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The interfacial behaviour of two amphiphillic poly iso-butenyl succinic anhydride (PIBSA)-derived surfactants and the effect of their interaction with various nitrate salts on the stability of a water-in-oil type emulsion has been investigated. The adsorption of the esterification product of PIBSA and coco-diethanolamide (PICDEA) and of Experse-70 (E-70) at the equilibrated aqueous-fuel oil interface was investigated via the measurement of interfacial tension using the ring detachment method.The interfacial pressure of PICDEA decreased in the presence of excess unreacted coco-diethanolamide (CDE) and for both PICDEA and E-70 interfacial pressure decreased with an increase in the length of the poly iso-butenyl (PIB) hydrocarbon tail. Interfacial tension-concentration curves and the Gibbs Equation were used to determine surfactant surface excess concentration and the packing efficiency of the surfactant in the interphase. The double hydrocarbon PICDEA molecule was found to occupy a larger interfacial area than the single hydrocarbon E-70 molecule. The pH of the aqueous phase effects the interfacial activity and nature of, PICDEA and E-70 at the interface. PICDEA is protonated at pH values less than 4.6 and deprotonated at higher pH values. E-70 is neutral at low pH and deprotonated at pH values greater than approximately 2.The effect of sodium, calcium and ferric nitrate salts on the interfacial free energy of the surfactant saturated interface was also determined. The interfacial tension at the E-70 aqueous nitrate interface was dependent on ionic strength alone with a general decrease in interfacial free energy as nitrate concentration was increased. In the case of PICDEA, however, a surfactant-cation orientation effect was observed. The divalent Ca2+ cation attracts two adjacent PICDEA anions resulting in the adverse interaction of hydrocarbon tails in the interphase. This produces an interface with a higher than expected interfacial free energy. The Na+ cation produces an interface with a more energetically stable orientation. PICDEA in the presence of a ferric nitrate solution (pH 1 to 2) is protonated and therefore the univalent nitrate anion forms the counterion layer at the positively charged surfactant interface. Stability studies were carried out on aqueous nitrate salt in diesel emulsions using PICDEA as the stabilizing surfactant. Droplet coalescence rates were determined from droplet size distribution data in the presence of varying concentrations of sodium, calcium and ferric nitrate salts. Droplets were sized microscopically at progressive time intervals and the rate of coalescence determined from the change in droplet concentration with time. Coalescence was found to follow two or more consecutive first order reactions. After an initial period of rapid droplet coalescence, involving small droplets with diameters of 5~m and less, a droplet distribution is attained conducive to a more stable emulsion which then undergoes a slower rate of coalescence involving larger droplets. The effect of the nitrate salt type on the initial droplet coalescence rate (in order of increasing rate) is as follows: Ca2+< Na+< Fe3+. The opposite trend was observed for the slower long term rate of coalescence, i.e. Fe3+< Na+< Ca2+. These trends are explained in terms of the surfactant cation orientation effect, the effect of the droplet's radius of curvature on the potential energy barrier against coalescence and the effect of the droplet distribution of the emulsion system. / Thesis (M.Sc.)-University of Natal, Durban, 1990.

QC 351 A7 no. 85 / A technique is described for suppressing unwanted grain noise in scanned and digitized photographic images. The technique employs the rms granularity statistics of the film to divide, or quantize, the density range of the digital image into distinguishable ranges of density. For Eastman Kodak type 3414 film, the rms granularity statistics determined indicate constant Selwyn granularity for the range of scanning spot diameters from approximately 16 to 4 micrometers, and this result agrees with Kodak data for a 48 micrometer diameter spot. For spots from 16 to 4 micrometers diameter, the rms granularity is also determined to be a function of the square root of diffuse density. The number of distinguishable density levels, required to sup- press the grain noise of the digitally processed image, is found to be directly related to the scanning spot diameter. Finally, evaluation of the resulting digitally processed images indicates that subjective image quality is directly related to the spatial resolution of the image. That is, with the grain noise suppressed, subjective quality is improved by scanning the original image with a smaller diameter spot.

