Dissipative spots are found in physical experiments of many branches of natural science. In this thesis we use three-component reaction-diffusion systems on two-dimensional domains in order to generate these patterns. Using a dynamical system approach we proceed with a Fourier analysis on a linearized reaction-diffusion system in order to provide the bifurcation conditions for a given homogeneous state. We validate our results and establish it's limitations through numerical experiments. We report very interesting behavior during these simulations, notably hysteresis and multi-stability. We will then turn our attention to the relatively unexplored phenomenon of rotating spots. Based on previous work done for spiral waves, we investigate the effect of translational symmetry-breaking on a rotating spot mainly through careful numerical analysis.

Infrastructure-as-a-Service cloud platforms are incredibly complex: they rent hundreds of different types of servers across multiple geographical regions under a wide range of contract types that offer varying tradeoffs between risk and cost. Unfortunately, the internal dynamics of cloud platforms are opaque in several dimensions. For example, while the risk of servers not being available when requested is critical in optimizing these risk-cost tradeoffs, it is not typically made visible to users. Thus, inspired by prior work on Internet bandwidth probing, we propose actively probing cloud platforms to explicitly learn such information, where each "probe'' is a request for a particular type of server. We model the relationships between different contracts types to develop a market-based probing policy, which leverages the insight that real-time prices in cloud spot markets loosely correlate with the supply (and availability) of fixed-price on-demand servers. That is, the higher the spot price for a server, the more likely the corresponding fixed-price on-demand server is not available. We incorporate market-based probing into SpotLight, an information service that enables cloud applications to query this and other data, and use it to monitor the availability of more than 4500 distinct server types across 9 geographical regions in Amazon's Elastic Compute Cloud over a 3 month period. We analyze this data to reveal interesting observations about the platform's internal dynamics. We then show how SpotLight enables two recently proposed derivative cloud services to select a better mix of servers to host applications, which improves their availability from 70-90% to near 100% in practice.

This paper is predicated on determining the effectiveness of angles-only initial orbit determination (IOD) methods when limited observational data is available for low-Earth orbit (LEO) rocket body debris. The analysis will be conducted with data obtained from Lockheed Martin Space’s Space Object Tracking (SpOT) facility, focusing on their observational data from 2018 that contains tracking of rocket body debris for less than one minute per overhead pass. After the IOD accuracies are better understood, a feasibility study will follow that investigates the possibility of cataloguing LEO orbital debris from a single optical observation facility with similar observational capabilities as that of the SpOT facility. The IOD accuracy analysis will investigate nine different rocket bodies, with a total of 50 orbital passes of data included in the research. Three main IOD approaches will be tested for each data set to determine the best method in achieving high levels of IOD accuracy: a traditional three-point method, an iterative method, and an assumed-circular orbit method. Application of the iterative approach results in increased accuracy for the resultant initial orbit determination as compared to the three-point IOD method, and an assumed-circular orbit assumption allows for a further increase in accuracy, especially for observed objects in near-circular orbits. The feasibility of cataloguing debris from a singular optical facility shows promise, as subsequent target acquisition after an object’s initial observation is determined to be achievable under the correct circumstances. By choosing a correct telescope pointing angle based on the IOD results from one pass of data, an observed rocket body debris object would pass through the field of view of SpOT’s spotter scope (0.7-degrees) during its next overhead pass for two different test cases. An increase field of view would increase both the likelihood of acquiring the target object and the amount of time the object is visible by the telescope.

