This thesis is 'concerned with aspects of dynamic compaction of pharmaceutical powders. The research is mainly aimed at the influence of compression rates on the residual resilience and strength of the tablet. A wide range of compression strain rates (103 - 10 per sec. ) is covered for di-pac-sugar, sodium chloride, potassium bromide, paracetamol, copper sulphate, avicel, lactose and calcium phosphate. The influence of compression rate on the form of the pressure-density relationship including the IHeckel and 1: awakita diagrams is investigated. Theoretical and experimental work are conducted on the relationship between radial and axial pressures during uniaxial straining. The general tendency for all the powders tested except for the paracetamol d. c., is to exhibit increased compaction pressure with strain rate up to 105 per sec. Due to morphological and compositional factors paracetamol d. c. softens with the rate of straining up to about 102 per sec. At higher rates it behaves like other powders. Generally, at high strain rates, the brittle behaviour dominates the process and tablet capping becomes more evident. The scope, origin and the main objectives of the present work are presented in Chapter 1. A brief historical account of the development of uniaxial compression techniques is given in'Chapter 2. Past work in the field of uniaxial compaction is reviewed and. classified. Various dynamic processes are classified according to the rates of compaction. Discussion of the various mechanisms responsible for, and governing, the way in which a powder consolidates when subjected to uniaxial compaction is presented together with a brief discussion of the capping phenomenon. Chapter 3 describes the construction and operation of a specially designed die incorporating a pressure pin for radial pressure measurement. The effect of compression rate on the form of the characteristic compaction curves, for all powders, is investigated using the above die on a servohydratlic variable speed machine (ICI simulator) at constant compression rate conditions (10-110 per sec). Investigations, using this apparatus indicate that all materials tested exhibit strain rate sensitivity to varying degrees (i. e. increased resistance to compaction as the speed is increased). In Chapter 4a brief review and discussion of viscoelastic aspects and theoretical modelling of the compaction process are presented. By plotting axial versus radial pressures during successive compression and decompression cycles at various speeds and by observing the decay of both pressures under constant volume conditions, it is possible toi draw certain conclusions about the relative elastic-plastic behaviour of each material. Investigations ' indicate that the use of linear viscoelastic theory could be useful in predicting the general trend of the process but insufficient to model the response of the various powders to the different loading conditions. Accurate modelling would require more experimental work and analysis of a high level. Also, the elastic recovery of all the compacts within the die is found to range from 8-120. Chapter 5 describes various aspects of forming and testing of tablets on an Instron machine at constant speed. Crack initiation, propagation and modes of failure during the Brazilian test are investigated by employing -high speed photography. An analysis of the effect of die and punch rigidity on the Kawakita relationship is attempted. An account of 'the variation of the. ejection pressure and the residual tensile strength with the maximum applied pressure is given. in this-chapter, the effect of ageing time and the effect of the ejection speed, for both straight and tapered dies, are also examined. Investigations indicate that, during the Brazilian test, in all compacts for all materials, the crack starts at the centre of the tablet and propogate up and down towards the plattens. Three main types (modes) of failure are observed: The 'traditional' mode of failure, in compacts of elastic-plastic deforming materials , (such like di-pac-sugar, paracetamol); The (random) mode of failure in plastically deforming compacts (such like sodium chloride potassium bromide), End capping which is observed in almost all materials compacted at high speeds. The values of the constant "b" (in the Kawakita Equation) is significantly influenced by the die and punch materials while the constant "a" remains unchanged. Also, the ejection pressure is increased with the increased axial maximum pressure and decreases with increasing speeds of compaction. All materials tested, show slight increase in the compact tensile strength as the. ageing time is increased - Also all compacts formed in the tapered die show higher tensile strength than those formed in the straight die over the range of ejection speed tested. Chapter 6 describes the construction and operation of an apparatus used for quasistatic"and medium rate (10 2_ 103 per sec) uniaxial compaction of powders. This apparatus allows the powder volume, 'axial and radial compaction pressures to be measured simultaneously. The investigations indicate that the properties of the resulting compacts are influenced by the compaction rate employed. Also, the compact tensile strength at this range is found to decrease together with the capping pressures. Chapter 7 describes the construction and operation of especially designed high pressure air projectile launcher compaction apparatus suitable for high rate uniaxial compaction of powders. Both, the axial pressure and powder volume can be measured on this apparatus. Problems of stress wave reflections in the system are overcome by using long load cells which enable accurate measurements to be obtained. Almost in all compacts, formed on this apparatus, ' end capping is observed. Chapter 8 gives a detailed description of the design, construction and operation of a high pressure triaxial cell working at pressures of up to 207 MPa, together with the associated equipment. Also, the sample preparation procedure is established. Preliminary, tests carried out on di-pac-sugar, lactose and paracetamol d. c. indicate that the powder characteristics can be designed by controlling the axial-and radial stresses. Chapter 9 describes the theory, equipment and the experimental results of a new technique based on the Split Hopkinson Bar principle to determine 'tension and compression Young's moduli of'a. tablet. The investigation indicates that the modulus in compression is higher than that in tension (in some cases by almost 20t). Finally, chapter 10 outlines general conclusions and suggestions for further work.

