The formation constants for several metal ion-ligand complexes have been measured by glass electrode potentiometry in aqueous solution at 37°C using an ionic background of 150mM sodium perchlorate. The three topics comprising this thesis are (i) a study of the reaction of several metal ions, namely Co(II), Ni(II), Cu(II) and Zn(II), with ligands such as adeninate, cyclohexylamine and cyclopentylamine. These were studied in order to gain experience in the techniques of potentiometry and computation. (ii) The second topic, which comprises the major portion of the thesis, involved the in vitro study of zinc complexes with a series of ligands which can be divided into two groups; those containing only oxygen donor groups (acetate, galacturonate, hydroxybutyrate, malate, malonate, oxalate, salicylate and tartarate) and those which contain oxygen and nitrogen donor groups (glycinate, glycylglycinate and glycylglycylglycinate); the purpose of this investigation being to suggest the best zinc supplementing drug for treating zinc deficiency conditions. Hydroxybutyrate and galacturonate are suggested to be the most promising ligands for zinc absorption. (iii) Finally, computer simulation models of equilibria involving zinc and ligands in intestinal solution were used to correlate the rate of growth of turkey poults with the type of metal-ligand complexing occurring in intestinal fluid.

The origin of the extreme hydrogen deficiency observed in the R Coronae Borealis (RCrB) stars remains poorly understood. A likely mechanism for producing this deficiency is one whereby the original hydrogen envelope of the star is engulfed and destroyed in its interior. One of the few RCrB stars so far analysed, U Aquarii, in fact shows emphatic evidence of such an event having indeed occurred. This evidence takes the form of the large s-process enhancements observed in U Aquarii. Such enhancements are caused by the production of significant neutron fluxes which are directly produced by envelope engulfment giving rise to the ¹²C(p, γ) ¹³N(β⁺γ) ¹³C(α,n) ¹⁶O sequence of nuclear reactions. In order to obtain vital information regarding the nature of the envelope mixing event from observed s-process enhancements, detailed nucleosynthesis calculations investigating neutron production and s-process synthesis are carried out using a series of nuclear reaction networks and covering a wide range of parameter space. These calculations are mainly based on low-mass AGB and post-AGB stellar models since it is widely believed that the RCrB's are in some way related to this group of stars. It is shown how the ingestion rate of envelope material, the initial abundances and the type of mixing model used have a large influence on the neutron and s-process production. New spectral observations of U Aquarii are presented, and it is shown how these new observations allow a new interpretation of the mixing event which occurred in this star and how further improved abundance data of the star will lead to an unambiguous determination of the nature of the mixing event. The RCrB stars are also thought to be related to the extreme helium stars. Discovery of variability in two of these latter stars is presented.

Commercially important superabsorbent polymers are crosslinked polymers of partially neutralised acrylic acid which can typically absorb and retain up to a hundred times their own weight in water. Superabsorbent polymers are most widely used in the personal hygiene industry where they are found in the core of disposable nappies, external feminine sanitary products and adult incontinence pads as absorbents for bodily fluids. Many other applications have been found through their amazing absorptive properties including artificial snow, artificial muscles and the prevention of water leakage into underground transmission cables. Superabsorbent polymers have many important industrial uses although little investigation into their structure and mechanisms has been done to date. As a result of superabsorbent polymers being totally insoluble in all NMR solvents solid state 13C CP/MAS NMR was used to investigate various structural aspects of the polymer in both dry and hydrated states. The NMR work carried out on the structure of the superabsorbent polymers suggests differences in structure between polymers neutralised before and after polymerisation takes place. It also suggests different tacticity within the polymer, seen as the polymer becomes more hydrated. 23Na relaxational studies have given an insight into the change in the sodium ion environment as the polymer becomes more hydrated. The effect of increasing neutralisation of the polymer was also investigated. Nuclear Magnetic resonance imaging was also used to try and investigate the mechanism of absorption of liquid by the polymer. From the images produced it was seen that the liquid is not absorbed homogeneously throughout the polymer sample and a more intense region is seen at the front of the image suggesting a solvent front. Commercial superabsorbent polymers are usually coated to enhance their absorptive properties. Experiments were carried out using a sodium ion-selective electrode to try and determine whether or not this coating provided the polymer with an osmotic ion-exclusion membrane. The sodium ion-selective electrode allowed differences in [Na+] before and after the addition of polymer to a solution of NaCl to be detected, and consequently allowed the presence of an osmotic ion-exclusion membrane to be determined.

