Introduction: The Rho family of small GTPases, including Rac1 and Rac2, are key regulators of osteoclast differentiation and function; however, little is known about their roles in bone quality and aging. Methods: Male four and nine month old mice (n=10) with Rac1, Rac2 or both (DKO) isoforms deleted in osteoclast precursors were assessed using dual energy x-ray absorptiometry (DXA), scanning electron microscopy (SEM), micro computed tomography (microCT), compression, torsion and three-point bending testing, back scattered electron microscopy (BSE), Goldner’s trichrome and TRAP staining. Results: All Rac null mice demonstrated decreased cortical structural properties and improved trabecular architecture. With age, Rac null mice demonstrated the ability to attenuate age-related bone loss. Conclusions: Using an in vivo model with Rac1, Rac2 or both Rac isoforms deleted in osteoclasts, our findings demonstrate the deletion of Rac1 and Rac2 compromised cortical bone while improving trabecular bone properties and attenuated age-related bone loss.

Introduction: The Rho family of small GTPases, including Rac1 and Rac2, are key regulators of osteoclast differentiation and function; however, little is known about their roles in bone quality and aging. Methods: Male four and nine month old mice (n=10) with Rac1, Rac2 or both (DKO) isoforms deleted in osteoclast precursors were assessed using dual energy x-ray absorptiometry (DXA), scanning electron microscopy (SEM), micro computed tomography (microCT), compression, torsion and three-point bending testing, back scattered electron microscopy (BSE), Goldner’s trichrome and TRAP staining. Results: All Rac null mice demonstrated decreased cortical structural properties and improved trabecular architecture. With age, Rac null mice demonstrated the ability to attenuate age-related bone loss. Conclusions: Using an in vivo model with Rac1, Rac2 or both Rac isoforms deleted in osteoclasts, our findings demonstrate the deletion of Rac1 and Rac2 compromised cortical bone while improving trabecular bone properties and attenuated age-related bone loss.

In the first part of this dissertation, we study the aging of soot, a representative type of primary aerosols, in the presence of OH-initiated oxidation products of toluene. Monodisperse soot particles are introduced into an environmental chamber where toluene is oxidized by OH radicals. The variations in soot particle properties are simultaneously monitored, including particle size, mass, organic mass faction, hygroscopicity, and optical properties. The changes in particle properties are found to be largely governed by the thickness of the organic coating that is closely related to reaction time and initial reactant concentrations. Derived from particle size and mass, the effective density increases while dynamic shape factor decreases as the organic coating grows, suggesting a compaction of the soot morphology. As the organic coating grows, the particles become more hygroscopic and have enhanced light scattering and absorption. The second part discusses the potential reactions between amines and some aerosol constituents and alteration of aerosol properties. The reactions between alkylamines and ammonium sulfate/bisulfate have been studied using a low-pressure fast flow reactor coupled to a mass spectrometer at 293 K. Alkylamines react with ammonium sulfate/bisulfate to form alkylaminium sulfates, suggesting the existence of alkylaminium salts in particle phase. We have extended our study to characterize the physicochemical properties of alkylaminium sulfates. The hygroscopicity, thermostability, and density of five representative alkylaminium sulfates have been measured by an integrated aerosol analytical system. All alkylaminium sulfate aerosols show monotonic size growth when exposed to increasing relative humidity. Mixing ammonium sulfate with alkylaminium sulfates lowers the deliquescence point corresponding to ammonium sulfate. Alkylaminium sulfates are thermally comparable to or more stable than ammonium sulfate. The densities of alkylaminium sulfate particles are lower than that of ammonium sulfate. Our results suggest that the organic compounds can effectively alter the composition and properties of atmospheric aerosols, considerably influencing the impacts of aerosols on air quality, climate forcing, and human health.