Call number: LD2668 .T4 1959 P38

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2016. / The subject of this current study concerns highly concentrated emulsions of the explosive grade. A distinguishing characteristic of these systems is a high internal to external phase volume ratio. The volume fraction of the aqueous phase of such an emulsion generally far exceeds the close packing limit. Continuous phase of the system is a supersaturated aqueous solution of ammonium nitrate inorganic salt. In combination with high internal phase concentration, this inevitably leads to the destabilisation of the system. The thermodynamic instability of such systems is attributed to two major factors: 1) crystallisation of dispersed phase and 2) coalescence of the individual droplets within the bulk. This poses a significant problem since destabilisation of the bulk emulsion in turn leads to partial or complete loss of sensitivity to detonation of the final product of which highly concentrated emulsion is the base. Since the invention of such types of bulk explosives, a considerable and on-going effort has targeted the improvement of the stability of these systems, with a scope primarily focused on the use of various surfactant agents with different properties as well as stabilising mixtures containing numerous surfactants. In recent years, a new approach has been explored: the stabilisation of highly concentrated emulsions with the use of solid fumed silica nanoparticles. This is a promising new field of study, already being implemented by manufacturers and actively developing. The focus of this present study is to investigate and lay the ground work for further research in the principally new approach towards the stabilisation of highly concentrated emulsions with the use of the polyhedral oligomeric silsesquiozane nanomolecules. These are unique compounds possessing hybrid inorganic-organic structures and properties, and carrying a range of advantages over currently implemented surfactants. As opposed to silica nanoparticles, these compounds are not solid particles but can be regarded as molecular silica. This investigation will focus on the general possibility of implementation of such compounds as stabiliser agents for emulsions in general, and highly concentrated emulsions of the explosive grade in particular, and the resultant effects on the stability. Effects on stability will be investigated both when used solely and in combination with common surfactants. In addition, stability both on shelf and under stress will be investigated within the framework of the study.

The aim of this thesis is to gain new insights into the physics underlying the long-term stability and instability of liquid foams and emulsions in the absence and presence of particles. By using Finite element based and mesoscopic Lattice Boltzmann techniques along with the microfluidic tools at our disposal, we tackled this question using two very different, yet complementary, approaches. In the first part, we went down to the smallest scale of foam, by observing a single bubble where the particle would straddle at interfaces of thin films. This brought a novel understanding to the observation that the torque on the particle is independent of film thickness and was mainly contributed by contact line stresses. We then precisely measured the hydrodynamic and dielectrophoretic interactions of a particle armored bubble treating the bubble as a flat surface and showed that its resistance to the motion was much less for hydrophobic particles compared to other wetting particles while the dielectrophoretic forces were more for hydrophobic particles as the latter protruded more in the oil phase. These findings are of utmost importance when designing particle-stabilized foams and dielectrophoresis-based particle separation techniques because they guide the choice of the particles to use for a particular application. In the second part, we studied the foam at a larger scale, by analyzing the evolution of a large population of identical bubbles produced in microfluidic geometries. This monodisperse foam destabilizes through Ostwald ripening or Coarsening toward a well-known self-similar state. However, we have shown that the transient regime leading to that state is not homogeneous in space. The microfluidic model that we develop predicts how the disorder grows in the foam, which is a valuable asset in applications where an ordered organization of the bubbles is required resisting foam coarsening. Furthermore, multiscale Lattice Boltzmann simulations of emulsion drainage based on frustrated long-range interactions are developed using the images from the microfluidic experiment as the initial phase thus providing a global understanding of emulsion stabilization and drainage dynamics. The key parameters investigated for particle-induced emulsion stabilization were solid particle concentration, particle size, wettability, heterogeneity and particle shape. The resulting emulsion droplets adopted pronounced non-spherical polyhedral shapes with time, indicating a high elasticity of the interface. The stability and the remarkable non-spherical shape of the emulsion droplets stabilized by the particles were features which bear resemblance with foam stabilization of bubbles using hydrophobic particles in flotation processes.

