Analytical modelling of bacterial migration and accumulation with rate-limited sorption in discrete fractures

An analytical model for bacterial accumulation in a discrete fractllre has been developed. The transport and accumlllation processes incorporate into the model include advection, dispersion, rate-limited adsorption, rate-limited desorption, irreversible adsorption, attachment, detachment, growth and first order decay botl1 in sorbed and aqueous phases. An analytical solution in Laplace space is derived and nlln1erically inverted. The model is implemented in the code BIOFRAC vvhich is written in Fortran 99. The model is derived for two phases, Phase I, where adsorption-desorption are dominant, and Phase II, where attachment-detachment are dominant. Phase I ends yvhen enollgh bacteria to fully cover the substratllm have accllillulated. The model for Phase I vvas verified by comparing to the Ogata-Banks solution and the model for Phase II was verified by comparing to a nonHomogenous version of the Ogata-Banks solution. After verification, a sensitiv"ity analysis on the inpllt parameters was performed. The sensitivity analysis was condllcted by varying one inpllt parameter vvhile all others were fixed and observing the impact on the shape of the clirve describing bacterial concentration verSllS time. Increasing fracture apertllre allovvs more transport and thus more accllffilliation, "Vvhich diminishes the dllration of Phase I. The larger the bacteria size, the faster the sllbstratum will be covered. Increasing adsorption rate, was observed to increase the dllration of Phase I. Contrary to the aSSllmption ofllniform biofilm thickness, the accllffilliation starts frOll1 the inlet, and the bacterial concentration in aqlleous phase moving towards the olitiet declines, sloyving the accumulation at the outlet. Increasing the desorption rate, redllces the dliration of Phase I, speeding IIp the accllmlilation. It was also observed that Phase II is of longer duration than Phase I. Increasing the attachment rate lengthens the accliffililation period. High rates of detachment speeds up the transport. The grovvth and decay rates have no significant effect on transport, althollgh increases the concentrations in both aqueous and sorbed phases are observed. Irreversible adsorption can stop accllillulation completely if the vallIes are high.

An educator's perspective of Dr. Feingold's K-P (Kaiser- Permanents) elimination diet for hyperkinetic children and others

Do evaluation of the literature and a regional observational report support Dr. Feingold's claim that the K-P (Kaiser-Permanente) elimination diet improves the behaviours of hyperkinetic children, and others? Dr. Feingold suggests that some hyperkinetic children, and other children as well, are genetically predisposed to intolerance of food additives, particularly food colours and flavours. He claims that the K-P diet, that eliminates salicylates and artificial food colours and flavours, improves the hyperkinetic child's behaviour, muscle co-ordination, and scholastic performance. Public acceptance of the K-P diet has outstripped acceptance in the medical and scientific communities. Evaluation of available data and additional studies are needed to arrive at a conclusion of acceptance or rejection of the K-P diet for hyperkinetic children and others. My interest in the K-P elimination diet for hyperkinetic children is educational. My experience as an elementary school teacher in special education and in the classroom from K-8 has taught me that attentiveness is crucial to learning. Hyperkinesis appears to impair a child's ability to attend. Learning problems appear, followed by behavioural and social problems. l If we accept the possibility of a relationship between diet and attentiveness, and attentiveness and school behaviours, then the diet-behaviour link could be of lay importance. For instance, if a diet such as the K-P diet could do what is claimed, substantial benefits could accrue to the child. One could, for example, improve a child's behaviours. One could identify attending disturbances early in the child's education, possibly minimizing, or eliminating future difficulties in school. Finally, the greatest benefit may be the fulfillment of the basic goal of our Ontario schools, that the eh~ld-,lIla1p.evelop happily and competently within our educational framework. 2 This thesis reports evidence from the literature and from a regional observational investigation to determine the possibility of a link between the behaviours of children and Dr. Feingold's K-P elimination diet. The literature research examines (1) Dr. Feingold's concept of H-LD, (2) his K-P elimination diet, and (3) the response from three sectors, medicine, science, and the public. The regional investigation examines the observed behaviours of nine children in Regional Niagara during a nine-month period on the K-P diet.

