An investigation into the network structures of eThylene propylene terpolymer elastomers

A series of ethylene propylene terpolymer vulcanizates, prepared by varying termonomer type, cure system, cure time and cure temperature, are characterized by determining the number and type of cross-links present. The termonomers used represent the types currently available in commercial quantities. Characterization is carried out by measuring the C1 constant of the Mooney Rivlin Saunders equation before and after treatment with the chemical probes propane-2-thiol/piperidine and n-hexane thiol/piperidine, thus making it possible to calculate the relative proportions of mono-sulphidic, di-sulphidic and poly- sulphidic cross-links. The cure systems used included both sulphur and peroxide formulations. Specific physical properties are determined for each network and an attempt is made to correlate observed changes in these with variations in network structure. A survey of the economics of each formulation based on a calculated efficiency parameter for each cure system is included. Values of C1 are calculated from compression modulus data after the reliability of the technique when used with ethylene propylene terpolymers had been established. This is carried out by comparing values from both compression and extension stress strain measurements for natural rubber vulcanizates and by assessing the effects of sample dimensions and the degree of swelling. The technique of compression modulus is much more widely applicable than previously thought. The basic structure of an ethylene propylene terpolymer network appears to be independent of the type of cure system used ( sulphur based systems only), the proportions of constituent cross-links being nearly constant.

Fabrication and application of short and novel structure in-fibre Bragg gratings

This thesis presents details on progress made in the fabrication and application of short and novel structure fibre Bragg gratings. The basic theoretical concepts of in-fibre Bragg gratings and photosensitive mechanisms are introduced together with an overview of fabrication methods and applications presented to date. The fabrication of fibre Bragg gratings using a quadrupled Nd:YAG laser is presented and some of the issues of grating fabrication using a fabrication using a phasemask are investigated, including the variation of the separation of the fibre and phasemask, and other alignment issues. A new apodisation technique is presented, enabling the production of gratings with a wide range of spectral profiles. The technique is used to investigate the design and fabrication of length limited fibre Bragg gratings for use in telecommunication systems as filters. Application to devices designed for use in WDM systems is presented. The use of fibre Bragg gratings as high spatial resolution distributed sensors is investigated. Grating sensing arrays comprising very short apodised gratings are demonstrated and Chirped Moiré gratings are implemented as distributed sensors achieving high spatial resolution with miniature point sensing sub-elements. A novel grating sensing element designed to imitate an interferometer is also presented. Finally, the behaviour of gratings fabricated in Boron-Germania-co-doped fibre is investigated, revealing atypical behaviour of the Bragg wavelength during ageing.

Genetics of ocular disease Part 1: Basic concepts: cells, chromosomes and inheritance

This series of articles describes the basic elements of genetics necessary to understand the new advances and the impact these advances will have on the study and treatment of ocular disease. The first article describes the patterns of inheritance of human characteristics, how they are transmitted between the generations and the structure of chromosomes.

Genetics of ocular disease Part 2: Basic concepts: DNA, proteins and genes

This article on the basic concepts of genetics concentrates on doeoxyribose nucleic acid (DNA), the chemical constituent of the genes. First, it will cover how DNA was discovered to be the substance of the genes. Second, the structure of DNA is revealed together with how DNA molecules can make copies of themselves. Third, the nature of the genetic code contained in DNA and how this code directs the manufacture of proteins is described. Finally, the effects of mutation of the genes and how the activities of genes are regulated will be discussed together with the relevance of these concepts to ocular disease.

