Understanding and optimisation of non-conventional emulsions

This thesis is concerned with understanding the effect of diols on emulsion properties and to use knowledge gained to optimise emulsions containing them. The project was sponsored by GlaxoSmithKline, a world leading pharmaceutical company, whose interest is in using the knowledge to help in research and development of new products and optimising existing products during manufacture. For this reason pharmaceutical ingredients were used throughout unless additional knowledge could be gained from using non-pharmaceutical ingredients. Systems studied included emulsions with water, diols and paraffin liquid stabilised by surfactants and particles using various techniques from microscopy, conductivity, surface tension, rheology, light scattering, stability analysis, differential scanning calorimetry and nuclear magnetic resonance. The thesis will examine three aspects of emulsion non-conventionality; addition of diol to both surfactant and particle-stabilised emulsions and the effect of crystallisation in diol containing emulsions stabilised solely by surfactant. Surfactant and particle-stabilised systems will be discussed in terms of phase inversion where it will be shown that inversion of emulsions can be controlled by addition of diol within both systems. For phase inversion in water, diol, paraffin liquid and non-ionic surfactant systems it will be argued that the phase inversion witnessed is due to the change in preferred surfactant monolayer curvature. This will be shown by examining the structurally and isomeric nature of the diols as well as their surface activity. Also considered and compared will be the well established experimental facts that occur in related systems at phase inversion including initial droplet diameter, emulsion stability, temperature variation and surfactant structure change. Results will show that for all traits examined at phase inversion diol addition follows all well known facts regarding a change of preferred surfactant monolayer curvature from negative to positive values. Emulsions stabilised by particles will be shown to phase invert from w/o to o/w emulsions with the addition of diol and changing particle hydrophobicity at fixed hydrophobicity and fixed diol content respectively. This will be contributed to the surface energies of each system and therefore a decrease in contact angle θ with increasing diol addition and changing hydrophobicity. Included will be a comparison between calculated and measured phase inversion of a number of diol containing series which shows good correlation. Systematic studies will also include the effect of this phase inversion on droplet diameter, stability and emulsion type. These will be explained in terms of existing theory regarding particle stabilised emulsions. Diol effect on the in situ contact angle will also be shown in water/diol–air mixtures. Investigations will include the immersion times of fumed silica powders of varying wettability in water-propane-1,2-diol mixtures and from theory the contact angles of particles at the air-polar phase interface will be determined. The materials formed upon aerating these samples will also be described in terms of the wettability of the particles in situ. Again the result will indicate that diol increase the inherent hydrophilicity of the system and therefore change the materials formed upon aeration. The final chapter of the thesis will discuss the effects of crystallisation in emulsions containing diol stabilised solely by surfactant. Crystallisation with surfactant stabilised systems will be discussed in terms of changing temperature and varying droplet diameter of emulsions. It will be shown that droplet diameter has an effect on the crystallisation of dispersed oil droplets and linked to stability. Systemic investigations using differential scanning calorimetry, rheology and nuclear magnetic resonance will show the crystallisation effect of a model system and attempts to link such findings to stability and the crystallisation mechanism. Microscopy of an additional model system containing high amounts of diol will show the ability of such systems to produce ‘dumbbell’ droplets when the systems temperature is decreased. Additional discussion on the formation of dumbbells and the effect on stability in diol containing emulsions will also be considered

