Interactions of fluorophores with complex surfaces and spectroscopic examinations of ancient manuscripts

In the first part of this thesis, it was found by fibre-optic fluorescence spectroscopy, that the greening of fabrics washed in optical brighteners is due to a reabsorption effect. The quantum yield of fluorescence of the optical brighteners OB15, OB36 and OB49 in water are $0.11$, $0.08$ and $0.71$ respectively. Their respective fluorescence natural lifetimes are $6700\pm109$, $5971\pm712$ and $1685\pm22$ ps. In solution, the excited state of OB15 experiences more competing relaxation processes as the solvatochromic shift increases. OB49 displays the opposite trend. A literature cellulose model surface is employed as a cotton mimic for evanescent wave fluorescence studies. Two model greases are similarly developed and used, and a third is presented for future work. These are based on surface-specific reactions with glass substrates, and the doping of a regenerated cellulose film with long chain alcohols. On doped cellulose surfaces, some low quantum yields occur compared to clean cellulose and bulk solution. Photobleaching behaviours are also observed. Both dyes physisorb rigidly to cellulose and grease models. The second part of this thesis identifies the pigment palette of the earliest Northumbrian manuscripts pre- and post-1066, by Raman and diffuse reflectance spectroscopy. It develops a suite of multispectral imaging programs in MATLAB for facile classification of pigments across a page ab initio, using data reduction and colour spaces. Raman and reflectance data are meta-analysed using symmetric permutation to split manuscripts and pigments into groups ab initio. It was also generalised, that the palette of the pre-Hastings selected manuscripts contained vergaut, indigo, orpiment, impure red lead, and copper green pigments, as well as orcein purples. Immediately post-1066 white lead, red ochre, vermilion and lapis lazuli appear in the palette in England, though vergaut and indigo disappear and the red lead used is essentially pure

Thermoplastic active fiber composites for structural actuation

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2002.Includes bibliographical references (v. 2, leaves 267-276).The integration of piezoelectric actuators into a structure can lead to an active structural surface that can adapt by bending or straining to different operational conditions. This can be used to tune desired properties of the active system to their optimal levels. Due to their fast response time, high bandwidth, and the level of force that the actuator can apply, it has been proposed that monolithic piezoelectric materials be used for active structural control. Monolithic piezoelectric materials for planar actuation have several drawbacks including: (a) use of the lower 3-1 actuation for planar actuation, (b) low strain before failure, (c) inability to conform to curved surfaces. Active Fiber Composites (AFCs) have been developed to address some of these shortcomings of monolithic piezoceramic materials. AFCs are thin composite plies comprised of unidirectional piezoelectric fibers imbedded in a thermoset matrix. An electric field is supplied to the fibers by use of an interdigitated electrode pattern adhered to either side of the AFC. The benefits of AFCs include: the interdigital electrode design uses 3-3 actuation offering increased levels of actuation, AFCs allows for anisotropic planar actuation, the AFCs matrix provides load transfer and load distribution, AFCs allows for coverage of curved shapes. A major drawback of the AFCs with PZT-5A fibers is that the level of actuation is 60% lower than that of the 3-3 actuation of monolithic PZT-5A. This is due primarily to a small layer of low dielectric matrix material that is trapped between the electrodes and the high dielectric fibers during manufacturing.(cont.) This dielectric mismatch causes a large voltage drop in the matrix thereby reducing actuation. A method that has been developed to reduce this matrix gap, and thus increasing actuation, is to transfer the electrode pattern onto plastic sheets, and heat and press the sheets around the fibers to make Thermoplastic Active Fiber Composites (tmAFCs). tmAFCs also have simpler processing when compared to AFCs and are reshapeable. The focus of this research is to analyze, manufacture, and test tmAFCs to be used in structural control applications with the goal of producing high quality and high performance actuators.by Christopher T. Dunn.Ph.D

Statistical mechanical theory of equilibrium structure and miscibility of polymer nanocomposites: effects of polymer chemical heterogeneity and architecture, and nanoparticle surface corrugation and softness

Motivated by the persistent interest in different nanoparticles added to various polymer matrices, the Polymer Reference Interaction Site Model (PRISM) theory is extended and applied to study the thermodynamics, statistical structure, and miscibility of diverse polymer nanocomposites (PNCs). Under chemistry-matched conditions and in the absence of interfacial attractions between a spherically smooth nanoparticle and the matrix fluid, the polymer-induced depletion attraction is dominant and induces entropic phase separation. The depletion attraction can be potentially reduced by modifying the nanoparticle surface topography as recently observed in experiments. Two types of surface-modified nanoparticles have been considered in this thesis – (1) spheres with ordered roughness on the surface and (2) soft polymeric nanoparticles with surface fluctuations and fuzziness. Monte Carlo integration and other computational techniques have been developed to compute the effective interactions between such particles. The morphologically diverse particles introduce additional length scales, making the physics non-monotonic, subtle, and rich. The common advantage with using either of the particles is reduced contact aggregation and enhanced miscibility. Optimal surface corrugation and/or particle softness allow monomer penetration resulting in favourable (entropic) mixing. However, high enough degree of corrugation/softness can also result in destabilization by excluding the polymer from its interior. Another route of developing new nanocomposites is by tuning the polymer-particle interfacial chemistry. Prior work has established three states of spatial organization, namely depletion, steric stabilization and bridging, depending upon the effective interfacial attraction strengths. Introducing polymer chemical heterogeneity via the use of AB copolymers offers additional control over the equilibrium structure. Specifically, two types of copolymers are considered – (1) random copolymers (RCP) of disordered sequence and (2) ordered, alternating multiblock copolymers (MBCP). Quantum chemical calculations are combined with the polymer liquid state theory to predict structure and miscibility. The chain connectivity, monomer sequence, copolymer composition and differential wettability results in unique frustration in the system leading to novel states of organization of the polymer around the nanoparticles. In the context of strongly attractive nanoscopic fullerenes, this results in improved miscibility relative to the corresponding homopolymers. For some of the systems studied, maximum dispersion is predicted at an intermediate copolymer composition due to packing correlations and differential wetting effects with favourable comparison to experiments

