There are two focal points of this thesis: the acoustics of seagrass and the acoustical properties of encapsulated bubbles for underwater noise abatement. The acoustical properties of seagrass have applications in mine hunting, shallow water sonar, and environmental acoustic remote sensing. In order to optimize these applications, a predictive model of acoustic propagation in seagrass beds is sought. Previous laboratory research has indicated that the tissue acoustic properties of seagrass as well as the tissue physical structure and entrained air masses inside the leaves contribute to the overall acoustic behavior. The present research utilized a glass laboratory resonance tube to find the low frequency (1 kHz-4 kHz) acoustic compressibility of two species of seagrass, Thalassia testidinum and Halodule wrightii. By using a mixture of finely divided seagrass tissue suspended in seawater, the bulk moduli of the seagrass species were extracted. In the second section, encapsulated bubbles were analyzed as a method of abating underwater anthropogenic noise sources, since these sources, including marine piledriving and oil and gas exploration and production, pose potential harmful effects to marine life. Previous research, which used an array of rubber-shelled encapsulated bubbles, found the attenuation from these bubbles in be in close accordance with an existing encapsulated bubble model. Experiments were performed in a small laboratory resonance tank, a large outdoor acoustic tank, and at Lake Travis Test Station (LTTS) in order to determine the effects of varying an encapsulated bubble's wall thickness and fill material on bubble resonance frequency and damping. Results found that increasing the wall thickness tended to increase the balloon resonance frequencies measured in the small tank, which was strongly correlated to the frequency of maximum noise reduction in the large outdoor test tank and LTTS tests. The addition of polyester fibers and aluminum wool as fill materials decreased both the resonance frequency and quality factor, whereas helium-filled filled encapsulated bubbles had an increased resonance frequency but decreased quality factor as compared with air-filled bubbles. The resonance quality factor and void fraction further proved to affect the noise reduction near bubble resonance in the outdoor acoustic tank and LTTS tests. The measurements made with a single bubble in a small laboratory tank were correlated to measurements with a full-size system composed of many bubbles operating in open water. / text

This thesis reports on the synthesis and characterization of PtNi dendrimer-encapsulated nanoparticles (DENs) containing on average 147 atoms. This is significant because PtNi DENs have not yet been reported. The DENs were prepared by first complexation of Pt²⁺ to the interior tertiary amines of a sixth-generation, hydroxyl-terminated (G6-OH) poly(amidoamine) (PAMAM) dendrimer template, followed by chemical reduction in the presence of free Ni²⁺ to yield PtNi DENs. UV-visible (UV-vis) absorbance measurements exhibit a broad, monotonically decreasing band characteristic of nanoparticle formation. Upon dialysis in both H₂ and O₂ this band is observed to decrease in absorbance. Transmission electron microscopy (TEM) studies indicate that particles have been synthesized and are 1.8 + 0.2 nm before dialysis and 1.9 + 0.2 nm after dialysis under H₂. Results obtained from X-ray photoelectron spectroscopy (XPS) show that Pt is present and the Pt(4f7/2) binding energy is observed at 72.0 eV before dialysis and 71.5 eV after dialysis under H₂. XPS shows that Ni is present and the Ni(2p3/2) binding energy is centered at 857.0 eV before dialysis and 856.6 eV after dialysis under H₂. Finally, oxidative electrochemical stripping is observed at 1.07 V (vs NHE) for PtNi DENs immobilized on glassy carbon electrodes (GCE) and is tentatively assigned to Ni. / text

>Magister Scientiae - MSc / This study describes the synthesis and characterisation of Cu(II) and V(IV) complexes of tri- and quadridentate ligands L1 and L2 formed by condensation of ethylenediamine with acetylacetonate in 1:1 and 1:2 molar ratio, respectively. Encapsulation of these metal complexes in the nanocage of zoilite-Y generates new heterogeneous catalysts. These catalysts were synthesized employing the flexible ligand method encapsulation technique.The structures of these encapsulated complexes were established on the basis of various physico-chemical and spectroscopic studies. The results indicated that the complexes did not hinder or modify the framework or structure of the zeolite, confirming successful immobilization of Schiff-bases through the voids of zeolite Y.These encapsulated complexes were screened as heterogeneous catalysts for various oxidation reactions such as such as phenol, benzene, styrene and cyclohexene using a green oxidant (H2O2). For comparison, the corresponding neat complexes were screened as potential homogeneous catalysts for these oxidation reactions. The results proved that the corresponding homogeneous systems described here represent an efficient and inexpensive method for oxidation of phenol, benzene, styrene and cyclohexene, having advantages over heterogeneous catalysis are its high activity and selectivity and short reaction times. Its major problem is its industrial application regarding principally the separation of the catalyst from the products.The size of the substrate has a significant effect on the conversion by encapsulated complexes such as in styrene oxidation. Therefore, it was established that steric effects of the substrates play a critical role in the poor reactive nature of the encapsulated complexes.In general, the percentage conversion decreased upon encapsulation of complexes in zeolite Y. All catalysts studied proved to be potential catalysts for the various oxidation reactions.It has been shown in this study that encapsulation can effectively improve product selectivity but requires a longer reaction time in most cases for maximum activity. Furthermore, oxovanadium complexes were more reactive than copper-based catalysts in all oxidation reactions tested in this study.A reaction mechanism study revealed that the activity of the encapsulated and neat complexes occurs through either formation of peroxovanadium (V) or hydroperoxidecopper(II) intermediate species.The studies in this thesis, therefore, conclude that the Cu(II) and V(IV) complexes encapsulated in Y-zeolite are active heterogeneous catalysts for the selective oxidation of various substrates. Encapsulation of the metal complexes in the super cages (-cages) of the zeolite matrix has the advantages of solid heterogeneous catalysts of easy separation and handling, ruggedness, thermostability, reusability (regeneration of the deactivated catalysts) as well as share many advantageous features of homogeneous catalysts.

