed by covalently bonded L-lysine to the polymerized acrylic acid chains using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC). The Fe ions were introduced to the composite by L-lysine chelation and subsequently reduced to Fe0 with NaBH4, and finally deposition of Ni2+ which later were also reduced to Ni0 with NaBH4. The Fe/Ni bimetallic NPs system was chosen based on its proven ability for the total dechlorination of chlorinated organic compounds. Systematic characterization of the composite was performed using ATR-FTIR, FESEM, EDS, HRTEM, XRD, AFM and Contact Angle measurements. A relatively uniform distribution of Fe/Ni nanoparticles was found in L-lysine/PAA/PVDF membrane. The diameter of Fe/Ni nanoparticles was predominantly within the range 20-30 nm. Furthermore, the mechanism of the catalytic dechlorination of the model compound, PCB 77, was investigated by careful analysis of the reaction products. It is generally known that zero-valent iron undergoes corrosion to provide hydrogen atoms and electrons for the reductive catalytic hydrodechlorination reaction. The second metal in the bimetallic system on the other hand, acts as...

The reductive dechlorination of chlorobiphenyls in sediment by titanium(III) citrate-reduced vitamin Bus was studied in batch reactors. Long term ampoule studies demonstrated reductive dechlorination of sediment-sorbed 2,3,4,5,6-pentachlorobiphenyl (2,3,4,5,6-PeCB) to tetra-, tri-, di-, and monochlorobiphenyl products. Over 50% chlorine removal was observed over 160 days. The results of the ampoule experiment were compared to previous experiments with aqueous PCBs, and both systems appeared to follow the same pathway. Theoretical product distributions based on free energies of formation were compared to product distributions for the ampoule experiments, and both aqueous and sediment-sorbed PCB reductive dechlorination followed the thermodynamically favored pathway. Although chlorines were removed from all positions, reductive dechlorination was generally preferred at the ortho position. / Graduation date: 1999

Salmonella and Escherichia coli O157:H7 (EC) contamination continues to be one of the major concerns for the microbiological safety of raw poultry and beef products. Application of more than one decontamination agent as a multi-hurdle intervention to carcasses in a processing line might produce greater reductions than one treatment alone due to different modes of action of individual antimicrobials. In this study, sequential spray applications of e-polylysine (EPL), lauric arginate and acidic calcium sulfate (ACS) solutions were evaluated against Salmonella Enteritidis (SE) and Salmonella Typhimurium (ST) on artificially inoculated broiler carcasses and against ST and EC on beef rounds and ground beef derived from the rounds. All possible 2-way combinations and individual applications of 20 % ACS (ACS20), 300 mg/liter EPL (EPL300) and 200 mg/liter LAE (LAE200) were evaluated using a sterile membrane filter model system. The combinations that provided higher Salmonella reductions were further evaluated on inoculated chicken carcasses using either response surface methodology (RSM) or in various concentrations applied in a sequential manner. Sequential spray applications of EPL300 - ACS 30 % (ACS30) or LAE200-ACS30 produced the highest Salmonella reductions on inoculated chicken carcasses. In a subsequent experiment, treatment of Salmonella inoculated carcasses with EPL300-ACS30 or LAE200-ACS30 combinations were found effective for reducing initial Salmonella counts by 1.5 and 1.8 log CFU/ml, respectively, immediately after treatment and by 1.2 and 1.8 log CFU/ml, respectively, following 6 days of storage at 4.4 °C. Evaluation of the resident microflora including aerobic plate counts (APC), E. coli, coliforms and psychrotrophs on uninoculated chicken carcasses after treatment with EPL300-ACS30 or LAE200-ACS30 and during storage indicated that these treatments have the potential to increase the shelf-life of poultry carcasses. Furthermore, application of warm (55 °C) EPL300-ACS30 or LAE200-ACS30 onto inoculated beef rounds reduced both ST and EC counts over 6 days of storage at 4.4 °C by 4.5 and 4.3 log CFU/cm2, respectively. Ground beef manufactured with EPL300-ACS30 or LAE200- ACS30 treated rounds had lower ST and EC counts initially and stayed lower over 4 days of storage at 4.4 °C when compared to control.