Upon sensing pathogens, plants initiating defense responses typically resulting in programmed cell death (PCD). PCD effectively subdues biotrophic pathogens but is hijacked by necrotrophs that colonize the resulting dead tissues. We showed that barley wall associated kinase (WAK) genes, underlying the rcs5 QTL, are manipulated by the necrotrophic fungal pathogen Bipolaris sorokiniana to cause spot blotch disease. The rcs5 genetic interval was delimited to ~0.23 cM, representing an ~234 kb genomic region containing four WAK genes, designated HvWak2, Sbs1, Sbs2, and HvWak5. Post-transcriptional gene silencing of Sbs1&2 in the susceptible barley cultivars Steptoe and Harrington resulted in resistance, suggesting a dominant susceptibility function. Sbs1&2 expression is undetectable in barley prior to pathogen challenge; however, specific upregulation of Sbs1&2 occurred in the susceptible lines post inoculation. Promotor sequence polymorphisms were identified in the allele analysis of Sbs1&2 from eight resistant and two susceptible barley lines, which supported the possible role of promotor regulation by virulent isolates contributing to susceptibility. Apoplastic wash fluids from virulent isolates induced Sbs1expression, suggesting regulation by an apoplastic-secreted effector. Thus, the Sbs1&2 genes are the first susceptibility/resistance genes that confer resistance against spot blotch, a disease that threatens barley and wheat production worldwide. The nec3 mutants of barley are hyper-susceptible to many necrotrophs and show distinctive cream to orange necrotic lesions that are induced by infection, representing aberrant PCD. The γ- irradiation induced necrotic mutant, nec3-γ1 (Bowman) was confirmed as a nec3 mutant by allelism tests. The F2 progeny of a cross of nec3 x Quest inoculated with B. sorokiniana segregated as a single recessive gene fitting a 3 WT: 1 mutant ratio. The homozygous F2 mutant progeny were genotyped with four SSR and 25 SNP markers at nec3 locus on chromosome 6H, a physical region spanning ~ 16.96 Mb containing 91 high and low confidence annotated genes. Exome capture sequencing of nec3 mutants failed to identify a candidate gene, however, RNAseq analysis identified two candidates in the nec3 region with >three-fold downregulation. We hypothesize that the underlying aberrant PCD mechanism in the nec3 barley mutant facilitates extreme susceptibility to multiple adapted fungal pathogens of barley.

Please read the Summary and Conclusions(04chapter4) on pages 141-143 / Thesis (DSc (Agriculture))--University of Pretoria, 1963. / Microbiology and Plant Pathology / unrestricted

Cercospora leaf spot (CLS), caused by the fungal pathogen Cercospora beticola, is one of the most destructive foliar diseases on sugar beet. It severely affects productivity and profitability of the sugar beet industry. CLS is managed by using resistant cultivars, rotating with non-host crops, and applying effective fungicides in a timely manner. In North Dakota and Minnesota, site-specific fungicides, such as quinone outside inhibitors (QoIs) and demethylation inhibitors (DMIs), had been widely and extensively applied to control C. beticola which has developed resistances to these fungicides. The mycelial growth, spore production, spore germination, and aggressiveness of QoI and/or DMI resistant isolates were compared to sensitive isolates in a laboratory and greenhouse study. Results indicated that the QoI and/or DMI resistant isolates had a relatively slower disease development on sugar beet leaves due to their fitness penalty in sporulation and mycelial growth but still caused high disease severities as sensitive isolates. Fungicides were evaluated to manage the QoI and/or DMI resistant C. beticola isolates in a sensitivity study and a greenhouse and field study. Copper-based multisite activity fungicides were evaluated for controlling fungicide resistant C. beticola. The mean EC50 values for nine copper-based chemicals ranged from 1 to 10 ug/ml using a spore germination assay. In a greenhouse study, Fertileader (a copper-based fertilizer) caused leaf injury and was not evaluated, but the other tested chemicals provided significantly better control of CLS compared to the control check with Badge X2, Champion, Cuprofix, COCS and Ridomil having significantly small AUDPC. Newer site specific fungicides with different modes of action that have never been used for CLS management in North Dakota and Minnesota were also tested. The mean EC50 values were 4.9, 33.1, 99.4, and 481.6 ug/ml using mycelial growth assay and 5.7, 4.1, 9.2, and 4.2 ug/ml using spore germination assay for cyprodinil, fluazinam, pydiflumetofen, and Chlorothalonil, respectively. In a two-year field study, all the fungicides resulted in significantly better disease control, significantly higher beet tonnage, and recovered sucrose compared to the nontreated check. However, none of tested fungicide treatments performed better than the industry?s standard fungicide, triphenyltin hydroxide.

