Approved for public release; distribution is unlimited / The purpose of this thesis is to find suitable ways to design feedback compensators for high order systems by using Root-Locus methods. As a starting point we will examine a motor amplidyne system and a position control system that were previously designed using Bode methods. Then we generalize the method and extend it to other systems. The final subject of this thesis is to design feedback compensators as filters by using state feedback coefficients to define zeros of the filter, then we extend this idea to build cascade filters. / http://archive.org/details/designingfeedbac00kork / Lieutenant, Junior Grade, Turkish Navy

A number of techniques were used to obtain a variety of bacterial and fungal species antagonistic to Pythium - F group in hydroponic systems. Isolations were made from roots of ‘escape’ lettuce plants in a commercial hydroponic gravel system as well as Pythium mycelium exposed to the hydroponic solution. Seventy four bacterial and eighteen fungal isolates were obtained and were screened for in vitro activity against Pythium by means of the dual culture method. Twenty-two bacterial isolates rendered between 10.8 and 48 % inhibition and ten fungal isolates rendered between 24.3 and 54 % inhibition of Pythium mycelial growth. Potential biocontrol agents were screened in a static aquaculture system on butterhead lettuce seedlings in the greenhouse prior to evaluation in a re-circulating gravel bed hydroponic system in the greenhouse and field, for both growth promoting and biocontrol ability. Significant increases of between 689 % and 922 % in total fresh yield were obtained from plants preventatively treated with isolates JH49, JH41, JH83, JM6R and JM16W. The eight best performing isolates were further evaluated for biocontrol activity against Pythium as well as growth promotion on butter head lettuce in a re-circulating gravel bed hydroponic system in the greenhouse. Significant increases of 1.5 % - 63.5 % and 0.9 % - 38.8 % in total fresh yield were obtained from plants evaluated for growth promotion and Pythium control, respectively. Based on their performance five of the eight isolates were selected for evaluation in a re-circulating gravel bed hydroponic field system. Treatment with Pseudomonas fluorescens and Bacillus subtilis significantly increased fresh leaf weight of lettuce plants in comparison with the untreated control indicating effective suppression of Pythium. Of the isolates that were previously evaluated against Pythium wilt and root rot of lettuce in a hydroponic system (Chapters 2 and 3), 6 bacteria and 2 fungi were most effective. The following possible modes of action of these isolates, were investigated, namely competition, production of inhibitory substances and induced resistance. The root colonizating ability of the isolates was also assessed. Competition between the isolates and the pathogen were confirmed by testing for siderophore and hydrolytic enzyme production. Five of the isolates produced siderophores much faster than the rest, demonstrating that these isolates were able to take-up iron from the media at a faster rate, thus indicating a significant competitive ability. Antibiotic production by the isolates was confirmed in vitro by means of the dual culture technique. Of the eight isolates screened, only one isolate showed in vitro inhibition of the pathogen. This result was confirmed by a TLC assay, where fluorescent bands were formed by the same isolate, indicating the presence of phenolic compounds. These compounds were separated by HPLC. Analysis of total soluble and cell wall phenolic levels in Pythium infected and non-infected plants treated and untreated with the biocontrol isolates did not render conclusive results. Three of the eight isolates were able to colonize 100% of the lettuce roots. / Dissertation (MSc (Plant Pathology))--University of Pretoria, 2008. / Microbiology and Plant Pathology / unrestricted

Chemical and biological aspects of thiarubrine, a highly antifungal dithiacyclohexadiene polyine, were investigated. A tissue culture system for the production of thiarubrines was developed by culturing hairy roots of Chaenactis douglasii induced by Agrobacterium rhizogenes strain TR7. One culture line accumulated two times the levels of thiarubrines of nontransformed control root cultures, while maintaining rapid growth. The combination of fast growth and high thiarubrine accumulation could not be duplicated in controls by adding exogenous NAA to the culture medium. Hairy root cultures also produced less thiarubrine B relative to thiarubrine A compared to controls. Thiarubrine synthesis appears to be closely correlated with degree of tissue differentiation; it is suggested that it may be more practical to improve the growth rate of thiarubrine-producing root cultures by transformation rather than seek to induce synthesis in fast-growing suspension cultures. The biosynthetic relation between thiarubrines and the always co-occurring thiophenes was investigated by performing ³⁵S tracer experiments with C. douglasii hairy root cultures. It is possible that the thiophenes are not actively synthesized by the roots but rather are products of thiarubrine decomposition resulting from the extraction procedures and other manipulations of the cultures. The in vitro conversion of thiarubrine to thiophene can be induced by light, heat and other agents. No turnover of thiarubrines could be detected in the cultures in late logarithmic or stationary phases of the growth cycle. I Thiarubrines show strong light-independent antibacterial and antifungal activity. The mechanism of action of thiarubrine against E. coli and S. cerevisiae was investigated using comparative disk bioassays. A very similiar polyine from Rudbeckia hirta was as active as thiarubrine in the dark, indicating the central role of the disulfide ring in toxicity of the compounds. Visible light enhanced this activity suggesting that decomposition of the disulfide ring is important for its antibiotic effects. The photodegradation product, a thiophene, is phototoxic, probably via both type I and type II photosensitization mechanisms. The root culture extracts of Rudbeckia hirta yielded a new isomer of a known dithiacyclohexadiene polyine. MS and NMR analyses confirmed the cis configuration of this isomer. / Science, Faculty of / Botany, Department of / Graduate

