The Common bed bug, Cimex lectularius L., suddenly reappeared in developed countries in the past 15 years. The factor contributing to the sudden resurgence of the bed bugs is insecticide resistance. In this study, we investigated the mechanisms of reduced cuticular penetration type insecticide resistance in bed bugs. First, we determined and compared the lethal dosage (LD50) of a pyrethroid insecticide using topical and injection application. The resistant strain not only had significantly greater resistance ratios, but also demonstrated significantly greater penetration resistance ratios. This provided the evidence of the reduced cuticular penetration in bed bugs. Second, we determined the levels of gene transcription (CPR-type cuticle protein genes) using real-time quantitative polymerase chain reaction (qRT-PCR). We identified 62 putative bed bug cuticle protein-encoding contigs based on the presence of the Chitin-binding 4 (CB4) domain. Based on the qRT-PCR analysis of the mRNAs, we found many of the genes were up-regulated in the resistant strain suggesting thickening of the cuticle or increasing the cuticular proteins might be involved in the reduced cuticular penetration. Third, we identified and described the cuticular proteins using the matrix-assisted laser desorption/ionization (MALDI) time-of-flight/time-of-flight (TOF/TOF) high-resolution tandem mass spectrometry (MALDI-TOF/TOF). The total of 265 peptides were identified, among which 206 belonged to one of 50 confidently identified proteins. We identified the CPRL, CPF, CPFL, TWDL, and CPAP1 family proteins. The profile of the cuticular proteins between the resistant and the susceptible strains bed bugs were almost identical. Fourth, we determined and compared the cuticular thickness using Scanning Electron Microscopy (SEM). We found statistical differences of the cuticular thickness among different strains (populations), however, correlation between the levels of insecticide resistance and cuticular thickness were not found. Finally, we identified and described bed bug cuticular hydrocarbon profiles using Gas-Chromatography and Mass-Spectrometry (GC-MS). The total of 87 compounds in addition to n-alkanes were extracted and identified. There were no correlation found with the concentration and the levels of insecticide resistance. However, several additional compounds exhibited the correlation between the concentration of the compounds and the levels of insecticide resistance. Overall, we found three lines of evidence to support reduced cuticular penetration as a mechanism of insecticide resistance in some bed bug populations. This study provides additional evidence of the reduced cuticular penetration type resistance in bed bugs. / Ph. D.

No / A profile across 8 layers from a fossil travertine terrace from a low temperature geothermal spring located in Svalbard, Norway has been studied using both Raman spectroscopy and SEM (Scanning Electron Microscopy) techniques to identify minerals and organic life signals. Calcite, anatase, quartz, haematite, magnetite and graphite as well as scytonemin, three different carotenoids, chlorophyll and a chlorophyll-like compound were identified as geo- and biosignatures respectively, using 785 and/or 514 nm Raman laser excitation wavelengths. No morphological biosignatures representing remnant microbial signals were detected by high-resolution imaging, although spectral analyses indicated the presence of organics. In contrast, in all layers, Raman spectra identified a series of different organic pigments indicating little to no degradation or change of the organic signatures and thus indicating the preservation of fossil biomarker compounds throughout the life time of the springs despite the lack of remnant morphological indicators. With a view towards planetary exploration we discuss the implications of the differences in Raman band intensities observed when spectra were collected with the different laser excitations. We show that these differences, as well as the different detection capability of the 785 and 514 nm laser, could lead to ambiguous compound identification. We show that the identification of bio and geosignatures, as well as fossil organic pigments, using Raman spectroscopy is possible. These results are relevant since both lasers have been considered for miniaturized Raman spectrometers for planetary exploration.

Monitoring the non-metallic inclusions formed in steels is of the utmost importance. In fact, inclusions, depending on their type, can affect both the properties of the steel and its processing. Once the most problematic inclusions have been detected, solutions can be found and applied to counter the arising issues. One such solution is the addition of calcium during ladle treatment to modify the inclusions shapes and avoid the precipitation of problematic inclusions. The focus was put on the detection, analysis and calcium addition countermeasure of inclusions. No clear conclusion could be drawn as to the effects of calcium addition on the inclusions, due to the very high zirconium content of the inclusions. A high zirconium content has a significant impact on the thermodynamics governing inclusion formation and prevents reliable analysis of the results. After discussion with the company, it has been found that the zirconium is not present in the steel grade but instead originates from the samplers that were used. / Övervakning av icke-metalliska inneslutningar som bildas i stål är av yttersta vikt. Faktum är att inneslutningar, beroende på typ, kan påverka både stålets egenskaper och dess bearbetning. När de mest problematiska inneslutningarna har upptäckts kan lösningar hittas och tillämpas för att motverka de uppkomna problemen. En sådan lösning är att tillsätta kalcium under skänkbehandlingen för att ändra inneslutningarnas form och undvika utfällning av problematiska inneslutningar. Fokus låg på detektering, analys och kalciumtillsats som motåtgärd för inneslutningar. Ingen tydlig slutsats kunde dras om effekterna av kalciumtillsats på inneslutningarna, på grund av inneslutningarnas mycket höga zirkoniuminnehåll. En hög zirkoniumhalt har en betydande inverkan på den termodynamik som styr bildandet av inneslutningar och förhindrar en tillförlitlig analys av resultaten. Efter diskussion med företaget har det visat sig att zirkoniumet inte finns i stålsorten utan istället härrör från de provtagare som användes.