Dendrimer-encapsulated nanoparticles (DENs) were prepared, characterized, and immobilized on solid surfaces. The resulting films were applied as electrocatalysts for the oxygen reduction reaction (ORR). First, the synthesis, physical and chemical properties, and stability of Pd DENs prepared within poly(amidoamine) (PAMAM) dendrimers were studied in aqueous solution. In this part of the study, the following new findings were reported: (1) the maximum Pd ion loading in the dendrimer was correlated to the number of interior amines available for complexation; (2) Pd DENs could be synthesized within amine-terminated Pd DENs by controlling the solution pH; (3) the oxidative stability of Pd DENs was significantly improved by removing solution-phase impurities; (4) exposure to hydrogen gas reversibly converts partially oxidized Pd DENs back to the zerovalent state. Second, Pt and Pd DENs were prepared using amine-terminated PAMAM dendrimers, and then the free amine groups on the periphery were used to immobilize Pt and Pd DENs onto Au surfaces via an intermediate self-assembled monolayer. The resulting DEN films were more robust and had higher coverages of DENs compared to the DEN films prepared via physisorption. Third, Pt DENs were prepared and immobilized on glassy carbon electrodes using an electrochemical coupling method. The resulting films were electrochemically active for the ORR. These electrocatalytic monolayers were also robust, surviving up to 50 consecutive electrochemical scans for ORR and sonication in acid solution with no significant change in activity. Finally, PtPd bimetallic nanoparticles containing an average of 180 atoms (~1.8 nm in diameter) and composed of seven different Pt:Pd ratios were prepared within sixth-generation, hydroxyl-terminated PAMAM dendrimers. Transmission electron microscopy and single-particle energy dispersive spectroscopy confirmed the sizes and compositions of the particles. These DENs were immobilized on glassy carbon electrodes, and their electrocatalytic properties were evaluated as a function of composition using cyclic voltammetry and rotating disk voltammetry. The results showed that the maximum rate for the ORR occurs at a Pt:Pd ratio of 5:1, which corresponds to a relative mass activity enhancement of 2.5 compared to otherwise identical monometallic Pt nanoparticles.

This thesis studies the reliability issues of encapsulated cholesteric LCD, and analyzes the defective pixel. Adjusting fabrication process parameters, we change the thickness of the buffer layer and absorption layer to explore the influence of different boundaries to CLC. It is found that the buffer layer can provide a good protection. When the buffer layer is getting thicker, the less the defective pixels appear, and the absorption layer cannot induce defect. The reflection band of the ITRI¡¦s encapsulated CLCs blue shifts to UV band and then become defective pixel. When CLCs exposed to the atmosphere with large area, the reflected color will be shifted. The shift of reflection band is due to CLC¡¦s inherent properties. Different kind of CLC has different properties, and we found the reflection band of ITRI¡¦s CLC is blue shift and the nematic E48 with chiral dopant R811 is red. Mixing different features of CLCs with appropriate proportion can reduce the color shift. In conclusion, mixing different characteristics CLCs with appropriate proportion and providing good protection to encapsulated CLC, we can reduce CLC¡¦s color shift and restrain the defective pixel.

