Thesis (doctoral)--Swedish University of Agricultural Sciences, 2001. / Thesis statement in Swedish and English abstract inserted. Based on 4 previously prepared or published papers reprinted here. Includes bibliographical references.

Thesis (Ph.D)--Industrial and Systems Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Kleywegt, Anton J.; Committee Member: Ayhan, Hayriye; Committee Member: Dai, Jim; Committee Member: Erera, Alan; Committee Member: Ward, Amy R. Part of the SMARTech Electronic Thesis and Dissertation Collection.

The intensification of freshwater aquaculture worldwide has facilitated the propagation of the parasitic ciliate protozoan Ichthyophthirius multifiliis Fouquet, 1876 commonly known as “fish white spot” or “Ich”. Ichthyophthirius multifiliis infections lead to high mortalities, generating significant economic losses in most cultured freshwater fish species worldwide. Until recently, malachite green was the chemical treatment traditionally used to control I. multifiliis infections. Its reclassification as carcinogenic to humans and its subsequent ban for use in food fish has left the industry without any suitable treatments. Currently, in-bath formaldehyde and sodium chloride treatments are the most common option used in farm systems to control I. multifliis infections. Given their low efficacy, however, they are not considered as sustainable long–term options. There is, therefore, an urgent necessity to find efficacious alternatives for controlling I. multifliis infections. The general aim of this research project was to improve the management of I. multifiliis infections in order to develop more comprehensive, environmentally friendly and sustainable therapeutic strategies for use in freshwater food fish aquaculture. The present PhD-thesis present first a literature review chapter providing an overview and critical assessment of chemotherapeutants and physical interventions tested within the last 30 years against I. multifiliis infections. The experimental worked consisted of a number of in vitro and in vivo trials were conducted using experimental scale flow-through, static tank systems and commercial scale raceways within a rainbow trout hatchery, in addition to molecular work on different isolates of the parasite. The results of this research are organised into three experimental chapters which describe the testing of chemical and non-chemical treatments against I. multifiliis infections and work undertaken to determine the most suitable molecular markers to identify I. multifiliis isolates. In the first experimental chapters, the possibility of efficiently controlling I. multifliis infections through the administration of novel environmentally-friendly chemical treatments (e.g. bronopol and peracetic acid-based products) was investigated. The results clearly showed that bronopol and peractic acid-based products have a strong biocidal/cytotoxic effect against all free-living stages of I. multifiliis (e.g. tomonts, cysts and theronts). The administration of high concentrations of bronopol (e.g. 20, 50 and 100 mg L-1) over short periods of exposure (e.g. 30 min) significantly reduced the survival of tomonts, cysts and theronts and delayed the development of I. multifiliis tomonts and cysts. Prolonged low concentrations of bronopol (e.g. 1 mg L-1) greatly reduced the survival of infective theronts, although such treatment did not affect the ability of surviving theronts to subsequently infect a host. When tested in vivo, the continuous prolonged exposure (e.g. 27 days) of low concentrations of bronopol (e.g. 2 and 5 mg L-1) had an impact on the population dynamics of I. multifiliis, this being demonstrated by a significant reduction in the number of trophonts developing within the fish. Low concentrations of bronopol (e.g. 2 mg L-1) administrated as a preventive treatment prior to infection also proved to be very successful at reducing the colonisation success of I. multifiliis. Peracetic acid administrated at low concentrations (e.g. 8, 12 and 15 mg L-1) over a short window of exposure (e.g. 1 h) displayed a strong biocidal effect against all the free-living stages of I. multifiliis (e.g. tomonts, cysts and theronts). The bronopol and peracetic acid-based products tested here both appear to be capable of disrupting the development of the cyst stage of I. multifiliis which is seldom reported for chemotherapeutants currently used against this parasite. These results suggest that bronopol and peracetic acid-based products have a place in the arsenal of treatment options for controlling I. multifiliis infections in commercial aquaculture systems. The use of a mechanical device or a biological control agent to remove the cyst stage of I. multifiliis and the impact of such control on the population dynamics and the levels of infection of fish were also investigated. The results revealed that tomonts preferentially settle and encyst on the base of culture systems and on biofilm–covered substrates. The survival of the tomont stage is greatly affected by the composition of the substrate upon which it settles and is significantly lower on polypropylene-based plastic. The lining of raceways in a commercial rainbow trout hatchery with a low-adhesion polymer created a smooth surface facilitating the dislodgement and elimination of the cyst stage of I. multifilis by natural flushing or brushing. The physical removal of the cyst stage alone, through the use of a mechanical device or substrate detrivorous/algae feeder as a biological control agent, significantly reduced the propagation of I. multifiliis to a low level of infection without the need to deploy an additional chemical treatment. These studies demonstrate that the cyst is a key stage in the dynamics of I. multifiliis infection and its removal from the fish culture systems could constitute an effective and simple mean of managing I. multifiliis infections. The third experimental chapter explores the utilisation of molecular marker to characterise different isolates of I. multifiliis. The results highlight the unsuitability of the rDNA region (ITS-1 and ITS-2) and the strong potential of the mtDNA (COI) as molecular markers to discriminate isolates of I. multifiliis from distant geographical locations. It is suggested that genetic “barcoding” using mtDNA is the most effective method to identify I. multifiliis isolates. Importantly, genetic “barcoding” could allow associating I. multifiliis strains or geographical isolates with particular properties as regards their ecophysiology, pathogenicity and sensitivity to treatment, in order to improve the management of I. multifiliis infections according to the specific genetic isolate encountered. This research project demonstrates the efficacy of a range of new approaches against the propagation of I. multifiliis. Together, our findings contribute towards the development of a more effective and integrated system for managing I. multifliis infections in farm systems. The utilisation of physical methods and of environmentally friendly chemotherapeutants holds great potential for the control of I. multifiliis infections in organic fish production and in a broader context to any freshwater food fish farms affected by I. multifiliis.

