Sharif Digital Repository

Retinal detachment is a disorder of the eye in which a part or entire retina detaches from underlying layers. It is a medical emergency and if it is not treated, all vision may be lost. Surgery is the only way to treat retinal detachment. Pneumatic retinopexy (PR) is an office-based procedure for repairing some retinal detachment. PR has three cardinal steps: applying laser or cryopexy around all breaks to seal them, injection of gas into the vitreous cavity and appropriate head position so that the bubble closes the retinal breaks.
In this thesis, we are trying to model PR procedure and predict the behavior of intraocular gas. In general, once the gas is injected into the eye, because... 

To generalize the Najafi_Golestanian swimmer model from one dimension to two dimensions and to demonstrate its chemotaxis ability, here we introduce a model that consists of four spheres with same radius connected by three arms and we call it a star swimmer. Each arm can be in two states, contracted and expanded (initial length). So that at the head of each arm there are molecular motors that can act as enzymes and as a result of chemical interaction with specific activating substances in their environment, cause the entire body of the tiny swimmer to move and rotate. The change in the concentration of the activating substance in the environment breaks the symmetry of the preferred state of... 

This study used the emulsion liquid membrane method to investigate the extraction and separation of thorium from nitrate solution. According to the results obtained from the studies, Cyanex 272 was a suitable option for selectively extracting thorium. For simultaneous extraction and stripping of thorium from dilute aqueous solutions, an emulsion liquid membrane system consisting of Cyanex 272 as an extractant, Span 80 as a surfactant and sulfuric acid solution as a receiving phase (internal phase) was used. Emulsion liquid membrane method has high mass transfer flux due to high surface to volume ratio, which causes high extraction efficiency and fast transfer of thorium ions from its low... 

One of the novel methods of stabilization of nuclear waste is the use of vitrification technology. In order to stabilize high level wastes (HLLW) in glass, it is required that the elements are in their oxide form. Therefore, it is necessary to evaporate the waste and turn it into a solid form so that the elements can be converted into oxide form in the calcination furnace. Hence, one of the challenges of stabilization is the optimization of evaporation and calcination conditions. In this research, the parameters affecting evaporation were first investigated. Using laboratory measurements of application: temperature (110 to 180 °C), presence of nitric acid (0.5 to 4 mol/L), ratio of zirconium... 

One of the most common spinal surgeries involves spinal fusion or vertebral fixation, which is used to treat various conditions such as intervertebral disc disease, scoliosis (lateral deviation of the spinal column), fractures, infections, or the presence of tumors in the spinal column. In this surgical procedure, the use of pedicle screws and titanium rods prevents motion and friction between two vertebrae. Screws may enter the vertebrae in the wrong position and angle, causing bone weakening, rupture of nerve roots or blood vessels, weakness or lack of sensation in some parts of the body, spinal cord injury, and in severe cases, paralysis of the patient. For this reason, fusion surgery is... 

Pulp necrosis in immature teeth disrupts root development and predisposes roots to fracture as a consequence of their thin walls and open apices. Regenerative endodontics is a developing treatment modality whereby necrotic pulps are replaced with newly formed healthy pulp-like tissue. Many clinical studies have demonstrated the potential of this strategy to stimulate root maturation and apical root-end closure. However, clinical outcomes are patient-dependent and unpredictable. The development of predictable clinical protocols is achieved through the interplay of the three classical elements of tissue engineering, namely, stem cells, signaling molecules, and scaffolds. Scaffolds provide...