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Aeromonas spp. isolates, which are fish and opportunistic human pathogens, form biofilms, however the factors involved in and affecting biofilm formation have not been fully elucidated. Biofilm formation is affected by motility, cell surface characteristics, and/or metabolism, thus it is important to identify factors potentially contributing to initial attachment and/or biofilm formation and their correlation with biofilm formation by Aeromonas spp. isolates. With knowledge of the stages of biofilm formation, mechanisms involved in biofilm formation and its physiology, various strategies may be applied to control aeromonad biofilms. Factors potentially involved in initial attachment and/or biofilm formation were investigated for 99 Aeromonas isolates obtained from seawater and cultured fish. Aeromonad biofilm formation was assessed using microtiter plate assays under varying physicochemical conditions. The disk diffusion method was used to determine the antimicrobial susceptibility profiles of isolates, for comparison to clinical and aquaculture isolates reported in other studies. The MICs and MBICs for antimicrobial agents (azithromycin, ceftazidime, ciprofloxacin, gentamicin and tetracycline) of planktonic cells and biofilm cells, respectively, were investigated using the broth microdilution and modified microtiter plate assays. The effect of sub-MIC (0.5 × MIC) and supra-MIC (2 × MIC) exposures on biofilm-forming cells was also determined using microtiter plate assays. The presence of efflux pump-mediated resistance in 45 Aeromonas spp. isolates was determined using the disk diffusion assay incorporating efflux pump inhibitors (EPIs) [carbonyl cyanide 3-chlorophenylhydrazone (CCCP), phenylalanine arginine β-naphthylamide (PAβN) and 1-(1-naphthylmethyl)-piperazine (NMP)]. Modified microtite plate assays were used to determine the effect of EPIs [CCCP, PAβN, and NMP], matrix-degrading DNase I and quorum-sensing inhibitors (QSIs; vanillin, 2(5H)-furanone, S-adenosylhomocysteine and cinnamaldehyde) on initial attachment and mature biofilm. Majority of isolates were motile by swimming and swarming and displayed caseinase, gelatinase, and DNase activities, as well as an A-layer phenotype. Majority of isolates displayed high levels of autoaggregation and were hydrophilic. Isolates showed varying levels of adherence, but majority were strongly adherent in nutrient-rich media at 30 ºC. Motility appeared to be a significant characteristic for biofilm formation. Majority of Aeromonas isolates spp. showed high levels of resistance to β-lactams, trimethoprim and sulphamethoxazole, and were susceptible to augmentin, piperacillin-tazobactam, aztreonam, 2nd and 3rd generation cephalosporins, carbapenems, macrolides, fluoroquinolones and aminoglycosides . High levels of resistance towards ceftazidime (MIC > 32 μg/ml) were observed for isolates, while levels of resistance towards remaining antimicrobial agents tested (tetracycline, azithromycin, ciprofloxacin, and gentamicin) were ≤ 32 μg/ml. There was a ≥16-fold increase in MBICs (4096 μg/ml) compared to the MICs for all the antimicrobial agents. The sub-MIC, MIC, and supra-MIC exposures of all antimicrobial agents had an inhibitory effect on both initial attachment and pre-formed biofilms by Aeromonas spp. isolates. Majority of isolates were more susceptible to tetracycline, norfloxacin, and azithromycin due to CCCP and NMP inhibition of the efflux pumps eliminating these antimicrobial agents. Susceptibility to erythromycin was observed for 51% and 47% of isolates, respectively, due to NMP and PAβN inhibition of the efflux pump/s eliminating erythromycin. In the microtiter plate assays, CCCP, NMP and PABN exposures resulted in significant reduction of biofilm formation by majority of Aeromonas spp. isolates in both initial attachment and mature biofilm assays, with CCCP being more effective. DNase I was more effective in reducing mature biofilm, causing reduction for 60% of isolates, compared to its effect on initial attachment. QSIs were also more effective in reducing mature biofilm compared to inhibiting initial attachment. Although increased biofilm dispersal was observed with all QSIs, vanillin and 2(5H)-furanone were more effective compared to S-adenosylhomocysteine and cinnamaldehyde. Based on data obtained in this study, antimicrobial agents, EPIs and QSIs can be used as potential biofilm-inhibiting compounds in aquaculture to control aeromonad infections and may not only prevent disease outbreaks but they could also increase the effectiveness of existing therapeutic agents. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2012.