During the harvesting process, meat products can become contaminated with enteric pathogens, such as Escherichia coli O157:H7 and Salmonella Typhimurium. Surrogates for these pathogens would be beneficial for validating carcass decontamination treatments. Surrogate organisms are organisms that behave similarly to specific pathogens but are non-pathogenic and can be used to determine efficacy of decontamination regimes for pathogens. The surrogates proposed are non-pathogenic, ampicillin-resistant E. coli biotype I strains that were previously isolated from beef cattle hides. Each E. coli strain was transformed to express a fluorescent protein (red: EcRFP; green: EcGFP; yellow: EcYFP) that is detectable under an ultraviolet light source. Surface areas on hot boned beef carcasses (clod, brisket, outside round) were inoculated with a fecal slurry containing EcRFP, EcGFP, EcYFP and rifampicin-resistant E. coli O157:H7 and S. Typhimurium. Surface regions were then treated in a model spray cabinet using an initial water wash (28ºC) followed by treatments using 2% L-lactic acid (55ºC), hot water (95ºC at source) or a combination of the two. Treatments were compared for their effectiveness at reducing populations of inoculated (4.7 to 6.7 log CFU/cm2) E. coli, S. Typhimurium, EcRFP, EcGFP and EcYFP. Log reductions for inoculated organisms were calculated individually and then total and average surrogate cocktail values were calculated. All decontamination treatments reduced the inoculated numbers of pathogens and surrogates to near or below the detection limit of 0.5 log CFU/cm2. The combined treatment resulted in the greatest log reductions. The three individual surrogate organisms varied in log reductions according to the different decontamination treatments applied; however, log reductions for the total surrogate cocktail did not differ significantly from that of E. coli O157:H7. With the exception of EcYFP, the individual surrogates and average surrogate cocktail were significantly more resistant to microbial interventions including lactic acid than S. Typhimurium. Because abattoirs utilize different carcass decontamination treatments, it is difficult for one single fluorescent protein-producing isolate to accurately represent the behavior of E. coli O157:H7 or S. Typhimurium. Instead, surrogates should be used as a total cocktail to accurately represent the effectiveness of different treatments for reduction of enteric pathogens.

In this thesis, we consider the problem of decontaminating networks from black viruses (BVs) with a team of mobile agents, using parallel strategies. The BV is a harmful process whose initial location is unknown a priori. It destroys any agent arriving at the network site where it resides and, once triggered, it spreads to all the neighboring sites, creating copies of itself, thus increasing its presence in the network. To eliminate a virus present in a node, an agent has to move on that node; however, once the disinfection is performed, the agent is destroyed (i.e., it becomes inactive and cannot operate anymore). Existing literature has proposed sequential strategies that minimize the spread of the virus, such techniques are however quite inefficient in terms of time complexity. Instead of exploring the network sequentially, we propose to employ a group of agents that cooperate to follow a collective protocol to explore the network simultaneously. In this way, we dramatically reduce the decontamination time, still keeping the spread (and the number of agents loss) asymptotically optimal. In the thesis, various protocols are proposed in meshes, tori, and chordal rings following the monotonicity principle (i.e., once a node is disinfected we prevent it from being recontaminated). Finally, a solution is proposed also for the general case of the arbitrary topology. We analyze theoretically the cost of all our solutions for special topologies showing the advantages of our strategies with respect to the existing ones. In the case of the arbitrary topology, we conduct experimental analysis to assess the performance of our solution, confirming its efficiency. In all cases, our strategies significantly improve time while maintaining asymptotically optimal spread and agent losses.

Ethanol fermentation of highly concentrated aflatoxin-contaminated corn (Zea mays) was conducted on a lab scale to determine if aflatoxin concentrated in the distilled ethanol and/or dry distillers grain end-products. Alliquots of fermented mash, distilled ethanol, stillage, and dry distillers grain (DDG) were analyzed via LC-MS/MS and immunoassay detection methods for aflatoxin. Results indicate that aflatoxin does not greatly concentrate during fermentation in the DDGs and is undetectable in distilled ethanol. Addition of binders, MTB-100®, to aflatoxin-contaminated DDGs showed great reduction in aflatoxin concentrations when analyzed via LC-MS/MS. Also, an experiment investigating detoxification of aflatoxin using Clorox® was conducted. Results obtained from LC-MS/MS showed a positive correlation of decreased aflatoxin levels with increasing Clorox® levels following a logarithmic trend.