The effects of colchicine and IAA on roots of Vicia faba L. have been examined; changes were found mitotic index, polarity and differentiation. The following conclusions were reached: 1) IAA suppresses or delays some process(es) in the G2. S and probably also the G1 stages of interphase. IAA has no effect on mitosis, but because of its effects on interphase, causes a decrease in the MI. IAA does not appear to be a factor involved in spindle formation, and the time at which spindles reappear after colchicine treatment is not influenced by IAA. Colchicine blocks the anaphase separation of the chromatids. This is not due to a change in pH and it does not involve IAA. Because colchicine blocks the anaphase separation of the chromatids, restitution takes place and polyploid cells are seen in division one mitotic cycle later. The duration of metaphase is apparently increased after colchicine treatment. A result of colchicine induced metaphase delay is that the relative duration of metaphase is lengthened and a change occurs in the prophase: metaphase ratio in favour of metaphases, compared with the control values. This change in the prophase: metaphase ratio is reversed by IAA, many hours after treatment, to produce prophase: metaphase ratios similar to those of the control roots. IAA has this effect for at least two reasons; the relative duration of metaphase is shortened from the value found after treatment with colchicine, to a value similar to that of the controls and, the percentage of polyploid metaphases found after colchicine treatment is lowered by treatments with both IAA and colchicine. 4) Following colchicine treatment, changes occur in the MI; there is a significant increase 24 hours after treatment but after a further threa days the MI is less than 1. 5) Polarity of root growth is initially determined by the plane of cell division. In more basal regions of the root, it is determined by both the plane of cell division and that of cell expansion. Finally, it is determined by the plane of cell expansion along. 6) IAA induces lateral root primordia formation, but these fail to develop normally, however, unlike the primordia that appear in the apical 10 mm of roots treated with colchicine and which 'gram out as lateral roots. 7) The polarity of cell division is re-established in colchicine treated roots as soon as normal mitosis reappears. Thus, one aspect of root polarity returns to normal several days before cell elongation recommences. IAA does not affect the polarity of cell elongation or division in the concentration used. 8) The cessation of root growth after colchicine treatment is not due to the cessation of cell division, but to the altered polarity of cell division. 9) Differentiation of xylem vessel elements occurs closer to the apex in colchicine treated roots than in the controls. IAA does not prevent this differentiation. In roots treated only with IAA xylem elements are seen closer to the apex compared with the control roots. 10) All of the primordia that develop after colchicine or colchicine and IAA treatments do so, at least partly, from cells affected by the colchicine. This is also true of the new meristem which forms, after these treatments, in the root apex. The new apical meristem forms partly from the cells of the meristem which was present at the time of treatment and partly from the cells of the quiescent centre. 11) IAA does not induce polyploidy, nor does it induce polyploid cells present at the time of treatment to divide. 12) The response of roots to IAA treatment, with respect to MI, depends on the age of the root at the time of treatment.

Measurements of drag forces an spheres end a cylinder in open rectangular channels in liquid helium II heat flow and superflow wore mode at temperatures between 1.3°K and the λ-point. The drag forces were measured by the deflection of a torsion system suspended above the free surface of the liquid from a quarts fibre. In the heat flow experiments, the drag vas found to be similar to that which would be exerted by a classical fluid with the same velocity, viscosity and density as the norma1 component. Correlations of the drag coefficient D/( 1⁄2 ρ[sub]n2A) with the Reynolds numbers ρnvηd/ηn and ρvnd/ηn show that the former is much more suitable both in tor of eliminating temperature dependence and agreement with the classical value. Above 1.6°K, a small decrease in drag with increasing velocity was usually noticed; this was attributed to the onset of turbulence in the superfluid, giving rise to a component of drag in the direction of superfluid flow. Describing the turbulent superfluid so a laminarly flowing fluid with an effective viscosity ηs makes possible an ardor of magnitude estimate of ηs the decrease in drag; it is found to lie between 10 and 100 micropoise. At temperatures nearer the λ -point, the simple two fluid description appears to become lies adequate. In the superflow experiments, sphere an the cylinder arc dragged in the direction of the superfluid flow. Correlations of drag coefficient with Reynolds number suggest value for the effective viscosity of between 20 and 100 micropoise. In the cylinder superflow experiments, below a velocity of 2±1 am sec−1, no drag was observable. This is attributed to an ideal flow regime and is bellowed to be the first direct demonstration of D'Alembert's wades, rely that an inviscid fluid can exert no drag on a body.