Indigenous Rhizobium isolates from naturally-formed bean root nodules were antagonistic to some of the root rotting pathogens of snap bean. Rhizobium isolates inhibited the radial growth of Fusarium species in dual culture agar plate tests but were not inhibitory to Rhizoctonia solani or Pythium isolates. With one exception, all indigenous Rhizobium isolates showed some degree of antagonism towards F. solani f. sp. phaseoli in vitro. The level of in vitro inhibition depended upon the agar plate technique utilized. A high level of in vitro inhibitory activity was recorded in 38% of the Rhizobium isolates tested where wide zones of inhibition formed between the test isolates and persisted for more than 1 week. A similar inhibitory effect of 8/17 nodulating Rhizobium isolates to Fusarium root rot of snap bean was observed in growth pouch experiments. Protection of bean plants from severe Fusarium root rot occurred in combinations where the inoculum concentration of Rhizobium (10\ 106 cells/pouch) was equal to or greater than the inoculum concentration of F_. solani (10² , 10⁴ spores/pouch). Ten Rhizobium isolates, which were highly antagonistic in vitro, had no apparent inhibitory effect on Fusarium root rot in vivo. Two Rhizobium isolates, RCC324 and RCC607, inhibitory to Fusarium root rot did not reduce Rhizoctonia root rot of bean. Soil experiments supported the results of growth pouch experiments whereby inoculation of bean seed with a high concentration of Rhizobium (RCC106 at 10⁸ cells/seed) effectively reduced bean root rot incited by a low inoculum potential of the pathogen, F. solani (inoculum: soil, 1:10⁴ or 1:120). These results indicated the potential exists for field control of Fusarium root rot of snap bean by a highly antagonistic nodulating isolate of Rhizobium. / Land and Food Systems, Faculty of / Graduate

<p>Plant root phenotyping technologies play an important role in breeding, plant protection, and other plant science research projects. The root phenotyping customers urgently need technologies that are low-cost, in situ, non-destructive to the roots, and suitable for the natural soil environment. Many recently developed root phenotyping methods such as minirhizotron, CT, and MRI scanners have their unique advantages in observing plant roots, but they also have disadvantages and cannot meet all the critical requirements simultaneously. The study in this paper focuses on the development of a new plant root phenotyping robot that is minimally invasive to plants and working in situ inside natural soil, called “MISIRoot”. The MISIRoot system (patent pending) mainly consists of an industrial-level robotic arm, a mini-size camera with lighting set, a plant pot holding platform, and the image processing software for root recognition and feature extraction. MISIRoot can take high-resolution color images of the roots in soil with minimal disturbance to the root and reconstruct the plant roots’ three-dimensional (3D) structure at an accuracy of 0.1 mm. In a test assay, well-watered and drought-stressed groups of corn plants were measured by MISIRoot at V3, V4, and V5 stages. The system successfully acquired the RGB color images of the roots and extracted the 3D points cloud data which showed the locations of the detected roots in the soil. The plants measured by MISIRoot and plants not measured (controls) were carefully compared with Purdue’s Lilly 13-4 Hyperspectral Imaging Facility (reference). No significant differences were found between the two groups of plants at different growth stages. Therefore, it was concluded that MISIRoot measurements had no significant disturbance to the corn plant’s growth.</p>

Magister Scientiae Dentium - MSc(Dent) / Statement of problem: Although bioceramic endodontic sealer cements offer various advantages over conventional zinc oxide-based and resin-based cements, questions have been raised about the ability to retreat root canals that have been sealed using these cements. Aims and Objectives: The aim of the study was to determine the retreatability of root canals sealed using a bioceramic calcium silicate-based sealer cement. The objectives were to determine the possibility of achieving working length and apical patency when obturation is done with the master GP placed at working length and when it is short by 3mm. The time it took to achieve these parameters when it was possible to achieve them was also determined. The role of XP Endo Finisher R, a supplementary retreatment file, in achieving working length and apical patency was also to be evaluated. However, this latter aspect was eliminated after the pilot study, when it was found not to have an effect in regaining working length and apical patency.