The popularity of Amazon's EC2 cloud platform has increased in commercial and scientific high-performance computing (HPC) applications domain in recent years. However, many HPC users consider dedicated high-performance clusters, typically found in large compute centers such as those in national laboratories, to be far superior to EC2 because of significant communication overhead of the latter. We find this view to be quite narrow and the proper metrics for comparing high-performance clusters to EC2 is turnaround time and cost. In this work, we first compare the HPC-grade EC2 cluster to top-of-the-line HPC clusters based on turnaround time and total cost of execution. When measuring turnaround time, we include expected queue wait time on HPC clusters. Our results show that although as expected, standard HPC clusters are superior in raw performance, they suffer from potentially significant queue wait times. We show that EC2 clusters may produce better turnaround times due to typically lower wait queue times. To estimate cost, we developed a pricing model---relative to EC2's node-hour prices---to set node-hour prices for (currently free) HPC clusters. We observe that the cost-effectiveness of running an application on a cluster depends on raw performance and application scalability. However, despite the potentially lower queue wait and turnaround times, the primary barrier to using clouds for many HPC users is the cost. Amazon EC2 provides a fixed-cost option (called on-demand) and a variable-cost, auction-based option (called the spot market). The spot market trades lower cost for potential interruptions that necessitate checkpointing; if the market price exceeds the bid price, a node is taken away from the user without warning. We explore techniques to maximize performance per dollar given a time constraint within which an application must complete. Specifically, we design and implement multiple techniques to reduce expected cost by exploiting redundancy in the EC2 spot market. We then design an adaptive algorithm that selects a scheduling algorithm and determines the bid price. We show that our adaptive algorithm executes programs up to 7x cheaper than using the on-demand market and up to 44% cheaper than the best non-redundant, spot-market algorithm. Finally, we extend our adaptive algorithm to exploit several opportunities for cost-savings on the EC2 spot market. First, we incorporate application scalability characteristics into our adaptive policy. We show that the adaptive algorithm informed with scalability characteristics of applications achieves up to 56% cost-savings compared to the expected cost for the base adaptive algorithm run at a fixed, user-defined scale. Second, we demonstrate potential for obtaining considerable free computation time on the spot market enabled by its hour-boundary pricing model.

