Two-photon fluorescence microscopy (2PFM) has become a powerful technique for bioimaging in non-invasive cancer diagnosis and also investigating the mechanization and original of a variety of diseases by tracking various biological processes. Because the fluorescence emission by two photon absorbing (2PA) is directly proportional to the square of the intensity of excitation light, this intrinsic property of 2PA provides 2PFM great advantages over traditional one-photon fluorescence microscopy (1PFM), including high 3D spatial localization, less photodamage and interference from biological tissue because of using longer wavelength excitation (700-1300 nm). However, most 2PA probes are hydrophobic and their photostabilities are questionable, severely limiting their biological and medical applications. In addition, probes with significant specificity for certain organelles for tracking cellular processes or metal ions for monitoring neural transmission are somewhat rare. Moreover, it is also very significant to deliver the probes to specific disease sites for early cancer diagnosis. In order to increase the water solubility of probes, polyethylene glycol (PEG) was introduced to a fluorene-based 2PA probe LT1 for lysosomal 2PFM cell imaging. The 2PFM bioimaging application of the novel two-photon absorbing fluorene derivative LT1, selective for the lysosomes of HCT 116 cancer cells is described in Chapter II. Linear and nonlinear photophysical and photochemical properties of the probe were investigated to evaluate the potential of the probe for 2PFM lysosomal imaging. After the investigation of the cytotoxicity of this new probe, colocalization studies of the probe with commercial lysosomal probe Lysotracker Red in HCT 116 cells were conducted. A high colocalization coefficient (0.96) was achieved and demonstrated the specific localization of the probe in lysosomes. A figure of merit, F[subscript M], was introduced by which all fluorescent probes for 2PFM can be compared. LT1 was demonstrated to have a number of properties that far exceed those of commercial lysotracker probes, including much higher 2PA cross sections, good fluorescence quantum yield, and, importantly, high photostability, all resulting in a superior figure of merit. Consequently, 2PFM was used to demonstrate lysosomal tracking with LT1. In addition to lysosomes, it is also very significant to investigate the physiological roles of free metal ions in biological processes, especially Zn²⁺, because Zn²⁺ normally serves either as the catalytic elements in enzymatic activity centers or as structural elements in enzymes and transcription factors. However, biocompatible and effective Zn²⁺ probes for 2PFM bioimaging are infrequent. In Chapter III, 2PFM bioimaging with a hydrophilic 2PA Zn²⁺ sensing fluorescent probe, bis(1,2,3-triazolyl)fluorene derivative, is described. 2PFM bioimaging of the probe in living HeLa cancer cells was demonstrated. The results revealed a significant fluorescence increase upon introduction of Zn²⁺ into the cancer cells, and a reversible Zn²⁺ binding to the probe was also demonstrated, providing a robust probe for two-photon fluorescence zinc ion sensing. Early cancer diagnosis is another critical application for 2PFM, but there are still huge challenges for this new technique in clinical areas. Most 2PA probes with large two-photon absorbing cross sections and fluorescence quantum efficiency are synthetically more accessible in hydrophobic forms. In order to increase the efficiency of the probes and minimize the effect of the probe on the human body, delivery of the probe specifically to cancer sites is desired. The synthesis and characterization of narrow dispersity organically modified silica nanoparticles (SiNPs), diameter ~30 nm, entrapping a hydrophobic two-photon absorbing fluorenyl dye, are reported in Chapter IV. The surface of the SiNPs was functionalized with folic acid to specifically deliver the probe to folate receptor (FR) over-expressing HeLa cells, making these folate 2PA dye-doped SiNPs potential candidates as probes for two-photon fluorescence microscopy (2PFM) bioimaging. In vitro studies using FR over-expressing HeLa cells demonstrated specific cellular uptake of the functionalized nanoparticles. However, when the concentration of the dye in SiNPs increased for higher signal output, the fluorescence quantum efficiency of a probe normally decreases because of self-quenching. In Chapter V, a near-infrared (NIR) emitting probe is reported to overcome this limitation through both aggregate-enhanced fluorescence emission and aggregate enhanced two-photon absorption. The dye was encapsulated in SiNPs and the surface of the nanoparticles was functionalized with PEG followed by a folic acid derivative to specifically target folate receptors. NIR emission is important for deep tissue imaging. In vitro studies using HeLa cells that upregulate folate receptors indicated specific cellular uptake of the folic acid functionalized SiNP nanoprobe. Meanwhile, the probe was also investigated for live animal imaging by employing mice bearing HeLa tumors for in vivo studies. Ex vivo 2PFM tumor imaging was then conducted to achieve high quality 3D thick tissue tumor images.