Dendrimer-encapsulated nanoparticles (DENs) were prepared, characterized, and immobilized on solid surfaces. The resulting films were applied as electrocatalysts for the oxygen reduction reaction (ORR). First, the synthesis, physical and chemical properties, and stability of Pd DENs prepared within poly(amidoamine) (PAMAM) dendrimers were studied in aqueous solution. In this part of the study, the following new findings were reported: (1) the maximum Pd ion loading in the dendrimer was correlated to the number of interior amines available for complexation; (2) Pd DENs could be synthesized within amine-terminated Pd DENs by controlling the solution pH; (3) the oxidative stability of Pd DENs was significantly improved by removing solution-phase impurities; (4) exposure to hydrogen gas reversibly converts partially oxidized Pd DENs back to the zerovalent state. Second, Pt and Pd DENs were prepared using amine-terminated PAMAM dendrimers, and then the free amine groups on the periphery were used to immobilize Pt and Pd DENs onto Au surfaces via an intermediate self-assembled monolayer. The resulting DEN films were more robust and had higher coverages of DENs compared to the DEN films prepared via physisorption. Third, Pt DENs were prepared and immobilized on glassy carbon electrodes using an electrochemical coupling method. The resulting films were electrochemically active for the ORR. These electrocatalytic monolayers were also robust, surviving up to 50 consecutive electrochemical scans for ORR and sonication in acid solution with no significant change in activity. Finally, PtPd bimetallic nanoparticles containing an average of 180 atoms (~1.8 nm in diameter) and composed of seven different Pt:Pd ratios were prepared within sixth-generation, hydroxyl-terminated PAMAM dendrimers. Transmission electron microscopy and single-particle energy dispersive spectroscopy confirmed the sizes and compositions of the particles. These DENs were immobilized on glassy carbon electrodes, and their electrocatalytic properties were evaluated as a function of composition using cyclic voltammetry and rotating disk voltammetry. The results showed that the maximum rate for the ORR occurs at a Pt:Pd ratio of 5:1, which corresponds to a relative mass activity enhancement of 2.5 compared to otherwise identical monometallic Pt nanoparticles.

abstract: The increasing pervasiveness of infections caused by multidrug-resistant bacteria (MDR) is a major global health issue that has been further exacerbated by the dearth of antibiotics developed over the past 40 years. Drug-resistant bacteria have led to significant morbidity and mortality, and ever-increasing antibiotic resistance threatens to reverse many of the medical advances enabled by antibiotics over the last 40 years. The traditional strategy for combating these superbugs involves the development of new antibiotics. Yet, only two new classes of antibiotics have been introduced to the clinic over the past two decades, and both failed to combat broad spectrum gram-negative bacteria. This situation demands alternative strategies to combat drug-resistant superbugs. Herein, these dissertation reports the development of potent antibacterials based on biomolecule-encapsulated two-dimensional inorganic materials, which combat multidrug-resistant bacteria using alternative mechanisms of strong physical interactions with bacterial cell membrane. These systems successfully eliminate all members of the ‘Superbugs’ set of pathogenic bacteria, which are known for developing antibiotic resistance, providing an alternative to the limited ‘one bug-one drug’ approach that is conventionally used. Furthermore, these systems demonstrate a multimodal antibacterial killing mechanism that induces outer membrane destabilization, unregulated ion movement across the membranes, induction of oxidative stress, and finally apoptotic-like cell death. In addition, a peptide-encapsulation of the two-dimensional material successfully eliminated biofilms and persisters at micromolar concentrations. Overall, these novel systems have great potential as next-generation antimicrobial agents for eradication of broad spectrum multidrug-resistant bacteria. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2019

