This project aimed at exploring new hybrid materials to be used for acoustophoresis applications. Acoustophoresis can be used to manipulate particles inside a microfluidic channel by creating ultrasound standing waves within the channel [1]. This can be used for cell separation [2] or trapping of particles [3]. The intent of this project was to create materials for use in microfluidic channels that would be cheaper and easier to manufacture than those traditionally used, while still having adequate acoustic properties to allow for use in acoustopheresis. This was done by investigating whether the addition of glass-beads or glass-bubbles could increase the acoustic properties of an off-stoichiometry-thiol-enes (OSTE) based polymer. Hybrid samples with different volume fractions of glass-beads or glass-bubbles added to the OSTE polymer were manufactured and characterised according to their acoustic properties using the pulse-echo buffer-rod method. The acoustic properties measured were the density, attenuation, acoustic impedance and the reflection coefficient between water and the material. The addition of glass-beads was found to increase the acoustic impedance while the inverse was found for the addition of glass-bubbles. Both the addition of glass-beads and glass-bubbles were found to increase the attenuation. The hybrid material that was found to have the most suitable acoustic properties was OSTE/Glass-beads 40%, whose acoustic impedance had been increased ∼60% compared to pure OSTE. Consequently, the OSTE/Glass-beads 40% material was used to manufacture a microfluidic channel. A particle trapping experiment showed that the OSTE/Glass-beads 40% microfluidic channel was able to obtain bead trapping. This means that a standing wave was able to be generated within the channel and that it was strong enough to trap particles in the centre of the channel. However, evaluation of the particle trapping efficiency of the channel showed that it was not as effective as those using traditional materials. Therefore, future work is recommended to optimise a channel design for the OSTE/Glass-beads 40% material to increase the particle trapping efficiency. / I detta projekt undersöktes ett nytt hybridmaterial för användning i applikationer inom akustofores. Akustofores kan användas till att manipulera partiklar inuti mikrofluidkkanaler genom att generera ståendevågor i kanalen med hjälpav ultraljud [1]. Detta kan användas till cellseparation [2] eller till att fånga partiklar [3]. Målet i detta projekt var att skapa material som skulle bli billigare och möjliggöra enklare fabricering av kanalerna som används inom akustofores än de material som traditionellt används, med bibehållande av tillräckliga akustiskaegenskaper. Detta genomfördes genom att undersöka om tillsättning av glaspärlor eller glasbubblor kunde förbättra de akustiska egenskaperna av en off-stoichiometry-thiol-enes (OSTE) baserad polymer. Hybridprover gjorda på OSTE-polymeren med olika volymandelar av glaspärloroch glasbubblor tillverkades och kategoriserades med avseende på deras akustiska egenskaper med hjälp av pulseeko buffertstång metoden. De akustiska egenskaperna som uppmättes var densitet, attenuering, akustisk impedans och reflektions koefficienten mellan vatten och materialet. Resultatet av projektet visade att tillsättning av glaspärlor ökade den akustiska impedansen  i motsatts till glasbubblorna som visade sig minska den. Vidare visade det sig att både tillsättningen av glaspärlor och glasbubblor ökade attenueringen. Det hybridmaterial som visade sig ha de mest lämpliga akustiska egenskaperna var OSTE/glaspärlor med en 40% volymandel av glaspärlor. Den akustiska impedansen hade förhöjts med cirka 60% jämfört med vanlig OSTE. Därför valdes det hybrid-materialet till att tillverka en mikrofluidikkanal. Därefter genomfördes ett partikelfångstexperiment som visade att, OSTE/glaspärlor med en 40% volymandel av glaspärlor, kunde erhålla partikelfångst i kanalen. Detta innebär att en stående våg kunde genereras i kanalen och att den var tillräckligt stark för att kunna fånga partiklarna i mitten av kanalen. Däremot visade utvärdering av kanalens partikelfångsteffektivitet att den inte var lika effektiv som kanaler gjorda av traditionellt använda material. Därför rekommenderas framtida arbete till att designa en optimerad kanaldesign med OSTE/Glas-pärlor 40% materialets egenskaper i åtanke för att förhoppningsvis kunna öka partikelfångst effektivitet.