The main objective of root canal therapy is cleaning, shaping and obturating the root canal system in three dimensions, as well as preventing reinfection. The objective of this in vitro study was: <ul> <li>to establish the antimicrobial efficacy of nine different root canal irrigation solutions, </li> <li>to determine the smear layer dissolving capabilities of these irrigating solutions, at various levels in straight root canals, and </li> <li>to examine the degree of erosion caused by the irrigation solutions on the root canal walls. </li></ul> Antimicrobial Effects: In this test the antimicrobial activity of nine irrigation solutions against E. faecalis was measured using a disc diffusion test. The antibacterial activity of materials was apparent from circular clear inhibition zones forming around the filtration paper. Effect on Smear Layer: Root canals were prepared by using Pro Taper nickel titanium rotary files. During preparation, the canals were irrigated with copious amounts of 3.5% sodium hypochlorite for 15 minutes. Thereafter, the teeth were randomly divided into nine groups. One group was kept as control. The other eight groups received a final rinse with one of the following irrigation solutions: 18% EDTA, Sterilox, Top Clear 17% EDTA, 2% Chlorhexidine, 10% Citric acid, Biopure MTAD, Ozonated water and Smear Clear. A total of 25ml of each solution was utilized to irrigate each root canal system, and left undisturbed in the root canal for 2 minutes. Biopure MTAD was left in the root canals for 5 minutes. Finally, the irrigation solutions were removed from the root canals with 10ml sterile distilled water. Each root was sectioned horizontally with a diamond disc in sections corresponding with the coronal, middle and apical levels of the root canal system. Each fragment was fractured laterally and prepared according to standard methods for biological SEM evaluation. The absence or presence of the smear layer as well as the amount of erosion of the peritubular dentine was assessed. The One-way ANOVA test was used to determine whether there were any statistical significant differences between the different test groups. No significant inhibition of E. faecalis was observed with sterile water (control) and the undiluted solutions of Sterilox, 10% Citric acid and Ozonated water. However, 3.5% NaOCl, 18% EDTA, Top Clear 17% EDTA, 2% Chlorhexidine, Biopure MTAD and Smear Clear showed significant inhibition of E. faecalis. For the 1/10 diluted solutions no inhibition of E. faecalis was observed with sterile water (control), 3.5% NaOCl, Sterilox, 10% Citric acid and Ozonated water. Biopure MTAD and Smear Clear demonstrated significant inhibition of E. faecalis compared to 18% EDTA, Top Clear 17% EDTA and 2% Chlorhexidine. Biopure MTAD was the only solution that showed significant inhibition of E. faecalis using a 1/100 diluted solution. No inhibition was observed with the 1/1000 diluted test solutions.Scanning electron microscope examination revealed that 3.5% NaOCl and Ozonated water had no visible effect on the smear layer. The 10% Citric acid solution slightly modified the smear layer at the coronal and middle levels of the root canals. There was no visible effect on the smear layer at the apical levels. Sterilox and 2% Chlorhexidine removed the smear layer at the coronal levels, modified it slightly in the middle levels and left the smear layer undisturbed in the apical levels of the root canals. 18% EDTA, Top Clear 17% EDTA, Biopure MTAD and Smear Clear removed the smear layer completely at the coronal levels. At the middle and apical levels of the root canals most of the smear layer was removed. However, there were less open dentinal tubules visible at the apical levels compared to the samples examined at the middle levels of the root canals. It was also noted that Top Clear 17% EDTA caused a significantly high percentage of erosion of the peritubular dentine at the coronal levels of the root canals compared to all the other irrigation solutions. Considering all the results of the present study Biopure MTAD demonstrated the best antimicrobial activity against E. faecalis, and removed most of the smear layer at all three levels of the root canal systems without significant erosion of the peritubular dentine. / Dissertation (MSc(Odont))--University of Pretoria, 2008. / Community Dentistry / unrestricted

The work is focused on the lateral roots, which are an indispensable part of the root system and play a key role in communication with rhizosphere and the efficient exploitation of natural resources. Tetratricopeptide-repeat Thioredoxin-like 3 gene (TTL3) was identified by forward screening based on its gene expression pattern in the search for genes associated with the development of lateral roots in Arabidopsis thaliana. TTL3 also known as VIT (VH1 interacting TPR containing protein), belongs to a family of four paralogues in Arabidopsis showing a very similar arrangement of domains. It seems that this type of proteins is widespread in plants and provides protein-protein signaling as an important component of phytohormone response pathways. The presented diploma thesis is focused on characterization and comparison of expression patterns of the four members of TTL family, through creation of pTTL::uidA (GUS) transcriptional fusions. The promoter area was estimated to be contained in about 2000bp upwards the TTLs coding sequences and transcriptional fusions with uidA gene were individually constructed and transformed into Arabidopsis via Agrobacterium tumefaciens. The expression patterns of analyzed genes were microscopically confirmed and allowed comparison among members of TTL gene family with regard...

Humphreys (1990) defines a simple root system for a finite reflection group which is an important concept fundamental to the understanding of reflection groups as well as Coxeter complexes and Coxeter groups. The proof that Humphreys uses to establish the existence and uniqueness of these systems follows an indirect method that left portions of the proof as exercises to the reader. I present a more complete and direct proof using different organization and methods.

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