Antalet patientbesök på landets akutmottagningar har ökat och inflödet av patienter är oförutsägbart vilket kan leda till en ojämn arbetsbelastning, långa väntetider och påverkad patientsäkerhet. De som söker vård upplever många gånger oro för sin hälsa och upplever därmed att de behöver hjälp och en snar medicinsk bedömning av sitt hälsotillstånd. Utifrån detta har flera av landets akutmottagningar infört så kallad spot check, vilket innebär att en sjuksköterska bedömer patienten genom ett kort “face to face”-möte redan i akutmottagningens reception. Spot check görs i syfte att bedöma hur snart ett triageteam på akutmottagningen bör träffa patienten, alternativt om patienten kan hänvisas till annan vårdnivå. Syftet med studien var att beskriva sjuksköterskors upplevelser av faktorer som kan påverka patientsäkerheten vid “spot check” på akutmottagningar. Som metod användes en kvalitativ intervjustudie med induktiv ansats. Intervjuer utfördes på två akutmottagningar i västra Sverige. Tio sjuksköterskor med minst två års erfarenhet av arbete på akutmottagning inkluderades. Dessa intervjuades med semistrukturerade frågor. Intervjumaterialet transkriberades ordagrant och analyserades genom en kvalitativ innehållsanalys. Resultatet av innehållsanalysen utmynnade i två kategorier: “Spot check som arbetsmetod” och “Arbetssätt för ökad patientsäkerhet”. Utifrån dessa formulerades fyra underkategorier. Dessa handlade om hur hänvisningar redan i spot check kunde påverka flödestiderna på akutmottagningen, att sekretess var en viktig faktor för att bevara patienternas integritet samtidigt som bristande sekretess kunde försvåra adekvata bedömningar i spot check. Vidare framkom upplevelse av att patientsäkerheten stärktes genom att en sjuksköterska både ser och bedömer patienten direkt vid dennes ankomst och att sjuksköterskan har uppsikt över väntrummet. Slutligen betonades vikten av att sjuksköterskan, för att främja god patientsäkerhet, behövde vara både kompetent och erfaren för att arbeta i spot check. Studiens slutsats indikerar att spot check som arbetsmetod kan vara ett sätt för akutmottagningar att skapa förutsättningar för ökad patientsäkerhet, genom att patienter redan vid ankomst till akutmottagningen får en tidig medicinsk bedömning av sitt hälsotillstånd av en sjuksköterska i receptionen.

Soybean (Glycine max [L.] Merr.) is one of the most important crops in the world. The average annual yield losses due to soybean diseases and pests are estimated to be around 11% in the United States. Soybean yield losses due to sudden death syndrome (SDS), caused by the fungus Fusarium virguliforme O'Donnell & T. Aoki have been problematic in majority of the soybean producing states. In recent years, reniform nematode (RN, Rotylenchulus reniformis Linford and Oliveira) and frogeye leaf spot (FLS), caused by the fungus Cercospora sojina K. Hara have emerged as a major problem in the southern soybean producing states. Planting resistant cultivars is one of the most cost-efficient methods in managing SDS, RN, and FLS, therefore it would be critical to identify and map the quantitative trait loci (QTL) that underlie their resistances. Two soybean populations were evaluated in this study. The ‘Essex’ × ‘Forrest’ 77 near-isogenic lines were screened in the field to evaluate the disease index of SDS. The Essex × Forrest and ‘Flyer’ × ‘Hartwig’ recombinant inbred lines were screened in the greenhouse to assess the reproduction index of RN and the disease severity of FLS. The BARCSoySNP6k chip was used to genotype the two populations. Four QTL that underlie SDS resistances were mapped in the same region as Rfv06-01, Rfv06-02, Rfv13-01, and Rfv19-01. The Rfv06-02 interval in this study was smaller than the one previously reported. Rrr08-01, Rrr13-01, Rrr15-01, Rrr18-01, and Rrr18-02 were reported to confer resistances to RN. Rrr08-01, Rrr13-01 and Rrr15-01 were novel whereas Rrr18-01, and Rrr18-02 were mapped in previous studies. cqSCN-001 (soybean cyst nematode, Heterodera glycines Ichinohe) was identified in the same region as Rrr18-01, and Rrr18-02 whereas cqSCN-006 was identified in the same region as Rrr15-01. These findings provide further evidence that there are common sources of genetic resistances to RN and SCN. Rcs15-01 and Rcs15-02 were reported to confer resistances to FLS. Rcs15-01 was novel and Rcs15-02 was mapped at the same region as an Rcs mapped in a previous study. This indicated that Rcs15-02 has dual resistances to C. sojina races. Candidate genes were inferred in this study. The QTL mapped in this study could potentially be used in soybean breeding programs that aim to introgress genetic resources that confer resistances to SDS, RN, and FLS.