1. A review of the literature on cartilage canals is given. 2. The formation of cartilage canals commences when the cartilage mass exceeds the maximum thickness which can be nourished by diffusion of fluid from the surface. This maximum thickness or the critical size at which canalization would occur, has been worked out in the distal femoral epiphysis at various developmental stages. It varies with the age of the foetus 0.25 mm. at the fourth month and gradually increasing to about 0.6 mm. at full-term. 3. Because of the restricted area of origin of the cartilaginous epiphysis of long bones, the canals seldom found, to be arranged in a radial fashion to the whole epiphysis, but they arranged so as to distribute the blood evenly through the whole mass. 4. (i) The clear, well-formed communicating canals have been seen in the epiphysis of human long bone as early as the fourth month of foetal life. (ii) As development proceeds, some of the communicating canals appear to become obliterated in, the region of proliferating cartilage adjacent to the metaphysis: this obliteration of canals occurs more rapidly after the onset of epiphyseal ossification so that by the time ossification of the epiphysis is complete, no communications between the diaphysis and the epiphysis remain. (iii) It is suggested that probably the primary cause of the formation of the communicating canal is the chemio-taxio influence in the zone of actively growing cartilage in the region adjacent to metaphysis, which directs the ends of the canals arising from the perichondrium near the end of the shaft to bend towards the diaphyseal end. (iii) The probable function of the communicating canals is that they assist in the supply of nutrition to and in the removal of waste products from the cells in the active juxta-metaphyseal cartilage. The almost invariable absence of osteogenic elements in these canals given no support to the hypothesis that they take part in the formation of the centre of epiphyseal ossification. (v) The vascular connective tissue buds which are identical with the communicating canals in the epiphysis of long bone, have boon observed in the cartilaginous sternal end of the clavicle of a human foetus. 5. It is suggested that the cartilage canals grow by a combination of three methods that is by surface accretion, stretching due to interstitial growth and active invasion of the cartilage by the tip of the canal. 6. The cartilage canal connective tissue contents are of perichondrial origin, and are not formed by back differentiation of the cartilage to an embryonic type of connective tissue. 7. In the long bone of the human, the cartilage canals are probably responsible for the formation of the epiphyseal ossification centre.

No description available.

Twelve heterocyclic ring compounds have been prepared and a high resolution Nuclear Magnetic Resonance study of each carried out. In particular, solvent effects and coupling constants have been studied. Some axial and equatorial shifts of methylene protons were found to be reversed compared to the predicted situation, Observed coupling constants have been found to be slightly solvent dependent. Some interesting values of coupling constants prompted a full X-ray crystal analysis of two of the compounds. This has been done, yielding bond lengths, bond angles, configuration around the phosphorus atom and conformation of the heterocyclic ring, all in the solid state. Dihedral angles for P-O-C-H systems have been calculated and an attempt has been made to correlate observed coupling constants with dihedral angles and electronegativity of substituents.

It is not clear whether flood-tolerant plants survive in waterlogged soils because they maintain aerobic activity in all regions of the roots, or whether biochemical adaptations to anoxia are involved. Many plants have some capacity for internal ventilation, and so in order to exclude oxygen from the root environment it is necessary to subject both the roots and the shoots to anoxia. Pea and rice seedlings were exposed to anoxia for 1 to 24 h and their tolerances and survival compared. With pea and rice, cv. Oeiras, tolerance of anoxia decreased as the temperature increased, although rice was more tolerant than pea at a given temperature. Increasing amounts of K+ were lost from the roots of whole seedlings during anoxia, and seedling recovery on return to air was associated with the seedlings' ability to reabsorb most of the leaked K+. Aerobic respiration in the root tips was associated with both K+ uptake by pea seedlings, and the recovery and subsequent growth of pea and three varieties of rice after anoxia. All rice varieties were more tolerant of anoxia at 25°C than was pea at 20°C, but differences between the tolerance limits of the rice varieties were apparent. Although some pea and rice seedlings appeared undamaged after anoxia, the subsequent growth rates of pea and rice, cv. IR8, were seriously impaired. Ethanol accumulated around the roots of all seedlings during anoxia, but there was no correlation between the quantity of ethanol produced and the different tolerance limits of the seedlings. Pea seedlings that were prevented from transpiring during anoxia were damaged earlier than controls, possibly because of an increase in the rate of accumulation of a toxic product of anaerobic metabolism in these seedlings. Two percent glucose merely delayed, and did not prevent, the onset of damage in whole pea seedlings during anoxia, nor did it enhance the subsequent growth of the seedlings. Under these conditions, the accumulation of endogenous ethanol to a toxic concentration was considered to have been the more likely cause of seedling death. From the results presented in this thesis and elsewhere, it is concluded that-the immediate cause of seedling death during anoxia is a shortage of substrate for glycolysis, and that the additional effect of ethanol accumulation in some species may reduce their subsequent rate of recovery.

The variation of the viscosity of aqueous and non-aqueous electrolyte solutions with salt concentration has been studied and the results interpreted in terms of a number of mathematical models. The effects of ion-association on the viscosity of electrolyte solutions has been investigated by measuring the viscosity of aqueous solutions of some thallous salts. The viscosities of alkali halide salts in formamide have been determined over a range of temperatures and new methods for the division of viscosity B-coefficients into ionic contributions have been proposed. The results of these studies have been interpreted in terms of the ion-solvent interactions. The intermolecular interactions present in binary liquid mixtures of formamide with methanol, ethanol propan-l-ol and butan-l-ol have been studied by viscosity measurements over the complete concentration range. Finally the usefulness of time domain dielectric spectroscopy in solute-solvent interaction studies has been briefly investigated.