No description available.

The objective of this study was to encapsulate cell lines that secrete marker proteins that cover a large molecular weight range (M^r from 45,000 to 300,000) and monitor the secretion of the marker proteins from alginate-poly-L-lysine-alginate (APA) microcapsules and hydroxyethyl methacrylatemethyl methacrylate (HEMA-MMA) thermoplastic capsules. Different parameters for the APA microcapsules, such as the duration of poly-L-lysine (PLL) and sodium citrate treatment, the initial cell density for encapsulation was studied, and their effects on secretion rate and cell proliferation were closely examined. Cell lines used for encapsulation secreted human growth hormone (hGH) (M^r 45,000), β-hexosaminidase (β-hexo.) (M^r 120,000) and β-glucuronidase (β-gluc.) (M^r 300,000). Monitoring the secretion rates, as well as the distribution of the marker proteins within the microcapsules following encapsulation enabled the permeability of the membrane to be assessed over one month in culture. Encapsulation of cell lines in both types of capsules was effective in producing viable cells capable of proliferating within a semi-permeable membrane. Encapsulating cells in single-coated APA microcapsules at 4°C, treated with 10 minutes PLL, 20 minutes sodium citrate and at a cell density of 2x10^6 cells/ml alginate was found to provide the most optimal conditions for prolonged viability of and stable secretion by the recombinant cells. Human growth hormone diffused readily across the capsule membrane into the culture media from both APA and HEMA-MMA capsules, at rates similar to the non-encapsulated cells. Human growth hormone did not accumulate in the intracapsular space in significant quantities. β-glucuronidase and β-hexosaminidase could diffuse across APA capsule membrane, but not across HEMA-MMA capsule membrane into surrounding media. β-glucuronidase secretion from APA microcapsules was 8-fold lower than non-encapsulated cells. β-hexosaminidase secretion from APA microcapsules was 4.5-fold lower than non-encapsulated cells. Slight retention of both β-glucuronidase and β-hexosaminidase was observed in the intracapsular space of APA capsules. HEMA-MMA capsules completely blocked the secretion of both β-glucuronidase and β-hexosaminidase out of the capsule. Massive accumulation of both kinds of secretory enzymes was found in the intracapsular space of HEMA-MMA capsules. This indicated APA microcapsules have a molecular weight cut-off of >300,000 whereas HEMA-MMA microcapsules have a molecular weight cut-off of <120,000. / Thesis / Master of Science (MS)

No description available.

No description available.

The work presented herein focuses on expanding the use of CO2-triggered switchable surfactants in emulsion polymerization of hydrophobic and hydrophilic monomers. Bicarbonate salts of the following compounds were employed as surfactants in the emulsion polymerization of styrene, methyl methacrylate (MMA) and/or butyl methacrylate (BMA): N’-hexadecyl-N,N-dimethylacetamidine (1a), N’-dodecyl N,N-dimethylacetamidine (2a) and N’-(4-decylphenyl)-N,N-dimethylacetamidine (3a). A systematic study of the effects of surfactant and initiator concentrations and solids content on the resulting particle size and ζ-potential was carried out, showing that a wide range of particle sizes (40 – 470 nm) can be obtained. It was found that as the basicity of the surfactant decreased, the particle size generated from emulsion polymerization increased. Destabilization of these latexes did not require the addition of salts and was carried out using only non-acidic gases and heat. It was shown that solids content, temperature, particle size and surfactant basicity greatly affect the rate of destabilization of latexes. The area occupied by N’-dodecyl-N,N-dimethylacetamidinium acetate on PMMA particles was determined to be 104 Å2. The monomer-D2O partition coefficient of 2a was determined to be 21 for styrene and 2.2 for MMA. The monomer-D2O partition coefficient of the bicarbonate salt of 2a was determined to be 1.2 for styrene and 0.85 for MMA. An initial assessment of the use of switchable surfactants in the generation of inverse emulsions was carried out. It was determined that butylated polyethyleneimine (BPEI) can successfully stabilize inverse emulsions of cyclohexane and aqueous 2-(dimethylamino)ethyl methacrylate. Upon CO2 introduction, this emulsion separates into two distinct phases. / Thesis (Master, Chemistry) -- Queen's University, 2011-09-26 11:10:14.053

Experimental data on the solubility of CO2 in methyl methacrylate (MMA) and butyl methacrylate (BMA) are reported at temperatures from 308 to 333 K and pressures in the range of 1 to 10 MPa. The corresponding measurements of the volumetric expansion of the liquid phase are also presented. The solubility data are correlated with the Peng-Robinson equation of state using two interaction parameters. Solubilities of CO2 as high as 80 mol% can be attained in both monomers in the range of pressure considered. A near-linear relationship is observed between pressure and liquid-phase composition. The Peng-Robinson equation of state provides a satisfactory correlation of the solubility data. The average absolute relative deviations with respect to the calculated values of pressure are less than 2%. For a given monomer, the expansion isotherms coincide when plotted as a function of the liquid - phase composition. Catalytic chain transfer (CCT) polymerisation of CO2-expanded MMA, BMA and styrene is then described. Experimental values of the chain transfer constant are determined at 323 K and 333 K and in the range of pressure from 0.1 to 6 MPa. A cobaloxime complex is used as the chain transfer catalyst. The effect of small quantities of polymer on the volumetric expansion of the corresponding monomer is considered. The chain transfer constants for the expanded monomers are significantly higher than those obtained in the bulk monomers. It is demonstrated that a linear relationship exists between the chain transfer rate coefficient and the inverse of liquid-phase viscosity. These results provide significant evidence that the rate-determining step in the CCT process is diffusion-controlled. Finally, molecular weight evolution in CCT polymerization of CO2-expanded MMA is reported. Experimental molecular weight and polydispersity index data are presented at 323 K in the range of conversion from 1 to 25%, and at pressures of 5 and 6 MPa. Both molecular weight and polydispersity increase with conversion at conditions below the homogeneous expansion limit. Predici simulations suggest that either irreversible catalyst deactivation or cobalt-carbon bond formation is the most likely mechanism for the increase in molecular weight with conversion.

