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Sarcocystis infections are common in domestic and wild animals. Pathogenic species are a cause of serious economic losses of livestock. In wild animals, infections with these parasites and their negative impact on wild populations are ill studied. The aim of this study is to determine the prevalence of Sarcocystis infections in gazelles kept at the King Khalid Research Centre (KKWRC), Saudi Arabia, and to establish the specific identity of the parasites causing these infections. This study was also designed to determine the definitive host(s) in which the sexual stages of the life cycle develop. Determining the definitive host of Sarcocystis species that infect gazelles may help in controlling the parasites. This study was also intended to examine the phylogenetic relationships between Sarcocystis parasites from different gazelle species, using modern techniques that involved the polymerase chain reaction (PCR) and sequencing the 18S rRNA gene. The prevalence of Sarcocystis infections in gazelles from Saudi Arabia was by macroscopic and microscopic (histological and peptic digestion) No macroscopic sarcocysts were found but Sarcocystis parasites were 66.7% of gazelles investigated by pepsin digestion and 39.9% using histological examination. Gazella dorcas showed the highest prevalence (83.9%) using the digestion technique, followed by Gazella subgutturosa marica (74.3%), Gazella thomsoni (55.6) and Gazella gazella (54.9%). The lowest prevalence was recorded from Gazella erlangeri (35.7%). A significantly higher prevalence rate was reported from from KKWRC main enclosure compared with those in the new breeding pens. Infection was significantly higher in adult gazelles compared with juveniles. The Arabian red fox (Vulpes vulpes arabica) was determined to be the definitive for Sarcocystis parasites in G. gazella and G. s. marica, through experimental Gazella gazella was also reported to act as an intermediate host for the cyst-forming coccidium, Hammondia heydorni and the Arabian red fox was found to act as a definitive host for the same parasite. The identity of Sarcocystis parasites detected in gazelles was determined using light and transmission electron microscopy. Microscopic characterisation showed five distinct species of Sarcocystis, which were subsequently described. However, sequence analysis of the 18S rDNA of Sarcocystis parasites reported from gazelles indicated that they were genetically identical in this region of the genome with the exception of that species derived from G. thomsoni. Sequence data also indicated that the group of Sarcocystis parasites detected from gazelles clustered with those species known to utilise canines as their definitive hosts.

Laser light scattering technique was used to measure the surface tension of liquid/vapor systems. It was also applied to measure the interfacial tension of low molecular weight chlorohydrocarbons/water interfaces, such as n-butyl chloride/water interface. The results were in good agreement with literature values. One of the powers of the technique; which is the ability to measure the dynamic surface tension; was applied for the first time to study the dynamic polymerization of vinyl chloride monomer (VCM) to form polyvinyl chloride (PVC) at 30°C. The interfacial tension of VCM/water surface was fond to decrease as the polymerization reaction proceeded. Dynamic light scattering was also applied to measure the surface tension of a polymeric surfactant (DAPRAL), as a function of concentration, temperature and time. It was discovered that the surface tension of this system to decrease exponentially with time, and that at steady state, the surface tension decreased as the concentration was increased. The critical micelle concentration at 25°C was found to be 0.007%. Finally the light scattering technique was applied for the first time to investigate the effect of the field of gravity on the surface tension of water. The experimental results were not conclusive to conclu de whether there is such a relation (even though the surface tension was slightly higher at -1g gravity compared to +1g gravity, but it was within the experimental error bars).

This work is directed towards linear and nonlinear three dimensional magnetostatic field analysis and computation in electrical devices. Question regarding the validity and uniqueness of numerical field solutions, obtained on the basis of the curl curl approach, has been resolved through analytical proofs, numerical demonstrations, as well as experimental verifications. A nonlinear three dimensional magnetostatic field formulation is developed using the Newton-Raphson approach in conjunction with the three dimensional finite element method for inclusion of nonlinearities in laminated iron cores under saturated conditions. The developed, formulation was successfully implemented and applied to a practical example with considerable magnetic saturation. A method, for the calculation of saturated device winding inductance, is presented. This method is based on an energy perturbation technique and was successfully applied numerically and verified experimentally. Two methods for the calculation of forces on conductor segments as well as magnetized ferrous parts are developed in conjunction with the three dimensional finite element vector potential method. The proximity effect, resulting from considering small or large solution volumes on the field distribution, and the calculated values of force, is examined. It is demonstrated that a large solution volume, with Dirichlet boundary conditions imposed on the outermost surfaces of the volume considered, yield practically the same result, as when the Neumman boundary conditions were imposed on such surfaces. This result is of a considerable significance, from a practical standpoint, since the imposition of Dirichlet type boundary conditions on the outermost boundaries of the volume considered, results in a fewer number of equations to be solved. This, in turn, results in savings of the total execution time and memory costs required for the solution of large problems of two dimensional, and three dimensional fields by finite elements. It is demonstrated that three dimensional field solutions reduce to the corresponding two dimensional field solutions for problems which are inherently two dimensional in nature due to axial symmetry. This result provides a further verification of the validity of the three dimensional finite element formulation presented in this work.