The aim of this dissertation is to gain a better understanding of the unique electronic structure of lead salt quantum dots (QDs) and its influences on the nonlinear optical (NLO) properties as well as the time dynamics of the photogenerated charge carriers. A variety of optical techniques such as Z-scan, two-photon excited fluorescence and time-resolved pump probe spectroscopy are used to measure these properties. The one-photon as well as the degenerate and nondegenerate two-photon absorption (2PA) spectra are measured and the electronic wave functions from a four-band envelope function formalism are used to model the results. We observe local maxima in the 2PA spectra for QD samples of many different sizes at energies where only 1PA is predicted by the model. This is similar to the previously measured transitions in the 1PA spectra which are not predicted by the model but accrue at the energies of the two-photon allowed transitions. Most importantly we observe 2PA peaks for all samples at the energy of the first one-photon allowed transition. This result can only be understood in terms of symmetry breaking and therefore is strong evidence that other transitions, not predicted by the model if the selection rules are left intact, also have the origin in the lifted spatial symmetry of the wave functions. On the other hand, the uniquely symmetric eigenenergies of these quantum-confined energy states in the conduction and valance bands explain the observed trend toward larger two-photon cross-sections as the quantum confinement is increased in smaller QDs. Moreover, this unique feature is shown to reduce the possible relaxation channels for photoexcited carriers, which is confirmed experimentally by the reduced carrier relaxation rate as compared to CdSe QDs which lack this symmetry. Carrier multiplication (CM), a process in which several electrons are excited by the iv absorption of a single photon is studied in PbS QDs. We show that for PbS QDs with radius smaller than 2.5 nm the parameters of CM get very close to the theoretical optimum. Nextgeneration solar cells operating under these ideal conditions could potentially have conversion efficiency of up to 42%. This compares favorably to the 30% efficiency limit of a single junction silicon solar cell.

This study explores optimal strategies for maximizing scores and winning in the popular dice game Qwixx, analyzing both single and multiplayer gameplay scenarios. Through extensive simulations, various strategies were tested and compared, including a scorebased approach that uses a formula tuned by MCMC random walks, and race-to-lock approaches which use absorbing Markov chain qualities of individual score sheet rows to find ways to lock rows as quickly as possible. Results indicate that employing a scorebased strategy, considering gap, count, position, skip, and likelihood scores, significantly improves performance in single player games, while move restrictions based on specific dice roll sums in the race-to-lock strategy were found to enhance winning and scoring points in multiplayer games. While the results do not achieve the optimal scores attained by prior informal work, the study provides valuable insights into decision-making processes and gameplay optimization for Qwixx enthusiasts, offering practical guidance for players seeking to enhance their performance and strategic prowess in the game. It also serves as a lesson for how to approach optimization problems in the future.

Wood structural elements are more vulnerable to blast loading due to the inherent brittle nature and low density of the material, as demonstrated by recent significant research efforts on the behaviour of timber elements subjected to the effect of blast loading. These studies showed that wood performs poorly under blast loading. A way of improving this performance is to provide additional ductility or energy absorption capabilities to wooden elements. Recently, there was interest in investigating and developing energy-absorbing connections (EAC) to improve timber assemblies’ ductility and energy absorption capabilities. Although some research effort has been made to investigate the use of EACs to enhance the ductility of reinforced concrete or structural steel members, only limited work is available on this topic about timber elements. The current study aims to systematically investigate the use of various shapes of EACs to be used to enhance the post-peak performance of timber assemblies. Preliminary finite element analysis led to selecting nine steel EACs with varying geometries for further experimental investigation. A total of eighteen specimens were tested statically. In comparison, a total of eighteen specimens were tested dynamically in the shock tube facility of the University of Ottawa to simulate the effects of far-field blast explosions. The experimental results showed that decreasing the leg length or increasing the thickness of EACs manufactured with steel angles and reducing the diameter of EACs manufactured with circular HSS caused an increase in yield load and elastic stiffness while reducing the densification displacement. Connections with angles and a centre weld, and connections with 90-degree arcs from circular HSS, were identified as unsuitable for the application of EACs. The experimental program also showed that EACs manufactured from angles offer a well-defined plateau able to absorb a large quantity of energy, making them particularly suitable for blast mitigation. EACs manufactured from multiple circular HSS were shown to achieve multiple load-displacement plateaus and present an interesting option for systems with multiple failure modes occurring at different levels. SDOF analysis and FEA were conducted to predict the experimental behaviour with some success. The importance of the weld type was also highlighted from both the analytical and experimental results. A methodology for developing idealized load-displacement curves from experimental results of EACs was also proposed and evaluated.