Understanding and optimisation of non-conventional emulsions

This thesis is concerned with understanding the effect of diols on emulsion properties and to use knowledge gained to optimise emulsions containing them. The project was sponsored by GlaxoSmithKline, a world leading pharmaceutical company, whose interest is in using the knowledge to help in research and development of new products and optimising existing products during manufacture. For this reason pharmaceutical ingredients were used throughout unless additional knowledge could be gained from using non-pharmaceutical ingredients. Systems studied included emulsions with water, diols and paraffin liquid stabilised by surfactants and particles using various techniques from microscopy, conductivity, surface tension, rheology, light scattering, stability analysis, differential scanning calorimetry and nuclear magnetic resonance.The thesis will examine three aspects of emulsion non-conventionality; addition of diol to both surfactant and particle-stabilised emulsions and the effect of crystallisation in diol containing emulsions stabilised solely by surfactant. Surfactant and particle-stabilised systems will be discussed in terms of phase inversion where it will be shown that inversion of emulsions can be controlled by addition of diol within both systems. For phase inversion in water, diol, paraffin liquid and non-ionic surfactant systems it will be argued that the phase inversion witnessed is due to the change in preferred surfactant monolayer curvature. This will be shown by examining the structurally and isomeric nature of the diols as well as their surface activity. Also considered and compared will be the well established experimental facts that occur in related systems at phase inversion including initial droplet diameter, emulsion stability, temperature variation and surfactant structure change. Results will show that for all traits examined at phase inversion diol addition follows all well known facts regarding a change of preferred surfactant monolayer curvature from negative to positive values.Emulsions stabilised by particles will be shown to phase invert from w/o to o/w emulsions with the addition of diol and changing particle hydrophobicity at fixed hydrophobicity and fixed diol content respectively. This will be contributed to the surface energies of each system and therefore a decrease in contact angle θ with increasing diol addition and changing hydrophobicity. Included will be a comparison between calculated and measured phase inversion of a number of diol containing series which shows good correlation. Systematic studies will also include the effect of this phase inversion on droplet diameter, stability and emulsion type. These will be explained in terms of existing theory regarding particle stabilised emulsions. Diol effect on the in situ contact angle will also be shown in water/diol–air mixtures. Investigations will include the immersion times of fumed silica powders of varying wettability in water-propane-1,2-diol mixtures and from theory the contact angles of particles at the air-polar phase interface will be determined. The materials formed upon aerating these samples will also be described in terms of the wettability of the particles in situ. Again the result will indicate that diol increase the inherent hydrophilicity of the system and therefore change the materials formed upon aeration.The final chapter of the thesis will discuss the effects of crystallisation in emulsions containing diol stabilised solely by surfactant. Crystallisation with surfactant stabilised systems will be discussed in terms of changing temperature and varying droplet diameter of emulsions. It will be shown that droplet diameter has an effect on the crystallisation of dispersed oil droplets and linked to stability. Systemic investigations using differential scanning calorimetry, rheology and nuclear magnetic resonance will show the crystallisation effect of a model system and attempts to link such findings to stability and the crystallisation mechanism. Microscopy of an additional model system containing high amounts of diol will show the ability of such systems to produce ‘dumbbell’ droplets when the systems temperature is decreased. Additional discussion on the formation of dumbbells and the effect on stability in diol containing emulsions will also be considered

Sulfate Reduction in Sediments Produces High Levels of Chromophoric Dissolved Organic Matter

Sulfate reduction plays an important role in altering dissolved organic matter (DOM) in estuarine and coastal sediments, although its role in the production of optically active chromophoric DOM (CDOM) and a subset of fluorescent DOM (FDOM) has not been previously investigated in detail. Freshwater sediment slurries were incubated anaerobically with added sulfate and acetate to promote sulfate-reducing bacteria. Ultraviolet visible (UV-Vis) absorbance and 3-dimensional excitation emission matrix (EEM) fluorescence spectra were measured over a five weeks anaerobic dark incubation period. Parallel Factor Analysis (PARAFAC) of FDOM determined components that increased significantly during dark and anaerobic incubation matching three components previously considered of terrestrially-derived or humic-like origin published in the OpenFluor database. The observed FDOM increase was strongly correlated (R2 = 0.96) with the reduction of sulfate. These results show a direct experimental link between sulfate reduction and FDOM production, which impacts our understanding of coastal FDOM sources and early sediment diagenesis. As 3D fluorescence techniques are commonly applied to diverse systems, these results provide increasing support that FDOM can have many diverse sources not consistently captured by common classifications such as “humic-like” fluorescence

Concert recording 2016-04-07

[Track 01]. English horn concerto / Vincent Persichetti -- [Track 02]. Divertissement / Euguene Bozza -- [Track 03]. Parable XV / Vincent Persichetti -- [Track 04]. Sonate / Paul Hindemith -- [Track 05]. Bassango / Mathieu Lussier -- [Track 06]. Blue rondo a la turk / Dave Brubek ; arranged by Richard Bobo

Mouthpiece for Patients with Neuromuscular Disorders

Neuromuscular Disorders (NMDs) impact people throughout the world. An early hallmark of these disorders includes some degree of facial muscle weakness. Respiratory testing is important to evaluate the progression of these patients’ NMDs. However, these tests require that the patient purses their lips around a mouthpiece to create a tight seal. This is a difficult task for one with facial muscle degeneration. This often leads to results that fail to reflect the patient’s true respiratory ability and prevents their physician from providing the appropriate degree of care. The objective of this project was to develop a face mask or mouthpiece for Negative Inspiratory Force (NIF) testing to allow these users to create a proper seal without use of their facial muscles. Through the engineering design process, a 3D printed prototype was designed to interface with NIF testing equipment. This proposed design uses bite force to create a tight seal, allowing for accurate test results, enhanced comfort, and better patient outcomes