This study explores the relationships that emerge between socioeconomic status (SES) and the prevalence of several health outcomes in children of different ages utilizing administrative data housed at The Manitoba Centre for Health Policy (MCHP). This research also determines the effect that family has on a child developing (or not developing) a specific health outcome. Finally, the relationship between prevalence and familial aggregation are examined. The Johns Hopkins ACG(r) Case-Mix System grouped various physician and hospital diagnosis codes into 32 Aggregated Diagnostic Groups (ADGs). Eight of these ADGs were assessed at four age groups (0-3, 4-8, 9-13 & 14-18) for each member of the final study population. Each member was assigned to one of six SES groups, five income quintile groups and one social assistance group. Familial aggregation was determined for eight selected ADGs using an intraclass correlation coefficient (ICC). Statistical contrasts were made for SA vs. Q1-Q5 and an overall linear trend (SA – lowest; Q5 – highest) to establish the SES differences for the prevalence and familial aggregation of a particular condition. Many of the conditions across SES had statistically significant (p<0.05) linear and SA vs. Q1-Q5 contrasts for 3 both ICCs and prevalence at all age groups. Of the eight ADGs that familial aggregation was calculated, chronic conditions related to the eye had the highest ICCs at all age groups. Injury ADGs had consistently lower ICCs for all age groups. Factors that affected the results of ICC estimation for binary outcomes include the number of bootstrap selections, the width of the age group and the event rate for the outcome of interest. Suggested future research includes a validity review of ICC estimates for binary outcomes, exploring the variables that may reduce or eliminate the SES gradient for ICCs and exploring the aggregation for different study samples within Manitoba.

Electrical bioimpedance was used to detect local volume and aggregation changes in blood. This was done with two separate experimentation processes to improve upon current research methods. Abdominal internal hemorrhaging is bleeding and pooling of blood within the abdominal cavity which can put the welfare of the patient at risk and may cause organ failure. Electrical bioimpedance is the response of biological tissue to applied electrical current. In cooperation with Bioparhom, electrical bioimpedance was used as a detection device for abdominal internal hemorrhaging. It is hypothesized that electrical bioimpedance could be a non-invasive and cost effective avenue for the detection of internal bleeding. In this study we investigate the use of electrical bioimpedance with a custom 8x8 needle electrode array, for detecting and locating the blood pooling due to a drop in resistivity in a rat using a Z-Metrix (function generator by Bioparhom). 5 and 95 kHz signals were inputted into a dead rat experiencing internal bleeding of porcine blood at a rate of 3.33 ml/min to 10 ml. For 8 rats, the 5 kHz frequency was found to be more sensitive to internal blood pooling. Red blood cell aggregation is a physiological process where red blood cells form reversible aggregates. RBC aggregation is an important indicator for physicians for the health of the circulatory system. Utilizing electrical bioimpedance, it is hypothesized that a reactance change as a result of blood aggregation will be detected. As well, a method is developed using impedance spectroscopy to determine s frequency which exhibits the highest reactance change during blood aggregation. This sensitive frequency, found to be 304 kHz, is compared to a frequency used by previous studies (100 kHz) to validate its. Using the Z-Metrix (function generator by Bioparhom) with a custom 4 electrode configuration, 2 ml of porcine blood mixed with 2 mg/ml of EDTA is tested for 2 minutes at a single frequency. The 304 kHz is found to be the most sensitive of the frequencies tested to reactance changes during aggregation. Results found for blood samples give an average AIc of 27.32 ± 11.44, which is within the physiological range for porcine blood of 3-30. It is seen that the 304 kHz has a higher precision than the 100 kHz frequency, but the AIc is within the same magnitude. As a result, 304 kHz is found to be a more favorable frequency than the previously published 100 kHz for the trials performed based on precision of the results and the sensitivity of the reactance change to blood aggregation.

