The quenching of the [Ru(bipy)3]2+ by Cu2L2+ was studied and the data were plotted with the Stern-Volmer equation. The plot showed a break and was divided into 2 regions, <0.5 and >0.5 Cu2L2+: [Ru(bipy)3]2+ molar ratio. Quenching above the 0.5 Cu2L2+: [Ru(bipy)3]2+ molar ratio was slower (330 x 10-6 M-1s-1) than the quenching rate reaction below 0.5 ratio (387 x 10-6 M-1s-1). With Cu2L2+ being a dimeric complex the break and differences in the quenching reaction rates can be explained in terms of the stoichiometry. When the Cu2L2+: [Ru(bipy)3]2+ ratio is < 0.5, then each [Ru(bipy)3]2+ can interact with 1 Cu2L2+ dimer. At 0.5 then there is exactly a 1:1 ratio RuII : CuII. Above the 0.5 ratio the [Ru(bipy)3]2+ can interact with maybe only one of the Cu2L2+'s in the dimer, or with a [Ru(bipy)3]2+: Cu2L2+ unit, so the quenching is less efficient.

Luminescence techniques are sensitive, selective, and widely used in analysis. Luminescence intensity is attenuated by quenchers. This research has focused on the use of surfactants such as CTAB, SDS, and TX-100 singly or together with TiO2 nanoparticles to evaluate their individual and combined effects on some fluorescent aromatic compounds such as pyrene, fluoranthene, anthracene, phenanthrene, and carbazole. Rutile phase TiO2 was synthesized using the low temperature sol-gel method. Carbazole and phenanthrene were severely quenched by all surfactants singly or in combination with TiO2. Anthracene and fluoranthene showed some enhancement in their luminescence intensity. The most dramatic effect was observed on the fluorescence intensity of pyrene. Pyrene showed enhanced fluorescence after degassing the solution alone or with the addition of the surfactants alone or in combination with TiO2 after degassing. These results showed that surfactants and TiO2 nanoparticles either singly or in combination should be useful for analysis employing luminescence techniques.

No description available.

Bioactive compounds, such as curcumin, lutein, coenzyme Q10, β-carotene, cholecalciferol, astaxanthin, and β-sitosterol, have antioxidant and anti-inflammatory properties that promote health, but their low solubility, fast metabolism, and degradation have made it difficult to fully harness their potential. Encapsulation techniques, such as nano and microencapsulation using food-based biopolymers, have been employed to address these challenges. However, research efforts in protein-based delivery have mainly focused on encapsulation without considering structural, physicochemical, and matrix compatibility, which is tedious, unsustainable, and not cost-effective. Hence, this thesis reports the structural basis of guest-host interaction in the gastrointestinal delivery of lipophilic bioactive compounds using protein-based vehicles. This research employed fluorescence quenching techniques to estimate the influence of protein modification, fractionation and ionic strength on the nature and strength of interactions between protein and bioactive compounds. Morphological examination was carried out with transmission electron microscopy, confocal and widefield fluorescence microscopy whereas the sizes of the nano and micro-complexes was measured with dynamic light scattering techniques. Thermal stability was measured with differential scanning calorimetry and functional group characterization done with Fourier Transform infrared spectroscopy. Encapsulation efficiency was estimated by UV-Visible spectroscopy whereas in vitro bioactive compound release study was carried out in simulated salivary, gastric and intestinal fluids. Cytotoxicity assessment was estimated by calcein leakage assay. The study showed that protein modification affects the strength of protein-curcumin interaction and encapsulation efficiency. Pea protein succinylation increased electrostatic interaction with chitosan but decreased protein-curcumin interaction. Pea glutelin, albumin and globulin fractions showed different binding strengths with curcumin and the protein hydrophobicity and encapsulation efficiency correlated positively with the binding strength. The study also investigated the impact of bioactive compound lipophilicity and physiological ionic strength on the interaction between protein and bioactive compound. Lipophilicity influenced the strength of protein-bioactive compound interaction, while ionic strength changed the mode of interaction from static to static-dynamic quenching. The morphology of the nano and micro complexes formed with protein varied depending on the nature of encapsulated bioactive compound. Finally, bio-nano interaction involving giant unilamellar vesicles and curcumin-loaded pea protein of various surface functionalities as model biomembrane and nanoparticles respectively, was investigated. The result showed that while the protein/chitosan shell stabilizes bioactive compounds from degradation, the bioactive compound modulates their interaction with biomembrane. Overall, this work has demonstrated that for a rational design of protein-based nano/micro-encapsulation system, it is essential to consider the influence of the structural and physicochemical properties of proteins and bioactive compounds, stabilizing intermolecular forces, ionic strength of the environment, lipophilicity of the bioactive compounds, mechanism of release and modulation of cytotoxicity by bioactive compound. For instance, in high ionic strength solution, the stoichiometric ratio between protein carrier and bioactive compounds influences the stability of the complex. Balancing the intermolecular forces in the shell and core of bilayer complexes is essential for the stability of nanocomplexes and the presence of bioactive compound stabilizes the macromolecular carrier to minimal biomembrane disruption.