Microorganisms have been known to play a major role in human health since early times. The ingestion of microorganisms as probiotics to restore and/or maintain health is a widely accepted and common practice. The challenge in industry is to ensure viability of probiotics until their ingestion to their site of action, the colon, for health benefits to be realised. Microencapsulation is one of the techniques used to protect probiotic bacteria and ensure viability. A method that does not involve the use of extreme temperatures and/or solvents which would otherwise adversely affect viable cells was developed and patented. The method is solventless and is based on complexation of Food and Drug Administration-approved polymers, poly (vinylpyrrolidone) and poly (vinylacetate-co-crotonic acid) in supercritical carbon dioxide. The use of this method of encapsulation was found to be suitable in target release in earlier studies. Microparticles produced were found to have pH-dependent swellability, protecting bioactives, in this case probiotic bifidobacteria, in acid (simulated gastric acid) and only releasing them in an alkaline environment (simulated intestinal fluid). Further studies were, however, needed to investigate the suitability of the microparticles for food and pharmaceutical applications. The current study therefore aimed to characterize these microparticles in terms of size range, distribution of bacteria within the microparticles, and particle size distribution. The average size of the Bifidobacterium lactis Bb12-encapsulating microparticles was found to be within the acceptable size in food applications. High encapsulation efficiency was obtained, with live bacteria distributed evenly within the microparticles, demonstrating the potential of the microparticles to deliver high numbers of probiotic cultures as required for this type of microorganisms to deliver purpoted benefits to the consumer. Probiotic products are normally kept under refrigerated storage, yet the viability of bacterial cells still decreases. An additional benefit of encapsulation within microparticles would be protection of the encapsulated probiotics from the detrimental factors to which the probiotic products are exposed during storage. In order to investigate this for the microparticles in this study, the shelf life of encapsulated B. lactis Bb 12 powder stored in glass vials was investigated. High temperatures were used for accelerated shelf life studies. Encapsulated B. lactis Bb 12 maintained the viable levels above the therapeutic minimum for the duration of the study (12 weeks), which was 7 weeks more than was the case with unencapsulated probiotic. Thus the microparticles provided protection to the probiotic cultures at temperatures much higher than those normally used for storage of probiotic products. These results further indicate the possibility for storage of the B. lactis Bb12 encapsulated in the tested microparticles, at ambient temperatures for at least two months, without drastic loss of culture viability. Research has recently focused on the development of probiotic foods other than dairy and dairy-based foods. This has been necessitated by increasing vegetarian lifestyle and concerns of allergenicity. A maize-based traditional fermented beverage, mageu, was investigated for use as a vehicle for probiotic delivery. Although no significant difference was noted between survival of encapsulated and unencapsulated probiotic was noted, pH decrease in mageu with encapsulated B. lactis Bb 12 was less than with unencapsulated cells. This suggested that encapsulation would ensure that metabolites produced by encapsulated probiotics, if any, would not negatively affect a product in which they are incorporated. Further studies may be needed for investigation of the effect of the encapsulating microparticles in traditional fermented non-dairy products, using more acid-sensitive probiotic strains as the test strain used in the current study is well-known for its inherent resistance to acidity. This study filled gaps in knowledge in terms of the characteristics of microparticles produced using supercritical technology. The main highlights of the research findings were that the microparticles were suitable for food applications, improved probiotic viability under nonrefrigerated temperatures, and delayed browning of the probiotic powder and minimized drop in pH of the fermented product containing the probiotic encapsulated within. The results showed that microparticles encapsulating B. lactis Bb 12 are appropriate to consumers in areas where refrigeration is absent. Furthermore, the study showed that mageu is a suitable alternative vehicle to dairy-based products, for delivery of probiotic B. lactis Bb 12. This possibility extends accessibility of probiotic products to consumers who do not take dairy products for various reasons. There is also a potential increase of probiotic products on the market. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Microbiology and Plant Pathology / unrestricted

BACKGROUND:Serum protein acidic and rich in cysteine (SPARC) is a matricellular secreted glycoprotein that performs several cellular functions and has been implicated in tumorigenesis in a variety of tumor types. The chemotherapeutic agent nanoparticle albumin-encapsulated (NAB)-paclitaxel has been postulated to exploit SPARC expression to target neoplastic cells. SPARC's role, and potentially the role of NAB-paclitaxel, in the highly heterogeneous class of soft-tissue sarcomas (STS) has not been investigated. Our objective was to explore the pattern of SPARC expression and its prognostic significance in STS.METHODS:27 tissue specimens representing various STS histologies were stained for SPARC expression by immunohistochemistry (IHC). Staining intensity was scored blindly. Survival was determined from patients' medical records and analyzed using Kaplan-Meier and log-rank with respect to SPARC expression level.RESULTS:Elevated SPARC expression was observed in 15/27 (56%) specimens. Overall patient survival segregated strongly based on levels of SPARC expression. Patients who expressed low-to-moderate levels of SPARC exhibited median survival of 22.1months, while the median survival of patients with moderate-to-high expression levels was 4.4months (log rank / p=0.0016).CONCLUSIONS:SPARC expression is elevated in a significant proportion of STS specimens analyzed in this study, but it does not appear to correlate with specific STS histologies. Given our limited sample size, we cannot draw definitive conclusions regarding association of SPARC with STS subtype. Overall survival segregates strongly by degree of SPARC expression, with elevated expression being adverse. If validated in a larger study, our results suggest that trials in STS with agents potentially targeting SPARC, such as NAB-paclitaxel, should be stratified by SPARC expression level.

This study deals with solidification and melting of some typical encapsulated ice thermal energy storage geometries. Using ANSYS GAMBIT and FLUENT 6.0 software, HTF fluid motion past encapsulated water (ice) geometries, varying HTF flow rates and inlet temperatures are analyzed. The main source of irreversibility was from entropy generation accompanying phase change, although viscous dissipation losses were included. Energy efficiencies were well over 99% for all cases, while exergy efficiencies ranged from 70% to 92%. By far, the most influential variable was the inlet HTF temperature; higher efficiencies resulted from inlet HTF temperatures closer to the solidification temperature of water. / UOIT