Sharif Digital Repository

Due to compability of Magnesium with the body, it is a suitable material for making biodegradable stents, Althogh, its mechanical properties are not desirable for stent application. Accordingly, lately, magnesium’s microstructure and mechanical properties have been improved using various methods, including the process of severe plastic deformation (SPD). Many severe plastic deformation methods have been introduced for the fabrication of ultrafine grain tubes till now, which the process of tubular channel angular pressing (TCAP) is the most effective one. In the first part of the research, Magnesium tubes with a thickness of 1 mm were processed using the TCAP with a trapezoidal channel, and... 

According to Penrose-Hameroff's theory, Consciousness as an undeniable reality can, in some cases, be explained by a kind of orchestrated objective reduction of the wave function in the cytoskeleton of the brain neurons. Here, I have presented the subject, problem, and claim of this theory, as well as its argument, which consists of three main premises. In the first premise, first by rejecting the opposing theories and then by presenting reasons, it is shown that human thinking is, in some manner, sound but non-computable, and at the same time, accepting the Non-computability of human thinking requires believing in the objects in the universe that are non-computable, but They can be... 

Properties of stents are significantly dependent on the mechanical properties of the microtubes used in their construction. Therefore, investigating the influence of various factors on the mechanical behavior of magnesium microtubes employed in the fabrication of biodegradable stents can play an indispensable role in the development of the emerging industry of biodegradable stent manufacturing. In this dissertation, the effects of different parameters on the mechanical behavior of magnesium microtubes used in the construction of biodegradable stents have been examined. To achieve this, the objectives of this dissertation have been divided into three main sections. In the first section, a... 

Magnesium and its alloys have attracted significant attention in the field of medical applications, particularly biodegradable stents. However, due to inherent limitations such as weak mechanical properties and high corrosion rates, they have not been widely used. Alloy X0 has emerged as a suitable substitute for magnesium alloys with rare earth elements due to its corrosion resistance and cost-effectiveness in biomedical materials. In this study, the direct extrusion method was used to produce microtubes with suitable mechanical properties from microalloy X0 magnesium. At first step, hot compression tests were condueted on the homogenized microalloy X0 at four temperatures of 250, 300, 350,...