The Enåsen gold deposit is located in Gävleborg county in central Sweden. Mining operations at Enåsen took place from 1984 to 1991 with Au as the main target for exploitation. The deposit has been interpreted as a metamorphosed Palaeoproterozoic analogue to near-recent epithermal Au mineralisations of a high sulphidation type. Its present mineralogy, textural-structural features, and morphology have been suggested to be the result of a combination of later deformation and regional Svecokarelian metamorphism at upper amphibolite to granulite facies conditions of the original epithermal deposit and it’s hydrothermally altered host rock. The main ore body now consists of a mineralised sillimanite quartzite gneiss. The aim of the project was to characterise the ore mineralogy, petrography and its paragenesis, evaluate the potential of Enåsen in terms of critical metals, and to test a hypothesis of partial ore melting.Among the most frequent ore minerals in the deposit are pyrite, chalcopyrite, pyrrhotite, bornite and tetrahedrite-tennantite, with variable but less abundant sulphides including covellite, digenite, mawsonite, stannite, arsenopyrite, cobaltite, galena, marcasite, sphalerite and pentlandite. Additionally, native gold, Se-bearing tellurobismuthite, hessite, tsumoite, pilsenite, rickardite, vulcanite, altaite, molybdenite, frohbergite, montbrayite, tellurantimony, löllingite and tellurbismuthantimony. While not an ore mineral here, rutile occurs abundantly. The ore mineral assemblages have seemingly at least partially melted. This is evidenced by failed quenching textures in the form of abundant multi-scale symplectites, potential sharp dihedral angles, localised concentrations of low melting point chalcophile elements (LMCE) + Au and Ag and arrays of multiphase sulphide/sulphosalt ± gold inclusions, as well as available mineral stability data considering that the ore assemblages have been subjected to upper amphibolite/granulite facies conditions followed by ductile and brittle deformation stages. Some ore mineral relationships have been described. Further studies would be required for a full paragenesis. The potential of Enåsen type deposits in terms of critical or near critical metals and semi-metals is likely to be as biproduct extraction in a mining operation aimed at gold. The most relevant element is likely to be bismuth, followed by tellurium and antimony.

No description available.

No description available.

No description available.

No description available.

Reverse Osmosis (RO) filtration is capable of producing high quality drinking water with an ultra-low nutrient level. Therefore, a very low bacterial growth potential (BGP). BGP is a key bioassay to evaluate microbial quality and the biological stability of drinking water. Current methods to assess BGP in drinking water need to be adapted to the wide variety of water types due to results could highly vary from each, providing unreliable insights to the biological stability of the assessed water. This study evaluates the application of an FCM-based BGP assay for RO produced chlorinated drinking water. The approach combines (i) the standardization of a quenching agent concentration, (ii) the impact of sample pre-treatment such as filtration and pasteurization on the BGP of RO produced chlorinated water, (iii) the effect of different inoculums (an indigenous community and a mixture with bottled water) on the bacterial growth and their longevity after being stored, (iv) the use of BGP to assess the performance of carbon filters in removing chlorine and (v) the use of BGP to assess the effect of the addition of magnesium on bacterial growth. The results showed that high concentrations of sodium metabisulphite (> 7.5 mg/L) decrease the pH levels of the water,thus, inhibiting bacterial growth. Filtration had a significant effect on BGP values (2.62 x10^5 intact cells/mL) in comparison to pasteurization (9.02 x 10^4 intact cells/mL), when compared to the control. Using a mixture of water types as inoculum might provide a better insight to bacterial growth potential in water due to a higher consumption of nutrients. BGP demonstrated to be a sensitive tool to test the performance of carbonfilters applied to remove chlorine and its applicability to evaluate the biological stability of RO produced chlorinated drinking water. The concentrations of magnesium chloride tested in this study did not have a significant effect on cell numbers.