Frogeye leaf spot is a foliar disease of soybean caused by Cercospora sojina Hara, which until recently had been successfully managed by quinone outside inhibitor (QoI) fungicides. After widespread resistance to the QoI fungicides was reported throughout Mississippi, the next step in characterizing C. sojina was to study the fitness of selected isolates. Fitness measurements of resistance stability, colony growth, conidia production and germination, and virulence were assessed. A phylogenetic analysis was also conducted to assess the genetic similarity of the QoI-resistant and -sensitive C. sojina isolates. All isolates remained stable in terms of QoI resistance. Results of all fitness measurements indicated no significant differences between the QoI-resistant and -sensitive C. sojina isolates. The phylogenetic analysis supported these results revealing similarity between QoI-resistant and -sensitive C. sojina isolates. Based on these results no indication of a fitness cost is associated with QoI resistance in C. sojina isolates from Mississippi soybean.

Abiotic stress tolerance and biotic stress resistance have long been targets for trait improvement in the field of plant breeding. To date, much of the target crop focus has been centered on commodity crops such as corn, soybean, wheat, and rice. However, little work has been conducted on improvement of these traits in forage grasses. This is due to a number of issues, particularly that most species are obligately outcrossing, the traits are governed by many genes at unknown loci, and are greatly affected by environmental variation. This creates major complications in successfully selecting and breeding populations of forage grasses tolerant to extreme high or low temperatures, as well as disease resistance. Recurrent phenotypic selection was used to select elite individuals of annual ryegrass (Lolium multiflorum Lam.) and orchardgrass (Dactylis glomerata L.) that expressed improved germination at high temperature. Selections were conducted within growth chambers at fixed temperature and light regimes (40/30 DEGREES C, 12/12 hr, light/darkness) to eliminate environmental variation. Following three cycles of selection, we observed gains (P LESSTHAN 0.001) in selection over the base population for both species. Annual ryegrass mean cumulative germination for cycle 3 peaked at 45.8%, and orchardgrass mean cumulative germination for cycle 3 peaked at 82.67%. Further selection of annual ryegrass for freezing tolerance was also conducted. Flats of unselected germplasm were grown to the three-leaf stage, then frozen for nine hours. Significant differences (P LESSTHAN 0.05) in freezing tolerance were observed between selected germplasm in both cycle 1 (0.076%) and cycle 2 (0.125%) over the unselected cycle 0 (0.025%). Finally, initial stages of resistance breeding work were conducted involving gray leaf spot (causal agent Pyricularia grisea Cke. [Sacc.]) on annual ryegrass. Isolates of the pathogen were obtained and stored for future use. It was determined that the actual pathogen species responsible was Pyricularia oryzae Cavara. Future work for annual ryegrass and orchardgrass germplasm that germinates at high temperatures will involve variety testing and cultivar release. Freezing tolerance and disease resistance work will require larger-scale screening methodology that was able to be conducted in this work to acquire sufficient population sizes for breeding.