Bicontinuous Pickering emulsions (or bijels) are a relatively new class of novel soft material with many potential industrial applications, including microfluidics, tissue engineering and catalysis. They are typically formed by initiating the spinodal decomposition of a binary liquid mixture in the presence of neutrally-wetting colloidal particles. The particles attach at the liquid-liquid interface and arrest the phase separation by jamming when the concentration of particles approaches the 2D close-packing limit. Predicted by simulations in 2005 and realized in the laboratory in 2007, many aspects of the bijels complex behaviour and properties have remained unexplored. This thesis expands the knowledge of the bijels structural and dynamical properties, while focusing specifically on the role of particle size. The bijels porosity (average interfacial separation L) according to simulations can be controlled by varying the size r and volume fraction ϕ of particles in the system (L ∝ r/ϕ). The inverse scaling of L with ϕ has been verified for one size of particle, but to access smaller values of L (to allow the structure to be used for a wider range of industrial applications) the scaling with r must be tested. Chapter 3 presents the first systematic study of reducing particle size in bijels made with the liquid pair water/lutidine (W/L).We find that a five-fold reduction in r only requires moderate modification to preparation methods (concentrations of reactants during particle synthesis and increased particle sonication time) and in principle allows L values of between 1 & 10 μm to be accessed in the W/L system, where previously 10 μm was the limit. We demonstrate that this reduced lower bound of L can be translated into a lower bound for polymerized bijels also. Unfortunately, reducing particle size even further (in the same way) reveals a law of diminishing returns, as the uptake fraction of particles to the interface also reduces as we reduce particle size. Hence, to reduce lengthscale even further, a new bijel fabrication paradigm is required. Unexpectedly, we find that the temperature quench rate becomes less important for smaller particles (which constitutes a direct material synthesis advantage) and develop a new theoretical framework to take account of this observation. Large particles promote domain pinch-off during the coarsening (due to a larger driving force towards spontaneous curvature) resulting in bijel failure when slow rates are used because the time required to jam is greater than the time required for depercolation. To further probe the bijels structure as a function of particle size and quench rate, and to account for the success/failure scenarios which seem not to depend on L, in Chapter 4 we quantitatively characterize the morphology by measuring distributions of interfacial curvatures. By computing area-averaged quantities to make valid comparisons, we find that smaller particles and faster quench rates produce bijels with greater hyperbolic `open' character, aligning with our understanding of bijel formation gained from Chapter 3. We compare to simulated bijel data and an estimate of the hyperbolicity of the bare liquids undergoing spinodal decomposition, validating the results. In addition, we uncover a time-dependent `mutation' of the curvature distributions when large particles are used, but not when smaller particles or a different liquid pair is used. The mutation appears to correlate with the propensity of the interfacial particles to form a 'monogel', whereby the interfacial particles develop permanent bonds and remain as a 3D percolating network after the interface is removed, although the precise mechanism of the mutation is still to be verified. Following the results from Chapters 3 & 4 it is clear that there are potentially microscopic phenomena in the bijel which result in macroscopic aging and/or a determination of macroscopic structural properties. To investigate further, we use diffusing-wave spectroscopy (a form of light scattering) to probe the microscopic dynamics of the interfacial particles and/or the particle-laden liquid-liquid (L-L) interface. We find that bijel dynamics show two-step (fast/slow) decay behaviour, with the dynamics slowing as the system ages. The two-step decay is very similar to that observed in colloidal gels formed by diffusion-limited cluster aggregation (DLCA), with the initial (fast) decay due to