Introduction: Single sample TWA samples collected over an 8-hour shift have the potential to mask elevated exposures, excursions or “peaks” that may have occurred thus permitting situations where workers are over-exposed or indeed over-dosed. The objectives of this study, undertaken in a small acrylic sheet manufacturing plant, are therefore to identify tasks that have the potential to exceed short-term occupational exposure levels and then simultaneously monitor employees undertaking these tasks for 8-hour TWA and Short-Term exposure concentrations. The results obtained from this sampling are then compared to their respective legal limits and then finally correlated to establish their statistical significance. Materials and Methods: The study setting comprises a syrup room wherein two employees are assigned per shift. Employees in this setting manufacture an acrylic “syrup” which is achieved by dosing raw materials into any one of 13 mixing vessels. Whilst mixing, these vessels also heat the ingredients until the required viscosity is reached. This “syrup” comprising mostly of liquid methyl methacrylate, is then decanted into a pressure vessel from where it is pipe-fed into a casting chamber and finally poured between two glass sheets. When cured, the final product is stored and sold as a clear or tinted acrylic sheet. All operations with this area are therefore associated with facilitating the syrup manufacture. Personal 8-hour TWA and Task- Based measurements of methyl methacrylate vapour were simultaneously obtained from the breathing zones of six employees over five separate shifts. These employees routinely work within the setting and also undertake tasks that have the potential to exceed the Short-Term Occupational Exposure Limit (ST-OEL) for methyl methacrylate vapour. Tasks were studied and those selected for quantitative monitoring were captured using a qualitative risk assessment tool. These selections were based on studying each task to establish the employee’s exposure probability and severity i.e. whether performing the task could indeed lead to excessive Short-Term exposures. Eight-hour TWA monitoring was undertaken using activated carbon 3M 3500 passive monitoring badges which were attached to each of the subject’s breathing zone and left over 80 % of the shift. The task-based measurements were obtained by using a Drager PAC III electro-chemical monitoring instrument, which was also placed in each each 4 subject’s breathing zone, and provided real-time exposure data whilst the employees were undertaking the various tasks. Results: All measurements (N = 116) were obtained over a series of 5 full-shift monitoring periods. When analysed, 8 of the 10 of the TWA samples returned results that were below the 8-hour TWA OEL. Of the 106 task-based measurements obtained for the nine identified tasks, when averaged, 89.1 % of results exceeded the ST-OEL. When the TWA and ST measurements were correlated, only one of the nine tasks were statistically significant in their correlation. This correlation coefficient was however highly statistically significant (r = 0.339, p = 0.032 and r = 0.337, p = 0.022 respectively). Both negative and positive correlations were obtained however these were statistically insignificant. Discussion: A significantly higher proportion of the sample results were above the STOEL than the 8-hour TWA OEL concentrations contributing to the argument that ST exposure monitoring may add additional insight to employees’ exposure profiles. A major limitation of the study is however the small sample size, which makes it difficult, due to inter-worker variability amongst other factors, to extrapolate the results and their corresponding interpretations to larger, more generalised occupational hygiene monitoring scenarios. Conclusion: The results obtained therefore support the assertion that the inclusion of short-term monitoring is important in characterising employee exposures in situations where these tasks are themselves potential sources of significant chemical exposures. Recommendations: As a basis for undertaking any form of monitoring and particularly in settings where short-term, task-based exposures may exist, the importance of undertaking a systematic approach to hazard identification and risk profiling via the use of a known risk assessment tool to compile a air sampling programme, has been demonstrated in the results of this research. Further research that specifically addresses the problem of characterising workplace exposures would be useful in larger study populations as well as occupational settings which expose employees to the various types of airborne contaminant e.g. fume, mists, particulates and gases.

The liquid argon target of the DEAP-3600 dark matter detector is contained by an extremely radiopure acrylic vessel. Alpha decays from the inner surface of the acrylic vessel are a source of background. If a fraction of the alpha energy is observed, or if the recoiling nucleus from the alpha decay is observed, the event will not be separated from a dark matter candidate event. In addition to the low level of inherent contamination from uranium and thorium, the Pb-210 from Rn-222 diffusion during manufacturing must be measured. The limit for the DEAP-3600 acrylic vessel is 1.1 × 10^−20 g/g Pb-210. By vaporizing a large quantity of acrylic and counting the concentrated residue with an ultralow background HPGe well detector and a low background alpha spectrometer, the bulk acrylic was found to have an upper limit of 10^−19 g/g Pb-210. The design, installation, commissioning, operation, and analysis for various aspects of the acrylic assay are described. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2014-01-14 19:27:47.533

Thesis (Ph.D.) - University of St Andrews, May 2007. / Restricted until 3rd May 2012.

Thesis (Ph.D.) - University of Queensland, 2004. / Includes bibliographical references.