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The effects of ionizing radiation on solutions of (1) sodium alginate, (2) alginate gels (wet and dry), (3) xanthan gum, (4), locust bean gum (LBG) and (5) carboxymethyl cellulose (CMC), have been investigated. Problems arise in the radiation sterilization of these gums (either as a solution or gel) due to reduction in their viscosity and the gel strength, caused by the high doses (25kGy) commonly used for the purpose of sterilization. The alginates used here were manugel DMB, manugel DPB and manucol DMF. The irradiations were carried out using 'Co-ry-source and the gels and solutions were analysed by measurement of their apparent viscosities using a Brookfield viscometer L.V.T. The data shows that 2% solutions of the sodium salt of the three alginates used here are all pseudoplastic. There is a rapid decrease in viscosity of solutions irradiated up to a dose of 0.5kGy, and the initial rate of viscosity decrease is unaffected by the presence or absence of air. Inclusion of mannitol at high concentration (15%) could, at least partially, protect the alginate solutions degradation by scavenging -OH radicals. The possibility of using 60Co-7-radiation to sterilize alginate gels (wet gels) was also studied. Gels of this type have potential use of wound care. Those prepared here could bend easily. Irradiated to 25 kGy, the gels readily crack by becoming more brittle, are easily squashed and lose water. Inclusion of mannitol improved the quality of the gels and again indicates its protective role in these systems. When alginate solutions containing mannitol and the gelling agents 5-gluconolactone and calcium orthophosphate were irradiated separately and then mixed, gels were formed, indicating that pre-sterilization of the components by irradiation is a feasible method of preparation of sterile gels. Gels that were concentrated (dry) by water evaporation were more stable to radiation (25 kGy). The gels that had the greatest capability to take up saline and to be manipulated most easily (both before and after irradiation) were those that contained initially 2% alginate and 5% mannitol, and dried to a quarter of the original weight (ie. the gel now contained 8% alginate and 20% mannitol). These gels were clear and pliable and after irradiation to 30 kGy remain stable in saline for up to 24 hours. The effect of ionizing radiation on xanthan and LBG solutions are also studied. The initial studies indicated that these solutions were also pseudoplastic. Irradiation of xanthan gum solutions caused a rapid initial decrease in apparent viscosity. t-Butanol had some protective effect on xanthan-LBG and xanthan-NaC1 solutions. Addition of mannitol (20%) to xanthan gum solutions again only partially protects the solutions. The solutions with highest apparent viscosity were those prepared by mixing equal volumes of solutions of LBG 1%, mannitol (20%) and ascorbic acid (10" mol dm') and solutions of xanthan gum (1%), mannitol (20%) and ascorbic acid (10' mol dm'). The viscosity of this solution falls from 300,000 cps to 250,000 (shear rate 0.07s4), after irradiation to 25 kGy. Therefore, whereas xanthan gum solutions containing readily depolymerized by irradiation, very high viscosity irradiated xanthan solutions containing thickening agents (LBG) and radiation protectors (mannitol - ascorbic acid) can be prepared. Solutions of CMC are also pseudoplastic. Irradiation to 25 kGy resulted in a decrease in the apparent viscosity of solutions of CMC/mannitol/ascorbic acid from — 180,000cps to 8,000cps, whereas for solutions of CMC alone and for CMC/mannitol solutions the viscosity was less than 500cps. This further illustrates the protective effect of ascorbic acid as was observed for xanthan solutions and also suggests that mannitol radicals cause depolymerization of CMC.

Thesis (M.Sc.)--York University, 2005. Graduate Programme in Biology. / Typescript. Includes bibliographical references (leaves 49-54). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url%5Fver=Z39.88-2004&res%5Fdat=xri:pqdiss &rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR11779

The distribution of a range of artificial radionuclides, derived from the authorised discharges of the Sellafield nuclear fuel reprocessing plant, have been determined in a core sampled from the intertidal sediments in the Esk Estuary. The plutonium-alpha activity profiles qualitatively resemble the Sellafield discharge histories for these isotopes, suggesting that the plutonium is largely immobile in the sediments. The beta-emitting 241Pu isotope activity profile was also determined for the sediments using the beta/alpha discriminator on a low-level liquid scintillation counter and qualitatively resembles the Sellafield discharge history. The 241Am activity profile represents the sum of americium both from Sellafield discharges and from the decay of its parent isotope 241Pu. The 244Cm activity profile was examined to see if its relationship to 241Am could be used as a marker of the Sellafield "discharge only" 241Am but this proved to be unsuitable. The 241Pu measurements were therefore used to calculate the amount of 241Am ingrowth and a deconvolved 241Am profile was estimated. The presence of the short-lived isotope 242Cm in the core can only be due to the precursor isotope, 242mAM, supporting its production. The first direct environmental sample measurements of the anthropogenic isotope of uranium, 236U, have been made using accelerator mass spectrometry. Coupled with 238U/235U atom ratios, and the known operational history of Sellafield, these data provide evidence that uranium has limited movement within the core. 237Np activity profiles in cores from west Cumbrian area are limited and the concentrations determined here are very similar to findings of other authors who have sampled close to this sampling site. The profile does not resemble the known Sellafield discharges suggesting that some redistribution of neptunium in the core is occurring. Finally, a quantitative model has been developed to examine the relationship between the Sellafield discharge histories and the sediment profiles, in terms of transport to the sampling site via an offshore mud patch which acts as a buffer. A prediction of the Sellafield discharge history for 236U, which is unknown, has been made, and the model has also been used to evaluate the potential mobility of the actinides that have been studied. A long-term prediction of the transfer of radionuclides to the intertidal sediments has also been made.