A number of technologies rely on the conversion of short laser pulses from one spectral domain to another. Efficient frequency conversion is currently obtained in ordered nonlinear optical materials and requires a periodic spatial modulation of their nonlinear coefficient which results in a narrow bandwidth. One can trade off efficiency for more spectral bandwidth by relaxing the strict phase-matching conditions and achieve nonlinear interaction in carefully engineered disordered crystalline aggregates, in a so-called random quasi-phase-matching (rQPM) process. In this dissertation, we examine appropriate fabrication pathways for (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) and ZnSe transparent ceramics for applications in the mid-IR. The main challenge associated with the fabrication of high transparency PMN-PT ceramics is to avoid the parasitic pyrochlore phase. The most effective method to suppress the formation of this undesired phase is to use magnesium niobate (MgNb2O6) as the starting material. We have found that, contrary to commercially available lead oxide powders, nanopowders synthesized in our lab by the combustion method help improve the densification of ceramics and their overall optical quality. The effects of dopants on the microstructure evolution and phase-purity control in PMN-PT ceramics are also investigated and show that La3+ helps control grain-growth and get a pure perovskite phase, thereby improving the samples transparency. With large second order susceptibility coefficients and wide transmission window from 0.45 to 21 μm, polycrystalline zinc selenide is also an ideal candidate material for accessing the MWIR spectrum through rQPM nonlinear interaction. We have investigated non-stoichiometric heat-treatment conditions necessary to develop adequate microstructure for rQPM from commercial CVD-grown ZnSe ceramics. We have been able to demonstrate the world's first optical parametric oscillation (OPO) based on rQPM in ZnSe transparent ceramic, enabling broadband frequency combs spanning 3-7.5 μm.

The normal regulation of the Hedgehog (Hh) pathway is essential for embryonic development, stem cell maintenance, and gametogenesis for both vertebrates and invertebrates, whereas the aberrant pathway regulation can cause various developmental defects and cancers. Hence, it is important to understand the precise mechanism of how the Hh pathway is regulated. Much of our understanding of the Hh pathway comes from studies in Drosophila but applies also to vertebrates. In Drosophila, Hh signal transduction terminates with regulation of the transcriptional activator, Cubitus interruptus (Ci). In the absence of Hh signaling, Ci is 1) processed to a repressor form via the Costal2 (Cos2) complex and suppresses the transcription of Hh target genes or 2) inhibited by binding to Cos2 and Suppressor of Fused (Su(fu)). Once the cells receive Hh ligand, however, 1) Ci processing is inhibited and 2) inhibition by Su(fu), and possibly Cos2, is countered by Fused (Fu) kinase, which ultimately transforms Ci into an activator form that goes into the nucleus and induces the transcription of Hh target genes. How Fu alleviates Su(fu) inhibition and facilitates the activation of Ci is not well understood, and it was only discovered recently that Ci is the direct target of Fu phosphorylation. Many studies of Hh signaling have been conducted under artificial conditions, where proteins are often overexpressed, leading to findings that sometimes do not reflect in vivo events, where relative protein stoichiometry is important. For this dissertation, I investigated how Ci activation is regulated by Su(fu) and Fu using CRISPR/Cas to generate different Ci variants expressed at physiological levels in fly wing discs. I looked at how different regions of Ci, including known phosphorylation sites, contribute to the regulation of Ci activity. From this study, I propose that different sets of Ci phosphorylation events mediated by Fu are responsible for changes in Ci-Su(fu) interactions, by altering Ci-Su(fu) interfaces, but also by changing intramolecular Ci-Ci interactions and thereby transforming Ci to an active conformation, leading to target gene activation in response to Hh.

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I investigated the drivers of nutrient cycling by heterotrophic microbes during leaf decomposition in streams. My research addressed two overarching questions: 1) how do exogenous and endogenous factors interact to drive microbial nitrogen (N) cycling during organic matter decomposition in stream ecosystems, and 2) what affect will the global increase in biologically active N have on these factors and resulting fluxes? I conducted studies in natural streams and laboratory mesocosms to address these questions and used general stoichiometric theory to conceptualize diverse microbial assemblages as a single functional unit within stream ecosystems. First, I described spatial and temporal patterns of N and phosphorus uptake and mineralization by leaf-associated microbial assemblages in five southern Appalachian streams which spanned a gradient of nitrate availability. I found wide variations in nutrient fluxes across time and space, perhaps due to macroinvertebrate-induced changes in microbial assemblage composition. Secondly, I explored the roles of endogenous and exogenous N in meeting microbial requirements. I isolated microbial biomass from leaves that had been labeled with N-15 and incubated in the same five Appalachian streams. The importance of exogenous N increased as decomposition progressed and was particularly important in streams with high N availability. Finally, I tested potential interactions between two exogenous drivers of microbial nutrient cycling: N availability and animal activity. I used mesocosms to test the effects of consumer nutrient recycling (CNR) and grazing by two shredders on microbial uptake under different N regimes. Animals only influenced microbial uptake under low N conditions. Shredder CNR generally stimulated uptake while grazing had a negative effect. My research provides a robust model describing N cycling by detritus-associated microbes over the course of decomposition. According to this model, microbes assimilate endogenous N during the initial stages of decomposition and immobilization of exogenous N becomes more important as decomposition progresses. The labeled substrate technique that I used to generate this model is an elegant way of testing the applicability of this model in other ecosystems. My results also suggest that anthropogenic activities that increase exogenous N availability have implications for N and C cycling in lotic systems. / Ph. D.