The pyrrolo[2,1-c][1,4]benzodiazepines (PBDs) are a diverse group of antitumour antibiotics in which there has been growing interest over the past 30 years. These compounds bind covalently within the minor groove of DNA via the formation of an aminal bond between the N10-C11 imine functionality of the PBD and the exocyclic C2-NH2 of a guanine base, resulting in the inhibition of processes including DNA replication and transcription, thus leading to cell death. PBD `dimers' have the ability to form irreversible interstrand cross-links with DNA. One example, DSB-120, has been shown to recognise six base pairs compared to the monomer DC-81 that recognises only three. A second example, SJG-136, has unsaturation at the C2 position and is cytotoxic at the picomolar level in glutathione-rich cell lines resistant to a number of agents including DSB-120. The major part of this project concerns the synthesis of novel PBD dimers specifically designed to investigate the effect of sp1 hybridisation at the C2 position of the molecule. One problem has been that only small amounts of PBD dimers were previously available through the original synthetic routes. Through this project, three new synthetic methodologies have been devised to produce two novel PBD dimers KEC-570 and KEC-5130, as well as the known PBD dimers SJG-136 and DSB-120. These syntheses utilise novel cyclisation procedures that involve fewer steps than existing synthetic methods and afford cleaner products in higher yields and on a larger scale. This has allowed, for the first time, a full pharmacological evaluation of these molecules. KEC-570 has been shown to form interstrand DNA cross-links and to be cytotoxic in three human carcinoma cell lines. Presently, both KEC-570 and DSB-120 are being evaluated across the standard panel of tumour cell lines at the National Cancer Institute. SJG-136 has proved successful in the NCI's Hollow Fibre assay and has progressed to in vivo xenograft assays at the NCI.

No description available.

The work presented in this thesis is involves two distinct topics. The first area is the main theme of the thesis, and is an investigation of the contribution made by the gain to the temperature sensitivity of long wavelength semiconductor lasers. The second topic is in a separate but related area and consists of an experimental determination of the valence band deformation potential, b, whose magnitude is found to be in good agreement with theoretical prediction. The thesis first presents an overview of the equipment used in the measurements, followed by a review of the available methods for making gain measurements on semiconductor lasers. It is concluded that the Hakki-Paoli method, in conjunction with the Cassidy method, provides the most suitable technique, but the measurement system must be very carefully set up to ensure valid results. The gain-current relationship is then measured in three quantum well lasers with 1.55μm tensile, compressive and unstrained active region respectively, and in two 1.3μm devices, with tensile and compressive quantum wells. It has been observed experimentally that the modal gain, G, varies linearly with the log of the drive current, I, in many quantum well lasers. This relationship was expressed by McIlroy as G= Go in011/0 ). It has been suggested that the strong temperature sensitivity of the threshold current in long wavelength lasers is due to strong temperature dependence of the gain characteristics. We show that the Go parameter is virtually independent of temperature in the 1.5μm devices studied, close to that expected for an ideal laser, while the 1.3μm lasers depart from the ideal case to some degree. The 1.54m devices all have a characteristic temperature, To, of = 70K, in good agreement with what would be expected if non-radiative phonon assisted Auger recombination, with an activation energy of 25meV, dominates the current. The lower To values in the 1.3μm devices of 42K and 50K respectively are consistent with an additional temperature dependence of the differential gain above that predicted in an ideal laser. In both cases it is concluded that Auger recombination makes the dominant contribution to the temperature sensitivity. In the second topic considered, photo voltage measurements are used to determine the energy splitting of the light hole and heavy hole valence subbands in a set of tensilestrained lasers. Using these measurements it is shown that a theoretical model, using the interpolated strain deformation potential determined by Krijn, gives good agreement with experiment.

This study reviews the upgrading of forestry training in Indonesia comprising public, private and local people. The principal aim of this study is to investigate if, and how, forestry training can meet the needs of Indonesia forestry sector as methods of sustainable forest management are developed. Sustainability of forest resources and its underpinning by human resource development systems and processes are currently the primary issues and serious challenges for Indonesia forestry sector. The current capacity of forestry training in Indonesia is considered inadequate to meet the challenge. Forestry training managers and trainers in both public and private sectors, timber company managers and workers, and local people were involved in the human resource development processes to meet the new requirements and to see through the remaining traditional forestry training at the same time. Consideration was given to the weakness of the capacity of the current forestry training and the needs for improvement. The literature review took a theme approach covering the fields of human resource development processes, training and development, the six Indonesia five - year development plans, the guidelines for sustainable forest management of Indonesia and the International Tropical Timber Organisation. The main focus for obtaining data with respect to the respondents and informants was the changes brought about by training. The methodology centred on the design and use of a questionnaire with return rate of 55% from eighty managers of forest concessions, 80% from ten heads of public forestry training centres and 60% from eight private forestry training centres. In addition, a formal interview was conducted with HPH managers, APHI representatives, Forestry officials, local government, and trainers. Semi - structured interviews were conducted with villagers and HPH workers. Observations were conducted of villages within KPHP pilots in Riau, Jambi, Central Kalimantan, and East Kalimantan concerned with Forest Village Development. Teaching sessions of trainers graduated from OTTA at the Wolverhampton University were also observed. These data formed the basis of an analysis of the gap between the ideal future forestry human resource capacity and the current provision in relation to sustainable forest management. Analyses of quantitative data were conducted based on descriptive statistics using Excel. The approach to qualitative data was from open to axial and selective coding. In this study the limitation of upgrading forestry training emerged. This limitation is also endorsed by the users of the training programmes. The forestry extension activities are seen as an integral part of human resource development processes and as such must be with the respect to the forestry training programmes. The sustainable forest management can be justifiably incorporated within the upgrading forestry training. The only high standard of forestry training that can assure a success of forestry development is by providing welltrained foresters. Training has to become a strategic preoccupation of senior executives and top trainers as agent of change, which induces positive work attitudes, commitment, discipline and professionalism.

No description available.

No description available.

No description available.

No description available.

No description available.