This study explores the relationships that emerge between socioeconomic status (SES) and the prevalence of several health outcomes in children of different ages utilizing administrative data housed at The Manitoba Centre for Health Policy (MCHP). This research also determines the effect that family has on a child developing (or not developing) a specific health outcome. Finally, the relationship between prevalence and familial aggregation are examined. The Johns Hopkins ACG(r) Case-Mix System grouped various physician and hospital diagnosis codes into 32 Aggregated Diagnostic Groups (ADGs). Eight of these ADGs were assessed at four age groups (0-3, 4-8, 9-13 & 14-18) for each member of the final study population. Each member was assigned to one of six SES groups, five income quintile groups and one social assistance group. Familial aggregation was determined for eight selected ADGs using an intraclass correlation coefficient (ICC). Statistical contrasts were made for SA vs. Q1-Q5 and an overall linear trend (SA – lowest; Q5 – highest) to establish the SES differences for the prevalence and familial aggregation of a particular condition. Many of the conditions across SES had statistically significant (p<0.05) linear and SA vs. Q1-Q5 contrasts for 3 both ICCs and prevalence at all age groups. Of the eight ADGs that familial aggregation was calculated, chronic conditions related to the eye had the highest ICCs at all age groups. Injury ADGs had consistently lower ICCs for all age groups. Factors that affected the results of ICC estimation for binary outcomes include the number of bootstrap selections, the width of the age group and the event rate for the outcome of interest. Suggested future research includes a validity review of ICC estimates for binary outcomes, exploring the variables that may reduce or eliminate the SES gradient for ICCs and exploring the aggregation for different study samples within Manitoba.

Most existing data mining approaches perform data mining tasks on a single data table. However, increasingly, data repositories such as financial data and medical records, amongst others, are stored in relational databases. The inability of applying traditional data mining techniques directly on such relational database thus poses a serious challenge. To address this issue, a number of researchers convert a relational database into one or more flat files and then apply traditional data mining algorithms. The above-mentioned process of transforming a relational database into one or more flat files usually involves aggregation. Aggregation functions such as maximum, minimum, average, standard deviation, count and sum are commonly used in such a flattening process. Our research aims to address the following question: Is there a link between aggregation and possible privacy violations during relational database mining? In this research we investigate how, and if, applying aggregation functions will affect the privacy of a relational database, during supervised learning, or classification, where the target concept is known. To this end, we introduce the PBIRD (Privacy Breach Investigation in Relational Databases) methodology. The PBIRD methodology combines multi-view learning with feature selection, to discover the potentially dangerous sets of features as hidden within a database. Our approach creates a number of views, which consist of subsets of the data, with and without aggregation. Then, by identifying and investigating the set of selected features in each view, potential privacy breaches are detected. In this way, our PBIRD algorithm is able to discover those features that are correlated with the classification target that may also lead to revealing of sensitive information in the database. Our experimental results show that aggregation functions do, indeed, change the correlation between attributes and the classification target. We show that with aggregation, we obtain a set of features which can be accurately linked to the classification target and used to predict (with high accuracy) the confidential information. On the other hand, the results show that, without aggregation we obtain another different set of potentially harmful features. By identifying the complete set of potentially dangerous attributes, the PBIRD methodology provides a solution where the database designers/owners can be warned, to subsequently perform necessary adjustments to protect the privacy of the relational database. In our research, we also perform a comparative study to investigate the impact of aggregation on the classification accuracy and on the time required to build the models. Our results suggest that in the case where a database consists only of categorical data, aggregation should especially be used with caution. This is due to the fact that aggregation causes a decrease in overall accuracies of the resulting models. When the database contains mixed attributes, the results show that the accuracies without aggregation and with aggregation are comparable. However, even in such scenarios, schemas without aggregation tend to slightly outperform. With regard to the impact of aggregation on the model building time, the results show that, in general, the models constructed with aggregation require shorter building time. However, when the database is small and consists of nominal attributes with high cardinality, aggregation causes a slower model building time.

Web services is a relatively recent initiative that aims to promote program-toprogram interaction across the Internet, but while web services is based on a set of XML standards, new standards continue to emerge and existing standards to evolve. Also, web services relies on Remote Procedure Call (RPC) for communication and is thus influenced by the semantics of RPC. In this research, we investigated the juxtaposition of RPC with Generative Communications (GC). GC is a communication paradigm where messages exist independently of the sender and receiver and are stored in a network accessible buffer called a &quotspace": this leads to interactions which are inherently decoupled (in time and space). Also, messages are addressed to recipients by their content, rather than by network addresses, opening up the possibility for one-to-many interactions. These aspects are a marked departure from the RPC paradigm and introduce two main implications: 1) GC messages can be intercepted when in-transit between participants thus introducing the opportunity for mediation and 2) GC can be used as the basis for the aggregation of simple services into more complex ensembles. In this research, we explored these possibilities by creating proof-of-concept prototypes in three areas. 1) Mediation - GC based mediation was used to intercede between clients and services to allow a client using one protocol to interact with a service using a different protocol. For example, a GC based client interacting with a SOAP service (leading to backward compatibility). 2) Location services - a location service is a GC based service that performs a similar function to a UDDI registry but can be treated as just another service rather than part of an architecture. 3) Aggregation - a workflow design was used as the basis of an aggregated service using GC as the means by which the aggregation elements interact. We concluded that GC provides a natural platform for mediation, location services and aggregation and that these aspects could be combined to produce a holistic service environment.