The main purpose of this thesis is to improve the fundamental knowledge of non-isothermal tempering of martensite phase and its effects on the reduction in hardness (softening) with respect the base metal occurring at the heat affected zone (HAZ) of resistance spot welded dual-phase (DP) steels. This thesis also aims at understanding the influence of HAZ-softening on the joint performance of various DP steel grades. The tempering of martensite occurring at the sub-critical HAZ (SC-HAZ) of resistance spot welded DP600, DP780 and DP980 steels has been systematically evaluated by microhardness testing through Vickers indentation and the degree of tempering has been correlated to the HAZ-softening. From the joint performance analysis of similar and dissimilar steel grade combinations assessed through standardized testing methods, three important issues have been targeted: a) the joint strength (maximum load to failure), b) the location of failure (failure mode), and c) the physical characteristic of the weld that determines certain type of failure (weld nugget size). In addition, a partial tensile test has been conducted in order to evaluate the initiation of failure in dissimilar steel grade combinations. It has been shown that HAZ-softening lowered the weld size at which transition from interfacial to pullout failure mode takes place along with increased load-bearing capacity and higher energy absorption. Thus, it is concluded from mechanical testing that HAZ-softening benefits the lap-shear tensile joint performance of resistance spot welded DP steels by facilitating pullout failures through failure initiation at the SC-HAZ (tempered region). Instrumented nanoindentation testing was employed to further investigate HAZ-softening along the SC-HAZ by evaluating individual phases of ferrite matrix and tempered martensite islands. Although the ferrite matrix presented a slight reduction in hardness at nanoscale, higher reduction in hardness (softening) resulted for tempered martensite; thus confirming that tempered martensite is the major contributor to softening at micro-scale. A comparison between nanohardness and microhardness testing made at different distances from the line of lower critical temperature of transformation (Ac1) allowed revealing the actual extension of the SC-HAZ. In this regard, good correlation was obtained between nanohardness results along the SC-HAZ and the microstructural changes analyzed by electron microscopy (i.e., the tempering of martensite occurring at various distances far from Ac1 was correlated to low temperature tempering of dual phase steels). An in-depth analysis of the tempering of martensite phase at high temperature in DP steel subjected non-isothermal conditions i.e., rapid heating, extremely short time at peak temperature and rapid cooling (resistance spot welding), has been carried out mainly through analytical transmission electron microscopy (TEM). In addition, an isothermal tempering condition (i.e., slow heating and long time at peak temperature) in DP steel has been evaluated for complementing the analysis. Both non-isothermal and isothermal conditions have been correlated to the softening behaviour. TEM analysis of the base metal in the DP steel indicated that the morphology of the martensite phase is dependent on its carbon content, and its tempering characteristics are similar to that of equal carbon containing martensitic steel. The isothermally tempered structure is characterized by coarsening and spheroidization of cementite (θ) and complete recovery of the martensite laths; whereas precipitation of fine quasi-spherical intralath θ-carbides, coarser plate-like interlath θ-carbides, decomposition of retained austenite into elongated θ-carbides, and partial recovery of the lath structure were observed after non-isothermal tempering of DP steel. This difference in tempering behaviour is attributed to synergistic effect of delay in cementite precipitation due to higher heating rate, and insufficient time for diffusion of carbon that delays the third stage of tempering process (cementite coarsening and recrystalization) during non-isothermal. The finer size and the plate-like morphology of the precipitated carbides along with the partial recovery of the lath structure observed after non-isothermal tempering strongly influenced the softening behaviour of DP steel. The chemical analysis of θ-carbides through extraction replicas for three different DP steels revealed that the chemistry of the carbides is inherited from the parent DP steel during non-isothermal tempering at high temperature confirming that non-isothermal tempering DP steel is predominantly controlled by carbon diffusion.

The variable rate fertilizer spreader was modified to control each pair of nozzles for spot-application of fertilizer only in plant areas of wild blueberry fields. The experiments were conducted to evaluate performance accuracy of modified variable rate granular (MVRG) fertilizer spreader. The results suggested that the MVRG fertilizer spreader performed efficiently in detecting bare spots/weed patches and clay filler application only in green grass/plant areas. Two wild blueberry fields were selected to evaluate the impact of MVRG spreader on nutrient leaching through small bare spots/weed patches. Management zones were delineated on the basis of slope variability. The MVRG spreader significantly reduced the nutrient loading in subsurface water samples collected from the bare spots/weed patches. Based on the results obtained, it can be concluded that the fertilization in wild blueberry fields using MVRG fertilizer spreader can result in the protection of subsurface water quality, thus protecting the environment.