thermally-activated modes of the gel network, and the later (slow) decay due to the relaxation of internal stresses induced by gel syneresis. For a bijel, the internal stresses could be due to syneresis, but could also be due to the jamming transition and/or the monogelation process and/or the forces acting on the L-L interface by the particle layer. In terms of the aging, if the system does not form a monogel, the correlation functions can be (almost) rescaled on to a master curve, indicating the property of universal aging. If the system does monogel, the functions cannot be superimposed, implicating the monogelation process as a potential cause for a different kind of aging in this system. Due to the interesting differences found when changing the size of the stabilizing particles in a bijel, in Chapter 6 we combine large and small particles (making `bimodal' bijels) and look for evidence of particle segregation by size, quantitatively estimate the ratio of particle uptake fractions and measure kinetics. Larger particles are found to adsorb to the interface in twice the quantity as smaller particles, and we find evidence to suggest the preference of larger particles for interfaces curved in only one direction, corroborating results from previous Chapters. Bimodal bijels take longer to jam than an equivalent monomodal (standard) bijel, which is backed up by simulations and highlights the increased ability of the bimodal particles to reorganise at the interface before arriving at the jammed metastable state. Finally, we also observe that the lengthscale of a bimodal bijel can heavily depend on the quench rate used during the preparation, suggesting that quench rate could be used (as well as particle size, volume fraction and contact angle) as a lengthscale control parameter. This thesis adds to the bijel literature, building on previous experimental studies and verifying/contradicting simulations. Particle size is shown to be a pivotal parameter for bijel formation in the W/L system, with particles of size r = 63 nm proving more versatile (markedly less sensitive to quench rate) than particles of size r ≈ 300 nm. However, even-smaller particles (of the same type) do not provide any additional advantage. We also show how the particle size can not only control bijel porosity (according to L ∝ r/ϕ as predicted by simulations) but can control bijel topology (smaller particles result in structures with greater hyperbolic character). By monitoring the bijel structure over time (topology and dynamics) we have shown that the bijel (in some cases) continues to age for at least c. 1 hr (topology) and in all cases c. 1 day (dynamics). For the first time experimentally, we have used a bimodal dispersion of particles to stabilize a W/L bijel and have uncovered a potentially useful new way to produce samples with different porosities from the same starting mixture, by changing the quench rate. The knowledge of the interplay between particle size and quench rate along with the effect on bijel topology will both assist in the scaling up of processes for industrial-level production and inform future strategies for tailoring the structure for specific applications. Future research should focus on several remaining open questions. The volume fraction of r = 63 nm particles in the W/L system should be increased towards 10% and sonication procedures improved to allow good redispersion to test the lower bound of L, which we expect to be around 1 μm. Also, a new W/L fabrication paradigm should be devised which uses sterically-stabilized particles, to continue the reduction of r towards the value used in simulations (5 nm) in order to test the fundamental physics of bijel formation, specifically what value of interfacial attachment energy is needed for long-term stability. Bijel dynamics can be further probed by using a technique which allows a variation in the probe lengthscale (e.g. / differential dynamic microscopy, DDM), as well as developing a better theoretical model for (multiple) light scattering in a bijel system to arrive at the mechanisms responsible for the anomalous aging, and compare to the predictions of monogelation. Finally, higher magnification/resolution microscopy should be used to look for particle segregation on the liquid-liquid interface (as seen in simulations) and to identify in real-space the locations of the changes in Gaussian curvature over time as measured in Chapter 4.

