The Clinical Application of Cardiac Doppler Ultrasound

The aim of this thesis is to investigate the accuracy of Doppler ultrasound in specific types of cardiac disease and more particularly, to establish its clinical role in cardiovascular diagnosis in conditions where it is likely to confer additional advantage over clinical examination and conventional non-invasive techniques, and thereby have its most major clinical impact

An experimental study of the electric field drift of positrons in solid media and its application to the development of field assisted positron moderators

The primary aim of this work was to investigate the possibility of developing more intense laboratoiy-based slow positron (e+) beams. Conventionally, these are formed by moderating β+ particles in vacuo using metal foils and meshes, e+ thermalise in the metal bulk and a fraction subsequently diffuse to a surface where they are re-emitted with eV energies. It is proposed that a new type of moderator could be developed based on the electric field drift of e+ in semiconductors or insulators. A solution to the diffusion equation is derived, which includes terms describing positron implantation, drift and annihilation. Using published mobility data for Si, the expression is used to estimate the fraction of e+ drifted to a surface or interface. For a 50μm Si crystal cooled to 80K, efficiencies of up to 10% are predicted. It is suggested that the trapping of e+ in defects in the thin contact required to generate the electric field can be reduced by using an epitaxially grown NiSi2 layer on a Si(l 11) substrate. A new method of measuring positron mobility, μ+, using a modified e+ lifetime spectrometer was developed. Changes in the lifetime spectra are related to the electric field drift of e+ from the Si bulk into an annihilation state associated with the Au contact or Au-Si interface. Values of μ calculated from the data are in good agreement with other published measurements. The re-emission of e+ from clean and oxygen exposed Si(111) and Si(l00) surfaces bombarded with β+ particles was measured in ultra high vacuum. The data suggest that the Si(111) and Si(l00) samples studied have positive positron work functions and the small yield of slow e+ measured is attributed to the escape of non-thermal e+ from the surface. Measurements of positron yield versus oxygen exposure are consistent with a changing surface dipole arising from oxygen adsorption. It is concluded that Si is not suitable as a positron moderator and that other materials need to be evaluated to establish whether a practical field assisted moderator can be developed

Evaluation of the Potential of Chitosan Nanoparticles as a Delivery Vehicle for Gentamicin for the treatment of Osteomyelitis

Chitosan nanoparticle delivery systems have potential for enhancing bone healing and addressing osteomyelitis. The objective was to deliver antimicrobial agents capable of preventing or treating osteomyelitis. Each formulation was optimized to achieve desired characteristics in terms of size (ranging from 100 to 400 nm), PDI (less than 0.5), zeta potential (typically negative), and in vitro release profiles for gentamicin. Entrapment percentages varied with gentamicin ranging from 10% to 65%. The chitosan nanoparticles exhibited substantial antimicrobial efficacy, particularly against both P. aeruginosa and MRSA, with zones of inhibition ranging from 13 to 24 mm and complete reduction in colony forming units observed between 3 to 24 hours. These chitosan nanoparticle formulations loaded with antimicrobials hold promise for addressing orthopedic complications

Palladium-catalyzed synthesis of aryl amides through silanoate-mediated hydrolysis of nitriles

A procedure for the formation of aryl amides through the palladium-catalyzed coupling of nitriles and aryl bromides, via the formation of intermediary silanoate derived imidate species is reported. Optimization was undertaken and examples of the process are described that furnish the products in up to 86% isolated yield

Catalytic amidation of unactivated ester derivatives mediated by trifluoroethanol

A catalytic amidation method has been developed, employing 2,2,2-trifluoroethanol to facilitate condensation of unactivated esters and amines, enabling the synthesis of a range of amide products in good to excellent yields. Mechanistic studies indicate the reaction proceeds through a trifluoroethanol-derived active ester intermediate

The British economy [March 1988]

Growth in the British economy continues at a high rate. To date there is little evidence that the collapse of share prices in October has had much effect on consumer demand or on business confidence. The expected decline in the UK growth rate during 1988 is likely to prevent any occurence of the symptoms of overheating which were evident before the events of last October. Further significant deterioration in the balance of payments is to be expected this year. The size of the deterioration and the extent of downward pressure on the exchange rate will in part depend on the degree to which the economy can contain incipient cost inflationary pressures