Towards a circular economy: fabrication and characterization of biodegradable plates from sugarcane waste

Bagasse pulp is a promising material to produce biodegradable plates. Bagasse is the fibrous residue that remains after sugarcane stalks are crushed to extract their juice. It is a renewable resource and is widely available in many countries, making it an attractive alternative to traditional plastic plates. Recent research has shown that biodegradable plates made from Bagasse pulp have several advantages over traditional plastic plates. For example, they are more environmentally friendly because they are made from renewable resources and can be composted after use. Additionally, they are safer for human health because they do not contain harmful chemicals that can leach into food. The production process for Bagasse pulp plates is also relatively simple and cost-effective. Bagasse is first collected and then processed to remove impurities and extract the pulp. The pulp is then molded into the desired shape and dried to form a sturdy plate. Overall, biodegradable plates made from Bagasse pulp are a promising alternative to traditional plastic plates. They are environmentally friendly, safe for human health, and cost-effective to produce. As such, they have the potential to play an important role in reducing plastic waste and promoting sustainable practices. Over the years, the world was not paying strict attention to the impact of rapid growth in plastic use. As a result, uncontrollable volumes of plastic garbage have been released into the environment. Half of all plastic garbage generated worldwide is made up of packaging materials. The purpose of this article is to offer an alternative by creating bioplastic goods that can be produced in various shapes and sizes across various sectors, including food packaging, single-use tableware, and crafts. Products made from bagasse help address the issue of plastic pollution. To find the optimum option for creating bagasse-based biodegradable dinnerware in Egypt and throughout the world, researchers tested various scenarios. The findings show that bagasse pulp may replace plastics in biodegradable packaging. As a result of this value-added utilization of natural fibers, less waste and less of it ends up in landfills. The practical significance of this study is to help advance low-carbon economic solutions and to produce secure bioplastic materials that can replace Styrofoam in tableware and food packaging production

The sedimentary geochemistry of the Moffat Shales : a carbonaceous sequence in the Southern Uplands of Scotland

The Moffat Shales form a 100-metre condensed politic succession of middle Ordovician to Silurian age. 210 samples were collected from several inliers and were dated by contained graptolites. Mineralogy indicates low greenschist facies regional metamorphism. Correlation and multivariate statistical techniques assess the interdependence of the range of major and trace elements analysed, and demonstrate progressive change related to an increasing input of clay. Physiography is deduced as the main factor controlling sedimentation with physico-chemical conditions and the decay of organic matter having important influences. Amino acids were not detected. Minor amounts of alkanes occur, with the highest average yield extracted from sediments at the locality of Hartfell, and lesser amounts from Dobb's Linn and Clanyard Bay. Their abundance and distribution is related to thermal effects of metamorphism and to biodegradation. Metamorphism of kerogen has produced a graphite-d1a structure. Structural ordering is highest in Hartfell kerogens and can be related to the proximity of reverse faults. Optical properties and textural relationships of carbonized graptolite fragments are related to distance from a porphyrite dyke. Samples show increasing reflectivity, refractive and absorptive indices approaching the intrusion from the south. To the north, three discontinuities in the reflectivity trend are attributed to reactivation of reverse faults following intrusion. Dispersion of reflectivity with wavelength shows a rise from blue to red corresponding to that of anthracitic vitrinites. The relationship between optical parameters and temperature indicates that carbonization has occurred at lower temperatures than for the coal-carbon transformation. Contrasts are attributed to initial chemistry, and rank, also to the unknown effects of time and tectonically induced pressure and temperature. Reflectivity of dispersed graptolite fragments is used as a rank index for Moffat Shales cropping out in Luce Bay and near Moffat. At Luce Bay values correspond to those of coals in the low volatile bituminous to anthracitic range with high values occurring near faults. Coalification is related mainly to regional metamorphism; secondary processes, e.g. migration of hot fluids along fractures, may also have operated. At Moffat, comparable rank ranges are distributed along the southeast flank of a Caledonoid trending dome, low values occurring adjacent to the Ettrick Valley Thrust, high at Hartfell. Secondary thermal effects from an unexposed pluton are deduced. Further evidence of enhanced thermal activity in the Hartfell sediments is presented from a study of the electrical conduction of powdered samples. The low resistance of Hartfell samples is attributed to the graphitic nature of the relatively abundant carbonaceous material