Age-related neurodegenerative proteinophaties, including polyglutamine (polyQ) diseases such as Huntington’s disease, are a group of disorders in which a single protein or a set of proteins misfold and aggregate resulting in a progressive and selective loss of anatomically or physiologically related neuronal systems. Despite evidence showing a clear relationship between mitochondrial dysfunction, aging and neurodegenerative proteinophaties, the extent of the mitochondrial respiratory chain deficits, the involvement of mitochondrial dysfunction and the mechanisms responsible for these processes are largely unknown. Using yeast models of cellular aging and polyQ disorders we show that mitochondrial dysfunction is an important contributor to the process of aging and age-related neurodegenerative diseases. Preserving mitochondrial function is essential for standard wild-type aging. Enhancement of mitochondrial biogenesis ameliorates polyQ cytotoxicity and is a required component of interventions that retard the aging process.

Understanding the toxicity of carbon nanomaterials, such as carbon nanotubes and graphenes, is important for the development of nanotechnology. Studies have shown that surface redox capability is an important factor for toxicity of carbon nanomaterials. We have measured the surface reductive capacity for a number of carbon nanomaterials in previous studies, but the effects of various engineering processes on surface redox capability have not been investigated until this study. In this study, commercially available carbon black, carbon nanotubes, standard reference materials, fullerenes, graphenes and acetylene soot generated in the lab were used. The carbon nanomaterials were subjected to heating at various temperatures in various atmospheres up to 500 ˚C, and soaking in water at room temperature under various atmospheres, and weathering in the powder form at room temperature under various atmospheres. The redox capability of the carbon nanomaterials was quantified in terms of the reductive capacity towards Fe3+ ions (RCFI). The RCFI values of the asreceived nanomaterials and that of the nanomaterials after various treatments were compared. The carbon nanomaterials were also characterized using x-ray photoelectron spectroscopy (XPS), for understanding the surface chemistry mechanisms of RCFI and the effects of various treatments. In general, heating induced a significant increase in RCFI, regardless of the atmosphere under which the nanomaterials were heated. On the other hand, aging in O2- containing atmospheres brought about significant decrease in RCFI, either in water suspension or in the powder form. Water vapor enhanced the aging effect of O2. CO2 was found to affect the RCFI and the aging of carbon nanomaterials. The extent of RCFI change due to heating or aging was dependent on the type of material. According to the XPS results, the RCFI of some carbon nanomaterials such as carbon black may be correlated with the C-O surface functional groups. However, the definitive correlation between the oxygen-containing surface functional group and RCFI for all carbon nanomaterials couldn’t be determined by the XPS result. This indicates that the RCFI changes of carbon nanomaterials after treatments mainly derived from the factors such as the active sites of edges other than the oxygen-containing surface functional group changes as other studies show. This suggests that the RCFI measurement cannot be replaced by XPS analysis. The effects of heating and aging on RCFI, and more generally the surface redox capability of carbon nanomaterials, reveals that various engineering and environmental processes may significantly change the toxicity of carbon nanomaterials. The findings of this study suggest that it is important to take into account the effects of engineering and environmental processes when assessing the toxicity of carbon nanomaterials.

The effect of pH, temperature, and ionic strength on the molecular conformation of five industrial polyacrylamide-based flocculants was investigated by determining intrinsic viscosities on dilute flocculant solutions. The Fedors equation was found to be most suitable for all flocculants for determining the intrinsic viscosity. The results indicated that the flocculants are fully extended in distilled water at natural pH and at 25°C as evidenced by the high intrinsic viscosities. The data pointed to the strong dependence of the intrinsic viscosity on the presence of salts as a result of the shielding of negatively charged carboxylate groups by the counterions. At a constant ionic strength of 0.01M NaCl, the flocculants assumed a coiled conformation, and further coiling was observed in the presence of small quantities of calcium chloride. CaC1₂ (0.001 mo1/L) There was a decrease in intrinsic viscosities at high pH (~8.5 and 10.5) that was merely attributed to an increase in ionic strength with the increase in concentration of Na⁺ at high pH. Intrinsic viscosity measurements at higher temperatures (35°C and 50°C) showed a small effect of temperature on the conformation of the flocculants. Higher temperature, however, seemed to accelerate the aging of the flocculant solutions. The degrees of anionicity of the flocculants were found to be in the range 1.5% to 50%, as determined through chemical analysis. It was established that determination of total organic carbon content and sodium assays is an accurate way of obtaining the degrees of anionicity of industrial flocculants. The solution stability of the flocculants in distilled water and in 0.01M NaCl was investigated over a period of three days. The reduced viscosities of the anionic flocculant in distilled water steadily decreased. The decrease was more dramatic at high temperature (50°C) than at room temperature, but no viscosity loss was observed in the presence of NaCl. The viscosity of the nonionic flocculant was stable in both distilled water and NaCl. The viscosity loss with time in the case of the anionic flocculant can be correlated with the hydrolysis of the weakly acidic carboxylate (C00⁻) groups to release OH⁻ ions and simultaneous association into uncharged carboxylic (C00H) groups that promote coiling of polyacrylamide. This effect is therefore very similar to the earlier-mentioned effect of sodium chloride.