The development is described of a new ion source for atomic mass spectrometry which could lead to much wider applications of the technique. The source is based on an atmospheric pressure high temperature inductively coupled plasma. Samples are introduced to the plasma as aqueous solutions by a pneumatic nebulizer. Ion extraction from the plasma at temperatures up to 8000 K is based on sampling gas through an aperture placed in the tail flame. Initially apertures of 0.07 mm diameter were used which were protected from the full plasma temperature by the formation over them of a cooler boundary layer. High sensitivity and good resolution were obtained up to solute concentrations of 10 mug.ml-1, but matrix effects were severe. Conditions were then established in which ions could be sampled direct from the plasma core without passage through a boundary layer. Continuum flow through apertures up to 0.5 mm diameter enables plasma ion populations to be frozen rapidly in the supersonic expansion, before reactions can occur to disturb the composition. Much better matrix performance is obtained in this mode and sample concentrations up to 1000 mug.ml-1 can be introduced. Detection limits below 1 ng.ml-1 are obtained for a wide range of elements. Multi-element analysis is feasible at the rate of one sample per minute and isotope ratio determinations on solutions at about 30 mug.ml-1 are possible with precisions approaching 0.1% for integration times of 5 minutes. The performance of the system is discussed theoretically and reasonable agreement demonstrated with the experimental behaviour. The source already provides a viable analytical technique for samples introduced by any of the methods available for ICP-AES. These include solution nebulization, thermal evaporation, laser ablation and arc aerosol generation. Considerable scope exists for improving ion transport efficiency to provide sensitivity at least as high as any other routine analytical technique.

The main purpose of this work is to calculate the isotropic shielding of some nuclei, other than protons, of first- and second-row atoms in the periodic table and some transition metal elements in a wide variety of molecular environments, with a view to gaining an understanding of the various electronic factors which determine the observed nuclear shielding. Chapter One introduces some general concepts. Chapter Two presents a general servey of various Semi-empirical molecular orbital methods. Various MO calculations of nuclear shielding are briefly reviewed in Chapter Three with particular emphasis on Pople's GIAO-MO approach. This chapter also contains a description of the theory of medium effects on nuclear shieldings. Chapter Four is concerned with approximate MO theories and their application to the GIAO-MO method for Sum-Over-State (SOS) results of some shieldings of first-row elements. The medium effect models are used to explore the role of medium effects on nuclear shielding. This exploration is supplemented by performing some calculations on hydrogen-bonded models. Chapter Five records the SOS results for the nuclear shielding of some second-row elements in conjunction with the GIAO-MO method. The solvaton model is also used in an attempt to improve on our understanding of the relation between magnetic shielding and various features of molecular electronic structure. Chapter Six presents some shielding data for transition metal elements obtained by means of Pople's GIAO-MO method in conjunction with the INDO/5R parameterization scheme for SOS results of some inorganic molecules. A reasonable correlation between the calculated and experimental chemical shifts, compared by mean of a least-squares fit is obtained for some of the molecules considered.

Beta-induced fluorescence (BIF) is the luminescence excited from a compound as a result of the passage of beta-particle radiation through a compound or dilute solution of a compound. A liquid chromatographic detector, based on the principle of BIF, has been developed which allowed the detection and quantitation of fluorescent materials. A number of flow cells, incorporating ,a promethium-147 beta particle emitter, were designed and developed with the objective of attaining maximum sensitivity from the detection technique. The response of, the detector to eluted materials, the linearity of the detector response with sample loading and the sensitivity of the detector were examined in normal and reversed phase liquid chromatography. During the development of the BIF detector it became evident that the compounds detected need not be inherently fluorescent. The range of compounds detected could be increased to include those which quench the beta-induced fluorescent emission from the mobile phase. The technique of quenched beta-induced fluorescence was investigated as a detection technique and the response, linearity of response and sensitivity to eluted materials examined. Cerenkov photons are generated whenever a charged particle, travelling at a velocity greater than the velocity of light in the medium, passes through a transparent medium. Cerenkov photons are emitted from the medium as a continuum of wavelength range between 180 nm and 600 nm. The principle of absorption of Cerenkov photons was investigated as a detection technique in liquid chromatography. Strontium-90 was incorporated into a number of flow cells and the response, linearity of response and sensitivity of eluted materials, examined in normal and reversed phase liquid chromatography.