Synthesis of nanoporous materials for preconcentration and determination of trace elements by ICP-AES ; Investigation and elimination of the memory effects of mercury, gold, silver and boron in ICP-AES

Nanoporous materials with large surface area and well-ordered pore structure have been synthesized. Thiol groups were grafted on the materials' surface to make heavy metal ion pre-concentration media. The adsorption properties ofthe materials were explored. Mercury, gold and silver can be strongly adsorbed by these materials, even in the presence of alkaline earth metal ion. Though the materials can adsorb other heavy metal ions such as lead and copper, they show differential adsorption ability when several ions are present in solution. The adsorption sequence is: mercury> == silver> copper » lead and cadmium. In the second part of this work, the memory effects of mercury, gold, silver and boron were investigated. The addition of 2% L-cysteine and 1% thiourea eliminates the problems of the three metal ions completely. The wash-out time for mercury dropped from more than 20 minutes to 18 seconds, and the wash-out time for gold decreased from more than 30 minutes to 49 seconds. The memory effect of boron can be reduced by the use of mannitol.

Bacteriophages of Erwinia amylovora and their potential use in biological control

Forty-four bacteriophage isolates of Erwinia amy/ovora, the causal agent of fire blight, were collected from sites in and around the Niagara Region of Southern Ontario in the summer of 1998. Phages were isolated only from sites where fire blight was present. Thirty-seven of these phages were isolated from the soil surrounding infected trees, with the remainder isolated from aerial plant tissue samples. A mixture of six E. amy/ovora bacterial host strains was used to enrich field samples in order to avoid the selection bias of a single-host system. Molecular characterization of the phages with a combination of peR and restriction endonuclease digestions showed that six distinct phage types were isolated. Ten phage isolates related to the previously characterized E. amy/ovora phage PEa1 were isolated, with some divergence of molecular markers between phages isolated from different sites. The host ranges of the phages revealed that certain types were unable to efficiently lyse some E. amy/ovora strains, and that some types were able to lyse the epiphytic bacterium Pantoea agg/omerans. Biological control of E. amy/ovora by the bacteriophages was assessed in a bioassay using discs of immature pear fruit. Twenty-three phage isolates were able to significantly suppress the incidence of bacterial exudate on the pear disc surface. Quantification of the bacterial population remaining on the disc surface indicated that population reductions of up to 97% were obtainable by phage treatment, but that elimination of bacteria from the surface was not possible with this model system.

X-ray diffraction of a gram-negative bacterial membrane mimetic

This thesis applies x-ray diffraction to measure he membrane structure of lipopolysaccharides and to develop a better model of a LPS bacterial melilbrane that can be used for biophysical research on antibiotics that attack cell membranes. \iVe ha'e Inodified the Physics department x-ray machine for use 3.'3 a thin film diffractometer, and have lesigned a new temperature and relative humidity controlled sample cell.\Ve tested the sample eel: by measuring the one-dimensional electron density profiles of bilayers of pope with 0%, 1%, 1G :VcJ, and 100% by weight lipo-polysaccharide from Pse'udo'lTwna aeTuginosa. Background VVe now know that traditional p,ntibiotics ,I,re losing their effectiveness against ever-evolving bacteria. This is because traditional antibiotic: work against specific targets within the bacterial cell, and with genetic mutations over time, themtibiotic no longer works. One possible solution are antimicrobial peptides. These are short proteins that are part of the immune systems of many animals, and some of them attack bacteria directly at the membrane of the cell, causing the bacterium to rupture and die. Since the membranes of most bacteria share common structural features, and these featuret, are unlikely to evolve very much, these peptides should effectively kill many types of bacteria wi Lhout much evolved resistance. But why do these peptides kill bacterial cel: '3 , but not the cells of the host animal? For gramnegative bacteria, the most likely reason is that t Ileir outer membrane is made of lipopolysaccharides (LPS), which is very different from an animal :;ell membrane. Up to now, what we knovv about how these peptides work was likely done with r !10spholipid models of animal cell membranes, and not with the more complex lipopolysa,echaricies, If we want to make better pepticies, ones that we can use to fight all types of infection, we need a more accurate molecular picture of how they \vork. This will hopefully be one step forward to the ( esign of better treatments for bacterial infections.