Over the past several decades, many techniques and approaches have been proposed and implemented for load and price forecasting. The objective of all of these methods was load and price forecasting with minimal error. However, researchers face several challenges in achieving this goal. For price forecasting, the main challenge is to forecast electricity prices accurately in a deregulated electric power market with volatile aspects. Decentralized or deregulated markets are very volatile systems. Hence, pattern following and accurate forecasting of electricity prices are difficult tasks using ordinary methods. In this thesis, a novel approach is introduced and implemented to overcome the challenges inherent in accurate price forecasting. This novel approach involves innovations in forecasting to improve the spot power price forecasting accuracy in a competitive market. To investigate the applicability and effectiveness of this technique, Multiple Linear Regression (MLR) and Artificial Neural Networks (ANN), two well-known forecasting techniques, are developed.

An automated prototype variable rate (VR) sprayer was developed for control of eight individual nozzles on a 6.1 m sprayer boom for spot-application (SA) of agrochemicals in wild blueberry fields. The VR control system consisted of eight ultrasonic sensors and four cameras mounted on a separate boom in front of the ATV, flow controller, VR controller, ruggedized computer, flow valve and solenoid valves. Custom software was capable of processing the images to detect weeds or plants in real-time and automatically send a signal to the VR controller for SA at the correct target. The performance of VR sprayer for SA on weeds (herbicide) and foliage (fungicide) was evaluated in commercial wild blueberry fields. Based on the results of this study, the VR sprayer was reliable, efficient and accurate enough for SA of agrochemicals. The average volume of chemical saved with SA was 70 % herbicide and 30 % fungicide.

Soil application of a known activator of Systemic Acquired Resistance (SAR), benzo(1,2,3)thiadiazole-7-carbothioic acid-S-methyl ester (BTH), and Harmonizer, a polychlorinated copper (II) phthalocyanine pigment, reduced severity of Colletotrichum orbiculare in Nicotiana benthamiana by 99% and 38%, respectively. BTH induced expression of nine SAR/progammed cell death-related genes and primed expression of two Induced Systemic Resistance (ISR)-related genes, while Harmonizer induced expression of only one SAR-related gene. Soil application of Harmonizer also reduced severity of Sclerotinia homoeocarpa in Agrostis stolonifera up to 39%, whereas BTH was ineffective. Next generation sequencing identified over 1000 genes in A. stolonifera with two-fold or higher increased expression following Harmonizer treatment relative to a water control, and induced expression of three defense-related genes was confirmed by relative RT-PCR. These results demonstrate that Harmonizer can activate systemic resistance in a dicot and a monocot, but changes in expression of genes indicated that it differed from BTH-activated SAR. / Petro-Canada, Natural Sciences and Engineering Research Council of Canada, Ontario Turfgrass Research Foundation

The ubiquitous second messenger cAMP acts to integrate and translate information encoded by extracellular messenger molecules, including hormones and neurotransmitters. Intracellular cAMP concentrations are regulated through coordinated changes in the activities of adenylyl cyclases (ACs) and cyclic nucleotide phosphodiesterases (PDEs). Freely diffusing cAMP can reach concentrations sufficient to activate cAMP effector proteins, such as protein kinase A (PKA) or the exchange protein activated by cAMP (EPAC), except in defined compartments where PDEs are localized which allows for spatial and temporal control of the cAMP signal. In human aortic vascular endothelial cells (HAECs) and HEK293T cells we recently identified a macromolecular complex consisting of PDE3B and EPAC and showed that this complex coordinated cAMP-induced effects on adhesion of these cells to fibronectin-coated surfaces. Using “pull-down” assays and peptide array-based approaches we have identified the molecular determinants which coordinate the formation of this complex. Our evidence suggests that the extreme N-terminal 13 amino acids of PDE3B represent the portion of PDE3B that interacts with EPAC. In addition, although several EPAC-encoded peptides were shown to bind PDE3B, immunoprecipitation-based studies identified a region proximal to the cAMP-binding domains as likely to have a dominant role in this binding. Of functional relevance, a cell permeable peptide containing these amino-terminal 13 amino acids of PDE3B antagonizes PDE3B-EPAC interactions in cells. In addition, this peptide impacted the ability of cAMP-elevating agents to coordinate EPAC-dependent cell adhesions. / Thesis (Master, Pathology & Molecular Medicine) -- Queen's University, 2009-10-06 19:07:12.01