This dissertation delves into the exploration of calcium carbonate polymorphs and silica-based materials upcycled from waste cement paste using a two-step extraction and carbonation process as supplementary cementitious materials (SCMs) to simultaneously achieve solid waste upcycling and carbon sequestration in the built environment. With the growing urgency to mitigate carbon emissions associated with the cement industry—one of the largest industrial contributors to anthropogenic CO₂ emissions globally—there is a pressing need to develop low-carbon alternatives that do not compromise the performance of concrete. This research is motivated by the potential of marrying carbon capture, utilization, and storage (CCUS) and alternative SCMs through CO₂ mineralization of industrial by-products and waste materials to lower the embodied carbon of cement and concrete. This approach addresses two critical issues: the reduction of construction and demolition (C&D) waste and the creation of highly reactive SCMs that can partially replace ordinary Portland cement (OPC). The dissertation is structured into two primary parts: the first focuses on the synthesis and potential applications of calcium carbonate polymorphs that can be derived from CO₂ utilization, and the second on the upcycling of waste cement paste into reactive silica-based materials. The first part (Chapters 2, 3, and 4) of the dissertation centers on three anhydrous calcium carbonate polymorphs, calcite, aragonite, and vaterite, which were synthesized under controlled laboratory conditions. These polymorphs were first characterized comprehensively using analytical techniques including scanning electron microscopy (SEM) to observe their distinct morphologies, X-ray diffraction (XRD) to determine their crystalline structures, laser diffraction (LD) to analyze their particle size distribution, and Brunauer-Emmett-Teller (BET) analysis to measure their specific surface areas. The rheology, hydration, and stability of these polymorphs were then investigated after they were used as substitutes for Portland cement (OPC) in cement pastes at 10 wt% or 20% replacement level. In Chapter 2, detailed rheological analyses were conducted, including rotational and oscillatory shear tests, to evaluate the influence of these polymorphs on the viscosity, yield stress, and structural buildup of cement pastes. Aragonite, with its needle-like crystals, was found to significantly enhance the static yield stress and structural build-up rates while having a minimal impact on dynamic yield stress, making it particularly suitable for applications requiring high thixotropy, such as 3D printing of concrete. In Chapter 3, the polymorphs were found to affect the hydration kinetics of the cement pastes, with aragonite exhibiting the most pronounced accelerating effect, thereby contributing to faster early-age strength development. The differences in thermodynamic stability of the three polymorphs also resulted in slightly different phase assemblages as revealed via thermodynamic modeling, indicating potential beneficial effects of using metastable aragonite and vaterite in cement-based materials. The metastable vaterite was also found to be stabilized in cement systems despite its instability and tendency to convert to calcite in aqueous environments. In Chapter 4, the mechanisms underlying the stabilization of vaterite in cement paste were explored with carefully designed experiments to construct model systems to decompose the complex cement-based systems and isolate dominating factors. The deposit and growth of cement-hydrated phases on the surface of vaterite and calcite seeds were found to be the dominant mechanisms preventing the transformation of vaterite to calcite, stabilizing metastable vaterite even in the presence of calcite seeding. The second part (Chapter 5) of the dissertation investigates the reactivity of amorphous silica-based materials extracted from waste cement paste using a pH swing process as alternative SCMs. The upcycling process involves the leaching of calcium from waste cement paste, followed by a pH swing to precipitate undesired elements to isolate calcium for CO₂ mineralization. The resulting materials, referred to as "residue" and "precipitate," were thoroughly characterized and found to exhibit strong pozzolanic reactivity. When used as 10% replacements for OPC, these upcycled materials significantly improved the compressive strength of cement pastes, particularly at early ages. The study also explored the phase assemblages formed in these cement pastes after hydration via XRD and the chemical circularity of silicate structures during the upcycling and reincorporation processes. The results indicated that the incorporation of these upcycled SCMs can contribute to the hydration of cement pastes and enhance their mechanical properties, which proved the feasibility of using these upcycled materials as alternative SCMs. Overall, this dissertation presents a comprehensive study on the potential of calcium carbonate polymorphs and upcycled silica-based materials as alternative SCMs to lower the embodied carbon of cement-based materials. Calcium carbonate polymorphs can be incorporated into cementitious materials to improve their rheological properties, hydration behavior, and mechanical performance, while amorphous silica-based materials exhibited high pozzolanic reactivity and contributed to the enhancement of compressive strength. This research paves a new way to decarbonize the built environment through the combination of solid waste upcycling and carbon sequestration, contributing to the global efforts to reduce the carbon footprint of the cement industry and promote a circular economy within the construction sector.