During the last years perovskite materials have taken the photovoltaic community by storm, bringing promises of solar cells with efficiencies comparable to conventional silicon devices but at a lower price. However perovskite solar cells so far are facing two main obstacles, they are unstable in the presence of air, moisture and heat and they are usually toxic due to being based on lead-halide materials. This has spurred investigations into alternative materials with similar properties but without the mentioned drawbacks. Just next to Pb in the periodic table is bismuth (Bi) with just one more electron in its outer-shell, Bi however is less toxic. In this work the perovskite derived compounds of Ag-Bi-I and Cu-Bi-I are characterized and their properties as light absorbing material in solar cell devices are investigated. Devices are prepared by preparing Ag-Bi-I and Cu-Bi-I solutions which are then spin-coated on top of a mesoporous TiO2. A conducting polymer, P3HT, was then deposited and serve as hole transport material. For Ag-Bi-I, the molar ratios of AgI:BiI3= 1:2 and 2:1 were observed with SEM to form homogeneous crystal films with one dominating crystal phase, which by XRD could be determined to most likely have formed a cubic AgBi2I7 crystal structure for the 1:2 ratio and a hexagonal Ag2BiI5 crystal structure for the 2:1 ratio. The Cu-Bi-I materials were not successfully synthesized to form homogeneous films with a dominating crystal phase, although several molar ratios were investigated. All investigated compositions of both Cu and Ag devices showed to in principle work as light absorbing materials, the best Ag-Bi-I device showing a PCE of 1.92%, for the 2:1 ratio, while the Cu-Bi-I devices at best reached 0.32% for a ratio of 1:1. XPS measurements were carried out with a classical in-house XPS using an Al K X-ray source of 1486.7 eV as well as at the Diamond Light Source (UK) synchrotron facility using photon energies of 758 eV and 2200 eV so that a depth resolution of the composition could be observed. Because of their inhomogeneous crystal formation, XPS couldn’t give much useful quantitative information regarding the Cu devices. For Ag devices it was observed that the stoichiometry at the extreme surface deviated from that predicted by XRD, but deeper into the surface the relative ratio of elements approach the predicted ones, hinting towards a different structure at the outermost surface or a lot of surface defects. For all samples, two types of bismuth atoms were observed, metallic (Bi0) as well as a cationic (Bi+x), the later corresponding to Bi atoms which are partaking in the crystal bond. The ratio of metallic to cationic Bi was observed to decrease notably just a few nm below the extreme surface. The effect of the high presence of metallic Bi on final device performance was not concluded with certainty but not believed to be positive. By varying the annealing temperature, after spin coating the light absorber solution on the TiO2, it was observed that lower temperature resulted in a lower ratio of metallic Bi. As final conclusions, it was said that the synthesis method of Cu-Bi-I needs to be improved before those materials can be studied further. The synthesis of Ag-Bi-I is showing much more promise and one can start looking into further optimizing their final device structure to boost efficiency. Both Cu-Bi-I and Ag-Bi-I devices are relatively simple, cheap and energy efficient (with annealing temperatures around 150C) to produce, great aspects for solar cells. UVVis measurements showed they have band gaps around 1.6-1.7 eV which makes them a great potential material for use in tandem solar cells together with a semiconductor of lower band gap such as silicon.

This thesis aims at developing conceptual and methodological tools in order toadapt sound within the textile design area. Occupational groups working with soundare to a large extent problem driven. Accordingly, textile designers working withsound- affecting properties of textiles concentrate on their dampening qualities. Theambition with this research project is to make suggestions how textile designers canwork practically with textile sound design, in a more nuanced way.The overall aim of the thesis is to develop a vocabulary to make textile designersable to express the sound affecting qualities of textiles in a language full of nuances.As a starting-point the thesis briefl y describes commonly used methods andprocesses used to describe the expressiveness of a design, followed by a morethoroughly analyze of the textile design process illustrated by a practical example.These studies constitute a foundation to make it possible to see in what way thesemethods and processes will be affected when sound is added as new design tool.By studies of two sound design models, the fi rst attempts to develop a vocabularyconcerning how to describe sound affecting qualities of a textile are developed.Research focusing on language issues, especially on the development of conceptualtools done at the research institute CRESSON, provides descriptive soundconcepts, “sound effects”, embracing the interaction between human and his soundenvironment. These concepts are followed by a model of how to describe just asound or “sound object” in “itself” (not in relation to anything else), developed byPierre Schaeffer. These theoretical models have been complemented with empiricalstudies in form of a survey, named LISTEN. Interviews were performed from aphenomenological perspective. A number of informants were asked to tell aboutthe sound environment and single sounds occurring at their working places. Theinterviews were interpreted from a phenomenographic perspective. A number ofdesign projects are fi nally presented as practical examples of different ways to workwith textiles and sound.The theoretical models provided by Schaeffer have been used to make the fi rstsystematic attempts to describe sound environments; sounds and textiles soundaffecting properties.Since the model presented by Schaeffer is developed to be used within musicalcomposition the concepts have to be additionally modifi ed to be a useful tool withinthe textile design area. The thesis presents just the fi rst attempts to use this model.The next step to take in the research project is to adjust the theoretical systems ofCRESSON and Schaeffer to suit the special area of textile design. The interactiveideas of a sound-affecting textile will also be a subject of further development.