The aggregation of misfolded proteins into amyloid fibrils is implicated in the pathogenesis of several human degenerative diseases, including Alzheimer’s, Parkinson’s and Type II diabetes. Links between the deposition of amyloid fibrils and the progression of these diseases are poorly understood, with much of the current research focused on monomer misfolding and subsequent assembly of oligomers and mature fibrils. This project examines the formation of human apolipoprotein (apo) C-II amyloid fibrils, with a focus on the stability and reversibility of amyloid fibril assembly. / The initial stages of the project were to develop a model for apoC-II amyloid fibril formation. This was achieved by analysis of the concentration dependent kinetics of apoC-II amyloid fibril formation, and correlation of these data with the final size distribution of the fibrils, determined by sedimentation velocity experiments. On the basis of these studies, a new reversible model for apoC-II amyloid fibril formation is proposed that includes fibril breaking and re-joining as integral parts of the assembly mechanism. The model was tested by rigorous experimentation, with antibody-labelling transmission electron microscopy providing direct evidence for spontaneous fibril breaking and re-joining. / The development of this model for apoC-II fibril assembly provided the foundation for experiments to investigate factors that promote, inhibit or reverse amyloid fibril formation. Factors that were considered include a molecular chaperone protein, αB-crystallin, and a chemical modification, methionine oxidation. Investigations on the effect of αB-crystallin revealed that the inhibition of apoC-II fibril formation occurs by two distinct mechanisms: transient interaction with monomer preventing oligomerisation, and binding to mature fibrils, which inhibits fibril elongation. Studies on the effect of methionine oxidation on apoC-II fibril formation showed that both the assembly and stability of the fibrils was affected by this modification. ApoC-II contains two methionine residues (Met-9 and Met-60), and upon oxidation of these residues fibril formation was inhibited. In addition, the treatment of pre-formed fibrils with hydrogen peroxide caused dissociation of the fibrils via the oxidation of Met-60, located with the fibril core structural region. The final chapter details the development of antibodies that specifically recognise the conformation of apoC-II amyloid fibrils, which provide the foundation for future studies to examine the role that apoC-II amyloid fibrils play in disease. / Overall, this thesis reveals the dynamic and reversible nature of amyloid fibril formation. New insight is also obtained of the general stability of amyloid fibrils and the processes that may regulate their formation, persistence and disease pathogenesis in vivo.

Gorse, Ulex europaeus, is a serious weed of agriculture and forestry in New Zealand. The mite Tetranychus lintearius feeds on gorse in Europe and was released in New Zealand during autumn 1989 as a potential biological control agent. The aim of my laboratory study was to increase available knowledge on its development and aggregation. As the quality of gorse declined as a food resource (as indicated by chlorophyll content) a significant decline in egg production, and an increase in development time of mites was found. Mean egg production at 15℃ ranged from 37.8 to 45.2 eggs/female over 10 days in the experimental treatments and development time from 39.2 to 43.3 days. Density of adult female mites (1, 2, 5, 10, 15, 20/spine) also had a significant effect on the number of eggs produced/female over ten days (mean daily egg production/female, 0.78-0.88). Mean development time from egg to adult decreased from 40.6 to 39 days as density increased from 1 to 50 mites/spine. The resident New Zealand strain of T lintearius, imported originally from Cornwall, is now widely established but has not established successfully on the west coast of the South Island or in the north of the North Island. Four new strains recently introduced from coastal Portugal and Spain, areas climatically similar to these New Zealand regions, may be more successful. Thus, although egg production and survival of all strains were significantly reduced when subjected to daily periods of simulated rainfall in laboratory experiments, those of the newly introduced strains were least affected. Laboratory experiments with the resident New Zealand and Cambados strains also showed that individuals aggregated actively at 10-20℃, but the latter aggregated more strongly at these temperatures. This strong aggregation behaviour may increase survival in warm, wet climates and suggests that Cambados strain mites could become established and so increase gorse control in Westland and Northland.

2003--Zugl.: Diss., 2003. / Zsfassung in dt. Sprache.