Evaporation of particle-stabilised emulsion sunscreen films

We recently showed (Binks et al., ACS Appl. Mater. Interfaces, 2016, DOI: 10.1021/acsami.6b02696) how evaporation of sunscreen films consisting of solutions of molecular UV filters leads to loss of UV light absorption and derived sun protection factor (SPF). In the present work, we investigate evaporation-induced effects for sunscreen films consisting of particle-stabilized emulsions containing a dissolved UV filter. The emulsions contained either droplets of propylene glycol (PG) in squalane (SQ), droplets of SQ in PG or droplets of decane in PG. In these different emulsion types, the SQ is involatile and shows no evaporation, the PG is volatile and evaporates relatively slowly, whereas the decane is relatively very volatile and evaporates quickly. We have measured the film mass and area, optical micrographs of the film structure, and the UV absorbance spectra during evaporation. For emulsion films containing the involatile SQ, evaporation of the PG causes collapse of the emulsion structure with some loss of specular UV absorbance due to light scattering. However, for these emulsions with droplets much larger than the wavelength of light, the light is scattered only at small forward angles so does not contribute to the diffuse absorbance and the film SPF. The UV filter remains soluble throughout the evaporation and thus the UV absorption by the filter and the SPF remain approximately constant. Both PG-in-SQ and SQ-in-PG films behave similarly and do not show area shrinkage by dewetting. In contrast, the decane-in-PG film shows rapid evaporative loss of the decane, followed by slower loss of the PG resulting in precipitation of the UV filter and film area shrinkage by dewetting which cause the UV absorbance and derived SPF to decrease. Measured UV spectra during evaporation are in reasonable agreement with spectra calculated using models discussed here

Spectrophotometry of thin films of light absorbing particles

Thin films of dispersions of light absorbing solid particles or emulsions containing a light absorbing solute all have a non-uniform distribution of light absorbing species throughout the sample volume. This results in non-uniform light absorption over the illuminated area which causes the optical absorbance, as measured using a conventional specular UV-vis spectrophotometer, to deviate from the Beer-Lambert relationship. We have developed a theoretical model to account for the absorbance properties of such films which are shown to depend on the size and volume fraction of the light absorbing particles plus other sample variables. We have compared model predictions with measured spectra for samples consisting of emulsions containing a dissolved light absorbing solute. Using no adjustable parameters, the model successfully predicts the behaviour of non-uniform, light absorbing emulsion films with varying values of droplet size, volume fraction and other parameters

A Theory of the Wind-Driven Beaufort Gyre Variability

The halocline of the Beaufort Gyre varies significantly on interannual to decadal time scales, affecting the freshwater content (FWC) of the Arctic Ocean. This study explores the role of eddies in the Ekman-driven gyre variability. Following the transformed Eulerian-mean paradigm, the authors develop a theory that links the FWC variability to the stability of the large-scale gyre, defined as the inverse of its equilibration time. The theory, verified with eddy-resolving numerical simulations, demonstrates that the gyre stability is explicitly controlled by the mesoscale eddy diffusivity. An accurate representation of the halocline dynamics requires the eddy diffusivity of 300 ± 200 m^2 s^(−1), which is lower than what is used in most low-resolution climate models. In particular, on interannual and longer time scales the eddy fluxes and the Ekman pumping provide equally important contributions to the FWC variability. However, only large-scale Ekman pumping patterns can significantly alter the FWC, with spatially localized perturbations being an order of magnitude less efficient. Lastly, the authors introduce a novel FWC tendency diagnostic—the Gyre Index—that can be conveniently calculated using observations located only along the gyre boundaries. Its strong predictive capabilities, assessed in the eddy-resolving model forced by stochastic winds, suggest that the Gyre Index would be of use in interpreting FWC evolution in observations as well as in numerical models

Ploidy Controls the Success of Mutators and Nature of Mutations during Budding Yeast Evolution

SummaryBackgroundWe used the budding yeast Saccharomyces cerevisiae to ask how elevated mutation rates affect the evolution of asexual eukaryotic populations. Mismatch repair defective and nonmutator strains were competed during adaptation to four laboratory environments (rich medium, low glucose, high salt, and a nonfermentable carbon source).ResultsIn diploids, mutators have an advantage over nonmutators in all conditions, and mutators that win competitions are on average fitter than nonmutator winners. In contrast, haploid mutators have no advantage when competed against haploid nonmutators, and haploid mutator winners are less fit than nonmutator winners. The diploid mutator winners were all superior to their ancestors both in the condition they had adapted to, and in two of the other conditions. This phenotype was due to a mutation or class of mutations that confers a large growth advantage during the respiratory phase of yeast cultures that precedes stationary phase. This generalist mutation(s) was not selected in diploid nonmutator strains or in haploid strains, which adapt primarily by fixing specialist (condition-specific) mutations. In diploid mutators, such mutations also occur, and the majority accumulates after the fixation of the generalist mutation.ConclusionsWe conclude that the advantage of mutators depends on ploidy and that diploid mutators can give rise to beneficial mutations that are inaccessible to nonmutators and haploid mutators