The present thesis investigated age differences in emotion recognition skills of 146 older adults (age range 60-92 years) and 146 young adults (age range 18-25 years) in four experiments. Experiment 1 assessed participants� ability to categorise facial expressions of sadness, fear, happiness, and surprise. In Experiments 2 and 3, participants were asked to identify six emotions (happiness, sadness, surprise, fear, anger, disgust) from still and dynamic faces, alone and in combination with vocal expressions. Finally, Experiment 4 compared performance on these standard emotion recognition paradigms to that of more ecologically-valid measures; the Faux Pas and Verbosity and Social Cues Tasks. Across the four studies, there was evidence of an age-related decline in emotion recognition skills. Older adults were overall less sensitive to perceptual differences between faces in Experiment 1 and showed a loss of categorical perception effect for fearful faces. Older adults were less accurate than young adults at recognising expressions of sadness, anger, and fear, across types of expression (voices and faces). There were some differences across modalities, with older adults showing difficulties with fear recognition for faces, but not voices, and difficulty in matching happy voices to happy faces but not for happy voices and faces presented in isolation. Experiment 2 also showed that the majority of older adult participants had some decline in emotion recognition skills. Age differences in performance were also apparent on the more ecologically-valid measures. Older adults were more likely than young adults to rate the protagonist as behaving inappropriately in the Faux Pas Task, even with the control videos, suggesting difficulty in discriminating faux pas. Older adults were also judged to be more verbose and to offer more off-topic information during the Verbosity Task than young adults and were less likely to recognise expressions of boredom in the Social Cues Task. These findings are discussed in terms of three theoretical accounts. A positivity bias (indicating increased recognition and experience of positive emotions and reduction for negative emotions) was not consistent with the older adults� difficulties with matching happy faces to voices and relatively preserved performance with disgusted expressions. Age-related decline in cognitive processes did not account for the specific pattern of age differences observed. The most plausible explanation for the age differences in the present thesis is that age-related neurological changes in the brain areas that process emotions, specifically the temporal and frontal areas, are likely to contribute to the older adults� declines in performance on emotion categorisation, emotion recognition, and social cognition tasks. The implications for everyday social interactions for older adults are also discussed.

Older adults of the 21st century have not grown up with information and communication technology and may not have used computers in their working lives. However, they have experienced the many technological changes of the 20th century. Some changes have fundamentally altered communication, entertainment, and the kinds of knowledge and skills that are sought and valued. These changes are difficult to ignore because of their pervasiveness. In order to actively participate in their lifeworlds older adults face an imperative to adapt and meet new challenges. The purpose of this research was to investigate and interpret the lived experience of laterlife computer learners in non-formal learning environments. The research focused on the interpretation and understanding of the learning experience from the perspective of participants. Hence there is an ontological thread that is grounded in the lifeworld of older adults in Sydney, Australia. A hermeneutic phenomenological methodology was considered suitable because of its emphasis on understanding the lived experience of humans. A qualitative method was used in this study because it enabled existential insights into the learning experience from the perspective of learners and privileged their voices. Fourteen older adults volunteered to participate and were interviewed. Participants identified themselves as laterlife beginning computer learners. Interviews were audio-taped and analysed using an interpretative case study approach. Other analytic tools used were grounded theory, thematic analysis and narrative inquiry. Existential themes were identified and interpreted within a framework of wellbeing. The research found that participants engaged in learning optimistically and that they believed in their abilities and also in the worth of the learning they were undertaking. The learners believed the outcomes from learning would lead to greater opportunity for participation in their lifeworld. Without computer skills and knowledge they believed they would be ignored and relegated to a peripheral position as observers in their lifeworld. By undertaking learning they believed they were taking control of their current and future lives, acting in defiance of developmental theories that suggested ageing was a stage of life and not a process. However, the sense of agency and purpose was not without its pressures and hurdles and learning was perceived to be difficult, dynamic, frustrating and immensely satisfying. Their purposes and expectations were situated in the changing nature of the world and a desire to continue to live their lives authentically, as participants and not spectators. Laterlife computer learners in this study were seen to be learning and growing their lives into a future of their making.