Coals, from mines in the Highveld coalfield, as well as gasification ash samples were characterised, in order to understand the mineralogical and chemical properties of the individual components in the gasification feedstocks. X-ray diffraction of low temperature oxygen-plasma ash indicates that the coals contain significant proportions of kaolinite, quartz and a fluxing elements-bearing mineral (dolomite), plus minor concentrations of illite and other fluxing elements-bearing minerals namely calcite, pyrite and siderite. Of the feed coal, the -75+53 mm size fraction has a high pyrite, and to a lesser extent a high calcite and dolomite content. However, the small proportion of iron-bearing phases (from the reaction between kaolinite and pyrite) in samples taken from the gasifier implies that pyrite contributes minimally to sintering or slagging in this case. Calcite is mainly present in the >1.8 g/cm3 density fraction of the feed coal, whereas dolomite is mainly present in the 1.5-1.8 g/cm3 density fraction, as inclusions or fine cleats in the coal matrix. Electron microprobe analyses of coals from the six different South African mines confirmed that some Ca, Mg, Al, Si, Na, K, Ti and Fe are present in the organic matrix in the coal samples tested in this study, but the amounts of these are small compared with the fluxing elements in minerals. XRD and microprobe analyses indicate that the ash clinker samples taken from the gasifiers contain a number of crystalline high temperature phases, including anorthite, mullite, cristobalite, quartz and diopside. FactSage confirmed that anorthite and mullite are equilibrium phases at elevated temperatures in the ash clinkers and heated rock fragments. Limited reaction takes place between the included coal minerals and the extraneous rock fragments. / Thesis (PhD)--University of Pretoria, 2008. / Materials Science and Metallurgical Engineering / unrestricted

The thesis deals with modifying and biulding of scintilation detector of secondary electrons for environmental scanning electron microscopy. It describes dilemma of environmental scanning electron microscopy, types of detectors and secondary electrons detection. The experimental part of this thesis focuses on the design and construction of new scintillation detector on the basis of simulations secondary electrons trajectories. Identifying the parameters, pressure dependencies and optimizations of electrode system of the detector realized.

The genus Restrepia is well known to orchid enthusiasts but its micromorphology has not been described, and its pollination and breeding systems have not been investigated. The aim of this investigation was, therefore, to add to existing knowledge so that the resultant data could be used to facilitate ex situ conservation initiatives. A detailed electron microscopy study (SEM) of the floral organs was performed. This confirmed the structure of the dorsal sepal and lateral petal osmophores, their secretory nature together with that of the synsepal and the labellum. It was postulated how, by manipulating different labellar surface textures, the flower might use these ‘tactile guides’ to steer the insect (fly) through the flower. The cirrhi were postulated to help by destabilising the pollinator in flight, trapping it and bringing about pollination. The papillate structure of the calli was established and their optical properties investigated. Media comparison investigations established that Western medium supported the highest germination rates and, with the addition of banana supplement, the highest rates for seedling growth and development. This represented the first protocol for axenic germination of Restrepia in the literature (Millner et al., 2008) and provided a tested methodology for investigating breeding systems and producing Restrepia plant material for both scientific and horticultural purposes. Self-pollinations were found to produce fewer embryos compared to cross-pollinations. The operation of self-incompatibility (SI) was confirmed by the study of pollen tube growth which further confirmed the time interval between pollination and fertilisation. A time line from pollination/fertilisation to flowering was established. The type of SI in operation was best explained by gametophytic incompatibility. This demonstrated that it was possible to raise Restrepia hybrids and species from seed, by performing intraspecific crosses so helping to preserve them for posterity and relieve pressure on wild populations. Narrow endemic Restrepia species face combined threats from habitat loss, habitat degradation and problems of viable seed production due to the effects of SI and inbreeding depression (ID). Recently developed online resources, such as GeoCAT, were used to perform a Red List assessment in order to identify the degree of threat individual species faced, both globally and nationally. All species were classified as facing substantial levels of threat; although this was lessened for populations in protected habitats. Conservation is needed for cultivated collections as well as these wild populations by keeping alive existing knowledge and expertise in growing these species.

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