In this study, pulsed field gel electrophoresis (PFGE) was used for genomic DNA finger printings of methicillin-resistant Staphylococcus aureus (MRSA) isolates. Thirty strains of S. aureus collected from major hospital laboratories and public health centers, Riyadh, King Saudi Arabia were tested phenotypically by conventional methods and genotypically by multiplex-PCR for direct detection of S. aureus 16S rRNA and mecA genes. The chromosomal DNA of the isolates was examined by using pulsed-field gel electrophoresis (PFGE) using SmaI. SmaI cut the chromosomal DNA of the examined MRSA into 9 to 13 fragments, moreover, 16 chromosomal digestion patterns were observed out of the 30 examined isolates. The first pulsed field gel electrophoresis (PFGE1) contains 9 strains recovered from soft tissue infections and surgical wound infections. The second one (PFGE 2) contains 4 MRSA isolates, 3 of which were recovered from skin and soft tissue infections, while one was recovered from wound infection. Moreover, there are 3 chromosomal digestion patterns (PFGE 3, 4 and 5), each pattern involved two strains of MRSA which were recovered from surgical wound infections. A dendrogram of percent similarity, revealed three major clusters, the first cluster containing four groups (17 strains). The second cluster contains one group (12 strains), while the third cluster contains only one strain recovered from deep abscess.

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Osteoporosis is a common disease affecting a large proportion of the human population worldwide. It is described as a bone density and structure deterioration leading to a bone fracture risk. The World Health Organisation (WHO) recognises osteoporosis as one of the most health issue since it is asymptomatic. Globally, two third of women and one third of men over 50 years is diagnosed with osteoporosis.One million in Australia alone have osteoporosis and over six million is considered with low bone mass which cost the budget healthcare sector about 2.75 $ billion dollars a year. The expectation rate of population affected by osteoporosis is assumed to significantly increase with continuous increase of aging population. Therefore, an urgent powerful and precise technique for early detection of bone loss is required.There are several techniques in the market available but the Dual Energy Absorptiometry (DXA) is the only one authorised for this regard by the WHO.However, the controversy is that DXA can only measure the bone density but not yet the bone microarchitecture which is an important factor for the assessment of bone.Quantitative ultrasound (QUS), in terms of broadband ultrasound attenuation (BUA) and speed of sound (SOS), is an alternative method that has been investigated by numerous studies confirming that it is a reliable technique for the assessment of bone and predicting fracture risk. Yet, sufficient knowledge about the propagation of ultrasound waves through complex structure such as cancellous bone is not attained which affects the ability of accurate determination of bone mass and structure.A new proposed hypothesis is that phase interference is the leading attenuation mechanism in complex composite such as cancellous bone due to inhomogeneity transit time of the sonic rays. It also proposed that the propagation of ultrasound wave can be approximated as parallel sonic rays; each has a transit time determined by the proportion of bone (solid) and marrow (liquid) it travels through. Thus, a transit time spectrum (TTS) can be defined describing the proportion of sonic rays of the same transit times. Therefore, this thesis will illustrate a development and validation of an ultrasound transit time model of complex structure such as cancellous bone and identify its relation with phase interference. This study will further explore possible ULTRASOUND TRANSIT TIME SPECTROSCOPY IN COMPLEX MEDIA -APPLICATIONS AND RELATIONSHIP WITH PHASE INTERFERENCE IV applications of the TTS to enhance the effectiveness of ultrasound as a reliable assessment tool for bone.In particular, an examination of the phase interference, created by the variation in transit time, being the main attenuation factor in complex structure among other factors for instance absorption and structure-scattering was performed. Amore fundamental concept of phase interference was investigated showing that it has both temporal and spatial phase interference. The temporal phase interference depends on the pulse length and the transit time di...

Technical and practical hurdles were behind the limitation of drilling extended reach wells. These include, pipe torque and drag, fluid circulation control, and directional control of drilling such wells. From practical point, horizontal and extended-reach wells are proved to have a finite-conductivity wellbores, which means that there will be a flow capacity limitation when reaching certain length of wellbore. That implies that the flow optimization consideration may limit the drilling requirement to the effective wellbore length. To maximize the extension of drilling, whilst unleashing the limitation of wellbore finite conductivity, a U-shaped horizontal well design is investigated in this study. The U-shaped well architecture is new but was not studied from the flow capacity drivers, was hence was not considered as a solution for optimizing the flow in extended reach wells. This is to unleash restriction imposed by the finite conductivity of the wellbore and hence maximize flow capacity and sweep efficiency. A semi-analytical model was developed to validate results from pressure transient analysis and wellbore flow simulation. The model was validated with data in literature for a single horizontal well. The flow simulation of the connected wells showed a big increase in flow capacity. In addition, the new well architecture can be utilized to optimize flow by altering the flow rate from both ends. This solution can be used as a solution to avoid the used of downhole chokes to restrict flow. In addition, it can be used to optimize sweep efficiency as extended reach wells cross long section in the formation.

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