Ethnic groups as market segments: implications of the demand structure

Ethnic market potential in Britain has not yet been thoroughly researched. Important recent trends have focused mainly on the affective and emotional aspects of ethnicity, and included deliberations on the emergence of a revitalised neo-ethnic consciousness; its identification; politicisation, and the impact on it; of a rising third-world consciousness. This investigation attempts to take cognizance of the consuner demand of the ethnic Asian and West Indian groups, as specific market segments. It discusses the rationale for ethnic segmentation on the underlying premise, that the starting point for all product marketing is a response to perceived market opportunities. On the basis of this approach, the UK laundry detergent and automobile markets were investigated; as being representative of product categories constitutirg extremes along the purchase-search-time continuun in consuner decision-making. Ethnic groups were further analysed for their retail patronage patterns; media usage, and the differential effectiveness of alternative advertisirg strategies. The basic technique of marketing research namely the sample survey, was used with the aim of applying scientific techniques in obtaining information on ethnic groups. The integrated marketirg framework utilised allowed, moreover, for the collection of market research data on the specific issues of ethnic product penetration dealing with retailing, advertising and product promotion. The evidence highlights the fact that the cultural orientations of ethnic groups are instrunental in providing for differential demand structures. It points to the answer that ethnicity is an anchor not only for a deeper sense of identity; but also serves as a focus for the economic interests of ethnic groups. On this basis it is argued here, that since cultural levelling would eventually produce stagnation; current marketing strategies should utilise ethnic diversity as an econanic artifact; which; per se is necessary for profitability and growth; especially in innovative product design and development.

A data structure for improved gp analysis via efficient computation and visualisation of population measures

Population measures for genetic programs are defined and analysed in an attempt to better understand the behaviour of genetic programming. Some measures are simple, but do not provide sufficient insight. The more meaningful ones are complex and take extra computation time. Here we present a unified view on the computation of population measures through an information hypertree (iTree). The iTree allows for a unified and efficient calculation of population measures via a basic tree traversal. © Springer-Verlag 2004.

Basic principles of design and functioning of multifunctional laser diagnostic system for non-invasive medical spectrophotometry

The devising of a general engineering theory of multifunctional diagnostic systems for non-invasive medical spectrophotometry is an important and promising direction of modern biomedical engineering. We aim in this study to formalize in scientific engineering terms objectives for multifunctional laser non-invasive diagnostic system (MLNDS). The structure-functional model as well as a task-function of generalized MLNDS was formulated and developed. The key role of the system software for MLNDS general architecture at steps of ideological-technical designing has been proved. The basic principles of block-modules composition of MLNDS hardware are suggested as well. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Structure of glassy GeO2

The full set of partial structure factors for glassy germania, or GeO2, were accurately measured by using the method of isotopic substitution in neutron diffraction in order to elucidate the nature of the pair correlations for this archetypal strong glass former. The results show that the basic tetrahedral Ge(O-1/2)(4) building blocks share corners with a mean inter-tetrahedral Ge-O-Ge bond angle of 132(2)degrees. The topological and chemical ordering in the resultant network displays two characteristic length scales at distances greater than the nearest neighbour. One of these describes the intermediate range order, and manifests itself by the appearance of a first sharp diffraction peak in the measured diffraction patterns at a scattering vector k(FSDP) approximate to 1.53 angstrom(-1), while the other describes so-called extended range order, and is associated with the principal peak at k(PP) = 2.66( 1) angstrom(-1). We find that there is an interplay between the relative importance of the ordering on these length scales for tetrahedral network forming glasses that is dominated by the extended range ordering with increasing glass fragility. The measured partial structure factors for glassy GeO2 are used to reproduce the total structure factor measured by using high energy x-ray diffraction and the experimental results are also compared to those obtained by using classical and first principles molecular dynamics simulations.

Structure-sensitive biodiesel synthesis over MgO nanocrystals

Size-controlled MgO nanocrystals were synthesised via a simple sol-gel method and their bulk and surface properties characterised by powder XRD, HRTEM and XPS. Small, cubic MgO single crystals, generated by low temperature processing, expose weakly basic (100) surfaces. High temperature annealing transforms these into large, stepped cuboidal nanoparticles of periclase MgO which terminate in more basic (110) and (111) surfaces. The size dependent evolution of surface electronic structure correlates directly with the associated catalytic activity of these MgO nanocrystals towards glyceryl tributyrate transesterification, revealing a pronounced structural preference for (110) and (111) facets. © 2009 The Royal Society of Chemistry.