This thesis describes the design and construction of a microfluidic platform for producing stable double emulsions and its application in protein crystallization. Emulsion-based systems has been widely utilized to encapsulate various substances in both industrial applications and fundamental researches. Microfluidics is a promising technique to handle small volumes of liquid and produce such kind of emulsion-based microreactors. / Two different types of microfluidic devices were constructed to generate double emulsions: one was the planar PDMS-based device, and the other was the 3D Glass-Teflon hybrid device. Both devices were demonstrated with the ability to produce a high level of monodispersity in the size distribution of double emulsions with volumes ranging from dozens to hundreds of nanoliter. Compared to the PDMS-based microfluidic devices which are commonly used in the microfluidic field but require sophisticated soft-lithography procedures and selective surface modifications, the Glass-Teflon hybrid microfluidic devices are more competitive in the aspects of low cost, ease of fabrication, reliable performance, and reusability. Double emulsions stored in confined environments were proved to be more stable than that in open environments. With the prolonged lifespan of double emulsions, long-term reactions could be conducted inside the microreactors. In addition, the permeability of the oil shell in double emulsions provided means to precisely control the bio/chemical environments of the core droplets by adjusting the composition of the oil phase or the osmotic pressure differences between the inner and outer phases. The microfluidic platform was established to be a simple and reliable tool for producing stable double emulsion-based microreactors. / We employed the microfluidic platform to perform protein crystallization in the inner aqueous phase of double emulsions.Double emulsions can provide ideal conditions to explore protein crystallization for the advantages of convection-free environment and homogeneous interface. Both vapor diffusion method and microbatch method were implemented in the double emulsion-based approaches using four model proteins to grow crystals successfully. The property of water-oil interface was demonstrated to be a critical factor for nucleation and appropriate surfactants should be chosen to prevent protein adsorption at interface. The results from the volume effect study showed a trend of fewer crystals formed and longer incubation time needed with a reduction in the protein solution volume, suggesting that the nucleation in protein crystallization process can be controlled by changing the volume of protein solutions.Finally, sparse matrix screening was achieved using the double emulsion-based microbatch method. The double emulsion-based approaches for protein crystallization were established to be a promising tool for reducing heterogeneous nucleation and gaining the chance to obtain one crystal in one reactor. / 本論文發展了一種用於產生和存儲穩定雙乳液（double emulsion）的微流控實驗平台，對其製備方法以及把雙乳液用作微型反應容器并在其內核進行蛋白質結晶做了系列的研究和探討。 / 首先，我們製作了兩種製備雙乳液的微流控裝置：第一種是基於聚二甲基硅氧烷（PDMS）的平面型微流控芯片；另一種是由Teflon管、硅膠管和玻璃毛細管組裝而成的三維結構微流控裝置。兩套裝置均可以產生不同納升體積的、具有高單一分散性的雙乳液。製作第一種微流控芯片需要軟光刻及選擇性表面修飾等相關的儀器和步驟；相比之下，第二種微流控裝置在製作消耗的時間和材料，製作簡易性、性能可靠性和可重複使用等方面證明有明顯優勢。通過把雙乳液以低密度存儲在受限容器中，雙乳液的壽命被顯著延長，為將其作為微型反應器提供了可能。此外，雙乳液的中間油層可以起到半透膜功能，可以用調節油相組成及內外水相滲透壓的方式精確控制雙乳液內核溶液的濃度環境。 / 雙乳液的內核是一個沒有對流影響的環境及具有高度均一的界面，可以為蛋白質結晶提供理想空間。我們以製備的雙乳液為微型反應容器，在其內核進行了一系列蛋白質結晶實驗。四種蛋白質分別以類氣相擴散方法（vapor diffusion method）和類微液滴方法（microbatch method）在納升量級進行了結晶實驗，并得到了良好的蛋白質晶體。雙乳液界面會對結晶過程產生明顯影響，在實驗中我們選用了適當的表面活性劑來阻止蛋白質分子的界面吸附。在研究體積效應對蛋白質結晶的影響中，我們發現隨著體積減小，在單一容器內會得到更少數目的晶體，但結晶時間會增加。這為通過控制蛋白質溶液體積來研究成核過程提供可能的途徑。最後，我們把這種基於雙乳液的微型反應容器應用到大數量的結晶條件篩選，通過偏光顯微鏡觀察對比，得到了與普通微液滴方法一致的結晶條件。這種基於雙乳液的微型反應容器為研究蛋白質結晶提供了一種可有效阻止異相成核的新方法。 / Zhu, Deyong. / Thesis Ph.D. Chinese University of Hong Kong 2015. / Includes bibliographical references (leaves 80-90). / Abstracts also in Chinese. / Title from PDF title page (viewed on 05, October, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

No description available.

