Saudi Cultural Missions Theses & Dissertations
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Item Restricted The Effect of Dietary Interventions on Arterial Stiffness in Men. A Systematic review of the literature(University of Nottingham, 2024) Almutairi, Mohammed; Rocha, LuciaAbstract Background and introduction Cardiovascular diseases (CVDs) are the leading cause of death globally, encompassing conditions like coronary heart disease and strokes. Risk factors include hypertension, diabetes, and lifestyle choices such as smoking. Arterial stiffness is a crucial risk factor in hypertension, refers to the reduced flexibility of the arterial walls. This condition arises as blood vessels age and is associated with various cardiovascular diseases. Studies have shown that dietary interventions can significantly reduce CVD risks by improving factors like blood pressure and arterial stiffness, particularly in men. This paper is to systematically review the current literature on the effects of different dietary interventions on arterial stiffness in men Methodology This systematic review adheres to PRISMA guidelines, employing a flow diagram to outline the article selection process, focusing on adult males at risk for cardiovascular diseases. It assesses the impact of dietary interventions on arterial stiffness, measured by carotid-femoral pulse wave velocity (PWV). The review specifically includes randomized controlled trials (RCTs) published from January 2015 to June 2024 that are in English and utilize PWV for measuring arterial stiffness. Excluded are non-RCT studies, those combining diet with exercise, and those involving females, children, or mixed groups. Primary outcomes are changes in PWV, while secondary outcomes include variations in systolic blood pressure, heart rate, and triglycerides. Results The systematic review process identified five randomized controlled trials (RCTs) met the inclusion criteria out of an initial 1,131 papers after rigorous screening. Only one study using cocoa flavanol intervention achieved significant reduction on the pulse wave velocity, the same study also showed significant decrease in systolic blood pressure, also another study showed significant reduction in systolic blood pressure after consumption of high fat beef patties. Conclusion This review indicated that cocoa flavanols can significantly improve arterial stiffness and systolic blood pressure, but other dietary interventions lacked similar impactful results. The findings suggest that effective strategies might need to integrate diet with exercise and other lifestyle changes to significantly enhance cardiovascular health.12 0Item Restricted SELF-HEALING MECHANISM IN POLYMER COMPOSITE MATERIALS(2023-07-04) Almutairi, Mohammed; Khan, MuhammadThe current self-healing mechanisms are still a long way from being fully implemented, and most published studies have only shown successful damage repair at the laboratory level. The complex nature of these mechanisms makes it difficult to implement them in real-life situations where the component or structure must continue to function. For complete healing, a molecular-level chemical reaction is required with the aid of external stimuli such as heating, light, and temperature change. Existing self-healing mechanisms are almost impossible to implement in critical applications such as 3D-printed products due to the requirements of external stimulations and reactions. The objective of this research is to investigate the strain release behaviour during crack growth of polymeric beams under elastic loads for self-healing. The mechanical behaviour of polymer components has been studied for many years, and their basic features are well understood. In this study, the elastic and plastic responses of 3D-printed beams made of Acrylonitrile butadiene styrene (ABS), thermoplastic polyurethane (TPU), and thermoplastic elastomers (TPE) were investigated under different bending loads. Two types of 3D-printed beams were designed to test their elastic and plastic responses under different bending loads. These responses were used to develop an innovative self-healing mechanism based on origami capsules that can be triggered by crack propagation due to strain release in a structure. The origami capsules, made of TPU in the form of a cross with four small beams either folded or elastically deformed, were embedded in a simple ABS beam. When crack propagation occurred in the ABS beam, the strain was released, causing the TPU capsule to unfold with the arms of the cross in the direction of the crack path. This increased the crack resistance of the ABS beam, which was validated in a delamination test of a double cantilever specimen under quasi-static load conditions. The results showed the potential of the proposed self-healing mechanism as a novel contribution to existing practises primarily based on external healing agents. The self-healing mechanism of TPU and TPE origami capsules has been demonstrated and reported for the first time. These materials achieved a good balance of mechanical strength and self-healing ability. A thicker beam structure tends to yield higher strain energy than do low thickness values for the beam. Since the strain energy release is dependent on how much cracking has propagated, so the higher strain release from the DCB TPU star and roll contributes to the rate at which crack propagation extends.44 0