Studies in a number of human tissues have revealed that the activities of mitochondrial respiratory chain enzyme complexes decline during the aging process. Other studies have suggested that aging increases the frequency of mitochondrial DNA (mtDNA) mutation and leads to the accumulation of mutant mtDNA species, mainly those with large deletions and point mutations. Although the mitochondrial theory of aging may be more applicable to post mitotic tissues, abnormalities of mtDNA have also been reported in tissues which retain a mitotic capacity. Fresh tissues from elderly patients are difficult to obtain and only a limited number of studies on biochemical examination of respiratory chain enzyme complex activities have been carried out. Prostate tissue is readily available in elderly male subjects because of the high prevalence of benign prostatic hypertrophy in this sub-group of the population, and endoscopic surgery is routinely performed for excision of the diseased prostate. In this study, mitochondrial respiratory function and the mtDNA mutations in prostate tissues of elderly patients (aged from 56 to 92) were studied in 24 subjects. This included the measurement of the activities of the respiratory chain enzyme complexes and screening for mitochondrial point mutations and deletions at sites commonly affected in neurodegenerative diseases. (For complete summary open document)

Flux of ferrous iron (FeII) to the estuarine environment, whether from bottom sediments or via groundwater seepage, has been identified as a potentially important source of iron required for the development and sustenance of nuisance blooms of the toxic cyanobacteria Lyngbya majuscula in Moreton Bay, Queensland. However the rapid oxidation of FeII in seawater imparts importance to the resultant form of ferric iron (FeIII). Oxidation of FeII in the presence of natural organic matter (NOM) results in a mixture of FeIII-NOM complex and amorphous ferric oxides (AFO). The fate of these oxidation products has implications for the supply of iron to L. majuscula where transformations over time scales of hours are likely to be important. In this thesis the process of oxidation of FeII in seawater in the presence of NOM and the subsequent transformations of the products of oxidation are investigated. UV and visible spectroscopic techniques were used to monitor the production of organically complexed FeIII for both NOM and a model organic compound. Kinetic modelling of data facilitated the examination of key reactions, especially those involving AFO. Controls on the reactivity and aging of AFO were investigated using two different dissolution reactions to measure reactivity. Light scattering techniques were used to probe the structure of AFO and X-ray absorption spectroscopy was used to examine the coordination environment of Fe centres within AFO. Analysis of a kinetic model of iron transformations parameterised using the best available knowledge revealed large uncertainty surrounding the role of ligand classes in complex formation and dissociation and the role of AFO in both formation of oxidation products and the subsequent decay of organically complexed FeIII. Laboratory studies demonstrated that, within a wide range of initial concentrations, unstable mixtures of FeIII-NOM and AFO are produced from the oxidation of FeII in seawater containing NOM and that the organic complexes immediately commence transformation to AFO. Simulation using numerical kinetic modelling of the processes investigated indicated that AFO has a significant role in the processes of formation of oxidation products and dissociation of organically complexed FeIII. The rapid aging that AFO was recognised to undergo was successfully incorporated into the model though whether the aging was due toeither 1) increased coordination of Fe centres or 2) decreased Fe centre accessibility due to aggregation could not be ascertained from the model results. However, together with information regarding the coordination environment of the Fe centres and the particle and fractal structure of the aggregates, aggregation was considered most likely to be the factor responsible for the observed and modelled decreases in AFO reactivity.