Within the field of ecosystem science, substantial progress has been made towards our knowledge of the factors which shape the global distribution of vegetation. However, factors which control the biogeography of belowground vegetation structure and function remain less understood than their aboveground counterpart. Vegetation types can differ substantially in terms of belowground processes such as root growth, root turnover, and resulting vertical root distributions. Fine roots provide an exchange surface, allowing transport of water and nutrients to the leaves. On the other hand they also represent a significant sink for photosynthetically fixed carbon to the soil in terms of maintenance and growth. Overall, root processes have a major influence on fluxes of water, carbon and nutrients within ecosystems. In this thesis, an electrical impedance method was used to determine the area of ‘active’ root in contact with the soil for the purpose of absorption. These measurements were compared to the leaf area of the trees, for the first time allowing the aboveground and the belowground resource exchange areas of plant to be contrasted. This approach was first developed to compare the exchange surface areas of leaves and roots within a Sitka spruce (Picea sitchensis) managed forest, making measurements in adjacent stands of differing tree density, but identical in age. Stem density was found to significantly influence the proportion of absorbing root area relative to leaves. Following the successful test of the method, it was used to compare the resource exchange areas of eight stands of forest and savanna vegetation in central Brazil. Across a broad gradient of vegetation structure, the results showed progressively more investment in fine root area relative to leaf area across the transition from dense forest to open savanna. However, a contrasting result showed that the forests had a higher absorbing root area to leaf area ratio than savannas. Furthermore, these measured ratios were strongly correlated with tree height across the eight structurally contrasting stands. It appears that absorbing root area index provides a physiologically meaningful way of characterising belowground water uptake ability, it is possible that excessive investment in fine root area, relative to leaf area, may reflect differences in the requirement for nutrient uptake in poor soils. Complementary to the analysis of root absorbing area, measurements of root activity and belowground carbon cycling were made by focussing on two of the eight tropical study sites. Here, the carbon costs of root growth and respiration were quantified to develop a belowground carbon budget for two structurally contrasting Brazilian savannas, using soil respiration measurements and a root presence/absence manipulation experiment. Annual estimates showed that at least 60% of the total CO2 efflux from the soil was contributed by autotrophic processes, with this value rising to 80% during the dry season. Seasonal fluctuations of soil respiration were strongly correlated with soil moisture for both the autotrophic (R2=0.79, pvalue< 0.05) and heterotrophic (R2=0.90, p-value<0.05) components, with maximum flux rates corresponding with 16.4 and 17.7% soil moisture content respectively. Furthermore, autotrophic respiration was found to varied with phonological patterns of fine root growth (R2=0.80, p-value<0.05). It follows that, the way in which phenological processes respond to a changing climate is of potential importance within seasonally dry regions. Diurnal fluctuations of heterotrophic CO2 efflux were correlated with soil temperature (R2=0.74, p-value<0.05), demonstrating a Q10 value of 1.6 across both sites. In contrast, total soil CO2 efflux was not correlated with temperature (p-value=0.31), suggesting that autotrophic respiration is predominantly limited by substrate supply.

In this paper we establish the regularity, exponential stability of global (weak) solutions and existence of uniform compact attractors of semiprocesses, which are generated by the global solutions, of a two-parameter family of operators for the nonlinear 1-d non-autonomous viscoelasticity. We employ the properties of the analytic semigroup to show the compactness for the semiprocess generated by the global solutions.

The ill-posed problem of aerosol size distribution determination from a small number of backscatter and extinction measurements was solved successfully with a mollifier method which is advantageous since the ill-posed part is performed on exactly given quantities, the points r where n(r) is evaluated may be freely selected. A new twodimensional model for the troposphere is proposed.

We say that (weak/strong) time duality holds for continuous time quasi-birth-and-death-processes if, starting from a fixed level, the first hitting time of the next upper level and the first hitting time of the next lower level have the same distribution. We present here a criterion for time duality in the case where transitions from one level to another have to pass through a given single state, the so-called bottleneck property. We also prove that a weaker form of reversibility called balanced under permutation is sufficient for the time duality to hold. We then discuss the general case.