The presence of toxic order ow and predatory HFT strategies in a multi-market setting are scarcely researched in the academic world. This thesis studies the toxicity levels of a set of markets by examining unconsolidated quote data and firm specific trade data. A method for deducing the markets toxicity levels is presented along with proxies for toxic order ow, namely: changes in spread and quoted volume, following a trade in a given market. We find both signs of toxicity and different toxicity levels between the markets. However, the results are lacking in statistical significance but they show that this field is of great interest for further research. Also, the methods proposed for deducing the toxicity levels are rudimentary but could serve well as a premise for further development. / Närvaron av toxic order flow och predatoriska HFT-strategier i en flermarknadsmiljö är föga studerat i den akademiska världen. Denna avhandling studerar detta på en uppsättning marknader genom att undersöka okonsoliderad quote data och firma specifika trades, och på så vis ta fram marknadernas toxicity-nivåer. En metod för att fastställa marknadernas toxicity-nivåer presenteras tillsammans med proxys för toxic order flow, mer specifikt: förändringar i spread och quotad volym, efter en handel på en given marknad. Vi finner både tecken på toxicity och olika toxicityniv åer mellan marknaderna. Resultaten saknar dock statistisk signifikans men de visar ändå på att detta område är av stort intresse för ytterligare forskning. De metoder som föreslås för att fastställa toxicity-nivåerna är rudimentära, men kan tjäna som en utgångspunkt för vidare utveckling.

<p>Bed bugs (<i>Cimex lectularius</i> L.) are globally important human ectoparasites. Their management necessitates the use of multiple control techniques. Plant-derived essential oils are extracts from aromatic plants that represent one of the alternative control measures for bed bug control, in addition to mechanical options and synthetic pesticides. However, there is limited information available on the efficacy and toxicology of plant essential oils against bed bugs. This project was designed with the aim to provide in-depth information on efficacy, toxicology and mode-of-action of essential oils and their insecticidal constituents in bed bugs. Initially, I evaluated topical and fumigant toxicity of fifteen essential oil components against adult male bed bugs of the Harlan strain (an insecticide susceptible strain). Neurological effects of the six most toxicologically active compounds were also determined. In both topical and fumigant bioassays, carvacrol and thymol were the most active compounds. Spontaneous electrical activity measurements of the bed bug nervous system demonstrated neuroinhibitory effects of carvacrol, thymol and eugenol, whereas linalool and bifenthrin (a pyrethroid class insecticide) produced excitatory effects. Further, I evaluated the efficacy and neurological impacts of a mixture of three neuroinhibitory compounds; carvacrol, eugenol and thymol in 1:1:1 ratio against adult male bed bugs of the Harlan strain. This mixture of monoterpenoids as well as the mixture of synthetic insecticides exhibited a synergistic affect in topical bioassays. In electrophysiology experiments, the monoterpenoid mixture led to higher neuroinhibitory effects, whereas a mixture of synthetic insecticides caused higher neuroexcitatory effects in comparison to single compounds. </p> <p>In the next objective of my dissertation, I compared the efficacy of five plant essential oils (thyme, oregano, clove, geranium and coriander), their major components (thymol, carvacrol, eugenol, geraniol and linalool) and EcoRaider^® (commercial product) between pyrethroid susceptible (Harlan) and field collected (Knoxville) bed bug populations. Initially, I found that the Knoxville strain was 72,893 and 291,626 fold resistant to topically applied deltamethrin (a pyrethroid class insecticide) compared to the susceptible Harlan strain at the LD₂₅ and LD₅₀ lethal dose levels, respectively. Synergist bioassays and detoxification enzyme assays showed that the Knoxville strain possesses significantly higher activity of cytochrome P450 and esterase enzymes. Further, Sanger sequencing revealed the presence of the L925I mutation in the voltage gated sodium channel gene. The Knoxville strain, however, did not show any resistance to plant essential oils, their major components or EcoRaider^® in topical bioassays (resistance ratios of ~ 1). In the final objective, I evaluated the efficacy of binary mixtures of above-mentioned essential oils or their major components or EcoRaider^® with deltamethrin in susceptible and resistant bed bugs. In topical application bioassays, binary mixtures of essential oils or their major components or EcoRaider^® and deltamethrin at the LD₂₅ dose caused a synergistic increase in toxicity in resistant bed bugs. Further, I studied the inhibitory effects of major essential oil components on detoxification enzyme activities (cytochrome P450s, esterases and glutathione transferases). Detoxification enzyme assays conducted using protein extracts from bed bugs pre-treated with essential oil constituents showed that these compounds significantly inhibited cytochrome P450 activity in the resistant strain, but esterase and glutathione transferase activity were unaffected. No inhibition of detoxification enzyme activities was observed in the Harlan strain bed bugs pre-treated with essential oil constituents.</p> <p>In conclusion, my dissertation research has created the foundation for utilization of natural products for bed bug management by (i) describing the efficacy of plant essential oils and their components against bed bugs, (ii) discovering synergistic interactions between essential oil components at the nervous system level, (iii) determining susceptibility of deltamethrin-resistant bed bugs to plant essential oils and their constituents and (iv) identifying synergistic effects of essential oils or their components on toxicity of pyrethroid insecticides and underlying mechanisms of this synergistic interaction. </p> <br>