The aims of this study were to prepare poly (ethylcyanoacrylate) (PECA) nanoparticles on the basis of different types of microemulsions, to investigate the entrapment within and release of a bioactive from these particles and to establish a set of delivery systems with varying entrapment and release characteristics, thereby giving the formulator the opportunity of a more tailor-made approach in the development of a delivery system. Furthermore the scale up of particle preparation and the possible enhancement of the immunogenic properties of PECA particles by incorporation of the adjuvant Quil A was investigated. Methods: Four phase triangles were established and microemulsion samples, used as a template to prepare nanoparticles, were characterised by viscosity and conductivity measurements, polarising light microscopy, freeze fracture transmission electron microscopy (TEM), cryo field emission electron microscopy (cryo FESEM) and self-diffusion NMR to determine their microemulsion type (droplet, bicontinuous, solution type). PECA nanoparticles were prepared from different types of microemulsions by interfacial polymerisation. Particle size, polydispersity index (PI) and [zeta]-potential were measured by photon correlation spectroscopy and electrophoretic mobility respectively. Normal scanning electron microscopy (SEM) and cryo FESEM were used to visualise particles. Fluorescently labelled ovalbumin (FITC-OVA) was used as a model protein/antigen and entrapment within and release from nanoparticles was investigated. To scale up nanoparticle preparation an instrumental set-up with reactor, peristaltic pump and stirrer was used. A 2⁷ fractional factorial study was designed to observe possible factors or their interactions that could influence particle formation under scale up conditions. For an immunological study freeze dried formulations of PECA nanoparticles, having FITC-OVA and Quil A entrapped, were prepared, and activation and uptake of formulations by murine bone marrow derived dendritic cells (DCs) and T cells in vitro were monitored. Results: Results obtained from the measurements described above, for formulations from the four different phase triangles, indicated that microemulsions of w/o droplet, bicontinuous or solution type could be formed. It was possible to prepare PECA nanoparticles from all of the different types of microemulsions. Particles had an average size of 265 nm � 24, with an average PI of 0.18 � 0.05 and an average negative [zeta]-potential of -17 mV � -5. Particle size, PI and [zeta]-potential were not influenced by the type of microemulsion that was used as a polymerisation template. Entrapment and release were however influenced by the type of microemulsion and although entrapment of FITC-OVA was generally high for PECA particles, it was highest for particles prepared from a droplet type microemulsion. Entrapment could also be increased by increasing amounts of monomer. The rate of release was dependent on the amount of monomer used for polymerisation and the type of microemulsion used for particle preparation, with nanoparticles prepared from a w/o droplet type microemulsion showing the slowest release. Furthermore it was shown that particle preparation could be scaled-up with the instrumental set-up used in this study, but conditions need to be refined as the average particle size and polydispersity index were considerably larger (441 nm � 101, 0.68 � 0.14) when compared to particles prepared by the beaker-pipette method (see above). The adjuvant Quil A could efficiently be entrapped into PECA nanoparticles together with FITC-OVA. Incubation of DCs and T cells with the various formulations did, however, not result in increased uptake or activation. Conclusions: PECA nanoparticles with high entrapment efficiency of antigen and adjuvant can be prepared from different types of microemulsions. Particles show different rates of entrapment and release depending on the type of microemulsion used as a polymerisation template, possibly because two different types of nanoparticles form. Nanocapsules are believed to form on the basis of droplet type microemulsions and nanospheres form on the basis of bicontinuous and solution type microemulsions. Freeze dried formulations of PECA nanoparticles, containing Quil A and FITC-OVA, were not able to induce an immune response, which might be due to charge repulsion effects between the negatively charged PECA nanoparticles and the negatively charged surface of dendritic cells. Moreover, no adjuvant effect of Quil A was apparent, perhaps caused by total encapsulation of the compound into the particle matrix with no active groups extending out displaying adjuvanticity.